Mohammad Faraji - M.Sc. Student
Vahid Johari Majd - Assistant professor
Behrooz Saghafi - M.Sc. Student

Locked brakes and hydroplaning are the reasons which sometimes cause vehicle accidents in wet or icy road surface condition. Anti-lock Braking system (ABS) helps the driver to control decelerating vehicle and improves the control performance of a vehicle in critical conditions. Determining friction of the road surface is essential for developing vehicle control system such as ABS.Hence , a proper model for modeling road – tire contacts is needed. In order to lessen costs, a minimum number of sensors have been used for determining road friction. In this paper, considering a dynamical model of road-tire contacts, a nonlinear observer has been designed for estimating the road-tire friction force in a vehicle , which only uses the measurement of wheel angular velocity .Finally , the proposed observer is evaluated by comparing its performance with that of the observer designed in a recent work.

Tire- road friction estimation , Nonlinear observer , Antilock braking system