I am tuning PID parameters on a very large quadcopter and having issues with oscillations in stabilize. I have solved my vibration problems, but it is still a rather flexible frame which would allow low frequency vibration on the arms of the frame which support the motor.
Because it is barely flyable currently I can’t easily tune the parameters by trial and error, and autotune is out of the question at this point. Which direction should I adjust my parameters to try to reduce the oscillations I’m seeing?
I have checked the pitch rate versus desired pitch rate (PDes vs. P) and can see the pitch follows the desired pitch (although with a considerable delay). Is it possible I can reduce my oscillation simply by reducing the P term for stabilize?
If it’s a large craft I would start with reducing the Rate Pitch and Roll filter to 10Hz. Then put Rate Pitch/Roll kP on a In Flight Tuning pot and go from there.
It’s 8 ft long and 6 ft wide. Reducing the acc and gyro filter to 10 hz helped a lot. After that I saw there were rate p itch and roll filter as well… didn’t touch them as I’m not sure what the difference is between that and the acc and gyro filters. Possibly they are downstream?
I also built a frame to mount the whole thing on, and isolate the roll axis (so it cannot pitch or yaw). I was able to find flyable parameters like this and will probably be doing an autotune down the road.
The accel and gyro filters set the filter cutoff for the sensors and I saw you already lowered them to 10Hz. The Rate filters set the cutoff for the PID loop control, try lowering them as well. Autotune may not work well if the frame is as compliant as you suggest.