Phase modulation type digital position detector

摘要

A digital mode phase modulation type position detector utilizing a resolver as the phase modulating element is disclosed in which the phase of the modulated signal is determined by comparing it with that of the follower signal, the phase of which is adjusted to that of the modulated signal. The phase difference between the modulated and the follower signal is detected at the ends of the half-periods thereof to effect the adjustment. To make the adjustment more precise, an adjustment circuit may further be provided which generates evenly spaced pulses in the present half-period of the follower signal at a frequency corresponding to the rotational speed of the resolver during the preceding half-period of the modulated signal. These pulses are used to adjust the phase of the follower signal more closely to that of the modulated signal. The position counter is also provided to accumulate the values corresponding to the phase differences between the modulated and the follower signal and/or the number of the pulses of the adjustment circuit. Thus, the accumulated value in the position counter represents the overall rotational angle of the resolver from the beginning of the counting up to the present instant.