How can replace default controller parts of PX4 with custom algorithms controller?

I want to change controller algorithms of PX4.

So I am learning 'UAV Toolbox Support Package for PX4 Autopilots'

I want replace controller parts of px4 firmware(default : 'mc_att_control' and 'mc_pos_control)' with custom controller.

Path following flight is performed simply by connecting PX4 to the drone and simply giving a mission with QGC.(Before using UAV Toolbox Support Package for PX4 Autopilots)

if I want to change only the controller of PX4 using the UAV Toolbox Support Package for PX4 Autopilots, I wonder if I can design and build only the controller. Or, I wonder if I should design all the processes (connecting to QGC, transmitting and receiving msg, etc.) from the beginning with simulink. There is no example for this, so it is difficult to proceed.

P.S.

It would be very helpful if there was an example of flying a real drone by building a custom algorithm in PX4. (not simulation)

Answer 1

[Jianxin Sun]

Hi SeungWoo,

You can use the support package to replace the PX4 controller only. Please refer to the "integration with general PX4 architecture" doc page for details. You will also need to enable the mavlink module if you want to enable communication with QGC.

The following examples show how to replace multirotor position controller in PX4:

https://www.mathworks.com/help/supportpkg/px4/ref/position-tracking-with-rate-example.html

https://www.mathworks.com/help/supportpkg/px4/ref/position-tracking-example.html

https://www.mathworks.com/help/supportpkg/px4/ref/simulator-plant-model-example.html

Jianxin

[SeungWoo Park]

Hi Jianxin

Thanks for your answer.

First, I have some questions.

If i want to replace controller with custom controller, should i make code with code generator or just build controller?

And the user's guide said that you can replace the controller without touching anything else, so I was curious.

I wonder if it is the right way to build after designing only the controller in the simulation except for all other things. Or, I wonder if the entire flight system should be designed as a simulation.

Park SeungWoo

[Jianxin Sun]

You can follow https://www.mathworks.com/help/supportpkg/px4/ref/position-tracking-with-rate-example.html and https://www.mathworks.com/help/supportpkg/px4/ref/qgc-hitl-example.html.html example to replace controller module on PX4 stack. The support package would compile the Simulink model as a controller module, disable the original PX4 controller module, build and deploy this modified PX4 firmware stack to the target according to your hardware configuration.

Since you only need to replace the controller, you only need to design controller in Simulink and reuse other modules in PX4. When you test the controller with SITL/HIL setting, your controller will be running along with other modules in PX4 as a complete software stack.

[Tristan]

@Jianxin Sun

Are these only relevant to certain PX4 versions?

[Jianxin Sun]

In R2023a, the PX4 support package supports PX4 1.12.3 firmware version. The supported autopilot hardware is listed on https://www.mathworks.com/help/supportpkg/px4/ug/supported-flight-controllers.html

The release note lists the release to release support updates: https://www.mathworks.com/help/supportpkg/px4/release-notes.html

[Jonah Whitt]

@Jianxin Sun

Hi Jianxin. In "integration with general PX4 architecture", it would appear that you can replace the "Position Controller" and "Attitude & Rate Controller" modules.

However, in all the examples you have provided, it appears the "Output Driver" block is also being replaced (a custom "To Actuator" block is present in all of the examples).

How can I set up the build to only replace the Position, Attitude, and Rate controllers, or are there any examples that I missed which do this?

Or is the diagram under "Supported Modules that can be Replaced with User-Defined Algorithms" inaccurate, and the Output Driver module is also being replaced?

Thank you!

[Jianxin Sun]

Hi Jonah,

I assume you want to keep using PX4's mixer instead of using the PWM blocks from the PX4 support package? In that case, you should consider use the "PX4 uOrb write" block to write to "actuator_controls_0" message. This will let you send roll/pitch/yaw/thrust commands to PX4 firmware, which will then be translated into actuator outputs by PX4 firmware mixer.

You can check the following examples:

https://www.mathworks.com/help/supportpkg/px4/ref/actuator-control-uorb-blocks.html for a simple model

https://www.mathworks.com/help/uav/ug/validate-multirotor-uav-model-by-playing-back-flight-log-in-simulink.html for a more complete model in the controller deployment section.

Jianxin

Answer 2

[Massimo Satler]

Hi Jianxin Sun, I saw the system requirements section where it is recommended Ubuntu 18.04 Is it possible to use the support packets with Ubuntu 20.04 and matlab 2022a?

[Jianxin Sun]

From R2022b, the PX4 support package supports PX4 1.12.3 and Ubuntu 20.04: https://www.mathworks.com/help/releases/R2022b/supportpkg/px4/ug/download-px4-source-code-ubuntu.html