A resolver can make accurate angle detection in an entire detection range. The resolver includes a resolver stator having an excitation winding of one phase adapted to be excited by a power supply and a first and a second output winding of two phases for outputting a change in the density of magnetic flux as a voltage, a resolver rotor arranged at a central portion of the resolver stator so as to cooperate with the resolver stator for changing a gap permeance between the resolver rotor and the resolver stator in accordance with the rotation of the resolver rotor, and a detection error correction part that corrects an angle detection error of the resolver by using the value of a Lissajous radius of a circular Lissajous waveform obtained from the amplitudes of an output signal Scos from the first output winding and an output signal Ssin from the second output winding.
1. A resolver comprising:
a resolver stator having an excitation winding of one phase adapted to be excited by a power supply and output windings of two phases for outputting a change in the density of magnetic flux as a voltage;
a resolver rotor that is arranged at a central portion of said resolver stator and cooperates with said resolver stator for changing a gap permeance between said resolver rotor and said resolver stator in accordance with the rotation of said resolver rotor; and
a detection error correction part that corrects an angle detection error of said resolver by using the value of a Lissajous radius of a circular Lissajous waveform obtained from respective amplitudes of an output signal Scos output from said first output winding and an output signal Ssin output from said second output winding of said output windings of said two phases, which are obtained by the following expressions:
S cos= K·E ·sin ω t ·cos(θ)
S sin= K·E ·sin ω t ·sin(θ)
where K represents a voltage transformation ratio of said resolver; E represents said excitation voltage generated on said excitation winding by means of said power supply; ω represents an angular velocity of an excitation signal generated by exciting said excitation winding by means of said power supply; t represents time, and θ represents an electrical angle of said resolver.
2. The resolver as set forth in claim 1 , wherein an error amplitude A, an error amplitude B and an error phase C of said angle detection error are obtained from a maximum value MAX and a minimum value MIN of said Lissajous radius, and an angle θ m at a minimum point of said radius according to the following expressions:
error amplitude A= 2×sin −1 {(MAX−MIN)/(2×(MAX+MIN))};
error amplitude B= 2×sin −1 {(MAX−MIN)/(2×(MAX+MIN))}; and
error phase C=θm.
3. The resolver as set forth in claim 1 , wherein said resolver rotor is press-fitted to an end of a shaft of a motor built into an electric power steering apparatus.
4. The resolver as set forth in claim 3 , wherein said detection error correction part is incorporated in an ECU for controlling the driving of said motor, calculates said angle detection error of said resolver based on said output signal Scos and said output signal Ssin input to said ECU, stores correction data for said angle detection error, and corrects said angle detection error of said resolver based on said correction data.