How to debug circle mode not circling?

I have my switch working right, I can see circle mode when I activate it, I can see it move servos on the ground, but very very little.
I have LIM_ROLL_CD cranked to 60 since it's supposed to mean bank angle of 20 (it gets divided by 3) for circling, but basically while I can see circling working on the ground when I tilt the plane, but once in the air, flipping the switch seems to make the plane fly straight away from me :)

Now, RTL does actually work. it brings the plane back to me and circles (although way too high despite ALT_HOLD_RTL lowered to 2000 (20m).

I tried auto calibration (brand new setup), and I'm not sure how well that worked. I did do the 25 left and right, and the up and down barely do anything. I can see the plane barely nosing up or down, but ever so slightly.

How can I debug this on the ground without flying? Is there a way to debug circling or RTL by feeding fake flight data and seeing what the plane does?
And from this description, could you guess what I might have set wrong to have circling not work?

Thanks,
Marc

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  • Moderator

    Can your post your Rate_P/I/D values here as often those being too low cause some of the symptoms you're seeing.

    Circle only maintains altitude and bank angle, no GPS position is used, so the aircraft will drift with the wind. Loiter is a better test as it should at least keep over a point. Also what is your Loiter radius set at?

    I generally use 35 degrees for LIM_ROLL in all my aircraft which is more than enough for a 60m radius loiter and fairly tight turns without very steep bank angles.

    How large are your ailerons and how much movement do they have?

    Flying in FBW_A is the best test to see if the aircraft will behave in any of the auto modes as it uses the same values but you send the commands not the autopilot. The flight response in FBW_A should be crisp and sharp in response to your inputs when the PID's are set correctly. Then try Loiter.

    It's odd that your RTL comes back so high, are you altitudes reported correctly otherwise?

    • Hi Graham, thanks for your answer.

      You were asking about my PIDs, this is what auto tune gave me. No idea how good they are, it's a multiplex minimag if that helps (smallish control surfaces) with a big 200W motor.

      Roll: P: 0.3 I: 0.02 D:0.02

      Servo Pitch Pid P 0.57 / I 0.03 / D 0.04

      Servo Yaw Pid Roll: 1, Int: 0 Dam: 0, Integrator: 15"

      Turn control period 25, Damping: 0.75

      Yes, I know that circle does not use GPS, although I didn't know about loiter, now that I do, I will try it out when I go fly next. Loiter defaulted to 60m, but I'll set it to 20 which my aircraft can do easily given the right aileron input. Note though that when I bank 60 degrees or more, I use back elevator pressure to tighten the turn, not sure if APM is smart enough to do that or not.

      I'm going to leave LIM_ROLL to 60 which means circle with circle at a mere 20 degrees (it divides that by 3, and I have no way to tell it not to), and I think my small ailerons ailerons (pretty stubby, they need a lot of deflection to have good effect) might also be why circle feels very sluggish.

      I'll try FBW_A once I have switches to let me do this.Right now I only have 2 switches: RTL and CIRCLE which will now be RTL and LOITER :)

      Altitude, I found I had ALT_HOLD_RTL at 10000 instead of 1000, that might be a problem :)

      I put it back to 1500 and will test it at my next flight. However my understanding is that APM initializes the barometer from GPS altitude when I power it on on the ground, correct?

      Thanks,

      Marc

      • Moderator

        I use:

        Roll: PID: 1.150 / 0.200 / 0.150 (35°)

        Pitch PID 1.200 / 0.150 / 0.200 (+17°/ -18°)

        ...which is not perfect but shows how high you can potentially go. This is on a Super Skysurfer at 800W max. I haven't done an Autotune yet but will try that soon.

        • Moderator

          After autotune on level 8:

          3702761273?profile=original

          • Sorry, I never got back to you, I had other problem with the plane, but basically your settings did help, so thank you for your help.

  • So I did more tests. It does circle, but the circle radius is so huge that it could go out of my view easily.

    I've tried increasing LIM_ROLL a bit more, but I can't really do that because this causes RTL to bank too much and stall the plane (which is understandable)

    I think I really only need a way to increase the bank angle for circle mode, and I'm not sure one can do that. Am I correct?

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