Hi,
I'm having some issues with a quadcopter i'm building. Here is the spec:
2217q 880kv motors with 10x45 props
S500 frame with PDB
30A quattro 4in1 ESC (I've also tried individual SimonK escs with no difference)
APM2.8 hardware with external compass and GPS
Flysky FS-I6 transmitter with PWM receiver.
4000mAh 4S Flureon battery (25C)
I'm running 3.2.1 firmware, my quadcopter is in the X configuration.
The problem i'm having is the quadcopter exhibits some extreme instability during heavy throttle and fast yaw movements. When i drive it up hard and fast it flips 180degrees in roll, like one motor is driving way too hard. This is reproducible. Slight bursts of throttle induce roll also. As for the yaw, fast yaw movements cause parasitic motion in the pitch and roll axes, i'm not sure if this is related.
To try and get to the bottom of this issue I have swapped the ESCs, moved motors around and changed props, it's always the same arm / motor that seems to instigate the flip.
I set the APM logging and i've had some interesting results that I can't fully understand. Just before it flips I give it heavy throttle (just after line 2500 of the log file), all motor outputs (RCOU) give a similar response except for channel 2 which seems to reduce it's output prematurely. This reduction in output appears to precede the sudden change in roll (the flip) which makes me think this reduction in output is the cause of the flip.
I'm out of ideas. The next thing i'm going to try is soldering all my motor connections rather than using bullet connectors, perhaps a heavy current draw drops too many volts over a bad connection. I'll also remove the apm and hook up the motor outputs to a scope, I would assume that if the APM is level and I give it full throttle the pulse widths of all motor outputs should be more or less the same.
I've attached the log file, any ideas would be much appreciated as I just can't seem to get to the bottom of it.
I'm aware I have compass / GPS issues, this hasn't always been the case but it shouldn't effect stabilize mode should it?
I think my tune is ok as the response in roll and pitch is very good the vast majority of the time.
Thanks in advance.
Lee
Replies
Hi,
Yes I found the problem. The frame was too flexible for the motor / prop combo. I changed to an f450 frame and the problems went away. I found this by tethering it to the ground and videoing it with a go pro at high fps. Slowing it down showed one arm oscillate like mad. A stiff frame really is very important, I didn't realise how important it is! Hope this helps
Hi, bro. Im having the same issue with the Mini Apm v3.1. When i start to throttle it gradually, at on point, its start to flip. In my case, 3 motors are running at same power, but one of the motor seems to be not sync with the other motor. Have you found the issue?
Bummmp