Advanced Vertical Robotics Drone Documents

• 1: AVR Drone Kit Contents
• 2: 3D Printing
• 2.1: Landing Gear
• 2.2: Mounts
• 2.3: Gimbal
• 3: AVR Drone CAD Model
• 4: Basic Drone Assembly
• 4.1: ESC Mounting
• 4.2: Mid Plate Assembly
• 4.3: Motors and Arms
• 4.4: FC to ESC Wiring
• 4.5: FC Mounting
• 4.6: Bottom Accessory Plate
• 4.7: Landing Gear
• 4.8: Prop Guard Assembly
• 5: Battery Management
• 5.1: Overview
• 5.2: Charging
• 5.3: Storage
• 6: RC Transmitter Setup
• 6.1: Basic Usage
• 6.2: Binding the RC Receiver
• 6.3: Setting the Output Mode
• 6.4: Setting Up Channels on the RC Transmitter
• 6.5: Setting Up Failsafe
• 7: Flight Controller Setup and Calibration w/ QGC
• 7.1: PX4 Firmware
• 7.2: Airframe
• 7.3: Sensors
• 7.4: Radio
• 7.5: Flight Modes, Arming, and Kill Switch
• 7.6: Power
• 7.7: Safety
• 7.8: Motor Test
• 8: Checkpoint 1: Initial Flight Test
• 8.1: Before You Fly
• 8.2: Flight Test
• 8.3: After You Fly
• 9: Peripheral Control Computer (PCC)
• 9.1: Physical Assembly
• 9.2: Flash the PCC
• 9.3: Test the PCC
• 10: Vehicle Management Computer (VMC)
• 10.1: Preparing the Jetson
• 11: Advanced Drone Assembly
• 11.1: VMC and PCC Power
• 11.2: Buck Converter Mounting
• 11.3: FC ⟷ VMC Telemetry Cable
• 11.4: Top Accessory Plate Assembly
• 11.5: Zed Mini Camera Mounting
• 11.6: Assembly Review
• 12: Checkpoint 2: Stabilized Flight Test
• 13: Software
• 13.1: Flashing the SD Card
• 13.2: Connecting to the Jetson
• 13.3: Updating VMC Software
• 13.4: Running VMC Software
• 13.5: Connecting QGC
• 13.6: Flight Controller Parameters
• 13.7: GUI
• 14: Checkpoint 3: Position Flight Test
• 15: Peripheral Drone Assembly
• 15.1: Gimbal Assembly
• 15.2: Gimbal Testing
• 15.3: FPV Camera Testing
• 15.4: CSI Camera
• 15.5: LED Status Lights
• 15.6: LED Ring
• 16: Sphero RVR
• 17: Autonomy and Beyond
• 17.1: VS Code
• 17.2: Python
• 17.3: Git
• 17.4: GitHub
• 17.5: Jetson Development
• 17.6: Sandbox
• 17.7: Using Git
• 17.8: Docker
• 18: Diving Deeper
• 18.1: Glossary
• 18.2: Architecture
• 18.3: Control Loops
• 19: Troubleshooting
• 19.1: VMC
• 19.1.1: System Setup
• 19.1.2: Installing VMC Software

1 - AVR Drone Kit Contents

As you read through this page please be sure to refer to the glossary, which contains definitions of many of the components on this page. The Bell AVR drone kit includes all of the components required to build your own autonomous quadcopter. The kit provides a frame, motors, electronic speed controllers, flight controller, and several additional peripherals. This section will cover a majority of the components included for basic assembly of the drone.

Boxes in AVR Kit

The AVR kit will contain the following boxes. Be sure to read the label on each box to gain a high level understanding of the components inside.

AVR kit boxes from first shipment

Components for Basic Drone Assembly

The photo below shows the main components necessary for the first phase of the build, which consists of assembling the drone hardware, configuring the flight controller, and becoming familiar with manual, stabilized flight.

AVR kit components for manual flight

Components for Advanced Drone Assembly

In the second phase of the build you will be adding several peripherals to your AVR drone, installing software, and configuring parameters for better performance. These modifications will allow you to fly in a mode known as “Position Hold” where the drone will maintain position and altitude. This will lead to a much better experience when it comes to competition day.

AVR kit components for position hold flight

2 - 3D Printing

For AVR, you’ll need to 3D print some parts for your drone. While not needed immediately, these are good to get started with:

Explore each of the subsections to see what you’ll need to print.

Downloading

To download parts select the download button.

Onshape Download Button

Change the units from Meters to Millimeters.

Onshape Units Selection

The export page should resemble the following. Press OK.

Onshape Export Page

2.1 - Landing Gear

• AVR-LANDING-GEAR-MOUNT (x4)
  • STL file: AVR-LANDING-GEAR-MOUNT.stl
  • STEP file: AVR-LANDING-GEAR-MOUNT.stp
• AVR-LANDING-GEAR-BRACE (x4)
  • STL file: AVR-LANDING-GEAR-BRACE.stl
  • STEP file: AVR-LANDING-GEAR-BRACE.stp
• AVR-LANDING-GEAR-FOOT (x4)
  • STL file: AVR-LANDING-GEAR-FOOT.stl
  • STEP file: AVR-LANDING-GEAR-FOOT.stp

2.2 - Mounts

• AVR-CAM-ZED-MINI-MOUNT (x1)
  • STL file: AVR-CAM-ZED-MINI-MOUNT.stl
  • STEP file: AVR-CAM-ZED-MINI-MOUNT.stp
• AVR-BATTERY-STANDOFF-SMC (X1)
  • STL file: AVR-BATTERY-STANDOFF-SMC.stl
  • STEP file: AVR-BATTERY-STANDOFF-SMC.stp

An infill of 15% should be sufficient for these parts.

For best prints, it is advised that you rotate the part onto its back for printing.

Zed Mini Standard Orientation

Zed Mini Print Orientation

2.3 - Gimbal

• AVR-GIMBAL-BASE (x1)
  • STL file: AVR-GIMBAL-BASE.stl
  • STEP file: AVR-GIMBAL-BASE.stp
• AVR-GIMBAL-PAN (x1)
  • STL file: AVR-GIMBAL-PAN.stl
  • STEP file: AVR-GIMBAL-PAN.stp
• AVR-GIMBAL-TILT (x1)
  • STL file: AVR-GIMBAL-TILT.stl
  • STEP file: AVR-GIMBAL-TILT.stp

An infill of 15% should be sufficient for these parts.

3 - AVR Drone CAD Model

Teams can find a representative model of the drone by following this link to Onshape

Front View

Isometric View

Side View

4 - Basic Drone Assembly

This section is a complete guide on how to build the Bell AVR drone. It is recommended to read this guide thoroughly and in order. At the bottom of each page, there are navigation buttons that will allow you to proceed to the next section or visit the previous one.

Our goal in this section is to get you to Checkpoint #1: Flight Test, which consists of the ability to manually pilot the drone indoors in a stabilized flight mode.

Below are photos of what your assembled kit will look like before your first flight test.

AVR drone ready for first flight

AVR drone right side view

A simple block diagram can be used to represent the components of the basic drone. As you move throughout this documentation keep these details in mind. It will help you gain a high-level understanding of what we’re trying to accomplish.

Block diagram of basic drone components

Let’s get started with assembly!

4.1 - ESC Mounting

Mounting

The Tekko32 4-in-1 ESC will be mounted underneath the bottom plate of the middle section. Locate the bottom plate as shown in the photo below. You will notice a small notch that indicates the front of the plate.

Look for the 6mm threaded nylon standoffs and bolts that will be used to mount the ESC. It’s important that the electronics from the ESC do not make contact with the carbon fiber plate. This could lead to a potential electrical short.

Mid bottom plate with nylon hardware

Your AVR kit comes with a small tube of blue Loctite. You’ll want to place a small drop of this inside each of the threaded standoffs. Don’t overdo it. Loctite can get messy and a little will go a long way.

Applying blue Loctite to 6mm nylon standoff

Mount the standoffs in the right rear corner of the plate facing downward as shown in the photo below.

Nylon bolts and standoffs in place

Flip the plate over so that the threaded standoffs are facing up. Run all of the ESC leads through the provided cutout.

Feeding ESC leads through the plate

Before placing the ESC on the standoffs you will need to install the rubber dampeners. You can find these inside a small ziploc bag in the ESC packaging.

The purpose of these rubber dampeners is to keep the ESC secure when placed onto the nylon standoffs.

ESC dampeners prior to installation

Working with rubber dampeners can sometimes be a bit challenging. We recommend using a tool with a flat tip such as a 2.0mm hex driver that you will be using throughout the AVR build process. Do not use a sharp or pointy tool such as a Phillips head screwdriver. You do not want to accidentally pierce the rubber dampeners.

Pinch the dampener and feed it into the hole with your fingers. Use the hex driver to push the rim of the dampener into place as shown in the photo below. Repeat the process for all four corners of the ESC.

Using a 2.0mm hex driver to install rubber dampener

Once all the dampeners have been installed proceed to place the ESC on the standoffs. You will need to use a bit of force to push the ESC into place.

Make sure the yellow XT60 connector is facing the towards the inside of the plate and not hanging off the edge.

ESC placed onto 6mm standoffs

Now that the ESC is in place use four more 6mm threaded standoffs to secure it. In the next phase of the build process you will “stack” a Power Distribution Unit (PDU) on top of the 4-in-1 ESC. Don’t forget to use a dab of Loctite on the standoffs.

ESC secured with standoffs ready for PDU

ESC mounting is complete! Before proceeding we recommend following the tip below.

Labeling ESC leads saves time and frustration

4.2 - Mid Plate Assembly

Standoff Mounting

We will be mounting the mid top plate to the bottom plate using M3x8mm standoffs and M3x6mm screws. Make sure your parts match up with the photo below.

Mid plates with 8mm standoffs and 6mm M3 screws

The mid bottom plate has several mounting holes around the outside edge. Locate the center hole on each edge of the plate. Place a screw in each hole.

Standoff with Loctite

A small dab of Loctite in each of the standoffs will help keep the plates secure. Screw each of the standoffs into place with a 2.0mm hex driver.

All four standoffs secured to mid bottom plate

Pixhawk FC Tray Mounting

Before securing the mid top plate we will mount the Pixhawk Flight Controller (FC) tray with four rubber dampeners. This is necessary to help isolate the FC from vibrations that are generated from the propellers.

FC tray, dampeners, and mid top plate

The following steps show installing the dampeners in the top plate first, but some prefer installing them in the tray and then attaching the tray to the top plate. Choose whatever method makes the most sense to you.

Use the same procedure as mounting the ESC dampeners. Pinch the dampener, push it into the hole, and use your 2mm hex driver to feed it through the plate. Do this for all four dampeners.

Dampener installation with 2mm hex driver

The photo below shows all four dampeners installed into the mid top plate. Proceed with installing the FC tray onto the dampeners.

FC tray ready for installation onto dampeners

You will have limited wiggle room when installing the FC tray onto the dampeners. Be patient. In a matter of no time you will become a dampener installation pro!

FC tray mounted onto mid top plate

Assembling Top and Bottom Plates

Place your mid top and bottom plates side by side as shown in the photo below.

Mid top and bottom plates ready to be secured

As we discussed in the previous section, motor order is incredibly important for you to have a successful flight test. Look at the motor position diagram below. Lay out each of your ESC leads in this same order.

Matching up ESCs with their motor position

Place Loctite in each of the standoffs and secure the mid top plate with four 6mm screws. Your mid plate assembly is now complete!

Completed mid plate assembly

4.3 - Motors and Arms

Overview

Motor position and rotation are incredibly important for any drone to fly properly. In your kit you will notice two motor boxes labeled CW (clockwise) and two CCW (counter clockwise). This represents the direction of rotation for each motor. Let’s revisit motor position and rotation in the image below:

PX4 motor position and rotation

Motor positions 1 and 2 require CCW rotating motors and motor positions 3 and 4 require CW rotating motors.

You may be wondering how to determine the rotation of each motor. There are two ways to determine this. The first, and less intuitive in our opinion, is to look at the motor can. The photo below shows the motor size (2812) and kV rating (900) printed in two different formats. The kV rating for the CCW rotating motor is printed before the motor size. The kV rating for the CW rotating motor is printed after the motor size.

CW (black cap) and CCW (silver cap) motors

With that out of the way let’s cover a much more intutive (in our opinion) way to determine motor rotation. It requires using the propellers included in your kit. The silver capped propeller is a CCW rotating propeller and is threaded in a way that it will only screw onto the CCW motors. The black capped propeller is a CW rotating propeller. It is threaded in a way that it will only screw onto the CW rotating motors.

The photo below shows an example of installing a CW rotating propeller. Hold the propeller in place and rotate the motor in a clockwise direction. If the thread pattern is correct the propeller will screw onto the motor shaft and lock into place.

CW propeller mounting

Repeat this process for each of the four motors and then use tape to label them, just like you did with your ESC leads. You will be glad you did later!

Label each of your four motors

You should have the following:

• Motor 1: CCW
• Motor 2: CCW
• Motor 3: CW
• Motor 4: CW

Attaching Motors to Arms

Inside each motor box there is a small ziploc bag of 4 x 8mm screws. In your AVR kit you will also find a ziploc bag of M3 washers.

The photo below shows the necessary parts for mounting the motor to the frame arm. You will follow this procedure for each of the four motor/arm assemblies.

Parts necessary for mounting each motor

A 2mm hex driver is necessary to secure each of the 8mm screws into the motor.

Place a small drop of blue Loctite on each screw as shown in the photo below.

Blue Loctite on motor screw

Loctite is useful in helping secure your screws and prevents them from coming loose.

Motor mounted and secured

Repeat this process for all four of the motors.

All four motor/arm assemblies complete

Attaching Arms to Midplate

Locate the M3 22mm screws and lock nuts in your AVR kit. These will be necessary for mounting the motor arms to the midplate and securing the 3D printed landing gear mount.

Parts for motor arm mounting

Each arm will require three 22mm screws and lock nuts. You will insert each of the screws through the top plate, arm, bottom plate, and landing gear mount. The lock nut will be secured from the bottom as shown in the photo below. A 5.5mm box driver is necessary for tightening the nut. Be sure to tighten each nut securely.

Securing lock nuts with 5.5mm driver

Repeat the installation process for each motor arm.

All four motor arms secured

Flip your AVR drone over and connect each of the motor leads to the corresponding ESC leads.

Motors and ESCs ready to be connected

Be sure to make a good connection between the male leads of the motor to the female leads of the ESC. You should not see any brass between each of the connections. This is important so that nothing comes loose or causes a potential short.

Motors and ESCs all wired up

Feed any excess cable slack between the top and bottom plates. You can use zip ties to clean up your cabling as shown in the photo below.

Zip ties keep you build nice and tidy

Motor position and rotation is an important part of any drone build. The photo below is a gentle reminder. It won’t be long before you have this photo memorized!

Motor position and rotation

4.4 - FC to ESC Wiring

FC Wiring

You may have noticed that the ESC has a connector with several flying leads coming out of it. These leads are what we will be connecting to the FC. The FC will send PWM (Pulse Width Modulation) signals to each of the motors to keep the AVR drone hovering in the air.

Remove the small white cable adapter from the ESC and gather the necessary parts for this phase of the build as seen in the photo below.

Parts for wiring FC to ESC

The image below shows the pinout for the ESC connector. We will be focused on wiring each of the motor leads (M1-M4) as well as VBAT and GND to the PWM module of the FC. We will not be using TLM or CURRENT.

Pull out four jumper cables from your AVR kit and to keep things simple make sure they mach up with each of the motor wire colors. They will be green (M1), yellow (M2), red (M3), and blue (M4) as seen in the image below.

Laying out wires for soldering

Remove the plastic female connector from one end of each jumper cable. This is easy to do once you understand how the connector works. There is a small tab that you can pry up and then slide the cable out. A small flat head screwdriver or tweezers area great tools to assist with this step.

Plastic connector with tab lifted up

Slide the wire all the way out and get rid of the plastic connector.

Wire removed from plastic connector

Slide the wire into the servo connector housing as shown in the photo below. Servo connectors can be found in a small envelope of miscellaneous parts in your kit. Refer back to the first photo in this section to see it.

Sliding wire into servo connector

The blue wire is now secured into the connector and represents motor #4 (M4).

M4 wire securely in place

We will repeat this step for M2 (yellow wire) and M3 (red wire).

The photo below shows how the cable will be attached to the PWM module from the Pixhawk. You will notice that the connector is plugged in horizontally across the top row of pins 2, 3, and 4. Pixhawk can support up to 8 motors (an octocopter) and each number represents a specific motor.

M2, M3, and M4 connector

Let’s repeat the same process for M1 (green), VBAT (red), and GND (black). You will remove each of the plastic female connectors and secure the wires into the servo connector.

M1, VBAT, and GND wires

Once again, pay attention to the ordering of your wires. Your second cable should look identical to the one below.

M1, VBAT, and GND in servo connector

Make sure your cables are plugged into the PWM module as shown below.

PWM module wired up

Here is a close up of the connections. This represents the FC side of the wiring. Now we will proceed with the ESC side.

PWM module close up

ESC Wiring

Go ahead and unplug your cables from the PWM module. Let’s take one last look at the ESC side connections before we solder.

Use wire cutters to cut off the plastic female connectors from the other end of the colored leads. Proceed with stripping off about 1/2" of the wire insulation.

Remove about 1/2" of insulation from the ESC leads. You will notice that the ESC leads already have some wire exposed.

Match up the wire color on the FC side with the same color on the ESC side. Twist the wires together using the “Twisted Helix” method described in the video below.

The photo below shows the blue M4 wire from the ESC connected to the M4 wire of the FC. The wires are secured using the “Twisted Helix” method.

Wires twisted and ready for soldering

Place solder all around the joint to strengthen the connection.

Soldering the ESC and FC M4 wires together

A little solder will go a long way. Don’t overdo it as you will need to slide the heat shrink over the joint next.

M4 wires soldered together

Slide the heat shrink over the connection and apply heat to it using a heat gun or a lighter.

Heat shrink applied to M4 wire

Repeat this process for the M2 (yellow) and M3 (red) wires.

M2, M3, and M4 wires soldered

Repeat the soldering process for M1 (green), VBAT (red), and GND (black). Your new cable should look like the photo below.

All wires soldered

Feel free to apply heat shrink over all your wires to keep things clean. If you don’t have heat shrink you can use electrical tape.

Plug your connectors into the Pixhawk PWM module as shown in the photo below.

The finished FC to ESC cable

In the bag of cables that came with your Pixhawk FC look for the 10 pin connector that attaches to the Pixhawk’s I/O PWM OUT port and the PWM IN port on the PWM module.

Connecting PWM module to Pixhawk

4.5 - FC Mounting

FC Mounting

Locate the sheet of 3M double-sided adhesive pads and cut one out. Then cut it in half.

3M double-sided pads

Place each half at the front and back of the Pixhawk FC.

Pad applied to Pixhawk FC

Center the FC over the top tray and press it firmly into place.

Pixhawk mounted to top tray

PWM Module Mounting

Let’s connect the cable we previously created to the ESC beneath the frame. You can see in the photo below that we’ve zip tied it to the mid bottom plate to keep it in place. Feed the other end of the cable to the top of the frame.

ESC/PWM cable secured to frame

Cut out a small piece of 3M tape and secure your PWM module to the frame as shown in the photo below. Wire up your connections.

PWM Module mounted and wired

RX Mounting

The radio receiver (RX) will be mounted next. You can find the RX in the FlySky FS-i6S box. The cable to connect the RX will be in the bag of cables inside the Pixhawk box.

RX module and cable

Mount the RX using 3M tape as shown below. Attach the cable to the PPM/SBUS RC port of the Pixhawk and the other end of the cable to the I-BUS SERVO port of the RX.

FS-iA6B RX Connected to Pixhawk

Power Module

The Pixhawk Power Module steps down the battery voltage for use by the FC. It also provides voltage and current monitoring. This monitoring will be critical for the AVR competition and will help teams understand the power profile of their drone. Both the power module and cable can be found in the Pixhawk box.

Pixhawk power module and cable

Plug the female XT60 connector of the power module into the male XT60 of the ESC. Then plug the FC cable into the port of the power module as shown in the photo below.

Connecting FC power module to ESC

Feed the power cable from the module to the top of the frame and plug it into the POWER1 port of the Pixhawk.

Pixhawk power connection

4.6 - Bottom Accessory Plate

Battery Tray Assembly

The parts necessary to mount the battery tray to the accessory plate are 10mm M3 screws, lock nuts, and washers.

Bottom accessory plate and battery tray

Insert the screws and washers from beneath the plate coming up through the battery tray. Secure each corner with a lock nut as shown in the photo below.

Battery try mounted to accessory plate

Attaching Accessory Plate

Let’s attach the bottom accessory plate to the mid plate assembly of the AVR frame. You will need the 60mm standoffs and 10mm M3 screws that come with your kit.

Standoffs and screws for accessory plate mounting

From the top of the midplate assembly locate the eight larger access holes. Place a 10mm screw through each access hole into the mid bottom plate. A pair of needle nose pliers are very helpful for this step.

Access hole for 10mm screw

Place a small drop of Loctite into the standoff and screw into place using a 2.0mm hex driver.

Loctite applied to 60mm standoff

Repeat this process for all eight standoffs. Flip your AVR frame over so that the standoffs are facing up. Place a drop of loctite into each of them.

Standoffs with Loctitue

Place the bottom accessory plate onto the standoffs and secure with 10mm screws.

Bottom accessory plate secured and ZED Mini holes facing front of frame

4.7 - Landing Gear

Landing Gear Drilling and Mounting

Your AVR kit ships with 4 x 9" aluminum rods that are used for landing gear. As you get further into the advanced part of the build you can shorten these rods with a metal hacksaw. Customization is largely dependent on what accessories you have mounted to your drone.

3D printed parts and aluminum rods for landing gear

Attaching the aluminmum rods to the landing gear mounts will require drilling holes in each rod. We will walk through this process in detail to ensure success and minimize frustration. You will need a drill, 1/16" bit, 1/8" bit, screw (or nail), and a Sharpie.

Tools necessary for drilling aluminum rod

The first thing you will need to do is place an aluminum rod into the landing gear mount as shown below. In most cases this will be a tight fit so we recommend using a bit of force and rotating the rod clockwise and counterclockwise. This will cause some of the plastic from inside the mount to wear away.

Placing the aluminum rod into the mount

In the photo below you can see some of the plastic shaved off inside the mount.

Repeat this process until the rod is flush with the bottom of the mount.

Landing gear mount with rod inserted

Use a Sharpie to mark a hole on one side of the rod. Do not mark both sides. There is little margin for error so we will drill one side and repeat this process for the other.

Marking a hole for drilling

It can be challenging to accurately drill a hole in the aluminum rod. Clamp the rod to a piece of wood and then place a screw or nail in the center of the Sharpie mark. Tap the screw several times with a hammer to create an indentation in the metal.

Tapping the screw into the rod

Use the 1/16" bit to drill a starter hole. The indentation you created will keep the bit from slipping around. This drill bit is very fragile so don’t use too much force.

Drilling 1/16" hole in rod

Now use the 1/8" drill bit to enlarge the hole. This will be the final size necessary for our M3 22mm screws.

Drilling 1/8" hole in rod

Place the rod back into the mount make sure it’s all the way in. Slide a 22mm screw through the mount and into the hole you just drilled. Make sure everything fits well and then mark the other side with your Sharpie.

Marking other side of rod for drilling

Repeat the tapping and driling process for the other side of the rod. Once that’s complete place the rod back into the mount, slide the 22mm screw all the way through, and secure the rod with a lock nut.

Screwing landing gear into the mount

Once all four rods are mounted we will proceed to attaching the landing gear braces which provide extra support.

Landing gear securely mounted

Landing Gear Brace Mounting

The landing brace provides additional support by securing the rod to the bottom accessory plate. Use two 8mm screws and lock nuts as shown in the photos below. Repeat this process for all four legs.

8mm screws through landing brace and accessory plate

Lock nuts securing landing brace

Landing brace installation complete

Landing Gear Foot Mounting

There’s a good chance that the feet of the landing gear will require press fitting onto the rod. You can use a 3/8" drill bit to shave some of the plastic from the foot.

If the foot is loose feel free to use a drop of hot glue to hold it in place.

Applying hot glue to landing gear foot

Repeat the process for all four feet.

Landing gear feet installed

4.8 - Prop Guard Assembly

Prop Guard Mounting

This section will guide you through the assembly of the propeller guards.

Locate the following items below in both your first and second kit shipments.

Prop Guard Components and Hardware

Fasten lower prop guard bracket to motor arm using agreed upon method.

Lower Bracket Fastened to Motor Arm

Fasten a short stand-off to the motor arm hole closest to the drone body arm using the M3 x 15mm bolt.

Securing Short Stand-off

Fasten the long stand-offs to the 3 mounting locations on the lower prop guard bracket using the M3 x 15mm bolts.

Securing Long Stand-offs to Lower Bracket

The assembly should match the following photo with the bottom prop guard and all stand-offs mounted.

Stand-offs and lower bracket installed

Stack two upper prop guard brackets on top of one another, place a M3 x 15mm bolt through the two holes, and fasten to one of the 4 stand-offs as shown in picture below.

Securing 1st Set of Upper Brackets

Stack the remaining 2 upper brackets such that the upper bracket sits on the lower bracket of the previous step; likewise, the current lower bracket should sit below the upper bracket from the previous step. Secure the brackets to the stand-off using a M3 x 15mm.

Securing 2nd Set of Upper Brackets

Check that the top brackets are stacked in the correct order and secure to the remaining 2 stand-offs with 2 M3 x 15mm bolts.

Assembled Prop Guard

Repeat on the remaining three motor arms.

Completed Drone with Prop Guards

Congrats, you have now properly assembled the prop guards to your AVR drone!

• Purchase the remaining M3 x 22mm bolts (Recommended solution)
  • Pros: Quick fix, doesn’t require any modifications to drone parts
  • Cons: Spend money and coordinate travel to store or buy online
• Repurpose the M3 x 22mm bolts currently used on the upper landing gear mounts for mounting the prop guards. The M3 x 20mm Nylon bolts included in your kit will act as a substitute for the Aluminum bolts on the upper landing gear mount.
  • Pros: Does not require purchase of additional supplies
  • Cons: Nylon hardware prone to breaking in substitute of Aluminum on landing gear mounting brackets
• Use Nylon M3 x 20mm bolts and nuts included in your kit to fasten prop guards to motor arms
  • Pros: Does not require purchase of additional supplies
  • Cons: Nylon hardware prone to loosening in a high vibration environment next to the motor. Loosening can be prevented by using a non-loctite thread locker applied to Nylon nuts and bolts. (See previous note about loctite being caustic to poly carbonate.)
• Counterbore prop guard motor arm mounting holes to accommodate shorter length Aluminum fasteners included in your kit.
  • Pros: Does not require purchase of any additional supplies.
  • Cons: Run the risk of ruining prop guard components if done improperly, it is aesy. If this approach is attempted, a drill press and appropriately sized end mill are suggested to perform this operation.

5 - Battery Management

5.1 - Overview

Safety Overview

Please ensure all team members have read the LiPO guidelines were included with the SMC battery as well as the manual for the Hitec charger.

You can learn more about these products at the links below:

• SMC True Spec DV Extreme 14.8V 5200mAh 135C Battery
• Hitect RDX1 Pro charger

Key Safety Points

• Always charge batteries using the proper settings. Improper charge settings may result in a catastrophic failure of the battery.
• Never charge batteries unattended. If, during a charge, you need to leave for any reason, stop the charge and disconnect the battery from the charger. You can restart charging when you return.
• If a battery ever becomes warm/hot during charge, or starts to swell, it should be removed from the charger and taken outside where it cannot cause damage if it fails. If a battery fails as a result of damage or misuse it may result in fire.
• Never leave a battery connected to your device or charger when not in active use. This may cause a parasitic draw on the battery which may lead it to become over-discharged.

LiPO Battery Voltage Range

• 4.20V per cell represents a fully charged cell.
• 3.00V per cell is the very lowest the battery can go without sustaining damage.
• 3.70V per cell is the “Nominal Voltage” which is the “named” voltage of the cell. This voltage is used as a standard to identify the cell/battery type.
• 3.5-3.7V per cell is the voltage we would recommend landing at.

SMC Battery

The battery you will be using is a SMC 14.8V 5200mAh 135C Battery.

Definitions

• Battery: A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices.
• mAh: is an abbreviation for milliamp hour and is a unit that measures (electric) power over time. It is commonly used to measure the energy capacity of a battery. In general, the more mAh and the longer the battery capacity or battery “run time.”
• C-Rating: is a shorthand representation of how many amps the cells can supply on a continuous basis without failing.
• Cell Count: How many cells are in series to make the overall voltage of the pack. In this case, 4 cells are in series to make 14.8V nominal, or 16.8V when fully charged. Sometimes referred to as a 4S battery, the “S” refers to “series” to tell us how many cells are comprising the battery pack.

The Charger: Hitec RDX1 Pro

The RDX1 Pro is one of Hitec’s most popular single-channel multi-chemistry battery chargers. It features a 100W Power supply as well as an integrated 6-cell balancer. The RDX1 Pro is capable of charging 1S-6S batteries.

Hitec RDX1 Pro Charger

Battery Storage Bag

Your kit includes a battery storage bag that can be used for storage, transport, and charging.

Lipo storage bag

We recommend you use this bag as a charging mat, this will give you an added layer of protection between the battery and the charging surface. Always remember to charge batteries on a non-combustible surface.

What to Do in Case of Fire

If you follow the safety guidelines provided, you should be perfectly safe. However, in the event that something has gone wrong, and there is a battery (LiPo) fire, take the appropriate steps:

1. First, get yourself and those around you to safety. Drones, computers, etc. are replaceable, while you (and your lungs) are not. Battery fires produce very toxic smoke, and you do NOT want to breathe it in.
2. Get help. This depends on your specific situation, but this may be to pull a nearby fire alarm (contrary to popular belief, pulling the alarm does not set off sprinklers), call 911, or call your security department.

After doing the above two steps, and only if you’re comfortable with it and does not pose any danger to you, you can attempt to fight the fire. Your most effective tool is a class D fire extinguisher. These are special fire extinguishers that are meant to put out combustible metals (such as Lithium) and stand out as being bright yellow.

Example class D Copper powder fire extinguisher

However, class D fire extinguishers tend to be uncommon. If a class D fire extinguisher is available, pull the safety pin, aim the nozzle, and squeeze the handle. These tend to be quite heavy, so you may need an additional person to assist.

If a class D fire extinguisher is not available, your next best bet is to throw a fire blanket over the fire to smother it as much as possible. This won’t put it out but it will supress the flames. Most labs have a fire blanket.

Example fire blanket

Finally, as a last resort, pour sand or dirt on the fire. This is generally what we have on hand at competition events for safety and acts similarly to a fire blanket.

Low-tech solutions can be effective

A normal, red, class ABC fire extinguisher does very little to put out a battery fire. Don’t waste your time unless you have absolutely nothing else to smother the flames with.

A class ABC fire extinguisher is not effective for a battery fire

5.2 - Charging

Charging the Battery

Please read the manual prior to beginning your first charge. The manual comes with your charger or you can find a digital version here.

Please watch the video below to understand the recommended LiPo charging process.

5.3 - Storage

Battery Storage

After using the battery, give it approximately 30 minutes to cool down.

Determine when the battery will be used going forward. If the battery will be used again within 24 hours, proceed to fully charge the battery. The goal is to minimize the time lithium batteries sit fully charged. Long periods of maintaining full charge will dramatically reduce the lifespan of the battery pack, and can lead to swelling/premature failure.

If the battery will not be used in the next 24-48 hours, please proceed with a storage cycle, as demonstrated in the video below.

The storage voltage range is typically between 3.70-3.85V per cell. However, lower voltages, down to 3.4V per cell are unlikely to cause issues, especially over shorter time periods. If the battery will be in storage for more than a week, it’s best to perform a proper storage cycle as time permits.

6 - RC Transmitter Setup

Setup

The FlySky FS-i6S RC transmitter is a highly configurable radio controller with a touch screen, supporting up to 10 control channels at the same time. In order to use it with the AVR drone, some setup is required, both for the RC transmitter and for the FC. On this page, we will go into detail on how to set up the RC transmitter so that it can be used to safely control the drone.

The radio controller box should include a quick start guide. A more detailed user manual for the radio controller is available for download below.

The following sections will cover numerous aspects of the transmitter configuration required to fly your AVR drone.

6.1 - Basic Usage

Overview

To turn on the transmitter, press and hold the two power buttons on the front of the device until the screen lights up. After you see the logo, you will be presented with the home screen.

You might see a warning when you turn on the transmitter about switch positions. Just follow the instructions provided on the screen to continue to the home screen.

Make sure all switches are in the up position to continue to the home screen

The transmitter contains a touch screen used for displaying status info and for setup purposes. The home screen has three different views. You can switch views by swiping left and right, where the bottom indicator shows you which screen you are on (when you start the transmitter, you see the center screen).

Home screen of transmitter

The left screen shows you the current value sent over all channels, while the right screen shows information about sensors connected to the transmitter.

Left screen showing channel values

One thing that is helpful to gain an understanding of how your flight sticks map to various channels is to swipe to the channel view and move your sticks around. You should see the channel values update as you move the left and right sticks.

Screen Unlock

By default the transmitter settings will be locked which prevents you from accidentally changing a setting. To unlock the screen press and hold the lock icon for 2 seconds.

Press and hold 2 seconds to unlock

After unlocking you will see the settings icon with the wrench and screwdriver.

Settings icon on home screen

Configuration

Configuration is done by pressing the settings icon. The next screen has two different views: the function view and the system view. The function view provides options that change how the different sticks, buttons, and dials on the transmitter are transformed to channel values.

Function view

The system view provides options for setting up the transmitter itself. You can change to the system view by pressing SYS.

System view

Screen Lock Timeout

You will likely find that the screen lock timeout of 5 seconds is way too short. We recommend changing this to 5 minutes while you’re becoming familiar with the transmitter. You can do this by going to the system menu and selecting screen lock.

Screen lock in system menu

You have several screen lock timeout options. Select the one you’re most comfortable with.

Screen lock timeout

6.2 - Binding the RC Receiver

The RC receiver module has already been installed on the drone in a previous step. Please verify that it is correctly connected on both the receiver (RX) side and on the FC side as shown in the photo below.

Aside from the physical connection we also need to establish a wireless connection between the transmitter and the receiver. This wireless connection happens through a process known as binding. Binding is what will allow us to control the AVR drone with the transmitter and change flight modes, which will become important in the competition.

Out of the box, the receiver and transmitter should be automatically bound to each other. If this is the case, the RC transmitter display would look similar to the picture below when both transmitter and receiver are turned on (receiving power). Please note the RX battery bar. If this shows a question mark (while the receiver is getting powered), then you will need to go through the binding process. We will cover that shortly.

TX main screen showing RX connected

The TX battery bar shows the remaining capacity of the batteries in the transmitter. However, the RX battery bar does NOT actually show the battery capacity of the drone. It reports a reading of the voltage level (between 4.0 and 8.4 V) that is provided to the receiver module by the FC, which should always be 5.0 V. In our case, it is only useful for verifying that the transmitter and receiver module are communicating with each other.

If your transmitter and receiver are already bound you can skip to the next section labeled Setting the Output Mode. If the transmitter and receiver are not bound, you can do it yourself. Make sure the FC is not powered by the battery or USB cable. Insert the bind plug in the rightmost vertical slot (labeled B/VCC) on the receiver module, see the picture below. You will find the bind plug in a small plastic bag in the transmitter box. The cable that connects to the FC should remain as shown below.

Receiver with cable going to FC (black/red/white) and bind plug in B/VCC slot

Turn on the transmitter and go to the system view in the settings menu. Select RX bind. It will wait for the receiver to be turned on in bind mode as well. You should now power the FC, which will also power the RC receiver module. The easiest way is to power the FC with a micro-USB cable. When power is provided, the receiver module will go into bind mode because of the jumper wire. The binding procedure should be finished automatically (you might not even notice).

Power everything down and you should now remove the bind plug from the receiver module. It should not remain in the receiver as it will trigger the binding procedure again every time the receiver module is powered. The next time you power up your transmitter and receiver they will be communicating.

6.3 - Setting the Output Mode

In the world of drones and radio controllers, there are a lot of different protocols in use. More information about these different protocols can be found here. The FlySky FS-iA6B receiver that was included with the FlySky FS-i6S transmitter supports PWM, PPM, S.BUS, and i-BUS output, but the FC in the AVR kit only supports PPM and S.BUS. For the AVR drone, it is recommended to use the S.BUS protocol since it is the most stable of the two and supports more channels.

Configuring the RC receiver to output the S.BUS protocol can be done in the OUTPUT MODE screen shown below. You can find the OUTPUT MODE screen on the system view in the settings menu. Everything should be configured as shown in the picture. This will set PPM and S.BUS as the output communication protocols, which will be available on separate pins. The FC has already been connected to the pins on which S.BUS output will be available.

Output mode configured for PPM and S.BUS

Changes are automatically saved so you can tap on the back arrow to go to the previous menu. If you power down your transmitter these settings will still be maintained.

6.4 - Setting Up Channels on the RC Transmitter

The receiver module supports up to 10 channels when using the S.BUS protocol. The first 4 channels are used for basic control with the transmitter sticks, leaving several free channels which can be mapped to auxiliary control switches. Assigning switches, dials, and buttons on the transmitter to channels can be done using the Aux. channels option under the Function tab in the Settings menu.

These channels will be useful throughout AVR and will let us do things like toggle a switch to change the current flight mode of the drone.

Auxiliary channels in Function menu

You can press the icon to change the kind of input (STX = stick, SWX = switch, VRX = dial, KEY = button). Pressing the text label you can specify which exact input should be mapped to the channel. It is also explained in section 6.7 of the transmitter manual.

For the AVR drone, we provide a default channel setup which allows for maximum utility of the available channels, which can be found below. In future references, we will always use the channel setup as provided here.

The following steps will walk you through assigning Channel 5 to SWA. First, tap on the big circle with the line through it.

Channel 5 setup

The following screen allows you to assign CH5 to a switch. You will select SWx.

Assigning a channel to a switch

After selecting SWx you will be presented with a screen that lets you select one of the following switches: SWA, SWB, SWC, or SWD for Channel 5. In this case, we will select SWA.

Select SWA for Channel 5

Repeat these steps for CH6, CH7, and CH8 based on the table above. After completing the steps you can go back to the home screen and swipe right to see your channel outputs. Swipe down to see CH5 - CH8 outputs. With all switches in their default position (up) you should see the output as shown in the image below.

Default output for CH5-CH8 - all switches up

Now toggle all of your switches to the downward position. You should notice that the output changes and should be identical to the image below.

All switches toggled down

6.5 - Setting Up Failsafe

By default, when the RC receiver loses connection with the transmitter, the receiver will continue sending the latest known stick position to the FC. While this can be useful in some situations, it is very dangerous for flying drones: it can result in fly-away situations whenever signal is lost! To change this, the failsafe option in the function tab of the settings menu can be used. It allows us to set a desired value for each channel to take on whenever the transmitter loses connection.

While the FC should be able to detect signal loss and has different options to react in such a situation, we also recommend a good failsafe setup on the RC transmitter, as a last resort in case the FC does not detect the signal loss.

We recommend setting the failsafe options as follows in terms of stick and switch positions. This will cause the drone to shut down its motors when the FC does not detect the signal loss. This is the only viable option, it is not safe to keep the drone in the air when we do not have any control over it.

We will later have a look at failsafe options in the FC configuration as well. For now, we will set the RC transmitter failsafe to:

• Left stick (throttle/yaw) to the bottom and horizontally centered.
• Right stick (pitch/roll) both horizontally and vertically centered.
• Switches SWA, SWB, and SWC in the upward position, SWD in the downward position.

This will set the throttle to zero and reset the yaw, roll, and pitch to neutral angles. We will later assign functions to the switches, where the upper position will be the default state. We will assign a kill switch function to SWD. With this failsafe setting, the receiver will emulate the kill switch being flipped when it loses connection, and ultimately disable the motors.

Default stick/switch positions with SWD kill switch enabled (toggled down)

To begin setting up failsafe values, go to the Failsafe screen from the Function screen in the Settings menu.

Default failsafe screen

To set up a failsafe for a channel, tap the Off button next to the channel. In the screen that appears, tap the On button to enable the failsafe for that channel.

Setting up failsafe for CH1

Now make sure the stick/switch belonging to that channel is in the correct position. In the case of CH1, which is assigned to the right stick, it will be horizontally and vertically centered. Now tap the Setup button to save this position.

CH1 failsafe value set to 0%

After tapping Setup you will be taken to the main failsafe screen where you can configure the failsafe for the rest of the channels.

CH1 failsafe value set to 0% (right stick centered)

Go ahead and complete the failsafe configuration for Channels 2, 3, and 4. When finished you should see something identical to the image below.

Failsafe configuration for Channels 1-4

We will now set up failsafe values for the switches we configured in the previous section. Let’s run through an example of doing this for CH5, which is attached to SWA. Make sure SWA, SWB, and SWC are in the up position and SWD is in the down position.

Setting up failsafe for CH5 attached to SWA

Tap On and then Setup for CH5. This will set a value of -100% for CH5 (SWA up position) as shown below.

CH5/SWA default switch position up with a value of -100%

Tap the back arrow and complete the process for Channels 6-8. Keep in mind that since CH8 (switch SWD) is in a downward position the value will be +100% as shown in the photo below.

CH8/SWD down switch position with a value of +100%

The following photo shows the final failsafe values for Channels 5-8. These are the values that will be sent from the receiver to the FC in case there is a loss of signal with the transmitter.

Failsafe configuration for channels 5-8

The failsafe values for all channels have been configured. In the end, you should have the following failsafe values for each of the channels:

Your transmitter setup is now complete and we will move on to setting up and calibrating the FC.

7 - Flight Controller Setup and Calibration w/ QGC

QGroundControl (QGC)

Ground control software is used for configuration and monitoring of your AVR drone. We will be using QGroundControl as our ground control software of choice throughout AVR. With QGC you can upload firmware, configure flight modes, calibrate sensors and much more. It also provides different ways of controlling the drone, such as an autonomous mission planner.

QGC can be downloaded and installed on Windows, Mac, and Linux operating systems. You can find the necessary installer by going to the downloads page. Using the daily build, follow the steps here for your operating system.

Go ahead and install QGC before proceeding to the next section.

sudo apt install libfuse2

The following sections will guide you through the process of using QGC to set up your FC. Let’s get started!

7.1 - PX4 Firmware

Uploading PX4 firmware using QGC

PX4 is firmware that we will be running on the AVR drone. It is an open-source flight stack containing all the software necessary to get your drone into the air.

To facilitate some of the extra functionality required for our drone to fly in stabilized flight mode without a GPS, you will need a custom version of PX4 Bell engineers have developed. Go to the latest AVR software release and download the px4_fmu-v6c_default.<px4 version>.<hash>.px4 file.

In the Firmware screen in QGroundControl you can upload a new version of PX4. To access the firmware screen make sure to click on the Q logo in the top left of the screen and then click on Vehicle Setup > Firmware. You will see the following screen.

Firmware upload screen in QGC

QGC will ask you to plug in your FC using a USB cable. A popup will appear that asks you which firmware you want to use. select “Advanced Settings”, then “Custom firmware file…”

Loading PX4 Pro Stable Release onto FC

Then click “Ok” and select the firmware file you downloaded. Now, you will see a progress bar. This process should take no more than 2-3 minutes.

After the PX4 firmware is successfully loaded you will be presented with the default Vehicle Setup screen. It is necessary to go through the following steps to ensure a reliable and stable first flight.

QGC Vehicle Setup screen right after PX4 firmware load

7.2 - Airframe

The AVR drone is 500mm in size and is represented by the diagonal distance between motors. If you were to measure the distance it would be close to 500mm. In QGC you will now configure the drone frame, which will provide optimal settings for flight. Select Airframe in the navigation menu.

Airframe Setup screen

Scroll down in the Airframe Setup screen and look for Quadrotor x. Click on the dropdown menu and select S500 Generic as the airframe type. Scroll back up and click the Apply and Restart button in the top right of QGC. You will be asked to confirm that you want to restart. Click Apply and the airframe setting will be saved.

While the FC is rebooting QGC will disconnect for a few moments and then automatically reconnect.

7.3 - Sensors

The Sensors screen lists most of the sensors that are available to the FC (internal or external). It allows you to start the calibration process for the listed sensors. This step is very important for stable flights. It is required to do the calibration at least once and should be repeated whenever adding new components to the AVR drone or if flight becomes less stable.

Click on Sensors in the navigation menu and let’s walk through the calibration process for each sensor.

Default Sensors screen

Compass

The compass is important for your AVR drone to maintain proper orientation. Click on the Compass button and you will be asked to begin the calibration process. This process requires you to position the AVR drone in a number of set orientations and rotate the vehicle about the specified axis.

Default compass sensor screen before calibration begins.

Click Ok to proceed with the compass calibration. QGC will automatically recognize the orientation of the AVR drone and provide a yellow highlight as shown in the image below.

Begin the process of rotating the AVR drone around the highlighted axis.

Once the orientation is highlighted you can begin rotating the drone until the box is highlighted green. This generally requires one 360 degree rotation around the axis. The image below shows three of the six orientations completed.

Compass calibration in progress

After completing the calibration of all axes click Ok to return to the sensor setup. It is important to reboot your FC prior to flight, but for now we will move on to calibrating the Gyroscope.

Gyroscope

The gyroscope is an important sensor that will be used to keep your AVR drone level when hovering. Now that the compass calibration is complete you will click on Gyroscope to being the process. This will be much easier than compass calibration! Make sure your AVR drone is on a level surface and click Ok.

After a few seconds, the gyroscope calibration will be complete.

Successful gyroscope calibration

Accelerometer

The accelerometer works in conjunction with the gyroscope to keep your AVR drone level along each axis. Click on Accelerometer and then Ok to begin the calibration process.

This process is fairly similar to compass calibration but does not require you to rotate the drone around each axis. You simply need to hold the drone level in each orientation. QGC will detect the orientation, which is denoted by the yellow border.

Accelerometer calibration in progress

Hold your AVR drone steady in each orientation for approximately 5-10 seconds. As you complete each axis the border will turn green in QGC.

Accelerometer calibration complete

Level Horizon

Level horizon is a simple calibration to make sure your FC understands the default level position when powered on. Click on the Level Horizon button and then Ok. This process will take more than a couple of seconds to complete.

Level Horizon calibration complete

Orientations

Given we have mounted the FC in its default orientation (facing up and forward) this calibration is unnecessary.

Nice work! You have calibrated the necessary sensors for your AVR drone to be able to know its orientation and keep level during flight. The following Summary screen shows the successful steps completed in green. Now we will move onto setting up the Radio (aka Transmitter).

Summary screen showing all sensors calibrated and ready for flight

7.4 - Radio

In the RC Transmitter Setup section we configured the stick and switch channels. Now we will calibrate the endpoints of these channels so they can be saved to the FC. QGC makes this very easy to do and the process can be observed in the following video.

Now that your transmitter has been calibrated using the Radio screen in QGC we will move onto setting up our flight modes.

7.5 - Flight Modes, Arming, and Kill Switch

The primary goal of the basic assembly is to be able to pilot the AVR drone in stabilized mode. Therefore we will configure SWB (3 position switch) to control which flight mode we’re in. In addition to setting up flight modes, we will also enable a kill switch on SWD (2 position switch). This is VERY IMPORTANT in case the AVR drone needs to be shut down due to a fly-away or complete loss of control. The video below demonstrates this process.

7.6 - Power

Power Setup

For correct display of battery percentage, you should always specify the correct number of cells in the battery. In our case this will be 4 since we are using a 4 cell LiPo battery. You should also calculate the value for the voltage divider to calibrate the voltage readings coming from the power module. This can be done by measuring the overall voltage with the Venom cell checker. Then you can input the measured voltage into the Calculate Voltage Divider prompt.

These settings will provide you with an accurate battery percentage while the drone is idle on the ground, so you can determine whether it is still safe to take off and when you need to land. PX4 also has a fail-safe that prevents arming when the battery percentage is too low. The video below walks through the power setup.

ESC Calibration

To ensure that all motors correctly respond to commands coming from the FC, you should perform an ESC “calibration”. It makes sure that the ESCs are aware of the minimum and maximum pulse-width modulation (PWM) values that the FC provides. This can be done by pressing the ESC calibration button and following the on-screen prompts. The calibration process requires a USB connection since it involves steps where you have to disconnect and reconnect the battery. The video below covers this in detail.

7.7 - Safety

Safety Setup

Previously, in the RC Transmitter Setup section, we covered Setting Up Failsafe. In QGC we need to make sure we disable some of the failsafe options, as many of them are related to GPS-enabled drones. AVR is all about indoor navigation in a GPS-denied environment therefore it warrants a different safety configuration. The video below walks through the setup process.

7.8 - Motor Test

One physical check that must be done to ensure your AVR drone hovers properly is to verify that the motor positions and rotations are correct. We previously covered ESC wiring which should ensure that the FC output is going to the right motor.

We discussed motor rotation when installing the frame arms and learned that the rotation for each motor is important. You may recall the image below and we will refer to it one more time before we run the motor test.

Motor position and rotation diagram

Motor positions and propellers installed with the nose of the AVR drone pointed forward

The video below will walk through the necessary steps to run the position and rotation test.

8 - Checkpoint 1: Initial Flight Test

8.1 - Before You Fly

Much of the work done so far has created the foundation for your AVR drone. The following videos will talk through the process you should follow each time you fly. These are important checks to make sure your AVR drone operates correctly and keeps all team members safe.

Pre-flight Checks

Installing Propellers

Place your AVR drone in its desired takeoff location and install the propellers as demonstrated in the video below.

8.2 - Flight Test

Let’s Fly!

We have covered a tremendous amount of information to get to this phase of the competition. Now it’s time for our first flight test! Watch the video below to understand the basics of getting your AVR drone in the air and how to control it.

8.3 - After You Fly

As discussed in the Flight Test video always be sure to power down your AVR drone and run a voltage check on your battery. Always refer back to the battery documentation if you have any questions regarding charging, maintaining, and storing your battery.

Congrats on building your AVR drone, configuring it, and performing your first flight test!

We know it has been a challenging and hopefully rewarding journey, and there will be a lot more exciting things planned as you work towards the competition.

9 - Peripheral Control Computer (PCC)

9.1 - Physical Assembly

Assembling the Peripheral Control Computer is fairly easy, and just requires a bit of soldering.

Tools Needed

• Soldering Iron (I used an iron at 450C, but the recommended solder melts around 200C)
• Soldering Iron Tip Cleaner
• Solder (Recommend 60/40 Tin/Lead)
• Wire Strippers
• Breadboard

PCC Parts - Box 5

Before we get started, let’s make sure we have all the necessary parts for the PCC.

The PCC ships in 4 plastic bags consisting of the following:

• 1 x Adafruit Feather M4 Express (Pictured upper left)
  • 2 x 16x1 Male Pin Headers
• 1 x Adafruit Prop Maker Featherwing (Pictured upper middle)
  • 2 x 16x1 Male Pin Headers
• 1 x Adafruit Servo/PWM Featherwing (Pictured upper right)
  • 2 x 16x1 Male Pin Headers
  • 2 x 4x3 Male Pin Headers
  • 1 x 2 screw-terminal thru-hole adapter
• 1 x Adafruit Featherwing Tripler (Pictured Bottom)
  • 3 x 12x1 Female Pin Headers
  • 3 x 16x1 Female Pin Headers

Solder the Feather M4 Express

Before we dive in, let’s go over a couple of warnings and tips.

Step 1: Assemble Feather M4 Express

The Feather M4 is the brains of the PCC. It receives commands from the VMC and executes them in order to change the color of the LEDs or move a servo.

You’ll see that the M4 Express has 16 pins along its left side (assuming the micro USB port is the top), and 12 pins along the right side. Because the M4 Express ships with 2 x 16x1 headers, we need to cut one side down. You should be able to use scissors to trim one of the headers to 11 pins. Why 11? The PCC doesn’t make use of the “Bat” pin and in our testing including this pin caused issues. For this reason, we chose to omit this pin. You can see it is missing if you expand the picture below:

M4 Express being soldered

With the headers cut to length, grab your breadboard and place the headers in the “a” and “g” column as in the picture above, with the long side of the headers going into the breadboard. Make sure it’s lined up correctly and set the M4 Express onto the pins. The feather should not move around anymore and you can begin soldering.

For the smoothest outcome, start by soldering the pins in the four corners so the pins don’t move around on you when soldering the rest. I like to use a hot iron (around 450°C) with a fine tip for this.

Use the following steps to complete a solder joint:

1. Place the iron tip on the feather such that it is making contact with the protruding pin as well as the donut-shaped pad that the pin protrudes through.
2. If your iron is clean and hot, after about 5 seconds you should be able to move your solder in to touch the iron at the junction where the iron and the pin meet. The solder should melt almost immediately, and wick around the pin.
3. Don’t go overboard with the solder. You want just enough that the solder forms a cone shape around the pin. Less really is more here.
4. Pull the solder and iron away from the board and inspect your work.
5. Repeat steps 1 through 4 for each pin on the M4 Express.

Once complete you should have solder joints that look like this:

Completed M4 Express

Once you’re happy with your soldering work, grab each end (the micro-usb and opposite side) and slowly inch the feather out of the breadboard. It is very easy to bend a pin trying to remove it so just go slow and be careful.

Hopefully that wasn’t too bad! Now we need to repeat similar steps for the prop maker and the servo featherwing.

Solder the Prop Maker

The steps for the Prop Maker are the same as the M4 Express.

Make sure to cut one set of male headers down to 11 pins and skip the “Bat” pinhole.

Place the headers into the breadboard and solder all the pins.

Prop Maker being soldered

Solder the Servo/PWM Featherwing

For the Servo featherwing its easiest if you solder the 4x3 headers first:

1. Place one of the headers into the breadboard first.
2. Place the other set short-end first into the top of the featherwing.
3. Flip the featherwing upside down and onto the headers already inserted in the breadboard.
4. Solder these pins

Servo Featherwing placed upside down on the 4x2 headers

Once the 4x3 headers are soldered in place, remove the featherwing from the breadboard and solder the 16x1 headers, while remembering to trim the short side to 11 pins.

Servo Featherwing being soldered

Finally, we need to install the screw terminal:

1. Remove the Featherwing from the breadboard.
2. Place the screw terminal in the top of the circuit board with the terminals facing outward
3. Turn the assembly upside down and place it on top of the breadboard.
4. Solder the screw terminal on.

Installing the USB Power Jumper

In order to run the PCC from a laptop for testing, we’ll have to make a USB power jumper to connect the USB power from your laptop to the servo power rails. In the future, once the PCC makes its way onto the drone, the servos will have a dedicated power supply.‌

First, we need to install a pin for the wire to connect to:‌

• Find a spare male pin from the headers we used in the above steps
• Place the pin into the area labeled “USB” on the servo featherwing (highlighted below)

• Solder the pin from the underside

Now we need to make the jumper wire. Take a spare wire from the kit (there should be a whole bag with the proper connectors already on them) and cut it down to just about an inch. Then strip about 5mm from the end like shown below:​

Finally, place the terminated end on the pin we just soldered, and the bare end into the + side of the terminal block and screw it down.

That’s it! The Servo Featherwing is now complete.

Solder the Featherwing Tripler

The tripler can be the trickiest piece to solder if you don’t follow this simple trick:

Hold the tripler circuit board with the silkscreen print facing upwards.

Drop the headers into the board as shown in the picture below:

Then turn the whole thing over on its back (being careful not to drop the headers) and then solder each pin from here.

Back of soldered tripler for reference

Adding the Laser Trigger

For the 2022 season, we are making use of a laser pointer. In order to be able to trigger the laser from the PCC we need to add some extra pins connected to GND and A4 on the express to the Tripler.

Start by placing the Tripler down, and lining up the M4 Express with the headers on the Tripler like shown below:

Tripler

I used a spare male dupont-connector wire to mark the pins of interest by plugging them into the desired spots on the header.

Next, grab some of the spare header pins and break two single-pins off:

Separated Pin

Place them into the holes on the Tripler right next to the point of interest and use something flat to place over the board to hold the pins in place while you flip it over. I used an old PCB but you could use paper, cardboard, etc. Now solder the pins in place. You should now have something like this:

Soldered Pins

Now place a female dupont-connector wire on the pins and bend them down to the right. They should fit perfectly between the header rows like such:

Bent Pins

Thats it! Move on to the next step!

Putting It All Together

Now we can just pop the Featherwings into the Tripler as shown below:

Completed PCC

Now your PCC is assembled!

9.2 - Flash the PCC

Setup

To flash your PCC, you need to download and install a tool called BOSSA first.

Windows/MacOS

Go to this page and download and install the bossa-x64-<version>.msi file for Windows, or the bossa-<version>.dmg file for MacOS. Make sure to install the device drivers that it prompts you to install as well.

Download this installer file

Run through the setup wizard

Linux

For Linux, you’ll need to compile and run BOSSA from source.

git clone https://github.com/shumatech/BOSSA
sudo apt install build-essential libwxgtk3.0-gtk3-dev libreadline-dev
# if libwxgtk3.0-gtk3-dev cannot be found, run `sudo apt-cache search libwxgt*`
# and install the next closest match
cd BOSSA
make -j
./bin/bossa

Flashing

After getting BOSSA installed, you need to also download the PCC firmware that you’ll be loading. Go to the AVR release page and download the pcc_firmware.<version>.bin file.

Download this firmware file

Now you’re ready to flash your PCC! Follow the next steps exactly to not run into any issues.

First, plug your PCC into your computer with the provided MicroUSB cable.

Quickly double-tap the little reset button right next to the MicroUSB connector. The LED next to the button should briefly flash red before turning solid green.

This puts the PCC into bootloader mode so we can flash new firmware.

Open BOSSA and select the COM port that has now shown up from the previous step, or the serial device ttyACM0. Also select the firmware file you downloaded.

In BOSSA, make sure to put in a flash offset of 0x4000 and select “Erase all”.

BOSSA settings

Now, you can hit the “Write” button!

Flashing complete

You can also optionally click the “Verify” button as well just to make sure everything flashed correctly.

Verificiation complete

Finally, to get the PCC out of bootloader mode, and make sure the firmware is working correctly, unplug the PCC and plug it back in, or press the reset button once. The bright green LED should remain off and the original COM port should show back up in device manager.

9.3 - Test the PCC

Physical Setup

On your PCC, we’ll need to make use of a USB power jumper to power the servos from our laptop.

Installed USB power jumper

Plug your servos and LED strip into the designated connections on the PCC:

• The LED strip plugs into the prop-maker featherwing
• The servos plug into channels 0-3, with the yellow signal wire of the servo facing the Adafruit logo on the PCB.

Software Setup

Now it’s time to download the AVR GUI program.

Windows

Go to the latest AVR software release and download the AVRGUI.<hash>.exe file. Like QGroundControl, you may need to bypass some warnings about being an untrusted file.

Select “Keep”

Select “Keep anyway”

Other Platforms

For Linux and MacOS, we recommend running the AVR GUI from source. You’ll need to have Python 3.9 or Python 3.10 installed.

For Linux users, here’s how you can easily install Python 3.10:

sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt install python3-pip python3.10 python3.10-venv
sudo -H python3.10 -m pip install pip wheel --upgrade

For MacOS users, go to the Python releases page for MacOS and download an appropriate installer: https://www.python.org/downloads/macos/

Now, run the following commands to clone the code repository where desired, and setup the dependencies.

# clone the repo
git clone https://github.com/bellflight/AVR-2022
# cd into the repo
cd AVR-2022
# create a Python virtual environment
# You may need to replace `python` here with `python3` or `python3.10`
python -m venv .venv
# activate the virtual environment
source .venv/bin/activate
# install the dependencies
python scripts/install_requirements.py --directory GUI
# run the application
python GUI/app.py

In the future to run the application, you’ll just need to activate the virtual environment first:

cd AVR-2022
source .venv/bin/activate
python GUI/app.py

To deactivate the virtual environment, run:

deactivate

PCC Tester

Before, you launch the application, plug the PCC into your computer with a MicroUSB cable. The application will not recognize anything plugged in after it starts. Now, launch the application. You should be presented with a screen like this:

AVR GUI Home Screen

In the Serial section, select the COM Port your PCC enumerates as. Click “Connect” and the “PCC Tester” should now be enabled (we’ll talk about the other tabs in a later section).

PCC Tester Tab

Click around and try the different buttons, your PCC should light up the LED and move some servos!

If some parts of the PCC work (such as the servos but not LEDs), this is likely a hardware issue. Double check all of your solder connections to make sure they are properly electrically connected and not shorting anything they shouldn’t be.

If nothing on the PCC works:

1. Make sure you selected the right serial port in the GUI. Sometimes phantom COM ports show up on Windows which you will be able to select, and won’t do anything.
2. Make sure your firmware flashed correctly. Follow the steps again and pay close attention.
3. Finally, as stated above, double check all of your solder connections.

10 - Vehicle Management Computer (VMC)

10.1 - Preparing the Jetson

• Unbox your Jetson
• Unbox WiFi Adapter
• Unscrew Jetson top
• Push the tabs out

• Pull out the Jetson Nano Module
• Pull black screw

• Slide in the WiFi card
• Put in black screw
• Slide module back into place
• Replace screws

Micro SD with software pre-installed

Make note of the orientation of the micro SD card in the photo below.

Inserting the micro SD card into the Jetson

11 - Advanced Drone Assembly

Please make sure you’ve successfully built and flown your basic AVR drone. You will be making some extensive modifications to your drone in preparation for advanced assembly.

AVR advanced drone assembly (front)

AVR advanced drone assembly (back)

The modifications for advanced assembly will require some disassembly and the following additions to your drone:

• 3D printed components
  • For mounting various cameras and peripherals
• Power setup for VMC and PCC
  • Power distribution board soldering
  • Y-cable to split power between PDB and ESC
  • Buck converters for powering VMC and PCC
• Telemetry cable
  • For communication between VMC and FC
• Vehicle Management Computer (VMC)
  • Runs AVR code
  • Interfaces with external sensors
  • Provides wireless interface with PX4
• Peripheral Control Computer (PCC)
  • For LED and servo actuation
• ZED Mini Tracking Camera
  • For real-time mapping of the environment
  • For position hold

Block Diagram for the Advanced Drone

11.1 - VMC and PCC Power

Overview

Two main components of your advanced build are the Vehicle Management Computer (VMC), which runs the AVR software stack and the Peripheral Control Computer (PCC), which will allow teams to manually and programmatically control the LED ring, actuate up to four servos, and control the laser.

This section will walk through the necessary steps for providing adequate power to both the VMC and PCC. This will be done with two separate buck converters. The main battery of your AVR drone is 16.8V fully charged. The required input voltage for the VMC and PCC are 5V, therefore the buck converters will step the voltage down to a usable 5V.

Power Wiring Diagram

This section will work its way from the battery out to the VMC & PCC.

Y-Cable

The Y-cable is the cable that splits the battery power into two directions: one for the ESC, and one for the PDB.

To create the wire cables use 3 of the 4 pre-soldered XT60 cables from the kit, 2 females and one male.

XT60 cables

XT60 male (left) and female (right) connectors

Firstly, cut each cable to approximately 2 inches and solder the ends so that they are ready to combine. The end result should look similar to the following.

XT60 cables preparation

Next, place heat shrink large enough to slide over the 3 cable solder joint on the side with 1 male connector. Then, solder the 3 ground (black) cables together. Pull the heat shrink down over the end of the connection and apply heat. If you have access to a heat gun or a lighter this will work well. Alternatively, you can use the side of your soldering iron to apply heat and let the tubing shrink over your connectors.

Soldering XT60 cables

Repeat for the voltage (red) cables.

Soldering XT60 cables

Your finished cable should look like the photo below.

Y cable with 1 male and 2 female connectors

PDB Input Soldering

Before installing the buck converters, the Power Distribution Board (PDB) will need to be soldered correctly. The PDB will allow us to split off power from the battery to each of the buck converters.

The first step is to solder on the battery leads to the PDB. To do this cut 1 male XT60 cable to about 2 inches and tin the ends as we did with the y-cable above.

Tinning male XT60 leads

We recommend watching this video that goes into great detail on soldering. It’s lengthy so at the very least you should scrub through it before attempting to solder the XT60 to the PDB.

You do not want the PDB to slide around while soldering. One of our favorite tricks is to use Blu Tack to hold components in place.

Start the process by tinning the Batt +/- pads as shown in the photos below. A good temperature to aim for is between 750 and 800 degrees Fahrenheit.

Tinning PDB batt +/- pads

Pads tinned and ready for input wires

Place the positive wire onto the positive pad and set the tip of the iron on top. Do not apply too much pressure as you do not want the wire to spread out. The iron should heat both the wire and the pad to form a single solder joint.

Animation of soldering wire to PDB pad

Repeat this process for the negative wire. Your completed PDB will look similar to the one below.

PDB input soldering complete

PDB Output Soldering

In the photo below you will notice two identical buck converters, one for powering the VMC and the other for the PCC. This section will walk through the necessary wiring to supply power to the buck converters.

PDB, wires, and buck converters

Cut approximately 8" of wires; 2 black and 2 red. These will be used to connect each of the buck converters to the PDB. On the opposite end of the PDB there are two sets of pads that we’ll tin for soldering.

Heat the pad using the tip of the soldering iron and feed the solder onto the pad as shown in the photo below.

Soldering the PDB

Once the pads are pre-tinned it should like the following.

Pre-tinned Solder Pads

Next, apply solder to the wires to pre-tin them.

Pre-tinned Wires

After pre-tinning everything, place each lead on the corresponding pad and gently push the soldering iron down. Like we did with the XT60 connector we want to make sure to apply heat long enough for the solder on the pad and wire to join.

Soldering wires to pads

Repeat this process for the other two wires. After successfully soldering the positive and negative wires to the PDB, use a multimeter to run a continuity test. This will ensure that there are no shorts between the positive and negative terminals.

Checking connections

You should now be at a place where you have the PDB soldered as shown in the following photo.

Power Distribution Layout

Finally, place the PDB on top of the ESC standoffs and secure using M2.5 nuts from your AVR kit.

Mounting the PDB

11.2 - Buck Converter Mounting

Overview

Wire management is an important part of any drone build. It will make your build easier to maintain, look professional, and keep wires from potentially getting caught in your drone’s propellers. In the previous section we pre-soldered the VMC/PCC power wires and mounted the PDB. Now we will focus on wiring and mounting the buck converters.

The power wires from the PDB will be run through the mid-plate assembly to the front of the AVR drone. This is necessary to make sure the wires do not interfere with battery mounting, which we’ll cover in an upcoming section.

Wiring

The PDB and ESC are both mounted near the right rear of the frame. The buck converters will be mounted near the front of the frame. This means we need to run the cables up through the mid-plate assembly and drop them down in the front of the frame.

Feed the wires into the mid-plate assembly and zip tie them to the mid-bottom plate as shown in the photo below. Securing these wires is important as you don’t want them to interfere with battery mounting.

VMC and PCC power leads run through mid-plate assembly

Drop the wires down through the two large oval cutouts in the mid-bottom plate as shown in the photo below.

VMC and power leads ready to connect to buck converters

Mounting

We will mount the buck converters using the 3M double-sided tape provided in your AVR kit. The solder joints on the bottom of the buck converters stick out a good bit so we will double-stack tape on each end. The reason for this is that we do not want to the solder joints to accidentally make contact with the carbon fiber plate. This could lead to a short circuit. Cut one of the 3M squares into four pieces as shown in the photo below.

3m tape cut into four squares

Double stack the tape on each end of the buck converter as shown in the photo below. Repeat the process for the other buck converter.

Double stacked 3M tape on buck converter

Before securing the buck converters to the AVR frame we will connect the input leads to the screw terminals on each buck converter as shown below.

Power wires connected to buck converter terminals

Take the remaining 18 gauge wire (the wire you used to supply input power from the PDB to each buck converter) and connect it to the output terminals on the PCC buck converter. The PCC buck converter will be on the left side as drone is facing you. You can see the output wires on the left side of the photo below.

PCC buck converter with output wires on left and input wires on right

VMC power is supplied with a barrel plug. Find the cable with the barrel plug in your kit and cut it to 8". Remove the shielding and expose about 1/8" from the positive and negative wires as shown in the photo below.

Prepping power cable for VMC

Connect the positive and negative leads to the output terminals on the VMC buck converter. Once again, screw down tightly on the terminals so that the wires do not come loose.

VMC buck converter wired up with barrel plug

Stick the PCC buck converter on the left side of the bottom mid-plate and the VMC buck converter on the right (as the front of the drone is facing you). Place each buck converter at a 45 degree angle with the output leads pointed towards each side of the frame. The photo below shows the PCC leads on the left side of the frame and the VMC barrel plug on the right.

Buck converters mounted at 45 degree angle

The photo below shows the right side of the frame and clearance for the battery to slide into the tray. The PCC will be mounted and powered from this side of the frame.

Right side battery clearance

The photo below shows the left side of the frame where the battery can slide into place without any obstruction from the buck converters. The barrel plug hangs off this side of the frame and will be used to power the VMC.

Left side battery clearance

Take a quick look at the wiring orientation from a top down perspective. In the next section we will build the top plate assembly and install it over the FC.

Top down view of power wires for VMC and PCC

11.3 - FC ⟷ VMC Telemetry Cable

Overview

It’s important that the FC and VMC can communicate with each other. This bi-directional communication will allow us to receive telemetry data from the FC and send data to it from the VMC. If you recall, before we communicated with the FC using a micro-USB cable connected to a PC running QGroundControl. What you will be able to do now is communicate over a WiFi network, which will make this process easier.

In addition to a wireless link between the AVR drone and QGC you will learn how to configure position hold capabilities using external cameras. You may have noticed with the basic drone that the drone required constant input from the pilot to maintain position in stabilized flight mode. With the assistance of these cameras you will be able to hover in position mode with ease! The cable we build in this section makes this all possible.

Locate the following components in the photo below:

• 6 pin cable from the Pixhawk box
• 40 pin connector housing
• 3 female to female wires (black, purple, and grey)

Necessary components for telemetry cable

Creating the Cable

Before we start building the telemetry cable let’s take a quick look at the following wiring diagram. The middle area represents the 40 pin connector housing. Pay attention to the pinout from the connector housing to the TELEM1 port on the Pixhawk FC. We will be using the following pins:

• Pin 2 - TX - Grey
• Pin 3 - RX - Purple
• Pin 6 - GND - Black

VMC pinout

Using tweezers you will remove pins 1, 4, and 5 from the Pixhawk connector. This is done by prying the plastic tab for each pin as shown in the photo below.

Removing pin 1 from the telemetry connector

The photo below shows only the necessary pins remaining: pin 2, 3, and 6 from left to right.

Telemetry wires: TX, RX, and GND

Clip the connector from the other end of the Pixhawk cable. Cut all three of the individual female-female wires to approximately 2-3". Strip 1/2" of shielding away from all wires as shown in the photo below.

Wire prep for soldering

Prior to soldering make sure each colored wire matches the corresponding pin. The photo below shows one final check before soldering.

Confirming layout before soldering

Join the wires using the “Twisted Helix” method we covered in the ESC wiring during basic assembly.

Joining wires prior to soldering

Solder all three wires and apply heat shrink.

Telemetry cable with all three wires soldered

Remove the plastic connectors from the grey, purple, and black wires.

Plastic connectors removed

Insert all three wires into the 40 pin connector housing as shown in the following photos. If you’re uncertain where to insert the wires refer back to the diagram in the overview section.

Make sure you hear each of the pins click into the connector housing. Inserting them properly into the housing will prevent them from accidentally getting pulled out.

Adding telemetry wires to 40 pin connector

Now that your telemetry cable is complete you can do a test fit. Pay attention to the orientation of the 40 pin connector as seen in the photo below.

Telemetry cable connected to VMC and Pixhawk TELEM1 port

11.4 - Top Accessory Plate Assembly

Overview

In this section we will cover mounting the VMC and PCC to the top accessory plate followed by attaching the plate over the FC. Locate the ziploc bag of 2.5mm nylon hardware. We will be using the 6mm nylon standoffs, bolts, and nuts. Make note of the four holes around the larger cutout on the left. This is where we will mount the VMC. In addition, make note of the four holes around the smaller cutout on the right. This is where we will mount the PCC.

VMC, PCC, top assembly plate, and nylon hardware

Start by placing the 6mm standoffs facing down through the mounting holes in the top plate. Use a 2.5mm nut to secure each of the standoffs.

Installing 6mm standoffs

The photo below shows the completed standoff installation.

6mm standoffs in place for VMC and PCC mounting

VMC Mounting

We will now mount the VMC to the top accessory plate. The VMC is the “brains” behind your AVR drone build and will be responsible for running the Bell software stack during testing and on competition day.

With the standoffs secured into the top accessory plate the next step is to attach the VMC. These standoffs will provide enough clearance for the VMC so that the solder joints beneath do not make contact with the carbon fiber plate. Carbon fiber is conductive, which means that it can cause your board to short out if two leads touch the plate.

Align all four of the VMC mounting holes over the 6mm standoffs and secure into place with the nylon bolts. The VMC will be mounted on the left of the top accessory plate with the USB ports facing out.

Securing nylon bolts for VMC mounting

The orientation of your top plate and VMC should look identical to the photo below.

VMC mounted to top accessory plate

VMC Cooling Fan

During advanced testing you will be running the AVR software stack on your VMC. Since we make extensive use of the VMC’s CPU and GPU it can heat up significantly. It’s important to keep your VMC cool and in this section you will install a cooling fan onto the top of the VMC heat sink.

There are two nuts and bolts included in a small ziploc bag with your cooling fan. Place your cooling fan on top of the heat sink and insert two bolts, on opposite corners, through the fan and the heat sink.

Cooling fan with bolts on opposite corners

A small drop of Loctite applied to cooling fan nut

Use needle nose pliers to hold the nut in place and screw the bolt from the top using a Phillips head screwdriver.

Securing the cooling fan with screwdriver and pliers

Repeat the process for the other nut and bolt. Attach the fan’s power cable to the VMC as shown in the photo below.

Cooling fan connected to power port

PCC Mounting

Let’s proceed with mounting the PCC to the top accessory plate. Make note of the photo below and that the micro USB port is facing outward.

PCC USB port must face outward

We will secure the PCC with four nylon bolts. The easiest way to do this is to remove the top and bottom PCC boards as shown in the photo below.

Securing PCC with four nylon bolts

Replace the boards back into the PCC and mounting is complete!

PCC mounting complete

Top Accessory Plate Mounting

Before we can place the top accessory plate onto the drone we must screw the antenna connectors into place. Run the VMC and PCC cables through the bottom of the plate as shown in the photo below.

Cable management for top accessory plate

With the VMC and PCC attached to the top accessory plate and wires routed let’s proceed with mounting the plate over the FC using 40mm standoffs and 10mm M3 screws.

Hardware for accessory plate mounting

Place blue Loctite on one of the 10mm screws.

10mm mounting screw with Loctite

There are four access holes in each corner of the bottom mid-plate, close to where you mounted the 3D printed landing gear. Use a long hex driver to feed the screw up through the bottom accessory plate and through the mid-plate assembly.

Feeding screw through bottom mid-plate

Another option is to use a short L-shaped hex key to feed the screw into the hole.

Using hex key to feed screw through bottom mid-plate

Hand tighten the 40mm standoff onto the screw.

Placing 40mm onto 10mm screw

Securely fasten the standoff and repeat the process for the other three standoffs.

Top accessory plate standoff securely fastened

Connect the telemetry cable from the VMC to the TELEM1 port on the FC.

Telemetry cable connected to TELEM1 on FC

Use four 10mm screws to mount the top accessory plate onto the standoffs. Do not forget to use blue Loctite on each of the screws.

Securing top accessory plate on standoffs

Top accessory plate secured

Wiring

Connect the barrel plug from the VMC buck converter to the VMC power input.

VMC ready to be powered with the barrel plug

Finally, cut the positive and negative wires from the PCC buck converter to length. Trim 1/8" of shielding from the wires and connect them to the PCC power terminals as shown in the photo below.

PCC power leads connected

11.5 - Zed Mini Camera Mounting

The ZED Mini will be mounted to the front of your AVR drone and connected with a USB-C cable. This camera is instrumental in mapping out the environment in real-time and providing location updates to the VMC. This enables your AVR to “see” and maintain it’s current position without GPS!

You should have printed the Zed Mini mount from the 3D Printing section of this documentation. The ZED Mini should clip into your 3D printed mount securely.

Hardware for mounting ZED Mini

Secure the camera mount to the bottom accessory plate with two M3 8mm screws and lock nuts.

ZED Mini 3D printed camera mount

You will notice that the mount points 45 degrees downward. This aids in tracking both in front and beneath the AVR drone.

45 degree downward tilt

Snap the ZED Mini into the mount. Make sure that the ridges in the mount snap into the recessed areas on the top and bottom of the camera. You should not be able to slide the camera left and right when properly secured.

ZED Mini snapped into mount

Locate the large ziploc bag inside the AVR Drone Peripherals box. Inside this bag there are several screws floating around. You will need two of them that look like the ones in the photo below.

Set screws for securing ZED Mini into the mount

Use a Phillips head screwdriver to thread both screws into the 3D printed mount.

Wiggle the camera left and right to see if there is any play. If so, turn the set screws half a rotation. Repeat the process until the camera is fully secured.

Set screws hold ZED Mini in place

Finally, you can plug the USB cable into the side of the Zed Mini and into one of the ports on the VMC.

The Zed Mini has a unique USB-C cable so unfortunately it is going to be a little longer than you need. We suggest rolling the cable up and tucking it between the bottom and bottom-mid plate for cleanliness.

ZED Mini cable rolled out and zip-tied to standoffs

ZED Mini plugged into one of the VMC’s USB ports

11.6 - Assembly Review

Great job! Please take a few minutes to watch the video below and review all that we covered during the advanced hardware modifications.

12 - Checkpoint 2: Stabilized Flight Test

Please be sure to watch the video below to understand what to expect from the advanced flight test. This will be done in stabilized flight mode just like we did in the basic flight test.

13 - Software

13.1 - Flashing the SD Card

First, you need to download the Jetson’s operating system. A custom image with a baseline AVR software can be found here avr23.zip. This is a large file, so it will take a while.

After the .zip file finishes downloading, extract this file, and plug in your microSD card.

Windows

To flash the SD card on Windows, we recommend a tool called Rufus. Go to this page and download the rufus-<version>.exe file.

Download this installer file

Go ahead and launch Rufus. When you launch the application, it should look something like this:

Rufus main window

1. Make sure the correct device is selected. If your microSD card is not blank, it will probably have a different label.
2. Select the .img file in the folder you extracted.

You will now be able to click the “START” button in Rufus. Go ahead and click this. You will get a number of warnings that you’re about to format and wipe this microSD card.

Rufus warnings

Go ahead and click through all of these, you know what you’re doing. Rufus will begin flashing the microSD card and at the end will let you know when it’s finished.

MacOS/Linux

To flash the SD card on MacOS or Linux, we recommend using Balena Etcher. Go to their website and follow the instructions to download and install Balena Etcher.

Go ahead and launch Balena Etcher. Select the .img file in the folder you extracted, and select your microSD card.

Options selected in Balena Etcher

Once you hit “Flash”, you may be prompted to enter your password for super user privileges.

Enter your account credentials

Balena Etcher will begin flashing the microSD card and at the end will let you know when it’s finished.

13.2 - Connecting to the Jetson

You’ll need to login to your Jetson many times to setup and run software. Out of the box, your Jetson will have a default user account called avr with a password of bellavr22.

Here are 3 possible methods you can use.

Monitor and Keyboard

Possibly the simplest way to connect to your Jetson is with a monitor and keyboard. You’ll just need a monitor that has HDMI or DisplayPort that you can plug in to the Jetson.

Once at the desktop, you can open a terminal by clicking the application launcher in the bottom left (the 9 squares) or with the keyboard shortcut Ctrl+Alt+t.

Serial

If you do not have a monitor and keyboard, another method of logging in to your Jetson is over a serial connection. To do this, you’ll need a serial client.

Installing Serial Client

Installing Serial Client on Windows

For Windows, we recommend PuTTy. Go to this page and download and install the putty-64bit-<version>-installer.msi file.

Download this installer file

Run through the setup wizard

Installing Serial Client on MacOS

Rather than using PuTTy, it’s much easier to open a terminal and simply run:

screen ttyACM0 115200

Installing Serial Client on Linux

You can follow the same steps as on MacOS (after installing screen with sudo apt install screen), but if you like a GUI, you can install PuTTy with:

sudo apt install putty

and launch PuTTy with:

sudo putty

Connecting to Jetson via Serial Client

Now, if you want to power the Jetson via USB (if the Jetson is not connected to a wall adapter or a battery) remove the jumper behind the barrel jack.

Plug in a MicroUSB cable to the Jetson,

and then into your computer.

Open up PuTTy, choose the COM port or the serial device /dev/ttyACM0 for the Serial line, and put in 115200 as speed.

Click “Open”. You should now see the Jetson’s terminal.

SSH

In the future, you’ll want to use SSH to login to your Jetson, as it is far more convenient. SSH is way to login to a Linux system over a network. However, to do so, you’ll need to know the IP address of your Jetson. The simplest way to figure this out if you don’t know is to login via serial, and then run the command

ifconfig eth0

if you’ve connected the Jetson to ethernet or

ifconfig wlan0

if you’ve connected the Jetson to WiFi.

If you have yet to connect your jetson to the WiFi you can follow instructions for connecting to internet prior to returning to connect through ssh.

ssh Command

The quickest way to login to yor Jetson over SSH, is to use the builtin ssh command in Windows. Open up a command prompt or PowerShell, and run

ssh <user>@<ip>

The first time you log in to your Jetson, you’ll be prompted to accept the host’s key. Enter yes. You’ll thenbe prompted for your password, and then you’ll be put into a terminal.

Command line SSH login

PuTTy

If you’re not comfortable with the command line, you can install PuTTy to connect over SSH. Select the “SSH” button in PuTTy, put in the hostname field <user>@<ip> and then click the “Open” button.

PuTTy SSH Login

Secondary popup window

You’ll need to accept that you trust a key the first time.

Accept the key

SSH Troubleshooting

Connection closed/reset

If you try to SSH into your Jetson, and you immediately get a connection timed out error, here’s how to fix it.

First, login to your Jetson via serial. Run the command

tail /var/log/auth.log

and see that you’re getting errors about invalid formats:

Jun 28 18:42:26 drone sshd[8547]: error: key_load_private: invalid format
Jun 28 18:42:26 drone sshd[8547]: error: key_load_public: invalid format
Jun 28 18:42:26 drone sshd[8547]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Jun 28 18:42:26 drone sshd[8547]: error: key_load_private: invalid format
Jun 28 18:42:26 drone sshd[8547]: error: key_load_public: invalid format
Jun 28 18:42:26 drone sshd[8547]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
Jun 28 18:42:26 drone sshd[8547]: fatal: No supported key exchange algorithms [preauth]

If so, run the command

sudo /usr/bin/ssh-keygen -A

to generate a new host key.

13.3 - Updating VMC Software

Connecting to Internet

In order to install the AVR software, your Jetson needs to have an internet connection. The easiest way by far is if you have ethernet available. If so, just plug an ethernet cable into your Jetson and you should be good to go.

If you don’t have ethernet, you can use a WiFi connection. First, you can list the available networks with:

nmcli device wifi list

Example:

WiFi network list

Hit q to exit the list.

If the Jetson is already connected to a WiFi network, you can disconnect it with:

sudo nmcli device disconnect wlan0

To connect to a WiFi network, run:

# with a password
sudo nmcli device wifi connect <network name> password <password>

# without a password
sudo nmcli device wifi connect <network name>

such as:

sudo nmcli device wifi connect "WI do drones FI" password "Flying_Is_Fun"

If your network name or password has a space or other special characters, you’ll need to wrap it in quotes as shown above.

Updating

Bell engineers are constantly working on improving the VMC software. If a new version is ever available, you just need to go into the directory the repo is cloned to, pull the latest code, and re-run the setup script:

cd ~/AVR-2022/VMC/scripts
git pull
./setup.py

The setup.py script is safe to run at any time, it won’t mess anything up by running it after everything is already configured.

Troubleshooting

Release is not valid yet

Example output:

Get:1 file:/var/cuda-repo-l4t-10-2-local  InRelease
Ign:1 file:/var/cuda-repo-l4t-10-2-local  InRelease
Get:2 file:/var/visionworks-repo  InRelease
Ign:2 file:/var/visionworks-repo  InRelease
Get:3 file:/var/visionworks-sfm-repo  InRelease
Ign:3 file:/var/visionworks-sfm-repo  InRelease
Get:4 file:/var/visionworks-tracking-repo  InRelease
Ign:4 file:/var/visionworks-tracking-repo  InRelease
Get:5 file:/var/cuda-repo-l4t-10-2-local  Release [564 B]
Get:6 file:/var/visionworks-repo  Release [2,001 B]
Get:7 file:/var/visionworks-sfm-repo  Release [2,005 B]
Get:5 file:/var/cuda-repo-l4t-10-2-local  Release [564 B]
Get:8 file:/var/visionworks-tracking-repo  Release [2,010 B]
Ign:9 https://repo.download.nvidia.com/jetson/common r32.7 InRelease
Get:6 file:/var/visionworks-repo  Release [2,001 B]
Get:7 file:/var/visionworks-sfm-repo  Release [2,005 B]
Get:8 file:/var/visionworks-tracking-repo  Release [2,010 B]
Ign:10 https://repo.download.nvidia.com/jetson/t210 r32.7 InRelease
Err:11 https://repo.download.nvidia.com/jetson/common r32.7 Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses not yet valid certificate.  Could not handshake: Error in the certificate verification. [IP: 23.221.220.78 443]
Err:12 https://repo.download.nvidia.com/jetson/t210 r32.7 Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses not yet valid certificate.  Could not handshake: Error in the certificate verification. [IP: 23.221.220.78 443]
Hit:13 http://ports.ubuntu.com/ubuntu-ports bionic InRelease
Get:15 http://ports.ubuntu.com/ubuntu-ports bionic-updates InRelease [88.7 kB]
Hit:18 http://ports.ubuntu.com/ubuntu-ports bionic-backports InRelease
Hit:19 http://ports.ubuntu.com/ubuntu-ports bionic-security InRelease
Reading package lists... Done
E: The repository 'https://repo.download.nvidia.com/jetson/common r32.7 Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'https://repo.download.nvidia.com/jetson/t210 r32.7 Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Release file for file:///var/cuda-repo-l4t-10-2-local/Release is not valid yet (invalid for another 2259d 1h 0min 15s). Updates for this repository will not be applied.
E: Release file for file:///var/visionworks-repo/Release is not valid yet (invalid for another 1888d 8h 9min 54s). Updates for this repository will not be applied.
E: Release file for file:///var/visionworks-sfm-repo/Release is not valid yet (invalid for another 1869d 23h 29min 17s). Updates for this repository will not be applied.
E: Release file for file:///var/visionworks-tracking-repo/Release is not valid yet (invalid for another 1869d 23h 30min 39s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/bionic/InRelease is not valid yet (invalid for another 1218d 5h 2min 38s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/bionic-updates/InRelease is not valid yet (invalid for another 2728d 6h 14min 58s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/bionic-backports/InRelease is not valid yet (invalid for another 2728d 5h 42min 43s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/bionic-security/InRelease is not valid yet (invalid for another 2728d 5h 39min 48s). Updates for this repository will not be applied.

This usually means your system’s time is not correct. Try running the following commands to force your system to correct its time.

# After each attempt, run the `date` command to check the time to see if it worked

# Option 1:
sudo hwclock --hctosys

# Option 2:
sudo timedatectl set-ntp off
sudo timedatectl set-ntp on

# Option 3:
sudo service systemd-timesyncd restart

# Option 4:
# This is a final brute-force option that is not recommended.
# Substitute in the date and time you're running the command at
sudo date -s '2022-12-25 12:34:56'

ZED camera not detected

Example output:

WARNING: ZED camera not detected, skipping settings download

Obviously, make sure your ZED Mini camera is plugged in to the Jetson. If not, plug it in and re-run the setup script.

However, if it is, this sometimes happens because of a finnicky USB detection. Try running the setup script once or twice more, and unplug the camera and plug it back in until it picks it up and works.

Connection Issues

Example output:

Get:1 file:/var/cuda-repo-l4t-10-2-local  InRelease
Ign:1 file:/var/cuda-repo-l4t-10-2-local  InRelease
Get:2 file:/var/visionworks-repo  InRelease
Ign:2 file:/var/visionworks-repo  InRelease
Get:3 file:/var/visionworks-sfm-repo  InRelease
Ign:3 file:/var/visionworks-sfm-repo  InRelease
Get:4 file:/var/visionworks-tracking-repo  InRelease
Ign:4 file:/var/visionworks-tracking-repo  InRelease
Get:5 file:/var/cuda-repo-l4t-10-2-local  Release [564 B]
Err:6 http://ports.ubuntu.com/ubuntu-ports bionic InRelease
  Could not connect to ports.ubuntu.com:80 (0.0.0.0). - connect (111: Connection refused)
Err:7 http://ports.ubuntu.com/ubuntu-ports bionic-updates InRelease
  Unable to connect to ports.ubuntu.com:http:
Err:8 http://ports.ubuntu.com/ubuntu-ports bionic-backports InRelease
  Unable to connect to ports.ubuntu.com:http:
Err:9 http://ports.ubuntu.com/ubuntu-ports bionic-security InRelease
  Unable to connect to ports.ubuntu.com:http:
Get:10 file:/var/visionworks-repo  Release [2,001 B]
Get:11 file:/var/visionworks-sfm-repo  Release [2,005 B]
Get:5 file:/var/cuda-repo-l4t-10-2-local  Release [564 B]
Get:12 file:/var/visionworks-tracking-repo  Release [2,010 B]
Get:10 file:/var/visionworks-repo  Release [2,001 B]
Get:11 file:/var/visionworks-sfm-repo  Release [2,005 B]
Get:12 file:/var/visionworks-tracking-repo  Release [2,010 B]
Hit:13 https://repo.download.nvidia.com/jetson/common r32.7 InRelease
Get:14 https://repo.download.nvidia.com/jetson/t210 r32.7 InRelease [2,550 B]
Fetched 2,550 B in 1s (1,843 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/bionic/InRelease  Could not connect to ports.ubuntu.com:80 (0.0.0.0). - connect (111: Connection refused)
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/bionic-updates/InRelease  Unable to connect to ports.ubuntu.com:http:
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/bionic-backports/InRelease  Unable to connect to ports.ubuntu.com:http:
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/bionic-security/InRelease  Unable to connect to ports.ubuntu.com:http:
W: Some index files failed to download. They have been ignored, or old ones used instead.

If the setup script fails to download something, it likely lost connection to the internet, or your network is blocking a site it tried to download content from. Try running the script again.

If that still does not work, look at the VMC software README at https://github.com/bellflight/AVR-2022/tree/main/VMC/README.md and the provided list of domain names that the setup script connects to. Either see if your network administrator can allow these domain names, or use a personal hotspot or internet connection.

13.4 - Running VMC Software

Networking

Before running the VMC software, we highly recommend that you configure the Jetson to act as it’s own WiFi network you can connect to. To do this, login to the Jetson, go into the “VMC” directory, and run the command ./scripts/wifi.py create:

cd ~/AVR-2022/VMC/
./scripts/wifi.py create

This will walk you through creating a WiFi network that you can connect to.

WiFi setup wizard

After connecting to the WiFi network, your Jetson will always have the IP address 10.42.0.1, which you can use to connect to via SSH.

Running

After connecting to your Jetson via the hotspot, go into the “VMC” directory, and run the command ./start.py run:

cd ~/AVR-2022/VMC/
./start.py run

To shutdown the software, press Ctrl+C in the console window you started the software in. Additionally, run

./start.py stop

for good measure.

Options

With the basics out of the way, there are some options that can be used to control which parts of the software are run. By default, a normal set of modules are run:

./start.py run
# also equivalent to
./start.py run --norm
./start.py run -n

• fcm
• fusion
• mavp2p
• mqtt
• vio
• apriltag
• pcm
• status
• thermal

However, let’s say you have just the bare minimum equipment installed on your drone (just the ZED Mini camera). You can use the --min option to run only the following modules which are the bare minimum required for flight:

./start.py run --min
# also equivalent to
./start.py run -m

• fcm
• fusion
• mavp2p
• mqtt
• vio

On the other hand, if you have everything installed, and also want to run your own code in the sandbox module you can use the --all option:

./start.py run --all
# also equivalent to
./start.py run -a

• fcm
• fusion
• mavp2p
• mqtt
• vio
• apriltag
• pcm
• status
• thermal
• sandbox

Lastly, if you want to run modules not defined in a preset here, you can either list them all out explicitly, or add the additional modules you want to an exisiting alias:

# the following are equivalent
./start.py run pcm --min # the --min must come at the end
./start.py run fcm vio mqtt mavp2p fusion pcm

If you ever need help, just add the --help argument to the command:

usage: start.py [-h] [-l] [-m | -n | -a] {run,build,pull,stop} [modules ...]

positional arguments:
  {run,build,pull,stop}
                        Action to perform
  modules               Explicitly list which module(s) to perform the action one

optional arguments:
  -h, --help            show this help message and exit
  -l, --local           Build containers locally rather than using pre-built ones from GitHub
  -m, --min             Perform action on minimal modules (fcm, fusion, mavp2p, mqtt, vio). Adds to any modules explicitly specified.
  -n, --norm            Perform action on normal modules (apriltag, fcm, fusion, mavp2p, mqtt, pcm, status, thermal, vio). Adds to any modules explicitly specified. If nothing else is specified, this
                        is the default.
  -a, --all             Perform action on all modules (apriltag, fcm, fusion, mavp2p, mqtt, pcm, sandbox, status, thermal, vio). Adds to any modules explicitly specified.

Troubleshooting

Sometimes when starting the AVR software, things don’t all start correctly.

Cannot start service pcm

Example output:

Needing sudo privileges to run docker, re-launching
Running command: docker-compose --project-name AVR-2022 --file /tmp/docker-compose-v5eqlg13.yml up --remove-orphans --force-recreate pcm
/usr/local/lib/python3.6/dist-packages/paramiko/transport.py:33: CryptographyDeprecationWarning: Python 3.6 is no longer supported by the Python core team. Therefore, support for it is deprecated in cryptography and will be removed in a future release.
  from cryptography.hazmat.backends import default_backend
Creating network "avr-2022_default" with the default driver
Creating avr-2022_mqtt_1 ... done
Creating avr-2022_pcm_1  ... error

ERROR: for avr-2022_pcm_1  Cannot start service pcm: error gathering device information while adding custom device "/dev/ttyACM0": no such file or directory

ERROR: for pcm  Cannot start service pcm: error gathering device information while adding custom device "/dev/ttyACM0": no such file or directory
ERROR: Encountered errors while bringing up the project.

This error means that the AVR software was unable to connect to the PCC. If you are not using the PCC, follow the steps above to disable that module.

Otherwise, to test that the PCC is correctly connected to the VMC, run the command:

ls /dev/ttyACM0

You’ll get the message ls: cannot access '/dev/ttyACM0': No such file or directory if the PCC is not connected. If the PCC is connected, /dev/ttyACM0 will get echoed back. Try unplugging the PCC and plugging it back into the VMC.

13.5 - Connecting QGC

Once you have the VMC software running on your drone, you’ll want to connect QGroundControl to it. While not strictly required for anything, it helps with keeping an eye on the battery percentage remaining, and ensuring the correct flight mode is selected.

Open QGroundControl, click on the purple “Q” in the top left, then go to “Application Settings”. Now, go to “Comm Links” and then click “Add” at the bottom.

Now, enter a name for this connection, select type of “TCP”, enter the IP address of your drone, and leave the port number to the default of 5760. Click “Ok” to add it.

Now whenever you want to connect QGC to your done, go back to “Application Settings”, “Comm Links”, select your connection, and click “Connect” at the bottom.

Go back to the main QGC screen and you should see your drone at the Bell headquarters with 13 satellites visible.

13.6 - Flight Controller Parameters

After configuring the AVR software on your Jetson, you need to also load custom parameters into your flight controller as well. These settings configure how the flight controller processes sensor input, and we need to tell it to unconditionally trust the data the AVR software feeds it.

First, download this parameter file from GitHub: https://github.com/bellflight/AVR-2022/blob/main/PX4/Params/AVR2022Params.params

The easiest way to download the file is to click the “Raw” button, then right-click the page, and select “Save page as”.

The location of the “Raw” button

Like flashing the flight controller firmware, you’ll need to plug in the FC to your computer with the MicroUSB cable.

Now, open QGroundControl, click the “Q” in the top left, then “Vehicle Setup” then “Parameters” at the bottom of the list.

Click on “Tools” in the top right then select “Load from file…” and select the AVR parameter file you downloaded.

Then click “Ok” to load the parameters.

Then click “Ok” a bunch of times as QGroundControl informs you that many parameter changes requires a vehicle reboot.

Then go back to “Tools” and select “Reboot Vehicle” at the bottom of the list to restart the flight controller for the parameters to take effect.

13.7 - GUI

Setup

You should have already setup the AVR GUI when testing your PCC here.

Usage

Open the application. You’ll be brought to the Connections tab. After starting the AVR software on your Jetson, put in the Jetson’s IP address under the “MQTT” section. Leave the port as is.

Connections tab

Click “Connect”, and make sure the application properly connects.

Connection state

If the application is unable to connect to your drone, the state will show as “Failure”. Make sure the software is running, and you got the IP address correct.

After the application connects, all the VMC-related tabs will become enabled.

Tabs

The functionality of the application is broken up into multiple tabs. These tabs are automatically enabled/disabled based on the connectivity currently available. These tabs can be re-ordered as desired. Additionally, the tabs can be popped out into separate windows to create a multi-pane view, either by double clicking the tab, or right-clicking and selecting “Pop out”.

You can also double-click to pop out a tab

To reattach a tab, just close the window.

Re-attaching a tab

VMC Telemetry

VMC Telemetry Tab

This tab is a sort of QGroundControl “Lite” that shows the most important telemetry information from the drone. This is NOT a full replacement for QGroundControl, but quick view of important information while your drone is flying.

At the top is the status of the flight controller, with information about the current GPS fix, battery level and voltage, armed status, and selected flight mode.

In the middle is the current location of the drone in local and global coordinates, along with the current attitude of the drone in roll, pitch, yaw.

Finally, at the bottom is a display of the status of the software modules required for stabilized flight and April Tag detection. These indicators will turn green once MQTT messages are received from a module, and will turn red if more than a second has elapsed since the last received message.

Module status indicators

If all 4 indicators are green, you are good to fly!

VMC Control

VMC Control Tab

This tab allows you to control various aspects of the drone, including the LEDs, and servos connected to the PCC.

Click the individual open/close buttons to open/close individual servos, or click the open/close all buttons at the top of open/close all of the servos at once.

Click the color buttons to change the color of the LEDs to one of the presets (red, green, blue). The “clear” button at the bottom turns off the LEDs.

Autonomy Control

Autonomy Control Tab

Autonomous Enable

The “Autonomous” buttons in the tab, this is purely optional for the teams that have chosen to write autonomous code. These buttons send a message to the MQTT topic avr/autonomous with a payload of:

// enable button
{
    "enable": true,
}

// disable button
{
    "enable": false,
}

For any teams writing their own autonomous code, they can write a listener for this topic to enable/disable their autonomous code at certain points, rather than have it run continuously the entire time.

Example implementation:

from bell.avr.mqtt.client import MQTTModule
from bell.avr.mqtt.payloads import AvrAutonomousPayload

class Sandbox(MQTTModule):
    def __init__(self) -> None:
        self.enabled = False
        self.topic_map = {"avr/autonomous": self.on_autonomous_message}

    ...

    def on_autonomous_message(self, payload: AvrAutonomousPayload) -> None:
        self.enabled = payload["enable"]

    def autonomous_code(self) -> None:
        while self.enabled:
            do_stuff()

Building Autonomous Enable Drop

Additionally, buttons for enabling/disabling autonomous water drops are provided on this page. These buttons send a message to the MQTT topic avr/autonomous/building/drop with a payload of:

{
  "id": 0,
  "enabled": true
}

This message can be used to tell you drone what buildings are on fire and if you want to drop water on it or not. For a full list of which buildings have water drops please refer to the game manual. The activity of using the avr/autonomous/building/drop will be implemented by the students in the sadbox module. [Hint: the above example can also be used in this scenario]

Thermal View/Control

Thermal view and control tab

This tab shows a view of the thermal camera, and provides a means of controlling the gimbal and turning the associated laser on and off.

You can either calibrate your thermal cameras range manual by typing in a min and max value, or you can use the auto calibrate feature to get a dynamic range.

To use the gimbal, click and drag the black dot and move it around within the box. The bounds of the box are the gimbal’s limit.

Moving Map

Moving Map Tag

A map of your drones movements has been included for reference while flying. You can use this to reference your location, roll, pitch, yaw, or altitude.

MQTT Debugger

MQTT Debugger Tab

This tab is a debugging tool that shows all MQTT messages that are passing through the AVR software, along with giving you the ability to manually send messages.

In the top half of the tab is the message viewer. On the left side is a tree view of all the topics with the levels deonting “/“s in the topic name. When you click on a topic, on the right side will show the last payload recieved on that topic, and will update live.

Viewing live data from a topic

To show or hide topics, click the arrow on the left of the trip item to expand or hide the next level, or right-click the topic and select “Expand Children” or “Collapse Children”. To expand or collapse everything, select “Expand All” or “Collapse All”.

Expanding or collapsing child topics

At the bottom of the viewer is a “Running”/“Paused” button that will cause the viewer to update live, or freeze the current view. This is not associated with the MQTT connection in the Connections tabs. This only stops the viewer from updating when trying to look at data.

Running/paused button

In the bottom half of the tab is the message sender. You can put in the topic you want to send a message to and the payload of the message. Click the “Send” button at the bottom to send the message, and you will see it show up above in the message viewer.

Message sender

If you want to copy an existing message, right-click on an item in the message viewer and select “Preload data”. This will prefill the topic and payload of the message into the message sender.

Preload data option

Alternatively, you can select “Copy Topic” or “Copy Payload” to copy the topic or payload to your clipboard.

MQTT Logger

MQTT Logger tab

This tab is another debugging tool, that can be used to create a log of MQTT data that can be analyzed at a later time.

Clicking the “Record” button at the bottom will create a folder called “logs” next to the .exe and create a new log file with the starting timestamp in the name. The log file is just a .csv file with 3 columns:

1. Timestamp that the message was sent
2. Topic of the message
3. Payload of the message (JSON data as a string)

Short example:

Timestamp,Topic,Payload
2022-05-15T16:05:21.861220,avr/fcm/location/local,"{""dX"": -2.5455074310302734, ""dY"": -1.5015729665756226, ""dZ"": 2.0492169857025146, ""timestamp"": ""2022-05-15T18:43:51.529153""}"
2022-05-15T16:05:21.865960,avr/fcm/attitude/euler,"{""roll"": 0.3597148656845093, ""pitch"": -1.1968730688095093, ""yaw"": -115.29061126708984, ""timestamp"": ""2022-05-15T18:43:51.533150""}"
2022-05-15T16:05:21.867091,avr/fcm/location/global,"{""lat"": 32.8085261, ""lon"": -97.1563602, ""alt"": -0.1720000058412552, ""hdg"": -6245.665443087664, ""timestamp"": ""2022-05-15T18:43:51.534187""}"
2022-05-15T16:05:21.867533,avr/fcm/velocity,"{""vX"": 0.009999999776482582, ""vY"": 0.0, ""vZ"": -0.009999999776482582, ""timestamp"": ""2022-05-15T18:43:51.535720""}"
2022-05-15T16:05:21.886569,avr/fusion/hil_gps,"{""time_usec"": 1652640231557357, ""fix_type"": 3, ""lat"": 328085260, ""lon"": -971563603, ""alt"": 165206, ""eph"": 20, ""epv"": 5, ""vel"": 0, ""vn"": 0, ""ve"": 0, ""vd"": 0, ""cog"": 24600, ""satellites_visible"": 13, ""heading"": 24638}"
2022-05-15T16:05:21.890844,avr/fcm/location/global,"{""lat"": 32.8085261, ""lon"": -97.1563602, ""alt"": -0.1720000058412552, ""hdg"": -6245.528183606103, ""timestamp"": ""2022-05-15T18:43:51.557302""}"
2022-05-15T16:05:21.891264,avr/fcm/velocity,"{""vX"": 0.009999999776482582, ""vY"": 0.0, ""vZ"": -0.009999999776482582, ""timestamp"": ""2022-05-15T18:43:51.560023""}"
2022-05-15T16:05:21.901353,avr/fcm/location/local,"{""dX"": -2.5456197261810303, ""dY"": -1.5016621351242065, ""dZ"": 2.049142837524414, ""timestamp"": ""2022-05-15T18:43:51.571278""}"
2022-05-15T16:05:21.909915,avr/vio/position/ned,"{""n"": -254.60606976676002, ""e"": -143.7991712686676, ""d"": -370.6543833582757}"
2022-05-15T16:05:21.913765,avr/vio/orientation/eul,"{""psi"": -2.870100228693062, ""theta"": 0.7509557925331154, ""phi"": -1.982899257543946}"
2022-05-15T16:05:21.914391,avr/fusion/position/ned,"{""n"": -254.60606976676002, ""e"": -143.7991712686676, ""d"": -370.6543833582757}"
2022-05-15T16:05:21.914799,avr/vio/heading,"{""degrees"": 246.38824134310744}"
2022-05-15T16:05:21.915277,avr/vio/velocity/ned,"{""n"": 0.006583199572207324, ""e"": -0.020817144593196127, ""d"": 0.02579902535054221}"
2022-05-15T16:05:21.915846,avr/vio/confidence,"{""tracker"": 41}"

To stop recording, click the “Stop recording” button. This will stop writing to the log file.

You can do a lot of things with this data. For example, you can plot how your drone flew through 3D space using matplotlib and pandas:

import json

import matplotlib.pyplot as plt
import pandas as pd

# load in the CSV file
df = pd.read_csv("MQTTLog_2022-05-10_17-08-27.csv")
# parse the JSON data into the Pandas dataframe
df = df.join(df["Payload"].apply(json.loads).apply(pd.Series))
# filter to only data from the avr/fcm/location/global topic
px4_data = df[df["Topic"] == "avr/fcm/location/global"]

fig = plt.figure()
ax = plt.axes(projection='3d')

ax.plot3D(px4_data["lat"], px4_data["lon"], px4_data["alt"], label="PX4")

ax.set_xlabel("Latitude")
ax.set_xlabel("Longitude")
ax.set_zlabel("Altitude")

plt.legend()
plt.show()

Using matplotlib to plot a drone’s flight

Another example is plotting the drone’s battery remaining over time:

import csv
import datetime
import json

import matplotlib.pyplot as plt

filename = "MQTTLog_2022-05-15_16-05-21.csv"

x = []
y = []

with open(filename, "r") as fp:
    # create a DictReader to read the CSV file
    reader = csv.DictReader(fp)
    for row in reader:
        # only get data from the avr/fcm/battery topic
        if row["Topic"] == "avr/fcm/battery":
            # parse the JSON data
            payload = json.loads(row["Message"])

            # convert the timestamp to a Python datetime object
            x.append(datetime.datetime.fromisoformat(row["Timestamp"]))
            y.append(payload["soc"])

fig = plt.figure()

plt.plot(x, y)

plt.xlabel("Time")
plt.ylabel("Battery %")

plt.ylim(0, 105)
plt.grid(True)

plt.show()

Using matplotlib to plot battery percentage

PCC Tester

PCC Tester tab

This is covered when testing the PCC

14 - Checkpoint 3: Position Flight Test

15 - Peripheral Drone Assembly

15.1 - Gimbal Assembly

Overview

This section details how to assemble your gimbal. The gimbal allows the ground station operator to aim the FPV camera, thermal camera, and laser pointer at targets on the field independently of the drones position/orientation. The gimbal assembly will be used to detect hot spots on the field, put out fires using your water cannon, and perform reconnaissance with your FPV camera .

The gimbal uses 2 servos (very similar to servos used in previous years) to control the pan and tilt of the drone.

Pan is the rotation about the z-axis meaning this controls the left or right camera angle. Pan gets its name because it keeps an object in the picture or secures a panoramic effect.

Tilt is the rotation abut the y-axis meaning it controls the up and down camera angle.

Obtain the gimbal parts from the 3D printing section, 2 servos and associated hardware, a mosfet, the thermal camera, laser module, FPV camera, and long F-F dupont jumper wires.

Gimbal Parts Overview

Gimbal Base

Start with the gimbal base. Pass your servo wire through the slot on the slide and slide servo into place.

Gimbal Base Servo Placement

Secure the servo into the gimbal base using the servo hardware screws as shown below.

Gimbal Base Servo Mounting

Gimbal Pan

Next you will attach the servo horn with 2 arms to the bottom of the gimbal pan part using the servo hardware.

Gimbal Pan Servo Hardware

Be sure the geared part of the servo horn is facing away from the connecting face. Align the center hole and the 2 holes (one hole away from the end of the servo arm) with the holes on the pan part. Screw through the part to attach your servo horn to the pan part.

If done successfully your screws heads should sit flush with the bottom of the gimbal pan.

Gimbal Pan Servo Horn Attachment

Place a second servo in the gimbal pan part, this servo will be used to control the tilt of the gimbal. The gimbal gear and the tilt attachment arm should be on the same axis. Align the servo gear with the tilt attachment arm of the opposite side of the 3D printed part. Screw the tilt servo into the two holes on the side pan assembly; the final product of which should look like the following photo.

Tilt servo attached to gimbal pan part

Gimbal Tilt

Next we will be assembling the tilt mechanism. This is where all of our sensors will be mounted.

Thermal Camera Mounting

The thermal camera will be mounted in the center of our gimbal tilt part. Use 4 screws from the peripheral bag to attach the thermal camera to the drone.

Thermal Camera Mounting Overview

After screwing in, it should look like the photo below.

Mounted Thermal Camera

We will wire and test this in following sections.

FPV mounting

The FPV camera is mounted on the left side of the part (as shown in the picture).

FPV Mounting Overview

Cut a 3M double sided tape to the size of the base of the protruding area of the tilt part and place.

FPV Double Sided Tape Placement

Slide the camera into the slot and ensure that the camera is secured. You should be able turn the part upside down without the camera falling out.

FPV Mounted in Tilt Assembly

We will wire and test this in following sections.

Mount Servo Horn

Next place your servo horn into the the recess on the tilt part. We find that using a small amount of super glue is helpful in holding the servo in place before we attach it.

Tilt Servo Horn Mounting

The only remaining part of the gimbal assembly components is the laser, but we will come back to that after fully assembling the gimbal on the drone.

Gimbal Assembly

Now that all of the assembly 3D parts have been assembled we can start mounting the gimbal to the drone.

First, mount the Gimbal base to the drone using 10mm 3M screws included in your kit. Use the 1st and 3rd slotted holes from the front of the drone to mount the gimbal base.

Gimbal Base Mounted

Lock Screws

Pan and Tilt Calibration

Please watch the video below to understand calibrating your gimbal’s pan and tilt range of motion.

Command used in video for starting the services

cd AVR-2022/VMC
./start.py run mqtt pcm

Pan and Tilt Servo Wiring

You can clean up your servo wiring by using 12" servo extenders. You will run them up through the bottom, mid, and top plates and finally connect them to your PCC as shown in the photo below.

12" servo extenders routed up to PCC

There is no right or wrong way to manage your servo wiring. The only important thing is that you have your pan and tilt servos plugged into the correct ports as covered in the calibration video.

Laser Pointer Mounting

Components for laser mounting and wiring

Cut a small piece of your 3M double sided tape and place it on the end of your laser pointer being sure not to obstruct the view of the laser barrel.

Laser mounted in gimbal

Powering Laser and the FPV

Next we will be focusing on the FPV and the Laser wiring as shown in the following wiring diagram.

PCC Wiring

Solder extra header pins from the PCC section onto mosfet pins J1.

Mosfet with header pins soldered

Cut wires (black and red) approximately 6" in length.

Screw wires into the PCC Buck converter output terminal. There will be two wires coming out of the positive and negative terminals as shown in the photo below.

Leads that will power mosfet

Cut the extender provided with the FPV camera at the connector as shown in the following photo.

FPV camera cable ready to connect to mosfet

Place both the power and FPV wire ends into the mosfet input terminals and screw down to terminal to secure.

Mosfet Power Supply

Stack 2 layers of 3M double sided tape on the mosfet as shown in the following photo.

Mosfet Mounting

Next mount your mosfet and plug in your FPV camera.

Mosfet Mounting Location

Wire mosfet from the PCC. Wire A4 will run to the PWM. The Ground pin will run to GND.

Mosfet Diagram

Mosfet Wiring

Cut and strip one side of a black and red Female-Female dupont jumper wire to approximately 8" in length. Screw wires in to their respective terminal blocks. Place the black and red wire on the ground and signal pins of the laser pointer respectively as shown in the following photo.

Laser Wiring

Thermal Camera

Locate the thermal camera JST SH 4-pin connecting cable and four 12" jumper wires with corresponding colors from your kit.

Thermal Camera Wires

Connect long female-female jumper wires of corresponding colors. It may be beneficial to add a little bit of electrical tape to ensure they do not come undone.

Thermal Camera Wiring

Remove your plastic end pieces.

Thermal Camera Bundle

Attach the JST connector to the thermal camera and route the cables through the top accessory plate.

Thermal Camera Connection

Place your top cables into the 20x2 connector housing on your Jetson per the following wiring diagram.

Jetson Pinout

Thermal Camera 20x2 Connector

The final product should look like the following.

Thermal Camera Wiring Overview

15.2 - Gimbal Testing

Command used in video for starting the services

cd AVR-2022/VMC
./start.py run mqtt pcm thermal

15.3 - FPV Camera Testing

Overview

Your FPV camera has a built-in transmitter that will broadcast a video signal to the monitor, which has a built-in receiver. Open your FPV monitor box and pull out the components shown in the photo below.

FPV monitor and built-in receiver

The video below will walk you through setting the band and channel of the transmitter and receiver.

15.4 - CSI Camera

CSI camera and 300mm cable

Cable attached to VMC

Cable attached to CSI camera

15.5 - LED Status Lights

The status lights are designed to provide an extra layer of quick and easy debugging to show the status of your drone at a glance.

To complete the status light installation you will need the following.

Components with wires cut to 3"

Wiring

Wire the green wire to DIN, red wire to 5VDC, and black wire to Ground. Remove the plastic housing from other end of the wires.

LED soldered and ready for VMC wiring

Insert wires into VMC housing per the following wiring diagram.

Jetson Header Wiring Diagram

This should result in the following.

LED connected to VMC housing

Mounting

Use 3M double-sided foam tape to mount to the fan of the Jetson facing towards the rear of the drone.

Adhesive for mounting LED

LED mounted on rear side of cooling fan

Testing

Commands run in video:

cd AVR-2022/VMC/
./start.py run -n

Feel free to explore and try different combinations for what you think is the most useful information. For instance if you are doing just a flight test with no peripherals you may want to try the following.

cd AVR-2022/VMC/
./start.py run status -m

Light Definition

15.6 - LED Ring

In this section we cover how to install your LED light ring which will be used to communicate from the field back to teams.

LED ring

Route your wire lead through the side slot on the top accessory plate and plug into the PCC as shown below.

LED ring connected to PCC

Position the LED light ring under the top accessory plate around the inside of the standoffs and secure using zip ties.

LED ring zip tied around top mid plate

Testing

16 - Sphero RVR

Your Bell AVR Competition team registration includes complimentary access to the Sphero curriculum pages where they go into more detail about how to program and operate your Sphero RVR.

RVR Introduction / Getting Started:

• https://edu.sphero.com/cwists/preview/52597x

RVR Movement Intro Lesson:

• https://edu.sphero.com/cwists/preview/39622x

RVR Color Sensor Intro Lesson:

• https://edu.sphero.com/cwists/preview/39616x

17 - Autonomy and Beyond

Teams are encouraged to learn and practice programming with their drone. While it is not mandatory, programming the drone to perform tasks autonomously will give you an edge in the competition.

To gain an understanding of how autonomy works with the AVR drone please watch the video below.

Once you gain an understanding of how autonomy works through simulation you are ready to run your code on the real AVR drone. Make sure you pay attention to the following parameter:

MPC_XY_VEL_MAX

The default autonomous flight speed in PX4 is too fast for the AVR game court. You will need to slow it down. Our recommendation is something around 0.25 to 0.5 m/s, which is roughly 0.5 to 1 mph.

The example below demonstrates how we’ve set this param to 1 mph.

AVR drone right side view

The following sections will help you with:

• Installing and using VS Code to manage your project
• Installing and using Python
• Installing and working with git
• Using the Bell AVR sandbox environment
• Building and running your code with Docker

17.1 - VS Code

VS Code is a popular open source code editor from Microsoft. It is just one of many IDEs (Integrated Development Environments) that can be used to write and test code. You will be using VS Code to build custom software for your drone.

VS Code can be downloaded and installed from the following Link: VS Code Install

Once VS Code is intalled, take some time to familiarize yourself with the user interface. An intro to the layout and basic feature of VS Code can be found here.

In the next step, we will get Python installed and test example scripts on your machine.

17.2 - Python

Python is a general purpose programing language. Being one of the most popular programming languages in the world, Python is known for readability and accessability. This section will walk you through installing Python and testing it on your machine.

VS Code Extension

Before we get started, make sure you have the Visual Studio Code extension for Python. Go to your extensions tab, search “Python”, and install.

Installing the Python Extension in VS Code

This extension allows for debugging, auto complete, and python environment managemebnt in VS Code.

Python Interpreter

An interpreter’s job is to take the high-level code written by your team in VS code and to translate it into machine language that is executed by your computer.

The Python interpreter is installed from Python.org - install it from here. Select the installer and run through the installation process.

To confirm your installation, open a command prompt window and execute the following command:

py -3 --version

If your installation was successful, the output window will show the version of Python you have installed.

Setting Up a Project

Let’s set up a central location to store your future projects. Start by creating a “Projects” folder somewhere on your PC. Within this folder, make a “Hello World” folder. This is where we will create your first project.

In a blank VS Code window, open up this folder:

Opening a new folder from file

In your new workspace, create a new file called “hello.py”. The “.py” file format denotes a script written in python.

In this file, type the following:

print("Hello World")

Congrats, you’ve written your first python script! Before we run it, we will need to set up a python environment.

Setting Up a Python Environment

An “environment” is the context in which the python program runs. It consists of an interpreter and installed packages. We will be using “virtual environments”. These are are environments that are project specific and stored within the project itself. To create one in your “Hello World” project, start up a terminal.

Opening a new terminal in VS Code

In this terminal, type the following to create the virtual environment folder in your project:

py -3 -m venv .venv

To activate the environment:

.venv\scripts\activate

The environment should now be activated. You’re now set up to run your script. In the terminal, type and execute:

py Hello.py

If you were successful, you should see “Hello World” printed in the console.

17.3 - Git

In writing software for your drone, you will both need to interact with the sandbox environment as well as collaborate with your peers working on code from different machines. “Git” is built for tracking and managing changes between files. It is a staple of modern code management.

Windows Install

To install Git, simply select the standalone installer from the git-scm website

Run through the installation process. Once the install is completed, you will need to setup a username and email address for your machine.

Jetson Install

Git is already installed on your Jetson.

Git Configuration

Git needs to know who you are. To set up a username and email address, open a terminal and type the following:

git config --global user.name "yourusername"
git config --global user.email "email@youremail.com"

Remember this email, because you will need to add it to your GitHub account later.

17.4 - GitHub

The AVR codebase is currently hosted on GitHub. Not to be confused with Git, GitHub is a cloud-based hosting service that lets you manage Git repositories. In order to customize the software on your drone, we ask you to create your own account, join an organization for your team, and host a version of that project in github

GitHub Account

To get started, follow this link and create an account. If you already have a GitHub account, you are free to use that.

Organizations

You’ll want to create a group where you can set access permission for your code to the rest of your team. In your profile settings, add an organization. If an organization has already been made, ask your team leader for access.

Forking a Repo

Bell engineers have created the base AVR repository here. If you’d like to make changes to this codebase in order to modify your drone, you will need to fork the repository.

A fork is a copy of a repository. You will be able to make changes to the code without modifying the Bell codebase. To fork the AVR codebase, click on the fork button on the top right of the AVR GitHub Repository. If someone on your team has already done this, ask them to share access with you.

Bell AVR GitHub Page

Configure Jetson for the New Repo

Take note of the url of the repository you just made.

URL of the new repository

We will need to change the upstream URL on your Jetson. Run the following commands:

cd ~/AVR-2022/

git remote set-url origin https://github.com/your-username-here/AVR-2022

Your Jetson should now be configured for your forked Repo.

Syncing with the Bell Repository

If the Bell team makes changes to the main code repository, you will want to update your code fork to include those new changes. Updating your forked repo is simple in Github. Navigate to the main page of your repo, and select this “sync” option:

Fork Refresh

This option will allow you to see if your repository is behind. If it needs an update, simply select “Update branch” and sync the repository with your Jetson.

17.5 - Jetson Development

You should now be able to set up VS Code in order to modify code on your Jetson. If you have not done this yet, familiarize yourself with using SSH to remote into your Jetson.

Take note of the username of your Jetson, and the host IP address.

Remote Development with VS Code

VS Code has extensions that allow you to develop from a remote machine. From your VS Code window, install the remote development extension, from Microsoft.

Remote Development Extension

Bring up the command pallette in VS Code by pressing Ctrl+Shift+P. Search “SSH” and select “SSH: Connect to Host”

SSH Connect To Host

Type your username@IPaddress and press enter. Select “Linux” as your operating system. You may be prompted at several times to enter the password to your Jetson.

Operating System Selection

A seperate VS Code window should open. You now have access to the directories on your Jetson. On the left pane, select “Open Folder”.

List of directories on the Jetson

When prompted, select the AVR-2022 location and press “OK”.

You should now be ready for development on your Jetson.

17.6 - Sandbox

Your team will need to create a sandbox environment to develop from.

In the GitHub repository we’ve provided an area for you to write Python in order to accomplish your goals. The software stack for AVR is made up of a series of modules, which are actually independent Docker Containers.

Below is a graphic that shows the individual containers:

All of these modules communicate with each other over a message bus called MQTT. You could loosely think of MQTT like a social media feed. You can publish posts and your friends can subscribe to your feed to see them. Similarly, you can subscribe to your friends’ feeds and see their posts too.

Below is a non-exhaustive list of the kinds of data some of the modules publish:

• Flight Control Module
  • Drone Position
  • Drone Orientation
  • Drone Velocity
  • Drone Flight Mode
  • Drone Battery Level
• AprilTag Module
  • Visible AprilTag IDs
  • AprilTag relative Positions
• VIO Module
  • Zed Mini Position
  • Zed Mini Velocity
  • Zed Mini Confidence
• PCC Module
  • Laser States
  • Gimbal Control
• Fusion Module
  • Coordinate Transformed Drone Position
• Thermal Module
  • Infrared Camera Readings
• Status Module
  • Module States

You can read more about these modules here.

Your task here will be to subscribe to the necessary topics above and write your own logic to produce the desired output.

Using MQTT

You will be using the sandbox module to read from and interact with the other modules. By publishing messages to MQTT, you can create custom actions for your drone. The sandbox module has some example code to help you get started.

Example function that opens a servo

For full documentation of the MQTT topics and payloads available, go to https://pypi.org/project/bell-avr-libraries/ and scroll down to “MQTT Documentation”.

17.7 - Using Git

This section will intorduce you to the basics of using git and will walk you through an example using VS Code.

Basics of Git

Git has a handful of basic commands that are useful to know. These can be executed from the command line, but we encourage you to use VS Code’s GUI as you get started.

We will primarily focus on commit, push, and pull.

• A commit is used to capture the state of the project at a point in time. It saves any additions or changes to the local repository from your workspace.

• A push adds all commited files to the remote repository. In this case, your remote repository is hosted in GitHub.

• A pull gets files from the remote repository and puts them directly in your local directory. You will need to manually manage issues between conflicting files.

Example Git action diagram

VS Code Example

This will walk you through a Git command example using VS Code and the local repository on your Jetson. To start, make sure you have a VS Code window open with remote SSH access. Refer to previous steps for instructions on how to do this.

You should have an editor window on the left that looks like this:

Since you will be developing in the “sandbox” folder, we will experiment with that. Go ahead and add a new file. To do this, right click “sandbox” and “add new file”. Call it “test.txt”.

New test file in the sandbox directory

You’ve now made a change in your workspace, you can now commit it. Select the “Source Control” icon on the left pane of VS Code:

Source Control

The test file you made should show up in source control. Click the “+” button to commit the change. It will now be “staged”. In the upper text box, append a message to this commit describing the contents.:

Staged change with message

Click the check mark to commit the change. It is not saved in your local repository. The last step is to store this change in GitHub. The “Sync Changes” button that appears gives theuser the option to automatically pull and push to the remote repository. Select this to complete the process.

Pulling and Pushing your change

In the future, when working with others on your team, it may be necessary to manually manage conflicts when syncing changes.

17.8 - Docker

A Docker container is a lightweight executable package of a software that includes everything needed to run an application. In the AVR software package, parts of the code running on the Jetson(MQTT, AprilTag, Flight Control, etc.) are all run on individual Docker containers. You learned how to initialize and run them on the Jetson in the software section of this guide.

As a reminder, make sure to run the setup each time you want to pull the latest version of each of the modules.

cd ~/AVR-2022/VMC/scripts
git pull
./setup.py

To run the modules, use the start.py script.

cd ~/AVR-2022/VMC/
./start.py run

Your sandbox environment will be one of these modules. A basic sandbox.py script has been created for you. To run this specifically:

./start.py run sandbox

Each time you make changes/additions to your sandbox.py script, you will need to rebuild the module before running again.

./start.py build sandbox

18 - Diving Deeper

18.1 - Glossary

4S LiPo

4S LiPo refers to a Lithium Polymer battery that has 4 cells wired in series, which means it has a fully charged capacity of 16.8V. More info here.

CW/CCW (Clockwise/Counterclockwise)

CW stands for Clockwise and CCW stands for Counterclockwise. This refers to the direction a motor or propeller is meant to spin. A CCW propeller on a CW motor will produce lift in the wrong direction, so make sure to always double-check!

Electronic Speed Controller (ESC)

An Electronic Speed Controller controls how fast a motor spins. It receives a desired speed set-point from the Flight Controller and adjusts the power going to the motor to match the requested speed. More info on how they work here.

Flight Controller (FC) or Flight Control Computer (FCC) or Flight Management Unit (FMU)

The Flight Controller can go by many names, but in practical terms, it just a small computer that has sensors for determining the position and orientation of the drone, along with circuitry for controlling motors based on input from a pilot or autopilot. The flight controller used for the AVR (NXP RDDRONE-FMUK66) is running the PX4 flight stack, which provides basic functionality you’d expect from a hobby drone, and even some autonomy functions.

Ground Control Station (GCS)

A ground control station is an operator station from which your drone is controlled from. In our case, this will be a laptop running QGroundControl. More info here.

M3 Screw

An M3 screw is a metric screw with a 3mm diameter. This type of screw is used to build the entire X4 500 frame. More info here.

MAVLink (Micro Air Vehicle Link)

MAVLink is a standard protocol to send messages between a ground control station and an unmanned vehicle and vice versa. These messages include important information such as velocity, attitude, battery state, waypoints, etc. More info here.

MAVLink Router/MAVP2P

MAVLink Router and MAVP2P are both pieces of software that help to connect multiple MAVLink devices together. A standard MAVLink setup has a ground control station communicating directly with an unmanned vehicle, but these pieces of software allow you to connect a single ground control station to multiple vehicles or vice versa. More info here for MAVLink Router or here for MAVP2P.

Peripheral Control Computer (PCC)

The Peripheral Control Computer is a microcontroller running custom software that accepts requests from things like your laptop or, later on, the VMC to control servos and LEDs that are attached to it.

Power Distribution Board (PDB)

A Power Distribution Board is connected to your battery and takes the power coming from the battery and distributes it to the various components on your drone at the voltages and currents that they expect. More info here.

PX4

PX4 is an open-source autopilot software stack. This contains low-level algorithms running on the flight controller that constantly interpret things like position, attitude, altitude, heading, etc. and adjust the motors to keep your drone on course and can manipulate the drone to fly to desired positions. More info on PX4 here.

QGroundControl (QGC)

QGroundControl is ground-control software for drones and other unmanned vehicles. It allows you to easily connect to a drone and give it commands such as to takeoff, land, and uploading missions to it for it to perform. More info here.

R/C Controller

An R/C (radio-controlled) Controller can be used with QGroundControl to manually fly your drone while not in autonomous mode. More info here.

Vehicle Management Computer (VMC)

The Vehicle Management Computer is the companion computer that performs various tasks and communicates with the Flight Controller. This is where your custom software will be run to complete the challenges for the competiton.

Advanced Vertical Robotics (AVR)

The Advanced Vertical Robotics competition is a robotics competition put on by Bell Flight to challenge high school students to develop STEM skills outside of the classroom and work together to solve engineering challenges in a fun robotics competition in the vertical dimension.

X4 500

The X4 500 is the frame of your drone. This is what all of the components will be mounted to. More info here.

18.2 - Architecture

General

The software for AVR is designed around a pub/sub messaging system in order to exchange data throughout the system. This allows software modules to operate independently of each other, and to communicate with each other over a network.

A pub/sub messaging system is a system which allows clients to publish data to “topics” and clients can subscribe to incoming messages on defined topics. Think of how email works for example. You sending an email to someone is like publishing data to a topic (their email address), and you subscribe to all messages on a topic (your email address). However, a pub/sub system allows multiple clients to subscribe to the same topic.

With that in mind, the core principles of AVR software architecture are as follows:

1. Data exchange must happen through the MQTT broker.
2. All MQTT data must be JSON encoded.
3. All modules are run as containers.

Because of all of the hardware components of AVR (PCC, FCC, thermal camera, etc.), what this generally means is that each module acts as a hardware to MQTT adapter. For example, the FCM module publishes telemetry data over MQTT, and feeds fake GPS data from MQTT to the FCC.

This modular, open system makes it simple to add new modules or functionality to AVR. The GUI for example, is 100% based on consuming MQTT data.

Modules

Here is a description of the modules in AVR and what they all do.

Module Flowchart

AprilTag

Source Code

The AprilTag module is responsible for using the images pulled from the CSI camera to scan for visible AprilTags.

A low-level C++ program captures the images and hands them off to the Jetson’s GPU for processing and publishes the raw detections to the “avr/apriltags/raw” topic.

From here, a second Python program inside the module subscribes to this topic, and upon new detections, uses linear algebra to perform a coordinate transformation in order to get several pieces of data. These detections include the tags ID, as well as the drone’s absolute location in the court (pos_world), and the drones relative location to the tag itself (pos_rel).

This data is then broadcast out over MQTT for other modules, such as the Fusion and Sandbox modules to consume.

This is the only module with C++ code, for performance reasons.

Flight Control

Source Code

The Flight Control module (FCM) is responsible for communicating with the FCC over MAVLink. This module takes telemetry data from the FCC and publishes it over MQTT. Additionally, it takes fake GPS data from the Fusion module and feeds it to the FCC.

There also exists functionality to send commands to the FCC, such as arming the drone, or sending it missions, but this is disabled due to the drone’s current lack of knowledge of where it is in global coordinates.

Fusion

Source Code

The Fusion module is responsible for fusing multiple data sources to produce the final fake GPS data that is fed to the FCC. Currently, this only takes data from the VIO module, but experimental functionality exists to also take data from the AprilTag module to position itself more accurately in global coordinates.

This is the only module which is pure Python and has no hardware component.

Mavp2p

Source Code

The Mavp2p module is responsible for bridging multiple MAVLink connections together. This is just a Docker container for the amazing open-source project mavp2p.

MQTT

Source Code

The MQTT module is responsible for running the MQTT broker. This is a thin wrapper around the docker.io/library/eclipse-mosquitto container with a configuration baked in.

The port 18330 is used instead of the normal 1883 port because it puts it outside of the normal operating system privileged port range.

Peripheral Control

Source Code

The Peripheral Control module is responsible for communicating with the PCC over serial. This is a thin MQTT to serial bridge.

Status

Source Code

The Status module is responsible for consuming status information from the various other modules and updating the status LEDs connected to the VMC. This also communicates some with the host Jetson as well to check if it’s being power-limited.

Thermal

Source Code

The Thermal module is responsible for capturing thermal images from the thermal camera and publishing them over MQTT.

Visual Inertial Orientation

Source Code

The Visual Inertial Orientation (VIO) module is responsible for capturing data from the stereoscopic tracking camera, and converting it into global-ish coordinates.

This module considers wherever it is started as “0,0,0” and thus the drone’s movements are relative to that. Because PX4 only thinks in global coordinates, this module then uses a hardcoded latitude and longitude to convert the data into global coordinates. They’re not true global coordinates, however, as they’re still relative to where it was started.

This module is the core of the AVR “secret sauce” to enable GPS-denied stabilized flight.

18.3 - Control Loops

Control Loops

When a drone flies, there are many things going on at once, some of them are happening much more quickly than others. We can break these down as inner-loops and outer-loops.

Rate Control

This is the inner-most loop, running several hundred times per second usually. The purpose of this loop is to control the angular rate of the vehicle, that is, how quickly the vehicle is pitching forward or back, rolling to the left or right, or yawing to change its heading. If we can successfully control the angular rate of the vehicle, it is said that we are able to stabilize the vehicle. All other control loops are considered outer loops because they depend on this inner loop providing a stable vehicle.

Rate control is achieved by comparing a sensor value for the angular rate of the vehicle in each axis to a set point, or target, value. Once we have the knowledge of how far our state (pitch rate / roll rate / yaw rate) is away from where we want it to be, we can apply some gain factor (we can tune these gains to change the performance of the controller) to that difference, and we send those values to the motor controllers as motor commands. All control loops in our drone work on this principle.

Attitude Control

The Attitude control loop is the first outer loop, as its name suggests, this control loop allows us to command the vehicle to a particular attitude. If we wanted to hover, for instance, we would send attitude commands of 0 degrees, for the pitch and roll axis. It’s important to note that the output of the attitude controller is the input of the rate controller, they are effectively nested control loops. It is important to note the difference in frequency that these loops operate at; typically, an attitude loop is about an order of magnitude slower (or a division by 10) than the rate control loop.

Velocity Control

Similarly, the velocity controller compares velocity commands (usually in the form of forward velocity and vertical velocity) to a velocity estimate that has been calculated, applies some controller gain, and then computes what the desired vehicle attitude is to achieve that velocity, passing that desired attitude to the more inner loop below.

Position Control

Surely, you see where this is going. Once we can control the velocity of the vehicle, we are able to control the position of the vehicle, because velocity is merely the derivative of position, right? That is essentially true, however, we always need to keep in mind the different coordinate systems the vehicle is operating in. Almost exclusively, the coordinate frame that angular rates and attitudes are measured in is not relevant for position control, usually we want to command the vehicle to a particular latitude and longitude. How do you define a vehicle’s roll attitude in the coordinate system that latitude and longitude make sense in? There will be a coordinate transform between what position command is being set by the operator and how the vehicle interprets that before it can apply the controller.

For position control to work, the vehicle must have an estimate of where it is in space. This is where the VMC comes in, as we’ve mentioned, we are flying indoors and don’t have GPS to use a sensor, so we must find out the drone’s position with other sensors. The VMC uses two different sensors together to estimate the position of the vehicle in the inertial frame that is flying arena, that is, this frame is not moving, it is the reference for all other frames. Estimating position indoors is very challenging, and a great deal of work has been done to simplify the operation for these drones, it takes a lot of calculation and code to interface with the position sensors and generate these estimates, that’s why we have to do this work on the VMC and not the FC, the VMC is a much more powerful computer. Luckily for us, the position control loop is the slowest of the control loops, so we only have to send the position feedback to the more inner loop controls a few times a second.

19 - Troubleshooting

The following are some common issues that have been seen in the past.

For items not listed in the following sections please check the forum for existing answers or submit a new question.

19.1 - VMC

The following are some common issues that have been seen in the past.

In the rare instance that things get really bad, you may need to reflash your jetson. Should this be the case, the next few sections will guide you through this proccess.

19.1.1 - System Setup

Initial Setup

Select “Ok”

Scroll through agreement and select “Ok”

Select your language

Select your country

Select your timezone

Allow clock to be set to UTC

Creating your account

Enter a name, such as your school’s name

Choose a username, such as “avr”

Choose a password

Retype your chosen password

When asked about resizing the partition, leave the default.

Network Configuration

Setting up a network connection is not needed at this time. To bypass this, select “dummy0” and let the autoconfiguration fail.

Go ahead and select “Do not configure the network at this time”.

Final Setup

Select an appropriate hostname for your Jetson. “drone” is a good choice.

Choose the “MAXN” power mode.

Let the installation finish. Once it’s done, reboot your Jetson.

19.1.2 - Installing VMC Software

Internet

In order to install the AVR software, your Jetson needs to have an internet connection. The easiest way by far is if you have ethernet available. If so, just plug an ethernet cable into your Jetson and you should be good to go.

If you don’t have ethernet, you can use a WiFi connection. First, you can list the available networks with:

nmcli device wifi list

Example:

WiFi network list

Hit q to exit the list.

If the Jetson is already connected to a WiFi network, you can disconnect it with:

sudo nmcli device disconnect wlan0

To connect to a WiFi network, run:

# with a password
sudo nmcli device wifi connect <network name> password <password>

# without a password
sudo nmcli device wifi connect <network name>

such as:

sudo nmcli device wifi connect "WI do drones FI" password "Flying_Is_Fun"

If your network name or password has a space or other special characters, you’ll need to wrap it in quotes as shown above.

Install

git clone --recurse-submodules https://github.com/bellflight/AVR-2022 ~/AVR-2022
cd ~/AVR-2022/VMC/scripts
chmod +x setup.py
./setup.py

This clones the software repo, changes directory into the repo you just cloned, makes the setup script executable, and then executes the setup script.

Setup script starting

This setup script will automatically install and configure everything needed on your Jetson to get it ready for competition. This script does do operating system updates, so depending on your internet connection, it may take a while to run.

At the end of the setup script, it will perform a few self-tests to make sure everything is configured properly.

Self-tests passing

Once this is done, please restart your Jetson. Some system settings were changed that require a reboot to take effect.

Reboot prompt

After this, you should be ok to continue on with the setup per the updating per Updating VMC Software