TBWC Arduino Systems Code

Arduino firmware for the Teddy Bear Wheelchair (TBWC) autonomous robot system. This code controls the robot's navigation, motor control, distance measurement, and servo actuation for competition tasks.

About the TBWC Project

The Teddy Bear Wheelchair (TBWC) is an autonomous robot designed for precision navigation and task completion. This Arduino code implements the control system for:

Precise distance-based navigation using wheel tachometry
Two independent operational modes for different competition tasks
Real-time speed and position feedback
Servo-controlled actuation for task completion

The system uses interrupt-driven wheel encoding for accurate distance measurement and supports both autonomous startup and serial command control.

Features

Core Functionality

Dual Operation Modes: Two pre-programmed autonomous routines (Mode 1 and Mode 2)
Precision Distance Tracking: Interrupt-based tachometer with real-time distance calculation
Automated Startup: Pin-based mode selection at power-on with 3-second delay
Speed Monitoring: Real-time wheel RPM and linear speed (m/s) calculation
Servo Control: Calibrated servo actuation for task completion in Mode 2
Serial Interface: Full manual control and debugging via serial commands

Mode 1: Round-Trip Navigation

Forward travel: 4.52 meters (452 cm)
Automatic reversal at target distance
Backward travel: 4.52 meters (452 cm)
Total distance: 9.04 meters
Optimized for speed run tasks

Mode 2: Distance + Servo Action

Forward travel: 2.44 meters (244 cm)
Stops at target distance
Executes 120° servo rotation and return
Designed for trash launch or actuation tasks

Real-Time Feedback

Distance traveled (meters, 3 decimal precision)
Wheel RPM (revolutions per minute)
Linear speed (meters per second)
20ms update interval during operation

Hardware Requirements

Electronics

Arduino Board: Uno, Nano, or compatible (ATmega328P-based)
Motor Driver: H-bridge driver (e.g., L298N, L293D) supporting PWM control
IR Sensor: Optical tachometer or photointerrupter for wheel speed measurement
Servo Motor: Standard hobby servo (0-180°)
Power Supply: Appropriate for motors and electronics (typically 7-12V for motors, 5V for Arduino)

Mechanical Components

Drive wheels with radius: 26.05mm (2.605 cm)
Two black bands per wheel for tachometry (2 pulses per revolution)
Servo mounting for actuation mechanism

Wiring Requirements

Common ground between Arduino, motor driver, and sensors
Separate power supply for motors (do not power motors from Arduino 5V pin)
Interrupt-capable pin for tachometer (Pin 3 recommended)

Pin Configuration

// Motor Control
Pin 11 (PWM)  - Motor Enable (speed control)
Pin 12        - Motor Direction IN1
Pin 13        - Motor Direction IN2

// Sensors & Actuators
Pin 3         - IR Tachometer (interrupt-capable, REQUIRED)
Pin 9 (PWM)   - Servo Signal

// Mode Selection
Pin 7         - Mode Select Input (read at startup)
Pin 5         - Status Output (set HIGH at startup)

Pin 7 Mode Selection Logic

HIGH at startup → Mode 2 (2.44m + servo action)
LOW at startup → Mode 1 (4.52m forward, 4.52m reverse)

Installation & Setup

Arduino IDE

Install Arduino IDE (version 1.8.x or 2.x)
Install the Servo library (usually included by default)
Open CompletedTWBCOptimizedCode.ino
Select Tools → Board → Arduino Uno (or your board)
Select Tools → Port → Your Arduino's COM port
Click Upload (→ button)
Open Tools → Serial Monitor at 115200 baud

Hardware Setup

Connect motor driver to Arduino (pins 11, 12, 13)
Connect IR tachometer to Pin 3 (must be interrupt-capable)
Connect servo to Pin 9
Wire Pin 7 for mode selection (HIGH/LOW switch)
Verify Pin 5 output is available
Ensure common ground across all components
Power motors from external supply, not Arduino 5V

First Run Verification

1. Upload code with Pin 7 set LOW (Mode 1)
2. Serial Monitor should show:
   - "Startup: pin 5 LOW -> Mode 1 selected."
   - "Waiting 3 seconds before starting..."
   - Real-time distance/speed/RPM data
3. Robot should drive forward, then reverse automatically

Operation Modes

Automatic Startup Sequence

Power on Arduino
System reads Pin 7 to determine mode
Pin 5 is set HIGH (status indicator)
3-second delay before starting
Selected mode begins automatically

Mode 1: Round-Trip Run

Purpose: Speed run or long-distance navigation

Sequence:

Drive forward at high speed (PWM 255)
Monitor distance until 4.52m reached (with 0.25m buffer)
Reverse direction automatically
Drive backward at high speed
Stop when total distance reaches 9.04m
Print final statistics

Use Case: Competition speed runs, straight-line tests

Mode 2: Approach & Actuate

Purpose: Precision positioning with servo action

Sequence:

Drive forward at high speed (PWM 255)
Monitor distance until 2.44m reached
Stop motor
Wait 1.5 seconds
Rotate servo 120° from home position
Wait 300ms
Return servo to home position
Task complete

Use Case: Trash launch, object manipulation, target activation

Serial Commands

Open Serial Monitor at 115200 baud for real-time control and debugging.

Mode Control

Mode 1       - Start Mode 1 (4.52m forward + 4.52m reverse)
Mode 2       - Start Mode 2 (2.44m + servo action)
Stop         - Emergency stop (cancels current mode)

Motor Speed Adjustment

SetHigh <0-255>   - Set high-speed PWM value (default: 255)
SetLow <0-255>    - Set low-speed PWM value (default: 90)
GetSpeeds         - Display current speed settings

Servo Calibration

+            - Increment servo position by 1 degree
-            - Decrement servo position by 1 degree
SetServo     - Set current position as logical zero (0°)

Example Session

> Mode 1
Mode 1 selected via Serial and started.
Distance (m): 0.164  |  Wheel RPM: 145.23  |  Speed (m/s): 0.396
Distance (m): 0.328  |  Wheel RPM: 147.81  |  Speed (m/s): 0.402
...
Mode1: reached forward distance. Reversing...
...
Mode 1 complete. Final stats:
Total distance (m): 9.0412

> SetHigh 200
motorSpeedHigh set to 200

> +
Servo moved to 44 deg (user offset incremented).

Configuration & Calibration

Physical Constants (lines 26-34)

const float wheelRadius_m = 0.02605;    // Wheel radius in meters (26.05mm)
const int pulsesPerRev = 2;             // Black bands per wheel rotation
const float MODE1_PHASE_DISTANCE = 4.52; // Mode 1 distance in meters
const float MODE2_DISTANCE = 2.44;       // Mode 2 distance in meters

Calibration:

Measure actual wheel radius with calipers
Count tachometer pulses per wheel revolution
Adjust MODE1/MODE2 distances based on competition requirements

Motor Speed Settings (lines 42-43)

int motorSpeedHigh = 255;  // Maximum PWM (full speed)
int motorSpeedLow  = 90;   // Reduced PWM (not actively used)

Tuning:

Reduce motorSpeedHigh if robot is too fast or overshoots
Increase for faster completion times
Test on actual surface for optimal grip/speed balance

Servo Configuration (lines 54-56)

int servoLogicalZero = 0;    // Home position reference
int servoUserOffset = 43;     // Initial offset in degrees
const int servoRotate = 120;  // Rotation amount for Mode 2

Calibration Process:

Upload code and power on
Use + / - commands to move servo to desired home position
Send SetServo to save position as new zero
Test Mode 2 to verify 120° rotation reaches target

Tachometer Debouncing (line 39)

const unsigned long debounceMicros = 25000UL; // 25ms debounce

Adjustment:

Increase if seeing erratic pulse counts (noise/bouncing)
Decrease for higher maximum measurable speed

Technical Details

Distance Measurement System

Method: Interrupt-driven optical tachometry

IR sensor detects black bands on drive wheel
Each pulse triggers hardware interrupt (Pin 3)
ISR (Interrupt Service Routine) increments pulse counter with debouncing
Distance calculated from: pulses → revolutions → meters

Formula:

Revolutions = Pulses / PulsesPerRevolution
Distance (m) = Revolutions × WheelCircumference
WheelCircumference = 2 × π × WheelRadius

Accuracy: ±0.1mm per revolution (limited by wheel radius precision)

Speed Calculation

RPM (Revolutions Per Minute):

1. Count pulses over time window (default 20ms)
2. PulsesPerMinute = (DeltaPulses / TimeInMinutes)
3. WheelRPM = PulsesPerMinute / PulsesPerRev

Linear Speed (m/s):

1. Measure distance traveled in time window
2. Speed = DistanceMeters / TimeSeconds

Update Rate: 20ms (50 Hz) - provides smooth real-time feedback without overwhelming serial output

Motor Control

H-Bridge Configuration:

IN1 HIGH, IN2 LOW = Forward
IN1 LOW, IN2 HIGH = Backward
Both LOW = Coast stop (enable pin controls speed via PWM)

PWM Control: Pin 11 uses hardware PWM (490 Hz on Uno) for speed regulation

Servo Control System

Safe Initialization:

Servo attaches without commanding initial position
Prevents sudden movements that could damage mechanism
Current physical position treated as logical 0° at startup

Calibration Features:

Incremental adjustment (±1° via serial)
Zero-point setting (SetServo command)
Clamped writes (0-180° enforced) prevent servo damage

Interrupt System

Critical Requirement: Pin 3 must support hardware interrupts

Arduino Uno/Nano: Pins 2 and 3 support attachInterrupt()
Code validates interrupt capability at startup
ISR kept minimal (debounce check + counter increment) for reliability

Code Structure

Authors: Noah (tachometer, interrupts, servo) & Rayan (motor control, modes, serial)

Key Functions:

tachISR(): Interrupt service routine for tachometer
getDistanceMeters(): Safe read of pulse counter with interrupt protection
getSpeed_m_s() & getRPM(): Windowed speed calculations
setMotorForward/Backward(): H-bridge control abstraction
handleSerial(): Command parsing and execution
safeServoInit(): No-movement servo attachment

Troubleshooting

Robot Doesn't Start

Check: Pin 7 connection (mode select)
Check: Serial Monitor at 115200 baud - should show startup messages
Check: Power supply adequate for motors
Fix: Verify 3-second delay message appears, indicating code is running

Distance Measurement Errors

Symptom: Distance not increasing or increasing too fast
Check: IR sensor alignment with wheel bands
Check: Pin 3 connection to tachometer
Fix: Verify "attachInterrupt() on pin 3" message in Serial Monitor
Fix: Adjust debounce value if seeing erratic counts

Motor Not Running

Check: Motor driver power supply (separate from Arduino)
Check: Pins 11, 12, 13 connections to motor driver
Check: Motor driver enable pin has PWM signal
Fix: Test with SetHigh 255 command to ensure speed is set

Servo Doesn't Move (Mode 2)

Check: Servo power (needs 5V, adequate current)
Check: Pin 9 connection to servo signal wire
Check: Servo is not mechanically jammed
Fix: Use +/- commands to test servo manually before running Mode 2

Overshooting Target Distance

Cause: Robot momentum, surface friction, or wheel radius miscalibration
Fix: Reduce motorSpeedHigh for more controlled stopping
Fix: Measure actual wheel radius and update wheelRadius_m constant
Fix: Add stopping buffer in code (already has 0.25m in Mode 1)

Wrong Mode Starts

Check: Pin 7 state at power-on (use multimeter or LED)
Symptom: "pin 5 HIGH" but expected LOW (or vice versa)
Fix: Verify mode select switch/jumper wiring
Override: Use Serial commands (Mode 1 or Mode 2) to manually select

Code Won't Upload

Check: Correct board selected (Tools → Board → Arduino Uno)
Check: Correct port selected (Tools → Port)
Error: "avrdude: stk500_recv(): programmer is not responding"
- Disconnect Pin 0/1 if using them (TX/RX conflict)
- Try different USB cable or port
- Press reset button on Arduino right before upload

Interrupt Error at Startup

Error: "chosen IR pin is not interrupt-capable"
Cause: Tachometer not connected to Pin 3 (or Pin 2)
Fix: Rewire tachometer to Pin 3 (required for Uno/Nano)

Serial Monitor Shows Garbage Characters

Fix: Set baud rate to 115200 in Serial Monitor dropdown
Fix: Wait for Arduino to fully reset after upload

Real-Time Stats Not Printing

Cause: Mode not running (stopped or never started)
Check: Send Mode 1 or Mode 2 command
Check: Stats only print when mode is actively running

Project Repository: relfayoumi/TBWC-Arduino-Systems-Code

For issues, questions, or contributions, please open an issue on GitHub.

Name		Name	Last commit message	Last commit date
Latest commit History 6 Commits
CompletedTWBCOptimizedCode.ino		CompletedTWBCOptimizedCode.ino
README.md		README.md

splat1745/TBWC-Arduino-Systems-Code

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