Foreign matter detection system and method for wireless charging system of electric vehicle

Abstract

The invention provides a foreign matter detection system and method for an electric vehicle wireless charging system, and belongs to the technical field of electric vehicle wireless charging, and the foreign matter detection system comprises a double-comb-shaped self-resonance detection coil module, a high-frequency signal excitation module, a signal processing and detection module and a main control and discrimination module. The foreign matter detection method comprises the following steps: S1, calibrating initial parameters of a system and establishing a reference; and S2, real-time monitoring and foreign matter discrimination. According to the invention, the double-comb-shaped self-resonance detection coil module is designed, so that the adverse effect of an eddy current effect on a detection system is effectively eliminated in principle, noise in a detection signal is remarkably reduced, complete decoupling with a power magnetic field is realized, mutual independence of foreign matter detection and wireless energy transmission is ensured, a detection blind area is avoided, and the detection accuracy is improved. And a detection method based on orthogonal demodulation is introduced, so that the detection accuracy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a foreign matter detection system and method for a wireless charging system of an electric vehicle, and belongs to the technical field of wireless charging of an electric vehicle. BACKGROUND

[0002] During the operation of the wireless charging system of an electric vehicle, metal foreign matters or living organisms may intrude into the charging area. The metal foreign matters will generate eddy current heating under the alternating magnetic field, causing safety hazards; and the intrusion of living organisms may pose a risk of electromagnetic radiation. Therefore, effective foreign matter detection is the key to ensuring the safety of the system.

[0003] At present, the foreign matter detection methods for a wireless charging system can be divided into three categories: detection based on system electrical parameters, detection based on waves, and detection based on auxiliary coils. Among them, the method based on auxiliary coils has become the mainstream scheme in engineering applications due to its simple structure, low cost, and high detection sensitivity. However, the existing detection coil design still has some inherent defects: (1) insufficient electromagnetic decoupling: the traditional inductive detection coil is prone to magnetic coupling with the power transmission coil, which is disturbed by the strong power magnetic field, resulting in low signal-to-noise ratio of the detection signal. (2) Existence of detection blind area: due to the uneven magnetic field distribution of the traditional coil, the magnetic field strength in some areas is extremely weak, and when the foreign matter is located in these areas, the system parameter change caused is extremely small, resulting in ineffective detection and forming a detection blind area. (3) Weak integrated detection capability: it is difficult to use one coil structure to simultaneously detect metal foreign matters and living foreign matters with high sensitivity. SUMMARY

[0004] To solve the problems of insufficient electromagnetic decoupling, weak integrated detection capability, and existence of detection blind area in the detection coil of the existing foreign matter detection of a wireless charging system, and to further improve the efficiency of foreign matter detection, the present application proposes a foreign matter detection system and method for a wireless charging system of an electric vehicle.

[0005] The technical solution adopted by the present application to solve the above problems is as follows: the present application proposes a foreign matter detection system for a wireless charging system of an electric vehicle, which comprises: a double-comb self-resonant detection coil module, which comprises a top-layer comb coil 1, a PCB dielectric substrate 2, and a bottom-layer comb coil 3, the top-layer comb coil 1 being fixed on the upper surface of the PCB dielectric substrate 2 by printing process, and the bottom-layer comb coil 3 being fixed on the lower surface of the PCB dielectric substrate 2 by printing process; a high-frequency signal excitation module for generating a sinusoidal signal with adjustable frequency, adjustable amplitude, and controllable phase, which is connected to the signal excitation end of the double-comb self-resonant detection coil module; The signal processing and detection module uses an orthogonal demodulation circuit to mix the high-frequency signal returned by the dual-comb self-resonant detection coil module with the original excitation signal and its 90-degree phase-shifted signal to generate two baseband signal components. The mixed signal is then filtered by a low-pass filter to remove the high-frequency components, resulting in orthogonal DC signals I and Q. The main control and discrimination module includes an FPGA, which controls the high-frequency signal excitation module to perform frequency scanning, acquires the I and Q signals demodulated from the signal processing and detection module, and executes logic based on the transmission line distributed parameter model of the dual-comb self-resonant detection coil module. The transmission line distributed parameter model includes the equivalent series transmission line resistance. R s Equivalent series transmission line inductance L s Equivalent parallel transmission line resistance R p1 Equivalent parallel transmission line inductance L p1 Equivalent parallel coupled inductor L p2 Equivalent parallel coupling capacitor C p1 and ground capacitance C p2 .

[0006] Furthermore, the top comb-shaped coil 1 is fixed to the upper surface of the PCB dielectric substrate 2 through a printing process, forming a first comb-shaped electrode layer, which includes multiple planar comb teeth; the bottom comb-shaped coil 3 is fixed to the lower surface of the PCB dielectric substrate 2 through a printing process, forming a second comb-shaped electrode layer, which includes multiple planar comb teeth; the first and second comb-shaped electrode layers are arranged in a mirror symmetrical manner; one end of either the first or second comb-shaped electrode layer serves as a signal excitation end for receiving a high-frequency excitation signal, and the other end serves as a signal detection end for outputting an inductive signal; the dual-comb self-resonant detection coil module, as a distributed parameter network, has self-resonant characteristics, and the input impedance of the dual-comb self-resonant detection coil module exhibits series resonance or parallel resonance at a specific frequency.

[0007] Furthermore, in the signal processing and detection module, the I-channel signal is in phase with the original excitation signal, reflecting the in-phase component of the output signal of the dual-comb self-resonant detection coil module; the Q-channel signal is 90 degrees out of phase with the original excitation signal, reflecting the quadrature component of the output signal of the dual-comb self-resonant detection coil module.

[0008] Furthermore, the high-frequency signal excitation module includes a DDS module and a 3PD5651E analog-to-digital converter. The DDS module is a signal synthesis generator that uses high-precision direct digital frequency synthesis. The 3PD5651E analog-to-digital converter is used to generate sine wave signals with adjustable frequency, adjustable amplitude, and controllable phase.

[0009] Furthermore, the foreign object detection system is connected to a wireless charging module, which is used to transmit wireless power to the electric vehicle wireless charging system and receive instructions from the foreign object detection system to limit the power.

[0010] Furthermore, the equivalent series transmission line resistance R s and equivalent series transmission line inductance L s Series connection, and positioned along the transmission line path; equivalent parallel transmission line resistance. R p1 Equivalent parallel transmission line inductance L p1 Equivalent parallel coupled inductor L p2 Equivalent parallel coupling capacitor C p1 and ground capacitance C p2 Parallel connection, and all connected in parallel with the transmission line, capacitance to ground C p2 One end is coupled to the equivalent parallel inductor L p2 Equivalent parallel coupling capacitor C p1 Connect one end to the ground.

[0011] A foreign object detection method for a wireless charging system for electric vehicles includes: Step 1: The main control and discrimination module controls the DDS module to perform a full bandwidth frequency sweep from 0MHz to 25MHz with a step value of 50kHz. After the output stabilizes at each frequency point, the foreign object detection system maintains a fixed delay and performs a mixing operation through the signal processing and detection module to demodulate the quadrature DC signals of the I and Q outputs. Step 2: Simultaneously demodulate the orthogonal DC signals I and Q output by the signal processing and detection module, fully acquire the phase and amplitude information of the dual comb self-resonant detection coil module, store the voltage values ​​of I and Q in the buffer area, and obtain a complete frequency response curve containing multiple series and parallel resonant points. Step 3: In the execution logic of the main control and discrimination module, compare the amplitude curves and phase curves of the orthogonal DC signals of the I and Q paths to obtain local peak points and phase change points, identify candidate resonant frequency ranges, and mark all of them as candidate resonant points if multiple resonant points exist. Step 4: For the candidate resonant point, the foreign object detection system performs a secondary fine scan. During the secondary fine scan, the scan width is reduced to 1MHz and the step size is reduced to 10kHz. Compensation frequency points are inserted on both sides of the center frequency point of the amplitude and phase curves of the quadrature DC signals of the I and Q channels. The reference resonant frequency is accurately locked by the zero-crossing detection method of the Q channel. f_ref And simultaneously save the corresponding I / Q channel output signals; Step 5: Repeat step 3 to obtain candidate resonant points in the secondary fine scanning process, and collect multiple sets of data near the candidate resonant points in the secondary fine scanning process. Statistically analyze frequency jitter, noise distribution, and the system's own frequency stability based on the collected data, and automatically set the first threshold T1 and the second threshold T2 based on the statistical results. Step 6: Repeat steps 1-5 to perform the frequency sweep operation cyclically, and acquire the resonant frequency of the foreign object detection system in real time during each frequency sweep cycle. f_detect And obtain the detection frequency difference Δ f Based on the detection frequency difference Δ f The foreign object detection results are obtained using the first threshold T1 and the second threshold T2.

[0012] Furthermore, step 6 specifically includes: Based on the resonant frequency of the real-time foreign object detection system f_detect and reference resonant frequency f_ref The detection frequency difference Δ is obtained by combining the adaptive moving average filtering algorithm. f ; If the detection frequency difference is |Δ f If |≤ the first threshold T1, it indicates that the resonance point is stable, the system determines that there is no foreign object intrusion, the foreign object detection system enters the low power mode, only maintains the minimum monitoring function, and reduces energy consumption. If the first threshold T1 ≤ detection frequency difference |Δ f If |Δ| < the second threshold T2, the foreign object detection system marks it as a suspected metallic foreign object and repeats the detection for 3-5 frequency sweep cycles. If each repeated frequency sweep cycle has a value of |Δ| < the first threshold T1 ≤ |Δ|, the detection system will determine the result. f If |≤ the second threshold T2, it is confirmed as a metal foreign object intrusion. The foreign object detection system triggers the corresponding alarm level and sends a power limit command to the wireless charging module. If the detection frequency difference is |Δ f |>At the second threshold T2, the foreign object detection system marks it as a living foreign object, immediately triggers the highest level alarm, and forces the wireless charging module to limit its power.

[0013] Furthermore, before the foreign object detection system makes a judgment, it introduces a millisecond-level jitter reduction delay and compares it with the judgment result of the previous frequency sweep cycle. When a metal foreign object intrusion is identified, if the detection frequency difference |Δ f If a slight shift occurs in the detected position within the dual-comb self-resonant detection coil module, the foreign object detection system will trigger a low-level alarm. If a significant shift occurs in the detected position, a high-level alarm will be triggered.

[0014] The beneficial effects of this invention are: 1. This invention effectively eliminates the adverse effects of eddy currents on the detection system by designing a non-closed detection coil structure, thereby significantly reducing noise in the detection signal. In addition, this invention adopts a double-layer comb-shaped coil configuration, which achieves complete decoupling from the power magnetic field, ensuring the independence of foreign object detection and wireless power transmission, and avoiding interference during the detection process.

[0015] 2. This invention introduces a detection method based on orthogonal demodulation, which can accurately measure the parameter changes of the system under conditions of presence or absence of foreign objects. This not only improves the accuracy of the detection results but also effectively enhances the stability of the detection results, realizing the integrated and differentiated design of the detection function.

[0016] 3. The double comb-shaped self-resonant detection coil used in this invention has self-resonant characteristics. Its input impedance can exhibit series resonance or parallel resonance at a specific frequency, thereby achieving high-sensitivity detection. This allows the foreign object detection system to quickly adjust the detection parameters and relock the resonance point when the detection coil is affected by external foreign objects or temperature drift, adapting to dynamically changing loads or environmental interference.

[0017] 4. By setting dynamic thresholds, this invention allows the system to be flexibly adjusted according to application scenarios to adapt to different detection needs, such as situations sensitive to metals or safe for biological organisms. Simultaneously, by introducing measures such as de-jitter delay, multi-level discrimination logic, and spatial parameter deviation analysis, the reliability and robustness of the system are improved, and the possibility of false alarms is reduced. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of a foreign object detection system for a wireless charging system for electric vehicles. Figure 2 This is a schematic diagram of the structure of a dual-comb self-resonant detection coil module. Figure 2 In the diagram, 1-top layer comb coil, 2-PCB dielectric substrate, 3-bottom layer comb coil; Figure 3 A schematic diagram of the complete distributed parameter model of a transmission line; Figure 4 This is a schematic diagram of the structure of the transmission line distributed parameter model used in this invention; Figure 5 A schematic diagram of the distributed parameter model of a transmission line after the introduction of different types of foreign objects; Figure 6 This is a flowchart illustrating a foreign object detection method for a wireless charging system for electric vehicles. Detailed Implementation

[0019] Specific implementation method one: Combining Figures 1-5 This implementation method is described as follows: Figure 1 As shown, the structure of a foreign object detection system for a wireless charging system for electric vehicles according to this embodiment includes: The system includes a dual-comb self-resonant detection coil module, a high-frequency signal excitation module, a signal processing and detection module, and a main control and discrimination module.

[0020] The foreign object detection system constructed in this embodiment uses electric field coupling instead of traditional magnetic field coupling as the detection mechanism. It uses a non-closed, open double-layer comb-shaped electrode structure to excite and sense the electric field, thereby avoiding magnetic coupling interference and eliminating blind spots by utilizing its uniformly distributed electric field.

[0021] like Figure 2 As shown, the dual-comb self-resonant detection coil module includes a PCB substrate 2. A top-layer comb coil 1 is fixed to the upper surface of the PCB substrate 2 using a printing process to form a first comb electrode layer, which consists of multiple parallel comb teeth. A bottom-layer comb coil 3 is fixed to the lower surface of the PCB substrate 2 using a printing process to form a second comb electrode layer. The second comb electrode layer is mirror-symmetrical to the first comb electrode layer and also includes multiple parallel comb teeth. There is no direct electrical connection between the first and second comb electrode layers; the signal is coupled and transmitted through the capacitance and inductance parameters distributed between the layers. In the dual-comb self-resonant detection coil module, one end of one of the comb electrode layers serves as the signal excitation end, used to receive a high-frequency excitation signal, and the other end serves as the signal detection end, used to output an inductive signal. As a distributed parameter network, the dual-comb self-resonant detection coil module has self-resonant characteristics; its input impedance can exhibit series resonance or parallel resonance at a specific frequency, thereby achieving high-sensitivity detection.

[0022] The dual-comb non-closed self-resonant coil module is manufactured using PCB technology. The substrate is FR4 with a dielectric constant of approximately 4.4 and a thickness of 1.6 mm. The detection coil is 390 mm long, 190 mm wide, with a line width of 1 mil, a comb length of 185 mm, and a comb spacing of 15 mm. These parameters were optimized through ANSYS HFSS simulation, revealing a resonant point suitable for wireless charging systems within a frequency band below 25 MHz.

[0023] This invention effectively eliminates the adverse effects of eddy currents on the detection system by designing a non-closed detection coil structure, thereby significantly reducing noise in the detection signal. In addition, this invention adopts a double-layer comb-shaped coil configuration, which achieves complete decoupling from the power magnetic field, ensuring the independence of foreign object detection and wireless power transmission, and avoiding interference during the detection process.

[0024] The signal processing and detection module employs a quadrature demodulation circuit, including a positive-inverting negative feedback amplifier, an AD835 multiplier, a 3PA1030 analog-to-digital converter, and a UAF42 low-pass filter. This circuit mixes the high-frequency signal returned from the detection coil with the original excitation signal and its 90-degree phase-shifted signal, generating two baseband signal components. The mixed signal is then filtered by the low-pass filter to remove the high-frequency components, retaining only the low-frequency DC components, ultimately yielding quadrature DC signals I and Q. The I signal is in phase with the original excitation signal, reflecting the in-phase component of the detection coil's output signal; the Q signal is 90 degrees out of phase with the excitation signal, reflecting the quadrature component of the detection coil's output signal. By simultaneously acquiring and analyzing the I and Q signals, the phase and amplitude information of the detection coil can be fully obtained, enabling high-precision tracking of the coil's resonant state. Furthermore, this module design allows for real-time monitoring of dynamically changing loads or environmental interference. Since the I and Q signals can fully characterize the complex impedance change of the detection coil, the system can quickly adjust the detection parameters and relock the resonant point when the detection coil is affected by external foreign objects or temperature drift.

[0025] The high-frequency excitation module uses a high-precision direct digital frequency synthesizer (DDS) to generate a sine wave with adjustable frequency, adjustable amplitude, and controllable phase using a 3PD5651E analog-to-digital converter.

[0026] The execution logic of the main control and discrimination module is based on the transmission line distributed parameter model of the detection coil. When metallic or living foreign objects approach the detection system, the system parameters will change. The complete transmission line distributed parameter model is as follows: Figure 3 As shown. Its characteristic impedance Z 0 and propagation constant gamma By distributed resistors R TS Transmission line inductance L TS Interlayer capacitance C M Interlayer inductance L M capacitance to ground C G Top-level inter-electrode inductor L TP Bottom-level inter-electrode inductance L BP Top layer inter-electrode capacitanceC TP and bottom inter-electrode capacitance C BP Jointly decided. This invention adopts a simplified model, namely, as follows: Figure 4 In the distributed parameter model of the transmission line shown, R s is the equivalent series transmission line resistance. L s is the equivalent series transmission line inductance. R p1 For the equivalent parallel transmission line resistance, L p1 For equivalent parallel transmission line inductance, L p2 For equivalent parallel coupled inductance, C p1 For equivalent parallel coupling capacitors, C p2 Capacitance to ground. Equivalent series transmission line resistance. R s and equivalent series transmission line inductance L s Series connection, and positioned along the transmission line path; equivalent parallel transmission line resistance. R p1 Equivalent parallel transmission line inductance L p1 Equivalent parallel coupled inductor L p2 Equivalent parallel coupling capacitor C p1 and ground capacitance C p2 Parallel connection, and all connected in parallel with the transmission line, capacitance to ground C p2 One end is coupled to the equivalent parallel inductor L p2 Equivalent parallel coupling capacitor C p1 Connect one end to the ground.

[0027] Depend on Figure 4 It can be seen that the characteristic impedance of the double comb-shaped detection coil under specific excitation conditions is... Z 0. Propagation constant gamma and system phase constant As shown in formulas (1), (2) and (3): (1); (2); (3); In formulas (1)-(3), The imaginary unit, ω is the angular frequency.

[0028] Distributed parameter models of transmission lines after the introduction of different types of foreign objects, such as Figure 5 As shown, when a metallic foreign object approaches the detection coil, it couples with the coil's electric field, generating an electrostatic effect and forming an induced charge layer on its surface with a polarity opposite to that of the electrode charge. This phenomenon is equivalent to placing a capacitor plate closely next to the electrode, thus forming an additional parallel capacitance between the metallic foreign object and the electrode. Therefore, the characteristic impedance, propagation constant, and phase constant of the foreign object detection system decrease. Consequently, the resonant frequency of the foreign object detection system decreases.

[0029] When a living foreign object approaches the detection coil, a dielectric polarization effect occurs. This polarization effect is not only equivalent to a parallel capacitor next to the electrode, but also forms a bound charge layer on the surface of the living object, thus significantly increasing the dielectric constant of the medium transported between the electrodes. Therefore, the interlayer capacitance, inter-electrode capacitance, and capacitance to ground all increase. The changes in system characteristic parameters, propagation constant, and phase constant are the same as described above, but the degree of change is greater than when a metallic foreign object is present.

[0030] Specific Implementation Method Two: The main control module uses an FPGA to control a DDS to perform frequency scanning and acquire the demodulated I and Q signals. The initial series and parallel resonant frequencies are determined by finding the extreme points of the I-path. The system resonant frequency is accurately determined by precisely finding the zero-crossing points of the Q-path. In actual experiments, the frequency scanning range is 0~25MHz, and the scanning step size is 100kHz. The output sine wave amplitude is 2.5V, with no DC bias. The following is a flowchart of a foreign object detection method for a wireless charging system for electric vehicles, illustrating the operation of this system. Figure 6 As shown.

[0031] S1: System initial parameter calibration and benchmark establishment; S101: Preliminary Full-Band Scan: The FPGA controls the DDC module to perform a full-bandwidth frequency scan from 0MHz to 25MHz, with a step value set to 50kHz. After the output at each frequency point stabilizes, the system maintains a certain delay, and then the I and Q channel voltage values ​​are acquired through the ADC module and stored in the buffer. This process yields a complete frequency response curve, including multiple series and parallel resonant points.

[0032] S102: Coarse Resonance Point Localization: Within the FPGA's internal processing logic, the amplitude and phase curves of the I / Q signals are compared to identify local peaks and phase abrupt change points. This method can initially identify candidate resonant frequency ranges. If multiple resonant points exist, all are marked as candidate points for further confirmation.

[0033] S103: Local Fine Scan: For candidate resonant points, the system automatically performs a secondary fine scan. The scan width in this stage is reduced to 1MHz, and the step size is reduced to 10kHz. To compensate for nonlinearities caused by device frequency response or temperature drift, additional compensation frequency points can be inserted on both sides of the center frequency. The reference resonant frequency can be precisely locked using the Q-channel zero-crossing detection method. f_ref And simultaneously save the corresponding I / Q channel output signals.

[0034] S105: Setting Dynamic Thresholds: Near the resonant point, the system continues to collect multiple sets of data to statistically analyze frequency jitter, noise distribution, and the system's own frequency stability. Based on the statistical results, a first threshold T1 and a second threshold T2 are automatically set. The thresholds depend not only on the system noise level but can also be flexibly adjusted according to the application scenario. In situations requiring metal sensitivity, T1 can be reduced; while in scenarios involving biological safety, T2 should be increased to ensure rapid response to living foreign objects.

[0035] This invention allows the system to be flexibly adjusted according to application scenarios by setting dynamic thresholds, adapting to different detection needs, such as those sensitive to metals or those safe for biological organisms. Simultaneously, by introducing measures such as de-jitter delay, multi-level discrimination logic, and spatial parameter deviation analysis, the system's reliability and robustness are improved, reducing the possibility of false alarms.

[0036] S2: Real-time monitoring and foreign object detection; S201: Characteristic Parameter Acquisition: The system performs a frequency sweep operation cyclically to detect the system's resonant frequency in real time. Therefore, the detected frequency difference is shown in formula (4). f_detect This is the resonant frequency detected by the system in real time. f_ref This is the reference resonant frequency.

[0037] (4); In Δ f In the calculation process, this implementation method introduces an adaptive moving average filtering algorithm to flexibly change the weight parameters in the algorithm according to the data fluctuation.

[0038] S202: Multi-level discrimination logic: If |Δ f If |≤T1, it indicates that the resonant point is stable, and the system determines that there is no foreign object intrusion. At this time, the system can enter a low-power mode, maintaining only minimal monitoring functions to reduce energy consumption.

[0039] If T1 <|Δ fIf |T2 ≤ T2, the system flags it as a suspected metallic foreign object. Considering that dust, stray electromagnetic interference, or instantaneous temperature fluctuations may cause spurious frequency shifts, the system employs a continuous confirmation mechanism: if an anomaly is consistently observed within 3–5 consecutive monitoring cycles, it is confirmed as a metallic foreign object intrusion. Upon confirmation, the system triggers an alarm and sends a power limiting command to the wireless charging control module.

[0040] If |Δ f A value of T2 indicates a significant dielectric disturbance or coupling effect, which is highly likely to be a living foreign object. To ensure personal safety, the system skips the continuous verification process, immediately triggers an alarm, and forces the wireless charging module to limit its power.

[0041] S203: Reliability and Robustness Measures: System debouncing delay: Before making a final judgment, the system introduces a millisecond-level debouncing delay and compares it with the result of the previous cycle to avoid false alarms caused by a single anomaly.

[0042] System spatial parameter deviation: For dual-comb detection coils, Δ can be compared. f The system tracks the variation patterns at different positions of the coil. If a slight shift occurs at a certain position, the system can flag it as a low-level anomaly; if a large frequency shift occurs at a certain position, the alarm level will be increased.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A foreign object detection system for a wireless charging system for electric vehicles, characterized in that, include: A dual-comb self-resonant detection coil module, comprising a top comb coil (1), a PCB substrate (2), and a bottom comb coil (3). The top comb coil (1) is fixed to the upper surface of the PCB substrate (2) by a printing process, and the bottom comb coil (3) is fixed to the lower surface of the PCB substrate (2) by a printing process. The high-frequency signal excitation module, including a DDS module and a 3PD5651E analog-to-digital converter, is used to generate a sinusoidal signal with adjustable frequency, adjustable amplitude, and controllable phase, which is connected to the signal excitation terminal of the dual comb self-resonant detection coil module. The signal processing and detection module employs an orthogonal demodulation circuit to mix the high-frequency signal returned by the dual-comb self-resonant detection coil module with the original excitation signal and its 90-degree phase-shifted signal to generate two baseband signal components. The mixed signal is then filtered by a low-pass filter to remove the high-frequency components, resulting in orthogonal DC signals I and Q. The main control and discrimination module includes an FPGA, which controls the high-frequency signal excitation module to perform frequency scanning, acquires the I-channel and Q-channel signals demodulated by the signal processing and detection module, and executes logic based on the transmission line distributed parameter model of the dual-comb self-resonant detection coil module. The transmission line distributed parameter model includes the equivalent series transmission line resistance. R s Equivalent series transmission line inductance L s Equivalent parallel transmission line resistance R p1 Equivalent parallel transmission line inductance L p1 Equivalent parallel coupled inductor L p2 Equivalent parallel coupling capacitor C p1 and ground capacitance C p2 .

2. The foreign object detection system for a wireless charging system for electric vehicles according to claim 1, characterized in that, The top comb coil (1) is fixed to the upper surface of the PCB substrate (2) by printing process and forms the first comb electrode layer, which includes multiple comb teeth arranged in a plane; the bottom comb coil (3) is fixed to the lower surface of the PCB substrate (2) by printing process and forms the second comb electrode layer, which includes multiple comb teeth arranged in a plane; the first comb electrode layer and the second comb electrode layer are arranged in a mirror symmetrical manner; one end of either the first comb electrode layer or the second comb electrode layer is used as a signal excitation end for receiving a high-frequency excitation signal, and the other end is used as a signal detection end for outputting an induction signal; the dual comb self-resonant detection coil module is a distributed parameter network with self-resonant characteristics, and the input impedance of the dual comb self-resonant detection coil module exhibits series resonance or parallel resonance at a specific frequency.

3. The foreign object detection system for a wireless charging system for electric vehicles according to claim 1, characterized in that, In the signal processing and detection module, the I-channel signal is in phase with the original excitation signal, reflecting the in-phase component of the output signal of the dual-comb self-resonant detection coil module; the Q-channel signal is 90 degrees out of phase with the original excitation signal, reflecting the quadrature component of the output signal of the dual-comb self-resonant detection coil module.

4. The foreign object detection system for a wireless charging system for electric vehicles according to claim 1, characterized in that, The high-frequency signal excitation module includes a DDS module and a 3PD5651E analog-to-digital converter. The DDS module is a signal synthesis generator that uses high-precision direct digital frequency synthesis. The 3PD5651E analog-to-digital converter is used to generate a sine wave signal with adjustable frequency, adjustable amplitude, and controllable phase.

5. A foreign object detection system for a wireless charging system for electric vehicles according to claim 1, characterized in that, The foreign object detection system is connected to a wireless charging module, which is used to transmit wireless power to the electric vehicle wireless charging system and receive instructions from the foreign object detection system to limit the power.

6. A foreign object detection system for a wireless charging system for electric vehicles according to claim 1, characterized in that, Equivalent series transmission line resistance R s and equivalent series transmission line inductance L s Series connection, and positioned along the transmission line path; equivalent parallel transmission line resistance. R p1 Equivalent parallel transmission line inductance L p1 Equivalent parallel coupled inductor L p2 Equivalent parallel coupling capacitor C p1 and ground capacitance C p2 Parallel connection, and all connected in parallel with the transmission line, capacitance to ground C p2 One end is coupled to the equivalent parallel inductor L p2 Equivalent parallel coupling capacitor C p1 Connect one end to the ground.

7. A foreign object detection method for a wireless charging system for electric vehicles, applied to the foreign object detection system for a wireless charging system for electric vehicles as described in any one of claims 1-6, characterized in that, include: Step 1: The main control and discrimination module controls the DDS module to perform a full bandwidth frequency sweep from 0MHz to 25MHz with a step value of 50kHz. After the output stabilizes at each frequency point, the foreign object detection system maintains a fixed delay and performs a mixing operation through the signal processing and detection module to demodulate the quadrature DC signals of the I and Q outputs. Step 2: Simultaneously demodulate the orthogonal DC signals I and Q output by the signal processing and detection module, fully acquire the phase and amplitude information of the dual comb self-resonant detection coil module, store the voltage values ​​of I and Q in the buffer area, and obtain a complete frequency response curve containing multiple series and parallel resonant points. Step 3: In the execution logic of the main control and discrimination module, compare the amplitude curves and phase curves of the orthogonal DC signals of the I and Q paths to obtain local peak points and phase change points, identify candidate resonant frequency ranges, and mark all of them as candidate resonant points if multiple resonant points exist. Step 4: For the candidate resonant point, the foreign object detection system performs a secondary fine scan. During the secondary fine scan, the scan width is reduced to 1MHz and the step size is reduced to 10kHz. Compensation frequency points are inserted on both sides of the center frequency point of the amplitude and phase curves of the quadrature DC signals of the I and Q channels. The reference resonant frequency is accurately locked by the zero-crossing detection method of the Q channel. f_ref And simultaneously save the corresponding I / Q channel output signals; Step 5: Repeat step 3 to obtain candidate resonant points in the secondary fine scanning process, and collect multiple sets of data near the candidate resonant points in the secondary fine scanning process. Statistically analyze frequency jitter, noise distribution, and the system's own frequency stability based on the collected data, and automatically set the first threshold T1 and the second threshold T2 based on the statistical results. Step 6: Repeat steps 1-5 to perform the frequency sweep operation cyclically, and acquire the resonant frequency of the foreign object detection system in real time during each frequency sweep cycle. f_detect And obtain the detection frequency difference Δ f Based on the detection frequency difference Δ f The foreign object detection results are obtained using the first threshold T1 and the second threshold T2.

8. A foreign object detection method for a wireless charging system for electric vehicles according to claim 7, characterized in that, Step 6 specifically includes: Based on the resonant frequency of the real-time foreign object detection system f_detect and reference resonant frequency f_ref The detection frequency difference Δ is obtained by combining the adaptive moving average filtering algorithm. f ; If the detection frequency difference is |Δ f If |≤ the first threshold T1, it indicates that the resonance point is stable, the system determines that there is no foreign object intrusion, the foreign object detection system enters the low power mode, only maintains the minimum monitoring function, and reduces energy consumption. If the first threshold T1 ≤ detection frequency difference |Δ f If |Δ| < the second threshold T2, the foreign object detection system marks it as a suspected metallic foreign object and repeats the detection for 3-5 frequency sweep cycles. If each repeated frequency sweep cycle has a value of |Δ| < the first threshold T1 ≤ |Δ|, the detection system will determine the result. f If |≤ the second threshold T2, it is confirmed as a metal foreign object intrusion. The foreign object detection system triggers the corresponding alarm level and sends a power limit command to the wireless charging module. If the detection frequency difference is |Δ f |>At the second threshold T2, the foreign object detection system marks it as a living foreign object, immediately triggers the highest level alarm, and forces the wireless charging module to limit its power.

9. A foreign object detection method for a wireless charging system for electric vehicles according to claim 8, characterized in that, Before the foreign object detection system makes a judgment, it introduces a millisecond-level jitter reduction delay and compares it with the judgment result of the previous frequency sweep cycle. When a metal foreign object intrusion is identified, if the detection frequency difference |Δ f If a slight shift occurs in the detected position within the dual-comb self-resonant detection coil module, the foreign object detection system will trigger a low-level alarm. If a significant shift occurs in the detected position, a high-level alarm will be triggered.

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