path planning exceeding velocity limits of ur5

asked 2014-10-10 02:34:38 -0500

psfa_fz
36 ●5 ●7 ●7

updated 2014-10-10 03:16:00 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

Hi,

I am using moveit for path planning of a ur5. After finding a valid path, I want to execute it to the real robot (which is connected and communicating properly) but I always receive an error message like:

[ERROR] [WallTime: 1412925263.358047] Received a goal with velocities that are higher than 2.000000

the controller reports:

[INFO][ ... ]: Received new trajectory execution service request...
[WARNING][ ... ]: Controller handle reports status FAILED
[INFO][ ... ]: Execution completed: FAILED

any ideas how to fix that ?

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answered 2014-10-10 03:25:41 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

updated 2014-10-10 03:31:38 -0500

[ERROR] [WallTime: 1412925263.358047] Received a goal with velocities that are higher than 2.000000

The error you are seeing is not caused by exceeding a real, actual velocity limit, but rather by a check in ur_driver that compares the requested velocities against a (private) parameter called max_velocity. The idea behind the check was most likely to be able to enforce a maximum velocity over a trajectory. This is currently not (very well) documented.

This parameter has a default of 2 rad/s (this is in joint space).

You can do two things:

add a max_velocity parameter to the ur_driver node element in ur_bringup/launch/ur_common.launch, like so:

<node name="ur_driver" pkg="ur_driver" type="driver.py" args="...">
    <param name="max_velocity" type="double" value="YOUR_MAX_SPEED" />
</node>

edit ur_driver/src/ur_driver/driver.py, and increase the default value for the max_velocity parameter.

For now, I'd recommend you use option 1 on a source checkout of the universal_robot repository. Option 2 is really not a good idea.

I'll open a ticket on the github repository asking for this to be documented better.

Edit: for reference, see universal_robot/issues/124.

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answered 2014-10-10 04:12:28 -0500

psfa_fz
36 ●5 ●7 ●7

Thank you for your help. I modified the ur_bringup/launch/ur_common.launch file as stated in your option 1 but it seems to have no effect on the results.

In fact, I think the path planning function of MoveIt should be modified/constrained in such a way that it outputs only trajectories with joint velocities that are in the limits of max_velocity, right?

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gvdhoorn ( 2014-10-10 04:13:32 -0500 )edit

[..] that it outputs only trajectories with joint velocities that are in the limits of max_velocity, right?

It depends: if you think it is safer when you work with the robot, or your application does not require higher velocities, then yes, you could do that.

The parameter should work though.

gvdhoorn ( 2014-10-10 04:17:17 -0500 )edit

I modified the ur_bringup/launch/ur_common.launch file as stated in your option 1 but it seems to have no effect on the results.

Did you install from binaries, or do you have a source checkout? Editing the source will require a catkin_make and source devel/setup.bash.

gvdhoorn ( 2014-10-10 04:21:16 -0500 )edit

ok - I got it working so far. After checking the velocity of various paths, it seems that many trajectories have velocities of up to 3.5, so I adjusted the max_velocity level to 3.5. I could excecute some paths on the real robot. Even though, I encountered two problems afterwards:

psfa_fz ( 2014-10-27 08:00:40 -0500 )edit

for some paths, even 3.5 seems not high enough
for others, the robot moved, but stopped at some point due to the security stop. The velocity exeeded the limits of the real robot

psfa_fz ( 2014-10-27 08:02:20 -0500 )edit

Some other users have noticed the issue with security stops as well. See universal_robot/issues/67 and issue 98 fi. Adding information on your specific setup could help solving this.

gvdhoorn ( 2014-10-27 08:21:18 -0500 )edit

PS: you should really have updated your original question with this new information.

gvdhoorn ( 2014-10-27 08:21:22 -0500 )edit

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