Large quadcopter with height radar not holding height at stopping or accelerating

ArduCopter Copter 4.1
1

Hi,

I´m having trouble adjusting height PID for 25Kg quadcopter with height radar. I had this problem slighter with V4.0.7 and now with V4.1.5 it got severe. After flying straight forward in Loiter and performing a stop, the copter loses about 1m to 1.5m (also happens when I accelerate). This is probably a relation between Rangefinder and barometric height information fusion. In version 4.0.x there was RNGFND_GAIN and in version 4.1.X there is RNGFND_FILT. Is this just a name change or also a function change since the behavior with the same numbers is different (I use 0.8)? Any suggestions in the PSC_ parameter class tunning?

Flight log with height problems when stopping or accelerating.

2

It looks like your barometer is affected when you change directions and altitude (more than it should be). See if you can shield it better from propwash.

3

Thanks Shawn, but I don´t think it is propwash since the cube is well protected inside the frame body. Seems much more a tuninng issue.

4

Did you try changing EK3_SRC1_POSZ, 2 (RangeFinder) ?
And try doing similar maneuvers within the rangefinder’s maximum range, so we can rule out any unusual pressure variation issues in the barometer
Make sure to fly over a relatively flat ground for better comparison