Varying Actuator Outputs During Flight

PX4 Autopilot Multicopter 🛸
1

Hi All,

I have a Holybro x500 v2 quad-copter frame that I have been using for the majority of my research project. I’ve noticed this for a while but have finally decided to take on the task of figuring out why my actuator outputs are all different.

An example of this can be seen in the figure below:

image
image2024×1380 209 KB

During my usual flights, I normally fly in offboard mode via microRTPS (px4 v1.13). Some observations I’ve noticed is that my y-axis (NED frame) seems to be the worst and the drone experiences oscillations in this axis for a while before settling (most likely just a control issue but my x-axis seems to track fine).

Apart from this, the major observation is when going into POSCTL mode and flying using an RC controller, there is a notable yaw bias (clockwise rotation w.r.t to NED). This seems to align closely with the graphs I have been observing from the Actuator Output logs.

To debug I have done the following:

  • Change each motor on the quad separately
  • Change the ESCs separately
  • Calibrate the ESCs

Here are some log files to observe if anyone is interested:
https://review.px4.io/plot_app?log=2e9cee99-418e-4244-bfc4-13961648c555
https://review.px4.io/plot_app?log=2fafa8d7-2fa2-43ac-8fd8-3674f758b317

Any advice or help is appreciated! Thanks!

2

It looks like a yaw imbalance indeed. Have you checked whether there is no tilt on any of the motors that would cause this?

3

Hi @JulianOes, no tilt on any of the motors. I also checked with a level to be sure and they are mounted on straight to the carbon plate they sit on.

Although it doesn’t really make sense to or is the likely cause, I did swap around the motors on the PDB that comes with the x500 v2 kit. I still get a similar output. I don’t have a spare PDB to swap with but I do have an extra PWM breakout that I could probably try to swap out just to see if something changes.