Electric power steering controller and method of controlling same

摘要

The prior art electric power steering system in a vehicle has not been able to provide high steering-wheel returnability under every operating condition. A method of controlling an automotive electric power steering system in accordance with the present invention starts with estimating a first road reaction torque (Ttire_est1) from driver's steering torque detected by a steering torque detector (1). A second road reaction torque (Ttire_est2) is estimated from the steering angle (&thetas;hdl) detected by a steering angle sensor. A returning torque compensator (17) calculates a steering wheel-assisting torque (Itire) from the second road reaction torque (Ttire_est2). According to the result of the calculation, the assisting torque (Itire) generated by an electric motor (10) is controlled in the direction to return the steering wheel to its center position. The returning torque compensator (17) judges that the steering angle sensor is at fault when the difference ( DELTA Ttire) between the first (Ttire_est1) and second (Ttire_est2) road reaction torques is greater than a given value ( DELTA Tfail). <IMAGE>