Multi-layer multi-section asymmetric structure of unmanned aerial vehicle wireless charging system and optimization method

Abstract

This invention discloses a multi-layer, multi-segment asymmetric structure and optimization method for a wireless charging system for unmanned aerial vehicles (UAVs), belonging to the field of UAV wireless charging technology. The system includes a PWM rectifier, a high-frequency inverter, a transmitting coil, and a receiving coil. The transmitting coil's magnetic core adopts a multi-layer, multi-segment structure, with a core cross-sectional area satisfying a transmission ratio ≥ 1.5 times that of the receiving coil, and a magnetic shielding coverage area satisfying a transmission ratio ≥ 2 times that of the receiving coil. The transmitting coil uses fractional turns and gradient turn spacing. The receiving coil's magnetic shielding edge has an electromagnetic bandgap structure. Using the proposed structure, combined with a genetic algorithm, the parameters of the magnetic core and coil are optimized. When the receiving coil and transmitting coil of the UAV wireless charging system are offset, this invention can maintain a essentially unchanged mutual inductance between the receiving and transmitting coils, while reducing magnetic leakage, providing an effective method for fully automatic and efficient charging of UAVs.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology for unmanned aerial vehicles (UAVs), and in particular to a multi-layer, multi-segment asymmetric structure for a wireless charging system for UAVs and its optimization method. Background Technology

[0002] The charging system is one of the core components of a drone, and its performance directly affects the drone's safety and battery life. Currently, there are two main charging methods for drones: wired charging with contact points and automatic battery swapping. The main problems with wired charging with contact points are as follows:

[0003] The presence of charging contacts significantly reduces the safety of drone charging.

[0004] The large charging current poses a potential danger of leakage and electric shock, and is prone to generating contact sparks, making it unsafe.

[0005] The main problems with battery swapping are as follows:

[0006] (1) The battery swapping method has the problem of contact wear and high failure rate of mechanical devices, which greatly reduces the safety of UAV battery swapping;

[0007] (2) High construction costs and challenges in standardization and universal interfaces;

[0008] Wireless charging primarily transmits electrical energy through magnetic fields, eliminating the need for direct wire connections between the power supply and load, thus removing physical contacts. The load and power supply can intelligently connect via network commands, facilitating smart power supply. However, during wireless charging of drones, the uncertainty of the drone's stopping position inevitably causes misalignment between the transmitting and receiving coils. This alters the mutual inductance between the coils, leading to drastic voltage fluctuations and reduced efficiency at the output. Furthermore, misalignment increases magnetic leakage, compromising the safety and stability of the drone's wireless charging system.

[0009] Therefore, ensuring that the mutual inductance between coils remains as constant as possible, and on this basis, minimizing magnetic leakage and improving efficiency to achieve stable and efficient wireless charging is a challenging problem. Summary of the Invention

[0010] To address the above problems, this invention provides a multi-layer, multi-segment asymmetrical structure and optimization method for a drone wireless charging system. When the receiving coil and transmitting coil of the drone wireless charging system are offset, this invention can ensure that the mutual inductance between the receiving coil and the transmitting coil remains basically unchanged, while reducing magnetic leakage, thus providing an effective method for fully automatic and efficient charging of drones.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A multi-layer, multi-segment asymmetric structure for a drone wireless charging system includes:

[0013] PWM rectifier, high-frequency inverter, transmitting coil, transmitting-side compensation circuit, receiving coil, receiving-side compensation circuit, high-frequency rectifier and battery pack;

[0014] in:

[0015] The cross-sectional area of ​​the magnetic core of the transmitting coil Cross-sectional area of ​​the magnetic core of the receiving coil satisfy: Furthermore, the magnetic shielding coverage area of ​​the transmitting coil is ≥ twice the magnetic shielding coverage area of ​​the receiving coil;

[0016] The magnetic core of the transmitting coil has a multi-layer, multi-segment structure, with the number of layers... And number of segments The number of segments refers to the number of segments along the axial direction of the magnetic core, and each layer of magnetic core has an air gap of 0.5-2mm.

[0017] The magnetic core of the receiving coil has a single-layer or multi-layer structure;

[0018] When the receiving coil is offset by 1 cm in the lateral or longitudinal direction relative to the transmitting coil, the mutual inductance fluctuation rate is ≤5%, and the magnetic leakage at 9 cm in the vertical direction is ≤27 μT.

[0019] The beneficial effects of the above technical solution are as follows:

[0020] By increasing the cross-sectional area of ​​the transmitting coil core and the magnetic shielding coverage area, the magnetic field focusing capability is improved and the outward diffusion of the magnetic field is reduced. The multi-layer and multi-segment structure of the transmitting coil core and the interlayer air gap design can enhance the magnetic permeability, avoid core saturation, and reduce core heating. The mutual inductance fluctuation rate and magnetic leakage during offset are strictly controlled to ensure stable power transmission during drone charging and to comply with electromagnetic safety standards, avoiding interference to surrounding equipment and personnel.

[0021] As a further improvement to the above solution, the magnetic shield of the transmitting coil is located within 1-15mm below the coil, and the magnetic shield of the receiving coil is located within 3-10mm above the coil. Furthermore, the magnetic shield has a mesh structure with a mesh aperture diameter of... satisfy: ,in The length of the magnetic shield.

[0022] The beneficial effects of the above technical solution are as follows: placing the magnetic shield in a specific position can accurately block magnetic field leakage in the vertical direction of the coil, further improving the magnetic field confinement effect; the mesh structure of the magnetic shield reduces material usage and structural weight while ensuring shielding performance; the matching design of the mesh diameter and electromagnetic wavelength can avoid the shielding structure from having an adverse effect on magnetic field transmission, ensuring that the power transmission efficiency is not affected by the shielding device.

[0023] As a further improvement to the above scheme, the turns ratio of the transmitting coil to the receiving coil... satisfy: Furthermore, the transmitting coil adopts a fractional-turn structure, with the turn spacing increasing from the center outwards at a gradient of 5%-15%.

[0024] The beneficial effects of the above technical solution are as follows: the reasonable turns ratio design can match the different voltage requirements during the charging process of the drone, ensuring that the power conversion efficiency is at a high level; the fractional turns structure can flexibly adjust the coil inductance value, so that the coil and the compensation device can be better matched, reducing reactive power loss; the gradient increasing design of the turns spacing can balance the current distribution at each position of the coil, avoid excessive local current leading to coil overheating, and extend the service life of the coil.

[0025] As a further improvement to the above solution, the magnetic core is a cylindrical or rectangular three-dimensional helical structure; when it is cylindrical, the diameter of the magnetic core of the transmitting coil is... With the diameter of the receiving coil core satisfy: .

[0026] The beneficial effects of the above technical solution are as follows: the cylindrical and rectangular three-dimensional spiral magnetic cores can be adapted to the installation space of different drones, improving the versatility of the structure; the diameter ratio design of the cylindrical magnetic core can further optimize the magnetic field distribution, making the magnetic field more concentrated in the receiving coil area, reducing the loss of the magnetic field in the non-charging area, and improving the directionality and efficiency of power transmission.

[0027] As a further improvement to the above scheme, the magnetic core segment of the transmitting coil is provided with a high permeability pad with a permeability ≥5000H / m and a thickness of 0.2-1mm, which is used to suppress magnetic saturation.

[0028] The beneficial effects of the above technical solution are as follows: the high permeability pad can enhance the magnetic field conduction capability at the segmentation of the magnetic core, avoid magnetic field breakage caused by the segmentation structure, and ensure smooth magnetic circuit; the pad of a certain thickness can ensure magnetic permeability without increasing the overall volume and weight of the magnetic core, and can effectively suppress the magnetic core saturation phenomenon and maintain the stable electromagnetic performance of the coil.

[0029] As a further improvement to the above scheme, the mutual inductance Calculated using the following formula:

[0030] ;

[0031] Where Li represents the number of turns of the coil. Let be the magnetic flux density, Ip be the current in the transmitting coil, x3 and x5 be the coordinates of the two ends of the receiving coil along the X-axis, and y3 and y4 be the coordinates of the two ends of the receiving coil along the Y-axis. The X-axis coordinate is the side of the receiving coil closest to the transmitting coil (w is the width of a single-turn coil).

[0032] The beneficial effects of the above technical solution are as follows: by calculating various parameters and logic of mutual inductance, the mutual inductance value between the transmitting coil and the receiving coil can be accurately quantified, providing accurate data support for coil structure design and compensation device parameter adjustment; avoiding coil matching deviation caused by fuzzy mutual inductance calculation, ensuring stable power transmission efficiency, and facilitating subsequent optimization and verification of system performance.

[0033] As a further improvement to the above solution, the magnetic leakage Calculated using the following formula:

[0034] ;

[0035] in, , ;

[0036] Let Ip be the horizontal distance from the center of the transmitting coil to the measuring point, and let Ip be the current in the transmitting coil. The horizontal distance from the center of the receiving coil to the measuring point. The angle between the axes of the transmitting coil and the receiving coil ( (When the axes of the two coils coincide).

[0037] The beneficial effects of the above technical solution are as follows: the magnetic leakage calculation method can accurately predict the magnetic leakage intensity at different locations, which facilitates targeted optimization of the magnetic shielding structure during the system design stage and ensures that the magnetic leakage meets safety standards in all scenarios; considering parameters such as the included angle of the coil axis, the magnetic leakage calculation is more in line with actual use scenarios (such as the slight misalignment of the coil that may occur when the drone is charging), improving the practicality and reliability of the calculation results.

[0038] As a further improvement to the above scheme, each layer of the transmitting coil core is provided with a heat dissipation groove extending along the length of the core, with a groove width of 0.5-3mm, and the groove is filled with thermally conductive silicone grease (thermal conductivity not less than 3W / (m・K)).

[0039] The beneficial effects of the above technical solution are as follows: the heat dissipation grooves along the length of the magnetic core can increase the contact area between the magnetic core and the air, and accelerate heat dissipation; the filling of thermal grease can further improve the heat conduction efficiency, quickly dissipate the heat generated when the magnetic core is working, and avoid the magnetic core from degrading due to high temperature; the specific groove width and thermal conductivity design can ensure the heat dissipation effect without excessively weakening the structural strength and magnetic conductivity of the magnetic core.

[0040] As a further improvement to the above solution, the magnetic shielding edge of the receiving coil is provided with an electromagnetic bandgap structure, the bandgap period being... satisfy: ,in The system resonant frequency, is the dielectric constant of the shielding material.

[0041] The beneficial effects of the above technical solution are as follows: the electromagnetic bandgap structure can effectively suppress electromagnetic wave reflection and diffraction at the edge of the magnetic shield, reduce electromagnetic interference, and avoid affecting the precision electronic components inside the UAV; the matching design of the bandgap period and system parameters ensures that the electromagnetic bandgap structure plays the best interference suppression role at the system operating frequency, while not affecting the normal transmission of the magnetic field and ensuring charging efficiency.

[0042] As a further improvement to the above scheme, the vertical distance between the transmitting coil and the receiving coil is... satisfy: mm, and when When the change is ±2mm, the mutual inductance change rate is ≤5%, and this vertical distance is the reference spacing for measuring "magnetic leakage at 9cm in the vertical direction".

[0043] The beneficial effects of the above technical solution are as follows: by limiting the vertical distance range and controlling the mutual inductance change rate when the distance changes, it can adapt to the slight altitude deviation that may occur when the UAV lands, and ensure that the power transmission remains stable even if the distance fluctuates slightly; by using this distance as the magnetic leakage measurement benchmark, the magnetic leakage test results are more accurate and referential, which facilitates standardized production and quality control.

[0044] As a further improvement to the above solution, the following steps are included:

[0045] S1. Establish a three-dimensional model of the transmitting-receiving coil, including the number of magnetic core layers. , number of segments The core cross-sectional area, magnetic shielding coverage area, coil turns ratio, vertical distance h, and other core parameters define the number of core layers. , number of segments Let be a variable, and the constraint condition be... , ;

[0046] S2. With mutual inductance fluctuation rate ≤5% and magnetic leakage ≤27μT as the dual objective functions, a genetic algorithm is used for iterative optimization. The population size is ≥50, the crossover probability is 0.8, and the mutation probability is 0.1.

[0047] S3, calculate mutual inductance, mutual inductance volatility, and magnetic leakage;

[0048] S4, Determine if the mutual inductance, mutual inductance fluctuation rate, and magnetic leakage meet the requirements: Compare the current mutual inductance, mutual inductance fluctuation rate, and magnetic leakage with the set values. If the requirements are met, save the parameters that meet the conditions; if the requirements are not met, further adjust the parameters of the coil, magnetic core, and magnetic shielding.

[0049] S5. Repeat steps S3 to S5 until all parameters reach their upper limits.

[0050] S6. Output the solution set that satisfies the conditions, and select the solution with the lightest core weight as the optimal parameter combination.

[0051] The beneficial effects of the above technical solution are as follows: by integrating the core parameters of the system through a three-dimensional model, the working state of the coil can be fully simulated, avoiding the overall performance imbalance caused by the optimization of a single parameter; the dual objective function design ensures that the optimization results simultaneously meet the requirements of stable power transmission and electromagnetic safety; the parameter setting of the genetic algorithm takes into account both optimization efficiency and result diversity, and the Pareto front solution set and core weight are selected in a priority manner, which can reduce the system manufacturing cost and weight while ensuring performance, and is more suitable for the lightweight requirements of UAVs.

[0052] As a further improvement to the above scheme, the fitness function of the genetic algorithm is:

[0053] ;

[0054] in:

[0055] 1. The fitness value is used to quantify the overall performance of a combination of parameters. The smaller the value, the better the parameter combination;

[0056] 2. The weighting coefficient for the mutual inductance volatility term, with a value range of [value missing]. This is used to adjust the importance of charging stability in the optimization objective;

[0057] 3. The maximum change in mutual inductance when the receiving coil is offset by 1 cm in the lateral or longitudinal direction relative to the transmitting coil (unit: That is, the difference between the mutual inductance value after offset and the mutual inductance value without offset;

[0058] 4. The rated mutual inductance value when the transmitting coil and receiving coil are not misaligned (unit: The formula for calculating mutual inductance is derived from this formula.

[0059] 5. The weighting coefficient for the magnetic leakage term, with a value range of [value missing]. And satisfy , This is used to adjust the importance of electromagnetic safety in the optimization objective;

[0060] 6. The actual magnetic leakage magnetic induction intensity generated at key locations in the drone wireless charging system (unit: The specific definition is as follows:

[0061] Measurement locations: Corresponding to the magnetic leakage control scenario, including a vertical distance of 9cm from the transmitting coil (ground personnel safety protection area) and a horizontal or vertical offset of 12cm from the transmitting coil (surrounding electronic equipment anti-interference area).

[0062] Numerical source: The theoretical value was derived from the magnetic leakage calculation formula, and the measured value was obtained after correction by actual test.

[0063] 7. Magnetic leakage safety limit (unit: The value is 27. This ensures that the system does not cause electromagnetic hazards to personnel or surrounding equipment during operation.

[0064] The beneficial effects of the above technical solution are as follows:

[0065] The fitness function clearly defines the calculation scenario for mutual inductance changes and the definition of rated mutual inductance, making the function calculation more accurate and able to accurately reflect the system's performance under offset conditions. The setting of weight coefficients highlights the importance of mutual inductance stability while taking into account magnetic leakage control, ensuring that the optimization results are more in line with actual charging needs. Through the quantified fitness function, the iteration direction of the genetic algorithm is made clearer, improving optimization efficiency and the reliability of the optimal parameter combination.

[0066] Compared with the prior art, the overall beneficial effects of the present invention are as follows:

[0067] Existing wireless charging technologies for drones generally suffer from problems such as large magnetic field leakage, unstable power transmission during deflection, easy saturation and overheating of the magnetic core, and lack of precise methods for system optimization.

[0068] This invention achieves three core breakthroughs through a multi-layer, multi-segment asymmetric magnetic core structure, precise magnetic shielding and coil parameter design, scientific calculation methods for mutual inductance and magnetic leakage, and optimization methods that balance performance and lightweight design:

[0069] First, it significantly improves the magnetic field focusing capability, and controls the magnetic leakage to below 27μT, which is far lower than the electromagnetic interference level of existing technologies.

[0070] Secondly, the mutual inductance fluctuation rate does not exceed 5% within a 1cm offset range, which solves the problem of unstable charging caused by drone landing deviation;

[0071] Third, by combining structural and algorithmic optimization, the weight of the magnetic core is reduced while maintaining performance, thus meeting the lightweight requirements of drones. Overall, this invention outperforms existing technologies in terms of power transmission efficiency, electromagnetic safety, environmental adaptability, and cost control, providing a more reliable technical solution for the large-scale application of wireless charging for drones. Attached Figure Description

[0072] Figure 1 A schematic diagram of a wireless charging system for drones.

[0073] Figure 2 This is a schematic diagram of a multi-layered, multi-segmented, asymmetrical structure for a wireless charging system.

[0074] Figure 3 This is a schematic diagram of the magnetic core structure of a wireless charging system.

[0075] Figure 4 This is a schematic diagram of the front structure of a wireless charging system.

[0076] Figure 5 This is a side view of the wireless charging system.

[0077] Figure 6 A flowchart of the preferred method for wireless charging systems.

[0078] In the diagram: 11. Transmitting coil; 12. Transmitting magnetic shielding aluminum plate; 13. Three-layer, three-segment transmitting magnetic core; 21. Receiving coil; 22. Receiving magnetic shielding aluminum plate; 23. Three-layer, three-segment receiving magnetic core; 131. First segment transmitting magnetic core; 132. Second segment transmitting magnetic core; 133. Third segment transmitting magnetic core; 134. First layer transmitting magnetic core; 135. Second layer transmitting magnetic core; 136. Third layer transmitting magnetic core; 231. First segment receiving magnetic core; 232. Second segment receiving magnetic core; 233. Third segment receiving magnetic core; 234. First layer receiving magnetic core; 235. Second layer receiving magnetic core; 236. Third layer receiving magnetic core. Detailed Implementation

[0079] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0080] A multi-layer, multi-segment asymmetric structure and optimization method for a drone wireless charging system, comprising a PWM rectifier, a high-frequency inverter, a transmitting coil 11, a transmitting-side compensation circuit, a receiving coil 21, a receiving-side compensation circuit, a high-frequency rectifier, and a battery pack.

[0081] On the one hand, the magnetic cores of the transmitting coil 11 and the receiving coil 21 adopt an asymmetrical structure, that is, the transmitting coil 11 is equipped with a large magnetic core and the receiving coil 21 is equipped with a small magnetic core (the cross-sectional area of ​​the magnetic core of the transmitting coil 11 is not less than 1.5 times the cross-sectional area of ​​the magnetic core of the receiving coil 21, and the magnetic shielding coverage area of ​​the transmitting coil 11 is not less than 2 times the magnetic shielding coverage area of ​​the receiving coil 21), ensuring that the transmitting coil 11 and the receiving coil 21 have strong anti-offset capability. Even if there is a large offset between the two (1 cm in the lateral or longitudinal direction), the mutual inductance can still remain basically unchanged (the mutual inductance fluctuation rate does not exceed 5%), so as to achieve stable and safe operation of the system.

[0082] On the other hand, the magnetic cores and magnetic shielding of the transmitting coil 11 and the receiving coil 21 also adopt an asymmetric multi-layer, multi-segment structure (the magnetic core of the transmitting coil 11 has a multi-layer, multi-segment structure with no less than 3 layers and no less than 2 segments, with the segments divided along the magnetic core axis, and an air gap of 0.5-2mm between each layer of magnetic core). This can simultaneously reduce the magnetic leakage of the system (magnetic leakage at 9cm in the vertical direction does not exceed 27μT) and weight, thereby improving the drone's endurance. Through the proposed parameter calculation and optimization method, the optimal parameters of the coil, magnetic core, and magnetic shielding are obtained, achieving the goal of high-performance wireless charging.

[0083] Specifically, such as Figure 1 The diagram shows a framework of a wireless charging system for a drone, including a PWM rectifier, a high-frequency inverter, a transmitting coil 11, a transmitting-side compensation circuit, a receiving coil 21, a receiving-side compensation circuit, a high-frequency rectifier, and a battery pack.

[0084] Specific multi-layered, multi-segmented asymmetrical structures, such as Figures 2-5 As shown, it includes a transmitting coil 11, a magnetic core of the transmitting coil, a magnetic shield of the transmitting coil, a receiving coil 21, a magnetic core of the receiving coil, and a magnetic shield of the receiving coil.

[0085] The transmitting coil 11 is wound around the transmitting coil core. Depending on the actual scenario, the transmitting coil core and the receiving coil core can be cylindrical or cuboid. If it is cylindrical, the ratio of the diameter of the transmitting coil core 11 to the diameter of the receiving coil core 21 is not less than 1.8. In this embodiment, a cuboid structure is adopted.

[0086] To reduce magnetic saturation, the magnetic cores of the transmitting coil 11 and the receiving coil 21 adopt a multi-layer, multi-segment structure. In this embodiment, the magnetic core of the transmitting coil 11 adopts a three-layer, three-segment transmitting magnetic core 13, and the magnetic core of the receiving coil 21 adopts a three-layer, three-segment receiving magnetic core 23. The magnetic shielding of the transmitting coil 11 is a receiving magnetic shielding aluminum plate 22; the magnetic shielding of the transmitting coil 11 is a transmitting magnetic shielding aluminum plate 12.

[0087] The three-layer, three-segment transmitting magnetic core 13 is composed of a first transmitting magnetic core 131, a second transmitting magnetic core 132, and a third transmitting magnetic core 133 arranged side by side; each segment of the transmitting magnetic core is composed of a first layer of transmitting magnetic core 134, a second layer of transmitting magnetic core 135, and a third layer of transmitting magnetic core 136 stacked together.

[0088] The three-layer, three-segment receiving magnetic core 23 is composed of a first segment receiving magnetic core 231, a second segment receiving magnetic core 232, and a third segment receiving magnetic core 233 arranged side by side. Each segment receiving magnetic core is composed of a first layer receiving magnetic core 234, a second layer receiving magnetic core 235, and a third layer receiving magnetic core 236 stacked together.

[0089] The magnetic core has a certain air gap, which improves the system's anti-magnetic saturation capability. Furthermore, high-permeability pads (with a permeability of not less than 5000 H / m and a thickness of 0.2-1 mm) are provided at the segments of the transmitting coil 11 magnetic core, further suppressing magnetic saturation. Simultaneously, to improve the system's anti-offset capability, the size of the transmitting coil 11 magnetic core is larger than that of the receiving coil 21 magnetic core, and the size of the transmitting coil 11 is larger than that of the receiving coil 21. When the receiving coil 21 is offset, the coupling magnetic flux between the receiving coil 21 and the transmitting coil 11 remains relatively constant, ensuring that the mutual inductance between them remains essentially unchanged.

[0090] The magnetic shield of the transmitting coil 11 is located 5-15mm below the transmitting coil 11, and the magnetic shield of the receiving coil 21 is located 3-10mm above the receiving coil 21. The transmitting coil 11 and the receiving coil 21 use integer turns or fractional turns (the transmitting coil 11 preferably uses a fractional turn structure). The turns of the transmitting coil 11 and the receiving coil 21 are spaced evenly or unevenly (the turn spacing of the transmitting coil 11 increases from the center outwards, with an increase gradient of 5%-15%) to reduce magnetic leakage. To further reduce system magnetic leakage, magnetic shielding is added to the transmitting coil 11 to prevent electromagnetic interference to external electronic devices, and magnetic shielding is added to the receiving coil 21 to prevent electromagnetic interference to the UAV itself. The magnetic shielding has a mesh structure, with the mesh diameter not exceeding 1 / 10 of the electromagnetic wavelength corresponding to the system's operating frequency. Simultaneously, the edge of the magnetic shielding of the receiving coil 21 has an electromagnetic bandgap structure, and the bandgap period satisfies the formula... (where c is the speed of light,) The system resonant frequency, To further reduce electromagnetic interference, the dielectric constant of the shielding material is increased. In addition, each layer of the transmitting coil 11 magnetic core is provided with heat dissipation grooves extending along the length of the magnetic core. The grooves are 1-3mm wide and filled with thermally conductive silicone grease (thermal conductivity not less than 3W / (m・K)), which can effectively reduce the operating temperature of the magnetic core.

[0091] like Figure 6 As shown, to further ensure constant mutual inductance and reduce system magnetic leakage, the structural optimization method includes the following steps:

[0092] S1. Establish a model of transmitting coil 11 and receiving coil 21: It consists of a transmitting coil 11, the magnetic core and magnetic shield of the transmitting coil 11, and a receiving coil 21 with a smaller size than the transmitting coil 11, the magnetic core and magnetic shield of the receiving coil 21, etc. The receiving coil 21 is parallel to the transmitting coil 11. The model includes core parameters such as the number of magnetic core layers, the number of segments, the cross-sectional area of ​​the magnetic core, the coverage area of ​​the magnetic shield, the coil turns ratio, and the vertical distance h.

[0093] S2, set the main parameters: including the diameter of the copper wire, the resonant frequency, the distance between the transmitting coil 11 and the receiving coil 21 (the vertical distance h is in the range of 5-20mm, and the mutual inductance change rate does not exceed 3% when h changes by ±2mm, and h is the reference distance for measuring magnetic leakage at 9cm in the vertical direction), the magnetic core size of the transmitting coil 11 and the receiving coil 21, and the magnetic shielding size of the transmitting coil 11 and the receiving coil 21.

[0094] S3, Set specification constraints: Set constraints according to actual application and design requirements; including the range of length or diameter of transmitting coil 11, the range of width or diameter of transmitting coil 11, the range of number of turns of transmitting coil 11, the range of turn spacing of transmitting coil 11, the range of length or diameter of receiving coil 21, the range of width or diameter of receiving coil 21, the range of number of turns of receiving coil 21, the range of turn spacing of receiving coil 21, the range of variation in the length, width or diameter of magnetic core, the range of variation in the number of magnetic core layers (no less than 3 layers), the range of variation in the number of magnetic core segments (no less than 2 segments), the range of variation in the length, width or diameter of magnetic shield, the range of variation in the number of magnetic shield layers, the range of variation in the size of magnetic shield mesh (the mesh diameter does not exceed 1 / 10 of the electromagnetic wavelength corresponding to the system operating frequency), and the step size.

[0095] S4, calculate the mutual inductance and magnetic leakage between the transmitting coil 11 and the receiving coil 21;

[0096] Mutual inductance calculation: Calculated according to the formula for calculating the mutual inductance of a spiral coil:

[0097] ;

[0098] Where Li represents the number of turns of the receiving coil 21, Let be the magnetic flux density, Ip be the current in the transmitting coil 11, x3 and x5 be the coordinates of the two ends of the receiving coil 21 in the X-axis direction, and y3 and y4 be the coordinates of the two ends of the receiving coil 21 in the Y-axis direction. The X-axis coordinate of the receiving coil 21 on the side closest to the transmitting coil 11 (w is the width of a single-turn coil).

[0099] Magnetic leakage calculation: Calculated according to the formula for calculating magnetic leakage of a helical coil.

[0100] ;

[0101] in: , ;

[0102] p1 is the horizontal distance from the center of the transmitting coil 11 to the measuring point, p2 is the horizontal distance from the center of the receiving coil 21 to the measuring point, and ψ is the angle between the axes of the transmitting coil 11 and the receiving coil 21 (when ψ=0°, the axes of the two coils coincide).

[0103] S5, set mutual inductance, mutual inductance fluctuation rate, and magnetic leakage requirements: set mutual inductance ≥ 3.5 μH; mutual inductance fluctuation rate ≤ 5% when offset laterally by 1 cm; mutual inductance fluctuation rate ≤ 5% when offset longitudinally by 1 cm; magnetic leakage below 27 μT at 9 cm vertically; and magnetic leakage below 27 μT at both 12 cm lateral and longitudinal offsets.

[0104] S6, calculate mutual inductance, mutual inductance fluctuation rate and magnetic leakage; (the calculation method is the same as S4, based on the above calculation formulas for mutual inductance and magnetic leakage).

[0105] S7, Determine if mutual inductance, mutual inductance fluctuation rate and magnetic leakage meet the requirements: Compare the current mutual inductance, mutual inductance fluctuation rate and magnetic leakage with the set values. If the requirements are met, save the parameters that meet the conditions; if the requirements are not met, further adjust the parameters of the coil, magnetic core and magnetic shield.

[0106] S8. Repeat steps S3 to S7 until all parameters reach their upper limits. During optimization, a genetic algorithm is used for iterative optimization. The population size is no less than 50, the crossover probability is 0.8, and the mutation probability is 0.1. The dual objective functions are mutual inductance fluctuation rate ≤ 5% and magnetic leakage ≤ 27 μT, and the fitness function is... (Where ΔM is the maximum change in mutual inductance when the receiving coil 21 is offset by 1 cm in the lateral or longitudinal direction relative to the transmitting coil 11, and M0 is the rated mutual inductance when the two coils are not offset.) The weighting coefficients α and β satisfy 0.4≤α≤0.8 and 0.2≤β≤0.6, and α+β=1, and the value of α is not less than β, prioritizing the stability of mutual inductance); finally, the Pareto front solution set is output, and the solution with the lightest core weight is selected as the optimal parameter combination.

[0107] The following is a specific embodiment that details the implementation process of the entire technical solution:

[0108] 1. System Composition:

[0109] This system includes a PWM rectifier, a high-frequency inverter, a transmitting coil 11, a transmitting-side compensation circuit, a receiving coil 21, a receiving-side compensation circuit, a high-frequency rectifier, and a battery pack. By optimizing the magnetic shielding, core, and coil parameters of the transmitting coil 11 and the receiving coil 21, the system maintains a relatively constant mutual inductance between the coils (mutual inductance fluctuation rate not exceeding 5%) when the coils are offset (lateral or longitudinal offset of 1cm), reducing system magnetic leakage (magnetic leakage at a vertical distance of 9cm not exceeding 27μT), thus achieving safe and high-performance charging for the drone wireless charging system.

[0110] 2. Parameter settings:

[0111] Copper wire diameter: 2.5mm;

[0112] Resonant frequency: 85kHz;

[0113] The initial distance between the transmitting coil 11 and the receiving coil 21 is 1cm (within the range of 5-20mm, and the mutual inductance change rate does not exceed 3% when the distance changes by ±2mm; this distance is the reference spacing for magnetic leakage measurement at 9cm in the vertical direction).

[0114] 3. Implementation of structure and parameter optimization algorithms:

[0115] S1. Establish a model of transmitting coil 11 and receiving coil 21: consisting of a transmitting coil 11, the magnetic core and magnetic shield of the transmitting coil 11, and a receiving coil 21 smaller than the transmitting coil 11, the magnetic core and magnetic shield of the receiving coil 21, etc. The receiving coil 21 is parallel to the transmitting coil 11. The model includes core parameters such as the number of magnetic core layers (not less than 3 layers), the number of segments (not less than 2 segments), the cross-sectional area of ​​the magnetic core (the cross-sectional area of ​​the magnetic core of the transmitting coil 11 is not less than 1.5 times the cross-sectional area of ​​the magnetic core of the receiving coil 21), the magnetic shielding coverage area (the magnetic shielding coverage area of ​​the transmitting coil 11 is not less than 2 times the magnetic shielding coverage area of ​​the receiving coil 21), the coil turns ratio (1.2-2.5), and the vertical distance h (10mm).

[0116] S2, set the main parameters: including the diameter of the copper wire, the resonant frequency, the distance between the transmitting coil 11 and the receiving coil 21 (10mm), the core size of the transmitting coil 11 and the receiving coil 21, and the magnetic shielding size of the transmitting coil 11 and the receiving coil 21 (the magnetic shielding is mesh, and the mesh diameter does not exceed 1 / 10 of the electromagnetic wavelength corresponding to 85kHz. The electromagnetic wavelength corresponding to 85kHz is approximately 3529m, so the mesh diameter does not exceed 352.9m. In practice, it is taken as 20mm).

[0117] S3, Set specification constraints: Set constraints according to actual application and design requirements; including the range of length or diameter of transmitting coil 11, the range of width or diameter of transmitting coil 11, the range of number of turns of transmitting coil 11, the range of turn spacing of transmitting coil 11 (increasing from the center outwards, with an increment of 5%-15%), the range of length or diameter of receiving coil 21, the range of width or diameter of receiving coil 21, the range of number of turns of receiving coil 21, the range of turn spacing of receiving coil 21, the range of variation in the length, width or diameter of the magnetic core, the range of variation in the number of magnetic core layers (1-4, including constraints of at least 3 layers), the range of variation in the number of magnetic core segments (1-3, including constraints of at least 2 segments), the range of variation in the length, width or diameter of the magnetic shield, the range of variation in the number of magnetic shield layers, the range of variation in the size of the magnetic shield mesh (not exceeding 352.9m), and the step size;

[0118] Based on practical applications and design requirements, the optimization range of the coil is set as shown in Table 1 below.

[0119] Table 1 Parameter Optimization Range:

[0120] Length of transmitting magnetic core / mm 5~15 Emitter core width / mm 2-6 Receiver core length / mm 3~10 Receiver core width / mm 2~5 Length of transmitting magnetic core / cm 3~10 Receiver core length / cm 3~8 Number of turns of transmitting coil 10~20 Number of turns of receiving coil 8~16 Number of core segments 1-3 Number of core layers 1-4

[0121] S4, calculate the mutual inductance and magnetic leakage between the transmitting coil 11 and the receiving coil 21;

[0122] 1. Mutual Inductance Calculation: The following mutual inductance calculation formula is used, combined with electromagnetic simulation (ANSYS Maxwell) to obtain magnetic field distribution data. The specific calculation process is as follows:

[0123] Mutual induction Calculated using the following formula:

[0124] ;

[0125] Where Li represents the number of turns of the coil. Let be the magnetic flux density, Ip be the current in the transmitting coil, x3 and x5 be the coordinates of the two ends of the receiving coil along the X-axis, and y3 and y4 be the coordinates of the two ends of the receiving coil along the Y-axis. is the X-axis coordinate of the receiving coil near the transmitting coil, and w is the width of a single-turn coil.

[0126] Core parameter: Number of turns of the receiving coil Turns (fitting the optimal turns ratio of 15:12, matching actual assembly parameters) Transmitter coil current Effective area of ​​a single turn of the receiving coil (Based on the dimensions of the transmitting magnetic core (10*4mm) and the receiving magnetic core (8*3mm), after deducting inter-turn gaps and edge losses, this represents the reasonable effective area for adapting to multi-layer magnetic cores.) Average magnetic flux density in the central region of the coil. (After stacking multiple layers and segments of magnetic cores with high-permeability pads, the magnetic field coupling strength is significantly improved, which is consistent with the actual magnetic field strength range of wireless charging coils.)

[0127] single-turn magnetic flux ;

[0128] This system adopts a multi-layer, multi-segment magnetic core structure, coupled with high-permeability segmented pads, which significantly improves magnetic coupling efficiency. The actual coupling coefficient is 0.49 (within the reasonable range of 0.4-0.6 for the optimized wireless charging system, suitable for the magnetic core and coil design of this scheme). The total mutual inductance is calculated as follows:

[0129] ;

[0130] A minor engineering correction was made, taking into account the distributed loss between coil turns and the slight magnetic reluctance of the air gap in the magnetic core, to finally determine the rated mutual inductance without offset. (The correction margin is only 0.5%, which is far below the conventional error range of engineering calculations, and the calculation accuracy is higher), meeting the design requirement of mutual inductance ≥3.5μH.

[0131] 2. Magnetic leakage calculation: The following magnetic leakage calculation formula is used, combined with the principle of magnetic field superposition in the axial direction. The specific calculation process is as follows:

[0132] Magnetic leakage Calculated using the following formula:

[0133] ;

[0134] in, , ;

[0135] Let Ip be the horizontal distance from the center of the transmitting coil to the measuring point, and let Ip be the current in the transmitting coil. The horizontal distance from the center of the receiving coil to the measuring point. The angle between the axes of the transmitting coil and the receiving coil.

[0136] Key parameter: Horizontal distance from the center of the transmitting coil to the measuring point Horizontal distance from the center of the receiving coil to the measuring point The included angle of the coil axis (The axes of the two coils coincide), the current in the transmitting coil. Vacuum permeability The measurement point is located directly above the coil axis (Y-axis coordinate). (aligned with the center of the coil); coefficient calculation:

[0137] ;

[0138] and Calculation (considering the ratio of coil size to measurement distance):

[0139] ;

[0140] Substitution , , ,have to:

[0141] ;

[0142] Similarly ;

[0143] Magnetic leakage calculation (with 30dB correction for mesh magnetic shielding efficiency):

[0144] ;

[0145] Substituting into numerical calculations yields the theoretical magnetic leakage. , compared with actual test values Consistency, satisfaction Safety requirements.

[0146] S5, set mutual inductance, mutual inductance fluctuation rate, and magnetic leakage requirements: as set above, mutual inductance ≥ 3.5 μH; mutual inductance fluctuation rate ≤ 5% when the lateral offset is 1 cm, mutual inductance fluctuation rate ≤ 5% when the longitudinal offset is 1 cm; magnetic leakage at 9 cm vertically and at 12 cm lateral / longitudinal offset is ≤ 27 μT.

[0147] S6 calculates mutual inductance, mutual inductance volatility, and magnetic leakage.

[0148] When the lateral offset is 1cm: the mutual inductance after offset is obtained by combining the mutual inductance calculation formula with simulation correction. Mutual inductance volatility:

[0149] ;

[0150] Meets offset stability requirements;

[0151] When the longitudinal offset is 1cm: Similarly, the mutual inductance after the offset is obtained. Mutual inductance volatility:

[0152] ;

[0153] Meets the set standards;

[0154] Magnetic leakage test: The actual measured value at 9cm vertically is 21μT, at 12cm horizontally offset is 23μT, and at 12cm vertically offset is 25μT, all of which are ≤27μT, meeting the magnetic safety requirements.

[0155] S7. Determine if the parameters meet the requirements: The current parameter combination (transmitting magnetic core length 10mm, width 4mm, receiving magnetic core length 8mm, width 3mm, transmitting coil 11 turns 15 turns, receiving coil 21 turns 12 turns, magnetic core layer 3 layers, segment 2 segments, magnetic shielding mesh diameter 20mm) meets all constraints (mutual inductance, offset fluctuation rate, and magnetic leakage all meet the standards), and stores this set of parameters in the valid parameter library.

[0156] S8, Repeated Optimization and Optimal Parameter Selection:

[0157] Following the S3–S7 process described above, traverse the parameter range while simultaneously initiating iterative optimization using a genetic algorithm—setting the population size to 50, crossover probability to 0.8, and mutation probability to 0.1, with "mutual inductance volatility ≤ 5%" and "magnetic leakage ≤ 27 μT" as the dual objective functions, and substituting them into the fitness function:

[0158]

[0159] ( , ,satisfy , and , Prioritize ensuring the stability of mutual inductance during offset).

[0160] After 50 iterations, the Pareto front solution set is output, and three sets of core effective parameter combinations are selected, as shown in Table 2 below:

[0161] Table 2. Effective parameter combinations and performance indicators of the Pareto front:

[0162] 1 10×4 8×3 15:12 3×2 78 4.0% 21 2 12×5 9×4 18:14 4×2 95 3.5% 19 3 8×3 7×2 12:10 3×3 82 4.8% 23

[0163] Based on the selection principle of "lightest magnetic core weight", the parameter combination of number 1 (magnetic core weight 78g) is the optimal solution, and subsequent system assembly and testing are all based on this set of parameters.

[0164] 4. System performance verification:

[0165] The drone wireless charging system was assembled with optimal parameters. An industrial inspection drone (2-hour flight time, 6000mAh battery capacity) was selected as the test subject and subjected to 100 cycle charging tests to verify the core performance indicators. The test results are shown in Table 3 below:

[0166] Table 3 Summary of System Performance Test Results:

[0167] System charging efficiency ≥85% 87.5% 100% yes Lateral offset of 1cm stability Mutual inductance fluctuation rate ≤ 5%, no power outage 4.0%, continuous charging without interruption 100% yes Longitudinal offset of 1cm stability Mutual inductance fluctuation rate ≤25%, no power outage 20%, continuous charging without interruption 100% yes Vertical distance adaptability (h=8-12mm) Mutual inductance change rate ≤ 3% When h=8mm, M=225μH; when h=12mm, M=219μH; the rate of change is approximately 2.7%. 100% yes Magnetic leakage safety ≤27μT at a vertical distance of 9cm 21μT 100% yes Core operating temperature After continuous charging for 2 hours, the temperature will be ≤65℃. 58℃ 100% yes Impact of drone battery life System additional weight ≤100g The total weight of the magnetic core, coil, and shield is 92g. 100% yes

[0168] 5. Conclusion of the Example:

[0169] This embodiment achieves high-performance operation of the drone wireless charging system through three core steps: "asymmetric multi-layer and multi-segment magnetic core structure design," "precise parameter calculation," and "genetic algorithm optimization." The specific conclusions are as follows:

[0170] 1. Structural design: The asymmetrical dimensions of the transmitting coil 11 magnetic core (3 layers, 2 segments) and the receiving coil 21 magnetic core (transmitting core 10×4mm, receiving core 8×3mm), combined with the mesh magnetic shield (mesh size 20mm) and heat dissipation grooves (2mm wide, filled with 3.5W / (m・K) thermal grease), ensure both the anti-offset capability (lateral offset fluctuation rate of 4.0% per 1cm) and control of magnetic leakage (21μT) and temperature (58℃).

[0171] 2. Parameter optimization: By accurately applying the calculation formulas for mutual inductance and magnetic leakage, and combining them with a genetic algorithm (α=0.6, β=0.4), the lightest magnetic core parameter combination (78g) was selected. While meeting performance requirements, the system weight was reduced to the minimum, which is suitable for the lightweight requirements of drones.

[0172] 3. Practical application level: The pass rate of 100% in 100-cycle tests and the charging efficiency of 87.5% prove that the solution can stably meet the wireless charging needs of industrial inspection drones and provide reliable technical support for improving the drone's endurance.

[0173] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A multi-layer, multi-segment asymmetrical structure for a drone wireless charging system, characterized in that, include: PWM rectifier, high-frequency inverter, transmitting coil, transmitting-side compensation circuit, receiving coil, receiving-side compensation circuit, high-frequency rectifier and battery pack; in: The cross-sectional area of ​​the magnetic core of the transmitting coil Cross-sectional area of ​​the magnetic core of the receiving coil satisfy: Furthermore, the magnetic shielding coverage area of ​​the transmitting coil is ≥ twice the magnetic shielding coverage area of ​​the receiving coil; The magnetic core of the transmitting coil has a multi-layer, multi-segment structure, with the number of layers... And number of segments The number of segments refers to the number of segments along the axial direction of the magnetic core, and each layer of magnetic core has an air gap of 0.5-2mm. The magnetic core of the receiving coil has a single-layer or multi-layer, multi-segment structure; When the receiving coil is offset by 1 cm in the lateral or longitudinal direction relative to the transmitting coil, the mutual inductance fluctuation rate is ≤5%, and the magnetic leakage at 9 cm in the vertical direction is ≤27 μT.

2. The structure according to claim 1, characterized in that, The magnetic shield of the transmitting coil is located 1-15mm below the coil, and the magnetic shield of the receiving coil is located 1-5mm above the coil. The magnetic shield has a mesh structure with a mesh diameter of [missing information]. satisfy: ,in The length of the magnetic shield.

3. The structure according to claim 1, characterized in that, The turns ratio of the transmitting coil to the receiving coil satisfy: Furthermore, the transmitting coil adopts a fractional-turn structure, with the turn spacing increasing from the center outwards at a gradient of 5%-15%.

4. The structure according to claim 1, characterized in that, The magnetic core has a cylindrical or rectangular three-dimensional helical structure; when it is cylindrical, the diameter of the magnetic core of the transmitting coil is... With the diameter of the receiving coil core satisfy: .

5. The structure according to claim 1, characterized in that, The mutual inductance Calculated using the following formula:

6. Wherein, Li represents the number of turns of the coil. Let be the magnetic flux density, Ip be the current in the transmitting coil, x3 and x5 be the coordinates of the two ends of the receiving coil along the X-axis, and y3 and y4 be the coordinates of the two ends of the receiving coil along the Y-axis. is the X-axis coordinate of the receiving coil near the transmitting coil, and w is the width of a single-turn coil.

7. The structure according to claim 1, characterized in that, The magnetic leakage Calculated using the following formula: ;in, , ; Let Ip be the horizontal distance from the center of the transmitting coil to the measuring point, and let Ip be the current in the transmitting coil. The horizontal distance from the center of the receiving coil to the measuring point. The angle between the axes of the transmitting coil and the receiving coil.

8. The structure according to claim 1, characterized in that, The transmitting coil has heat dissipation grooves extending along the length of the core between each layer of the core. The grooves are 0.5-3mm wide and filled with thermally conductive silicone grease with a thermal conductivity ≥3W / (m·K).

9. The structure according to claim 1, characterized in that, The vertical distance between the transmitting coil and the receiving coil satisfy: mm, and when When the change is ±2mm, the mutual inductance change rate is ≤5%.

10. An optimization method for a multi-layer, multi-segment asymmetric structure of a drone wireless charging system, applied to the structure described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Establish a three-dimensional model of the transmitting-receiving coil, including the number of magnetic core layers. , number of segments The core cross-sectional area, magnetic shielding coverage area, coil turns ratio, vertical distance h, and other core parameters define the number of core layers. , number of segments Let be a variable, and the constraint condition be... , ; S2. With mutual inductance fluctuation rate ≤5% and magnetic leakage ≤27μT as the dual objective functions, a genetic algorithm is used for iterative optimization. The population size is ≥50, the crossover probability is 0.8, and the mutation probability is 0.

1. S3, calculate mutual inductance, mutual inductance volatility, and magnetic leakage; S4, Determine if the mutual inductance, mutual inductance fluctuation rate, and magnetic leakage meet the requirements: Compare the current mutual inductance, mutual inductance fluctuation rate, and magnetic leakage with the set values. If the requirements are met, save the parameters that meet the conditions; if the requirements are not met, further adjust the parameters of the coil, magnetic core, and magnetic shielding. S5, repeat steps S3 to S5 above until all parameters reach their upper limits; S6. Output the solution set that satisfies the conditions, and select the solution with the lightest core weight as the optimal parameter combination.

11. The method according to claim 9, characterized in that, The fitness function of the genetic algorithm is: ； in, This represents the maximum change in mutual inductance when the receiving coil is offset by 1 cm from the transmitting coil in either the lateral or longitudinal direction. This is the rated mutual inductance when the two coils are not offset. Weighting coefficients , satisfy , and ,and The value of is not less than .

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