Shield: Safety Ensured High-efficient Scheduling for Magnetic MIMO Wireless Power Transfer System

Recently, the developed techniques such as magnetic resonant coupling (MRC) and multiple-input multiple-output (MIMO) transmission have significantly improved the charging efficiency and distance for wireless power transfer (WPT) systems. However, the electromagnetic radiation (EMR) safety of wireless charging is critical in practice while mostly ignored. In this work, we take the EMR safety into account in MIMO MRC-WPT systems. We propose a safety ensured high-efficient scheduling algorithm for magnetic MIMO wireless power transfer system (called Shield). Technically, we firstly devise a simple but accurate Z-axis rotational symmetrical EMR model along with a magnetic-field-line-based meshing scheme. Further, we express the EMR safety requirement in the continuous physical space with a limited number of constraints via random sampling and rule-based filtering. Finally, we build up a system prototype for Shield and conduct extensive experiments. With the given power budget and resonant frequency, the results reveal that the EMR safety requirement only influences the charging performance of an MRC-WPT system within a certain range. Furthermore, Shield can dramatically improve the payload power transfer efficiency (PTE) by up to 66.60% compared with state-of-the-art baselines while guaranteeing the EMR safety.