Permanent-Magnet Flux Adaptation for Sensorless Synchronous Motor Drives

This paper deals with estimation of the permanent-magnet (PM) flux in sensorless synchronous motor drives. A back-electromotive-force (back-EMF)-based observer is augmented with an adaptation law for the PM flux magnitude. The gains of the augmented observer are designed based on the linearized model. The proposed design makes PM flux estimation independent of speed estimation and enables straightforward analytical pole placement of the observer. Practical design guidelines are given. The proposed design is evaluated by means of simulations and laboratory experiments using a 2.2-kW interior PM synchronous motor drive.