Abstract
Wireless power transfer technology is being widely used in electric vehicle wireless-charging applications, and foreign object detection (FOD) is an important module that is needed to satisfy the transmission and safety requirements. FOD mostly includes two key parts: metal object detection (MOD) and living object detection (LOD), which should be implemented during the charging process. In this paper, equivalent circuit models of a metal object and a living object are proposed, and the FOD methods are reviewed and analyzed within a unified framework based on the proposed FOD models. A comparison of these detection methods and future challenges is also discussed. Based on these analyses, detection methods that employ an additional circuit for detection are recommended for FOD in electric vehicle wireless-charging applications.
Highlights
Electric vehicles (EV) are expected to be a promising alternative to vehicles powered by fossil fuels and to reduce emissions from the transportation sector
foreign object detection (FOD) methods can be divided into metal object detection (MOD) and living object detection (LOD) methods according to type of foreign object
The influence of the metal object location on the self-inductance, mutual inductance and resonance frequency of the wireless power transfer (WPT) system was researched in [56,82], where the variation increased as the metal object became closer to the coil, and the maximum variation always occurred on the coil but not on the exact center because the flux density in the center may cancel it out. All these results show that the impact of a metal object in a WPT system is extremely sensitive to the characteristics of the metal object
Summary
Electric vehicles (EV) are expected to be a promising alternative to vehicles powered by fossil fuels and to reduce emissions from the transportation sector. On the other hand, living objects such as cats, dogs or humans may move or even remain close to the transmitting coil of the WPT system, which may cause serious safety problems The corresponding standards, such as SAE J2954, require sensors to protect against hazardous FOD conditions. Based on the proposed models, the FOD methods are reviewed and analyzed within a unified framework The characteristics of these methods are comparatively studied with respect to cost, space, sensitivity and complexity, and suitable detection methods are introduced in this paper. The structure of this paper is as follows: in Section 2, a typical WPT system is introduced, and general circuit models of a metal object and a living object in a WPT system are proposed for the analysis and review of FOD methods.
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