Been watching my first vid taken on the quad, and noticed something that I'd also seen on the ground in previous flights - when switching to alt hold, the engines cut completely off for a second or even 2, before spinning up again. This results in an alarming "hold-you-breath" moment, as you wait for the motors to kick in. It's only a second or two, but they're the longest 1-2 seconds in the world...:-)
And they do, and once running, alt hold works perfectly, and seems to return to the correct altitude almost immediately.
Is this normal? Does it do this if you engage alt hold while still climbing? I'm thinking it does this because when AH was engaged and it's still climbing, it cuts the motors to descend back to the original "set" altitude. However, even in what looks like a steady hover it does a dramatic - but brief - drop.
Replies
What code version are you using and witch ESC ?
The altitude controller try to slow down ascension reducing throttle to minimum and in your case it is cutting motors where it should not.
You should check that :
- check your ESC calibration, they could be off causing a motor cut too early. If ESC are rightly calibrated then adjust THR_MIN parameter so that your ESC do not cut. Witch ESC are you using ?
- do you have motor pulsing during alt_hold, specially when climbing in this mode ? If yes then your altitude controller gain is too high.
- set your THR_MID parameter so that your hovering point is perfectly at mid stick position. So that you don't have throttle jumps when switching from manual throttle mode to an auto throttle mode.
http://copter.ardupilot.com/wiki/advanced-parameter-list/
Avoid to engage alt_hold when you are climbing fast, same thing for other auto modes.
I think that you have mainly an ESC calibration problem to solve.
Olivier