DSP based all-digital resolver-to-digital conversion using DSRF-PLL

Nowadays all-digital resolver-to-digital conversion is popularly invested for space-limited applications. However time delay is inevitable in demodulation part when frequency shifting algorithm used. Furthermore, the angle calculation result is affected by time delay. So the synchronous demodulation is analyzed in this paper to void time delay. The demodulated sine and cosine signals always exist with amplitude and quadrature errors. In order to eliminate the influence of these two errors, the double synchronous reference frame-based phase-locked loop (DSRF-PLL) is investigated in the angle calculation part. DSRF-PLL removes the angular position error caused by the amplitude error and makes the position error caused by the quadrature error to be a constant value, which can be easily compensated in the software. So the angular position can be detected with no time delay and error. The presented all-digital resolver-to-digital conversion scheme is verified by the simulation and experimental results at the end of this paper.