Torque Regulation Theory and Sensorless Control Technology for Unipolar Salient Synchronous Permanent Magnet Motor Based on Unified Models

Salient synchronous permanent magnet motors (SynPMs) can be categorized into two types: 1) bipolar and 2) unipolar. Bipolar SynPM exhibits a two-period inductance within one electrical cycle, while unipolar SynPM has a one-period inductance. Torque regulation theory and sensorless control technologies for bipolar SynPM have been well-developed, relying on torque and electromotive force (EMF) models derived using conventional Park Transform. However, the model, theory and technologies remain underdeveloped for unipolar SynPM due to the distinct inductance periods. This article derives unipolar SynPM models that are unified with bipolar SynPM by proposing the Variant Park Transform (VPT). Based on the unified models, we establish the torque regulation theory for unipolar SynPM, and outline the procedure to adapt the well-developed sensorless control technologies from bipolar to unipolar SynPM. The VPT essentially represents a unique diffeomorphism for system linearization and time-invariance transformation. The derived torque and linear-time-invariant EMF models are experimentally validated on a unipolar SynPM. Additionally, we construct the instantaneous torque regulator for the unipolar SynPM, and demonstrate the procedure to adapt the advanced sensorless control technologies to unipolar SynPM by experiment.