ros_control: Using an existing interrface

[Marius]

Hi everyone,

I want to change an existing hardware interface of the KUKA youBot so that I can use it with ros_control. This procedure ist explained in ros_control wiki.
The existing youbot_driver_ros_interface interfaces the youbot_driver to ROS.
My problem is that I have no idea how to change the existing interface to the structure described in the tutorial in the link above.
The current joint interface looks like this: 

topicName.str("");

topicName << youBotConfiguration.youBotArmConfigurations[armIndex].commandTopicName << "arm_controller/position_command"; // e.g. arm_1/arm_controller/positionCommand

youBotConfiguration.youBotArmConfigurations[armIndex].armPositionCommandSubscriber = node.subscribe<brics_actuator::JointPositions > (topicName.str(), 1000, boost::bind(&YouBotOODLWrapper::armPositionsCommandCallback, this, _1, armIndex));

(URL to code)

and I want to have something like this:

hardware_interface::JointHandle pos_handle_a(jnt_state_interface.getHandle("A"), &cmd[0]);
   jnt_pos_interface.registerHandle(pos_handle_a);

like in the link above.

Is there a simple way to do it?
Any ideas?

BTW: There is a gazebo simulation for the youbot which uses ros_control (youbot_simulation). In this simulation the "hardware-interface" is realized by an URDF transmission file which works with an inbuild default hw-interface in gazebo (gazebo default interface). At least, this is how I think it works.

I've been working with ROS/MoveIt! for the last few month but I havn't used ros_control yet an I can't find any other tutorials.

Any help is much appreciated!

[Michele Mambrini]

Hi Marius, 

Some months ago I encountered the same problem. You need to develop a fake ROS:Hardware_Interface that works as medium layer between the KUKA youBot and one controller of the ros_control package. I found a useful bachelor thesis, completely shared on Github that helps me a lot (https://github.com/kaffeesiader/bachelor_thesis) . In addition to the thesis, the author, Martin Griesser, has shared also the package developed on his own to provide a fake position interface  to work with a Kuka Lightweight and Ros Control (https://github.com/kaffeesiader/uibk_moveit_adapter).

I'm quite sure that it is what you are looking for. 

[Marius]

Hi Michele,

this looks indeed pretty good. Thank you for the hint!
What kind of robot did you work on?

Cheers

[Marius]

I realized that one important difference to the suggestion with the fake hardware_interface is that the youbot interface already uses the FollowJointTrajectory topic directly. So what I want is that for example MoveIt! sends a FollowJointTrajectory command to a ros_controller and the ros_controller sends a command to the joints via a hardware_interface. So instead of using an adapter I have to change the youbot interface so that it doesn't receive the FollowJointTrajectory command directly.

Is this correct?