Detecting Tire Pressure Losses Using Linear Phase Shift in Wheel Correlation Analysis

Wheel correlation analysis is a method for estimating the speed of a car by determining the delay between a disturbance on the front and the rear wheels. Given the car’s speed and the angular speed of a wheel the radius can be estimated, and changes in radius can be detected over time. The purpose is to detect pressure losses by observing decreasing radius estimates. In this thesis we implement wheel correlation analysis, where the delay is determined by determining the linear phase shift that occurs because of the delay. Two methods are developed — the line fitting approach and the discrete values approach — and a total of six different ways of estimating the linear phase shift are examined. Using linear phase shift in wheel correlation analysis has proven effective for estimating speed, and detecting tire pressure losses is possible although not reliable.