Design, analysis and control of wireless motors

Abstract

In recent decades, wireless power transfer (WPT) is gaining more and more attention, as it takes definite advantages of large capacity, high efficiency, and strong security. Hence, this technology offers a brand-new power-supply solution and changes the conventional style of energy utilization for electric-driven devices, such as electric vehicles, customer electronics, and implantable medical devices. This study mainly focuses on some research highlights in the design, control, and application of various wireless motors. To be more specific, a series of robust wireless motors and corresponding position detection methods are studied and devised, including wireless shaded-pole induction motor (IM), the sensorless control strategy for wireless switched reluctance (SR) motor, and wireless resolver for all wireless motors. The study of wireless shaded-pole IM is to increase the portability of electric motors. Hence, the wire limitation can be avoided. Its research highlights comprise four parts. First, the power source and load motor can be physically isolated, so the electric motor can be employed in sealed environments. Second, as the motor side does not involve any controller or battery, the secondary side is very robust and can provide maintenance-free operation. Third, only one pair of WPT coils are employed in this system, the secondary side can be packed easily. Fourth, the structure of the shaded-pole IM is very simple and robust. Hence, the secondary side can offer maintenance-free operation over a wide speed range. The study of position sensorless control strategy for wireless SR motor is to advance the drive capability of the wireless motor. Particularly, only the transmitter current need to be measured, while the motor terminal measurement, such as motor voltage or current, is not required. Thus, the secondary side can be simple and robust. Besides, as this system does not require any wireless communication device, communication delay can be avoided. Thus, it is very suitable for high-speed operation. The study of the wireless resolver is to offer a robust solution for position signal acquisition for wireless motors. The proposed wireless resolver can provide a real-time position signal for the controller while reserving the merit of robustness. Meanwhile, the placement of WPT coils is carefully designed. Thus, the dimension of the secondary side is highly reduced, and the crosstalk between unrelated coils can be eliminated. Besides, the power consumed by the wireless resolver is negligible relative to the input power of the motor. Finally, to evaluate and verify the proposed wireless motors and position detection methods, theoretical analyses and prototype experimentations are performed to provide in-depth discussions and validations for the wireless shaded-pole IM, wireless sensorless SR motor, and wireless resolver.