| CPC G01D 18/00 (2013.01) [G01D 5/16 (2013.01); G01D 5/145 (2013.01); G01D 18/002 (2013.01)] | 9 Claims |
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1. A correction apparatus for use with a rotating magnetic field sensor, the rotating magnetic field sensor including:
a detection signal generator for generating a first detection signal and a second detection signal each having a correspondence with a rotating magnetic field; and
a detector for generating a detection value based on the first and second detection signals, the detection value having a correspondence with the rotating magnetic field,
the correction apparatus being configured to correct the first and second detection signals, and comprising:
a correction processor configured to perform correction processing for generating a first corrected detection signal from the first detection signal and generating a second corrected detection signal from the second detection signal, wherein
the first detection signal contains a first ideal component, a first signal error component, and a second signal error component,
the second detection signal contains a second ideal component, a third signal error component, and a fourth signal error component,
the first ideal component is expressed as A0 sin θ, the second ideal component is expressed as A0 cos θ, the first signal error component is expressed as −A1 sin((N−1)θ+α), the second signal error component is expressed as −A2 sin((N+1)θ+α), the third signal error component is expressed as A1 cos((N−1)θ+α), and the fourth signal error component is expressed as −A2 cos((N+1)θ+α), where θ represents an angle that has a correspondence with a rotating field angle, the rotating field angle being an angle that a direction of the rotating magnetic field at a reference position forms with respect to a reference direction in a reference plane; N is an integer greater than or equal to 1; A0, A1, and A2 are real numbers other than 0; and α is a predetermined angle,
a computed value of the angle θ without the correction processing being referred to as an uncorrected angle θp, the uncorrected angle θp contains an error, and when the angle θ varies with a predetermined period T, the error of the uncorrected angle θp contains a component resulting from the first to fourth signal error components and varying with a period of T/N, and
the first detection signal being referred to as S1 and the second detection signal being referred to as S2, the first corrected detection signal is expressed as S1−A3 sin((N−1)θp+α), and the second corrected detection signal is expressed as S2+A3 cos((N−1)θp+α), where A3 is a real number such that |A1+A2+A3| is less than |A1+A2|.
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