Overload error while measuring low current

Technical Support
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1

Issue:

We have a XH540-W270 with minimal current (not even half of the current limit (measured with an external accurate current clamp and oscilloscope) getting an Overload Error in position mode. There was no motor movement so no load peak should be expected.

  1. Is there a way to get further documentation of the Motor in general and the error specifically?

The explanation i found online does not explain the duration of the over current that would lead to this error.

  1. Would this error also happen if the target and actual position differ enough?

  2. Is there a way to get expert documentation on all dynamixel motors (we use multiple types)?

  3. What is the error behavior if i disable the shutdown for the overload error?

  4. Could it be a workaround to use the CurrentPosition (application is the third axis of a 6 axis robot arm)?

  5. Is the reboot (using DYNAMIXEL Protocol 2.0 Clear register) function also available for the XH540-W270 or only for y series motor as stated in the linked documentation?

Thank you

DYNAMIXEL Servo:

XH540-W270

DYNAMIXEL Controller:

U2D2 with ROS2 Humble, MoveIt

Software Interface:

U2D2 with ROS2 Humble

2

  1. Complete documentation for all DYNAMIXEL servos is available on ROBOTIS’ online manual.

  2. That could be a possible explanation, if the servo is unable to complete a movement and ends up in a stall that would trigger the overload condition.

  3. The online manual documentation is the most comprehensive documentation publicly available for DYNAMIXEL servos.

  4. The servo will still log an overload condtion, and the LED will still start blinking, but the servo won’t release torque and will continue operating if possible. However, this runs the risk of allowing the servo to overheat and damage itself if operated in stall conditions.

  5. A workaround for what in specific?

  6. The function to clear errors for X series servos would be the Reboot instruction, on X series servos Clear just resets the present position.

3

Thank you for your help!

  1. is there a way to increase the maximum position difference before the error is triggered

  2. Would the over-temperature error protect against overheating and damage to the motor.

  3. We are using the motor as a third axis for a six axis robot arm. If We use the currentBasedPosition mode if the goal current is reached the arm would just not reach the target position but would not trigger the overload error.

  4. Would you recommend that we disable the shutdown for the overload error if we keep the temperature shutdown enabled?

  5. Do you have any other ideas or recommendations?

4
  1. Not for our X series servos.
  2. The over temperature protections will still function, however since the temperature protections don’t activate until heat has already built up, they may not prevent damage as even short periods of elevated temperature can cause damage to the unit.
  3. That would actually be the intended use case for current based position operation. I would recommend this approach if possible, you can adjust the allowable goal current to increase the force allowed to approach the goal position.
  4. I would recommend keeping all shutdown statuses enabled unless you absolutely need to disable them, to avoid possible damage to your servos.
  5. I would recommend the use of current based position control for this application, it’s well suited to the type of cobot-style robot it sounds like you’re building.
5

The current based position mode still results in overload error… same error behavior.

8

Would you be able to share a photo/video of the issue occuring in your setup? I’d like to see what the motion looks like before the overload error triggers, in case that helps me figure out how to avoid it.