Sense Coil Matrix Layout for Uniform Foreign Object Detection
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Solution Overview
Problem
Existing foreign object detection systems for wireless power transfer systems suffer from non-uniform sensitivity across the surface, leading to potential undetection of objects near the edges of sense coils and increased complexity due to oversized system design to account for worst-case scenarios.
Innovation Solution
The implementation of a sense coil structure with an outer and inner coil section, where the distance between the outermost and innermost turns is at least twice the largest distance between turns in the outer region, ensuring more uniform sensitivity across the surface, along with a stimulus circuit and measurement unit for detecting foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sense coil is used for foreign object detection, then the system structure is simple, but the detection sensitivity is non-uniform across the surface with poor performance at edges
Solution Approach 1:
The sense coil is divided into multiple independent coil sections (first coil section, second coil section, third coil section, etc.) arranged in a matrix pattern. Each coil section can be independently controlled and evaluated, allowing the system to achieve uniform detection sensitivity across the entire surface by combining results from multiple segments rather than relying on a single oversized coil.
2Area of stationary object
If multiple detection cells are used to cover the surface, then the detection area increases, but the system complexity and lead requirements increase
Solution Approach 1:
Multiple coil sections are electrically connected in series within each detection cell, and detection cells are connected through a matrix of input and output leads. This merging approach allows the system to cover a large detection area while managing complexity through structured connectivity patterns, where each detection cell processes information from its constituent coil sections and combines results through the lead matrix.
Solution Approach 2:
The coil sections are arranged in a two-dimensional matrix pattern with rows and columns, creating a grid structure that efficiently covers the detection surface. This dimensional arrangement allows systematic evaluation of the entire surface area by organizing multiple detection cells in spatial relationships that optimize both coverage and complexity management.
3Measurement precision
If the sense coil turns are closely spaced to increase sensitivity, then the detection precision improves, but the coil becomes more susceptible to external magnetic field interference
Solution Approach 1:
By dividing the sense coil into multiple smaller coil sections, the system reduces the effective area of each individual coil that could pick up external magnetic field interference. The segmented structure allows closely spaced turns within each section for high precision while the distributed arrangement across multiple sections reduces overall susceptibility to external interference through spatial distribution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration provides a more uniform detection sensitivity across the surface, reducing the likelihood of undetected foreign objects and minimizing system complexity by maintaining high sensitivity both centrally and peripherally, while also reducing interference from external magnetic fields.
Implementation Method 1
Inductive sensors are more commonly used, because they are robust against environmental influences such as dirt and provide precise results in the near range at the same time. One kind of inductive sensors detects the reduction of the inductance of a coil due to induced eddy currents in the object to be detected, which counteract the primary field of the coil.
Implementation Method 2
One kind of inductive sensors detects the reduction of the inductance of a coil due to induced eddy currents in the object to be detected, which counteract the primary field of the coil.
Data Source
AI summary
A sensor arrangement for a foreign object detection device for a wireless power transfer system includes a plurality of detection cells, each including a sense coil including a winding spirally wound in a plane and having a plurality of turns. A plurality of input leads and one or more output leads are provided such that each detection cell may be connected to a current input and a current output. The input lead and the output lead of at least one sense coil is routed through a matrix-like structure to which the at least one sense coil belongs close to each other such as to reduce an area parallel to said matrix-like structure and enclosed by said input and output leads.