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Flight Controller Setup and Calibration w/ QGC
In this section we’ll walk through the final steps of loading firmware and calibrating your drone before your first flight.
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.
Note
For Ubuntu 22.04 users, you may need to additionally install libfuse2 before the
AppImage will work:
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!
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.
Note
Be sure you grab the correct 6c firmware, there will also be a 6x build,
px4_fmu-v6x_default, but that is for a different flight controller
and is NOT to be used.
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
Note
Make your FC is NOT plugged in when accessing the firmware setup screen.
First access the firmware screen and THEN plug in your FC.
It will recognize the connection and initiate the process.
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
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.
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.
Note
Given advanced assembly of your drone will require additional autonomy components
and peripherals, it is a good practice to understand the calibration process in detail.
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.
Note
Don’t be thrown off by the images of an airplane in the QGC
compass calibration process. This still applies to the AVR drone.
Begin the process of rotating the AVR drone around the highlighted axis.
Tip
You may find it difficult to rotate the AVR drone with USB connected.
It is helpful to have someone keep the cable out of the way while another
rotates the drone around its designated 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
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.
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.
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 - 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.
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.
Tip
It is not necessary to do this motor test every time you fly,
but it is highly recommended if any wiring modifications have been
made to your AVR drone.