🤖 R.D - Autonomous Delivery Robot: Technical Reference Manual

This document provides a comprehensive technical overview of the Autonomous Delivery Robot (R.D) project. It covers the architecture, communication protocols, algorithms, hardware specifications, and software logic.

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📑 Table of Contents

1. System Architecture
2. Communication Protocols (UART Binary)
3. Navigation & Pathfinding (A*)
4. Positioning & ArUco Recalibration
5. Hardware Specification & Pinout
6. Software State Machine
7. Web Interface & API Reference
8. Safety & Fail-safes

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🏗 System Architecture

The robot operates on a Distributed Control System (DCS) using two microcontrollers:

🧠 ESP32 Master (High-Level Control)

• Networking: Hosts the Web Dashboard and WebSocket server.
• Pathfinding: Runs the A* algorithm on a RAM-allocated grid map.
• Vision Interface: Receives ArUco detections from an external mobile device via HTTP API.
• User Interface: Manages the 4x4 Keypad and generates delivery security codes.
• Mission Orchestration: Maintains the global state machine and handles the delivery queue.

⚙️ Arduino Uno Slave (Low-Level Control)

• Motion Control: Manages DC motors with differential drive and speed ramping.
• Sensor Fusion: Reads 4 ultrasonic sensors and an MPU6050 IMU.
• Local Safety: Implements autonomous obstacle avoidance and wall centering.
• Peripheral Interface: Controls the MG90S locking servo and I2C LCD status display.

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📡 Communication Protocols (UART Binary)

Communication between the ESP32 and Arduino is handled via Serial2 (115200 baud) using structured binary packets to minimize overhead and latency.

⬆️ Command Packet (ESP32 → Arduino)

Header: 0xAA | Size: 6 bytes

Byte	Field	Description
0	Header	Constant 0xAA.
1	Action	1:FWD, 2:BACK, 3:LEFT, 4:RIGHT, 5:STOP, 6:UNLOCK, 7:OPEN_SERVO, 8:CLOSE_SERVO, 9:LCD_MSG.
2-5	Argument	32-bit integer (e.g., specific LCD message ID or target angle).

⬇️ Sensor Packet (Arduino → ESP32)

Header: 0xBB | Size: 12 bytes

Byte	Field	Description
0	Header	Constant 0xBB.
1-4	Distances	Left, Right, Front, Back (0-255 cm).
5-6	IMU Angle	16-bit signed integer (degrees).
7	Button	Push-button state (0/1).
8	Event	0:None, 1:Obstacle, 2:HatchOpened.
9	Delta Dist	Signed 8-bit integer (cm since last update) for odometry.

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🗺 Navigation & Pathfinding (A*)

The robot uses a modified A Algorithm* (AStarPathfinder.h) optimized for ESP32 memory constraints.

🟢 Grid Configuration

• Cell Size: $20 \text{cm} \times 20 \text{cm}$ ($0.20$m).
• Map Source: map.bin on SD card (bit-packed grid).
• RAM Cache: Downsampled "coarse map" stored in RAM (max 50,000 cells / ~50KB).

🟡 Algorithm Details

• Connectivity: 8-direction movement (Octile distance heuristic).
• Corner Safety: Prevents diagonal movement if adjacent cardinal cells are occupied.
• Robustness: If a destination is inside a wall, the algorithm automatically searches for the nearest free cell within a 5-cell radius.
• Path Memory: Supports paths up to 300 steps (MAX_PATH).

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🎯 Positioning & ArUco Recalibration

To combat wheel slip and odometry drift, the robot uses ArUco Markers as absolute global anchor points.

📍 Recalibration Logic

When a marker is detected (via the mobile phone camera API), the robot:

1. Lookup marker ID in the balises[] registry.
2. Overrides current $(X, Y)$ coordinates and orientation $(\theta)$ with the marker's calibrated world position.
3. Notifies the Dashboard via WebSocket for real-time map visualization update.

🚩 Key Landmarks

• Marker 29: Kitchen / Home Base.
• Markers 24-42: Individual Patient Rooms.
• Markers 201-213: Corridor intersections and technical waypoints.

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🛠 Hardware Specification & Pinout

🔋 ESP32 Master

Peripheral	Pin	Responsibility
SD Card (SPI)	CS:4, MOSI:23, SCK:18, MISO:19	Map & Site hosting.
UART Serial2	TX:17, RX:16	Inter-MCU link.
Keypad Rows	32, 33, 15, 26	Input.
Keypad Cols	27, 14, 12, 13	Input.

⚙️ Arduino Slave

Peripheral	Pin	Responsibility
Motors (A/B)	Dir:12/13, PWM:3/11, Fren:9/8	Movement.
Ultrasonic	L:4, R:5, F:6, B:7	Obstacle detection.
Servo	10	Hatch Lock.
Button	A0	Delivery confirmation.
I2C LCD/IMU	SDA/SCL	Display & Gyro.

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🔄 Software State Machine

The robot operates on 7 core states (MissionState):

1. MISSION_IDLE: Awaiting command from Dashboard.
2. GOING_TO_KITCHEN: Moving to pick-up point (Marker 29).
3. WAITING_LOADING: Stopped at base; waits for staff confirmation via WebSocket.
4. GOING_TO_ROOM: Navigating to the patient's room marker.
5. WAITING_DELIVERY: Stopped at room; checks for Keypad code entry.
6. RETURNING_HOME: Mission success; returning to base.
7. NEEDS_CHARGE: Battery $< 20%$; status locked until charged.

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🌐 Web Interface & API Reference

The ESP32 hosts a Full-stack Single Page Application (index.html) with dual-role authentication.

🔑 Authentication

• Staff: admin / robot2024 or infirmier / soins123.
• Patient: Authenticated via Room Number + PIN (last 4 digits of room).

📡 API Endpoints

• GET /aruco?id=<id>: Triggers ArUco marker detection logic.
• GET /status: Returns JSON of current position, state, and sensors.
• POST /auth?role=<role>: Authenticates user credentials.

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🛡 Safety & Fail-safes

🛑 Obstacle Avoidance Sequence

Triggered when Front sensor $< 20 \text{cm}$:

1. Emergency Stop + Notify Dashboard.
2. Wait 5s for obstacle to move.
3. Active Evasion: If blocked, detects freer side (Left vs Right), pivots $90^\circ$, advances, and re-routes.

🐕 Watchdogs

• ESP32 Watchdog (30s): Panic reset if mission logic hangs.
• Arduino Watchdog (3s): Performs emergency stop if UART heartbeat (0xAA packet) from ESP32 is lost.
• Mission Timeout (10m): Automatically cancels mission and returns home if target is not reached within 10 minutes.