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Hi everyone,

I built a 250 FPV quad with DYS1806 2300kV motors, equipped with 5040 props and Mini APM 3.1. The Mini APM is placed in a box and foam above the baro sensor. The box itself is fixed with vibration reducing gel pads.

The quad is flying quite nice, but once I stitch to Alt Hold, the alitude is maintained only poorly. It is going up and down by 1-2 meters. Data log review does clearly show that alitude is not stable. It seems that the APM is giving not the correct output for the motors.  I some screen shots of the plots (desired Alt, Baro Alt and Alt) with and without_GPS module as well as the vibrations. To my opinion they don't look very bad as they are within the given range of -5 to -15 for AccZ. In the next post I'll add the respective log files.

PID-settings for Alt-Hold are standard, so nothing changed. I tried a bit, but without any success.

Does anybody know the reason and what to change to improve Alt Hold?

Thank you in advance.

Matthias

vibration.jpg

with_GPS.jpg

without_GPS.jpg