Patent ID: 7431117

Claim:
A steering control apparatus which is capable of running an automotive vehicle under an automatic steering control without driver's manual operation of a steering wheel, wherein a steering angle of steered wheels is controlled by an electric motor that is connected to the steering wheel and the steered wheels a reduction mechanism, and which is provided with a steering control system that calculates an electric current command value for the electric motor based on a deviation of a detected steering angle of the steered wheels from a target steering angle calculated according to a predetermined target position to which the vehicle is to run, wherein the steering control system comprises: a detected steering angle calculating section which reads out a steering wheel rotational angle from a steering wheel rotational angle sensor provided on the rotational axis of the steering wheel and an motor rotational angle from a motor rotational angle sensor, storing the steering wheel rotational angle at the beginning of the vehicle running under the automatic steering control as an initial value θc 1 of the detected steering angle, calculating a variation θf of the motor rotational angle θ 7 from the motor rotational angle at the beginning of the vehicle running under the automatic steering control, calculating the detected steering angle θj by an equation of θj=θc 1 +θf/R, wherein the initial value θc 1 is added to a value obtained by dividing the variation θf by a reduction ratio R of the reduction mechanism.