A Non-contact Method for Sensing Tire Contact Patch Deformation Using a Monocular Vision System and Speckled Image Tracking

Abstract

A full-field, non-contact deformation sensing system was developed with an application for tires. Using an image tracking algorithm, in-plane displacements and their gradients were calculated. Furthermore, the effects of blurring from out-of-plane displacement and illumination variation were included in the algorithm developed, providing more accurate in-plane information. An imaging system was placed inside a tire that was compressed by approximate normal loadings. Images of the compressed inner liner were recorded and processed. Although a lens defect made independent determination of the out-of-plane displacement to blurring relationship impossible, an assumption was made given the normal loading condition that allowed normal strains to be plotted at six increments of vertical deflection. The longitudinal strain distribution shows an interesting behavior hardly noted in most literature although the tensile strain does generally increase with increasing load. Having proved that digital image processing can measure tire deformation accurately, this research should provide a solid foundation to develop the technique presented into more robust and efficient forms. With improvements, this technology could be implemented in real automotives to provide the high fidelity information needed to derive accurate tire parameters for advanced electronic stability control systems.