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[Unitree A1] Motor can't be controlled anymore

The rear left hip motor of our Unitree A1 can’t apply any torque. The motor is much harder to move compared to the other hip motors when the robot is off. The robot is able to boot and stand up sometimes, but it can’t walk because the rear left hip motor only has some resistance and can’t move on its own.

In the system report, there does not seem to be anything wrong. The motor even reports its position correctly. But when we send commands to specifically only move the problematic motor, we can’t detect any reaction, like a different sound or a weak movement.

// ********************************************************** // 
 Motor lose connect ([ ]/100ms): 
FR    0    0    0  ;     1    0    3 ; Joint->  0.1336   0.4971   -1.7023  
FL    0    0    0  ;     1    0    3 ; Joint->  -0.1307   1.3370   -1.7998  
RR    0    0    0  ;     1    0    3 ; Joint->  0.2436   0.8991   -1.8069  
RL    0    0    0  ;     1    1    3 ; Joint->  -0.6251   0.8675   -1.8062  
IMU        ::  Roll = -0.8739, Pitch = 1.1370, Yaw = 10.6796 
Foot Force ::  [FR_] = -1.06, [FL_] = -1.70, [RR_] = -20.86, [RL_] = -5.18  
GamePad CMD::  0.00, 0.00, 0.00, 0.00 
RobotVersion     = 400  
Firmware_version = 1000200525  
HardwareVersion  = 1000200420  
// ********************************************************** // 
 Motor lose connect ([ ]/100ms): 
FR    0    0    0  ;     1    0    3 ; Joint->  0.1336   0.4971   -1.7023  
FL    0    0    0  ;     1    0    3 ; Joint->  -0.1307   1.3370   -1.7998  
RR    0    0    0  ;     1    0    3 ; Joint->  0.2437   0.8991   -1.8068  
RL    0    0    0  ;     1    0    3 ; Joint->  -0.5187   0.8675   -1.8062  
IMU        ::  Roll = -0.1846, Pitch = 2.1050, Yaw = 10.9749 
Foot Force ::  [FR_] = -3.56, [FL_] = -2.20, [RR_] = -22.36, [RL_] = -5.68  
GamePad CMD::  0.00, 0.00, 0.00, 0.00 
RobotVersion     = 400  
Firmware_version = 1000200525  
HardwareVersion  = 1000200420  

We are now wondering if the motor needs to be replaced or if this issue can be fixed in a different way. If there is any other info that we can provide or things we could try, feel free to let us know. We would be thankful for any advice!

Dear Felix,

thanks for reporting an issue.

Could you please do two small things:

  1. Could you please upload a short video how the robot is standing up/falling down so we are having a better understanding what’s happening?
  2. Could you please move both legs and report if you feel any differences in the behaviour?

If we don’t find any solution, most probably we have to send you a new motor.

Thanks for the response!

Here is a video of the robot trying to stand up. Today I couldn’t get it to stand up entirely, but I think this is enough to see the problem. The rear left leg slides outward because there is no torque from the hip motor and then it can’t stand up properly anymore.

The hip motor of the rear left leg requires a lot more force to move and isn’t as smooth compared to the other hip motors. This resistance is probably also the reason why it could stand up sometimes while the motor doesn’t work.

I hope this was helpful.

@felix, thanks for the video.

If you would like, we can ship you a motor as replacement so you can check, if it is solving your issue - Should we do so?

Yeah that would be great! I’ll send you the address directly.
Will we need to configure the new motor before replacing it?

Dear Felix, received, thanks a lot!

Yes, all A1 motors have to be configured with an ID between 0-2

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