Patent ID: 8660755
Filing Date: 2014-02-25
Classification: B62D

Abstract:
1. An electric power steering system comprising: a motor for assisting a steering operation of a steering wheel; a motor drive circuit for supplying the motor with drive currents for driving the motor by converting a current supplied from a power source to the drive currents; a power shut-off circuit provided in a power line extending from the power source to supply the drive currents to the motor through the motor drive circuit, the power shut-off circuit shutting off power supply from the power source to the motor drive circuit or from the motor drive circuit to the motor when an abnormality arises; and a control unit for controlling power supply to the motor by controlling the motor drive circuit, wherein the control unit includes a state detection section, a steering detection section and a failure diagnosis section, the state detection section detecting that the control unit is in a normal control operation state for controlling the power supply to the motor by controlling the motor drive circuits after an ignition switch is turned on, the steering detection section detecting an amount of the steering operation of the steering wheel, and the failure diagnosis section diagnosing a short-circuit failure of the power shut-off circuit, when the state detection section detects that the control unit is in the normal control operation state and the steering detection section detects that a detected amount of the steering operation is less than a predetermined amount.