Servers by jDrones

Throttle oscillation when MIN_GNDSPD_CM takes effect

I’m having problems with severe throttle oscillations (amplitude is a significant percentage of available throttle travel, frequency less than 1s) when the ground speed falls to MIN_GNDSPD_CM due to headwind. I have performed autotune and TECS tuning steps as per the wiki.

Loiter is also poor in the wind conditions, looking like a curly single speech mark!

The plane flies great in all other circumstances.

The parameters are set to:

AIRSPD_FBW_MAX = 29m/s
TRIM_AIRSPD_CM= 1500
TRIM_THROTTLE=40
AIRSPD_FBW_MIN=11M/S
MIN_GNDSPD_CM=700 (or 600)

Wind was 8-9m/s as reported by Arduplane.

I’ve tried slight variations on these, the effect is unchanged.

Setting air speed to a value that keeps ground speed just above the min ground speed, or throttle nudging both eliminate the oscillation but this shouldn’t be necessary.

I haven’t changed the default values of THR_SLEWRATE, TECS_THR_DAMP etc. Should I try these? I’m concerned it will mess up the performance in other conditions and this may be caused by something else.

Unfortunately I cannot post log files but can provide screenshots of graphs etc.

Has anyone else had this issue or know a solution?

Thanks!

Servers by jDrones