  High-dimensional wireless power transfer (WPT) systems have received
increasing attention for charging mobile devices. With the receivers have
higher spatial freedom, the systems are more susceptible to the metal objects
in the surroundings. However, conventional methods for metal object detection
(MOD) can't satisfy the requirements of safety and stability of new systems.
This paper proposed a metal detection method which is more suitable for
high-dimensional WPT systems. The key feature of the proposed method is
combining load impedance and input power characteristics curves to determine
whether the receiver is a metal object or a coil. And the influence of the
metal is discussed in the circuit and magnetic model. The method is
theoretically proven by the simulation calculation. And the experiments
verified that the method can accurately detect the metal objects by setting the
threshold curves.
