Omnigraph node value readout using python code

Omniverse Isaac Sim
1

I am trying to articulate ur5 robot by subscribing to joint_states topic. I don’t want to use articulation controller to move the robot. Is there anyway to readout the values from ROS2 joint state subscriber node using python code?

2

Hi @yadun.murali.kurikalveed - Yes, you can subscribe to the joint_states topic in ROS2 using Python. Here is a basic example of how you can do this:

import rclpy
from sensor_msgs.msg import JointState

def callback(msg):
    # This function will be called every time a new message is published on the joint_states topic
    print('Received joint state:', msg)

def main():
    rclpy.init()

    node = rclpy.create_node('joint_state_listener')

    subscription = node.create_subscription(
        JointState,
        'joint_states',
        callback,
        10  # Queue size
    )

    rclpy.spin(node)

    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

In this code, callback is a function that will be called every time a new JointState message is published on the joint_states topic. The JointState message contains information about the positions, velocities, and efforts of the joints.

Please note that you’ll need to have the sensor_msgs package installed to use the JointState message. You can install it with sudo apt install ros-<distro>-sensor-msgs, replacing <distro> with your ROS2 distribution name (e.g., foxy).

Also, remember to source your ROS2 environment before running the script, like so: source /opt/ros/<distro>/setup.bash.