Modeling and optimization of the magnetically coupled resonant wireless power transfer used in rotary ultrasonic machining process

The existing method of contactless power transfer based on inductive power transfer (IPT) used in rotary ultrasonic machining (RUM) involves a small transmission distance (0.1–1 mm). A novel magnetically coupled resonant wireless power transfer (MCR WPT) technique for the RUM is proposed to increase the transmission distance of the RUM system. In addition, a self-resonance theory is proposed to eliminate the need for a secondary compensation capacitor. This article presents the design approach, simulation, and experimental study. First, a mutual inductance model of two spiral tube coils is proposed to analyze the influence of transmission distance on the transmission characteristics of the novel RUM system. The results show a critical coupling distance to achieve maximum output power. Second, the factors affecting the critical coupling distance are studied through a theoretical model. Finally, experiments are conducted, and experimental results are agreed with the theoretical results. In addition, the output power calculated by the theoretical model can be used to predict the amplitude of the ultrasonic vibrator which determines the surface quality of the workpiece and the tool life.