Stabilization at high pitch angle
  • Hello, I'm having trouble with stabilizing at high pitch angle.

    I'm using SBGC 32-bit extended with two CAN-IMUs (main/frame)
    and latest GUI version(2.63 b0).

    Works fine with pitch angle under 60 deg, But it jitters when pitch is higher than that.
    So I carefully re-started the whole basic things(balancing, PID setting, etc.) but it was not the reason.

    Here's the thing :
    The gimbal is turned on, Yaw motor disabled, camera facing forward, stabilizing well within normal range of angle.
    When i carefully move the frame downward 80~90 deg, It is very unstable, but I can manage to handle that position somehow.
    In such a position, if I turn the frame with respect to the roll motor axis(it is yaw axis with respect to the main IMU), the roll motor does not move. I think in such a position, the roll motor should compensate the Yaw motion.. right ??

    I see other videos using Simple BGC, stabilizing well in 90 deg pitch angle. In 90 deg position, their Roll motors are compensating Yaw motions very nicely..

    What is wrong with mine ?
    Any help would be grateful..
  • Hello,
    System can properly distribute stabilization commands to motors when you tilt frame to any angle. But it needs a precise information about the frame's attitude relative to a camera. I guess that even if you connected 2nd IMU on a frame, it is not properly configured. Check that its orientation is set properly (use auto-detection), and it is working and calibrated.
  • Yes, I checked again, the frame IMU is calibrated and working fine, with correct orientation.

    OK, let me describe my situation more in detail. Now I'm testing with three axes. When pitch angle is around 45 deg, the whole system works nicely. Roll & Yaw motors are moving together, properly compensate yaw motion(outside point of view). But when the pitch becomes higher(near 90 deg), the jitter happens and the gimbal goes crazy.

    ... Now I've discovered that the gray(or white?) arrows in the gauge monitor does not move, for Pitch & Roll axes. For Yaw motor I've installed AMT203 encoder and so that is moving. Is this normal ? Maybe this is the cause of the 90 deg pitch problem?
  • Same happens when I pitch up the camera using virtual RC input, while the frame stays still on the ground. When pitch angle is close to 90 deg, the Roll & Yaw become crazy.

    Googling for a while, and I found a video which is very very similar to my situation. Link: https://sourceforge.net/p/brushless-gimbal-brugi/tickets/_discuss/thread/c29ee045/f08e/attachment/VID-20130626-00006.3GP
  • So I also made a video. Check this out:
    - I used virtual RC input to move pitch up to about 70~80 deg and the jitter happens.

    And also check this out:
    - Disabled Yaw motor and only Roll & Pitch. When I pitch up 90 deg, the Roll goes crazy. And then I pitch up even more to 120 deg, it become stable again.

    Looks like it is caused by some singularity problem, called "Gimbal Lock".
    But I think, as Alexmos said, this should be no matter if the two IMUs working fine & SimpleBGC algorithm working fine.

    As I said above, the gray arrows in the gauge monitor does not move, for Pitch & Roll axes.
    Maybe that could be a problem ?
  • ... Finally. I found out.
    Gray arrows were the critical hint.

    I was using firmware 2.63 b0 Extended + ENCODERS version.
    (because I was using AMT203 encoder installed in Yaw motor, there was no doubt that I can use that firmware)

    But the thing is, when I use ENCODERS version, the gray arrows for Roll & Pitch do not move because I'm not using encoders for those axes.

    When I switched to 2.63 b0 Extended REGULAR (no encoder) version, the problem solved. Gray arrows moving, stable pitching all around, including 90 deg.

    But one problem remains. In REGULAR version, Yaw encoder is supported, but AMT203 is not in the list. Is this not supported yet?

  • Hi! I have similar problem, when pitching gimbal goes crazy. How do I check do I have wrong version of firmware (I don't have any encoders). I have dys made 32bit controller with 2 imus, frame imu installed above yaw. When I pitch forward gimbal also tilts roll to right.
  • https://youtu.be/7oUSUUUDdLk there's video of it, sorry about the tv on background :D
  • Hi,
    I have same issue, when using ENCODER version and gimbal si pitched around 90°, it start going crazy, doesn't matter if Encoders are switch on or off. When using regular version gimbal works fine(tested on multiple verisons (2.60,2.63,2.68). So unfortunately I payed for encoders and encoder version of FW, but Im not able to use them.

    Will be some patch to fix this in near future, this is not fine.