Patent ID: 9182251
Filing Date: 2015-11-10
Classification: G01D

Abstract:
1. An angle detector comprising: an AD converter configured to analog-to-digital convert plural-phase signal waves having respective different phases obtained by amplitude-modulating an excitation wave by a rotation angle of a rotation shaft; a corrector configured to receive an excitation signal which has a reference phase position representing a reference phase timing in an excitation period of the signal wave and the converted plural-phase signal waves from the AD converter, detect a zero-cross phase of a square sum average signal having a period half the excitation period and plural zero-cross points in the excitation period, and delay a phase of the excitation signal by an amount corresponding to a phase difference between the excitation signal and the signal wave, the corrector delaying the phase of the excitation signal by a shift amount equivalent to the phase difference from the reference phase position, according to a position of the zero-cross phase in any of plural phase intervals obtained by equally dividing the excitation period and a phase shift correction direction; a wave detector configured to perform synchronous detection to an output signal from the AD converter in synchronization with the excitation signal whose phase is corrected; and an angle calculator configured to calculate an estimated rotation angle using an output signal of the wave detector and output the estimated rotation angle to the AD converter.