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A Wireless Power Transfer (WPT) system based on magnetic resonant coupling is applied to a small electrical Unmanned Aerial Vehicle (UAV) to recharge its battery. The transmitting coil is assumed to be on a terrestrial base station, while the receiving coil is onboard. The operation frequency is fixed to 150 kHz. Key aspects for this kind of application are the reduction of the weight of the onboard WPT system while maintaining high WPT efficiency and avoiding EMC/EMI problems on the drone electronic system. In this study, the feasibility of the WPT charging system applied to a demonstrative drone has been proved

Impedance network boundary conditions (INBCs) are implemented in the finite-difference time-domain (FDTD) method to analyze the electromagnetic field around penetrable shield structures. The shield region is eliminated from the computational domain and the INBCs are applied on the new boundary surfaces, i.e., shield surfaces, to take into account the field discontinuity produced by the shield. The INBCs represent an important extension of the well-known surface impedance boundary conditions (SIBCs) since the INBCs model accurately the coupling of the electromagnetic fields through penetrable shields and lead to a significant reduction of the number of the FDTD unknowns. The INBC expressions are given analytically in both frequency and time domains, and the INBC implementation in a FDTD code is discussed. The proposed INBC-FDTD method is numerically efficient because the resulting convolution integrals are recursively solved. Furthermore, approximate time-constant INBCs are proposed which are valid for many practical applications. The analysis of transient electromagnetic fields around penetrable conductive shields in simple test configurations are presented and compared with the analytical solution

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An efficient model is presented for including penetrable conductive shields in the FDTD method. The shielding panels of negligible thickness are eliminated from the computational domain and replaced by impedance network boundary conditions (INBC's). The implementation of the INBC's in a 3D FDTD code is presented. The proposed method is applied to predict the electromagnetic field in complex shielded configurations

A near-field wireless power transfer (WPT) technology is applied to recharge the battery of a small size drone. The WPT technology is an extremely attractive solution to build an autonomous base station where the drone can land to wirelessly charge the battery without any human intervention. The innovative WPT design is based on the use of a mechanical part of the drone, i.e., landing gear, as a portion of the electrical circuit, i.e., onboard secondary coil. To this aim, the landing gear is made with an adequately shaped aluminum pipe that, after suitable modifications, performs both structural and electrical functions. The proposed innovative solution has a very small impact on the drone aerodynamics and the additional weight onboard the drone is very limited. Once the design of the secondary coil has been defined, the configuration of the WPT primary coil mounted in a ground base station is optimized to get a good electrical performance, i.e., high values of transferred power and efficiency. The WPT design guidelines of primary and secondary coils are given. Finally, a demonstrator of the WPT system for a lightweight drone is designed, built, and tested.