Foreign Object Detection in Inductive Charging via Multi-Frequency Impedance Analysis
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Solution Overview
Problem
Current inductive charging systems face challenges in accurately and reliably detecting foreign objects due to statistical fluctuations, which can lead to safety risks during charging operations.
Innovation Solution
A detection device with a signal generator, sensor device, and evaluation device that uses AC voltage with different frequencies to determine characteristic electrical variables, such as phase and amplitude information, to detect the presence of foreign objects, ensuring precise and reliable detection by analyzing changes in the electrical circuit's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If statistical fluctuation-based detection methods are used, then the detection system is simple to implement, but the measurement precision and reliability of foreign object detection deteriorate
Solution Approach 1:
The patent applies parameter changes by using multiple AC voltage frequencies to excite the detection coil and analyzing the impedance changes at different frequencies. This allows the system to distinguish between statistical fluctuations and actual foreign objects by observing consistent impedance changes across multiple frequency measurements, thereby improving detection precision while maintaining system simplicity
Solution Approach 2:
The patent implements preliminary action by performing multiple measurements at different AC voltages before making a final detection decision. The system collects impedance data at multiple frequencies, processes this information to identify patterns indicative of foreign objects, and only then makes a detection determination. This preliminary multi-parameter measurement approach enhances reliability without significantly increasing system complexity
2Reliability
If multiple measurements are performed to improve detection reliability, then the detection precision increases, but the detection time increases
Solution Approach 1:
The patent applies periodic action by performing measurements at multiple AC voltage frequencies in a systematic sequence. The system cycles through different frequencies, collects impedance data at each frequency, and processes this periodic measurement sequence to determine foreign object presence. This structured periodic measurement approach ensures reliable detection while controlling the total measurement time through efficient sequencing
Solution Approach 2:
The patent implements skipping by implementing early termination logic in the measurement process. If foreign objects are detected at earlier measurement stages or if the impedance changes clearly indicate foreign object presence, the system can skip completing all planned measurements and proceed to the detection decision, thereby reducing the actual detection time while maintaining reliability
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 enhances the safety and reliability of inductive charging systems by accurately detecting foreign objects, preventing overheating and potential fires, and allowing for quick reaction to dynamic changes during charging.
Implementation Method 1
Inductive sensors through which a time-varying current flows generate a time-varying magnetic vortex field
Implementation Method 2
the motor vehicle can be driven over a charging device, and this charging device has a primary coil, via which a coil of the charging system on the motor vehicle is supplied
Implementation Method 3
Conductive objects in a magnetic field that changes over time can heat up through induction or, if necessary, magnetic reversal
Data Source
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Figure 6b~7
AI summary
Method for detecting objects in charging arrangements (1) for charging electrically operated devices by means of a detection device (20), wherein at least one individual sensor device (43) comprising an electrical circuit comprising at least one detection coil (41) and/or at least one resistor and/or at least one capacitor is subjected to a plurality of different alternating voltages and at least one electrical quantity (ai, bi) characteristic of the individual sensor device (43) is measured in each case.According to the invention, based on a plurality of characteristic electrical quantities (ai, bi) measured for the individual sensor device (43), at least one evaluation quantity (Rsensor,0, Lsensor,0), preferably characteristic of the electrical circuit, is determined, wherein, depending on the evaluation quantity (Rsensor,0, Lsensor,0), it is determined whether there is an object in the vicinity of the individual sensor device (43) that is movable relative to this individual sensor device (43).