Python Move Group Tutorial

This tutorial walks you through creating a Python-based MoveIt 2 interface package using ROS 2 Jazzy. You’ll learn how to:

1. Create a Python ROS 2 package.

2. Write a script that moves a robot to a specific pose.

3. Configure the package for MoveIt.

4. Run the motion planning script.

---

Step 1: Create a Python Package for Move Group

Open a terminal in your ROS 2 workspace src directory:

cd ~/ws_moveit2/src
ros2 pkg create --build-type ament_python moveit_python_demo --dependencies rclpy moveit_commander geometry_msgs

This will generate the basic Python package structure.

Update setup.py

Edit the generated setup.py file and update the entry_points block:

entry_points={
    'console_scripts': [
        'move_to_pose = moveit_python_demo.move_to_pose:main',
    ],
},

---

Step 2: Create Script to Move Robot to a Pose

Create a file called move_to_pose.py inside the moveit_python_demo/moveit_python_demo/ directory:

#!/usr/bin/env python3

import rclpy
from rclpy.node import Node
from moveit_commander import MoveGroupCommander, PlanningSceneInterface, RobotCommander
from geometry_msgs.msg import PoseStamped

class MoveToPoseDemo(Node):
    def __init__(self):
        super().__init__('move_to_pose_demo')
        rclpy.spin_once(self, timeout_sec=1.0)  # ensure time is updated

        self.robot = RobotCommander()
        self.scene = PlanningSceneInterface()
        self.group = MoveGroupCommander('arm')

        self.group.set_pose_reference_frame('world')
        self.group.set_max_velocity_scaling_factor(0.5)
        self.group.set_max_acceleration_scaling_factor(0.5)

        self.move_to_ready_pose()

    def move_to_ready_pose(self):
        target_pose = PoseStamped()
        target_pose.header.frame_id = 'world'
        target_pose.pose.position.x = 0.4
        target_pose.pose.position.y = 0.0
        target_pose.pose.position.z = 0.4
        target_pose.pose.orientation.w = 1.0

        self.group.set_pose_target(target_pose)
        success = self.group.go(wait=True)
        self.group.stop()
        self.group.clear_pose_targets()

        if success:
            self.get_logger().info('Motion executed successfully!')
        else:
            self.get_logger().error('Motion planning failed!')


def main():
    rclpy.init()
    node = MoveToPoseDemo()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

Make it executable:

chmod +x moveit_python_demo/moveit_python_demo/move_to_pose.py

---

Step 3: Configure the Package

Add install_requires to setup.py

Make sure your setup.py includes:

install_requires=['setuptools'],

Add an __init__.py

Create an empty __init__.py file:

touch moveit_python_demo/moveit_python_demo/__init__.py

Update package.xml

Make sure your package.xml includes the correct dependencies:

<exec_depend>moveit_commander</exec_depend>
<exec_depend>rclpy</exec_depend>
<exec_depend>geometry_msgs</exec_depend>

---

Step 4: Build and Run the Package

Build your workspace:

cd ~/ws_moveit2
colcon build --packages-select moveit_python_demo
source install/setup.bash

Launch the robot simulation (if not already running):

ros2 launch panda_moveit_config demo.launch.py

Run your Python move group script:

ros2 run moveit_python_demo move_to_pose

You should see your robot arm move to the specified pose in RViz.

---

Summary

You have now:

• Created a Python ROS 2 package.

• Implemented a motion planning script using MoveIt Commander.

• Configured and launched a robot demo.

• Executed a pose target command.

Feel free to expand the script to include waypoints, cartesian motions, or object collision handling!