Harmonic Mitigation of Rotor Position Quantization Errors in High-Speed PMSM Applications With Low-Resolution Encoders

Abstract

Low-resolution encoders (LREs) in high-speed permanent magnet synchronous motor (PMSM) digital control systems face significant challenges from quantization errors. Due to spectral aliasing, high-frequency quantization-errors fold into the control bandwidth. These errors manifest as low-frequency harmonics and cause torque ripples. An improved scheme based on a vector-tracking observer is proposed to mitigate these aliased errors. First, a quantization-error decoupling method (QEDM) utilizes position increments and an auxiliary observer to address error discontinuity and information deficiency. Subsequently, an exact model-based error extraction (EMEE) module is employed for closed-loop feedback correction of residual errors. Experimental results show significant suppression of aliased position-error harmonics. As a result, the current harmonics and torque ripples are reduced. The proposed scheme (PS) provides a practical solution for employing LREs in high-speed applications.