Documentation of the head motors


I have several questions about the motors composing the head:

  • First, I did not find the documentation of these motors on the Reachy 2021 documentation web page. You mention a link to the documentation of the motors composing the arms but I did not find something similar for the motors composing the head. The only thing that I found is that these are DC Maxon motors, but that does not help much. Please correct me if I am mistaken, otherwise could you please make this documentation available ?

  • Second, what is the maximum speed of the motors composing the head ?

  • Third, on your documentation, you show examples of the turn off smoothly method. You use this method for the arms but not for the head. I suspect that the motors composing the head don’t allow to control their torque and thus don’t allow to implement the turn off smoothly method for the head. Am I right ?


Hi Romain,

You are talking about the motors of the Orbita mechanism used in the neck of Reachy, right ?

Indeed, we have not written the documentation about this part of the robot, and I think we should do it like we did for the arms.

Meanwhile, I can share to you here the spec of the maxon motors we use in Orbita. (1.2 MB)

To answer your questions:

  • We need to write the specification of Orbita and its motors in the documentation of the head part of Reachy.
  • There is a difference between the max speed of the motors and the max speed of th orbita mechanism.
    The max speed of the motors+gears with no load is 280 rpm, you can find all the info the the attached document.
    There is another gear in Orbita, so its max speed is lower than the max speed of the motors: 130rpm with no load. (since the gear ratio is 2.16.)
  • The control of orbita is different from the control of the dynamixel motors in the arms. The torque limit has not the same impact in orbita, so we can’t make a turn off smoothly method on the head with the torque control that would give good results.

Best regards,

Thank you Augustin for these clarifications, it helps a lot :smiley: