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which rostopic should 3rd part controller publish to, to control a real Universal Robot?

asked 2019-02-14 11:09:55 -0500

porkPy gravatar image

I am attempting to control a UR5 robot arm using a neural network controller. With the minimum amount of reconfiguring, to which topic should the joint commands from the neural network be published? The network output will be a tuple of joint movements of +/- 1 degree. How could I test such a publication message using the command line? This is using ROS Kinetic. Thanks, Dom

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answered 2019-02-15 05:07:49 -0500

gvdhoorn gravatar image

updated 2019-02-15 05:33:34 -0500

Provided you are using the kinetic-devel version of ur_modern_driver and provided you are running your network at 125 Hz and you make sure to not violate any limits, you could make use of the ros_control compatibility, configure a JointGroupPositionController, keep track of the absolute joint angles and publish new targets to the position controller.

Alternatively: use the JointGroupVelocityController that's already there and publish velocities.

Another alternative could be to use something like jog_arm between you and the driver. It can take care of some of the steps I wrote about above.


which rostopic should 3rd part controller publish to

just an observation: all controllers would be "3rd party" in this setup. I'm not sure what would make yours different from any other.

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Hi gvdhoorn, Thanks for your answer. I have managed to get jog_arm to start publishing to /move_group. I have worked out (I think) how to publish actions to the /jog_arm_server node using the /jog_arm_server/joint_delta_jog_cmds topic using the /jog_msgs/JogJoints message. .....

porkPy gravatar image porkPy  ( 2019-02-18 08:46:50 -0500 )edit

Example: $ rostopic pub /jog_arm_server/joint_delta_jog_cmds jog_msgs/JogJoint -1 '{stamp: now, frame_id: base_link}' [wrist_3_joint] [10]
and I get output publishing and latching message for 3.0 seconds However, the robot does not move. Any ideas? Many thanks

porkPy gravatar image porkPy  ( 2019-02-18 08:49:25 -0500 )edit

If I echo the joint_delta_jog_cmds topic I get an output of:

header: seq: 1 stamp: secs: 1550500372 nsecs: 132920026 frame_id: "base_link" joint_names: [wrist_3_joint] deltas: [10.0]

porkPy gravatar image porkPy  ( 2019-02-18 08:54:15 -0500 )edit

I would recommend you ask the jog_arm author, @AndyZe. Either here on ROS Answers or in an issue on his tracker.

gvdhoorn gravatar image gvdhoorn  ( 2019-02-18 11:08:49 -0500 )edit
AndyZe gravatar image AndyZe  ( 2019-02-18 16:34:24 -0500 )edit

Ok, will do. Thank you for your help.

porkPy gravatar image porkPy  ( 2019-02-18 16:35:21 -0500 )edit

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Asked: 2019-02-14 11:09:55 -0500

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Last updated: Feb 15 '19