robotic_arm_urdf_ws

A basic ROS 2 (Jazzy) workspace containing a simple 3-link robotic arm with a 2-finger gripper, modeled in URDF/Xacro using primitive shapes (cylinders and boxes) and visualized in RViz2.

Overview

This workspace defines simple_3_link_arm: a robotic arm built from a cylindrical base, three revolute links, and a fixed-mount parallel gripper with two prismatic fingers. It's a learning/tutorial-style project for understanding URDF/Xacro structure, link/joint definitions, and RViz2 visualization in ROS 2 — with no Gazebo, ros2_control, or MoveIt2 integration (yet).

Tech Stack

• ROS 2 Jazzy (Ubuntu 24.04)
• URDF / Xacro — robot structure definition
• RViz2 — visualization
• robot_state_publisher + joint_state_publisher_gui — publishing TF and manual joint control
• ament_cmake — package build system

Repository Structure

robotic_arm_urdf_ws/
├── robot_description/        # Robot model package
│   ├── urdf/
│   │   └── robot.urdf.xacro   # Xacro definition of simple_3_link_arm
│   ├── launch/
│   │   └── robot_rviz.launch.py   # Launches robot_state_publisher, joint_state_publisher_gui, and RViz2
│   ├── rviz/
│   │   └── simple_arm.rviz    # Pre-configured RViz view (Fixed Frame: base_link)
│   ├── CMakeLists.txt
│   └── package.xml
├── robot_ros2/                # Metapackage (depends on robot_description)
│   ├── CMakeLists.txt
│   └── package.xml
├── LICENSE                    # Apache License 2.0
└── README.md

Robot Model

The arm (simple_3_link_arm) consists of:

Link	Shape	Notes
base_link	Cylinder (r=0.1, l=0.05)	Mass 5.0 kg
link1	Cylinder (r=0.04, l=0.4)	Mass 2.0 kg
link2	Cylinder (r=0.04, l=0.3)	Mass 1.5 kg
link3	Cylinder (r=0.04, l=0.25)	Mass 1.0 kg
gripper_base	Box (0.05 × 0.05 × 0.02)	Mass 0.5 kg, fixed to link3
left_finger / right_finger	Box (thin, 0.08 m long)	Mass 0.1 kg each

Joint	Type	Parent → Child	Axis	Limits
joint1	revolute	base_link → link1	Z	±3.14 rad
joint2	revolute	link1 → link2	Y	0.50 to 2.09 rad
joint3	revolute	link2 → link3	Y	0 to 2.35 rad
gripper_joint	fixed	link3 → gripper_base	—	—
left_finger_joint	prismatic	gripper_base → left_finger	Y	0 to 0.016 m
right_finger_joint	prismatic	gripper_base → right_finger	−Y	0 to 0.016 m

So the arm has 3 revolute joints (shoulder yaw, shoulder/elbow pitch x2) plus a 2-finger prismatic gripper, all defined with visual, collision, and inertial properties — no mesh files, purely primitive geometry (cylinders/boxes).

Prerequisites

• Ubuntu 24.04
• ROS 2 Jazzy installed (installation guide)
• joint_state_publisher_gui and xacro:

  sudo apt install ros-jazzy-joint-state-publisher-gui ros-jazzy-xacro

Setup

1. Clone the repository into a Colcon workspace src folder:

   mkdir -p ~/ros2_ws/src
   cd ~/ros2_ws/src
   git clone https://github.com/ilovevampire/robotic_arm_urdf_ws.git .

   (Note: the repo itself contains the packages directly at its root — robot_description/ and robot_ros2/ — rather than nesting them under a src/ folder, so clone it directly into your workspace's src/ directory as shown above.)

2. Build the workspace:

   cd ~/ros2_ws
   colcon build --symlink-install
   source install/setup.bash

Usage

Launch the robot model in RViz2 with manual joint control:

ros2 launch robot_description robot_rviz.launch.py

This starts:

• robot_state_publisher — parses robot.urdf.xacro via the xacro command and publishes robot_description + TF
• joint_state_publisher_gui — opens a slider GUI to manually move each joint (joint1, joint2, joint3, and the two finger joints)
• rviz2 — opens with the pre-configured simple_arm.rviz view (Fixed Frame set to base_link, with Grid, TF, and RobotModel displays enabled)

Use the slider window to rotate the arm's joints and open/close the gripper fingers, and watch the model update live in RViz2.

Future Improvements

• Add Gazebo simulation support (ros2_control + gz_ros2_control).
• Add a MoveIt2 configuration package for motion planning.
• Replace primitive-shape visuals with proper mesh files for a more realistic appearance.
• Flesh out robot_ros2 as a full metapackage (it currently only depends on robot_description).
• Fill in package descriptions/licenses in package.xml (currently marked TODO).

Author

ilovevampire

License

Apache License 2.0 — see LICENSE for details.