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Thread: Overload error of Dynamixel XH430-V350

  1. Overload error of Dynamixel XH430-V350

    Hello, I am encountering a trouble in using Dynamixel XH430-V350.

    When a large load (e.g. PWM>600) is continuously applied to the servo in, for example, 10 seconds, the servo shutdowns with an overload error. We can disable the shutdown by modifying the control table of SHUTDOWN, but even in that case, the HARDWARE ERROR STATUS is set to overload.

    This is strange to me since the limit of PWM of this Dynamixel is 885 from the manual. This phenomenon happens even if I change the PWM Limit to 700. When PWM Limit is 500 of below, this phenomenon does not occur, but it is very weak compared to the maximum torque of the servo.

    Note that this overload error does not disappear even when the large load is removed (I need to reboot the servo).

    I wonder if this hardware error would REALLY damage the servo. Does someone have an idea to keep using the servo at large power? (like PWM=800)

    Many thanks!

  2. #2

    Re: Overload error of Dynamixel XH430-V350

    PWM limit is how much PWM the servo will apply at most.
    Meanwhile, "overload" means "the servo applied a large enough value for long enough that we think the servo is stalled."
    The reason the servo shuts down is that it needs to avoid over-heating, which will damage the motor of the servo.
    If your load is large enough to stall the servo, you are overloading the servo. it makes sense that it's protecting itself by shutting down.
    If you want to prevent shut-down, detect the stall (by polling the position, and detecting that it's stalled for, say, 500 milliseconds, and telling it to hold position instead.)

    You can use a large power for a small amount of time (seconds.) However, these servos, like all brushed motors, are generally designed to be run at an average of 1/5 of the maximum stall load. This either means running with 1/5 duty cycle at full load, for short enough time that it doesn't overheat, or running at 1/5 the max torque, on average, over a longer time.

  3. Re: Overload error of Dynamixel XH430-V350

    Thanks so much for your answer!

    > "the servo applied a large enough value for long enough that we think the servo is stalled."
    This is ambiguous to me... For detecting this, we would need a threshold PWM (like 550?) and a threshold duration (like 5 seconds), but such values are not defined in the control table. I want to know these values since I also want to use PWM or current control modes.

  4. #4

    Re: Overload error of Dynamixel XH430-V350

    The threshold is the maximum PWM value. I e, "overload" means "servo tried to drive at max PWM for too long and didn't get where it was going."

    If you apply "almost max PWM" but are holding at where you're supposed to be, the next thing that will trigger is the overheating shutdown. That one's more dangerous; you typically need to shut the servo down and wait for 20 minutes before you use it again if overheating. Some servos (MX-64) will overheat so much that they die if you run them at the max rated voltage (4S LiPo) into stall; they will kill themselves before either overload or overheat kicks in. I haven't used the XH/XM ones, so I don't know how they fare in this kind of torture. (Recommend using lower voltage, and perhaps also configuring a lower max PWM for safety, especially while developing.)

  5. Re: Overload error of Dynamixel XH430-V350

    I got your idea. I understand a good way is following your advice: not using servo with large PWM (800 or some) for long term (5 seconds or some).
    Thank you so much!

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