High-resolution sensorless position estimation using delta-sigma-modulated current measurement

Abstract

Sensorless speed and position control of surface mounted permanent magnet synchronous machines (SMPMSMs) is of special interest in industrial automation due to their high efficiency and simple design. However these types of machines have no geometrical saliencies and the exploitable magnetic anisotropies result solely from magnetic saturation and are therefore very small. The measurable position dependent current components resulting from injected high frequency voltages are hence very small and a high resolution current measurement is needed.This paper proposes a novel technique for injecting an alternating carrier voltage. The high frequency current components are measured using delta-sigma-modulators. Suitable design of the low-pass filters and appropriate processing of the measured current values allows to achieve a very high signal to noise ratio. The proposed analytical approach to separate the high frequency current components from the fundamental wave current portion avoids any interference between the current controller and the high frequency voltage injection. Therefore the extracted position information will not be affected by the fundamental current components even during transient conditions. The separation scheme is free of any motor parameters and can cope with significant nonlinear inductances.

Silent injection for saliency based sensorless control by means of current oversampling

“…One approach to ease this trade-off by using Delta-Sigma modulation for A/D conversion and an optimized demodulation scheme has been proposed in [7]. The convincing results emphasize the importance of research in this direction.…”

“…A particular way of combining both approaches, e.g. used in [7], yields a further ease of the noise-bandwidth-tradeoff. As shown in Fig.…”

“…Aiming to improve on [7] this paper proposes a different noise reduction approach. In standard drive systems the current is sampled once per PWM period, at the PWM center.…”

FPGA Implementation of a Hybrid Sensorless Control of SMPMSM in the Whole Speed Range

“…It is transformed to a reference frame in a negative rotating direction at the approximated carrier frequency. This is achieved by (9) through a low pass filter. The result is …”

“…Using a Delta-Sigma modulator, and with proper decimation filter design, this paper gives a promising solution for current measurement. The former work about high resolution position estimation with Delta-Sigma modulated current measurement was presented in [9]. The combination of signal injection and back EMF tracking estimators is a good solution for the PMSM sensorless control in the whole speed range.…”