🤖 Autonomous Sumobot Control System

An advanced, production-grade control codebase for an autonomous Sumo Robot (Sumobot) designed to compete in Sumo Ring competitions. This project controls a robot with the primary goal of staying within the ring (using an IR line sensor) while detecting and pushing opponents out (using an Ultrasonic distance sensor).

The repository contains two operational modes tailored for different hardware setups:

1. Sumobot using IR sensor.ino: Standard version focusing strictly on border detection and border evasion (line-bound cruising).
2. Sumobot IR with Ultrasonic.ino: Advanced version integrating line safety with target acquisition and charge routines.

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📋 Table of Contents

• Key Features
• System Architecture
• Hardware Specifications & Schematic
• Wiring Guide
• Operational Logic & State Flow
• Pseudocode
• Calibration & Troubleshooting
• License

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⚡ Key Features

• Safety-First Priority Queuing: Boundary detection immediately interrupts search/attack sweeps, preventing the robot from driving itself out.
• Intelligent Evacuation Direction: Alternating evacuation directions (turning Left for lines 1–3, Right for lines 4–6) prevent the robot from getting trapped in loops or predictable patterns.
• Ultrasonic Pulse Filtering: Fixed standard Arduino timeout bug where a sensor timeout (0 pulse duration) is incorrectly evaluated as an opponent directly in front.
• Configurable Tactile Strategy: Allows optional pre-charge backing maneuvers (wind-up phase) to optimize kinetic energy transfer.
• RAM-Optimized Debug Logging: Utilizes the Arduino F() macro to preserve precious SRAM on microcontrollers like the Arduino Nano.

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📐 System Architecture

The robot works as a finite state machine prioritizing survivability over offense:

stateDiagram-v2
    [*] --> Search_Forward : Initialize Setup
    
    Search_Forward --> Line_Recovery : Black Line Detected (HIGH)
    Search_Forward --> Opponent_Charge : Distance < 15cm
    
    Opponent_Charge --> Line_Recovery : Black Line Detected (HIGH)
    Opponent_Charge --> Search_Forward : Opponent Lost (Distance >= 15cm)
    
    Line_Recovery --> Search_Forward : Recovery Complete (Turn Finished)
    
    state Line_Recovery {
        [*] --> Move_Backwards : Reverse Delay (800ms)
        Move_Backwards --> Pivot_Spin : Switch Motor Polarities
        Pivot_Spin --> [*] : Turn Delay (800ms)
    }

Loading

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🔧 Hardware Specifications & Schematic

The robot conforms to standard mini-sumo dimensions and constraints:

• Dimensions: Max 200mm × 200mm
• Weight: Max 500 grams
• Processor: Arduino Nano (ATmega328P)
• Motor Driver: L298N Dual H-Bridge Driver
• Actuators: Dual DC Geared Motors (1:48 or 1:120 ratio)
• Power Source: 2 × 18650 Li-ion batteries (7.4V series configuration)
• Line Sensor: TCRT5000 IR Reflective Sensor (Active-High for dark surface)
• Object Sensor: HC-SR04 Ultrasonic Ranging Sensor

Refer to the included Sumobot_bb.pdf file in the workspace directory for the detailed breadboard wiring diagram.

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🔌 Wiring Guide

1. Advanced Configuration: IR + Ultrasonic

Component	Arduino Pin	Pin Function / Direction	L298N Driver Connection
IR Sensor	A0	Input (Digital Read)	—
HC-SR04 Trig	D5	Output (Trigger Pulse)	—
HC-SR04 Echo	D6	Input (Echo Pulse Duration)	—
L298N ENA	D2	Output (PWM Left Speed Enable)	ENA
L298N ENB	D3	Output (PWM Right Speed Enable)	ENB
L298N IN1	D7	Output (Left Motor Direction A)	IN1
L298N IN2	D8	Output (Left Motor Direction B)	IN2
L298N IN3	D9	Output (Right Motor Direction A)	IN3
L298N IN4	D10	Output (Right Motor Direction B)	IN4

2. Standard Configuration: IR Only

Component	Arduino Pin	Pin Function / Direction	L298N Driver Connection
IR Sensor	A0	Input (Digital Read)	—
L298N IN1	D5	Output (Left Motor Direction A)	IN1
L298N IN2	D6	Output (Left Motor Direction B)	IN2
L298N IN3	D7	Output (Right Motor Direction A)	IN3
L298N IN4	D8	Output (Right Motor Direction B)	IN4
L298N ENA/ENB	—	Connected to Onboard 5V Jumpers	—

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🧠 Operational Logic & State Flow

Boundary Avoidance (Highest Priority)

1. Edge Transition: The robot constantly reads the IR sensor connected to A0. In typical sumo rings (black surface with a white border, or vice-versa), transitioning onto the border switches the sensor reading to LINE_DETECTED (HIGH).
2. Direction Alternation: To avoid spinning in circles or getting stuck, the robot monitors darklineCount.
   • Line Detections 1–3: Reverse, then spin Left (counter-clockwise).
   • Line Detections 4–6: Reverse, then spin Right (clockwise).
   • At 6 Detections: The count resets to 0 to keep patterns diverse.
3. Early Exit: During a boundary detection, target scan routines are skipped to avoid tracking targets outside the ring boundaries.

Target Scan & Engagement (Active in Safe Zone)

1. Ranging: The HC-SR04 ultrasonic sensor fires a sound pulse. If the reflected sound wave returns under 15cm (configurable via OPPONENT_THRESHOLD_CM), it registers an opponent.
2. Bug Prevention: Standard implementations of pulseIn return 0 if an echo doesn't return (nothing is in range). If unchecked, 0 < 15 evaluates as true, causing the robot to charge empty space. The refactored code intercepts 0 and returns 999cm (out-of-range), preventing false attacks.
3. Engage: Upon verification, the motor controller ramps up to SPEED_ATTACK (100% duty cycle) and charges.

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📝 Pseudocode

💡 Advanced Mode: IR + Ultrasonic

INITIALIZE Motor Control Pins (IN1, IN2, IN3, IN4, ENA, ENB) as OUTPUT
INITIALIZE Ultrasonic Pins (TRIG as OUTPUT, ECHO as INPUT)
INITIALIZE IR Sensor Pin (A0) as INPUT
INITIALIZE Serial at 9600 bps

LOOP:
    lineState = DIGITAL_READ(A0)
    distance = READ_ULTRASONIC_DISTANCE_CM()

    // 1. Edge/Border Avoidance Routine
    IF lineState == LINE_DETECTED AND previousValue == SURFACE_WHITE:
        darklineCount = darklineCount + 1
        
        // Execute recovery actions
        IF darklineCount >= 1 AND darklineCount <= 3:
            EXECUTE turnLeft()   // Reverse 800ms, Pivot Left 800ms
        ELSE IF darklineCount >= 4 AND darklineCount <= 6:
            EXECUTE turnRight()  // Reverse 800ms, Pivot Right 800ms
        ENDIF

        IF darklineCount >= 6:
            darklineCount = 0
        
        previousValue = LINE_DETECTED
        CONTINUE // Skip current cycle to avoid using old distance calculations
    ENDIF

    previousValue = lineState

    // 2. Safe Surface Maneuvers
    IF lineState == SURFACE_WHITE:
        IF distance > 0 AND distance < OPPONENT_THRESHOLD_CM:
            EXECUTE pushOpponent(SPEED_ATTACK) // Full speed forward charge
        ELSE:
            EXECUTE moveForward(SPEED_CRUISE)  // Lower speed searching forward
        ENDIF
    ELSE:
        // Safety Fallback (Still sitting on the black border)
        EXECUTE stopMotors()
    ENDIF

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⚙️ Calibration & Troubleshooting

🔍 Calibrating the IR Line Sensor

1. Place the Sumobot inside the sumo ring (on the main surface). Note the value printed to the Serial Monitor.
2. Place the Sumobot's front nose directly over the border line. Note the value printed to the Serial Monitor.
3. Adjust the built-in potentiometer on the TCRT5000 sensor board using a small screwdriver until the onboard indicator LED turns ON only when crossing the border line.
4. If your sensor reads LOW on the line and HIGH on the surface, invert the logic in the code:

   const int LINE_DETECTED = LOW;
   const int SURFACE_WHITE = HIGH;

🏎️ Troubleshooting Motor Directions

If the robot spins in place or moves backwards when it should move forward:

• Hardware Solution: Swap the positive and negative wire leads of the affected motor at the L298N terminal blocks.
• Software Solution: Adjust the logic levels in moveForward() and moveBackwards(). For example, if the left motor spins backwards during forward movements, change:

  digitalWrite(PIN_MOTOR_IN1, HIGH); // Swap IN1 and IN2 states
  digitalWrite(PIN_MOTOR_IN2, LOW);

📡 Testing the Ultrasonic Sensor

1. Open the Serial Monitor at 9600 baud.
2. Put an obstacle (like your hand or a box) in front of the robot.
3. Ensure the serial print outputs "Opponent detected at X cm! Charging!" only when the obstacle is within 15 cm.
4. If the distance readings are constantly 999 or fluctuating wildly, verify that your Echo and Trigger pins are not swapped on the Arduino Nano.