AC3.2.1 APM 2.5 Throttle pulsates in Loiter


I have a problem after updating AC to 3.2.1 from 3.1.5.

When in Loiter, the the speed of the motors rev up and down/pulsate quite rapidly. This was working fine when I was using previous versions of arducopter.

I have downloaded the logs, and have looked into accX, accY and accZ. These seems to be inside the range specified in the wiki at arducopter. (Log_vibrations.bin)

Please have a look at the Log.bin, and note the difference between ThrIn and ThrOut when I'm in Loiter mode.


Anyone having any idea what the problem may be?



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    I ran the tests on APM 2.6 fw 3.1.5 and 3.2.1 with the same parameters, the result is that the firmware 3.1.5 are very stable in alt hold while the firmware 3.2.1 is very unstable, does anyone know tell me why?

    • Are you sure you do this test with the same vehicle and parameters?

      I think this is the most post that revealing thing about that there is a problem with 3.2.1 ,at least with the vibration filter code.

      I think the devolper team should think about keeping work on the 3.2.X branch to make it more stabilized

    • FW3.2.1 I solved by lowering the value of the parameter PILOT_ACCEL_Z FROM 250 TO 50 NOW is VERY STABLE IN FLIGHT and should not be more 'up and down

      • Have you been decreasing this parameter gradually or set 50 from the beginning? 

        Do vibrations on graph decrease or it just makes system insensitive?

        PILOT_ACCEL_Z - maxium acceleration used when pilot is controlling the altitude.

        Something tells me, that we can get issue on Auto missions. Do you have an opportunity to see how well it behave in Auto flight?

        Seems like I'll be flashing my quad twice a day :D

        By the way, while flashing 3.2.1 on MP 1.3.25 *4444 build at some point MP gets "Not responding", you need to know that process is still going on under the hood. Quite creepy moment :) 

        • I immediately set the parameter to 50 and hold alt works fine I do not know if there are problems in AUTO mode why not use it for aerial video

    • Have you tried setting MPU6K_FILTER = 20 as described earlier in this thread?  I think this is what solved the problem for me.

      • Here's the results:

        This firmwares feel pretty close, but IMO 3.2 is a bit smoother. Maybe 3.2.1 behavior can be tuned by adjusting throttle accel, I haven't tried yet. But out of the box 3.2. works slightly better.

        I have to mention, that it's weather change time here and slight side wind, like 1-3m/s no more.



        • the 3.2.1 is not quite perfect 3.1.5 is much more 'stable,moreover the 3.2.1 detects many more 'vibrations

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