Motor position going out of range even if motor is held in place about moteus

[jpieper]

Great, I'll close this out then. Come back if you have more questions, or join the mjbots discord! https://discord.gg/W4hUpBb

[kibidev]

Tested with FW versions:
20220501-moteus-0965b28edd417f4e935f87d1ad40a607093d816f.elf
20220730-moteus-75df0139aaf6e76f207dffae17b81b39f3d5d5ce.elf
20220803-moteus-26e636ddb36b702a361291b0ab842acd881f281b.elf

Tested on HW model 800 and 700.

[jpieper]

If understand correctly, I believe that is expected behavior. Your options are to either:

1. Set a finite servo.max_position_slip as documented in the reference manual section on velocity control: https://github.com/mjbots/moteus/blob/main/docs/reference.md#velocity-control

2. Disable the position limits, as they are rarely useful for velocity mode applications anyway. They can be set to nan to disable them completely: https://github.com/mjbots/moteus/blob/main/docs/reference.md#servoposposition_min

[kibidev]

Thank you for a quick and helpful reply!

I have set servo.max_position_slip to 0, and it seems to fix the problem.
It there any other behavior change I would need to be aware of when changing this from nan to 0?

[jpieper]

If you have the kp term set to 0, then setting servo.max_position_slip to 0 will have no other effect. However, the combination of those two means that the velocity control has no effective integrative term, and in steady state the velocity will never match the control velocity in the presence of an external torque. If you need the velocity to track accurately, you should use non-zero values for both. The kp will control the "velocity integrative term", and the max_position_slip will control the integrator windup limit.

[kibidev]

Great, thanks again.
Accurate velocity is not important in our application, so it should be good like this.