A variable structure observer for an on-line estimation of a tyre rolling resistance and effective radius

The rolling resistance and the effective radius of a tyre are two important characteristics that are very useful for vehicle diagnosis and wheel monitoring systems. This paper proposes to consider the physical model of rotational and longitudinal dynamics of the wheel and to apply a variable structure observer for an on-line estimation of these quantities using measurement of wheel angular velocity, vehicle speed and engine torque. These latter signals being available on major modern vehicle controller area networks (CAN), the proposed solution do not require any additional sensor. Experimental results are given in order to illustrate the relevance of this approach.