Resolver to digital converter

An apparatus for converting amplitude modulated analog signals into a digital signal representative of the position and a digital signal representative of the velocity of a movable element, and including an electronic control transformer circuit for providing respective products of sine and cosine components of said analog signal respectively times the cosine and sine of said digital signal and for summing said products so as to produce an AC error signal, synchronous converter means for converting said Ac error signal into a DC error signal, an analog loop compensation circuit for generating an analog signal from said DC error signal, and conversion means for converting said analog signal into a digital velocity signal, the improvement comprising, in combination:

• noise-shaping, oversampling A/D converter means connected to the output of said analog lop compensation circuit;
• digital decimation filter means connected to the output of said A/D converter means for converting the oversampled output from said A/D converter means to a digital velocity signal representative of the velocity of said element;
• digital integration means connected to the output of said digital decimation filter means so as to provide said digital position signal;
• and
• digital modulator means connected to the output of said digital integration means so as to provide a bit-reduced form of said digital position signal as feedback to said control transformer, thereby enhancing the resolution of said control transformer.

Improved apparatus for converting the analog output signals from an angle resolver excited by excitation signals, into digital signals representation of the velocity and position of a rotor of said resolver, said apparatus including, in combination:

• electronic control transformer circuit means for providing respective products of sine and cosine components of said analog signal respectively times the cosine and sine of said digital signal and for summing said products so as to produce an analog error signal;
• analog band pass filter means for suppressing any frequency component in said analog error signal outside of a critical frequency range, for passing frequencies within said critical frequency range with substantially flat frequency response, and rolling off between these two behaviors over a transition band;
• means for synchronously demodulating the band pass filtered analog error signal;
• analog-to-digital converter means, responsive to digital discrete oversampling signals, for converting the demodulated analog error signal into oversampled digital form;
• decimator means for digitally low-pass filtering the oversampled quantized signal output of said converter means so as to suppress frequencies above one-half of the desired discrete time sample frequency and including first digital accumulator means for integrating said output of said converter means, the output signal from said decimator means being said digital velocity signal;
• second digital accumulator means connected to the output of said decimator means for providing a second stage of integration for said apparatus;
• and
• digital modulation means connected to accept the output signals from said second digital accumulator means, the modulation rate of said digital modulation means being controlled responsively to a modulation waveform so as to provide said position signal.