Pixhawk causing motor sync issues.

I believe I have a problem with my Pixhawk and was hoping for some help.  Also posted this on rcgroups.

The issue is that when my speed controllers are hooked up to the Pixhawk they exhibit a bad sync issue.  However when they are connected to my old APM (3.1) or just a receiver directly they do not exhibit these symptoms.  This has resulted in 4 crashes now until I just tonight narrowed down the issue to the Pixhawk.

Can anyone advise what is going on?  Here are the specs of my setup:

Afro 30A ESC's with SimonK firmware (have tried all versions, and made my own with various parameters)

Tiger MT2216-9 1100kv motors

4S 3700mah battery

https://www.youtube.com/watch?v=i7_gVoY8q8M

https://www.youtube.com/watch?v=VTK81IANyUE

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    • I hate to say it but I think there is something peculiar about your setup, which is why we wanted to get a look at the entire system.  At this point we have no idea what is causing your problem, but as far as I know, you're the only one having it.  

      Changing the RC_Speed parameter... now that is odd.  Doing that will have some effect on the flight. How much?  Not sure.  But you shouldn't need to do that in any case.

      • I just registered so I could post about my issue and I think it is related to the motor sync issue with completely different hardware then the original poster.

        My setup is a Tarot 680P Hex.

        Motors: SunnySky 3508 580kv with 15 x 5.5 props

        ESC: ZTW Spider Opto 30A

        Pixhawk with ublox gps/compass

        I took it out today after getting everything setup and had set logging to default + IMU because I wanted to check vibrations also. I wanted to also try the auto tune. I took off from launch point and flew in alt hold over to a larger open area. Got up to about 15' and started auto tune. 

        While it was doing the roll tune I had to move it back in place a couple times but the one time I moved it, it went to start tuning again and it banked really hard right but caught itself and continued on. It sounded like a motor may have went out of sync but I can't be sure. It  completed the roll tune and started the pitch. I moved it back into position a couple times and on the last time it tipped back and upside down and hit the ground before I reacted other then dropping the throttle. It sounded like one or two motors went out of sync. 

        I am not sure what to do at this point. I had a Naza v2 which I sold when I bought the pixhawk. I didn't have any issues with the Naza. I would much prefer to stick with the pixhawk as I really like the features and the fact that it is open source. I don't know if I should rebuild the Tarot and try again the way I had it setup or try new motors and esc's. I have some afro 30a esc coming but they seem to be an issue as well. I know I am still frustrated at this point but I am basically ready to just sell everything and be done. 

        I am going to attach my log file, I didn't have it set to log the motors. Just default + IMU so I don't know if there will be enough info there or not.

        2014-04-13 08-34-13.kmz

        2014-04-13 08-34-13.log.gpx

        2014-04-13 08-34-13.log

        https://storage.ning.com/topology/rest/1.0/file/get/3702647045?profile=original
        • My Hex dumped in a week ago while doing Auto Tune and having Logging Default + IMU. Motors just seemed to stop after several tune oscillation sequences. I've looked at the Logs and it seems the Pixhawk just stopped sending signals to the motors. I'm not expert on Logs though.

          It was mentioned it might be a Buffer overrun and the Controller resets itself.

        • If you think the same problem exists then you need to narrow down the problem in a controlled environment.  Try my test with the quad strapped down and just one motor connected to the Pixhawk (prop needs to be on, so be careful), and see if you can get the motor to stall by moving the throttle from 0 to 100% instantly.  I have a throttle hold switch programmed on my transmitter, so I can flick it on, then move the throttle to max, then turn it off to instantly give full throttle.  In this test my motor will always go out of sync, well at least until I changed the RC_SPEED parameter to 100 anyway.

          Don't forget there are more normal things that can cause this problem.  For example, when I was initially troubleshooting this issue I removed all of the bullets from between the ESC's and motors to see if that would fix the issue, and I found one that had a cold solder joint from the factory and just pulled off.  So it's worth checking those things as well.

          • Cant you just buy some other ESC, not the cheapest you can find on hobbyking...Turnigy Plush is way to go...and than if you still have an issue, flash them with BLHeli firmwere(https://docs.google.com/spreadsheet/ccc?key=0AhR02IDNb7_MdEhfVjk3Mk...)

            you can adjust more important parameters...be sure you order new Plush with all NFets

          • I just got done doing some testing and have been able to rule out the pixhawk on this issue.

            I even setup the camcorder and was going to upload a video after a quick initial test with one motor and the pixhawk hooked up the motor would go out of sync just flicking the throttle stick. So I went and grabbed the camera and started recording and was able to get it to go out of sync pretty easy. 

            After that I needed to get my laptop hooked up and was going to change the rc_speed param but decided to try with the esc hooked directly to channel 3 on the rx. It did the same thing so I didn't worry about recording anymore. When it goes out of sync it sounds like a screaming banshee which is exactly what I heard when it went down.

            All the motors seem to be in good shape even after the crash. I think what I will plan on doing is trying the Afro esc's with these motors and see if I can get them to go out of sync without the pixhawk. If the prove good then I will try with the pixhawk. If it fails I will try changing the rc_speed param and try again. I just know I will be testing everything with it strapped down before anything goes in the air again.

            It is a little scary even with it strapped down on full power. Can't believe how much the carbon arms bend.

            • Well glad to hear you at least have some direction after your testing.  I think that test, where you try to induce motor sync issues with the prop on, should be a standard test before you try to get any new quad in the air.  Better it happens on the ground.

              It is a bit scary, even with my little 8" props.  I originally had them on upside down for testing and when I went full throttle in my basement it blew a few pictures off of the wall!

              • Then don't buy an ESC32 :)

                They have two calibration sequences that you do with the prop on, ramping up the motor between different rpm ranges. And if your parameters are unsuited to the motor, and it detects a desync, it screeches to a sudden halt so loudly that you'd expect to start searching around for blown motor pieces :)

                Otherwise, it's fun.

                • That sounds like a good idea....might look into those speed controllers.

          • I have a good bit of it torn apart but will put what I need back together so I can do some tests. Everything is hard soldered together and with the veer right and sound of out of sync motor(2) it did when doing the roll tune before crashing when doing the pitch tune and being different motor locations it does seem to be sync issues but without test data I can't be sure. I will try and get some testing done today and post up the results.

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