Slip-based tire-road friction estimation

Tire-road friction is estimated using the wheel-slip computed from standard sensor signals. A parametric model is estimated using an adaptive lter supported by a fault detector. Results from extensive eld trials are presented. An approach to estimate the tire{road friction during normal drive using only the wheel slip, that is, the relative diierence in wheel velocities, is presented. The driver can be informed about the maximal friction force and be alarmed for sudden changes. Friction related parameters are estimated using only signals from standard sensors in a modern car. An adaptive estimator is presented for a model linear in parameters, which is designed to work for periods of poor excitation, errors in variables, simultaneous slow and fast parameter drifts and abrupt changes. The physical relation between these parameters and the maximal friction force is determined from extensive eld trials using a Volvo 850 GLT as a test car.