Wireless Power FOD Using a Maxwell Bridge Balanced Coil
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Solution Overview
Problem
Existing foreign object detection (FOD) technologies in wireless power transfer systems face challenges in accurately detecting small metallic objects and living objects, especially at varying separation distances and under changing environmental conditions, leading to potential system instability and safety risks.
Innovation Solution
A method and system utilizing a balanced coil configured as a Maxwell bridge circuit with embedded optical fiber sensors and temperature sensors to detect changes in voltage and temperature, enabling reliable detection of foreign objects regardless of size or type, and employing pattern light laser-based imaging for shape analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inductance change detection method is used, then foreign objects of various sizes can be detected, but detection precision decreases for small metallic objects
Solution Approach 1:
The balanced coil is divided into multiple unit coils arranged in specific patterns (e.g., 2x2 grid, circular arrangements). Each unit coil can detect local inductance changes independently, and their combined signals provide both comprehensive coverage and enhanced sensitivity for small objects through spatial resolution.
Solution Approach 2:
The detection method transitions from single-point inductance measurement to multi-dimensional spatial mapping by arranging unit coils in two-dimensional patterns. This allows detection of small objects through their spatial signature across multiple coil elements, improving precision while maintaining versatility.
2Reliability
If balanced coil correction for temperature change is performed, then detection reliability is improved, but device complexity increases
Solution Approach 1:
The system performs self-diagnosis by monitoring its own temperature through integrated sensors and automatically compensates for temperature-induced inductance changes in the balanced coil. This self-service approach improves reliability without requiring external calibration equipment or complex manual adjustment mechanisms.
Solution Approach 2:
Temperature sensors provide continuous feedback on the thermal state of the balanced coil and transmitter coil. The controller uses this feedback to dynamically adjust detection thresholds and compensation parameters, maintaining high reliability across varying operating conditions through closed-loop control.
3Measurement precision
If optical fiber sensor is embedded in primary coil, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The optical fiber sensor is merged directly into the primary coil structure, combining the sensing function with the power transmission component. This integration achieves high detection accuracy through direct contact with the magnetic field while reducing overall system complexity by eliminating separate sensor housings and mounting mechanisms.
Solution Approach 2:
The optical fiber sensor serves multiple functions: detecting foreign objects, monitoring temperature changes, and measuring magnetic field variations. This multi-functionality improves detection accuracy across different parameters while justifying the added complexity through consolidated sensing capabilities.
4Shape
If camera-based detection is used, then object shape analysis is possible, but detection reliability decreases in low illuminance conditions
Solution Approach 1:
The patent replaces passive optical camera-based detection with an active electromagnetic sensing system using balanced coils and optical fiber sensors. This substitution enables shape and position detection through electromagnetic field interactions independent of ambient light, maintaining reliability in low illuminance conditions while providing three-dimensional spatial information.
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 provides robust and accurate detection of foreign objects, improving system reliability and safety by correcting for temperature changes and identifying object shapes, even in low illuminance conditions, thereby enhancing the stability and efficiency of wireless power transfer.
Implementation Method 1
A method of detecting foreign objects (FOs) by configuring a balanced coil as a Maxwell bridge circuit and detecting the amount of change in voltage applied across both ends of the Maxwell bridge circuit
Implementation Method 2
an FOD method and an FOD system, in which an optical fiber sensor is applied (embedded) in a primary coil
Implementation Method 3
converting light scanned from the laser light source into pattern light and scanning the pattern light, and receiving the pattern light and detecting a pattern image
Data Source
AI summary
A system for foreign object detection (FOD) in wireless power transfer is proposed. The system may include a balanced coil which is disposed between a transmitter coil and a receiver coil and which includes a Maxwell bridge circuit. The system may also include a temperature sensor configured to measure a temperature of the transmitter coil. The system may further include a processor configured to determine whether an FO is present between the transmitter coil and the receiver coil on the basis of voltage values detected at both ends of the bridge circuit. The FOD system can recognize the FO by finding a maximum resonant frequency at which a metal reacts using resonant frequency sweeping in a bridge circuit.