Laser-triangulation device for in-line measurement of road texture at medium and high speed

The knowledge of the friction coefficient between road and tyres is a very precious information to implement vehicle active control, especially considering the optimisa- tion of the braking action. One of the most important parameters able to influence such a coefficient is the road texture (microtexture and macrotexture). Although different methods are now available to perform reliable texture measurements, no well- established techniques currently exist for measuring the pavement texture at medium- high speed with real time data analysis during the usual vehicle operations. This paper presents a method, based on two identical industrial laser-triangulation displacement transducers, allowing to get real time reliable road micro and macro- texture measurements during standard vehicle operations, even at medium and high speed. The presence of two transducers also allows to estimate the instantaneous vehicle speed, which is needed to obtain the road texture from the sensor time- histories. This means that the presented system can be considered as a stand-alone device able to give as an output the road texture (micro and macro) and also the vehicle speed without any other input. The paper also underlines the advantages of this method and its drawbacks. The method reliability is evidenced by some real time outdoor tests on the different road surfaces of the Pirelli test track and at different vehicle speeds.