Method and system for foreign object detection using a uniform magnetic field implemented with a bic mode

Abstract

The application relates to the technical field of foreign matter detection, in particular to a method and system for foreign matter detection in a uniform magnetic field realized by BIC mode, which comprises the following steps: providing a detection antenna, wherein the provided detection antenna comprises a printed circuit board, a plurality of metal open resonant rings arranged periodically on the front face of the printed circuit board, and a metal excitation ring arranged at the center position of the back face of the printed circuit board; transmitting an excitation signal to the metal excitation ring by using an excitation source, and then exciting BIC mode in the metal open resonant rings of the array; arranging a detection port at the center position of the front face of the printed circuit board; and detecting the induced voltage formed at the detection port in real time, wherein if the induced voltage detected in real time changes during the wireless charging process, it is judged that foreign matter exists. The application has the characteristic of non-locality, so no matter where the foreign matter appears in the detection antenna, the magnetic field will change dramatically, and the foreign matter can be detected rapidly and globally.

Description

Technical Field

[0001] This invention relates to the field of foreign object detection technology, and specifically to a method and system for detecting foreign objects using a uniform magnetic field implemented in BIC mode. Background Technology

[0002] In recent years, the new energy vehicle market has expanded rapidly, leading to a surge in demand for electric vehicle charging. Wireless charging technology for electric vehicles has also matured significantly. Currently, the mainstream wireless charging principle is magnetic resonant coupling. During high-power charging, a high-intensity magnetic field is generated near the system, which can easily affect surrounding living and non-living objects. In particular, metallic foreign objects falling near the transmitter can generate eddy currents, affecting charging efficiency and posing significant safety hazards. Therefore, a foreign object detection (FOD) subsystem is a crucial component of wireless charging systems.

[0003] Currently, mainstream FOD (Focus on Discharge) implementation methods include: power loss-based detection methods, detection coil-based detection methods, ultrasonic / radar-based detection methods, and vision / temperature sensor-based detection methods. Each of these methods has inherent drawbacks in different aspects. For example, power loss-based detection methods have low accuracy and sensitivity and are unsuitable for high-power charging systems; detection coil-based methods require complex detection circuits, resulting in redundant size and space consumption; ultrasonic / radar-based methods require expensive equipment such as sonar, are susceptible to interference from external conditions such as obstruction and collisions, and have extremely high requirements for installation location; vision / temperature sensor-based methods require software algorithm support, have low stability and robustness, and are excessively affected by environmental factors. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for foreign object detection using a uniform magnetic field realized by BIC mode, thereby solving the aforementioned insurmountable shortcomings of existing FOD detection methods.

[0005] The technical solution to achieve the above objectives is: This invention provides a method for foreign object detection using a uniform magnetic field implemented in BIC mode, for use in wireless charging. The method includes the following steps: A detection antenna is provided, which includes a printed circuit board, a plurality of metal open resonant rings periodically arranged on the front side of the printed circuit board, and a metal excitation ring located at the center of the back side of the printed circuit board. Each metal open resonant ring is connected to a lumped capacitor. The detection antenna is placed in front of the transmitter of the wireless charging device, so that the detection antenna is located between the transmitter and receiver of the wireless charging device. An excitation source is provided and connected to the metal excitation ring. The excitation signal is transmitted to the metal excitation ring using the provided excitation source, and then the magnetic dipole formed by the ring current on the metal excitation ring excites the BIC mode in the metal open resonant ring of the array. A detection port is provided at the center of the front side of the printed circuit board; The induced voltage generated at the detection port is detected in real time. If the detected induced voltage changes during the wireless charging process, it is determined that there is a foreign object near the transmitter of the wireless charger.

[0006] A further improvement of the method for detecting foreign objects using a uniform magnetic field achieved by the BIC mode in this invention is that the outer contour formed by the arrangement of multiple metal open resonant rings periodically arranged on the front side of the printed circuit board is a regular hexagon.

[0007] A further improvement of the method for detecting foreign objects using a uniform magnetic field achieved by the BIC mode in this invention is that a lumped capacitor is connected in series at the opening of the corresponding metal open resonant ring.

[0008] A further improvement of the method for detecting foreign objects using a uniform magnetic field achieved by the BIC mode in this invention is that the material and size of each of the metal open resonant rings are consistent.

[0009] A further improvement of the method for detecting foreign objects using a uniform magnetic field implemented in the BIC mode is that multiple detection antennas are provided, and the array of multiple detection antennas is set to cover the area where the wireless charging transmitter is located.

[0010] This invention also provides a system for foreign object detection using a uniform magnetic field implemented in BIC mode, for detecting foreign objects during wireless charging. The foreign object detection system includes: The detection antenna includes a printed circuit board, a plurality of metal open resonant rings periodically arranged on the front side of the printed circuit board, and a metal excitation ring located at the center of the back side of the printed circuit board. Each metal open resonant ring is connected to a lumped capacitor. The detection antenna is located on the front side of the transmitter of the wireless charging device and is located between the transmitter and receiver of the wireless charging device. An excitation source is connected to the metal excitation ring. The excitation source is used to transmit an excitation signal to the metal excitation ring, and then the magnetic dipole formed by the ring current on the metal excitation ring excites the BIC mode in the array of the metal open resonant ring. The detection port is located at the center of the front side of the printed circuit board; The detection circuit connected to the detection port is used to detect the induced voltage formed at the detection port in real time and determine whether the induced voltage changes. When the induced voltage changes, it is determined that there is a foreign object near the wireless charging transmitter.

[0011] A further improvement of the system for detecting foreign objects using a uniform magnetic field achieved by the BIC mode is that the outer contour formed by the periodic arrangement of multiple metal open resonant rings on the front side of the printed circuit board is a regular hexagon.

[0012] A further improvement of the system for detecting foreign objects using a uniform magnetic field realized by the BIC mode in this invention is that the lumped capacitor is connected in series at the opening of the corresponding metal open resonant ring.

[0013] A further improvement of the system for detecting foreign objects using a uniform magnetic field achieved by the BIC mode in this invention is that the material and size of each of the metal open resonant rings are consistent.

[0014] A further improvement of the system for detecting foreign objects using a uniform magnetic field achieved by the BIC mode is that the system has multiple detection antennas, and the array of multiple detection antennas is arranged to cover the area where the wireless charging transmitter is located.

[0015] The beneficial effects of the method and system for foreign object detection using a uniform magnetic field achieved by the BIC mode in this invention are as follows: The foreign object detection method and system of the present invention are configured with a detection antenna to excite a BIC mode at a specific frequency. The quality factor of the BIC mode can theoretically reach infinity. The magnetic field distribution in this mode has extremely high uniformity and strong stability when there is no foreign object. Unlike the local detection in traditional methods, the magnetic field in the BIC mode has the characteristic of non-locality. Therefore, no matter where the foreign object appears on the detection antenna, the magnetic field will change drastically, enabling rapid and global foreign object detection.

[0016] The foreign object detection method and system of the present invention have a detection area coverage of over 90%, exceeding most current mainstream methods; the main components of the detection antenna are PCB board and copper foil, which are extremely low in cost, simple in structure, easy to install, and occupy a small volume; the topology of the detection circuit and the complexity of the required microcontroller program are lower than those of mainstream methods, and the overall cost is reduced by at least 50%. Attached Figure Description

[0017] Figure 1The diagram shows the structure of the detection antenna in the method and system for detecting foreign objects using a uniform magnetic field implemented by the BIC mode according to the present invention. (a) is a schematic diagram of the front structure of the printed circuit board, (b) is a partial enlarged view of the front of the printed circuit board, and (c) is a schematic diagram of the structure of the metal excitation ring on the back of the printed circuit board.

[0018] Figure 2 This is a schematic diagram of the second embodiment of the detection antenna in the method and system for detecting foreign objects using a uniform magnetic field implemented by the BIC mode according to the present invention. (a) is a front view of the printed circuit board, (b) is a partially enlarged schematic diagram of the front view of the printed circuit board, (c) is a schematic diagram of the back view of the printed circuit board, and (d) is a schematic diagram of the front view of the printed circuit board, showing that a lumped capacitor is connected in series on each metal open resonant ring.

[0019] Figure 3 This is a schematic diagram of the magnetic field distribution in the BIC mode of the method and system for detecting foreign objects using a uniform magnetic field realized by the present invention.

[0020] Figure 4 This is a schematic diagram of the framework structure of the system for detecting foreign objects using a uniform magnetic field implemented in the BIC mode according to the present invention.

[0021] Figure 5 This is an example diagram of a car wireless charging system that utilizes the uniform magnetic field achieved by the BIC mode for foreign object detection, as described in this invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] See Figure 1 This invention provides a method and system for foreign object detection using a uniform magnetic field implemented in BIC mode, for use in wireless charging of electric vehicles. The method and system include a detection antenna and a circuit. Utilizing the uniform magnetic field implemented in BIC mode, the system exhibits non-locality; regardless of the location of the foreign object on the detection antenna, the magnetic field changes drastically, enabling rapid and global foreign object detection. The method and system for foreign object detection using a uniform magnetic field implemented in BIC mode are described below with reference to the accompanying drawings.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0025] See Figure 1 This diagram illustrates the structure of a first embodiment of the detection antenna in a method for detecting foreign objects using a uniform magnetic field implemented in the BIC mode, as well as the method of the present invention. The following is a related illustration. Figure 1 The present invention describes a system for detecting foreign objects using a uniform magnetic field implemented in the BIC mode.

[0026] like Figure 1 As shown, the system for foreign object detection using a uniform magnetic field implemented in BIC mode according to the present invention is used for foreign object detection during wireless charging. The foreign object detection system includes a detection antenna, an excitation source, a detection port, and a detection circuit. The detection antenna includes a printed circuit board 21, multiple metal open-ring resonators 22 periodically arranged on the front side of the printed circuit board 21, and a metal excitation ring 23 located at the center of the back side of the printed circuit board 21. Each metal open-ring resonator 22 is connected to a lumped capacitor. The detection antenna is located on the front side of the wireless charging transmitter and is located between the wireless charging transmitter and receiver. The excitation source is connected to the metal excitation ring 23 and is used to transmit an excitation signal to the metal excitation ring 23. The magnetic dipole formed by the ring current on the metal excitation ring 23 excites the BIC mode in the array of metal open-ring resonators 22. The detection port is located at the center of the front side of the printed circuit board 21. The detection circuit is connected to the detection port and is used to detect the induced voltage formed at the detection port in real time and determine whether the induced voltage changes. When the induced voltage changes, it is determined that there is a foreign object near the wireless charging transmitter.

[0027] When the wireless charging transmitter is located on the ground, the detection antenna of the present invention is located above the wireless charging transmitter, with the back of the printed circuit board close to the wireless charging transmitter and the front of the printed circuit board close to the wireless charging receiver.

[0028] Furthermore, such as Figure 1 and Figure 2 As shown, the outer contour formed by the multiple metal open-ring resonators 22 periodically arranged on the front side of the printed circuit board 21 is a regular hexagon. Preferably, the number of metal open-ring resonators 22 can be set according to the size of the printed circuit board 21.

[0029] The arrangement of the metal open-ring resonators 22 possesses mirror symmetry or rotational symmetry to strictly prohibit dipole / higher-order multipole radiation channels. The spacing between the metal open-ring resonators 22 arranged laterally or diagonally in the same row is equal, and the material and size of each metal open-ring resonator 22 are consistent. The material of the metal open-ring resonators 22 is copper. The size, linewidth, and period length of the metal open-ring resonators 22 can be designed according to the actual detection requirements. The size selection can be determined based on the size of the foreign object to be detected. For example, the outer diameter of the metal open-ring resonator 22 can be set to 13 mm, the linewidth to 1.5 mm, and the period length (i.e., the center distance between two adjacent metal open-ring resonators 22) to 13.5 mm. The opening direction of each metal open-ring resonator 22 is consistent, all facing downwards. Preferably, the metal open-ring resonators 22 can be made by etching copper foil with a thickness of 1 oz.

[0030] One row of two adjacent rows of metal open resonant rings 22 is positioned at the middle position of two adjacent metal open resonant rings 22 in the other row, so that the outer contours of the three metal open resonant rings 22 form an isosceles triangle.

[0031] Furthermore, the lumped capacitors are connected in series at the openings of the corresponding open-circuit metal resonant rings 22. The lumped capacitors connected in series on each open-circuit metal resonant ring 22 have equal capacitance.

[0032] Furthermore, the size of the metal excitation ring 23 can be set according to the actual detection requirements. Specifically, it can be set according to the size of the foreign object to be detected. For example, the outer diameter of the metal excitation ring 23 can be set to 6mm, and the material of the metal excitation ring 23 can be copper. The thickness of the printed circuit board 21 can be set according to actual requirements. For example, the thickness of the printed circuit board 21 can be set to 1mm.

[0033] Furthermore, the detection port is a high-impedance detection port, which utilizes the high impedance characteristic to ensure that it does not affect the magnetic field distribution in the system.

[0034] The excitation source transmits a specific frequency excitation signal to the metal excitation ring 23 through the excitation circuit, forming a ring current on the metal excitation ring 23. The magnetic dipole formed by this ring current excites a BIC mode in the array of metal open resonant rings 22. The magnetic field distribution in this mode has a high degree of uniformity, such as... Figure 3As shown, the detection port on the front of the printed circuit board generates an induced voltage under the action of the magnetic field. The analog voltage value is transmitted back to the detection circuit. The microcontroller in the detection circuit converts the analog voltage into a digital value and records it as the standard value when the system is in a foreign object-free state. When a foreign object appears in the system, the uniform field distribution is disrupted, and the induced voltage on the detection port changes. After the digital value detected by the microcontroller is different from that in the foreign object-free state, it is determined that a foreign object is present.

[0035] like Figure 4 As shown, the excitation circuit outputs an excitation signal of a specific frequency to the metal excitation ring. The magnetic dipole formed by the ring current excites a BIC mode in the metal open resonant ring array. At this time, the detection port located on the front of the printed circuit board generates an induced voltage under the action of the magnetic field, and transmits the analog voltage value back to the detection circuit section. Figure 5 As shown, when a metallic foreign object (such as a small iron block in the figure) appears in the working range of the wireless charging system, the uniform field distribution is disrupted, the induced voltage on the detection port changes, and the digital quantity detected by the microcontroller is different from that in the state without foreign objects, thus determining that there is a foreign object present.

[0036] In one specific embodiment of the present invention, there are multiple detection antennas, and the array of multiple detection antennas is arranged to cover the area where the wireless charging transmitter is located.

[0037] Accordingly, the number of excitation circuits and detection circuits for the corresponding detection antennas is consistent with the number of detection antennas. Each excitation circuit can be connected to an excitation source, or each excitation circuit can be connected to an excitation source.

[0038] The excitation circuit outputs an excitation signal of a specific frequency to the metal excitation ring. This specific frequency can be calculated based on the parameters of each metal open resonator ring set on the detection antenna. This specific frequency can be selected from the resonant frequency of the metal open resonator ring and the frequency value near it.

[0039] The working principle of the foreign object detection system of the present invention is as follows: The detection antenna of this invention consists of a metal open-circuit resonant ring array on the front side of a PCB (printed circuit board) and a metal excitation ring on the back side. At a specific frequency, the magnetic dipole formed by the current in the metal excitation ring excites a BIC mode in the metal open-circuit resonant ring array on the front side. Theoretically, its quality factor can reach infinity, and in practical systems, it can achieve orders-of-magnitude improvements. The magnetic field distribution in this mode exhibits extremely high uniformity and strong stability in the absence of foreign objects. Unlike the localized detection in traditional methods, the magnetic field in the BIC mode is non-local, and the detection port is high-impedance, which does not affect the field distribution in the system. Therefore, regardless of where a foreign object appears on the detection antenna, the magnetic field will change drastically, enabling rapid and global foreign object detection.

[0040] Bound states in the continuum (BIC) are a special type of wave. Generally, if an electromagnetic wave of a certain frequency is within the propagation band in space, its energy will continuously dissipate outward in the form of leakage waves, leading to a rapid decay of the overall energy. However, BIC-mode waves are an exception. They are within the propagation band, but their energy is highly localized. All leakage and coupling channels are completely prohibited. Therefore, microscopic particles in BIC mode are theoretically under extremely strong confinement and possess an infinitely large quality (Q) factor.

[0041] BIC modes have the following characteristics: ① They are more easily excited in periodic / resonant structures; ② Local excitation can form an overall field distribution in the structure; ③ The mode itself is very sensitive to disturbances. Based on these characteristics, when a foreign object invades the detection area, its dielectric constant and geometric dimensions will slightly perturb the symmetry and phase matching conditions of the BIC mode, causing the originally strictly suppressed radiation channels to partially open, the Q factor to drop sharply, and accompanied by a significant shift in the reflection spectrum or broadening of the absorption peak. By identifying this response through a monitoring system (or detection circuit), subwavelength-level foreign object identification and location can be achieved.

[0042] The realization of a uniform magnetic field in BIC mode requires satisfying the dual constraints of structural symmetry and phase matching. On the one hand, the unit structure must possess structural symmetry, which can be either mirror symmetry or rotational symmetry, to strictly prohibit dipole / higher-order multipole radiation channels. On the other hand, the consistency of the structure between adjacent units must be ensured by precisely controlling geometric parameters (such as linewidth, period ratio, and coupling strength) and electromagnetic parameters (such as capacitance, inductance, and resonant frequency), so that far-field radiation undergoes complete destructive interference in the continuous spectrum. Only through the synergistic effect of these two factors can a non-radiative uniform magnetic field localized mode be formed at the operating frequency (which is the specific frequency of the excitation signal output by the excitation circuit, which is the resonant frequency of the metal open-loop resonator and its surrounding frequencies).

[0043] The following experiment was conducted on the foreign object detection system of this invention: A detection system was constructed by etching resonant coils of specific size and period length onto an FR4 board (50cm*60cm). Excitation and receiving ports of specific frequencies were built on both sides of the central region. An excitation signal was input through the excitation port, and the induced voltage was detected at the receiving port. Different foreign objects were then placed within the 50cm*60cm area. After the foreign object was placed, the induced voltage at the receiving port changed. The experiment showed that the foreign object detection system of this invention can achieve a seamless detection effect within the area. Regardless of where the foreign object lands within the area, it causes a drastic change in the overall field distribution. Foreign objects ranging in size from large aluminum foil to paperclips can be successfully detected.

[0044] This invention also provides a method for detecting foreign objects using a uniform magnetic field implemented in BIC mode, which is used for detecting foreign objects during wireless charging. The method for detecting foreign objects is described below.

[0045] The foreign object detection method of the present invention includes the following steps: A detection antenna is provided, which includes a printed circuit board, multiple metal open resonant rings periodically arranged on the front of the printed circuit board, and a metal excitation ring located at the center of the back of the printed circuit board. Each metal open resonant ring is connected to a lumped capacitor. The detection antenna is placed in front of the transmitter of the wireless charging device, so that the detection antenna is located between the transmitter and receiver of the wireless charging device. An excitation source is provided and connected to a metal excitation ring. The excitation signal is transmitted to the metal excitation ring using the provided excitation source. Then, the magnetic dipole formed by the ring current on the metal excitation ring excites the BIC mode in the metal open resonant ring of the array. A detection port is set at the center of the front side of the printed circuit board; The induced voltage at the detection port is detected in real time. If the detected induced voltage changes during the wireless charging process, it is determined that there is a foreign object near the wireless charging transmitter.

[0046] In one specific embodiment of the present invention, the outer contour formed by the arrangement of multiple metal open resonant rings periodically on the front side of the printed circuit board is a regular hexagon.

[0047] In one specific embodiment of the present invention, a lumped capacitor is connected in series at the opening of the corresponding metal open resonant ring.

[0048] In one specific embodiment of the present invention, the materials and dimensions of each metal open resonant ring are consistent.

[0049] In one specific embodiment of the present invention, multiple detection antennas are provided, and multiple detection antenna arrays are arranged to cover the area where the wireless charging transmitter is located.

[0050] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A method for foreign object detection using a uniform magnetic field implemented in BIC mode, used for foreign object detection during wireless charging, characterized in that, The foreign object detection method includes the following steps: A detection antenna is provided, which includes a printed circuit board, a plurality of metal open resonant rings periodically arranged on the front side of the printed circuit board, and a metal excitation ring located at the center of the back side of the printed circuit board. Each metal open resonant ring is connected to a lumped capacitor. The detection antenna is placed in front of the transmitter of the wireless charging device, so that the detection antenna is located between the transmitter and receiver of the wireless charging device. An excitation source is provided and connected to the metal excitation ring. The excitation signal is transmitted to the metal excitation ring using the provided excitation source, and then the magnetic dipole formed by the ring current on the metal excitation ring excites the BIC mode in the metal open resonant ring of the array. A detection port is provided at the center of the front side of the printed circuit board; The induced voltage generated at the detection port is detected in real time. If the detected induced voltage changes during the wireless charging process, it is determined that there is a foreign object near the transmitter of the wireless charger.

2. The method for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 1, characterized in that, The outer contour formed by the arrangement of multiple metal open resonant rings periodically on the front side of the printed circuit board is a regular hexagon.

3. The method for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 1, characterized in that, Connect the lumped capacitor in series at the opening of the corresponding metal open resonant ring.

4. The method for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 1, characterized in that, The materials and dimensions of each of the aforementioned metal open-ring resonators are consistent.

5. The method for detecting foreign objects using a uniform magnetic field achieved by the BIC mode as described in claim 1, characterized in that, The provided detection antennas are multiple, and the multiple detection antenna arrays are set up to cover the area where the wireless charging transmitter is located.

6. A system for foreign object detection using a uniform magnetic field implemented in BIC mode, used for foreign object detection during wireless charging, characterized in that, The foreign object detection system includes: The detection antenna includes a printed circuit board, a plurality of metal open resonant rings periodically arranged on the front side of the printed circuit board, and a metal excitation ring located at the center of the back side of the printed circuit board. Each metal open resonant ring is connected to a lumped capacitor. The detection antenna is located on the front side of the transmitter of the wireless charging device and is located between the transmitter and receiver of the wireless charging device. An excitation source is connected to the metal excitation ring. The excitation source is used to transmit an excitation signal to the metal excitation ring, and then the magnetic dipole formed by the ring current on the metal excitation ring excites the BIC mode in the array of the metal open resonant ring. The detection port is located at the center of the front side of the printed circuit board; The detection circuit connected to the detection port is used to detect the induced voltage formed at the detection port in real time and determine whether the induced voltage changes. When the induced voltage changes, it is determined that there is a foreign object near the wireless charging transmitter.

7. The system for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 6, characterized in that, The outer contour formed by the arrangement of multiple metal open resonant rings periodically on the front side of the printed circuit board is a regular hexagon.

8. The system for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 6, characterized in that, The lumped capacitor is connected in series at the opening of the corresponding metal open resonant ring.

9. The system for detecting foreign objects using a uniform magnetic field implemented in BIC mode as described in claim 6, characterized in that, The materials and dimensions of each of the aforementioned metal open-ring resonators are consistent.

10. The system for detecting foreign objects using a uniform magnetic field achieved through BIC mode as described in claim 6, characterized in that, The detection antennas are multiple, and the array of multiple detection antennas is arranged to cover the area where the wireless charging transmitter is located.

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