A Coupled Piezoelectric/Single-Hall-Sensor Position Observer for Permanent Magnet Synchronous Machines

In recent years, several control methods have been proposed to reduce the torque ripple produced by permanent magnet synchronous machines [sinusoidal and trapezoidal back electromotive force (EMF)]. In these approaches, a drive system is used to control current harmonics based upon measured machine parameters or measured torque ripple. In general, the methods presented have utilized high-precision position encoders and thus a common perception is that such encoders are required for successful mitigation. In this paper, a position observer is developed that is shown to be suitable for control-based torque ripple mitigation. Additional advantages of the observer are that it achieves excellent start-up performance, requires no knowledge of the machine parameters, and is applicable to machines with an arbitrary back EMF waveform and stator slot configuration.