mini_pi_description

Mini_Pi Robot – ROS 2 description & simulation package

Description: Mini_Pi is a small differential drive robot with ultrasonic sensors, modeled in URDF/Xacro and simulated in Gazebo for navigation and SLAM experiments. This is a GIAR research project

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1. Project Overview

mini_pi_description provides the URDF/Xacro description and Gazebo integration for the Mini_Pi robot:

• A small differential-drive robot intended for education, research, and prototyping.
• Designed as a ROS 2-first robot: easy to use with rviz2, Gazebo, and standard ROS 2 tools.
• Focused on:
• Basic navigation experiments (odometry, wheel kinematics).
• SLAM and mapping (with range sensors and simulated worlds).
• Testing control and perception algorithms in simulation before moving to real hardware.

The package focuses on a clean, modular Xacro structure so it can be reused or extended in other projects.

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2. Features

• ✅ Differential-drive mobile base
• Left/right wheel joints with configurable radius and separation.
• ✅ Ultrasonic range sensors
• Front-mounted ultrasonic modules (and additional ones if enabled via parameters).
• ✅ URDF/Xacro modular design
• Reusable macros for chassis, wheels, sensors, etc.
• Easy to tweak dimensions and inertial parameters.
• ✅ Gazebo simulation-ready
• Includes Gazebo plugins for differential drive and sensor simulation.
• Compatible with use_sim_time and standard ROS 2 workflows.
• ✅ RViz visualization
• Robot model can be visualized via robot_state_publisher + joint_state_publisher.
• ✅ Prepared for navigation experiments
• Standard frames (base_link, odom, etc.).
• Structured to be integrated later with Nav2 and SLAM packages.

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3. Requirements

• ROS 2 (Jazzy)

• Gazebo (Harmonic)

• xacro

• robot_state_publisher

• joint_state_publisher or joint_state_publisher_gui

• gazebo_ros (if using Gazebo Classic integrations)

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4. Build & Installation

Clone into your ROS 2 workspace and build:

# 1. Go to your workspace
cd ~/ros2_ws/src

# 2. Clone the repo
git clone https://github.com/<your-user>/mini_pi_description.git

# 3. Build
cd ~/ros2_ws
colcon build --packages-select mini_pi_description

# 4. Source the workspace
source install/setup.bash

5. Robot Description Details

High-level structure of the robot model:

• Base / Chassis

  • Main base_link defined as a box or mesh.

  • Inertial, collision, and visual elements defined in Xacro for reuse and clarity.

• Wheels

  • Two driven wheels:

    • left_wheel_link / right_wheel_link

    • left_wheel_joint / right_wheel_joint

  • Parameters:

    • wheel_radius

    • wheel_separation

• Caster / Support (optional)

  • Passive caster wheel.

• Ultrasonic Sensors

  • Typically attached to a frame like ultrasonic_front_link.

  • Positioned with configurable offsets from base_link.

• Coordinate Frames

  • base_link (main body)

  • base_footprint (optional, planar projected frame)

  • Sensor frames (e.g., ultrasonic_front_link)

  • odom frame for wheel odometry (usually provided by a controller/odometry node, not by this package alone).

The description is written in Xacro to allow parameterization and reuse.

6. Topics, Frames & Controllers

• /tf / /tf_static
  Standard transform topics for the robot’s TF tree.

• /joint_states
  Joint states (wheel joints, sensor joints if any).

• /diff_drive_controller/cmd_vel
  Geometry_msgs Twist commands for the differential drive controller must be stamped:=true.

• /odom
  Odometry (if provided by a controller or an external node).

7. Common Issues & Troubleshooting

[!WARNING] Do not name the robot <name_of_robot>_robot_description because robot_description messes up the argument in ros2_control and it will fail—it's a Jazzy bug. To fix it, do not use that name. You can use mini_pi_description or model or whatever you like.

8. License

This project is licensed under the Apache License 2.0. See the LICENSE file for the full text.

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9. Photos