Drone Obstacle Avoidance System

Overview

This project implements an intelligent obstacle avoidance system for drones or similar RC vehicles. The system uses ultrasonic sensors to detect obstacles in four directions (front, back, left, right) and automatically adjusts the vehicle's movement to prevent collisions while maintaining the desired flight path as much as possible.

Features

• Multi-directional obstacle detection using four ultrasonic sensors
• Three flight modes:
  • Manual Mode: Basic obstacle avoidance without position memory
  • Position Hold Mode: Advanced obstacle avoidance with position memory (returns to original position after avoiding obstacles)
  • Loiter Mode: Similar to manual mode with different avoidance behavior
• Position memory system that remembers the original position and returns to it after obstacle avoidance (in Position Hold mode)
• RC signal pass-through when no obstacles are detected
• Interrupt-driven RC signal reading for precise timing and responsive control

Hardware Requirements

• Arduino board (Mega or similar with sufficient pins)
• 4× HC-SR04 ultrasonic sensors (or compatible)
• RC receiver with at least 3 channels
• Servos or ESCs for vehicle control
• Drone or RC vehicle compatible with the system
• Power supply appropriate for your setup
• Mounting hardware and cables

Pin Configuration

Component	Pin	Description
RC Input Channel 3	3	Forward/backward control
RC Input Channel 4	2	Left/right control
RC Input Channel 5	4	Flight mode selection
Servo Output Channel 3	9	Forward/backward output
Servo Output Channel 4	10	Left/right output
Servo Output Channel 5	11	Flight mode output
Front Ultrasonic Trigger	23	Front sensor trigger
Front Ultrasonic Echo	22	Front sensor echo
Right Ultrasonic Trigger	25	Right sensor trigger
Right Ultrasonic Echo	24	Right sensor echo
Left Ultrasonic Trigger	27	Left sensor trigger
Left Ultrasonic Echo	26	Left sensor echo
Back Ultrasonic Trigger	29	Back sensor trigger
Back Ultrasonic Echo	28	Back sensor echo

Installation

1. Connect the hardware according to the pin configuration table above
2. Install the required libraries:
   • Servo.h (included with Arduino IDE)
   • NewPing.h (install via Arduino Library Manager)
3. Upload the avoidance_system.ino sketch to your Arduino board

Usage

1. Power on your RC transmitter
2. Power on the Arduino and the vehicle
3. Select the desired flight mode using Channel 5:
   • Manual Mode: Channel 5 value ≤ 1299
   • Position Hold Mode: Channel 5 value between 1300-1490
   • Loiter Mode: Channel 5 value ≥ 1750
4. Control the vehicle normally using your RC transmitter
5. The system will automatically avoid obstacles while trying to follow your control inputs

Flight Modes Explained

• Manual Mode: The system will avoid obstacles but won't remember the original position. Once an obstacle is cleared, the vehicle will continue in the new direction.
• Position Hold Mode: The system remembers how far it moved to avoid an obstacle and will return to the original flight path once the obstacle is cleared.
• Loiter Mode: Similar to Manual Mode but with different avoidance behavior optimized for hovering or loitering in place.

Customization

You can customize the system by modifying these parameters in the code:

• MAX_DISTANCE: Maximum detection distance for the ultrasonic sensors (default: 50cm)
• MODE_MANUAL_MAX, MODE_POSITION_MIN, etc.: Thresholds for flight mode selection
• FORWARD_PULSE, BACKWARD_PULSE: Servo pulse values for movement directions

Troubleshooting

• Erratic movement: Check sensor connections and ensure they're properly mounted
• No obstacle detection: Verify ultrasonic sensor wiring and power
• System not responding to RC: Check RC receiver connections and channel mapping
• Incorrect flight mode: Verify Channel 5 signal range and mode thresholds