ELECTRIC POWER STEERING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an electric power steering system capable of driving a brushless motor and improving steering feeling when a switching element in a driving circuit of the brushless motor fails in short-circuit.SOLUTION: When one FET 31 in a driving circuit 30 fails in short-circuit, a control part 40 identifies the FET which fails in short-circuit. The control part 40 sets a voltage command value P corresponding to current to be supplied to an electric motor 18, based on a detected steering torque T. Then the control part 40 corrects the voltage command value P based on the number of motor rotations n. In fact the control part 40 reduces and corrects the voltage command value P when the number of motor rotations n is lower than a predetermined threshold α.