Evaluation Modeling and Improvement Method for Sensitivity of Metal Object Detection in EV Wireless Charging System

Metal object detection (MOD) technology can effectively improve the safety of wireless charging systems for electric vehicles. To solve the problem of disunity in sensitivity evaluation methods and the lack of parameters design rules in the research field of MOD technology, a sensitivity evaluation model for MOD systems based on sensing coils is constructed and three system parameters design rules are proposed based on this model. First, a sensitivity evaluation factor is defined and different types of detection blind spot generation mechanisms are distinguished. Second, three parameters design rules are obtained: parameters design rules for high sensitivity, parameters design rules for low detection voltage errors, and parameters design rules for reducing Rx coil impact. Third, the parameters design rules are verified and modified by electromagnetic field simulation. Three engineering parameters design rules for the bipolar checkerboard MOD system are obtained. Finally, a bipolar checkerboard MOD system is built to test different materials and sizes of metal objects (MOs). The eddy current dividing MOs capability and the advantage of high sensitivity of the bipolar checkerboard MOD system are verified.