Resolver-to-digital converting apparatus, method and program

1. A resolver-to-digital converting apparatus for calculating a resolver rotational angle from two-phase sampling values that are the result of sampling output signals of two phases, which are obtained from a single-phase-excited, two-phase output resolver, at peak timings of a waveform, comprising:

a determination unit for determining whether each of the two-phase sampling values has deviated from a prescribed path of rotation by more than a predetermined amount when the two-phase sampling values are represented by orthogonal coordinates;

a correction processing unit, responsive to a determination by said determination unit that the predetermined amount has been exceeded, for applying a correction to the two-phase sampling values using an equation of a tangent to the path of rotation at a point on the path of rotation at which the previous resolver rotational angle was obtained; and

an angle calculation unit for obtaining a resolver rotational angle at the corrected two-phase sampling values obtained by said correction processing unit.

2. A resolver-to-digital conversion method for calculating a resolver rotational angle from two-phase sampling values that are the result of sampling output signals of two phases, which are obtained from a single-phase-excited, two-phase output resolver, at peak timings of a waveform, comprising the steps of:

determining whether each of the two-phase sampling values has deviated from a prescribed path of rotation by more than a predetermined amount when the two-phase sampling values are represented by orthogonal coordinates;

in response to a determination that the predetermined amount has been exceeded, applying a correction to the two-phase sampling values using an equation of a tangent to the path of rotation at a point on the path of rotation at which the previous resolver rotational angle was obtained;

obtaining a resolver rotational angle at the corrected two-phase sampling values obtained by correction processing; and

controlling a motor with the obtained resolver rotational angle.

3. A resolver-to-digital conversion method for calculating a resolver rotational angle from two-phase sampling values that are the result of sampling output signals of two phases, which are obtained from a single-phase-excited, two-phase output resolver, at peak timings of a waveform, comprising the steps of:

obtaining average values of the two-phase sampling values in the past;

determining whether differences between the latest two-phase sampling values, referred to as “present values” hereinafter, and previous two-phase sampling values exceed predetermined tolerance values;

if a determination is made that a tolerance value has been exceeded, obtaining a first distance between the present value and the previous value and a second distance between the average value and the previous value;

adopting the present value as a correction candidate value if the first distance is less than the second distance, and adopting the average value as the correction candidate value if the first distance is equal to or greater than the second distance;

when the previous value is represented by orthogonal coordinates, obtaining a correction value by substituting the correction candidate value into an equation of a tangent that passes through the previous value on a circle that passes through the previous value;

adopting the correction candidate value as the correction value if the distance between the correction value and the previous value is greater than the distance between the correction candidate value and the previous value;

obtaining a first slope at the average value;

obtaining a second slope at the present value;

obtaining a third slope at the correction value; and

obtaining a resolver rotational angle from a slope, from among the first, second and third slopes, that is closest to a slope at the previous value; and

controlling a motor with the obtained resolver rotational angle.

4. The method according to claim 3 , wherein the first distance is a distance obtained by projecting the present value and the previous value onto either of the orthogonal coordinate axes, and the second distance is a distance obtained by projecting the average value and the previous value onto either of the orthogonal coordinate axes.

5. The method according to claim 3 , wherein if values that are the result of sampling the output signals of two phases at the timings of nodes of the waveform deviate from the center of the circle by more than a predetermined amount, then the values that are the result of sampling at the peak timings are corrected by the amount of the deviation.