Robotics & Hardware · 2023 · completed
Precision Line-Following Robot
High-speed autonomous trajectory-following robot with PID-tuned optical sensor array.
PID ControlInfrared ArraysMotor ControlEmbedded C++Kinematics
01 / Overview
An autonomous wheeled robot engineered for high-speed track navigation using an infrared reflectance sensor array and closed-loop Proportional-Integral-Derivative (PID) motor control.
02 / Problem
Navigating sharp track curves at high linear velocities causes standard threshold-based robots to oscillate violently and throw themselves off course.
03 / Contribution
Designed the analog sensor conditioning circuit, implemented discrete PID control in firmware, and tuned KP/KI/KD coefficients.
04 / System architecture
Physical + hardware
- 8-channel infrared reflectance array (QTR-8A)
- High-RPM micro metal gearmotors with soft silicone grip tires
- Dual H-bridge driver with high PWM switching frequency
Firmware + software
- Weighted average position estimation algorithm calculating path offset error with sub-millimeter resolution
- Discrete PID controller adjusting left/right motor PWM differential at 500 Hz loop frequency
Signal flowMultiplexed IR phototransistor array feeding analog pins; MCU running 2ms timer interrupt executing PID calculation to update PWM registers.
05 / Engineering decisions
- 01Tuned the derivative coefficient (KD) to aggressively counteract rate-of-error change, damping out high-speed fish-tail oscillations.
06 / Results + constraints
Observed results
- Navigated complex high-curvature test tracks at continuous speeds without losing tracking.
- Smooth trajectory tracking with zero observable overshoot on straightaways.
Current limitations
- Requires calibration under varying ambient lighting conditions.