Not smooth movement using Moveit Servo on ur5e

[AFimiani]

Affected ROS2 Driver version(s)

commit ff5b80e

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 both the ROS driver and UR Client Library from source

Which robot platform is the driver connected to.

Real robot

Robot SW / URSim version(s)

ur5e

How is the ROS driver used.

Through the robot teach pendant using External Control URCap

Issue details

Description

I am attempting to teleoperate the ur5e using MoveIt Servo to perform precision movements by sending geometry_msgs/TwistStamped commands to the /servo_node/delta_twist_cmds topic. The message is sent at a fixed frequency of 500 Hz from a ROS2 node, populating only one axis at a time and setting the other fields of the Twist message to 0.0. When a sufficiently high value is sent (0.3) , the manipulator moves smoothly along a straight line without issues. However, when a low value is sent (0.07), the manipulator no longer performs a perfect linear movement and starts exhibiting up and down movements, making proper precise teleoperation difficult . This behavior is also observed when attempting teleoperation using a 3D mouse.
I am directly connected to the robot using an ethernet cable.

The UR robot executes a slow linear movement without oscillations when manipulated:

• via the teach pendant.
• in simulation using use_fake_hardware:=true
• through MoveIt

Steps to Reproduce

Modifications made to launch files

• In both files, import the calibration file obtained through the ur_calibration package.
• Launch ur_control with the forward_position_controller as the active controller.
• Start the robot_state_publisher with publish_frequency=500.

Command sequence

In different terminal:

    ros2 launch ur_robot_driver ur_control.launch.py 
    ros2 launch ur_moveit_config ur_moveit.launch.py 
    ros2 service call /servo_node/start_servo std_srvs/srv/Trigger {}

-> launch teleop node

Expected Behavior

I expect that slow linear movements are executed without oscillations using MoveIt Servo communication.

Actual Behavior

The robot is unable to perform slow linear movements smoothly.

Relevant log output

No response

Accept Public visibility

• I agree to make this context public

[Blain354]

Hello AFimian,

I don't have an answer to your issue, but out of curiosity, how or where did you find resources to control a UR5e in servo mode? I am not a moveit expert and i have been searching for a certain time..

Also, if you find an answer, i would be curious to know about it too, Thanks !