US Patent 11904712 Foreign object detection for wireless power transfer systems

Foreign objects impinging on a ground transceiver assembly (GTA) of a wireless power transfer (WPT) station are detected using a two-stage foreign object detection system. In a first stage, at least one camera is positioned to observe a charging position of the GTA and an area surrounding the charging position. In a second stage, an impedance measurement circuit measures an impedance of a wireless power transfer coil of the GTA. An imaging processor analyzes images from the at least one camera to identify changes or features indicative of introduction of a foreign object onto an exposed surface of the GTA or in the area surrounding the charging position. A foreign object detection (FOD) controller triggers an impedance inspection of the GTA by the impedance measurement circuit and initiates a failsafe operation when movement of an object crossing into or over the charging position is detected.