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Family of X_controllers/JointGroupYController using PIDs
Greetings fellow ros-controllers,
I was wondering if there is interest in having grouped controllers that plug to type X joint interfaces while accepting commands for type Y joint interfaces.
These would be useful for robots that are homogenic in their joint interfaces (Effort, for instance) but need to be controlled in some other manner (eg: Position, to keep straight, or Velocity to keep a fixed speed) in cases where the hardware abstraction layers cannot be fiddled with.
Last week I took effort_controllers/JointPositionController and combined it with forward_command_controller/ForwardJointGroupCommandController. My effort_controllers/JointGroupPositionController can be found here:
https://github.com/bmagyar/ros_controllers/blob/position-effortgroupcontroller/effort_controllers/src/joint_group_position_controller.cpp
My current implementation is nowhere pretty nor generic, but it works. For example it gets the Valkyrie do these funky moves: https://www.youtube.com/watch?v=tLCpJvqgtRQ
Your input on this would be much appreciated, thanks!
I don't think that we at IPA have the need for these controllers at the moment (@ipa-fxm: ?), but it might be useful for others. Most of your code could be moved into a common template. In addition https://github.com/ros-controls/ros_controllers/pull/187 might help.
IMHO the limit enforcing should be done by the RobotHW implementation.
Perhaps it would make sense to implement a chaining mechanism that would add PID controllers to all controllers. I am going to try this with joint limits filtering. (https://github.com/ipa320/cob_control/issues/72)
I thought our current controllers already convert, say, position commands to, say, effort commands? What does this group controller feature do differently?
The forward (group) controllers do not convert, they pass all data directly.
The only thing this controller adds compared to effort_controllers/JointPositionController is grouping.
For further improvements I can remove the joint limit enforcing and I was also thinking about making it templated over the "Command" and "Output" types.