Design, analysis and control of multi-phase wireless motors

Abstract

Originating over a hundred years ago, wireless power transfer (WPT) has drawn the attention of worldwide researchers and manufacturers due to its high flexibility and strong safety. Beyond wireless transmission of electricity, WPT can also convert electrical energy to other formats of energy, namely mechanics, thermology, optics, and magnetism via different media. To build wireless energy conversion from electrical energy to mechanical energy, explorations in wireless motors have been carried out to fully utilize the advantages of WPT. With no physical contact between the transmitter and the receiver, the motor and the receiver-side circuit can work in a sealed cover for fewer environmental impacts, showing great potential in electric powertrains, industrial manufacturing, and domestic applications. Among electric motors, multi-phase motors are widely applied due to higher power density, smoother operation, and higher efficiency over single-phase motors. This study focuses on the design, control, and implementation of multi-phase wireless motors. Circuit design, feedback transmission, and control strategies for various motor types are studied. Specifically, several designs of wireless hybrid stepper motors (HSMs), wireless permanent-magnet brushless DC (PM-BLDC) motors, and wireless switched reluctance motors (SRMs) are presented. The study of wireless HSM is to form a robust and high-performance wireless motor system without feedback. Thanks to the unique structure of HSMs, wireless HSMs can offer precise speed and position control and bidirectional rotation by controlling motor currents only; no microcontroller is required at the receiver side. Two designs are presented in total; the first one aims to achieve a simple structure with basic control, while the second one achieves precise speed and position control performance and smooth operation with multiple working modes and pulse frequency modulation (PFM). The study of wireless PM-BLDC motors aims to offer contactless position feedback for commutation and accurate speed control under various speeds and loads. The motor-attached Hall effect sensor is powered wirelessly, and the modulated sensor output can be extracted at the transmitter side for commutation and speed control. The low latency allows high-speed motor commutation for high-speed operation. Sigma-delta modulated pulse frequency modulation (Σ-Δ PFM) is adopted in part to reduce the switching loss during the whole regulation process. The study of frequency-modulated speed control for wireless SRMs aims to maintain zero voltage switching (ZVS) operation during the whole regulation process. Combined with closed-loop speed control, the system achieves precise control performance with reduced switching loss. Finally, to evaluate and verify the proposed wireless motors and related technologies, theoretical analysis, computer simulations, and experimental verifications are conducted to provide in-depth discussions and validations for wireless HSMs, wireless PM-BLDC motors, and wireless SRMs.