An unmanned aerial vehicle wireless charging method based on electromagnetic metasurface

Abstract

The application discloses a kind of unmanned aerial vehicle wireless charging methods based on electromagnetic super surface, it is related to wireless power transmission technical field.The method includes: platform is in low power detection mode to electromagnetic super surface unit is implemented tuning scanning one by one, and the increment of the real part of main transmitting end input impedance relative to the no-load baseline state is extracted;According to the impedance increment, determine the initial target area where the receiving coil is located and reconstruct its two-dimensional position coordinates;Accordingly, select local active subarray, carry out local empowerment and local tuning state setting to its internal unit, while making peripheral unit in low response tuning state, so as to form local high coupling magnetic field in the target area corresponding to the position of receiving coil, finally switch to power transmission mode and carry out power transmission.Through the above method, the application can realize receiving coil positioning without external positioning sensor and unmanned aerial vehicle side active communication feedback, and can improve the charging efficiency and magnetic field utilization rate of unmanned aerial vehicle wireless charging system under the working condition of deviation.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission technology, specifically to a near-field magnetic coupling wireless charging method for automatic recharging scenarios of unmanned aerial vehicles (UAVs), and more particularly to a UAV wireless charging method that utilizes the change in the real part of the input impedance of the main transmitter to realize the position sensing of the receiving coil, and forms a local high-coupling magnetic field region based on an electromagnetic metasurface array. Background Technology

[0002] Currently, drones are widely used in scenarios such as inspection, surveying, logistics, security, and emergency operations. However, their endurance is usually limited by the capacity of their onboard batteries. Building an automated recharging platform that allows drones to autonomously land and wirelessly recharge during mission breaks is an important means to improve mission continuity and reduce operating costs. In existing drone wireless charging processes, the main problem affecting charging efficiency and stability lies in the relative misalignment between the transmitter and receiver. During actual landing, drones are often affected by navigation errors, airflow disturbances, and landing bounce, making it difficult for the receiving coil to accurately land above the optimal charging area. This leads to problems such as high energy loss, low charging efficiency, and even charging interruptions.

[0003] To improve the anti-offset capability of wireless charging systems for drones, existing technologies typically employ the following approaches: The first approach expands the magnetic field coverage of the charging platform by increasing the size of the transmitting coil. However, this approach tends to result in uneven magnetic field distribution and significant magnetic leakage in non-target areas. Variable-pitch structures are designed to improve the magnetic field distribution of the transmitting coils, but magnetic field waste remains. The second approach uses multi-transmitter coil arrays or multi-unit coil platforms. It detects the presence of a receiver in a specific area and selectively activates the corresponding unit to reduce ineffective transmission energy. However, this approach requires additional hardware and software systems for position detection, increasing system complexity and cost. Furthermore, only a few coils operate during charging, resulting in a relatively weak magnetic field. The third approach relies on visual cameras, infrared sensors, etc., for position correction based on the displacement of the transmitting coils, or on the drone's active search and communication feedback mechanisms to improve landing accuracy. The former introduces additional sensors, increasing system hardware costs and implementation complexity; while the latter's frequent search and communication interactions inadvertently increase the drone's onboard computing power and power consumption.

[0004] In recent years, electromagnetic metasurfaces have been introduced into wireless charging systems to improve magnetic field distribution. By adjusting the resonant state of local cells in the array, electromagnetic metasurfaces can spatially control the near-field magnetic flux distribution, thus providing a new approach to improve the charging performance degradation caused by drone landing deviations. However, existing electromagnetic metasurface wireless charging schemes typically assume that the target load position is known, or rely on receiver feedback, external position detection methods, or a unified solution for the entire array to achieve magnetic field reconstruction.

[0005] Therefore, for the scenario of automatic recharging of drones, how to complete the position perception of the receiving coil using only the measurable information on the transmitting end without introducing additional sensors and active feedback from the receiving end, and further form a local high-coupling magnetic field region corresponding to the position of the receiving coil, so as to improve the wireless charging efficiency and stability under offset conditions, is a technical problem that urgently needs to be solved in this application scenario. Summary of the Invention

[0006] The main objective of this invention is to provide a wireless charging method for drones based on electromagnetic metasurfaces, in order to solve the problems of large energy loss, reduced charging efficiency, and even charging interruption caused by the relative misalignment between the transmitter and receiver in the existing wireless charging process of drones, and to reduce the system complexity caused by external positioning sensors or active search and feedback communication on the drone side.

[0007] To achieve the above objectives, this invention provides a wireless charging method for unmanned aerial vehicles (UAVs) based on electromagnetic metasurfaces, the specific technical solution of which is as follows:

[0008] A wireless charging method for unmanned aerial vehicles (UAVs) based on electromagnetic metasurfaces is disclosed. This method is implemented using a wireless charging platform, which includes a main transmitting coil, an electromagnetic metasurface array positioned above the main transmitting coil, an input impedance detection module, a central control module, and a unit tuning module. The method comprises the following steps: S1: Control the wireless charging platform to enter a low-power detection mode, so that the main transmitting coil works at a fixed nominal frequency, and control the multiple electromagnetic metasurface units in the electromagnetic metasurface array to change their tuning states one by one; synchronously collect the real part of the input impedance of the main transmitting end in the corresponding scanning state, and compare it with the real part of the input impedance in the no-load baseline state to obtain the increment of the real part of the input impedance corresponding to each electromagnetic metasurface unit. S2: Determine the initial target region where the receiving coil of the UAV to be charged is located based on the two-dimensional distribution of the real part increment of the input impedance, and extract the real part increment of the input impedance of multiple electromagnetic metasurface units in the neighborhood of the initial target region to reconstruct the two-dimensional position coordinates of the center of the receiving coil in the global array coordinate system. S3: Select a local activation subarray in the global array based on the two-dimensional position coordinates, and update the physical unit number corresponding to the local activation subarray when the two-dimensional position coordinates cross the boundary of the current local activation subarray. S4: Locally weight and locally tune the electromagnetic metasurface units within the local activation subarray, and put the electromagnetic metasurface units outside the local activation subarray into a low-response tuning state to reduce the magnetic field participation in non-target regions. S5: The size and spatial coverage of the local activator array are constrained according to the physical size of the receiving coil to form a local high-coupling magnetic field region in the target area corresponding to the position of the receiving coil, and the power transmission mode is switched to transmit electrical energy to the receiving coil through the main transmitting coil and the local activator array.

[0009] Preferably, in step S2, the two-dimensional position coordinates of the receiving coil center in the global array coordinate system are obtained based on the weighted distribution of the center coordinates of multiple electromagnetic metasurface units in the neighborhood of the initial target region and the corresponding real part increments of the input impedance; the local activation subarray is composed of M × N Composed of physical units M and N It is an integer not less than 2, and the size of the local activation subarray is not greater than the size of the global array; M and N The value of is determined based on the matching relationship between the size of the receiving coil and the side length of the electromagnetic metasurface unit.

[0010] Preferably, in step S4, a continuous weighted distribution centered on the two-dimensional position coordinates and monotonically decreasing with increasing distance is constructed, and sampling is performed at the center of each electromagnetic metasurface unit within the local activation subarray to obtain the weighting coefficients of each electromagnetic metasurface unit; based on the weighting coefficients and a preset reference current, the target current distribution of each electromagnetic metasurface unit is determined; based on the coupling relationship between the local activation subarray and its main transmitting coil, receiving coil, and electromagnetic metasurface units outside the local activation subarray that are in a low-response tuning state, a local impedance matrix is ​​constructed, and combined with the target current distribution, the target total capacitance of each electromagnetic metasurface unit within the local activation subarray is solved; according to the pre-established capacitance-bias voltage mapping relationship, the target total capacitance is converted into the control voltage of the corresponding electromagnetic metasurface unit to complete the local tuning state setting of each electromagnetic metasurface unit within the local activation subarray.

[0011] Beneficial effects: 1. This invention achieves the position sensing of the receiving coil by changing the real part of the input impedance of the main transmitter, without the need for additional external positioning sensors or active feedback of position information from the UAV side, thereby reducing external sensing and feedback links, simplifying the platform structure and reducing the overall implementation complexity.

[0012] 2. This invention dynamically selects a local activation subarray based on the two-dimensional position coordinates of the receiving coil center in the global array coordinate system, and puts the electromagnetic metasurface units outside the local activation subarray in a low-response tuning state. This can reduce the magnetic field participation in non-target areas, and form a local high-coupling magnetic field region in the target area corresponding to the position of the receiving coil under the condition of solving the local impedance matrix based on the coupling relationship. This enhances the local magnetic field concentration and suppresses magnetic field diffusion and leakage interference in non-target areas.

[0013] 3. This invention forms a complete closed-loop control link from position perception to local magnetic field construction by initial target area identification, two-dimensional position coordinate reconstruction, selection of local activator array, construction of continuous weighted distribution, determination of weighting coefficients, determination of target current distribution, solution of local impedance matrix based on coupling relationship, and control of capacitor and bias voltage mapping. This improves the platform's adaptive adjustment capability to the offset of UAV receiving coil. Attached Figure Description

[0014] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the drone wireless charging platform provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a single electromagnetic metasurface unit and a local tuning circuit provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the wireless charging method for drones based on electromagnetic metasurfaces provided in an embodiment of the present invention.

[0015] In the diagram: 1. Charging platform base; 2. Power conversion module; 3. Central control module; 4. Input impedance detection module; 5. Main transmitting coil; 6. Electromagnetic metasurface array; 7. Unit tuning module; 8. UAV body; 9. Receiving coil; C 0. Fixed resonant capacitor; C 1. First DC blocking capacitor; C 2. Second DC blocking capacitor; C VAR Variable capacitor; L 1. First isolation inductor; L 2. Second isolation inductor; R 1. Current-limiting resistor; V TUNE 1. Tuning the bias voltage; S1-S5. Steps of the drone wireless charging method. Detailed Implementation

[0016] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention. All equivalent substitutions, improvements, and modifications made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0017] In the description of this invention, unless otherwise expressly defined, the terms "connection" and "electrical connection" should be interpreted broadly, including both direct connections and indirect connections through intermediate components; the terms "above," "below," "center," "boundary," and other directional relationships are used only to facilitate the description of the technical solutions of this invention and do not constitute a limitation on the scope of protection of this invention.

[0018] Example 1 like Figure 1 and Figure 2 As shown, the wireless charging method for drones based on electromagnetic metasurfaces in this embodiment is implemented on a wireless charging platform. The wireless charging platform includes a charging platform base 1, a power conversion module 2, a central control module 3, an input impedance detection module 4, a main transmitting coil 5, an electromagnetic metasurface array 6, and a unit tuning module 7; the object to be charged is a drone, and a receiving coil 9 is installed on the bottom of the drone body 8.

[0019] The power conversion module 2 converts external input electrical energy into a form suitable for driving the main transmitting coil 5. The central control module 3 performs low-power detection control, incremental acquisition of the real part of the input impedance, two-dimensional position coordinate reconstruction, selection of the local activator array, local weighting, local tuning state setting, and power transmission mode switching. The input impedance detection module 4 acquires the real part of the input impedance of the main transmitting end. The unit tuning module 7 outputs tuning control signals to each electromagnetic metasurface unit in the electromagnetic metasurface array 6. The main transmitting coil 5 and the receiving coil 9 form a tunable near-field magnetic coupling channel through the electromagnetic metasurface array 6.

[0020] In a preferred embodiment, the central control module 3 employs a microcontroller, digital signal processor, or other controller with real-time computing capabilities; the unit tuning module 7 includes a multi-channel digital-to-analog converter network and a voltage-controlled variable capacitor. The central control module outputs digital control commands to the digital-to-analog converter via I2C, SPI, or other communication buses. The digital-to-analog converter converts these commands into analog bias voltages and applies them to the corresponding tuning branches of each electromagnetic metasurface unit, thereby achieving dynamic reconstruction of the resonant state of each electromagnetic metasurface unit.

[0021] In a preferred embodiment, the power transmission section includes an inverter drive unit. The central control module 3 switches between low-power detection mode and power transmission mode by adjusting the duty cycle, pulse width, or equivalent output power of the inverter drive signal. Each electromagnetic metasurface unit in the electromagnetic metasurface array 6 adopts a planar resonant coil structure. Figure 2 The local tuning circuit shown is a preferred circuit topology used to illustrate that the equivalent total capacitance of the electromagnetic metasurface unit can be adjusted by bias control. This invention is not limited to this specific circuit connection form.

[0022] Furthermore, such as Figure 2 As shown, a single electromagnetic metasurface unit includes a circular planar helical resonant coil and a locally tuned circuit electrically connected to it. The locally tuned circuit includes a fixed resonant capacitor. C 0. Variable capacitor C VAR First DC blocking capacitor C 1. Second DC blocking capacitor C 2. First isolation inductor L 1. Second isolation inductor L 2. Current-limiting resistor R 1 and tuning bias voltage V TUNE Input terminal. Among them, the fixed resonant capacitor... C 0 is used to adjust the fundamental resonant frequency of the electromagnetic metasurface unit; variable capacitor C VAR The capacitance value varies with the tuning bias voltage. V TUNE It changes accordingly, used to alter the resonant state of the corresponding electromagnetic metasurface unit; the first DC blocking capacitor C 1 and second DC blocking capacitors C 2. Used to isolate the bias branch and prevent tuning bias voltage. V TUNE A DC short circuit is formed in the resonant circuit; the first isolation inductor L 1 and second isolation inductors L 2. Used to provide isolation between the bias control branch and the high-frequency resonant branch, so as to allow independent tuning of each electromagnetic metasurface unit; current-limiting resistor. R 1 is used to limit the bias branch current. The central control module 3 changes the current through the unit tuning module 7. V TUNE ,make C VAR Changes occur, thereby altering the equivalent total capacitance and resonant state of the electromagnetic metasurface unit.

[0023] In a preferred embodiment, a fixed resonant capacitor is used. C 0 can be 220pF, the first DC blocking capacitor C1 and second DC blocking capacitors C 2 can be 1nF each, the first isolation inductor L 1 and second isolation inductors L 2 can be 100μH, current-limiting resistors. R 1. 51Ω is available; variable capacitor C VAR Voltage-controlled capacitors can be used, and their capacitance value varies with... V TUNE Variations, such as the tuning bias voltage of the commercial varactor diode SKYWORKS SMV1255. V TUNE The voltage can vary from 0V to 8V, and the corresponding capacitance range can vary from 4.7pF to 81.2pF. The above parameters are only a set of preferred implementation parameters and do not constitute a limitation on the scope of protection of this invention; in actual implementation, the above parameters can be adjusted accordingly based on the geometric dimensions of the electromagnetic metasurface unit, the target operating frequency, and the required tuning range.

[0024] Example 2 like Figure 3 As shown, in step S1, the central control module 3 first controls the wireless charging platform to enter the low-power detection mode, so that the main transmitting coil 5 works at a fixed nominal frequency, and controls the multiple electromagnetic metasurface units in the electromagnetic metasurface array 6 to change their tuning states one by one; the input impedance detection module 4 synchronously collects the real part of the input impedance of the main transmitting end in the corresponding scanning state, and compares it with the real part of the input impedance in the no-load baseline state to obtain the increment of the real part of the input impedance corresponding to each electromagnetic metasurface unit.

[0025] In a preferred embodiment, to establish an unloaded baseline, the central control module 3 first controls each electromagnetic metasurface unit in the electromagnetic metasurface array 6 to be in a deeply detuned state, and records the real part of the input impedance of the main transmitter at this time as the unloaded baseline value. The deeply detuned state refers to adjusting the resonant state of the electromagnetic metasurface unit to a significantly deviated frequency from the nominal operating frequency through the unit tuning module 7, so that the induced current of the unit at the nominal operating frequency is significantly lower than that of the electromagnetic metasurface unit in the local activator array that is in operation, thus exhibiting a low-response tuning state in space magnetic field manipulation. By ensuring that the global units are in the aforementioned deeply detuned state when establishing the baseline, the additional coupling effect of the array itself on the detection signal can be reduced, improving the stability and contrast of the subsequent extraction of the real part increment of the input impedance.

[0026] Let the first i The real part of the main emitter input impedance of each electromagnetic metasurface unit in the scanning state is: R in,i The real part of the main transmitter input impedance under no-load baseline conditions is: R in,0 Then the firsti The real part increment of the input impedance corresponding to each electromagnetic metasurface unit is defined as Δ. R i = R in,i - R in,0 When the scanned unit is located below or near the receiving coil 9, the influence of the receiving-side circuit on the transmitting-side coupling path is more significant, therefore the corresponding... The central control module 3 is relatively large. It determines the Δ value based on the corresponding values ​​of all units. R i The two-dimensional distribution determines the initial target area where the receiving coil 9 of the drone to be charged is located.

[0027] In step S2, the central control module 3 extracts the real part increment of the input impedance of multiple electromagnetic metasurface units in the neighborhood of the initial target region, and reconstructs the two-dimensional position coordinates of the center of the receiving coil 9 in the global array coordinate system by combining the center coordinates of these units.

[0028] In a preferred embodiment, the two-dimensional position coordinates of the center of the receiving coil 9 in the global array coordinate system are obtained based on the weighted distribution of the center coordinates of multiple electromagnetic metasurface units within the neighborhood of the initial target region and the corresponding real part increments of the input impedance. For example, a two-dimensional weighted centroid method can be used for position reconstruction. Let the center coordinates of the multiple electromagnetic metasurface units participating in the reconstruction be (…). x i , y i The corresponding real part increments of the input impedance are Δ R i Then the two-dimensional position coordinates of the center of receiving coil 9 ( x 0, y 0) can be obtained from the following formula:

[0029]

[0030] Through the above process, the continuous coordinate reconstruction of the center position of the receiving coil 9 can be completed using only measurable information from the transmitting end, without introducing external positioning sensors or relying on active feedback from the receiving end.

[0031] Example 3 In step S3, the central control module 3 uses the two-dimensional position coordinates obtained in step S2 ( x 0, y0), Select a local active subarray in the global array. When the two-dimensional position coordinates cross the boundary of the current local active subarray, the central control module 3 updates the physical unit number corresponding to the local active subarray so that the local active subarray dynamically migrates as the position of the receiving coil 9 changes.

[0032] The local activation subarray is composed of M × N Composed of physical units M and N It is an integer not less than 2, and the size of the local activation subarray is not greater than the size of the global array; M and N The value of is determined based on the matching relationship between the size of the receiving coil 9 and the side length of the electromagnetic metasurface unit. For local hotspot focusing scenarios, the local activation subarray can preferably be 2×2, 3×3, 4×4 or other subarray sizes suitable for covering the effective working area of ​​the receiving coil 9, but the present invention is not limited to the above specific sizes.

[0033] In step S4, the central control module 3 performs local weighting and local tuning state settings on the electromagnetic metasurface units within the local activation subarray, while simultaneously placing the electromagnetic metasurface units outside the local activation subarray in a low-response tuning state to reduce the magnetic field participation in non-target regions. The low-response tuning state refers to the tuning state where the induced current, magnetic field disturbance, or real part change of input impedance of the electromagnetic metasurface units outside the local activation subarray at the nominal operating frequency is lower than the corresponding response of the working units within the local activation subarray. The low-response tuning state can be predetermined through frequency sweep simulation, input impedance response testing, induced current testing, or capacitor-bias voltage calibration. The low-response tuning state is not limited to a fixed capacitance value, nor is it limited to a completely off state. To avoid abrupt changes in the edge field caused by a step-type uniform excitation, in this embodiment, the central control module constructs a system based on the two-dimensional position coordinates (…). x 0, y A continuous weighted distribution centered at 0) and monotonically decaying with increasing distance is obtained by sampling at the center of each electromagnetic metasurface unit within the local activation subarray to obtain the weighting coefficients of each electromagnetic metasurface unit.

[0034] In a preferred embodiment, the continuous weighting distribution can be represented by a two-dimensional Gaussian decay function. If the first... i The center coordinates of each electromagnetic metasurface unit are ( x i , y i If the weighting coefficient is ), then its weighting coefficient is ). c i It can be represented as:

[0035] in, σ This refers to the attenuation parameter used to control the spatial width of a localized, highly coupled magnetic field region. The attenuation parameter... σ The spatial distribution range of the local high-coupling magnetic field region should be selected to match the effective operating area of ​​the receiving coil 9, and the weighting coefficients of each electromagnetic metasurface unit at the edge of the local activator array should be significantly attenuated compared to the central region, so as to ensure the smooth continuity of the local magnetic field distribution and suppress abrupt changes in the edge field.

[0036] Example 4 After obtaining the weighting coefficients of each electromagnetic metasurface unit within the local activation subarray, the central control module 3 determines the target current distribution of each electromagnetic metasurface unit based on the weighting coefficients and a preset reference current. Further, based on the coupling relationship between the local activation subarray and its connections with the main transmitting coil 5, the receiving coil 9, and the electromagnetic metasurface units outside the local activation subarray that are in a low-response tuning state, a local impedance matrix is ​​constructed. Combined with the target current distribution, the target total capacitance of each electromagnetic metasurface unit is calculated. Then, according to the pre-established capacitance-bias voltage mapping relationship, the target total capacitance is converted into the control voltage of the corresponding electromagnetic metasurface unit to complete the local tuning state setting of each electromagnetic metasurface unit within the local activation subarray.

[0037] For any electromagnetic metasurface unit within the local activator array i Assume that its target current satisfies: I i = c i I x ,in, c i For the first i Weighting coefficients of each electromagnetic metasurface unit. I x This is the reference current.

[0038] Furthermore, let the first i The self-impedance of each electromagnetic metasurface unit is: Z ii = R i + jωL i +1 / jωC i ,in, R i The unit equivalent resistance, L i For unit self-inductance, C i The target total capacitance is to be determined; the first... i The unit and the firstj The mutual impedance between the units is: Z ij = jωM ij ,in, M ij For the first i The unit and the first j Mutual inductance between units.

[0039] Based on the impedance coupling relationship between the local activator array and the electromagnetic metasurface units outside the local activator array that are in a low-response tuning state, and under the approximate condition of neglecting the first-order influence of unit ohmic losses under low-frequency operating conditions, the central control module 3 can obtain the target total capacitance that satisfies the target current distribution based on the local impedance matrix. For any unit within the local activator array... i The target total capacitance can be expressed as:

[0040] in, A ( t () represents the set of cells corresponding to the current local activation subarray. ω This is the nominal operating angular frequency.

[0041] In a preferred embodiment, the unit self-inductance L i and inter-unit mutual inductance M ij The local impedance matrix can be obtained through electromagnetic simulation or pre-calibration and stored in the central control module 3 or a storage unit connected to it in the form of a parameter matrix or lookup table. Since the geometry and relative positional relationship of the electromagnetic metasurface array 6 remain fixed after manufacturing, the local impedance matrix can be pre-established offline and called by the central control module 3 during operation to solve for the target total capacitance.

[0042] After calculating the target total capacitance of each unit within the local activator subarray based on the aforementioned analytical relationship, the central control module 3 converts the target total capacitance into a corresponding control voltage according to the pre-established capacitance-bias voltage mapping relationship. This control voltage is then output to the corresponding electromagnetic metasurface unit via the unit tuning module 7, thereby completing the local tuning state setting of each electromagnetic metasurface unit within the local activator subarray. Simultaneously, the central control module 3 applies a bias voltage corresponding to the low-response tuning state to the peripheral units outside the local activator subarray to maintain the low-response tuning state of the peripheral units, thereby suppressing leakage magnetic channels in non-target regions.

[0043] Example 5 In step S5, after each electromagnetic metasurface unit in the local activation subarray completes its local tuning state setting, the main transmitting coil 5 and the local activation subarray establish a locally highly coupled magnetic field region in the target area corresponding to the position of the receiving coil 9. Subsequently, the central control module 3 controls the power conversion module 2 to switch from low-power detection mode to power transmission mode, so that the main transmitting coil 5 and the local activation subarray jointly transmit electrical energy to the receiving coil 9.

[0044] As can be seen from the above implementation process, in the same wireless charging platform, the present invention uses the real part increment of the input impedance of the main transmitter to complete the position sensing of the receiving coil 9, and selects the local activator array according to the reconstructed two-dimensional position coordinates; by performing local weighting and local tuning state settings on the electromagnetic metasurface units in the local activator array, while making the electromagnetic metasurface units outside the local activator array in a low-response tuning state, the magnetic field participation of non-target areas is reduced; further, by combining the local activator array and its peripheral coupling relationship to construct a local impedance matrix and solve the target total capacitance, the target area forms a local high-coupling magnetic field region corresponding to the position of the receiving coil 9, thereby completing the continuous control process from position sensing, local magnetic field construction to power transmission.

[0045] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the invention. Without departing from the spirit of the invention, those skilled in the art can make corresponding adjustments or substitutions to the scale of the electromagnetic metasurface array 6, the unit geometric parameters, the operating frequency, the scale of the local activator array, the specific functional form of the continuous weighting distribution, the topology of the local tuning circuit, the solution method of the local impedance matrix, and the capacitor-bias voltage mapping relationship. All such adjustments or substitutions should fall within the protection scope defined by the claims of this invention.

Claims

1. A wireless charging method for unmanned aerial vehicles based on electromagnetic metasurfaces, characterized in that, The method is implemented based on a wireless charging platform, which includes a main transmitting coil, an electromagnetic metasurface array disposed above the main transmitting coil, an input impedance detection module, a central control module, and a unit tuning module. The method includes the following steps: S1: Control the wireless charging platform to enter a low-power detection mode, so that the main transmitting coil works at a fixed nominal frequency, and control the multiple electromagnetic metasurface units in the electromagnetic metasurface array to change their tuning states one by one; synchronously collect the real part of the input impedance of the main transmitting end in the corresponding scanning state, and compare it with the real part of the input impedance in the no-load baseline state to obtain the increment of the real part of the input impedance corresponding to each electromagnetic metasurface unit. S2: Determine the initial target region where the receiving coil of the UAV to be charged is located based on the two-dimensional distribution of the real part increment of the input impedance, and extract the real part increment of the input impedance of multiple electromagnetic metasurface units in the neighborhood of the initial target region to reconstruct the two-dimensional position coordinates of the center of the receiving coil in the global array coordinate system. S3: Select a local activation subarray in the global array based on the two-dimensional position coordinates, and update the physical unit number corresponding to the local activation subarray when the two-dimensional position coordinates cross the boundary of the current local activation subarray. S4: Locally weight and locally tune the electromagnetic metasurface units within the local activation subarray, and put the electromagnetic metasurface units outside the local activation subarray into a low-response tuning state to reduce the magnetic field participation in non-target regions. S5: The size and spatial coverage of the local activator array are constrained according to the physical size of the receiving coil to form a local high-coupling magnetic field region in the target area corresponding to the position of the receiving coil, and the power transmission mode is switched to transmit electrical energy to the receiving coil through the main transmitting coil and the local activator array.

2. The wireless charging method for unmanned aerial vehicles based on electromagnetic metasurfaces according to claim 1, characterized in that, In step S2, the two-dimensional position coordinates of the receiving coil center in the global array coordinate system are obtained based on the weighted distribution of the center coordinates of multiple electromagnetic metasurface units in the neighborhood of the initial target region and the corresponding real part increments of the input impedance; the local activation subarray is composed of M × N Composed of physical units M and N It is an integer not less than 2, and the size of the local activation subarray is not greater than the size of the global array; M and N The value of is determined based on the matching relationship between the size of the receiving coil and the side length of the electromagnetic metasurface unit.

3. The wireless charging method for unmanned aerial vehicles based on electromagnetic metasurfaces according to claim 1, characterized in that, In step S4, a continuous weighted distribution centered on the two-dimensional position coordinates and monotonically decreasing with increasing distance is constructed. Sampling is performed at the center of each electromagnetic metasurface unit within the local activation subarray to obtain the weighting coefficients of each electromagnetic metasurface unit. Based on the weighting coefficients and a preset reference current, the target current distribution of each electromagnetic metasurface unit is determined. Based on the coupling relationship between the local activation subarray and its connections with the main transmitting coil, receiving coil, and electromagnetic metasurface units outside the local activation subarray that are in a low-response tuning state, a local impedance matrix is ​​constructed. Combined with the target current distribution, the target total capacitance of each electromagnetic metasurface unit within the local activation subarray is calculated. According to a pre-established mapping relationship between capacitance and bias voltage, the target total capacitance is converted into the control voltage of the corresponding electromagnetic metasurface unit to complete the local tuning state setting of each electromagnetic metasurface unit within the local activation subarray.

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