Patent ID: 7050895

Claim:
A method for measuring an absolute steering angle of a steering shaft for a vehicle using a first rotatable body and a second rotatable body that rotate together with the steering shaft of the vehicle at a predetermined rotation ratio, respectively, the method comprising: obtaining a Ψ M ′ value by measuring a relative rotational angle Ψ′ of the first rotatable body and obtaining a θ M ′ value by measuring the relative rotational angle θ′ of the second rotatable body, using angle sensors having measurement ranges of Ω; obtaining θ C 's by calculating a plurality of relative rotational angles θ's of the second rotatable body corresponding to the Ψ M ′ value, using the relation between the relative rotational angle Ψ′ of the first rotatable body and the relative rotational angle θ′ of the second rotatable body; obtaining a frequency i-value of the first rotatable body by comparing the plurality of θ C 's to the θ M ′ value; and obtaining an absolute steering angle Φ 1 of the steering shaft based on the relation between Ψ and Φ, after the absolute rotational angle Ψ is obtained by using the i-value.