Foreign-Object Detection Using Opposite-Phase Coils
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Solution Overview
Problem
Existing foreign-object detecting devices in wireless electric-power transmission systems face challenges in accurately detecting objects between adjacent coils and in increasing the detection range, leading to potential heat generation and safety concerns.
Innovation Solution
A foreign-object detecting device is designed with adjacent coils having the same winding direction, where detection signals with inverted polarities flow in opposite directions to generate a combined magnetic field, allowing for impedance changes to be measured to determine the presence of foreign objects between coils, thereby enhancing detection accuracy and range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If coils are arranged adjacently to increase detection area, then detection range increases, but detection accuracy between coils deteriorates
Solution Approach 1:
The detection system is divided into multiple independent detection coils arranged adjacently, with each coil responsible for detecting foreign objects in its specific region. This segmentation allows the system to cover a larger area while maintaining detection accuracy through coordinated operation of individual coils.
Solution Approach 2:
The patent applies opposite-phase currents to adjacent coils, creating magnetic fields that cancel each other out in the region between coils when no foreign object is present. When a foreign object is detected, it disrupts this cancellation, producing a measurable signal. This inverted approach solves the problem of detecting objects between coils by using magnetic field interference rather than direct detection.
2Measurement precision
If detection sensitivity is increased to detect small foreign objects, then detection accuracy improves, but false detection increases
Solution Approach 1:
The system continuously monitors impedance changes in real-time and compares them against predetermined thresholds. When the impedance change exceeds the threshold, the system determines the presence of a foreign object. This feedback mechanism allows the system to maintain high detection sensitivity while reducing false detections by objectively comparing measurements against established criteria.
Solution Approach 2:
By using opposite-phase currents that create magnetic field cancellation between coils, the system establishes a baseline state with minimal interference. Foreign objects disrupt this cancellation, creating detectable signals. This approach improves reliability by providing a clear distinction between normal operating conditions and foreign object presence, reducing false detections.
3Area of stationary object
If multiple detection coils are added to cover larger area, then detection range increases, but device complexity increases
Solution Approach 1:
Multiple detection coils are arranged adjacently and operated simultaneously with coordinated current phases. The coils are merged into a unified detection system where each coil contributes to the overall detection coverage. This combining approach increases the detection area while managing complexity through standardized coil designs and systematic current control.
Solution Approach 2:
The patent uses opposite-phase current arrangement in adjacent coils, creating a systematic pattern that simplifies the control of multiple coils. By establishing a regular alternating phase pattern, the system manages the complexity of multiple coils through a predictable and repeatable configuration, making the extended detection array easier to control.
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 effectively increases the detection range and accuracy for foreign objects between adjacent coils, preventing heat generation and ensuring safety by reliably detecting objects that previous systems struggled with, while minimizing component count and manufacturing costs.
Implementation Method 1
using electromagnetic induction between an electric-power transmission coil in a wireless electric-power transmitting device (also referred to as an "electric-power transmitting device") and an electric-power reception coil in a wireless electric-power receiving device
Implementation Method 2
measuring an amount of change in an impedance value of one of the first coil and the second coil, the change corresponding to a change in the combined magnetic field
Data Source
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AI summary
A foreign-object detecting device includes a first coil, a second coil arranged adjacent to the first coil and having the same winding direction as that of the first coil, and foreign-object detecting circuitry. The foreign-object detecting circuitry outputs a first detection signal to an outside or inside terminal of the first coil, outputs a second detection signal having an inverted phase to an outside or inside terminal of the second coil, causes one of the first and second detection signal to flow clockwise, causes the other detection signal to flow counterclockwise to generate a combined magnetic field across a center of the first and a center of the second coil, measures an amount of change in an impedance value of the first or second coils, and determines that a foreign object is present within the combined magnetic field, based on the amount of change.