Patent ID: 8402077
Filing Date: 2013-03-19
Classification: G01D

Abstract:
1. An amplitude calculation apparatus of an output signal of an encoder, comprising: a sampling means for sampling, at the same timing, an A-phase sine wave signal or a signal resembling said A-phase sine wave signal and a B-phase sine wave signal or a signal resembling said B-phase sine wave signal differing in phase by exactly a predetermined angle and thereby outputting an A/D converted value A of said A-phase sine wave signal or a signal resembling said A-phase sine wave signal and an A/D converted value B of said B-phase sine wave signal or a signal resembling said B-phase sine wave signal; an angle detection circuit for finding a phase angle θ at different sampling points of a Lissajous waveform obtained by plotting the A/D converted value A of said A-phase sine wave signal or a signal resembling said A-phase sine wave signal and the A/D converted value B of said B-phase sine wave signal or a signal resembling said B-phase sine wave signal at the sampling points by said sampling means on an X-axis and a Y-axis; a means for finding a quadrant n of said phase angle θ from polarities of said A/D converted value A and said A/D converted value B, and converting the phase angle θ of the quadrant n to a phase angle θ′ of a quadrant 1, where,  where n is 4 or a smaller natural number; a coefficient storing means for dividing said Lissajous waveform into a predetermined number of angle areas in said quadrant 1 and presetting and storing in advance an A-phase coefficient α and a B-phase coefficient β in accordance with the divided angle areas, in which case, said coefficients being set so that α|A|+β|B| approximates a radius of a theoretical Lissajous waveform; and a calculating means for calculating the radius of said Lissajous waveform as α|A|+β|B| and making said calculated radius the amplitude of the output signal of the encoder.