CAREER: Towards 3D Omnidirectional and Efficient Wireless Power Transfer with Controlled 2D Near-Field Coil Array

Wireless power transfer (WPT) technology, like wireless communications now dominating end-user applications, is poised to take over many of the wired power deliveries today. However, one of the major limitations that prevents wider adoption of WPT is its stringent orientation and alignment requirements in existing implementations. Current efforts from both academia and industry resulted in either 3-dimensional (3D) multi-coil structures that are too bulky for most applications or 2-dimentional (2D) planar coil arrays that only addressed misalignment issues while leaving the orientation issue unresolved. The goal of this CAREER project is to achieve efficient omnidirectional WPT systems with new spatial calibration methodologies that can dynamically shape the magnetic field direction to match the orientation of the receiver device for optimum power transfer without using a bulky 3D structure. By addressing this major challenge of WPT, this project will benefit a wide range of applications, from low-power implantable or ingestible medical devices with orientation/location uncertainties inside the body to higher-power consumer electronics, without the need for careful orientation and position alignment with the wireless transmitter, revealing the full potential of wireless power technology. In terms of education, this project will provide undergraduate students with chip-level design experience, opportunities to interact with industry professionals on practical applications, and new courses. These education activities will bridge gaps between university education and industry needs with better training of students to address the nationwide workforce demand in industry. The outreach activities in close collaboration with various organizations will also help develop a broader STEM workforce by increasing the participation of students from various groups and providing them with more opportunities to obtain the knowledge and skills to pursue career goals as engineers or scientists. To achieve 3D omnidirectional WPT without using bulky 3D structures, a controlled 2D near-field coil array will be developed to shape the magnetic field with real-time spatial calibration techniques to determine and generate the optimal phases and amplitudes driving the coils in the array. Three system-level approaches will be explored for different application scenarios with different constraints, namely: 1) Receiver Backward Excitation, which is inspired by the theory of reciprocity in classical electromagnetism to sense the receiver-driven signals in reverse to pick up potentially optimum driving signals at the transmitter; 2) Transmitter Forward Excitation, to analyze the reflected impedance by sensing the transmitter-driven voltages and currents, and then calculate the optimum driving parameters; 3) Feedback Guided Searching, by optimizing the search space and then utilize feedback signals from the receiver to search for optimal driving parameters. In addition, a pseudo-2D approach with thin-film receiver structure will also be developed when the transmitter does not have the flexibility to implement a planar multi-coil array. In each approach, theoretical analysis and hardware development of system-level topologies, chip-level integrated circuits, and closed-loop control techniques will be performed for prototyping and measurement. To improve system efficiency, adaptive optimizations of coils and resonant links and development of nonlinear power and voltage regulation techniques will be performed with measurement verifications. The successful completion of this CAREER project will enable wider adoption of WPT, trigger innovations, open new trends for omnidirectional wireless powered applications, and generate broad impacts in our society. This project is jointly funded by the Communications, Circuits and Sensing Systems (CCSS) Program and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.