Can this be done?

Is it possible to have the Flight Control Software provide specific control inputs when it’s somehow triggered?

That sounds a bit vague so I will add some more detail to help explain myself. I am planning to carry out System Identification/Parameter Estimation on the flight data from my Pixhawk. An example test flight can be something like:

  • Take the aircraft to Altitude X
  • Fly level and steady
  • In that situation, provide an abrupt control input designed to excite certain dynamic modes of the airplane
  • Have the control inputs and all sensor outputs recorded

I wish to process that data to estimate essential parameters (ex. stability and control derivatives) for my modelling of the aircraft in Simulink/Matlab.

What I need PX4-QGS to do is to have that ability to execute a pre-programmed set of inputs on command.

Is it doable? How?

I think it’s certainly doable task depending on how much you are familiar with the code.
Since you are playing with airplane, you should check out what fw_att_control and fw_pos_control in /src/modules have in the code.
There you can see how the controller interact with the input and find what needs to be modified.

Also there is a debug_vect or debug_key_value message as a mavlink message you can add in the code to see if it is actually working. And these messages can also be logged in sd-file if enabled in /src/modules/logger


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Thanks for the input. I actually came across something that seemed very relevant:

I’m trying to understand what this is and if it can be used and if so, how to go about doing it. :slight_smile: