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Some questions on IMU (firmware 2.41b4)
  • zsntiancai
    Hi,
    When I open two IMU, the system is really stable in hand.
    But if the Camera Mount is put on the Copter, there is a big vibration. (I've done a damping.there is no High-frequency vibration)
    At the same time, I turn off the second IMU, the camera on copter become stable again.
    So, I think the vibration is come from Low-frequency vibration of copter.
    The second IMU is Too sensitive. It should have a function to filter some vibration.

    Another problem is that if the camera IMU is opened only, The larger angle, the more shake camera platform. Whatever how to config the value of PID, the problem remain.But if I open the second IMU this problem is solved.

    I feel very helpless, because I can not put the camera system on my copter.

    Regards,
    Bubble
  • Garug
    I would suspect the vibration dampening especially if you do not have much mass (like batteries) above the yaw, before vibration dampers.

    The problem is that the yaw motor, when moving and stabilising the gimbal moves the damper plate above the yaw easier than the relatively heavy and big inertia gimbal. The problem is also that vibration dampers do not usually resist well yaw rotation, they flex a lot and easily on rotation. That causes low frequency (below 1Hz) movement.

    Using IMU LPF might help.

    Is your frame IMU below or above the Yaw? That might affect too. It is a bit strange that you have this problem only if second IMU is activated. If it is above the Yaw, is it on the dampening plate or on the air frame. I would try Frame IMU on Airframe or below the Yaw. If on Airframe maybe good to add vibration dampening for the Frame IMU (adding IMU mass and attaching with two sided tape etc.)
  • zsntiancai
    Thank you for the help.
    I have tried "above the Yaw" and "below yaw". "Below yaw" is better than "above the Yaw", the Low-frequency vibration of camera is smaller. (But for the record , it is unacceptable.) I think the reason is it far from the Airframe.

    Yes, the second IMU is on the dampening plate, but the problem is the same as it on Airframe, because the IMU is very light, the dampening plate is ineffective. Also I have tried the two sided tape, maybe better, but the vibration is still exists.

    If I only use "the camera IMU", it's really stable in 2-Axis. When I open 3-Axis, the large angle have Low-frequency vibration.

    So, I think there is no "IMU LPF" fuction as you said.
  • Garug
    IMU LPF, I mean advanced tab, Sensor/Gyro LPF

    I do not think it is the IMU installation that is really the problem (though it might be part of it)

    The main problem I have had with 3 axis gimbal like you are describing has been that the yaw motor moves the gimbal dampening plate (the plate where the Airframe side of yaw motor is installed). This douses low frequency vibration.
  • zsntiancai
    Yes, it's really a problem.
  • Garug
    What is?
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