Rover Controller - Complete How-To Guide

This project documents a modular robot controller built for the Arduino GIGA R1 WiFi, powering Obsidian - a tracked rover on the DFRobot Black Gladiator chassis.

The controller supports line following, wall following, and transition behaviours using a PID-based control system and modular sensor logic.
Obsidian successfully demonstrated in the 2025 UCL Robotics competition (UCL East), completing line and wall-following challenges under real-world conditions.

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Images

Front View	Side View

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Demo Video

See Obsidian in action:

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Overview

The Rover Controller is a flexible robotics framework written in C++ for Arduino.

• PID line following with dual QTR sensor arrays
• Wall following & cornering with 5 IR distance sensors
• Modular codebase (sensors, PID, behaviour logic in independent classes)
• Branch-based behaviours: main (line following), dist (wall following), test/obst (legacy)

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Hardware

• Arduino GIGA R1 WiFi
• 2× Pololu Motoron I2C motor drivers
• Dual QTR-9A reflectance sensor arrays
• 5× Sharp IR analog distance sensors (LF, LB, CF, RF, RB)
• 2 DC motors + optional hook actuator
• 10.9V battery pack

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Wiring Summary

Component	Pins
QTR Left	Digital 40-48
QTR Right	Digital 24-32
QTR LEDs	22 (right), 38 (left)
Distance Sensors	A2-A6
Button	23 (pull-up input)
Motoron Drivers	I2C0 + I2C1

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Software Setup

1. Clone repo and select branch (main = line following, dist = wall following).
2. Open rover_controller.ino in Arduino IDE.
3. Select Arduino GIGA R1 WiFi board.
4. Upload firmware and open Serial Monitor (115200 baud).

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Code Architecture

• pid_controller.cpp/h -> Generic PID module (reusable across robots)
• QTRSensorArray.cpp/h -> Normalised reflectance sensor handling
• distance_sensor.cpp/h -> IR distance sensing + filtering
• wifi_logic.cpp/h -> Optional UDP control interface

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Behaviour Logic

Line Following (main branch):

• Dual QTR arrays sample at 100 Hz -> normalised position -> PID correction -> motor control
• Triple-line detection triggers transitions (e.g. hook raise)

Wall Following (dist branch):

• 5 IR sensors provide lateral + angular errors
• Two PID loops (distance & angle) combined for stable wall tracking
• Corner detection (centre sensor + low angle error) triggers 90° turn manoeuvre

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Tuning & Customisation

• PID gains adjustable per module (PIDController pid(Kp, Ki, Kd);)
• Thresholds (line_threshold, confidence) for sensor reliability
• Easily extend transition logic (e.g. custom hook activation on marker detection)

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Calibration

Line Sensors:

qtrL.calibrate_time(3000);
qtrR.calibrate_time(3000);

Sweep across surface to capture min/max reflectance.

Distance Sensors:
Built-in smoothing & validation; no manual calibration required.

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License

MIT License

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Author

Kishan Grewal
GitHub: github.com/kishan-grewal