Hi all,
I have a serious AltHold problem with my brand new hexa... In never faced it with my quads... I'm running AC 3.1 rc7 on an APM 2.5 with external Compass.
Stab mode is perfect with default parameters, really responsive and easy to fly.
AltHold and Loiter are really perfect until I touch the yaw and... the hexa falls like a brick... or climbs like a rocket. (depending on the input, left or right)
If I release the yaw stick it stops falling or climbing (still needs 2-3 meters to recover).
I feel lucky not to have crashed it more seriously the first time I tried the hexa, only a broben skid...
I tried to reproduce this behaviour later and it happened again.
I already tried to change "AltitudeHold P" up and down but without success.
Thanks for your input...
Olivier
Here is today's log file with hard landing caused by this problem...
Replies
Do you have an idea about the reserve power for each motor? I have an endurance hexa which didn't demonstrate this behaviour, but someone with the same model had yaw issue like you describe.
Turns it out was related to the exact angle the motors are mounted and therefore the inclination of the props in relation to the plane of the hexa. Some of these motors were only angled by a degree and therefore generated a force that made it rotate.
The result is that you see all (C)CW motors have a consistent higher PWM input than the others. This could also be an indication of bad prop efficiency for (C)CW props.
I put the hexa on a flat surface (glass table) and measured from the table plane to the prop tip what the distance was on either side of the motor. Then I rotated the prop around and did the same and averaged the values. On two motors of the same clock direction I found 5mm difference, so these were angled. I put a bit of stuff between the motor and the frame, which corrected the angle and all motors now run relatively equal.
It may also be that your yaw rate gain is too high, so you can try reducing that.
Of course, all ESC's need to be tx calibrated as well.