Motor-driven power steering system for motor vehicle

摘要

A motor-driven power steering system for a motor vehicle implemented inexpensively in a simplified structure allows operation of a steering assist torque generating motor even in the vicinity of a neutral point while preventing rotation of the motor in a direction reverse to the steering direction as well as self-rotation of a steering wheel notwithstanding of occurrence of abnormality in a controller implemented by a CPU. The motor-driven power steering system includes a CPU (3) for controlling a motor (2) in dependence on output of a steering torque detecting unit (1), an interlock means (5) for limiting driving operation of the motor (2) upon occurrence of abnormality in the CPU (3), and a motor driving means (6) for driving the motor (2) in accordance with commands issued by the CPU (3).