Lightweight common-form anti-drift coupling mechanism for UAV and its parameter design method

Abstract

The invention discloses a lightweight common-form anti-offset coupling mechanism of an unmanned aerial vehicle and a parameter design method thereof, belonging to the technical field of wireless charging, and is intended to solve the problem that when the unmanned aerial vehicle lands, the landing position and direction are random, resulting in rotation offset affecting charging. The invention comprises a primary transmitting device and a secondary receiving device, wherein the primary transmitting device comprises a first transmitting coil and a second transmitting coil, wherein the first transmitting coil and the second transmitting coil are respectively vertical spiral tube coils of different sizes, the inner magnetic field of the first transmitting coil and the outer magnetic field of the second transmitting coil are superimposed on each other, and a superimposed magnetic field is generated between the two vertical spiral tube coils of different sizes, so that a receiving coil located above the two transmitting coils can receive the magnetic field, thereby ensuring that the power and efficiency of wireless power transmission will not be affected regardless of the relative rotation angle of the unmanned aerial vehicle during landing.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and more specifically, particularly relates to a lightweight common-type anti-drift coupling mechanism of an unmanned aerial vehicle and a parameter design method thereof. Background Art

[0002] In recent years, the drone market has been extremely hot. Short battery life is a common problem of current drones. Drones need to replace batteries or recharge after flying continuously for 20-30 minutes. The ability of drones to autonomously perform work tasks is severely limited by their battery life.

[0003] There are three main solutions to the problem of drone endurance. The first is to equip drones with new energy generation equipment such as solar cells, so that drones can automatically replenish electricity. The second is to develop batteries with higher energy density, so that drones can carry more electricity at a time. The third is to develop automatic charging technology that does not require human assistance, so that drones can replenish electricity in the middle of a cruise and extend the cruise range. Wireless charging technology, as an emerging charging technology, can charge devices without physical direct contact. The charging process does not require human participation and can be effectively used for fully automatic charging of drones.

[0004] In the prior art, in order to realize wireless charging of drones, modifications are usually made to the existing drone frame structure. Commonly used airborne secondary coils mostly use single planar coils. In order to ensure its charging performance, the coil area is large. When directly used in various existing drone models, it is difficult to directly adapt to the existing drone frame structure, and it is easy to increase the flight resistance of the drone, affecting flight safety.

[0005] In addition, due to the complex automatic / manual operation mode and environment of the drone and the limited algorithm accuracy, the landing offset of the drone should also be considered, including the randomness of the landing position and direction. The existing drone wireless charging system has a high tolerance for the landing horizontal position, but most of them have difficulty in dealing with the rotation offset problem. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a lightweight common anti-offset coupling mechanism for a UAV and a parameter design method thereof, which can reduce the impact of the wireless charging system on the structure of the UAV while having a certain degree of tolerance for horizontal offset and greatly improve the tolerance for rotation offset during landing of the UAV, so as to solve the technical problem in the prior art that when the UAV lands, the landing position and direction are random, resulting in rotation offset affecting charging.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a lightweight common-type anti-offset coupling mechanism for an unmanned aerial vehicle, including a primary transmitting device and a secondary receiving device, the key of which is that the primary transmitting device includes a first transmitting coil and a second transmitting coil, the first transmitting coil and the second transmitting coil are vertical spiral tube coils of different sizes, the second transmitting coil is located inside the first transmitting coil and is coaxial with the first transmitting coil, a magnetic field superposition area is formed between the inner side of the first transmitting coil and the outer side of the second transmitting coil, and when the unmanned aerial vehicle is docked for charging, the secondary receiving device is located directly above the magnetic field superposition area.

[0008] As a preferred technical solution of the present invention, the first transmitting coil and the second transmitting coil are wound in opposite directions and are connected in series.

[0009] As a preferred technical solution of the present invention, a ring-shaped transmitting coil magnetic core is arranged between the first transmitting coil and the second transmitting coil, the first transmitting coil is attached to the outer wall thereof, and the second transmitting coil is attached to the inside thereof.

[0010] As a preferred technical solution of the present invention, the secondary side receiving device includes a secondary side coil, and the secondary side coil is a vertical spiral tube coil.

[0011] As a preferred technical solution of the present invention, a secondary coil magnetic core is arranged in the secondary coil.

[0012] As a preferred technical solution of the present invention, the secondary coil core is a manganese-zinc ferrite core made of PC95 material.

[0013] As a preferred technical solution of the present invention, the first transmitting coil and the second transmitting coil are installed in a flat cylindrical hollow aluminum shell, and an opening is provided above the flat cylindrical hollow aluminum shell through which the superimposed magnetic field of the first transmitting coil and the second transmitting coil can pass.

[0014] As a preferred technical solution of the present invention, there are at least two secondary side receiving devices.

[0015] In addition, in order to achieve the purpose, the present invention also proposes a parameter design method of a lightweight common anti-drift coupling mechanism of a UAV as described above, the key of which is that it includes the following steps:

[0016] S1: Determine the basic structural framework of the electromagnetic coupling mechanism according to the lightweight conformal design requirements of the UAV;

[0017] S2: configure the magnetic core;

[0018] S3: Set the maximum value of the secondary coil self-inductance L smax ;

[0019] S4: Simulate and calculate the coupling coefficient K of the coupling structure;

[0020] S5: Set the initial excitation current I of the transmitting coil start ;

[0021] S6: Increase the number of transmitting coils and secondary coils N P and N S , calculate the self-inductance L and mutual inductance M;

[0022] S7: Determine whether the mutual inductance M is greater than the preset mutual inductance M required , if not greater than, return to step S6;

[0023] S8: Determine the self-inductance L of the secondary coil s Is it less than the maximum value L of the secondary coil self-inductance? smax， If not less than, return to step S5;

[0024] S9: Determine whether the number of resonance points is 1, if the number of resonance points is not 1, return to step S5;

[0025] S10: Calculate the output power p out and output efficiency η;

[0026] S11: Determine output power p out Is it greater than the preset power p? required At the same time, the output efficiency is greater than the preset efficiency η required If not, return to step S3.

[0027] The present invention provides a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle and a parameter design method thereof, which has the following beneficial effects:

[0028] 1. By generating a superimposed magnetic field between two vertical spiral coils of different sizes, the receiving coil can receive the magnetic field when it is located above the two transmitting coils, so that the power and efficiency of wireless power transmission will not be affected regardless of the relative rotation angle of the drone during landing. On this basis, there is also a certain amount of horizontal lateral offset tolerance, and power can still be transmitted normally within a certain range of horizontal offset;

[0029] 2. The receiving device of the present invention is small and light, and can be installed on the vertical tripod of most UAV tripods. It has strong universality, and it is symmetrically installed inside the tripod, with balanced weight, and will not affect the appearance structure of the UAV. The conformal design will not increase unnecessary resistance and affect flight safety.

[0030] 3. The wireless charging device for drones uses electromagnetic fields to transfer energy between the primary and secondary sides. It can wirelessly charge drones in severe weather and humid environments, improving the reliability of power supply and ensuring personal and electrical safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the coil structure of the magnetic coupling mechanism provided in this embodiment;

[0032] Figure 2 A schematic diagram of the structure of a lightweight common anti-drift coupling mechanism for a UAV provided in this embodiment;

[0033] Figure 3 for Figure 2 Schematic diagram of the explosion structure;

[0034] Figure 4 A schematic diagram of the structure of a secondary side receiving device provided in this embodiment;

[0035] Figure 5 A schematic diagram of the structure of an equivalent alternative magnetic core provided in this embodiment;

[0036] Figure 6 A design flow chart of the magnetic coupling mechanism provided for this embodiment;

[0037] Figure 7 It is a first schematic diagram of the change of the parameters of the magnetic coupling mechanism when the diameter of the hollow cylinder of the magnetic core changes;

[0038] Figure 8 A second schematic diagram of the change in the parameters of the magnetic coupling mechanism when the diameter of the hollow cylinder of the magnetic core changes;

[0039] Fig. 9 The third schematic diagram of the change of the magnetic coupling mechanism parameters when the diameter of the hollow cylinder of the magnetic core changes;

[0040] Fig.10 It is the dimension parameter diagram of the omnidirectional common-type magnetic coupling mechanism;

[0041] Fig.11 It is a schematic diagram of magnetic flux distribution on the coaxial cross section of the magnetic coupling mechanism;

[0042] Fig.12 Schematic diagram of the change in coupling coefficient when adding a magnetic core;

[0043] Fig.13 This is a schematic diagram of the change in coupling coefficient when no magnetic core is added;

[0044] Fig.14 It is a schematic diagram of the coupling coefficient when the diameter of the transmitting solenoid coil changes;

[0045] Fig.15 It is a schematic diagram of the coupling coefficient when the height of the transmitting solenoid coil changes;

[0046] Fig.16 It is a schematic diagram of the coupling coefficient when the number of layers of the transmitting solenoid coil changes;

[0047] Fig.17 This is a schematic diagram of the change of the self-inductance of the transmitting coil during lateral displacement in the lateral displacement test;

[0048] Fig.18 This is a schematic diagram of the change of the self-inductance of the secondary coil during lateral displacement test;

[0049] Fig.19 This is a schematic diagram of the change of mutual inductance during lateral displacement test;

[0050] Fig. 20 This is a schematic diagram of the change of coupling coefficient during lateral offset test;

[0051] Fig.21 This is a schematic diagram of the change in the self-inductance of the transmitting coil when it is laterally offset in the rotation offset test;

[0052] Fig. 22 This is a schematic diagram of the change in the self-inductance of the secondary coil during lateral displacement in the rotation displacement test;

[0053] Fig.23 This is a schematic diagram of the change of mutual inductance during lateral displacement in the rotation displacement test;

[0054] Fig.24 This is a schematic diagram of the change of coupling coefficient during lateral displacement in the rotational displacement test;

[0055] Fig.25 Schematic diagram of simulated magnetic coupling mechanism parameter changes during tilt offset.

[0056] In the figure: 1. primary transmitting device; 11. first transmitting coil; 12. second transmitting coil; 13. annular transmitting coil core; 14. housing; 2. secondary receiving device; 21. secondary coil; 22. secondary coil core. DETAILED DESCRIPTION

[0057] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0058] Embodiment 1:

[0059] See also Figures 1 to 3As shown, a lightweight common-type anti-drift coupling mechanism of a drone comprises an inductively coupled primary transmitting device 1 and a secondary receiving device 2; the primary transmitting device 1 comprises two vertical spiral tube coils of different sizes, the two coils are a first transmitting coil 11 and a second transmitting coil 12, wherein the second transmitting coil 12 is located inside the first transmitting coil 11 and is coaxial therewith, the first transmitting coil 11 and the second transmitting coil 12 are wound in opposite directions and connected in series so as to generate magnetic fields in opposite directions, thereby forming a magnetic field superposition area between the inner side of the first transmitting coil 11 and the outer side of the second transmitting coil 12, when the drone is docked for charging, the secondary receiving device 2 is located directly above the magnetic field superposition area, thereby achieving coupling, wherein according to the actual use requirements of the drone and the number of drone legs, multiple secondary receiving devices 2 can be set for simultaneous use to meet the charging requirements;

[0060] In order to control the magnetic circuit that gathers the transmitting coil to generate the magnetic field, reduce the magnetic resistance of the magnetic circuit, and reduce the leakage magnetic field in the transmitting coil, a circular transmitting coil magnetic core 13 is arranged between the first transmitting coil 11 and the second transmitting coil 12. The circular transmitting coil magnetic core 13 is a customized circular cylindrical magnetic core, so that the first transmitting coil 11 fits its outer wall and the second transmitting coil 12 fits its inner wall. The circular transmitting coil magnetic core 13 adopts a manganese-zinc ferrite magnetic core made of PC95 material;

[0061] The first transmitting coil 11 and the second transmitting coil 12 as well as the annular transmitting coil magnetic core 13 are all installed in an oblate cylindrical hollow aluminum shell 14. An opening is provided above the oblate cylindrical hollow aluminum shell 14 so that the superimposed magnetic field of the first transmitting coil 11 and the second transmitting coil 12 can pass through, so that the magnetic field above is not blocked;

[0062] See also Figure 4 The secondary receiving device 2 is a conformal secondary coil designed to fit the UAV tripod structure. Two vertical spiral coils fitted on the vertical poles of the UAV tripod are used to receive the vertical upward magnetic flux generated by the transmitting coil. This not only fits the external structure of the UAV itself, but also does not affect the balance and weight of the UAV. It also meets the universal requirements of the coupling mechanism for the UAV in the design purpose. It is worth mentioning that the design of this secondary coil can be fitted with the tripod structure design on the inside of the UAV tripod, or it can be designed around the UAV tripod structure design on the outside of the UAV tripod. In order to control the magnetic circuit that gathers the magnetic field generated by the primary transmitting device 1, a secondary coil core 22 is installed in the secondary coil 21 (receiving solenoid coil). The secondary coil core 22 uses a manganese-zinc ferrite core made of PC95 material.

[0063] Embodiment 2:

[0064] See also Figure 5As shown, according to the first embodiment, it can be analyzed that the complete path of each magnetic flux line is from the bottom surface of the first transmitting coil 11 and the second transmitting coil 12 vertically upward through the top surface of the first transmitting coil 11 and the second transmitting coil 12 to the bottom surface of the secondary coil 21. Therefore, in the configuration design of the primary magnetic core, it is only necessary to satisfy that the path of each magnetic flux line can completely pass through the magnetic core. The annular transmitting coil magnetic core 13 can be formed into an annular shape by laying a strip power magnetic core for equivalent replacement. Compared with the customized annular cylindrical magnetic core, the equivalent magnetic core has a common size and a suitable price. In the experiment, the first transmitting coil 11 and the second transmitting coil 12 are collectively referred to as transmitting coils. The results of the experiment are shown in Table 1:

[0065] Table 1 Performance parameters of magnetic coupling mechanism under two core laying methods

[0066]

[0067] It can be seen that the coupling mechanism after using the equivalent magnetic core configuration direction is compared with the original magnetic core configuration mode, and the transmitting coil self-inductance L P , the self-inductance L of the secondary coil 21 S The three parameters of mutual inductance M decreased slightly, but the decrease did not exceed 8%, and the coupling coefficient k remained almost unchanged.

[0068] In order to facilitate the acquisition of the design parameters of the aforementioned coupling mechanism, a method for designing parameters of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle is also provided, the key feature of which is that it includes the following steps:

[0069] refer to Figure 6 As shown, the basic structural framework of the electromagnetic coupling mechanism is determined according to the lightweight conformal design requirements of the UAV:

[0070] In the design of the wireless charging system for drones, configuring the magnetic core is an important design link. The magnetic core can increase the mutual inductance of the coupling mechanism and optimize the magnetic field distribution, thereby improving the efficiency and anti-offset characteristics of the system. At the same time, the magnetic core can also reduce the loss and electromagnetic interference of the system and increase the stability and reliability of the system. Therefore, configuring the magnetic core can effectively improve the performance and efficacy of the drone wireless charging system, especially in scenarios that require long-distance, high-power transmission or work in complex environments, the role of the magnetic core is more obvious;

[0071] However, in the wireless charging system of drones, the weight of the magnetic core at the receiving end may affect the battery life and flight time of the drone, so it is necessary to make a trade-off between the configuration of the magnetic core at the receiving end. Therefore, when designing the magnetic coupling mechanism, specific analysis and calculation are required to make a trade-off between the weight of the magnetic core and the performance of the magnetic coupling mechanism to achieve the best design solution;

[0072] To verify the necessity of the core configuration at the receiving end of the omnidirectional common-mode magnetic coupling mechanism, it is necessary to analyze and compare the mutual inductance and total weight when the receiving end is configured with a core and when the receiving end is not configured with a core. In the Comsol simulation software, the receiving end of the omnidirectional common-mode magnetic coupling mechanism with and without a core configuration is simulated and analyzed, and the values ​​of the coupling coefficient k and the mutual inductance M are recorded, as shown in Table 2:

[0073] Table 2 Performance parameters of magnetic coupling mechanism with and without magnetic core configuration

[0074]

[0075] It can be seen that when the magnetic core is not configured, the total weight of the secondary coil 21 is reduced by 61g, but the mutual inductance is reduced by 6.03uH, and the coupling coefficient is reduced by 0.0432. The mutual inductance of the magnetic coupling mechanism is completely unable to support the normal operation of the drone WPT system;

[0076] Further, without configuring the magnetic core, the number of turns of the coil is increased to make the total weight the same as the original system. The self-inductance L of the transmitting coil is analyzed at this time. P , the self-inductance L of the secondary coil 21 S , mutual inductance M and coupling coefficient k. Since the outer diameter of the secondary coil 21 at the airborne end is limited by the structure of the drone tripod, the modification of the secondary coil 21 can only be done by increasing the number of turns without changing the outer diameter of the secondary coil 21 to increase the mutual inductance. After calculation, when the outer diameter of the secondary coil 21 is 24mm, the number of turns needs to be increased to 83. At this time, the total weight of the secondary coil 21 is the same as the total weight of the secondary coil 21 of the original system. In the Comsol simulation software, the number of turns of the secondary coil 21 of the original system is adjusted to 83 turns, and the simulation analysis determines the self-inductance L of the transmitting coil. P , the self-inductance L of the secondary coil 21 S , mutual inductance M and coupling coefficient k, and the comparison with the original system performance parameters is shown in Table 3:

[0077] Table 3 Performance parameters of magnetic coupling mechanism with or without magnetic core configuration at the same weight

[0078]

[0079] After removing the magnetic core and increasing the number of turns of the secondary coil, the weight of the omnidirectional common-mode magnetic coupling mechanism has almost no change, but the primary self-inductance L P The secondary side self-inductance L SIt dropped by 17.76uH, the mutual inductance M dropped by 5.51uH, and the coupling coefficient dropped by 0.0524. Without configuring the secondary magnetic core, the coupling coefficient of the coupling mechanism is still very small. Increasing the number of turns of the secondary coil alone cannot significantly increase the mutual inductance value, and such a mutual inductance value still cannot support the normal operation of the drone WPT system. In summary, for the omnidirectional common-mode magnetic coupling mechanism used in drones, the configuration of the secondary magnetic core is necessary;

[0080] In the above analysis, the necessity of core configuration for omnidirectional common-mode magnetic coupling mechanism is determined. In the actual configuration of the core, the core material is the primary factor that determines its performance. The type and selection of core material will directly affect the core's magnetic permeability, saturation magnetic induction, hysteresis loss, electrical insulation performance, mechanical strength and other aspects, thus having an important impact on the power transmission, anti-offset characteristics and frequency response of the magnetic coupling mechanism. Therefore, the correct selection of core material is of great significance to ensure the lightweight, efficient, stable and safe operation of the drone wireless charging system.

[0081] At present, commonly used magnetic core materials include manganese-zinc ferrite, nanocrystalline alloy, soft magnetic alloy, etc., each of which has specific magnetic properties and physical properties. The emerging nanocrystalline material performs well in soft magnetic properties, with advantages such as high initial magnetic permeability, low coercivity, low magnetic loss and high saturation magnetic induction intensity, which is very suitable for magnetic coupling mechanisms that require lightweight design. However, the existing nanocrystalline alloy has low magnetic permeability under high-frequency magnetic field, and its resistivity is much smaller than that of ferrite, which will cause serious eddy current loss, so it is not suitable for high-frequency wireless charging system of drones. Soft magnetic alloy is a high-performance magnetic material with high magnetic permeability, low coercivity and low hysteresis, but in the wireless charging system of drones, soft magnetic alloy is also not applicable. First, the magnetic properties of soft magnetic alloy will be affected in the high-frequency environment of the wireless charging system of drones. For example, magnetization loss and ferromagnetic resonance may occur at high frequencies, which will reduce the transmission efficiency. Secondly, the saturation magnetic induction intensity of soft magnetic alloy is relatively low, which cannot meet the requirements of the wireless charging system of drones for high magnetic induction intensity, which will affect the efficiency and stability of power transmission.

[0082] Therefore, this embodiment will compare and analyze the magnetic permeability, magnetic loss volume density, saturation magnetic flux density, residual magnetic flux density, Curie temperature and volume density of Mn-Zn ferrites of different materials, study the influence of Mn-Zn ferrites of different materials on the performance of the coupling mechanism, and then select the Mn-Zn ferrite core most suitable for the wireless charging system of drones, as shown in Table 4:

[0083] Table 4 TDK manganese-zinc ferrite power core parameter standards

[0084]

[0085] As shown in Table 4, it is a standard table of TDK manganese-zinc ferrite power core parameters. It can be seen that compared with the power cores made of PC40, PC44, PC47 and PC90, the reference value of the magnetic permeability of the power core made of PC95 is μ i The power loss per unit volume below 60°C is much higher. cv It is also significantly smaller than the power cores of the other four materials. The residual flux density β at room temperature r In addition, the magnetic loss volume density P of PC95 power core under high temperature environment is cv , saturation flux density β s , saturation flux density β under high temperature environment s , Curie temperature T c , density ρ b It is also on par with the power cores of the other four materials. In other words, the PC95 material power core has better medium and low temperature characteristics and higher magnetic permeability while having similar density, and the magnetic permeability changes little with temperature, which is conducive to resonance. This makes the system using the PC95 material power core in the design of the drone wireless charging system have higher mutual inductance M, coupling coefficient k and smaller loss. In summary, the primary and secondary magnetic cores of the omnidirectional common magnetic coupling mechanism designed by the present invention are both made of PC95 material Mn-Zn ferrite power cores;

[0086] Similar to the difference in core materials, different core configurations will also affect the mutual inductance and coupling coefficient of the coupling mechanism, thereby further changing the system's operating frequency, power transmission efficiency, output voltage and other performance indicators;

[0087] Compared with the cost requirement of the primary core configuration, the configuration of the secondary core is directly related to the total weight of the secondary coil 21 at the airborne end. To reduce the weight of the wireless charging system of the drone, the optimal configuration of the core is an indispensable step. Similarly, according to the magnetic circuit model of the coaxial section of the primary and secondary solenoids of the omnidirectional common electromagnetic coupling mechanism, the main magnetic flux Φ of the coupling mechanism M The complete path of each magnetic flux line flows from the top surface of the first transmitting coil 11 and the second transmitting coil 12 to the bottom surface of the secondary coil 21, which means that the outermost part of the secondary cylindrical magnetic core is the key part of gathering the magnetic flux line path. Therefore, this embodiment attempts to hollow out a small cylindrical magnetic core from the center of the secondary cylindrical magnetic core to reduce the weight of the secondary magnetic core;

[0088] However, this will cause the magnetic flux density of the remaining secondary circular cylindrical core to increase significantly, even reaching the level of magnetic saturation. When the core is magnetically saturated, the magnetic permeability of the core will drop significantly, causing the transmission efficiency of the coupling mechanism to drop significantly, affecting the normal operation of the wireless charging system. In addition, the magnetic saturation of the core will also produce large hysteresis loss and eddy current loss, increase the energy loss of the coupling mechanism, and reduce the efficiency of wireless charging. Therefore, the volume of the hollow small cylinder cannot be increased indefinitely, and the peak magnetic flux density β inside the core must be considered. max Whether the saturation flux density β of the core material used has been reached s ;

[0089] Modify the diameter R of the hollow cylinder in Comsol simulation software H , record the mutual inductance M, coupling coefficient k and peak flux density β inside the core max The value of Figure 7-9 As shown, it can be seen that as the radius R of the hollow cylinder in the secondary magnetic core H The increase of the transmitting coil self-inductance L P There is basically no change, the mutual inductance M and coupling coefficient k decrease slightly. H When it reaches 9mm, it is reduced by 0.49uH and 0.0033 respectively. The self-inductance value of the secondary coil 21 is L S Then in R H When it reaches 9mm, it is reduced by 1.99uH. It can be seen that the radius R of the hollow cylinder in the secondary magnetic core H The increase of will not have a significant impact on the coupling strength of the magnetic coupling mechanism, and the performance indicators of the magnetic coupling mechanism can still meet the normal operation of the UAV WPT system. Fig. 9 It can be seen that only when R H When it reaches 9.5mm, the maximum value of the magnetic flux density of the working magnetic field of the magnetic coupling mechanism is β max Only exceeds the saturation flux density β of PC95 material power core s , reaching 560mT. H When β is 9mm, max It is only 150mT, so the radius R of the hollow cylinder of the secondary magnetic core of the designed omnidirectional common magnetic coupling mechanism is finally determined H The optimized secondary core configuration is 9mm, and the comparison with the original system parameters is shown in Table 5:

[0090] Table 5 Performance parameters of magnetic coupling mechanism before and after secondary core optimization

[0091]

[0092] Furthermore, it is necessary to further design the specific dimensional parameters of the frame to determine the final frame model. First, the dimensional parameters that need to be designed and their meanings are determined in the cross-sectional model of the omnidirectional common-mode magnetic coupling mechanism. Fig.10 As shown, D PIN is the outer diameter of the second transmitting coil 12 at the transmitting end, D POUT is the inner diameter of the first transmitting coil 11, H PIN and H POUT are the heights of the inner and first transmitting coils 11, D PMCOUT and D PMCIN H is the outer diameter and inner diameter of the annular transmitting coil core 13, PMC is the height of the annular transmitting coil core 13, H M is the charging distance of the magnetic coupling mechanism, D S and D SMC H is the outer diameter of the secondary coil 21 and the secondary coil core 22, S and H SMC is the height of the secondary coil 21 and the secondary coil core 22. Due to the large number of parameters, it is too complicated to analyze the influence of the changes of all parameters on the coupling technology and mutual inductance at the same time. Therefore, it is necessary to analyze the magnetic circuit of the omnidirectional common magnetic coupling mechanism, preliminarily judge the influence trend of each parameter change on the coupling coefficient, and determine the order of parameter design;

[0093] like Fig.11 Shown Φ P1 and Φ P2 are the leakage flux of the first transmitting coil 11, collectively referred to as the transmitting coil leakage flux Φ P , Φ M11 , Φ M12 and Φ M21 , Φ M22 are the magnetic fluxes transmitted from the inner and first transmitting coils 11 to the secondary coils 21-1 and 21-2, which are collectively referred to as the main magnetic flux of the coupling mechanism Φ M , Φ S1 and Φ S2 are the leakage flux of the secondary coil 21-1 and the secondary coil 21-2, which are collectively referred to as the leakage flux of the secondary coil 21 Φ S ;

[0094] The purpose of the magnetic coupling mechanism structural design is to find the most suitable structure so that the secondary coil 21 can receive as much magnetic flux as possible from the transmitting coil, so that the coupling coefficient of the magnetic coupling mechanism is higher. Fig.11 It can be seen that to obtain a higher coupling coefficient, it is necessary to reduce Φ as much as possible. P , increasing Φ M ;

[0095] Since the simulation of the magnetic coupling mechanism is based on the existing coupling mechanism parameters, an initial parameter needs to be determined before the coupling mechanism size design and the initial parameter needs to be optimized. First, according to the main performance indicators of the system, the vertical distance H between the transmitting coil and the secondary coil 21 is M Set to 10mm;

[0096] Next is the secondary coil 21 and the magnetic core design. In the omnidirectional common magnetic coupling mechanism of the drone designed in the present invention, the secondary coil 21 of the airborne end is designed to fit the inside of the drone tripod. From the above magnetic circuit analysis, it can be seen that D S It should be as large as possible. Therefore, when the size of the tripod of the design object UAV is determined, D S It was also determined to be 24mm;

[0097] In addition, the main performance indicators of the system require that the UAV WPT system achieve a 20mm offset tolerance in the horizontal direction and a 360° rotational offset tolerance. Fig.11 It can be seen from the analysis that the energy transfer of the magnetic coupling mechanism utilizes the vertically upward magnetic flux generated by the transmitting coaxial solenoid. Therefore, the channel area of ​​the transmitting coaxial solenoid should include the entire offset area of ​​the secondary coil 21 coil surround surface in the horizontal direction. Therefore, the outer diameter of the second transmitting coil 12 is initially selected to be 180 mm, and the inner diameter of the first transmitting coil 11 is initially selected to be 300 mm. For the selection of the wire diameter of the magnetic coupling mechanism, the wire diameter of the secondary coil 21 is determined by the output current of the receiving end, and the wire diameter of the transmitting coil is determined by the primary inductance current of the transmitting end. Therefore, according to the input and output performance of the WPT system designed according to the present invention, considering the actual winding spacing, the wire diameter D of the secondary coil 21 is wires Temporarily take 2mm wire diameter (0.1mm×200 strands), the wire diameter D of the transmitting coil wirep Temporarily take 3mm wire diameter (0.1mm×450 strands), the specific performance and selection of Litz wire will be analyzed in detail later;

[0098] After determining the coupling mechanism parameters with certain design basis, it is necessary to initialize the remaining parameters without specific design basis. Among them, the height H of the secondary coil 21 S It is a parameter limited only by the length of the drone tripod pole. The present invention initially selects it as 40 mm, but this parameter does not represent any meaning and is only used as the height H of the secondary coil 21. S The initial height before optimization. In addition, the initial number of turns N of the second transmitting coil 12 at the transmitting end PIN , the initial number of turns N of the first transmitting coil 11 POUT and the receiving end secondary coil 21N SThe initial number of turns is determined as 15 turns, 15 turns and 20 turns according to the initial height, wire diameter and dense winding method, as shown in Table 6:

[0099] Table 6 Initial parameters of omnidirectional common-mode magnetic coupling mechanism

[0100]

[0101] In the above table, the design parameters that need to be optimized are the outer diameter D of the second transmitting coil 12 at the transmitting end. POUT , the height H of the second transmitting coil 12 POUT , the inner diameter D of the first transmitting coil 11 PIN , the height H of the first transmitting coil 11 PIN , the height H of the secondary coil 21 S These five parameters;

[0102] The first step is to analyze the height H of the secondary coil 21 S In the Comsol simulation software, the parameters of the first transmitting coil 11 and the second transmitting coil 12 are controlled to be the same, and the number of turns of the secondary coil 21 at the receiving end is 20. S The variation trend of the coupling coefficient k of the omnidirectional common-mode magnetic coupling mechanism is analyzed in the range of 40 mm to 80 mm in two cases: without adding a magnetic core and adding a magnetic core inside the secondary coil 21. Figure 12-13 As shown. The diameter of the magnetic core added inside the secondary coil 21 is the same as the inner diameter of the coil, and the height is also the same as the height of the secondary coil 21. It can be seen that under the condition that the first transmitting coil 11 and the second transmitting coil 12 are controlled to be the same, and the number of turns of the secondary coil 21 at the receiving end is 20, as the height H of the secondary coil 21 remains unchanged. S The coupling coefficient k does not change significantly, but changes from 0.029 to 0.027 with a decreasing trend. Even when Hs doubles from 40mm to 80mm, the coupling coefficient only decreases by 7%. When the secondary magnetic core is added, as the height Hs of the secondary coil 21 increases, the coupling coefficient k also increases significantly. When Hs doubles from 40mm to 80mm, the coupling coefficient k increases from 0.0693 to 0.0933. This is because when the magnetic core is added, the increased coil height also increases the height of the magnetic core. The larger magnetic core is configured inside the secondary coil 21 to gather more magnetic flux lines, so that more and more magnetic flux passes through the secondary coil 21. However, the configuration of a larger magnetic core is bound to increase the weight of the receiving end, which is undesirable in the lightweight design of the receiving end. Therefore, this embodiment will continue to temporarily take the height of the secondary coil 21 as 40mm. After the parameters of the transmitting coil are finally determined, the height Hs of the secondary coil 21 is determined by combining the primary parameters.

[0103] The second step is to analyze the outer diameter D of the second transmitting coil 12 at the transmitting end. PIN and the inner diameter D of the first transmitting coil 11 POUT The effect of coupling coefficient k on the coupling mechanism is as follows: According to the results of the above magnetic circuit analysis, D PIN Varies in the range of 60mm-90mm, D PIN Varies within the range of 150mm-180mm,

[0104] D PIN and D POUT When the outer diameter D of the annular transmitting coil core 13 changes PMCOUT and inner diameter D PMCIN It also changes accordingly, and the value of the coupling coefficient k is determined by simulation analysis in Comsol;

[0105] like Fig.14 As shown in POUT is any value, D PIN As D decreases, the coupling coefficient k keeps decreasing. This is because as D PIN As D increases, the distance between the second transmitting coil 12 and the secondary coil 21 becomes farther and farther, and the magnetic flux passing through the secondary coil 21 becomes less and less. PIN When D is 90 mm, k is the maximum value. PIN is any value, D POUT As D increases, the coupling coefficient k also decreases. PIN Set to 90mm, D POUT Set to 150mm, at which point the coupling coefficient k takes the maximum value;

[0106] The third step is to analyze the height H of the second transmitting coil 12 at the transmitting end. PIN and the height H of the first transmitting coil 11 POUT The effect on the coupling coefficient k of the coupling mechanism. According to the initial parameter data of the coupling mechanism set by the present invention, H PIN and H POUT The minimum value is 45mm. PIN and H POUT When the height H of the annular transmitting coil core 13 is PMC According to the analysis, since the design of the drone coupling mechanism only pursues the lightweight and miniaturization of the receiving end, and there is no limit on the volume and weight of the transmitting end, the height H of the annular transmitting coil core 13 is set to PMC Configuration and H PIN and H POUT The larger value of H PIN Varies in the range of 45mm-75mm, H POUTVaries in the range of 45mm-75mm, H PMC It also changes accordingly, and the value of the coupling coefficient k is determined by simulation analysis in Comsol;

[0107] like Fig.15 It can be found that when the number of turns of the second transmitting coil 12 and the first transmitting coil 11 of the transmitting end coaxial solenoid remains unchanged, whether H is maintained POUT H PIN Increase or maintain H PIN H POUT As H increases, the coupling coefficient k will continue to decrease. This is because as H PIN and H POUT As H increases, the distance between the second transmitting coil 12 and part of the first transmitting coil 11 and the secondary coil 21 becomes farther and farther, and the magnetic flux passing through the secondary coil 21 becomes less and less. POUT Take 45mm and H PIN When 45 mm is taken, k is the maximum value. Therefore, H POUT Set to 45mm, H PIN Set to 45mm;

[0108] According to the above, the height H of the second transmitting coil 12 at the transmitting end PIN and the height H of the first transmitting coil 11 POUT From the simulation analysis, we can know that when H PIN and H POUT At the same time, as the number of turns N of the second transmitting coil 12 at the transmitting end is reduced, the coupling coefficient k of the omnidirectional common-mode magnetic coupling mechanism is increased. PIN and the number of turns N of the first transmitting coil 11 POUT Winding around the core in multiple layers reduces H with the same number of turns. PIN and H POUT , but this will also increase the D of the outer coil of the first transmitting coil 11 in disguised form. POUT and reduce the D of the outer coil of the second transmitting coil 12 PIN The specific effect of such a configuration needs to be compared after obtaining specific data through simulation. The number of layers of the first transmitting coil 11 and the second transmitting coil 12 and the first transmitting coil 11 are both set to Q, and Q is changed in the range of 1-3. The value of the coupling coefficient k is determined by simulation analysis in Comsol;

[0109] Figure Fig.16As shown in FIG. 1 , when the number of turns of the second transmitting coil 12 and the first transmitting coil 11 of the transmitting end coaxial solenoid is kept unchanged, when the number of layers Q increases, the coupling coefficient k increases accordingly. This is because as Q increases, the distance between the second transmitting coil 12 and the first transmitting coil 11 and the secondary coil 21 becomes closer and closer, so that the magnetic flux passing through the secondary coil 21 increases, and the trend of increasing the magnetic flux is greater than that of increasing the coil D of the first transmitting coil 11. POUT and reduce the second transmitting coil 12D PIN The magnetic flux decreases due to the Q value. When Q is 3, k is the maximum value, so Q is set to 3.

[0110] In the above-mentioned coupling mechanism structure design, in order to make the magnetic flux lines between the transmitting coil and the secondary coil 21 more dense and orderly, a whole ring-shaped cylindrical magnetic core is configured in the channel area of ​​the coaxial solenoid coil at the transmitting end. This magnetic core is not only large in size and weight, but also has a special shape and specifications compared to ordinary magnetic cores, and needs to be customized according to specific dimensions. This is not only not convenient for the size optimization test of the omnidirectional common magnetic coupling mechanism, but also makes the cost of the primary magnetic core out of control, which is not conducive to the promotion and application of the wireless charging system for drones;

[0111] In summary, the structure and size parameters of the magnetic coupling mechanism have been determined. Finally, the number of turns of the transmitting coil and the secondary coil 21 of the coupling mechanism need to be adjusted according to the mutual inductance value required by the main circuit of the UAV WPT system, so as to finally meet the needs of the main circuit of the system. The mutual inductance value M required The expression is:

[0112]

[0113] According to the wire diameter of the transmitting coil of 3mm and the current carrying parameters specified in its data sheet, the transmitting coil current is selected as 8A. Substituting the system required output voltage of 25V and the system resonant frequency of 100kHz into the expression, the required mutual inductance value M is obtained. required is 4.98uH, the actual designed coupling mechanism mutual inductance value should be greater than M required ;

[0114] By modifying the number of turns of the secondary coil 21 in the Comsol simulation software to adjust the mutual inductance value M of the magnetic coupling mechanism, the specific size parameters of the omnidirectional common-type magnetic coupling mechanism are determined as shown in Table 7 and Table 8:

[0115] Table 7 Dimensional parameters of omnidirectional common-mode magnetic coupling mechanism

[0116]

[0117]

[0118] Table 8 Performance parameters of omnidirectional common-mode magnetic coupling mechanism

[0119]

[0120] Constant inductance and constant mutual inductance are the basis for stable operation of the primary and secondary compensation topology circuits and stable power transmission. The mutual inductance of the magnetic coupling mechanism and the self-inductance of the primary and secondary sides will change with the degree of misalignment. The magnitude of their changes determines the strength of the coupling mechanism's misalignment tolerance. Therefore, the present invention will test the anti-drift characteristics of the coupling mechanism from two aspects: horizontal offset and rotational offset, so as to determine whether it can meet the needs of the drone wireless charging system.

[0121] (1) Lateral offset test:

[0122] For wireless charging systems designed for drones, the transmitting end is often fixed on the ground. The offset of the coupling mechanism is often caused by the offset of the secondary coil 21 due to various reasons during the landing of the drone. Therefore, in order to test the anti-offset characteristics of the omnidirectional common magnetic coupling mechanism of the drone, the transmitting coil is fixed in the Comsol simulation software, and the horizontal position of the secondary coil 21 is adjusted to simulate the horizontal offset generated when the drone lands, and the performance parameters of the coupling mechanism under different degrees of horizontal offset are tested respectively; the axis of the first transmitting coil 11 and the second transmitting coil 12 are taken as the origin, and the bottom surface of the first transmitting coil 11 and the second transmitting coil 12 is taken as the XY plane, so that the secondary coil 21 is offset by 0 to 20 mm in the X-axis, Y-axis and θ=45° directions respectively, and the mutual inductance M, coupling coefficient k, and self-inductance L of the coupling mechanism are measured. P and the self-inductance L of the secondary coil 21 S , within the 0~20mm offset range in three directions, the mutual inductance of the coupling mechanism drops within 0~1uH, the coupling coefficient drops within 0~0.011, the self-inductance of the transmitting coil drops within 0~0.4uH, and the self-inductance of the secondary coil 21 drops within 0~0.1uH. Among them, when the offset occurs in the X-axis direction, the performance parameters of the coupling mechanism change the most. When the offset is 20mm, the mutual inductance of the coupling mechanism decreases by 0.97uH, the coupling coefficient decreases by 0.011, the self-inductance of the transmitting coil decreases by 0.26uH, and the self-inductance of the secondary coil decreases by 0.1uH. When the offset occurs in the Y-axis direction, the performance parameters of the coupling mechanism hardly change, such as Figure 17-20 As shown;

[0123] (2) Rotational offset test:

[0124] Similar to the horizontal offset generated by the drone during landing, the rotation offset generated by landing is also the main reason for the degradation of the coupling mechanism performance. In order to test the anti-rotation offset performance of the drone's omnidirectional common-mode magnetic coupling mechanism, the transmitting coil is fixed in the Comsol simulation software, and the horizontal position of the secondary coil 21 is adjusted to simulate the rotation offset generated when the drone lands and test the performance parameters of the magnetic coupling mechanism;

[0125] Since the transmitting coil and the secondary coil 21 of the omnidirectional common magnetic coupling mechanism are both axisymmetric devices, the rotation offset angle range selected by the present invention is 0-180°, and the lateral offset range superimposed during the rotation offset is 0-20 mm. The variation law of the offset parameters from 180° to 360° is the same as that from 0 to 180°. The midpoint of the line connecting the bottom axes of the two secondary coils 21 is taken as the origin, and the bottom surfaces of the first transmitting coil 11 and the second transmitting coil 12 are taken as the XY plane. On the basis of the rotation axis of the secondary coil 21 being offset by 20 mm in the X-axis, Y-axis and θ=45° directions, the secondary coil 21 is rotated 30°, 60°, 90°, 120°, 150°, and 180° around the origin as the center to test the mutual inductance M, coupling coefficient k, and self-inductance L of the magnetic coupling mechanism. P and the self-inductance L of the secondary coil 21 S， like Figure 21-24 As shown;

[0126] (3) Tilt test:

[0127] One of the characteristics of the omnidirectional common-mode magnetic coupling mechanism is its universality for drone tripods. However, in the above analysis of drone tripods, it can be found that the vertical rods of some drone tripods are not completely perpendicular to the horizontal plane, but are tilted at a certain angle to the vertical direction. Therefore, it is necessary to test the tilt of the secondary coil 21 of the omnidirectional common-mode magnetic coupling mechanism to verify its universality. Since the tilt angle of the secondary coil 21 is determined by the drone tripod, the influence of the tilt angle on the self-inductance of the coil will not change the resonant state of the circuit. It is only necessary to test its influence on the mutual inductance M and the coupling coefficient k.

[0128] In the Comsol simulation software, the transmitting coil is fixed, the bottom surfaces of the two secondary coils 21 are taken as the XY plane, the line connecting the centers of the two ground circles is taken as the X axis, and the rotation axes of the two secondary coils 21 are offset toward the X axis by θ. B , so that θ B The mutual inductance M and coupling coefficient k of the coupling mechanism are tested at 5°, 10°, 15°, and 20° respectively. The simulation results are shown in Fig.25 As shown;

[0129] The simulation results show that when the inclination angle of the secondary coil 21 of the magnetic coupling mechanism changes from 0° to 20°, the mutual inductance and coupling coefficient of the magnetic coupling mechanism are slightly reduced, the mutual inductance is reduced by 0.3uH, and the coupling coefficient is reduced by 0.0035. However, after the secondary coil 21 is tilted by 20°, the mutual inductance and coupling coefficient of the coupling mechanism can still support the normal operation of the drone wireless charging system.

Claims

1. A parameter design method for a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle, characterized in that: The lightweight common-form anti-drift coupling mechanism of the UAV comprises a primary transmitting device and a secondary receiving device, wherein the primary transmitting device comprises a first transmitting coil and a second transmitting coil, wherein the first transmitting coil and the second transmitting coil are respectively vertical spiral tube coils of different sizes, the second transmitting coil is located inside the first transmitting coil and is coaxial with the first transmitting coil, a magnetic field superposition area is formed between the inner side of the first transmitting coil and the outer side of the second transmitting coil, and when the UAV is docked for charging, the secondary receiving device is located directly above the magnetic field superposition area; The parameter design method includes the following steps: S1: Determine the basic structural framework of the electromagnetic coupling mechanism according to the lightweight conformal design requirements of the UAV; S2: configure the magnetic core; S3: Set the maximum value of the secondary coil self-inductance L smax ; S4: Simulate and calculate the coupling coefficient of the coupled structure K ; S5: Set the initial excitation current of the transmitting coil I start ; S6: Increase the number of transmitting coils and secondary coils N P and N S , calculate the self-inductance L And mutual inductance M ; S7: Determine mutual inductance M Is it greater than the preset mutual inductance? M required , if not greater than, return to step S6; S8: Determine the self-inductance of the secondary coil L s Is it less than the maximum value of the secondary coil self-inductance? L smax , if it is not less than, return to step S5; S9: Determine whether the number of resonance points is 1, if the number of resonance points is not 1, return to step S5; S10: Calculate output power p out and output efficiency η ; S11: Determine output power p out Is it greater than the preset power? p required At the same time, the output efficiency is greater than the preset efficiency η required If not, return to step S3.

2. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 1, characterized in that: The first transmitting coil and the second transmitting coil are wound in opposite directions and are connected in series.

3. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 1, characterized in that: A ring-shaped transmitting coil magnetic core is arranged between the first transmitting coil and the second transmitting coil, the first transmitting coil is attached to the outer wall thereof, and the second transmitting coil is attached to the inner wall thereof.

4. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 1, characterized in that: The secondary side receiving device comprises a secondary side coil, and the secondary side coil is a vertical spiral tube coil.

5. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 4, characterized in that: A secondary coil magnetic core is arranged in the secondary coil.

6. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 5, characterized in that: The secondary coil core is a manganese-zinc ferrite core made of PC95 material.

7. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 5, characterized in that: The first transmitting coil and the second transmitting coil are installed in a flat cylindrical hollow aluminum shell, and an opening is arranged above the flat cylindrical hollow aluminum shell, through which the superimposed magnetic field of the first transmitting coil and the second transmitting coil can pass.

8. The parameter design method of a lightweight common anti-drift coupling mechanism of an unmanned aerial vehicle according to claim 1, characterized in that: There are at least two secondary side receiving devices.

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