Active Damping Configuration

[Emmanuel]

Hi,

 

I have been attempting to modulate the Sawyer's impedance parameters in a real time manner, during trajectory execution. Although the algorithm is functional in terms of active stiffness regulation, it precludes modifying the active damping values in an analogous fashion, since the simultaneous impedance-trajectory tracking control relies upon the 'InteractionOptions' class. Is there a means of setting the damping matrix elements to desired values? The rationale for excluding this feature from the 'InteractionOptions' class is slightly unclear, given that the 'InteractionControlCommand' class could be utilised for the same purpose, albeit being unsuitable for trajectory execution.

 

Best regards,

Emmanuel

[Shiwei Wang]

Hello Emmanuel,

Thank you for using the interaction control feature! For your question related to damping value,  the interface itself is designed not only for the SDK user but also the general user,  to avoid confusion we set the default value of damping internally.

We calculate and set the value based on stiffness and the damping value will not exceed [8.0, 8.0, 8.0, 0.5, 0.5, 0.5].

We do not provide the interface in SDK but you can send a command to set the damping value, the message file locates at:  

intera_common/intera_core_msgs/msg/InteractionControlCommand.msg 

and you can also echo the rostopic to see the value of damping: 

rostopic echo /robot/limb/right/interaction_controller/state

Hope this helps.

-Shiwei

 

 

[Emmanuel]

Hi Shiwei,

 

Thank you for the reply.

 

I have already experimented with modulating the active stiffness and damping values via executing the "intera_common/intera_core_msgs/msg/InteractionControlCommand" topic, through a terminal.

The real quandary is regulating the active damping in a real-time manner, whilst executing a trajectory, or set-point path. One would naturally anticipate that since it is possible to define the robot's interactional behaviour by using commands such as the following:

set_K_impedance

set_max_impedance

set_force_command

set_K_nullspace

set_endpoint_name

 

then it should also be possible to utilize 'set_D_impedance', which however consistently returns an error. It would be beneficial to offer the user the option of defining the active damping parameter, which would endow the robot with the desired dynamical behaviour/response, i.e. over-damped, critically damped, and under-damped. This is clearly a concern when transitioning between different proportional gains.

 

Kind regards,

Emmanuel