URDF and Robot Creation in ROS 2

Objective

This assignment focuses on understanding and applying the concepts of URDF (Unified Robot Description Format) to create custom robots in ROS 2. You will design and build a robotic arm with multiple degrees of freedom (DOF), integrate it with a mobile platform, and create an Ackerman drive system.

Tasks

Task 1: Create a Custom Transform Tree

1. Design a robotic arm with 3 DOF using URDF:
2. Define the transform tree for the robotic arm without including any visualization tags. Focus solely on creating the correct transforms for the arm’s joints.
3. Do not include any visual elements at this stage—only the transforms should be defined.

Task 2: Add Joints and Visual Elements

1. Enhance the robotic arm you created earlier by adding joints:
2. Finger Joints: Use prismatic joint types for the fingers.
3. Base Joint: The base joint should be of the continuous type.
4. All Other Joints: Set these as revolute joints.
5. Add visualization tags to your robot’s URDF to create the body, primarily using cylinder shapes for simplicity.

Task 3: Build a Mobile Manipulator

1. Integrate the robotic arm with a mobile robot platform:
2. Place the robotic arm on top of a differential drive robot.
3. Connect the arm using the base_link of the differential drive robot.
4. Create an Ackerman Drive System:
5. Design a car-like robot structure that represents the front axle rotations for turning, simulating an Ackerman steering mechanism.

Task 4: Debugging Task – Fixing an Incorrect URDF for a Wheeled Robot with a Lifting Mechanism

Task Description: This debugging task introduces a wheeled robot equipped with a lifting mechanism for carrying payloads. The provided URDF has several issues related to joint types, incorrect transforms, and missing elements. Your task is to debug the URDF and ensure the robot’s model is valid and functional.

Instructions:

1. Identify and fix the errors in the URDF file.
2. Verify that the lifting mechanism operates with the correct prismatic joint and range.
3. Ensure the wheels are configured correctly to enable a differential drive system.
4. Validate the corrected URDF using a ROS 2 launch file that spawns the robot in a simulated environment.

Submission Process

Fork the Repository:

1. Fork the Mobile Robotics Engineer repository, ensuring all branches are included in your fork.
2. https://github.com/Robotisim/mobile_robotics_engineer

Clone Your Forked Repository:

“`

mkdir -p ~/assignment_ws/src/ && cd ~/assignment_ws/src/

git clone https://github.com/<your-username>/mobile_robotics_engineer

“`

1. Create Files:
2. Navigate to the module_1_assignment package.
3. Create the required URDF files to implement the tasks, including the robotic arm and mobile manipulator designs.
4. Document Your Work:
5. Create a README.md file in the module_3_assignment package.
6. Provide details about the files you created, including explanations of the URDF structure and the commands needed to visualize your robots in ROS 2.
7. Submit Your Assignment:
8. Push your changes to your forked repository.
9. Provide your repository link in the assignment submission text area.
10. Wait for Review:
11. Wait for the instructors to review your submission.