Motor pulsing in Altitude Hold

Just an annoying problem with the motors pulsing in Altitude Hold.I don't seem to be able to tune it out entirely. I've disabled the Sonar. The Quad holds altitude quite well but the pulsing upsets the stability a little.Also I'm using 12x8" APC props. Could these be to 'aggressive'? I will be trying 13x5.5" later this week hoping to get smoother thrust.

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  • All my APM 2.6 and older tricopter and quadcopters are having the same problem. However, on my quad copter when I removed the gimbal and camera, the problem was gone. I though maybe there is some electric interferance, so I installed the camera and gimbal but let them unplugged (no power), and the problem came back. Thanks I removed the camera and gimbal and the problem was gone. I figured it is the weight. So Just to confirm, instead of camera gimbal i installed similar weight (extra battery that was unplugged) and the problem was back again.. I have concluded that it is the excessive weight that is beings in the problem. However, I am not sure what parameters to change to fix this behavior.


    Please share if some one know how to fix it. Thanks.

  • Hi all, 

    I have almost the same problem.

    It looks like this: Setting: APM 2.5, APM 2.9.1b, RCTimer Motors 2830/14, 750kv (also testing Sunnysky 2212, 980kv, but same problem), HK F-20A SimonK ESCs, TBS Discovery Frame, 3S, 10" Props, Ublox GPS, 3DR Radio.

    After wasting several ours with pid tuning, I have no idea, what to do. 

    Maybe it could be a problem of vibrations or compass offset? 

    I would be happy about every hint. 




  • Do you have those bullet connectors along the wiring between ESC and motor ?

    My experience with these (on gen 1 ArduCopter) was intermittent bad connectivity
    that resulted in intermittent motor glitches. By soldering up the connectors solid
    the twitching was gone. Just 2 cents.

    Else a wild guess could be specifically in altitude hold mode that the software
    access some ports in a way that happen to affect signals related to motor PWM output. Can be a debug issue that for resolving requires intimate knowledge of the processor registry and PWM timer functionality.

  • What motors (kV) are you using with these props? How many cells in your LiPo? It sounds very much like the motors are hunting, rather than a direct response to a control loop instability.

  • Hi Warren

    That's quite an aggressive prop!

    I'm using 12x5" carbon reinforced props and I thought that it would be too aggressive.  They seem to be doing ok though.

    I'm just speculating here.....  It could be that with such an aggressive prop the motors are working too hard to catch up with the requirements, but, when they do it's too late so they slow down too quickly and the cycle starts again?

    You could try some less agressive props to try to 'smooth things out'.


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