I have a very annoying yaw wag after changing my ublox 6M + compass from Goodluckbuy to the newer Drotek M8M + compass. The Drotek has the 5983 compass on it. That’s really the only difference besides the gps. The only other change was going from the latest 3.2RC to the full 3.2.
My setup:
FPV Dream Machine Tricopter
Immersion EZOSD + UHF
MiniAPM 3.1 + Bluetooth, no power module
Prior to my changes, using the latest 3.2RC and the cheap Ublox 6M + compass, everything was perfect and I flew the snot out of it. Perfect loiters, alt holds, and many missions. No problems at all. After adding the Drotek, I get an almost perfect uniform oscillation in the tail. I have tried different pids to no avail.
I have attached a log file from a quick flight in my yard. You will see the yaw oscillation. Prior to the new gps, my desired yaw followed the actual yaw very tight, just like in roll and pitch. My vibes are fine. They are not included in this log file, but I double checked to make sure. I have done numerous compass calibrations and they all turn out very close to each other. My motors are calibrated and in sync. When I point the copter North, Mission Planner shows North. My mount has no metal screws around - plastic case and plastic screws.
Wow, that is some wild oscillation! You say that you played with the PIDs, but I notice that your Yaw I is really very low. Have you tried increasing it?
Last time I helped people with Tricopters, just increasing the gains straightened them out.
I really can’t see how the compass would affect anything.
I do notice that you’re using the ATC functions, any chance that had an effect?
It is possible that the ATC might be doing it. I just added those based upon your suggestions from another thread. It’s been mostly windy here and I really didn’t know how bad it was until recently when I finally got a calm day. It’s flyable with the oscillations, but I just figured it was the wind playing with the tail.
Yeah, I’m not sure about the ATC, but it might be worth the effort to turn it off, or turn the yaw settings up really really high, like 144000. Or I supposed you can turn off just the yaw ATC by setting it to zero. It would be interesting to know if it plays a role.
I can say that I am not totally happy with the tail control of helicopters. It can also oscillate, it doesn’t stop cleanly after a pirouette, etc. I would not be surprised to find that the tricopter situation is similar.
Also, Tricopters do not have yaw rate feedforward, like helicopters do, and I wonder if that would help.