I was doing some high speed testing yesterday on a custom "H" quad. There were several instances where at high speed (>20m/s) a violent oscillation on pitch occurred. Initially I suspected a tuning problem and so tried to crank up the pitch gains, but this did not offer any improvement. After reviewing the log files I can see that the oscillation is in fact being induced by the control system.
check out the pitch chart in this log at times 5:48-5:52, 7:24-7:29, 10:50-10:55, 13:21-13:24
It seems that the controller is commanding oscillating pitch values when throttle = 100%. While it does make sense to back off on pitch at high throttle values, the oscillation it creates is frightening. I suppose it is possible that phase delay on the pitch response of my platform is to blame, but that the fact the the pitch controller is allowing this oscillation to get set up is disturbing.
Is there a way to fix this problem or is it simply a matter of I need to ease back on the speed?
Similar problem occurs in this log at times 12:45-12:52,