Just can't get yaw to work

Ok, so need some assistance with tuning yaw - see the attached vid (you won't need to watch more than a minute or two to see the problem. You can ignore the pitch issues which I'm addressing via the gimbal PID's.

Basically, I can't get the damned thing to fly straight without the nose bouncing around. Speed doesn't seem to matter - loiter or high speed, the bouncing is the same.

But it appears yaw can't be tuned the same way as pitch and roll - I've tried:
- detuning P (to 0.1)

- uptuning P (to 0.35)

and various settings inbetween.

I've also tried combining it with Stab Yaw as well - from as low as 4.5 to 9.5. And tried doing some I tuning, but it didn't really seem to have any effect.

If I detune it, it just bounces left/right slower, and has a lot of overshoot. If I tune it up, it bounces less, but more more quickly.


Where should I be tuning? Should I even look at D to control the overshoot?

I redid the compass calibration at the field before I shot this video. Compassmot is 9%, and I have tried running with and without it enabled, and it makes no difference. All motors are perfectly aligned, and seem to be running normally. Running APM2.6 and 3.1.5

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Replies

  • So are you relying on the supplied tools only, or do you know anything about PID?

    I think you should understand PID first, try Wikipedia.

    In general, you would want to have D low, almost 0, I also low, but sometimes it helps, and P is the one that makes the fastest moves, because it is simply P, which is proportional to the difference between set point and actual point.

    Your overshoot is being caused by I or D, but most likely I because it takes some time for the Integration to accumulate, and then it will oscillate. Cmon R&D.

    If you want it to be as smooth as possible, try a low or medium P setting, no I , no D. And get back to me, if you care.

    • Lol - did *you* read it?

      Answer me this mr PID-expert-who's-annoyed-I-critised-his-airframe-design...why is there no D on yaw in arducopter, and why in most craft is it not needed.

      • Because you don't need to use any differential feedback for small craft with good response.

        If it was a larger craft the inertia of moving would cause it to overshoot which is why a negative D is added, to reduce the speed as it approaches the target point. I went through 2 years of just PID.

        • So if there is no option for D,

          this assumes you are moving a small mass, and that you need to keep P low.

          I (integral) can help if there is any sensor offset or drifting.

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