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Concrete embedded sensors play a very important role in structural health monitoring. However, the time of endurance of sensors remains a performance bottleneck and sensors need to be charged without damaging the structure as well. Wireless power transfer (WPT) technology is a promising approach to solving this problem. However, the electromagnetic characteristics of concrete medium can cause WPT systems to be untuned and can reduce the energy transmission efficiency of the system. In this paper, the induced medium loss and eddy current loss of a WPT system in concrete are calculated using analytical equations and finite element analysis method. The equivalent circuit model of a concrete–air transmedia WPT system is established according to the calculated losses and a composite tuning control technology is proposed based on the above analysis. In addition, the composite tuning control technology combines the advantages of frequency-modulation tuning and dynamic compensation tuning to ensure the overall resonance of the WPT system. The tuning control technology can ensure the whole resonance of the WPT system and make the natural resonant frequencies of primary and secondary sides consistent. The experimental results show that compared with the untuned control technology, the output power and efficiency of the tuned control system increased by 73% and 11.05%, respectively. The proposed tuning control technology provides direction for future charging of concrete-embedded sensors. [ABSTRACT FROM AUTHOR]

The relay inductively coupled power transfer (ICPT) system is a typical nonlinear and high-order system that is composed of the inverter, the resonant tanks, the relay structure, the rectifier, and the filter. Additionally, the disturbance signals (such as external disturbance) and dynamic perturbations (such as parametric uncertainties) are unavoidable in this system. Therefore, a closed-loop system with an H\infty controller is designed under the external disturbance and parametric uncertainties in this paper. In order to achieve the robust stability and the robust performance (RSRP) of the closed-loop system with an H\infty controller, the generalized state-space averaging method is used to establish the linear model of the relay ICPT system first, and a linear fractional transformation of the nominal model and the parametric uncertainties is discussed then. The RSRP of the designed H\infty controller is tested by the structured singular value. The results of the practical experiment further verify the RSRP of the closed-loop system. [ABSTRACT FROM PUBLISHER]

This paper analyses the relationship between the coil design parameters and the system performance, including power transfer efficiency and amount, when circular flat spiral coils are adopted in a wireless power transfer (WPT) system. Coil design variables including outer radius, inner radius, channel width and coil turns are thoroughly studied to improve the system performance with a limited maximum outer radius for practical purposes. A two-coil WPT system has been built to verify the analysis, and the experimental results show good consistency with the theoretical calculations and simulation results, which show that the coil design parameters have a significant impact on the system performance, even with the same coil size. In the experiments, the coil-to-coil distance is 150 mm, the maximum coil outer radius is limited in 300 mm, and the DC input voltage and the load resistance are 100 V and 5 Ω, respectively. When the coils are tightly-wound in the most traditional way to maximize the coil size, the coil-system efficiency is 62.6% with only 4.5 W load power. In contrast, the efficiency optimized coil can improve the coil-system efficiency to 91.2% with the outer radius stayed the same. Besides, when the power transfer efficiency and amount are considered simultaneously, the system can achieve 1279 W load power with 85.94% coil-system efficiency. [ABSTRACT FROM AUTHOR]