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Wireless power transfer (WPT) technology has drawn much attention due to its advantages such as safety, convenience, and non-contact. For some movable devices such as intelligent inspection robot, the constant output voltage is very important to ensure its normal operation. In order to improve the system efficiency and steadiness of output voltage, a maximum efficiency tracking and constant voltage charging method is proposed for the dynamic WPT system. In this method, the mutual inductance and optimal input voltage can be estimated accurately no matter the coupling coefficient and equivalent load change or not. The simulation and experimental results have shown that the WPT system realize maximum efficiency tracking and constant voltage charging when the resistance is changed from 10Ω to 5Ω, and the same result was achieved when the mutual inductance is altered from 20μH to 10μH. INDEX TERMS Wireless power transfer, optimal input voltage matching, maximum efficiency tracking

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Electrohydrodynamic (EHD) conduction pumping technology offers a unique way to control flow distribution in multi-scale environments. In EHD conduction, the interaction between an applied electrical field and dissociated electrolyte species in a dielectric fluid generates a net body force within the fluid resulting in a net flow in the desired direction. EHD conduction pumps have remarkable potential due to their lack of moving parts, simple designs, low power consumption, and ability to operate in microgravity. The performance of these pumps increases at small scales and they have been previously proven effective for heat transfer enhancement, with possible applications in electronics cooling and more, both terrestrially and in space. Flow distribution control using EHD conduction pumps has been previously examined in macro-and meso-scale configurations, confirming effective redistribution of flow and recovery from mal-distribution, in single and two-phase flows, at those size scales. This study examines single-phase flow distribution control among two parallel microchannels, 500 microns tall, via upstream EHD conduction pumps. The working fluid was the refrigerant R-123 operated at ambient conditions.

The misalignment of the resonant coils in wireless power transfer (WPT) systems causes a sharp decrease in transfer efficiency. This paper presents a method which improves the misalignment tolerance of WPT systems. Based on electromagnetic simulations, the structural unit parameters of the electromagnetic material were extracted, and an experimental prototype of a four-coil WPT system was built. The influence of electromagnetic metamaterials on the WPT system under the conditions of lateral misalignment and angular offset was investigated. Experiments showed that the transfer efficiency of the system could be maintained above 45% when the transfer distance of the WPT system with electromagnetic metamaterials was 1 m and the resonant coils were shifted laterally within one coil diameter. Furthermore, the system transfer efficiency could be stabilized by more than 40% within an angle variation range of 70 degrees. Under the same conditions, the transfer efficiency of a system without electromagnetic metamaterials was as low as 30% when lateral migration occurred, and less than 25% when the angle changed. This comparison shows that the stability of the WPT system loaded with electromagnetic metamaterials was significantly enhanced.