Forums Niryo One Troubleshooting Suggest reduced calibration

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  • FindingNiryo
    Participant
    Post count: 105

    Since each joint has an absolute position encoder it seems calibration (home position to zero joints) should only be needed once to correlate arm physical limits to software position indicators. Physical homing should not be required every time CAN/DXL start hardware control loop is called. Specifically following a bus restart from CAN connection problem should not require homing joints.

    Edouard Renard
    Keymaster
    Post count: 239

    The trick here is that the encoder are “partially absolute”. What does it mean: axis 1, 2 and 3 all have a gear ratio, so if you want to make one complete turn on the axis, you’ll have to make multiple turns with the motor.

    So, when the communication is lost/robot is reboot, you need to calibrate the axis with NiryoStepper, so the robot knows how many motor rotations (+ the absolute offset that we calculate with the first auto calibration) is the correct offset.

    After doing one auto calibration, you can use the manual calibration which is much faster. I hope the explanation is clear!

    FindingNiryo
    Participant
    Post count: 105

    Ah, of course! I hadn’t considered the gear reductions. Thank you.
    Looking to minimize the human interactions with the robot I would still like to avoid calibration if possible.
    Suppose the reported position for joints is not significantly different than before the bus is reset it would be safe to assume that the positions were correct and that calibration was not needed.

    • This reply was modified 5 months, 1 week ago by  FindingNiryo.
    FindingNiryo
    Participant
    Post count: 105

    Stepper #1 is the worst case scenario as far as multiple rotations (each rotation has a chance to return the same absolute position code).
    V2 stepper_1
    Gear Ratio 6.0625
    Min angle -3.05433
    Max angle 3.05433
    radians 6.10866
    rotations 5.894104573

    If the last known position is within +/-.011757 radians of the current position there is a 98% chance the joint has not moved and does not need to be recalibrated to establish joint position.

    • This reply was modified 3 months, 2 weeks ago by  FindingNiryo.
    • This reply was modified 3 months, 2 weeks ago by  FindingNiryo.
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