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sanida hand grasp controllers

asked 2013-02-07 10:37:03 -0500

pbeeson gravatar image

Is the SimpleGrasp controller used on the DRC Tutorials page supposed to an API for grasping that will be used in the VRC, or is it just a demonstration on how we might write our own controller to send JointCommands to the hands? It is unclear whether I need to write my own, or (supposing this is sufficient for VRC tasks) whether I can rely on this service being run during the VRC.

If this is just an example, then it would be very helpful to explicitly state this in the tutorials so as to not cause confusion. We are still in recovery mode after the dropping of the FollowJointTracjectoryAction controller, and I don't want to have to do the same if/when the grasp controller goes away.

Thanks.

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I would like to know what the pre-determined grasp shapes are. I can't find this in the API, and have no idea how to find this out with an 'info' or 'echo' command.

DRC_Justin gravatar imageDRC_Justin ( 2013-02-07 13:24:36 -0500 )edit

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answered 2013-02-07 14:41:00 -0500

mquigley gravatar image

updated 2013-02-07 14:55:50 -0500

The simple_grasp controllers were purely intended for demonstration, just to show the hands moving in the simulator. Presumably the grasp controllers would need to be much more sophisticated to accomplish the range of tasks of the VRC. Importantly, real grasp controllers would likely need to use more features of osrf_msgs::JointCommands messages (e.g., torque limits).

The source for the simple_grasp controller is here. It's pretty short. It just does a minimal eigengrasp implementation of a few canonical grasps: cylindrical, spherical, and prismatic.

I have updated the wiki to clarify that this is only a strawman implementation for tutorial purposes.

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answered 2013-02-07 14:20:14 -0500

hsu gravatar image

updated 2013-02-09 14:15:24 -0500

Nodes used in tutorials such as the simple_grasp.py nodes is a demonstration and may change over time. But the underlying ROS API as specified in the DRCSim User Guide will be supported throughout VRC. We'll try our best to keep the set of interfaces as stable as possible.

We dropped the use of PR2 style controller manager given we are trying to mimic controller interface on the actual Atlas robot. One can wrap the functionalities of gazebo_ros_controller_manager into a library invoked through a standalone ros node and still be able to use the functionality offered by pr2_controllers and pr2_controller_manager (e.g. FollowJointTrajectoryAction controller).

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I understand why you did this, and I've already got a dropin replacement for the FollowJointTrajectoryAction controller. I just needed to know whether I just spend time doing the same for grasping. Looks like I do. Thanks.

pbeeson gravatar imagepbeeson ( 2013-02-07 16:37:39 -0500 )edit
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Asked: 2013-02-07 10:37:03 -0500

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Last updated: Feb 09 '13