JTC using velocity as command state interface yields to vibration due to sudden deceleration

[odbee]

Affected ROS2 Driver version(s)

2.2.10

Used ROS distribution.

Humble

Which combination of platform is the ROS driver running on.

Ubuntu Linux with standard kernel

How is the UR ROS2 Driver installed.

Build the driver from source and using the UR Client Library from binary

Which robot platform is the driver connected to.

UR E-series robot

Robot SW / URSim version(s)

ur10e

How is the ROS driver used.

Through the robot teach pendant using External Control URCap

Issue details

Summary

I am looking to use the UR10e using a joint trajectory controller with velocity as a command interface instead of position.

Issue details

when i send velocity commands to it the movements are extremely choppy and often lead to the robot doing invalid moves and stopping.

Steps to Reproduce

change joint trajectory controller in ur_controllers.yaml in ur_robot_driver to

joint_trajectory_controller:
ros__parameters:
joints:
- $(var tf_prefix)shoulder_pan_joint
- $(var tf_prefix)shoulder_lift_joint
- $(var tf_prefix)elbow_joint
- $(var tf_prefix)wrist_1_joint
- $(var tf_prefix)wrist_2_joint
- $(var tf_prefix)wrist_3_joint
command_interfaces:
- velocity
state_interfaces:
- velocity
- position
state_publish_rate: 100.0
action_monitor_rate: 20.0
open_loop_control: true

Without open_loop_control: true the robot would not move at all.

Expected Behavior

Smooth movements similar to JTC using position as a command interface

Actual Behavior

choppy erratic movements. no sudden deceleration

Relevant log output

No response

Accept Public visibility

• I agree to make this context public

[fmauch]

Thank you for reporting this. I would have assumed that this is actually working, but apparently, it does not. Using open_loop control doesn't seem like a proper solution to the problem, but we should check this, anyway.

[URJala]

I tried running this, and cannot reproduce the choppiness that you mention. I changed the command interface to velocity for the JTC (also tried the scaled jtc for good measure), and with open loop control it seems to run smoothly. I used the example_move script for the test.
Could you provide the trajectory that is choppy when executed in open loop mode?