Patent ID: 7205916

Claim:
An apparatus for determining an angular position of a shaft using a resolver coupled to the shaft, the resolver including an excitation input, a sine output, and a cosine output, the apparatus comprising: a sine signal analyzer including an analog input operably coupled to the sine output and a cosine signal analyzer including an analog input operably coupled to the cosine output, each of the sine signal analyzer and the cosine signal analyzer comprising: a comparator configured for comparing the analog input to an analog feedback signal and generating a comparison result; a digital estimator configured to sample the comparison result and modify a digital estimate by an incremental adjustment amount responsive to the comparison result at an estimation frequency; a digital-to-analog converter configured to convert the digital estimate to the analog feedback signal; an amplitude analyzer configured to collect a digital estimate history at a sample frequency that is a binary multiple of an excitation frequency of the excitation input and determine an amplitude of the digital estimate substantially near the excitation frequency; and a polarity checker configured to determine a polarity of the digital estimate at the sample frequency; and a result calculator configured to evaluate the amplitude and the polarity of the sine signal analyzer and the amplitude and the polarity of the cosine signal analyzer to generate the angular position.