Self-Detachable Through-Metal Acoustic Wireless Power Transfer.

Unlike electromagnetic waves, acoustic vibrations waves can be used to transfer power directly through metal structures without being shielded. In this article, a novel design of a self-detachable acoustic wireless power transfer system that can be used to transfer power through the thickness of a steel plate is presented, which does not require the use of any couplant. Electro-permanent-magnets (EPMs) were used to provide magnetic clamping force along the perimeter of the receiver transducer disk to enhance coupling to the steel plate, while the transmitter transducer was bonded to the other side of the plate. The EPM clamping force can be switched ON/ OFF electronically with low power consumption. Unlike past work reliant on additional bonding materials or liquid/gel couplant, this approach enables the receiver to be attached and detached at will, opening up the possibility of a simple charging pad for unmanned aerial vehicles (UAVs) or other consumer devices for harsh environment applications. Power transfer efficiency up to 63% was achieved, and the effect of varying steel plate thickness and clamping force was also investigated. A finite element model was also constructed to understand the vibration mode shape.

Ultrasonic Lamb Waves for Wireless Power Transfer.

Ultrasonic guided plate waves (Lamb waves) can be used to transfer power along the length of metal plates, achieving longer distance wireless power transfer (WPT), while not being impeded by electromagnetic shielding from the metal plate. In this article, a fundamental study on the performance of Lamb wave WPT is presented, including modeling, simulations, and experimental verification. By using Macro-Fiber Composite (MFC), d33 -mode, piezoelectric transducers bonded to a [Formula: see text] mm aluminum plate using an epoxy, power transfer of 0.47 W with 56% overall power transfer efficiency was achieved at a 204-mm distance. The measured frequency response of the power transfer efficiency matches well with the simulated results, and the effects of complex load impedance matching and transducer sizing were investigated. It is shown that the location where the efficiency is maximized roughly corresponds to the zero-order symmetrical mode (S0) standing wave patterns due to reflections from the plate edges. For practical implementation, the effect of using different methods to temporarily or permanently bond the MFC transducers to the metal plate was also investigated, as well as the effect of electrically grounding the metal plate.