The tire-road friction coefficient is critical to vehicle longitudinal, lateral and roll dynamics and control because tire is the only contact part between the vehicle body and the road. However, direct measurement of tire-road friction coefficient is impossible in practice. This paper presents a novel cost effective method for vehicle tire-road friction coefficient estimation. This method only needs the measurements of the wheel angular velocity, the traction/brake torque and the longitudinal acceleration, which are all available from the commonly installed sensors in ordinary passenger vehicles, and can be used to estimate the individual tire-road friction coefficient. There are three steps in the proposed method. Firstly, the longitudinal slip ratio is estimated by using a nonlinear filter with the measured wheel angular velocity. Then the tire longitudinal force is estimated by using a Kalman filter with the measured traction/brake torque and longitudinal acceleration. At last, the friction coefficient is estimated by using the recursive least squares (RLS) method and the results obtained from the first two steps. Numerical simulations are provided to validate the effectiveness of the proposed method. It is shown by the simulation results that the proposed method is effective in estimating the tire-road friction coefficient.
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