🤖 ESP32 4WD Rover — WiFi Web Control + PID

A 4-wheel drive rover controlled wirelessly from any browser over WiFi, with real-time PID motor speed control, live telemetry, and OTA firmware updates — all running on a single ESP32.

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📹 Demo Video

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📸 Project Photos

Top View	Side View

Web Interface

Wiring / Connections

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📌 Overview

This project implements a browser-controlled 4WD differential drive rover with:

• A WiFi HTTP web server running entirely on the ESP32
• A touch-friendly D-pad UI served to any phone or laptop on the same network
• Independent PID control on all four N20 encoder motors for smooth, consistent movement
• Live telemetry showing real-time target speed, actual speed, and PWM for every motor
• Live PID gain tuning from the browser — no re-flashing needed
• OTA (Over-The-Air) firmware updates — after first upload, re-flash wirelessly

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✨ Features

• 🎮 Browser-based D-pad controller (works on mobile and desktop)
• 📐 Differential drive mixing with proportional turn scaling
• 🔄 Independent PID loop per wheel (20 Hz update rate)
• 📊 Live telemetry: target ticks/s, actual ticks/s, PWM per motor
• 🎛️ Live PID gain adjustment from the web UI
• 📡 OTA firmware updates over WiFi
• 🔧 Built-in encoder calibration routine via Serial
• 🛡️ Anti-windup PID integrator clamping
• ⚡ IRAM-placed encoder ISRs for reliable interrupts during WiFi activity

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🛠️ Technologies Used

Hardware

Component	Details
ESP32 Dev Board	Main microcontroller — WiFi, web server, PID
N20 Encoder Motors (×4)	Geared DC motors with built-in quadrature encoders
TB6612FNG H-Bridge (×2)	Dual motor driver — front pair + rear pair
4WD Rover Chassis	Aluminium/acrylic frame with 4 wheels
Li-Po / Li-ion Battery	Power supply for motors and ESP32
Breadboard & Jumper Wires	Prototyping connections

Software & Libraries

Library	Purpose
WiFi.h	WiFi station mode connection
WebServer.h	HTTP server for web UI and API
ArduinoOTA.h	Over-the-air firmware updates

All libraries are included in the ESP32 Arduino Core — no external installs needed.

Arduino Core Requirement

This firmware uses the ESP32 Arduino Core 3.x timer API (timerBegin(1000000)). The older Core 2.x 3-argument API is deprecated and will break silently — ensure you are on Core 3.x.

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🏗️ System Architecture

Browser (Phone / Laptop)
        ↓  HTTP over WiFi
ESP32 Web Server  ←→  /drive  /stop  /pid  /status
        ↓
PID Controller (20 Hz)
   ├── Motor FL ←→ Encoder FL (ISR)
   ├── Motor FR ←→ Encoder FR (ISR)
   ├── Motor RL ←→ Encoder RL (ISR)
   └── Motor RR ←→ Encoder RR (ISR)
        ↓
TB6612FNG H-Bridge Drivers (×2)
        ↓
N20 Encoder Motors (×4)

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🔌 Hardware Connections

Motor Driver → ESP32

Motor	PWM Pin	IN1	IN2
Front-Left (FL)	27	25	26
Front-Right (FR)	13	14	12
Rear-Left (RL)	21	18	19
Rear-Right (RR)	5	22	23

Signal	ESP32 Pin
STBY (Front Driver)	33
STBY (Rear Driver)	32

Encoder → ESP32

Encoder	Channel A	Channel B
FL	34	35
FR	36 (SVP)	39 (SVN)
RL	4	16
RR	17	15

⚠️ Pins 34, 35, 36, 39 are input-only on ESP32 — no internal pull-ups available. Use external pull-up resistors or rely on the encoder's own output stage.

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📁 Repository Structure

ESP32-4WD-Rover/
│
├── README.md
├── .gitignore
│
├── Firmware/
│   └── Esp32_PID_4wd_control/
│       └── Esp32_PID_4wd_control.ino   ← Main sketch (WiFi + PID + Web UI)
│
├── Images/
│   ├── top_view.jpeg
    ├── side_view.jpeg
    ├── connections.jpeg
    └── web_interface.png

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⚙️ Installation & Setup

1. Clone the Repository

git clone https://github.com/MayankJain-22/ESP32-4WD-Rover.git
cd ESP32-4WD-Rover

2. Install ESP32 Arduino Core

In Arduino IDE → File → Preferences → Additional Board Manager URLs, add:

https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

Then go to Tools → Board → Boards Manager and install esp32 by Espressif Systems (version 3.x).

3. Configure WiFi Credentials

Open Firmware/Esp32_PID_4wd_control/Esp32_PID_4wd_control.ino and update:

const char* WIFI_SSID     = "YOUR_WIFI_SSID";
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";
const char* OTA_PASSWORD  = "YOUR_OTA_PASSWORD";

4. Upload via USB (First Time)

• Select board: ESP32 Dev Module
• Select the correct COM port
• Click Upload
• Open Serial Monitor at 115200 baud
• The IP address will be printed once connected to WiFi

5. Open the Web Interface

On any device connected to the same WiFi network, open a browser and go to:

http://[IP shown in Serial Monitor]

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🎮 Using the Web Interface

Section	Description
Speed sliders	Adjust drive speed and turn speed independently
D-pad	Hold buttons to move — release to stop. Supports diagonal movement
Live Telemetry	Real-time target speed, actual encoder speed, and PWM per motor
PID Tuning	Change Kp, Ki, Kd live and apply without re-flashing

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📡 OTA Firmware Updates

After the first USB upload, all future uploads can be done wirelessly:

1. In Arduino IDE go to Tools → Port → Network Ports
2. Select esp32-rover from the list
3. Click Upload as normal
4. Enter the OTA password when prompted

Motors are automatically stopped before any OTA flash operation for safety.

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🔧 Encoder Calibration

The MAX_SPEED_TICKS constant must match your actual motor speed for the PID to work accurately.

1. Lift the rover so wheels are off the ground
2. Open Serial Monitor at 115200
3. Type M and press Enter
4. The RL motor runs at full speed for 3 seconds and prints average ticks/sec
5. Copy the printed value into MAX_SPEED_TICKS in the sketch and re-upload

The default value of 2865.0 was measured from the N20 motors used in this build. Your motors may differ.

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🔄 PID Tuning Guide

Each wheel has its own independent PID controller. Tune using this procedure:

Step	Action
1	Set Ki=0, Kd=0. Increase Kp until responsive but not oscillating. Start at 1.0
2	Add small Ki (try 0.5) to eliminate steady-state speed error
3	If overshooting on direction change, add small Kd (try 0.05)

Gains can be changed live from the web interface PID panel — no re-flash needed.

Verified working values for this build: Kp=0.15 | Ki=0.23 | Kd=0.00

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🔄 Workflow

Power on ESP32
      ↓
Connect to WiFi → print IP to Serial
      ↓
Start Web Server + OTA listener
      ↓
User opens browser → http://[IP]
      ↓
Hold D-pad button → /drive request sent every 150ms
      ↓
ESP32 receives linear + angular values
      ↓
Differential mixing → left/right speed targets
      ↓
PID loop (20Hz) reads encoders → adjusts PWM
      ↓
TB6612FNG drives N20 motors
      ↓
Release button → /stop → motors halt

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📚 Learning Outcomes

• ESP32 WiFi station mode and HTTP web server
• Embedded PID control with anti-windup
• Quadrature encoder reading via hardware interrupts
• Differential drive kinematics and mixing
• IRAM-placed ISRs for interrupt reliability during WiFi
• OTA firmware updates with ArduinoOTA
• Responsive HTML/CSS/JS UI served from microcontroller flash
• H-bridge motor driver (TB6612FNG) control

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🚀 Future Improvements (ARIA Roadmap)

• Autonomous navigation with ultrasonic / LiDAR sensors
• Raspberry Pi 4B integration for on-device LLM voice control
• ROS2 compatibility
• SLAM-based indoor mapping
• Web dashboard with movement history and speed graphs
• Mobile app controller

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👥 Team

Mayank Jain — Firmware, PID, Hardware
IoT, Robotics and Automation Enthusiast

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📄 License

This project is shared for educational and learning purposes.