Emergency Stop System Implementation

Hi, Let’s say:

  • I’m connecting my dynamixels with u2d2 to my laptop pc on my robot,
  • I have an emergency stop button connected to my micro controller,
  • I have a relay on the power line to the motors that is controlled by my micro controller.

And I cut the motor power when emergency stop button is pressed.

After estop button is released and power came back to motors:

  • Do I need to unplug u2d2 from pc and replug back?
  • Or just reset the tty connection in pc?
  • Or does it just function well when the power comes back?

I’ll also stop sending commands from pc when estop is pressed. But I want to be sure that the system is safe.

Hi, each DYNAMIXEL has its own microcontroller in it and you can think it as a separate module from your controller or PC.
Since U2D2 is only work as a communication interface (translates between serial and USB), you don’t need to reconnect DYNAMIXEL after power switch.

For the emergency button implementation, you can simply cut off the power to DYNAMIXEL for the safety and when supply the power when it is safe.

However, please be aware that when DYNAMIXEL is turned on, data in the RAM area such as Profile Velocity and Profile Acceleration, PID gains will be reset to default value as well as Torque Off by default.
If you are using Extended Position Control for multiple rotating application, internal rotation count will also be reset to 0.

All in all, to answer your questions,

  • You don’t need to unplug and replug DYNAMIXEL from U2D2 after power reset.
  • Don’t need to reset tty connection if U2D2 is kept connected to your PC via USB cable.
  • Just allow some time for DYNAMIXEL to boot before use. 10ms should be fine. and Don’t forget to turn on the Torque :slight_smile:
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