🤖 Autonomous Obstacle-Avoiding 4-Wheeled Robot with Servo Scanning and ROS 2 LiDAR Visualization

Built using Arduino Uno, HC-SR04 Ultrasonic Sensor, and RPLIDAR A1 🔧 Powered by dual 3C-rated 18650 Li-ion cells with sensor shield integration

📌 Project Overview:

This project presents a smart autonomous ground robot capable of detecting and avoiding obstacles in real-time using ultrasonic scanning and precise motor control. Designed around the Arduino Uno, it combines real-world sensor interfacing, mechanical motion control, and ROS 2-based LiDAR visualization — making it ideal for robotics prototyping, education, and research extensions.

🔩 Hardware Architecture:

Component Specification / Pin Mapping

• Microcontroller Arduino Uno with Sensor Shield (for easy wiring)
• Motors 4x DC BO motors (geared), driven by L298N driver
• Ultrasonic Sensor HC-SR04 (Trig=A5, Echo=A4)
• Servo Motor SG90 (for scanning), Pin = 3
• Motor Control Pins ENA=6, ENB=5, IN1=11, IN2=9, IN3=8, IN4=7
• Power Source 2x 18650 Li-ion 3C batteries (7.4V approx)
• LiDAR: RPLIDAR A1 with ROS 2 and RViz
• HC-05 bluetooth module

🧠 Working Logic :

Scanning & Sensing:

The ultrasonic sensor, mounted on a servo, rotates to scan the front-left, center, and front-right directions. It measures the distance to nearby objects in all three zones.

Decision-Making Algorithm:

Clear path ➝ Move forward.

Obstacle ahead ➝ Compare left/right distances.

Turn toward the clearer direction, bypass the obstacle, and return to the original path using timed 90° turns.

Motor Control & Speed Management:

Differential drive with speed compensation ensures smooth navigation. The L298N module takes PWM inputs for motor speed and direction.

Power Management:

Dual 18650 Li-ion batteries supply the circuit through the sensor shield, ensuring organized power distribution.

➡️ Obstacle_avoidance_final_code.ino

🌐 ROS 2 Integration (Advanced Layer):

Using RPLIDAR A1, the robot integrates with ROS 2 Humble for real-time 2D environment scanning and visualization:

TF Frames: map → odom → base_link → laser

URDF: Represents the robot structure in RViz

Visualization: Laser scan (/scan) viewable in RViz GUI

➡️ ROS 2 commands for lidar

🔍 Sample LiDAR Scans from RViz

🌟Key Features

Modular Sensor Shield-based wiring for ease of maintenance

Servo-based directional scanning (left, center, right)

Autonomous obstacle detection & avoidance

ROS 2 compatibility with LiDAR visualization

Expandable for line following, Bluetooth remote control

📈 Applications & Extensions

Educational robotics and DIY prototyping

Indoor surveillance or warehouse bots

SLAM algorithm testing platform

Vision and ML integration (future upgrade)