How to set Startup Torque On while also being able to use ros2_control

[alireza-moayyedi]

Hello,

My robot operates on sloped terrains and regardless of whether ros2_control is running or not, I want to have the torque always on. Otherwise it would just roll down if something crashes or if the ros2 stack is not up yet. I tried using the Startup Torque On configuration available in the EEPROM Area which indeed turns it on by default. But then the problem is that since the torque is on, ros2_control cannot initialize as it would not be able to set the any configuration in RAM:

I would have expected the hardware interface to be able to implicitly turn off the torque, apply settings and turn on the torque again. Of course that is also turning it off but then it would be rather quick.

So the question is, is there a way to set the torque on by default, while also being able to initialize ros2_control afterwards?

For context, I am using XH540-V150-R motors with Firmware version 49.

Looking forward to your help.

[Woojin-Crive]

@alireza-moayyedi
Hello!

Can you provide which control table items would you want to read and write?

Thank you!

[alireza-moayyedi]

Hello @Woojin-Crive ,

Thanks for your reply. I have multiple motors working in different modes. Here is a couple of examples of the gpio settings of two of the motors:

But may I ask why does that matter which control item ros2_control tries to initialize? Correct me if I'm wrong, but if the torque is on nothing can be changed on the motor and therefore, ros2_control basically would fail to initialize any gpio settings.

[Woojin-Crive]

EEPROM area control items could be written only when the Torque Enable is 0.
We cannot make sure that the DXL is always pre-configured, so we use param to configure the control table.
I think i can make an option to skip the torque disable check logic when 'InitTorqueStates'.
But you have to remove any of param tag of EEPROM area.

[alireza-moayyedi]

Hi @Woojin-Crive ,

I see. Thanks a lot for your explanation. I was under the impression that also the RAM area cannot be modified when torque is enabled but I was wrong then. Since EEPROM area params are in any case persistent and my motors remain the same in the hardware then indeed they can be removed from the gpio settings (after a first time manual configuration).

And if there would be an option to have Startup Torque On while also allowing ros2 control to write the RAM params on startup then that would be awesome!

[alireza-moayyedi]

Hi @Woojin-Crive,

I was wondering if there has been any update on this issue.

In the meantime I removed all the EEPROM params and now I can enable start up torque while also being able to use ros2 control afterwards. However, the problem then would be that upon shutting down ros2_control the torque gets disabled again.