How bad for the motor is it to turn when powered off?

Technical Support
1

DYNAMIXEL Actuator

Thinking of using XC330 or XC430.

Issue Description

We would like to know how detrimental to the motor it would be to turn it when it’s powered off?
We are going to build a game where there is some string attached to a reel on the motor which can be pulled as normal, but then something my give a pull back when we turn the motor on. Is this dangerous for the motor?

2

What do you mean precisely about power on/off? Do you mean that the Input Voltage to the actuator is 0 V? Or do you mean that you set Torque Enable (Address 64) to On/Off?

3

As Roboteer mentioned, the answer might differ depending on exactly what you mean by “powered off”. However, in general, back driving like this is safe for the motors provided you keep a few important considerations in mind:

  1. If you intend to have the motor fight against the force of a user pulling on the reel then it’s important to ensure that you don’t overdrive the motor or cause a stall condition.
  2. Quickly trying to switch directions or suddenly applying a high resistive force puts a lot of instantaneous torque on the gears and motor. It’s best to change directions or adjust resistance gradually to prevent damage.
  3. Especially with X330 sized servos, high speed back driving can cause voltage spikes that might cause damage to electronics. If possible, try to prevent users from turning the motor very quickly by hand.
2 Likes
4

Okay, good info.

And when I say off, I mean torque disabled until I want to reenable it to have resistance on a string for the player.

5

Given what you are trying to accomplish, I think looking into compliant servo motion through the use of current control mode on the XC330 would be your best bet.

6

The motor continues to rotate for a long time even when the power is off/motor pin is short. When I saw your idea about the game it seemed very interesting. To my knowledge, it is not dangerous to start the motor when the power is off. When I learned MuleSoft Course, I got basic info about torque enable or disable function.