Patent ID: 7382295

Claim:
A control unit for electric power steering apparatus for applying a steering assist force to a steering system of a vehicle by a motor, comprising: an angle detecting device for detecting a rotation angle (θ) of the motor necessary for controlling the motor which is supplied a carrier wave signal (sin ωt) having a predetermined frequency and generates a sin signal (sin ωt·sin θ) having a wave shape obtained by modulating an amplitude of said carrier wave signal by sin θ and a cos signal (sin ωt·cos θ) having a wave shape obtained by modulating the amplitude of said carrier wave signal by cos θ; and an abnormal region judging map constituted by two values including a value corresponding to said sin θ and a value corresponding to said cos θ and constituted by a normal region and an abnormal region; wherein said abnormal region judging map sets the value corresponding to said sin θ to a value in an x-coordinate and sets the value corresponding to said cos θ to a value in a Y-coordinate, and a region surrounded by a quadrangle α structured on a region constituted by an X-axis and a Y-axis orthogonal to each other around an origin in which both of the values in the X-coordinate and the Y-coordinate are zero, and a quadrangle β smaller than said quadrangle α constituted around said origin forms a normal region, and an abnormality of said angle detecting device is judged by mapping said sin θ and said cos θ respectively calculated from said sin signal and said cos signal to said abnormal region judging map.