Foreign Object Detection in Wireless Power Transfer Systems
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Solution Overview
Problem
Wireless power transfer systems face challenges in detecting and mitigating the presence of foreign object debris (FOD), which can interact with magnetic fields, potentially causing heating or safety hazards, and existing methods are inadequate for reliably detecting all types of FOD, including living objects.
Innovation Solution
The system employs a plurality of detectors with loops of conducting material and control electronics to measure electrical signals related to magnetic fields and capacitance, comparing these measurements to baseline data to determine the presence of FOD or living objects, using a combination of passive and active mitigation techniques to prevent interactions with the wireless power transfer system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single type of detector is used to detect FOD, then the device complexity is reduced, but the measurement precision and reliability of detecting all types of FOD (including living objects) deteriorates
Solution Approach 1:
The detection system is segmented into multiple specialized detectors: a first detector with conductive loops for detecting metallic FOD through magnetic field changes, and a second detector with capacitive elements for detecting living objects through capacitance changes. Each detector type is optimized for specific FOD categories, improving overall detection precision without requiring a single complex universal detector.
Solution Approach 2:
The wireless power transfer system integrates multiple detection functions into a unified control system. The controller simultaneously processes signals from both magnetic field detectors and capacitive detectors, enabling the system to detect multiple types of FOD (metallic and non-metallic/living objects) using a single integrated control architecture, thereby maintaining ease of operation while improving detection comprehensiveness.
2Reliability
If multiple detectors with different configurations are used to improve detection coverage, then the measurement precision and reliability improve, but the device complexity increases
Solution Approach 1:
The detector array is segmented into functionally distinct groups: detectors with conductive loops for magnetic field sensing and detectors with capacitive elements for electric field sensing. This segmentation allows each detector type to be optimized for specific detection purposes while maintaining manageable system complexity through clear functional separation.
Solution Approach 2:
Multiple detectors are combined into a coordinated array under unified control. The controllers integrate signals from various detectors, combining their individual detection capabilities to achieve comprehensive FOD detection coverage. This merging approach improves reliability by cross-validating detections across multiple sensors while managing complexity through centralized control architecture.
3Measurement precision
If detectors with more loops are used to increase sensitivity in low magnetic flux regions, then the measurement precision improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Detectors with different numbers of conductive loops are strategically placed in different spatial regions based on local magnetic flux characteristics. Regions with higher magnetic flux use detectors with fewer loops, while regions with lower magnetic flux use detectors with more loops to achieve the required sensitivity. This local optimization improves overall detection precision while managing manufacturing complexity by applying different configurations only where necessary.
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 approach effectively detects and mitigates FOD, ensuring safe operation of wireless power transfer systems by accurately identifying and responding to various types of debris and living objects, reducing the risk of heating or safety hazards.
Implementation Method 1
a first detector featuring one or more loops of conductive material, where the first detector is configured to generate an electrical signal based on a magnetic field between the power source and the power receiver
Implementation Method 2
measure an electrical signal of the second detector, where the electrical signal of the second detector is related to a capacitance of the second detector
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
Systems and methods for detecting foreign object debris around a wireless power transfer system include a plurality of detectors, each detector featuring one or more loops of conducting material, and a controller configured to measure at least one of a voltage and a current in each detector and to determine, based on the measurements, whether foreign object debris is present around the wireless power transfer system, where at least some of the plurality of detectors include a first number of loops of the conducting material, and at least some of the plurality of detectors include a second number of loops of the conducting material larger than the first number.