Electromagnetic Model-Based Foreign Object Detection for Wireless Power Transfer

Abstract

Foreign objects near wireless power transfer (WPT) systems are fire hazards that must be detected. In this paper, a new accurate method is presented for foreign object detection based on an electromagnetic model for WPT. Foreign objects are detected by quantifying the deviation from a normal model. This deviation is caused by the foreign object's additional electromagnetic coupling. Advantages of this new method include invariance to receiver coil misalignment, and power level, allowing low-power detection prior to startup. Electromagnetic modelbased foreign object detection (EM-FOD) was demonstrated in hardware to detect a 2 cm diameter U.S. nickel coin, a small disposable lighter, and a saline proxy for a living animal in a kilowatt-level wireless power transfer system, using a pre-startup power of only 7 W. Furthermore, foreign objects can be detected regardless of an Rx coil misalignment of up to 10 cm. This paper is accompanied by an instructional video.

Numerical and Experimental Investigation of Time-Domain-Reflectometry-Based Sensors for Foreign Object Detection in Wireless Power Transfer Systems

“…The parameters R and L are derived from a magnetic simulation in the frequency domain according to Figure 4b following Equation (5), where H is the magnetic field strength, B the magnetic flux density, A the magnetic vector potential and J the current density, to which J e contributes as external current density. The external current density is set by a 1 A external current flowing through the cross section of the right conductor.…”

“…System-parameter-based FOD monitors the effect of foreign objects on the electrical, thermal or mechanical parameters of the WPTS. Electrical parameters are usually current [5,6], power loss or efficiency [7], quality factor [8], coil inductance, frequency or phase [9]. Non-electrical parameters are, for example, temperature [10,11], weight or pressure.…”

Analysis and Visualization of the Instantaneous Spatial Energy Density and Poynting Vector of the Wireless Power Transfer System

“…To solve and explain this question in the near field, the WPT system should be analyzed from the electromagnetic views. Many studies [12][13][14][15] have calculated the magnetic field of a WPT system. The magnetic field of a WPT system is important when one analyzes the magnetic field or designs of the coil system.…”