Patent ID: 6260655
Filing Date: 2001-07-17
Classification: B62D

Abstract:
An electric power steering apparatus for an automotive vehicle which includes an electric motor for applying an electric steering assist to a steering system interconnecting a steering wheel and steered wheels of the automotive vehicle, a steering torque sensor for detecting steering torque applied to the steering system, a motor voltage detector for detecting a motor voltage supplied to said electric motor, a motor current detector for detecting a motor current flowing through said electric motor, a motor condition detector for detecting a zero-rotating-speed condition of said electric motor, a control unit including a current setting section for setting a target motor current corresponding at least to the steering torque detected by said steering torque sensor and, a motor drive for driving said electric motor on the basis of a motor control signal generated by said control unit, the improvement comprising:said control unit further including a drive control section generation the motor control signal on the basis of an offset between the target motor current and the motor current detected by said motor current detector, a motor resistance calculating section for, on the basis of the motor voltage and motor current, calculation a winding resistance value of said electric motor when said motor condition detector is detecting the zero-rotating-speed condition of said electric motor, and a resistance value storage section for retaining the winding resistance value, wherein rotating speed of the motor is determined based on signals from said motor voltage detector, said motor current detector, and said resistance value storage section to permit said control unit to provide unload control for said electric motor.