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Joint space trajectory control (MoveIt)

asked 2016-02-22 01:53:47 -0600

Joska213 gravatar image

Hi,

I have a question about MoveIt and its capabilities: I have a robot which only can be controlled by joint poses (6DoF). Well If I'm trying to use MoveIt it generates the joint poses and velocities too. My problem is that I only can control the robot with joint poses, so I cannot send it velocity parameters. If I only send the joint poses and want the robot to move the end effector down, it doesn't follow a straight line. Is there a way to make MoveIt generate the joint poses without velocities, but with the result of a good end-effector moving? Like go from A to B through N steps. 1. step: Only move joint 1 by 0.02 rad, step 2. joint 1 by 0.04rad AND joint 1. by 0.001 rad and so on, but with have the end-effector move in a straight line?

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answered 2016-02-22 02:16:06 -0600

gvdhoorn gravatar image

updated 2016-02-22 02:16:29 -0600

MoveIt by default actually only plans in joint space. I believe you want to generate Cartesian trajectories.

For that you can use moveit::planning_interface::MoveGroup::computeCartesianPath(..). There is also a GUI interface for that: moveit_cartesian_plan_plugin (it's really a ui, not a planning plugin), but that might be a bit hard to setup.

Alternatively you could interpolate between poses yourself and use something like descartes to turn it into a joint space trajectory.

If you really just want a chopping stage for MoveIt's output, you could configure one of the ROS-Industrial trajectory_filters as a State Adapter and configure the step size appropriately.

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Thanks for the answer! It's ok tha MoveIt generate plans in joint space, but I cannot utilize velocity information of the given points. I need ponts without timing and velocity informations so I could send them to the robot and it should keep the end-effector in a straight line.

Joska213 gravatar imageJoska213 ( 2016-02-22 02:47:49 -0600 )edit

To crop the velocity and timing information, you could just configure a relay node that deletes them. But are you sure, you cannot just ignore this information?

Marcel Usai gravatar imageMarcel Usai ( 2016-07-15 06:59:08 -0600 )edit

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Asked: 2016-02-22 01:53:47 -0600

Seen: 1,190 times

Last updated: Feb 22 '16