Abnormal mission following

PX4 Autopilot
1

Hi, I considered a simple hover mission for my drone, including 3 total points, (1) take off to altitude 1.5 m, (2) hover for 2 minutes in the same point with a specified heading angle, and (3) landing to altitude 0. My quadrotor often faces a problem. It takes off and goes to the desired point, it holds for example for a minute, and then it reduces its altitude to near ground and again climbs and holds for one or two minutes and it does not land!! Do you have any idea? Sometimes also it has oscillations, especially after rapid changes. I checked its PID tunning and it was ok. One of data logs are here: https://review.px4.io/plot_app?log=1d6f5286-c491-4d32-b235-a6bd3d695801

2

Hi @Shd ,

Your vehicle is quite overpowered as it hovers at ~17% thrust. This is not a big problem, but it is unconventional and requires a few adjustments to fly properly.

  • set MPC_THR_MIN to ~0.05 (default is 0.12 and way too close to your hover thrust of 0.17, this is why the drone struggles to descend)
  • set MPC_THR_HOVER to 0.17. The hover thrust estimator estimates it correctly, but the change from 0.5 (default) to 0.17 (when the estimate gets valid) is too large and creates a transient issue in the velocity controller (explaining the sudden climb after takeoff).

Good luck!

2 Likes
3

Thank you so much, do you also think it has caused the altitude tracking problem?

4

It is highly possible, yes.

1 Like
5

I also have another problem. I put my desired altitude to remain the same at all the time but we can see the z setpoint value is oscillating at first seconds. What is the definition of these setpoint values and why do they change?