Absolute position detection apparatus and error compensation methods therefor
First Claim
1. In an absolute position detection method wherein one or more sets of sine and cosine waves are generated within a cycle of a rotating device, the generated sine and cosine waves are analog-to-digital converted into digital values, and error compensation is performed using an arithmetic process to compensate for errors including offset, amplitude and phase errors on the digital values, the error compensation method comprises the steps of:
- determining maximum and minimum values of the digital values, said maximum and minimum values representing peak values of the sine and cosine waves;
calculating an amplitude value for each of said sine and cosine waves using a difference between said maximum and minimum values;
determining an amplitude damping factor which varies as a function of an angular speed of said rotating device;
calculating an amplitude compensation factor for each of said sine and cosine waves as a function of said amplitude value, said amplitude damping factor and a reference amplitude value;
amplitude compensating each of said sine and cosine waves by multiplying each of said digital values by said amplitude compensation factor, thereby adjusting the amplitude of each of said sine and cosine waves to a reference amplitude.
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Abstract
An absolute position detection apparatus which comprises sine and cosine wave generators for generating one or more sets of sine and cosine waves within a cycle, analog-to-digital converters for converting the incoming sine and cosine waves generated by the sine and cosine wave generators into digital values. An arithmetic unit is used for calculating a compensation for errors including offset, amplitude and phase errors on the basis of the digital values from the analog-to-digital converters. In the apparatus, the arithmetic unit operates on a phase angle from phase angles found by the arithmetic performed prior to or during said error compensations and the digital values from the analog-to-digital converters, whereby a low-priced, highly reliable absolute position detection apparatus can be achieved without the addition of compensation circuits to the hardware.
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Citations
21 Claims
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1. In an absolute position detection method wherein one or more sets of sine and cosine waves are generated within a cycle of a rotating device, the generated sine and cosine waves are analog-to-digital converted into digital values, and error compensation is performed using an arithmetic process to compensate for errors including offset, amplitude and phase errors on the digital values, the error compensation method comprises the steps of:
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determining maximum and minimum values of the digital values, said maximum and minimum values representing peak values of the sine and cosine waves; calculating an amplitude value for each of said sine and cosine waves using a difference between said maximum and minimum values; determining an amplitude damping factor which varies as a function of an angular speed of said rotating device; calculating an amplitude compensation factor for each of said sine and cosine waves as a function of said amplitude value, said amplitude damping factor and a reference amplitude value; amplitude compensating each of said sine and cosine waves by multiplying each of said digital values by said amplitude compensation factor, thereby adjusting the amplitude of each of said sine and cosine waves to a reference amplitude. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. In an absolute position detection method wherein one or more sets of sine and cosine waves are generated within a cycle of a rotating device, the generated sine and cosine waves are analog-to-digital converted into digital values, and error compensation is performed using an arithmetic process to compensate for errors including offset, amplitude and phase errors on the digital values, the error compensation method comprising the steps of:
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when an angle of said digital values falls within predetermined ranges of 0°
, 90°
, 180° and
270°
, calculating respective amplitudes R0, R90, R180 and R270 from a sum of the square of the digital value representing the sine wave and the square of the digital value representing the cosine wave;calculating an amplitude compensation factor for each of said sine and cosine waves as a function of R0, R90, R180 and R270; determining an amplitude damping factor which varies as a function of an angular speed of said rotating device; amplitude compensating each of said sine and cosine waves by multiplying each of said digital values by said amplitude compensation factor, thereby adjusting the amplitude of each of said sine and cosine waves to a reference amplitude. - View Dependent Claims (16, 17, 18)
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19. An absolute position detection apparatus, comprising:
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sine and cosine wave generators (1a, 1b, 2a, 2b) for generating one or more sets of sine and cosine waves within a cycle; analog-to-digital converters (5a, 5b) for converting the incoming sine and cosine waves generated by said sine and cosine wave generators (1a, 1b, 2a, 2b) into digital values; and an arithmetic unit (17) for performing arithmetic to compensate for errors including offset, amplitude, and phase errors on the basis of the digital values from said analog-to-digital converters (5a, 5b), said arithmetic unit determining maximum and minimum values of the digital values, said maximum and minimum values representing peak values of the sine and cosine waves, calculating an amplitude value for each of said sine and cosine waves using a difference between said maximum and minimum values, determining an amplitude damping factor which varies as a function of an angular speed of said rotating device, calculating an amplitude compensation factor for each of said sine and cosine waves as a function of said amplitude value, said amplitude damping factor and a reference amplitude value, and amplitude compensating each of said sine and cosine waves by multiplying each of said digital values by said amplitude compensation factor, thereby adjusting the amplitude of each of said sine and cosine waves to a reference amplitude. - View Dependent Claims (20, 21)
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Specification