So heres the scoop. I had a well flying quadcopter using an APM 2.6. I decided to move to pixhawk. Bought a brand new unit from 3dr. Wired everything up and installed 3.2 Took it out to fly today and wasn’t able to get it off the ground. The throttle and motors seemed to be acting weird and it sounded almost like a grinding sound. Keep in mind these motors flew through two batteries just the other day on my APM 15min flights each without a hiccup. The only thing thats changed since then is the flight controller. I brought it home and flipped the props and went to work trying to debug. I did the motor test in mission planner and ran each motor up to 15% throttle. Everything seemed fine, no weird grinding. So I got my camera out and started recording while I armed and tried the throttle. Again I was getting the grinding noise, then I noticed that above 50% throttle it seemed like no more actual throttle was being applied but the grinding noise got louder. I blipped the throttle a few times and sure enough it would seem thrust was coming up to the 50% point and then it was just making a louder grinding noise but not giving anymore thrust beyond that. SUDDENLY all the motors went to full power. No grinding noise anymore. I closed the throttle but nothing happened it was stuck wide open. I tried to disarm but it wasn’t responding, so i took cover behind the bed as you can see in the video. The whole time I am trying to disarm. Eventually unsure of what my best move was I decided to turn off my transmitter. A moment later the motors returned to idle and I was able to disarm through my laptop (which I might have been able to do all along but in the rush I didnt think of it).
As I look back over that video. You can see the copter slides off my excellent tupperware support. Could that be the cause of the throttle lock? The board sensed it was leaned over and sent full power to that side trying to right itself? If thats the case than the full power isn’t an issue, but the grinding noise still is.
So I did another test this time with lots of bungees. The motors are making a real obvious grinding noise. But it sounds like a digital grinding to me, like maybe the throttle output from the pixhawk isn’t clean or something? I run up the throttle here and you can hear the obvious grinding. Then I do the motor tests again individually. Each motor makes the grinding noise when set to 25% throttle and tested. When I spin the motors by hand they spin completely smoothly and make no grinding sound, so im thinking it must be electrical/digital. These motors/escs were working perfectly fine with my previous APM setup. The only thing I have changed is swapping the APM for the Pixhawk and I also swapped my previous power module with the 3dr one that came with my pixhawk. Otherwise the motors, escs, power distribution is all the same.
Hi,
Looking at the video, it looks and sounds like an ESC desynchronization issue.
Did you wire correctly the esc’s signal AND ground cables to Pixhawk’s rail?
Are you using simonk flashed ESCs? (Known to cause sync issues in certain configurations)
Rgs
Hugues
[quote=“Hugues”]Hi,
Looking at the video, it looks and sounds like an ESC desynchronization issue.
Did you wire correctly the esc’s signal AND ground cables to Pixhawk’s rail?
Are you using simonk flashed ESCs? (Known to cause sync issues in certain configurations)
Rgs
Hugues[/quote]
These are Afro escs which come flashed with simonk. No I do not have the ground wire run for the escs, only the signal. It seemed to work fine without the ground wire on the APM? Someone else mentioned that they had this same issue with 3.2 and that reverting to 3.1 solved it. I was going to try that tomorrow night.
I would start by ensuring that each of the ESC signal and ground wires are connected. Then you can be sure that the controller and ESCs are using signals with a common ground reference. It may well be that there was a noise free ground path from the ESC and the APM in your old configuration that allowed you to get away with it in the past.