2-DoF Planar Scribe Bot - ROS2 & CoppeliaSim Integration

Event: IIT Dharwad PARSEC | Build-a-Bot Senior PS (Round 1)

Project: The Virtual Scribe

System: ROS2 jazzy (WSL2) + CoppeliaSim Edu (Windows)

1. Project Overview

This project implements a 2-Degree-of-Freedom (2-DoF) Planar Plotter simulation capable of writing/drawing on a 2D surface. The system bridges two distinct environments: ROS2 jazzy running on WSL (Ubuntu 24.04) and CoppeliaSim running on Windows. Control is achieved via standard keyboard teleoperation, with a custom Python bridge translating ROS messages into ZeroMQ (ZMQ) commands to drive the simulation in real-time.

2. Prerequisites

Windows Side

• Simulator: CoppeliaSim Edu (Version 4.5 or later)
• Network: Firewall must allow incoming connections on port 23000 (default ZMQ port). {if needed turn off the firewall or add a new rule for port 23000 in Advanced network settings}

WSL Side (Ubuntu 24.04)

• ROS2 Distribution: Jazzy Jalisco
• Python: 3.10+
• Dependencies:

sudo apt install ros-jazzy-teleop-twist-keyboard
pip install -r requirements.txt

• If you get error while installing from requirements.txt, run the following command instead

pip install -r requirements.txt  --break-system-packages

3. Directory Structure

Ensure your workspace is organized as follows:

BAB_SUBMISSION/
├─ src/
│  └─ scribe_bot/
│     ├─ resource/
│     │  └─ scribe_bot/
│     ├─ scribe_bot/
│     │  ├─ __init__.py
│     │  └─ scribe_bridge.py
│     └─ test/
│        ├─ test_copyright.py
│        ├─ test_flake8.py
│        └─ test_pep257.py
├─ package.xml
├─ setup.cfg
├─ setup.py
├─ README.md
├─ requirements.txt
├─ Screen Recording 2026-01-09 235402.mp4
└─ Sketcher-2-dof.ttt

4. Installation & Setup

Ensure ROS2 Jazzy is installed. If not then install by following this link: https://docs.ros.org/en/jazzy/Installation/Ubuntu-Install-Debs.html

Step 1: Configure the Network Bridge (Critical)

Since WSL and Windows communicate over a virtual network, you must tell the Python script where Windows is located.

Find Windows IP:

Run this command inside your powershell terminal:

ipconfig

Copy the IP address listed next to IPV4 (e.g., 172.23.112.1).

Update the Bridge Script:

Open in wsl BAB_sbmission/src/scribe_bot/scribe_bot/scribe_bridge.py and update line 10:

WINDOWS_IP = '172.xx.xx.1' 

Note: This IP may change if you restart your computer/WSL.

Step 2: Configure CoppeliaSim

Open Scribe_Bot_Scene.ttt in CoppeliaSim.

Ensure the Object Hierarchy matches the script's expectations:

Base -> X_joint -> X_link -> Y_joint -> ...

Attach the Lua Script (provided in submission) to the Base object to handle pen tracing and drawing.

Step 3: Build the ROS2 Package

cd ~/BAB_submission
sudo apt install colcon
colcon build
source install/setup.bash

5. Execution Guide

Follow this specific order to avoid connection errors.

1. Start Simulation (Windows)

   • Open CoppeliaSim and press the Play button.
   • Verification: The bottom status bar should display "SCRIBE BOT: System Initialization...".

2. Turn firewall temorarily off for the communication to happen or you can add Inbound Rule for port 23000 to accept connections over the network.

3. Start the Bridge (WSL Terminal 1)

   • This node connects ROS to the Simulator.

cd ~/BAB_submission
ros2 run scribe_bot scribe_bridge

Verification: Output should say ✅ Connected to Windows... and ✅ Joint Handles Found.

3. Start Controller (WSL Terminal 2)
   • This node captures your keyboard input.

source /opt/ros/jazzy/setup.bash
ros2 run teleop_twist_keyboard teleop_twist_keyboard

6. Control Guide (Custom Remapping)

The inputs have been remapped to function as a 2D Planar Plotter rather than a driving robot. You do not need to hold Shift.

Basic Movement

Key	Direction	Logic Map
i	Move UP	Maps Linear.X to Y-Axis (+)
,	Move DOWN	Maps Linear.X to Y-Axis (-)
l	Move RIGHT	Maps Angular.Z to X-Axis (+)
j	Move LEFT	Maps Angular.Z to X-Axis (-)
k	STOP	Halts all motors

Advanced Shapes (Diagonal Drawing)

Use these keys to draw stars, diamonds, or diagonals.

Key	Direction
o	Diagonal Up-Right ↗️
u	Diagonal Up-Left ↖️
.	Diagonal Down-Right ↘️
m	Diagonal Down-Left ↙️

7. Troubleshooting

"Connection Refused":

• Did you update the WINDOWS_IP in the Python script?
• Is CoppeliaSim running (Play button pressed)?
• Is Windows Firewall blocking python?

"Joints Not Found":

• Check the Scene Hierarchy in CoppeliaSim. The script looks for /Base/X_joint and /Base/X_joint/X_link/Y_joint. If your hierarchy differs, update the paths in scribe_bridge.py.

Robot moves erratically:

• Ensure you aren't holding the key down if the repeat rate is too high. Tap k to stabilize.

8. Submission Checklist

• ROS2 Package (scribe_bot)

• CoppeliaSim Scene (.ttt) with Lua scripts

• Python Bridge Code (scribe_bridge.py)

• README.md (This file)

• 2-Minute Demo Video Link

• Submitted by: BT_ke_bacche

• Track : senior

• Link To the Demonstration : https://youtu.be/Vq_coAOnuz4