Precise Rotor Position Detection for Skewed-PM Axial Flux Motors Using Orthogonal Third-Harmonic Hall Signals

In this article, a novel detection method without Clarke transformation and prefiltering, named third-harmonic synchronous reference frame-phase locked loop (THSRF-PLL), is proposed to improve the rotor detection accuracy of the skewed-PM axial flux motor (SPMAFM). First, the airgap magnetic field (AMF) characteristics of the SPMAFM are analyzed to propose the installation method of the two sets of three-phase LHSs. Then, the decoding algorithm based on the orthogonal third harmonics is presented. Meanwhile, under no-load and load conditions, the position detection accuracy of the proposed method at different speeds is calculated and compared with two previous methods. The results indicate that the proposed method demonstrates higher prediction accuracy across the entire speed range. Finally, a prototype of the SPMAFM with the two sets of three-phase LHSs installed was manufactured and tested under both steady-state and dynamic conditions to verify the effectiveness of the proposed method and simulation results.