Dual-Mode Foreign Object Detection System for Metal and Live Object Detection in Wireless Electric Vehicle Charger

Accurate detection of metal objects (MO) and live objects (LO) is essential to ensure the safe operation of wireless electric vehicle chargers. This letter proposes a dual-mode foreign object detection (FOD) system. The system utilizes the time division multiplexing mode to detect foreign objects and the frequency sweeping resonance mode to distinguish between MOs and LOs. First, a bipolar overlapping FOD coil is introduced and the effects of MOs and LOs on the coil impedance are analyzed. Subsequently, details regarding the design, operational principles, and detection criteria of the proposed dual-mode FOD system are provided. Finally, the proposed methods are verified with experimental results. The results indicate that a 30 mm diameter aluminum sheet causes a 0.06 V reduction in sampling voltage and a 20 kHz increase in resonance frequency, while a human finger induces a 0.18 V reduction in sampling voltage and a 180 kHz decrease in resonance frequency. These findings confirm the feasibility and effectiveness of the proposed system and its detection criteria.