Oposite motors change speed rappidly by themself ?

APM v2.5.4.

 I don't understand some strange motor behaviors.Maybe it's PID issue? Without touching or moving quad I could notice  two oposite motors slow down rapidly after few second. Quad tries to turn fast in Z axis.  It happen itself only under a half throttle value. I can compensate it for a moment with rudder stick, but then it happen again. I calibrated radio and all stick are definitely centered so what is wrong? (Stabilise Yaw P=3.0  I=0.05 )

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  • 1) Where can I find example of proper sensor calibration procedure , step by step ?

    2) After many  "blind" attempts  all motors work correctly but I don't know exactly which procedure helped. Should I do any tests in Terminal Mode or it's now unnecessery for good calibration?  

  • More likely than not, your wiring is contributing to magenetic drift so the compass thinks the machine moved when in fact it didn't. There are a lot of threads about this but the biggest problem wires are the ones from the battery to the power distro since they are carrying serious amperage to power all the motors. The suggested fixes are twisting the wires or otherwise running them far away from the APM board so as to not create a strong magnetic field. The reason why it's slow is that the code primarily uses the gyros and acclerometers first, but then corrects them with the magnetometer, so when  you go to half power, that's enough to throw off the magnetometer which purposely corrects the assumed orientation slowly through each loop of the main software.

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