H^∞ control for a sensorless permanent-magnet synchronous drive

A robust two degrees of freedom speed controller for a permanent-magnet synchronous motor (PMSM) drive system without using shaft sensor is proposed. The feedback controller and the prefilter are designed in a simple way by extending the utility of the H^∞ optimisation procedure. The feedback controller is designed to meet robust stability and disturbance rejection specifications by using the H^∞ loop shaping design procedure. For the prefilter the free contractive parameter resulting in H^∞ control is used to improve the robust model matching properties of the feedback system. A DSP-based sensorless PMSM drive under the field-oriented control framework is established for experimentally verifying controller performance.