Bipolar Checkerboard Metal Object Detection Without Blind Zone Caused by Excitation Magnetic Field for Stationary EV Wireless Charging System

Metal object detection (MOD) technology provides a guarantee for the safe operation of electric vehicle (EV) wireless charging system. To solve the problem of detection blind zone caused by excitation magnetic field in the existing MOD technology, a bipolar checkerboard MOD technology is proposed. By adding an excitation source, not only the blind zone is eliminated but also it makes the EV wireless charging system and the MOD system work independently. First, the positions and causes of the blind spot caused by the excitation magnetic field of the Tx coil in the EV wireless charging system are analyzed. Second, the structure and principle of the bipolar checkerboard MOD system are analyzed. Third, a definition of the detection sensitivity of MOD is given, and the relationship between sensitivity and the size parameters of bipolar checkerboard sensing coil sets is analyzed. Moreover, the parameter optimization method of the sensing coil sets and detection circuit is analyzed. Finally, a MOD system experimental setup is built to verify its feasibility. The results show that the highest sensitivity can reach 20% for a square aluminum plate of 80 × 80 × 1 mm³ without a blind zone and the two systems can work independently with each other.