Electromagnetic Model-Based Foreign Object Detection for Wireless Power Transfer

Foreign objects near wireless power transfer (WPT) systems are fire hazards that must be detected. In this article, a new accurate method is presented for foreign object detection based on an electromagnetic model for WPT. Foreign objects are detected by quantifying the deviation from a normal model. This deviation is caused by the foreign object's additional electromagnetic coupling. Advantages of this new method include invariance to receiver coil misalignment, and power level, allowing low-power detection prior to startup. Electromagnetic model-based foreign object detection was demonstrated in hardware to detect a 2 cm diameter U.S. nickel coin, a small disposable lighter, and a saline proxy for a living animal in a kilowatt-level wireless power transfer system, using a prestartup power of only 7 W. Furthermore, foreign objects can be detected regardless of an Rx coil misalignment of up to 10 cm. This article is accompanied by an instructional video.