APM Arducopter: Problem with Altitude Hold Solved
The problem:
As soon as I engage Altitude hold on my Arducopter Hexacopter, it shoots up instead of holding a nice steady altitude as expected.
The solution:
My throttle mid-point was not exactly at centre and when I engaged Altitude hold, the throttle stick becomes an altitude adjustment control as opposed to a throttle meaning relative to the centre position, if the stick is up, the Hex will rise. If the stick is below centre, it will fall. I analysed a logfile where I had been hovering in a nice stable position and found my throttle setting to be about 480. I thought this would have been close enough to the default (500) but apparently not because after adjusting THR_MID, the Hex hovered perfectly in position.
These URLs helped me identify and solve the problem: