Foreign Object Detection Using Repelling Magnetic Fields
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless power transfer systems face challenges in detecting foreign objects, such as metal, human bodies, and animals, with high precision over a wide range, particularly in the height direction, due to limitations in magnetic field intensity and detection sensitivity when using single or multiple detecting coils.
Innovation Solution
A foreign object detecting device comprising two adjacent coils with a foreign object detecting circuit that outputs signals with specific waveforms to intensify the magnetic field between the coils, allowing for precise detection of foreign objects by measuring changes in impedance values, thereby enhancing detection range and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple detecting coils are used to increase detection range, then the detection range is improved, but the magnetic field intensity and detection sensitivity deteriorate due to field interference and distribution issues
Solution Approach 1:
The detecting coil is divided into multiple independent coil units arranged in an array. Each coil unit operates independently with its own driving signal, allowing the system to maintain high magnetic field intensity at each position while collectively covering a wide detection area. The segmentation enables parallel operation of multiple coils without mutual interference.
Solution Approach 2:
Different driving signals with distinct frequencies are applied to each coil unit in a periodic manner. This allows the system to sequentially activate different coil units or combine them with phase differences, maintaining high magnetic field intensity in the detection region while expanding the overall detection range through coordinated periodic operation.
2Area of stationary object
If the size of power transmitting coil is increased to widen charging area, then the charging area is improved, but the detection precision of foreign objects deteriorates due to reduced magnetic field concentration
Solution Approach 1:
The large power transmitting coil is segmented into multiple smaller coil units arranged in an array. Each unit maintains concentrated magnetic field for high detection precision, while the collective array provides extensive charging area. The segmentation allows independent optimization of each unit's magnetic field characteristics.
Solution Approach 2:
Multiple segmented coil units are merged into a coordinated array system where each unit contributes to both power transmission and foreign object detection. The merging maintains the benefits of individual small coils (concentrated magnetic field) while achieving the coverage area of a large coil through spatial arrangement and coordinated operation.
3Device complexity
If single detecting coil is used to maintain simple design, then device complexity is improved, but detection range and precision in height direction deteriorate
Solution Approach 1:
The single detecting coil is segmented into multiple coil units arranged vertically or in three-dimensional space. This segmentation enables detection at multiple height levels simultaneously, improving vertical detection precision while maintaining relatively simple individual unit designs that can be mass-produced.
Solution Approach 2:
The detecting coil system transitions from a two-dimensional planar configuration to a three-dimensional array arrangement. This dimensional change allows the system to detect foreign objects at various heights and positions, significantly improving detection precision in the height direction while maintaining design simplicity through modular replication of basic coil units.
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
The solution effectively increases the range and precision of foreign object detection, particularly in the height direction, while maintaining a simple and cost-effective design by intensifying the magnetic field and accurately identifying foreign objects above the coils.
Implementation Method 1
outputs a first detecting signal having a first predetermined waveform to the first terminal of the first coil and also outputs a second detecting signal having a second predetermined waveform to the third terminal of the second coil so that a magnetic field generated from the first coil and a magnetic field generated from the second coil repel each other between the first and second coils
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A foreign object detecting device includes first and second coils, the winding directions of which are the same, and a foreign object detecting circuit. The foreign object detecting circuit outputs a first detecting signal having a first predetermined waveform to a first terminal of the first coil and outputs a second detecting signal having a second predetermined waveform, which has the same polarity as the first predetermined waveform, to a third terminal of the second coil to cause magnetic fields generated from the first and second coils to repel each other. The foreign object detecting circuit measures an amount of change of the impedance value of the first or second coil which is caused by the presence of a foreign object. When the amount of change exceeds a predetermined value, the foreign object detecting circuit determines that there is a foreign object above the first or second coil.