Foreign Object Detection in Induction Chargers via Sensor Array Sensitivity
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Solution Overview
Problem
The significant air gap between the primary and secondary coils of an electric vehicle induction charger poses a risk of accidental foreign object introduction, which can cause damage by heating and reducing magnetic field efficiency, as metallic objects are exposed to the electromagnetic field.
Innovation Solution
A sensor array adjacent to the primary coil detects foreign objects by varying sensor sensitivity based on magnetic field intensity, using a controller to scan signals and compensate for power or frequency drift, and applying a two-dimensional convolution transform to accurately locate foreign objects and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor array is used to detect foreign objects across the entire primary coil area, then foreign object detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by configuring sensors with different sensitivities based on their specific locations. Sensors in high magnetic field intensity regions (center areas) use lower sensitivity thresholds, while sensors in low magnetic field intensity regions (edge areas) use higher sensitivity thresholds. This location-specific configuration maintains uniform detection accuracy across the entire primary coil area without requiring a uniformly complex sensor array.
2Device complexity
If uniform sensor configuration is used across all sensor locations, then device complexity is reduced, but measurement precision deteriorates due to varying magnetic field intensity
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sensitivity threshold parameter for each sensor based on its location's magnetic field intensity. The controller configures each sensor's threshold according to pre-stored magnetic field intensity data for its location, allowing the system to maintain high measurement precision across varying field conditions without requiring complex hardware differences between sensors.
3Power
If the primary coil operates at high frequency to deliver required power, then power delivery efficiency is improved, but foreign object heating risk increases
Solution Approach 1:
The patent applies preliminary action by performing foreign object detection before initiating high-frequency power delivery. The controller first activates sensors to scan for foreign objects on the primary coil surface, and only after confirming no foreign objects are present does it proceed to operate the primary coil at high frequency for charging. This preventive approach enables efficient power delivery while eliminating the heating risk.
Solution Approach 2:
The patent applies feedback by continuously monitoring magnetic field changes during operation and comparing them against expected patterns. When foreign objects are detected through sensor arrays or magnetic field analysis, the system provides feedback to the controller, which then adjusts or terminates power delivery to prevent harmful heating while maintaining efficient operation under normal conditions.
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 solution effectively detects foreign objects near the primary coil, preventing damage and ensuring efficient charging by avoiding energy dissipation through heating, while maintaining high accuracy in signal sampling and location precision.
Implementation Method 1
a primary coil operating at a high frequency, creates an alternating magnetic field that couples a secondary coil
Implementation Method 2
The sensors are configured to output a sensing signal in response to magnetically coupling the high frequency alternating magnetic field strength produced by the primary coil
Implementation Method 3
Metallic foreign object lying between the primary and secondary coils will be exposed to the electromagnetic field, resulting in heating of the foreign object
Data Source
AI summary
The invention detects foreign objects FO near a primary coil 100 of an induction charger. A sensors 111 of a sensor array 110 output sensing signals in response to magnetically coupling the alternating magnetic field 103 produced by the primary coil. A controller 165 connected to each sensor 111 scans the sensing signals and determines whether there is a foreign object perturbing the magnetic field 103 near a sensor. The magnetic field has a spatial distribution that varies by location across the primary coil area. Each sensor has a magnetic field sensing sensitivity that is inversely proportional to the magnetic intensity of the magnetic field produced by the primary coil at a location of the sensor, to reduce the collective dynamic range of the signals, thereby contributing to maintaining a high accuracy in signal sampling. A reference sensor coil 155 compensates for magnetic field drift of the primary coil.