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Get IK using `ur_modern_driver`

asked 2018-04-12 02:58:35 -0500

prajval10 gravatar image

Is there a way to get Inverse Kinematics using the ur_modern_driver? Something similar to the UR Script function: get_inverse_kin(x, qnear, maxPositionError=1e-10, maxOrientationError=1e-10)

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answered 2018-04-12 03:06:41 -0500

gvdhoorn gravatar image

This is not functionality the ur_modern_driver provides. The driver is not a bridge into the VM that runs your URScript on the controller, but interfaces with the external motion and input/output capabilities of the controller.


A typical ROS approach would be to either use the services provided by MoveIt (if you're using MoveIt already, see Kinematic Model Tutorial for instance), or load an IK plugin directly into your application / script and use that.

trac_ik was recently extended with Python wrappers, see wiki/trac_ik. You could perhaps use that.

Another alternative could be KDL. There are both C++ and Python interfaces to that available, see wiki/orocos_kinematics_dynamics. Note that this may be slightly involved to get working, as it doesn't seem to have been updated much over the past few years.

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Thanks, however if I'd like to use UR inbuilt IK solver, I am publishing the following: pub = rospy.Publisher('/ur_driver/URScript', String, queue_size=10) query= "get_inverse_kin((10,150,100,0,0,0))" pub_command = "%s \n" % (query) pub.publish(pub_command) ...

prajval10 gravatar imageprajval10 ( 2018-04-12 07:05:50 -0500 )edit

... The function must return the closest joint positions. However, I'm not able to see anything on the topic /ur_driver/URScript. Is the topic just for sending commands?

prajval10 gravatar imageprajval10 ( 2018-04-12 07:09:10 -0500 )edit

Okay. Is there a workaround or should I set up a separate client-server application to access the IK solver?

prajval10 gravatar imageprajval10 ( 2018-04-12 07:11:22 -0500 )edit

You cannot do that. The controller does not return any results from statements sent to it over port TCP30002, TCP30003 or TCP30004. So the driver cannot return anything to you either.

gvdhoorn gravatar imagegvdhoorn ( 2018-04-12 07:11:52 -0500 )edit

There is no workaround, as the UR controller just doesn't return any results from URScript statements sent to it over a network connection. That is not a restriction of the driver, but of the controller.

gvdhoorn gravatar imagegvdhoorn ( 2018-04-12 07:13:17 -0500 )edit
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You could see whether creating a client-server application works for you. Note that the driver is also partly a URScript program, and you cannot run multiple programs on the controller, so you'll have to carefully manage those two.

gvdhoorn gravatar imagegvdhoorn ( 2018-04-12 07:14:25 -0500 )edit

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Asked: 2018-04-12 02:58:35 -0500

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Last updated: Apr 12 '18