Here are two videos of us trying to get our baby to fly:
We have HK-SS20A ESCs and KDA-20-22L motors. We suspect pretty bad PID settings and we will continue to keep trying to fix the problem by tweaking the PID settings. But we wanted to know if any of you had any other ideas of what may be going wrong. Jani Hirvinen suggested that our ESCs might be of different kinds even though they are advertised as being the same or something may be wrong with them. But upon changing the connections of the control lines from the receiver to the APM the two motors that were running slower and causing the oscillations changed to another pair of motors. Also we have checked our ESC calibrations and that the motors are rotating in the correct direction. Any help would be greatly appreciated.
Replies
Did you double check the direction of the electronics?!
If you are using the RC1, it always have to point along the front arm with clockwise motors, if you are using trunk it should point in the middle of the arms for X setup and in front for + setup.
I have a GAUI frame (much smaller than what you have) and default PID setting don't give that behaviour even though I had to lower them a little...
Emile
Lower the PID settings by 20%.
It's easier to hold it in your hand when you are having problems. It isn't going to fly anyway, and you can lightly hold it and get a feel for which motor is trying to take over. Your hand can be a strong damper to a light damper as needed.
If it looks pretty good with a light hand hold you can try a test flight.
- to determine if it's a hardware problem, swap the ESCs around - is it still the same two motors running slowly or has it changed. If it's still the same two motors then you know it's not a hardware problem. If the problem motors do change then it sounds like the ESCs (like Jani says) and I'd recalibrate them and if that doesn't work I'd get a new set.
If the test above shows it's a software problem, then I suspect it's your PID values. The default PIDs are set-up for the default hardware so might not work perfectly for you. There's some description of the PID controls on the Flight Tips wiki:
https://code.google.com/p/arducopter/wiki/Quad_FlightTips
It's a bit of trial and error...I'd recommend reducing your P term down in stages (by 10%~20% each time perhaps) to see if it makes things better. If you end up with something that's sluggish but still wobbly then it starts sounding less like a PID problem and maybe it's excess vibration (but if you're using the standard ArduCopter frame this shouldn't be a problem).