Patent ID: 7436172

Claim:
An angular speed detecting device for detecting an angular speed of a rotating object, said device comprising: first means for setting a magnetic field; second means for generating a first sinusoidal signal Va and a second sinusoidal signal Vb that each change between plus and minus signs as a function of change in relative direction of the magnetic field between the first and second means as an object rotates and causes relative rotational motion between the first and second means; and computing apparatus configured for calculating an angular speed from the first and second signals by (a) forming a pair of trigonometric functions of a trigonometric value θ′ from the sinusoidal signals Va and Vb, (b) forming a table showing plus or minus signs for the pair of sinusoidal signals Va, Vb and for corresponding trigonometric values θ′ at a plurality of rotational angles of the rotating object, (c) distinguishing rotational position of the rotating object based on combinations of the plus or minus signs for the first and second sinusoidal signals Va, Vb and the trigonometric value θ′, (d) forming a pair of saw-tooth curves of output angles θ 1 , θ 2 in terms of a 360-degree angular range that are different in phase with respect to each other by adding offset values to the trigonometric value θ′ according to the rotation position that is distinguished above, and (e) selectively using curves of the output angles θ 1 and θ 2 to calculate the angular speed of the rotating object, thereby reducing noise.