US 2011/0031962 A1 · MAGNETIC POLE POSITION DETECTING DEVICE AND METHOD

Abstract

A magnetic pole position detecting device that can correctly acquire a magnetic pole position even if two magnetic sensors are arranged at an arbitrary interval receives sensor outputs “a” and “b” of two magnetic sensors arranged at a predetermined interval L along a magnetic pole arraying direction motor and a phase difference φ between the two sensor outputs “a” and “b”. When sin φ>δ, the device divides a·sin φ by b−a·cos φ to calculate tan θ and outputs a magnetic pole position θ=tan−1 {a·sin φ/(b−a·cos φ)}, and when sin φ≦δ, because a=sin θ and b=sin(θ+φ), the device outputs a magnetic pole position θ={sin−1(a)+cos−1(b)−φ}/2. Because φ=2π×L/(a magnetic pole pitch or the number of poles), using φ as a correction coefficient for the two sensor outputs “a” and “b”, a magnetic pole position error can be canceled even when the interval L is different from a theoretical value, thus the two magnetic sensors can be arranged at an arbitrary interval.

Claims6

Dependent claims

A magnetic pole position detecting device that calculates and detects, based on a phase difference between sensor outputs of two magnetic sensors among two or more magnetic sensors arranged at predetermined intervals along a magnetic pole arraying direction of a motor, a magnetic pole position where a movable unit is located, the magnetic pole position detecting device comprising:

a first operation system that detects, when an advanced phase side sensor output of the two sensor outputs is represented as “a”, a delay phase side sensor output is represented as “b”, and the phase difference is represented as φ, a magnetic pole position θ in the case of a sine value of the phase difference larger than a determination threshold by performing a following arithmetic operation:
θ=tan−1 {a·sin φ/(b−a·cos φ)};
and
a second operation system that detects the magnetic pole position θ in the case of a sine value of the phase difference smaller than the determination threshold by performing a following arithmetic operation:
θ={sin−1(a)+sin−1(b)−φ}/2.

2 more elements

A magnetic pole position detecting method comprising:

a first step of calculating a phase difference between sensor outputs of two magnetic sensors among two or more magnetic sensors arranged at predetermined intervals along a magnetic pole arraying direction of a motor by performing an arithmetic operation (2π×an arrangement interval of the two magnetic sensors)/(a magnetic pole pitch or a number of poles);
a second step of determining a magnitude relation between a sine value of the phase difference and a determination threshold;
a third step of calculating and detecting, when the sine value of the phase difference is larger than the determination threshold as a result of the determination at the second step, as a first magnetic pole position, an arctangent value of a tangent value having, as a numerator, a value obtained by multiplying an advanced phase side sensor output of the sensor outputs of the two magnetic sensors by the sine value of the phase difference and having, as a denominator, a value obtained by subtracting, from a delay phase side sensor output of the sensor outputs of the two magnetic sensors, a value obtained by multiplying the advanced phase side sensor output by a cosine value of the phase difference;
and
a fourth step of calculating and detecting, when the sine value of the phase difference is smaller than the determination threshold as a result of the determination at the second step, as a second magnetic pole position, a half value of a value obtained by subtracting the phase difference from a sum of an arcsine value of the advanced phase side sensor output and an arcsine value of the detail phase side sensor output.

2 more elements

Dependencies are inferred from the claim text.

Magnetic pole position detecting device and method

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Magnetic pole position detecting device and method

Life of this patent

Abstract

Claims6