A magnetic coupling mechanism for anti-deviated wireless charging of drones

Abstract

The present invention discloses a magnetic coupling mechanism for anti-drift wireless charging of unmanned aerial vehicles, comprising a transmitting coil, a receiving coil and a ferrite core, wherein the transmitting coil is two orthogonal coils, respectively recorded as transmitting coil one and transmitting coil two; the ferrite core is in the shape of a cross, the two orthogonal coils are wound around the ferrite core, and the receiving coil is embedded in the unmanned aerial vehicle; by adjusting the magnitude of the transmitting coil current, a magnetic field in a specific direction is generated directly above the transmitting coil, so that the magnetic field generated by the transmitting coil is directly opposite to the receiving coil. The present invention not only has good anti-drift performance, but also has a small fluctuation amplitude of the receiving coil current, and at the same time, the efficiency decreases very little when a single horizontal offset or a compound offset occurs.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission, and in particular to a magnetic coupling mechanism for realizing anti-drift wireless charging of unmanned aerial vehicles. Background Art

[0002] Drones usually refer to commercial quadcopters. Initially, drones were developed by the United States in 1944 for military purposes as remote-controlled bomb carriers. In the past decade, drone technology has been increasingly mature in the civilian field; due to the advantages of drones such as high maneuverability, compact structure and light weight, this technology has shown broad application prospects in many fields such as security surveillance, agriculture, 3D map modeling, damage assessment, delivery and express delivery, aerial photography and many other fields. At the same time, the drone market is also growing year by year. It is estimated that by 2025, the total sales of the drone market will reach 43 billion US dollars, with a compound annual growth rate of 13.8%.

[0003] The most common way to charge a drone is to replace the battery, that is, to replace the exhausted battery in the drone with a fully charged battery. The physical battery replacement method requires the help of staff, which seriously affects the application of drones in remote areas and is contrary to the original intention of automated inspection of power grid drones. Traditional charging methods cannot meet the requirements of unmanned power grids, so a safer and more convenient automated charging method is needed.

[0004] Wireless Power Transfer (WPT) was first proposed by the famous American scientist Nikola Tesla as a method of energy transmission. It is a new charging technology that can transfer electrical energy from the power supply to the load without direct electrical contact. This technology can maintain high efficiency and a relatively streamlined design while being safe and flexible. Wireless charging is different from traditional wired charging. Because it does not require direct electrical contact, wireless charging is less likely to generate sparks, is less likely to wear and age, and is more flexible, safe and reliable. It has unique advantages for automated charging in harsh outdoor environments and unmanned occasions. Its application in drones can not only improve the drone's endurance and operating range, but also improve the drone's waterproof and dustproof performance, meeting the requirements for power supply for drone power grid inspections. Summary of the invention

[0005] Purpose of the invention: In order to solve the problem that efficient coupling mechanisms are insufficient in anti-drift performance and cannot take into account both efficiency and anti-drift performance, the present invention provides a magnetic coupling mechanism for anti-drift wireless charging of drones.

[0006] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A magnetic coupling mechanism for anti-drift wireless charging of a drone includes a transmitting coil, a receiving coil and a ferrite core. The transmitting coil is two orthogonal coils, which are respectively recorded as transmitting coil one and transmitting coil two. The ferrite core is in the shape of a cross, and the two orthogonal coils are wound around the ferrite core. The receiving coil is embedded in the drone. By adjusting the magnitude of the transmitting coil current, a magnetic field in a specific direction is generated directly above the transmitting coil, so that the magnetic field generated by the transmitting coil is directly opposite to the receiving coil.

[0008] Preferably: when the transmitting coil 1 is directly opposite to the receiving coil, the transmitting coil 2 is orthogonal to the receiving coil, the influence of the transmitting coil 2 is ignored, and the coupling between the transmitting coil and the receiving coil is regarded as the coupling between two square solenoid coils.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] In the present invention, an orthogonal dual transmitting coil is adopted, and the magnetic field generated by the transmitting coil is always directly opposite to the receiving coil by adjusting the current of the two transmitting coils, thereby eliminating the influence of the angle deviation on the current and efficiency of the receiving coil. While improving the system's anti-drift capability, it still has strong coupling performance, effectively increasing the flight time and working range of the drone. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of a magnetic coupling mechanism provided by the present invention for realizing anti-drift wireless charging of a drone.

[0012] Figure 2 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when the offset is 0°.

[0013] Figure 3 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when the offset is 15°.

[0014] Figure 4 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when it is offset by 30°.

[0015] Figure 5 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when it is offset by 45°.

[0016] Figure 6 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when it is offset by 60°.

[0017] Figure 7 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when it is offset by 75°.

[0018] Figure 8 This is the magnetic field simulation diagram of the anti-offset magnetic coupling mechanism when it is offset by 90°.

[0019] Fig. 9 is the relationship between the coupling coefficient and the turn spacing.

[0020] Fig.10 is the relationship between the coupling coefficient and the length of the transmitting coil.

[0021] Fig.11 This is the relationship between the coupling coefficient and the length of the transmitting coil when the offset is 4 cm.

[0022] Fig.12 is the relationship between the coupling coefficient and the height of the receiving coil.

[0023] Fig.13 is the relationship between the coupling coefficient and the core thickness.

[0024] Fig.14 is the relationship between the coupling coefficient and the width of the cross core.

[0025] Fig.15 is the relationship between the coupling coefficient in the offset state and the core length. DETAILED DESCRIPTION

[0026] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0027] A magnetic coupling mechanism for anti-drift wireless charging of drones, such as Figure 1 As shown, it includes a transmitting coil, a receiving coil 3 and a ferrite core 4. The transmitting coil is two orthogonal coils, which are respectively denoted as transmitting coil 1 and transmitting coil 2. The shape of the ferrite core is a cross, and the two orthogonal coils are wound around the ferrite core. The receiving coil 3 is embedded in the drone. In this embodiment, the receiving coil 3 is a hollow vertical coil embedded in the landing gear of the drone, and the installation position is far away from the belly of the drone. The transmitting coil 1 and the transmitting coil 2 are powered by two independent power supplies, and the frequencies and phases of the two power supplies are controlled to be the same. The ferrite core is cross-shaped and loaded on the transmitting coil. By adjusting the magnitude of the transmitting coil current, a magnetic field in a specific direction is generated directly above the transmitting coil, so that the magnetic field generated by the transmitting coil is directly opposite to the receiving coil 3.

[0028] The transmitting coil is the primary coil, and the receiving coil is the secondary coil. The coupling coefficient k is usually used as the performance index of the coupling mechanism. The coupling coefficient directly affects the power and system efficiency of wireless charging. The coupling coefficient of the magnetic coupling mechanism is: k represents the coupling coefficient, L P Represents the self-inductance of the primary coil, L S represents the self-inductance of the secondary coil, and M represents the mutual inductance between the primary and secondary coils.

[0029] When the coupling mechanism is offset, the self-inductance value often does not change, but the mutual inductance value will change accordingly. The change of the mutual inductance value will directly affect the coupling coefficient of the coupling mechanism. Therefore, maintaining the stability of the mutual inductance value in the offset state is an effective way to improve the anti-offset performance of the coupling mechanism. According to Neumann's theorem, the mutual inductance of the primary and secondary coils in the facing state is:

[0030]

[0031] Among them, N P is the number of turns of the primary coil, N S is the number of turns of the secondary coil, a represents the length of the primary coil, l2 is the length of the secondary coil, d is the vertical distance between the primary and secondary coils, and μ0 is the magnetic permeability of vacuum.

[0032] When the coil is deflected, the following equation holds:

[0033]

[0034] Where r1 and r2 are the outer diameters of the circular primary and secondary coils respectively, and t is the horizontal distance between the center points of the two coils after they are offset.

[0035] It can be inferred that when the coil is horizontally offset, the mutual inductance of the primary and secondary coils in the horizontal offset state is:

[0036]

[0037] Among them, r1 is the outer diameter of the circular primary coil, r2 is the outer diameter of the circular secondary coil, t is the horizontal distance between the center points of the two coils after offset, θ is the horizontal offset angle of the primary coil, and φ is the horizontal offset angle of the secondary coil.

[0038] According to the above formula, the inductance parameters of the coil can be easily calculated using simulation software.

[0039] According to the Biot-Savart law, the current element of a section of a current-carrying wire is The magnetic induction intensity generated by a point P in space is Where μ0 is the magnetic permeability of vacuum, is the conductor current element, is the unit vector of the current element pointing to point P, and r is the distance from point P to the current element. Based on the above analysis, combined with the Biot-Savart law, the magnetic induction intensity of the magnetic field generated by the primary coil wire at a point can be obtained as:

[0040]

[0041] The angle ξ between the unit vector of the current element pointing to point P and the xy plane satisfies:

[0042]

[0043] in, It represents the magnetic induction intensity of the magnetic field generated by the primary coil wire at a point, μ0 is the magnetic permeability of vacuum, I represents the current in the current-carrying wire, a represents the length of the primary coil, b represents the width of the primary coil, (x, y, h) is the coordinate of point P, and ξ represents the angle between the unit vector of the current element pointing to point P and the xy plane.

[0044] The primary coil is a circular coil, and the z-axis component of the magnetic induction intensity generated by the rectangular coil is the sum of the components of the magnetic induction intensity of the four sides. Then the magnitude of the vertical component of the magnetic induction intensity of the magnetic field generated by the primary coil is:

[0045]

[0046] Among them, B Z (x, y, h) represents the magnitude of the vertical component of the magnetic induction intensity of the magnetic field generated by the primary coil.

[0047] From this, the magnitude of the vertical component of the magnetic induction intensity of the magnetic field generated by the rectangular coil can be calculated.

[0048] like Figure 2-8 As shown: These are simulation diagrams of the magnetic field direction when the offsets are 0°, 15°, 30°, 45°, 60°, 75° and 90° respectively. It can be seen that by adjusting the current of the transmitting coil, a magnetic field facing the receiving coil can be generated at each angle, and the magnetic field is relatively uniform, thereby realizing wireless charging of the drone in all directions.

[0049] When the transmitting coil 1 is facing the receiving coil 3, the transmitting coil 2 is orthogonal to the receiving coil 3. The coupling coefficient k between the transmitting coil 2 and the receiving coil 3 is obtained by simulation. 23 Much smaller than the coupling coefficient k between the transmitting coil 1 and the receiving coil 3 13 , the influence of the transmitting coil 2 can be ignored, and the coupling between the transmitting coil and the receiving coil 3 can be regarded as the coupling between two square solenoid coils. At the same time, it is found that by giving different values ​​of transmitting coil current, a magnetic field in a specific direction can be generated directly above the transmitting coil, that is, the magnetic field generated by the transmitting coil can be made to face the receiving coil, achieving an effect similar to that of the receiving coil facing a certain transmitting coil, thereby eliminating the influence of angle offset on the performance of the magnetic coupling mechanism.

[0050] The turn spacing of the transmitting coil is s, and s is varied between 2-14 mm. The coupling coefficient k between the two coils is obtained through Maxwell modeling simulation analysis. As the turn spacing s increases, the coupling coefficient decreases, such as Fig. 9 As shown, a tight winding is selected, that is, the turn spacing s is 2 mm, so as to obtain the maximum coupling coefficient.

[0051] Depend on Fig.10 It can be seen that when the length L1 of the transmitting coil changes, the length L2 of the transmitting coil core will also change accordingly, so that L1 changes between 90-220 mm. As L1 increases, the horizontal magnetic flux received by the receiving coil increases, the coupling of the two coils is enhanced, and the coupling coefficient increases. However, since the length of the receiving coil is determined by the landing gear, the present invention selects a fixed value of 14 cm. When the length of the transmitting coil is much larger than the length of the receiving coil, the horizontal magnetic flux that can be captured by the receiving coil reaches a peak value, but the increase in the length of the transmitting coil will increase the leakage magnetic flux of the coupling device, and the system coupling coefficient will decrease.

[0052] For drone wireless charging systems, anti-drift performance often needs to be given priority, so asymmetric primary and secondary coils are usually used. Although the coupling performance will be reduced, the use of magnetic coupling resonant WPT technology can greatly improve the coupling ability and achieve strong coupling under weak coupling conditions. Usually, when a drone lands on a charging platform, there will be no vertical deviation, only horizontal deviation, and the maximum deviation is usually 3cm. The present invention tested the coupling performance under a 4cm deviation and found that the larger transmitting coil slightly enhanced the coupling performance of the coil. Fig.11 It can be seen that the coupling coefficient is the largest when the length of the transmitting coil is 19 cm. Considering the system coupling capability and anti-offset performance, the length of the transmitting coil L1 is selected to be 16 cm.

[0053] The height of the receiving coil is H3. When H3 increases, the coupling coefficient will first increase and then decrease. Fig.12 As shown. Analysis shows that the reason why the coupling coefficient increases first and then decreases is similar to that when the length of the transmitting coil is changed. The magnetic field generated by the transmitting coil is fixed. Increasing H3 can increase the effective magnetic flux receiving area, and the coupling coefficient will increase. However, when H3 is set too large, the horizontal magnetic flux that the receiving coil can capture reaches its peak value. Continuing to increase it will reduce the coupling coefficient. When H3 is greater than 40mm, the increase in the coupling coefficient gradually slows down. In order to reduce weight and save costs, H3 is selected as 40mm.

[0054] Fig.13 The relationship between the coupling coefficient and the thickness of the magnetic core. Since the transmitting coil adopts a solenoid coil, the wire needs to be wound on the magnetic core. Therefore, when the thickness of the magnetic core changes, the height of the transmitting coil will also change accordingly. The coupling mechanism is modeled and simulated. The thickness of 0mm in the figure represents no magnetic core. In this case, the magnetic leakage is large and the coupling coefficient is very low. After adding the magnetic core, the coupling coefficient will increase significantly, but when the thickness of the magnetic core exceeds 3mm, the coupling coefficient will not increase or even decrease. Considering the cost and practical application, H2 is selected as 3mm.

[0055] Considering that the magnetic coupling mechanism proposed in the present invention needs to generate orthogonal magnetic fields in two directions, the shape of the magnetic core needs to be symmetrical, and two rectangular magnetic cores, namely cross-shaped magnetic cores, are needed to ensure the same coupling performance in two orthogonal directions. The magnetic core length is set to L2 and the magnetic core width is set to L5. Fig.14 It can be seen that the coupling coefficient of the 19cm long transmitting coil is the highest under the horizontal offset state of 4cm, so two transmitting coils of 16cm and 19cm are selected here for simulation calculation. Keep the core length L2 unchanged, and change the width L5 of the cross core between 40-110mm. It can be seen that the coupling coefficient does not increase significantly after the core width is greater than 90mm, so the cross core width is selected to be 90mm. At the same time, it is found that the coupling performance of the 19cm coil relative to the 16cm length in the offset state is slightly improved, but the decrease in the coupling coefficient in the facing state is significantly greater than the improvement in the offset state. For the actual application of the invention, the coupling performance has a greater negative effect, which can confirm the correctness of choosing a transmitting coil length of 16cm.

[0056] Then the coupling coefficient under 4cm horizontal offset with different core lengths was simulated and calculated. Fig.15 It can be found that the longer the core is, the better the coupling performance is in the offset state, and the decrease in the coupling coefficient in the offset state caused by reducing the core width is greater than the increase in the coupling coefficient in the facing state. Even if the transmitting coil and the receiving coil are of the same length, the negative effect is greater than the positive effect. This also confirms the correctness of selecting the maximum core width to make the coil densely wound on the core surface.

[0057] In this embodiment, both the transmitting coil and the receiving coil 3 are solenoid coils, the coils are tightly wound, the turn spacing s is 2 mm, the transmitting coil L1 is 160 mm, the receiving coil height H3 is 40 mm, the magnetic core thickness H2 is 3 mm, the length L2 is 156 mm, and the width L5 is 90 mm.

[0058] The present invention has good anti-deviation performance. When the system efficiency is at a single angle deviation, it is as low as 82.14%, and the current fluctuation amplitude of the receiving coil is only 17%. When the system efficiency is at a single horizontal deviation or a compound deviation, the efficiency decreases very little, and the current fluctuation does not exceed 11.4%.

[0059] The present invention is aimed at the special application scenario of wireless charging of unmanned aerial vehicles. On the basis of traditional magnetically coupled resonant wireless power transmission, the magnetic coupling mechanism of the unmanned aerial vehicle anti-deviation wireless charging of the present invention is adopted, which greatly improves the anti-deviation performance of wireless charging of unmanned aerial vehicles while ensuring the transmission efficiency. This is of great significance for effectively increasing the working range of unmanned aerial vehicles and realizing the automation of unmanned aerial vehicle inspection operations and unmanned power grids. By adopting orthogonal dual transmitting coils, by adjusting the current of the two transmitting coils, the magnetic field generated by the transmitting coil can always be directly opposite to the receiving coil, thereby eliminating the influence of angle offset on the current and efficiency of the receiving coil. The parameters of the magnetic coupling mechanism are optimized by parameter scanning to determine reasonable design parameters. The invention has strong coupling performance while improving the anti-deviation capability of the system, increasing the endurance time and working range of the unmanned aerial vehicle, and has broad application prospects in the field of wireless charging of unmanned aerial vehicles.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A magnetic coupling mechanism for anti-deviated wireless charging of drones, characterized by: It comprises a transmitting coil, a receiving coil (3) and a ferrite core (4), wherein the transmitting coil is two orthogonal coils, which are respectively denoted as transmitting coil one (1) and transmitting coil two (2); the ferrite core is in the shape of a cross, the two orthogonal coils are wound around the ferrite core, and the receiving coil is embedded in the drone; a magnetic field in a specific direction is generated directly above the transmitting coil by adjusting the magnitude of the transmitting coil current, so that the magnetic field generated by the transmitting coil is directly opposite to the receiving coil (3); The transmitting coil is the primary coil, and the receiving coil is the secondary coil, so the coupling coefficient of the magnetic coupling mechanism is: k represents the coupling coefficient, L P Represents the self-inductance of the primary coil, L S represents the self-inductance of the secondary coil, and M represents the mutual inductance between the primary and secondary coils; The mutual inductance of the primary and secondary coils in the facing state is: Among them, N P is the number of turns of the primary coil, N S is the number of turns of the secondary coil, a represents the length of the primary coil, l2 is the length of the secondary coil, d is the vertical distance between the primary and secondary coils, and μ0 is the magnetic permeability of vacuum; The mutual inductance of the primary and secondary coils in the horizontal offset state is: Among them, r1 is the outer diameter of the circular primary coil, r2 is the outer diameter of the circular secondary coil, t is the horizontal distance between the center points of the two coils after offset, θ is the horizontal offset angle of the primary coil, and φ is the horizontal offset angle of the secondary coil.

2. The magnetic coupling mechanism for anti-drift wireless charging of drones according to claim 1, characterized in that: The magnetic induction intensity of the magnetic field generated by the primary coil wire at a point is: The angle ξ between the unit vector of the current element pointing to a point P in space and the xy plane satisfies: in, represents the magnetic induction intensity of the magnetic field generated by the primary coil wire at a point, μ0 is the vacuum magnetic permeability, I represents the current of the current-carrying wire, a represents the length of the primary coil, b represents the width of the primary coil, (x, y, h) is the coordinate of point P, ξ represents the angle between the unit vector of the current element pointing to point P and the xy plane; The primary coil is a circular coil. The magnitude of the vertical component of the magnetic induction intensity of the magnetic field generated by the primary coil is: Among them, B Z (x, y, h) represents the magnitude of the vertical component of the magnetic induction intensity of the magnetic field generated by the primary coil.

3. The magnetic coupling mechanism for anti-drift wireless charging of drones according to claim 2, characterized in that: When the transmitting coil 1 (1) is directly opposite to the receiving coil (3), the transmitting coil 2 (2) is orthogonal to the receiving coil (3), the influence of the transmitting coil 2 (2) is ignored, and the coupling between the transmitting coil and the receiving coil (3) is regarded as the coupling between two square solenoid coils.

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