Digital image correlation techniques for measuring tyre–road interface parameters: Part 2 – Longitudinal tyre slip ratio measurement

•Determining longitudinal slip ratio using camera based techniques.•Uses single sensor to measure.•Measures tyre velocity directly at the contact patch.•Compensates for tyre deflection.

Measurement of tyre longitudinal slip-ratio is often estimated from three independent measurements devices namely wheel rotation speed, vehicle speed and tyre rolling radius. This produces an expensive measurement system to indirectly determine the slip-ratio. This paper presents a method by which the slip-ratio is determined from a video camera using digital image correlation techniques. The camera, mounted in such a way that the contact patch region is captured, enables the system to measure the tyre tread speed and ground speed at the contact patch. The slip-ratio is then determined from these two measurements.