A low magnetic flux leakage interference omnibearing energy transmission unmanned aerial vehicle wireless charging system

Abstract

The present application relates to wireless charging technical field, specifically to a kind of low leakage flux interference's all-around energy transmission unmanned plane wireless charging system, including the transmitting module being arranged in wireless charging platform and the receiving module being arranged on unmanned plane;The transmitting module is composed of A-phase solenoid transmitting coil, B-phase solenoid transmitting coil and C-phase solenoid transmitting coil, wherein each phase solenoid transmitting coil includes two arc solenoid coils, and the three-phase solenoid transmitting coils are uniformly distributed in the same plane to form a complete circumference;The receiving mechanism includes two receiving coils, and the two receiving coils are wound on the two legs of the unmanned plane landing gear respectively;The transmitting module mainly generates horizontal magnetic field, and hardly generates vertical magnetic field, to reduce leakage flux interference;In three-phase solenoid transmitting coil, the current with 120 ° phase difference is excited to generate rotating magnetic field, to realize all-around wireless energy transmission under arbitrary position and arbitrary angle offset.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology, specifically to a low-leakage magnetic flux interference omnidirectional power transfer drone wireless charging system. Background Technology

[0002] Unmanned aerial vehicles (UAVs) are aircraft that do not require human piloting. They offer advantages such as flexibility, efficiency, safety, and low cost, and have broad application prospects in military operations, civilian aerial photography, power line inspection, agricultural plant protection, environmental protection, logistics transportation, and disaster relief. However, most UAVs currently have short flight times, requiring frequent returns to base for manual recharging or battery replacement. This power replenishment method is unsuitable for unattended missions, significantly limiting the widespread application of UAVs. Wireless power transfer (WPT) technology offers advantages such as flexibility, convenience, safety, and reliability, and has unique advantages in harsh conditions such as dust and underwater environments, as well as in unattended missions. Using wireless charging, UAVs can achieve autonomous power replenishment, effectively increasing their operational range and meeting the requirements of unattended missions. This is of great significance for further enhancing the intelligence of UAVs.

[0003] The electromagnetic coupling mechanism is a key component of a drone's wireless charging system. Figure 1 Several typical coupling mechanisms for drone wireless charging systems are presented. Face-to-face circular or rectangular coils are one of the most commonly used coupling mechanisms in drone wireless charging systems, for example... Figure 1 The butterfly coil in (a) and Figure 1 (b) shows a face-to-face loop coil. This type of coupling mechanism has advantages such as a large coupling coefficient, high power efficiency, and good resistance to rotational offset. However, it also suffers from poor structural adaptability, occupies additional installation space, obstructs the drone's downward view, increases wind resistance, and increases leakage flux interference to the drone's equipment. To address the leakage flux interference problem, some scholars have proposed a method such as... Figure 1 (c) shows a three-phase tightly coupled magnetic coupling mechanism. Other scholars have also proposed a similar mechanism. Figure 1 (d) shows an orthogonal coupling mechanism that reduces leakage magnetic interference and is lightweight, but both of these coupling mechanisms have poor resistance to angular displacement. To improve resistance to angular displacement, a symmetrical magnetic coupling mechanism that can be arbitrarily rotated has been proposed, which has strong structural adaptability. In addition, another mechanism has been proposed... Figure 1 (e) illustrates a transmitting mechanism with opposite inner and outer coil windings, which improves resistance to angular misalignment while reducing leakage flux interference. On the other hand, considering the need for a compact coupling mechanism and resistance to positional misalignment, some scholars have proposed a method such as... Figure 1(f) shows a target-shaped transmitting coil that can generate horizontal and vertical magnetic fields, as well as a two-dimensional orthogonal pickup coil. Some researchers have also proposed a squirrel-cage receiving mechanism embedded in the landing gear of a UAV, which offers strong structural adaptability. Although the above magnetic coupling mechanisms primarily utilize horizontal magnetic fields to transmit electrical energy, the presence of circular coils in the transmitting mechanism inevitably generates a large vertical magnetic field, resulting in high leakage flux interference. In summary, most of the studied coupling mechanisms cannot simultaneously meet the requirements of high offset tolerance and low leakage flux interference.

[0004] On the other hand, to improve high offset tolerance, the excitation current is usually controlled based on the position and angle of the receiving coil, so that the resulting magnetic field is pointed towards the receiving coil in real time, thereby achieving omnidirectional wireless power transfer. Some researchers use attitude sensors to detect the position and angle of the receiving coil, and then use communication circuits to send the attitude information of the receiving coil to the transmitting side, thereby controlling the excitation current to generate a targeted magnetic field pointing towards the receiving coil, thus achieving omnidirectional wireless power transfer. However, this method requires additional sensors and communication circuits, which will increase the system cost. To address this, some researchers use mutual inductance identification to replace the attitude detection of the receiving coil. Mutual inductance identification uses DC current information from the transmitting side for identification, so no communication circuit is needed. However, this method requires multiple excitation attempts and multiple DC current checks to identify the mutual inductance, resulting in low real-time performance, and the detection and calculation are also relatively complex. Summary of the Invention

[0005] To simultaneously meet the requirements of high offset tolerance and low leakage flux interference, improve the real-time performance of the wireless charging system, and reduce various costs, this invention provides an omnidirectional power transfer drone wireless charging system with low leakage flux interference. The system includes a transmitting module mounted on a wireless charging platform and a receiving module mounted on the drone. The transmitting module consists of an A-phase solenoid transmitting coil, a B-phase solenoid transmitting coil, and a C-phase solenoid transmitting coil. Each phase solenoid transmitting coil includes two arc-shaped solenoid coils, and the three phase solenoid transmitting coils are evenly distributed on the same plane to form a complete circumference. The drone includes a landing gear. The receiving mechanism includes two receiving coils, which are respectively wound around the two legs of the drone's landing gear.

[0006] Furthermore, the A-phase solenoid transmitting coil includes two arc-shaped solenoid coils, A1 and A2, connected in series; the B-phase solenoid transmitting coil includes two arc-shaped solenoid coils, B1 and B2, connected in series; and the C-phase solenoid transmitting coil includes two arc-shaped solenoid coils, C1 and C2, connected in series.

[0007] Furthermore, in the transmitting module, six arc-shaped solenoid coils are evenly distributed on the same plane to form a complete circle, wherein:

[0008] The left and right ends of the A1 arc solenoid coil are adjacent to the right end of the B2 arc solenoid coil and the left end of the C2 arc solenoid coil, respectively.

[0009] The left and right ends of the A2 arc solenoid coil are adjacent to the right end of the C1 arc solenoid coil and the left end of the B1 arc solenoid coil, respectively.

[0010] The left end of the B2 arc solenoid coil is immediately adjacent to the right end of the C1 arc solenoid coil, and the right end of the C2 arc solenoid coil is immediately adjacent to the left end of the B1 arc solenoid coil.

[0011] Furthermore, the arc of each arc-shaped solenoid coil is 60°.

[0012] Furthermore, the arc-shaped solenoid coil includes an arc-shaped magnetic core and a coil winding spirally wound on the arc-shaped magnetic core.

[0013] Furthermore, in the transmitting module, the phase difference of the excitation current between the three-phase solenoid transmitting coils is 120°, wherein:

[0014] When ωt=0, the synthesized magnetic field inside the launch module points in the positive y-axis direction;

[0015] When ωt=π / 2, the synthesized magnetic field inside the launch module points in the positive x-axis direction;

[0016] When ωt = π, the synthesized magnetic field inside the launch module points in the negative y-axis direction;

[0017] When ωt=3π / 2, the synthesized magnetic field inside the launch module points in the negative x-axis direction;

[0018] ω represents the angular frequency of the excitation current, and t represents time.

[0019] Furthermore, the two receiving coils are connected in series.

[0020] The beneficial effects of this invention are:

[0021] This paper proposes an omnidirectional wireless charging system for unmanned aerial vehicles (UAVs) with low leakage flux interference. In this system, the transmitting module employs a three-phase solenoid transmitting coil, which primarily generates a horizontal magnetic field and produces almost no vertical magnetic field, thus significantly reducing leakage flux interference to the UAV. To achieve high offset tolerance for wireless charging, a current with a 120° phase difference is excited in the three-phase solenoid transmitting coil, generating a rotating magnetic field. Regardless of the position and angle of the receiving coil within the transmitting module, sufficient electrical energy can be picked up, enabling omnidirectional wireless power transfer at any position and angle. Therefore, this method offers advantages such as no need to detect the orientation of the receiving coil, no need for complex calculations and control, high real-time performance, simple implementation, and low cost.

[0022] The solenoid receiving coil is wound around the drone's landing gear. Compared with the traditional circular coil structure, it has advantages such as not taking up extra installation space, not increasing the drone's flight drag, and not obstructing the drone's view below. Attached Figure Description

[0023] Figure 1 Examples of coupling mechanisms for several typical drone wireless charging systems;

[0024] Figure 2 This invention relates to a low-leakage magnetic flux interference omnidirectional power transfer drone wireless charging system;

[0025] Figure 3 The composite magnetic field distribution at different times in this invention;

[0026] Figure 4 This is a comparison diagram of the leakage flux of the two coil structures of the present invention;

[0027] Figure 5 This is the circuit topology of the system of the present invention;

[0028] Figure 6 This invention relates to the relationship between the rotation angle of the receiving coil and the mutual inductance.

[0029] Figure 7 This is a diagram of the experimental apparatus for the present invention;

[0030] Figure 8 These are the experimental waveforms of the output voltage and load voltage of the three-phase inverter of this invention;

[0031] Figure 9 These are the experimental waveforms of the excitation current and the receiving coil current of this invention;

[0032] Figure 10 The output power and efficiency of this invention under different angular and positional offsets;

[0033] Figure 11This is a demonstration diagram of the omnidirectional wireless power transmission of the present invention under various positional and angular offsets. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides an omnidirectional wireless charging system for power transfer drones with low leakage flux interference, such as... Figure 2 As shown, the device includes a transmitting module mounted on a wireless charging platform and a receiving module mounted on a drone. The transmitting module consists of an A-phase solenoid transmitting coil, a B-phase solenoid transmitting coil, and a C-phase solenoid transmitting coil. Each phase solenoid transmitting coil includes two arc-shaped solenoid coils, and the three phase solenoid transmitting coils are evenly distributed on the same plane to form a complete circumference. The drone includes a landing gear. The receiving mechanism includes two receiving coils, which are respectively wound around the two legs of the drone's landing gear.

[0036] Specifically, such as Figure 2 As shown, the A-phase solenoid transmitting coil includes two arc-shaped solenoid coils, A1 and A2, connected in series; the B-phase solenoid transmitting coil includes two arc-shaped solenoid coils, B1 and B2, connected in series; and the C-phase solenoid transmitting coil includes two arc-shaped solenoid coils, C1 and C2, connected in series.

[0037] Specifically, such as Figure 2 As shown, in the transmitting module, six arc-shaped solenoid coils are evenly distributed on the same plane to form a complete circle, wherein:

[0038] The left and right ends of the A1 arc solenoid coil are adjacent to the right end of the B2 arc solenoid coil and the left end of the C2 arc solenoid coil, respectively.

[0039] The left and right ends of the A2 arc solenoid coil are adjacent to the right end of the C1 arc solenoid coil and the left end of the B1 arc solenoid coil, respectively.

[0040] The left end of the B2 arc solenoid coil is immediately adjacent to the right end of the C1 arc solenoid coil, and the right end of the C2 arc solenoid coil is immediately adjacent to the left end of the B1 arc solenoid coil.

[0041] Specifically, the arc of each arc-shaped solenoid coil is 60°.

[0042] Specifically, to enhance the magnetic field generated by the transmitting mechanism, a ring-shaped magnetic core is embedded inside the solenoid. That is, the arc-shaped solenoid coil includes an arc-shaped magnetic core and a coil winding spirally wound on the arc-shaped magnetic core.

[0043] Specifically, two receiving coils are connected in series to form a total receiving coil. This solenoid receiving coil wound on the landing gear has the following advantages over traditional circular or rectangular coils mounted on the landing gear: 1) it does not occupy additional installation space; 2) it does not increase the flight drag of the UAV; 3) it does not obstruct the view below the UAV.

[0044] Specifically, in the transmitting module, a current with a 120° phase difference is excited in the three-phase solenoid transmitting coil, resulting in a top view of the composite magnetic field distribution inside the transmitting module at different times, as shown below. Figure 3 As shown.

[0045] Depend on Figure 3 It can be seen that when ωt=0, the synthetic magnetic field inside the transmitting module points in the positive y-axis direction; when ωt=π / 2, the synthetic magnetic field inside the transmitting module points in the positive x-axis direction; when ωt=π, the synthetic magnetic field inside the transmitting module points in the negative y-axis direction; and when ωt=3π / 2, the synthetic magnetic field inside the transmitting module points in the negative x-axis direction. ω represents the angular frequency of the excitation current, and t represents time. The direction of the synthetic magnetic field inside the transmitting module scans over time, covering any direction of a circle, completing one rotation in one time cycle, forming a circular rotating magnetic field. When the drone lands inside the transmitting module, regardless of its position or angle, the solenoid receiving coil wound on the landing gear will always capture enough magnetic energy, thus achieving omnidirectional wireless charging. This method of generating a rotating magnetic field in the transmitting module to achieve omnidirectional wireless charging has the following advantages compared to using a targeted magnetic field: 1) No need to detect the position and angle of the receiving coil; 2) No need for a communication link between the transmitter and receiver; 3) No need for complex control and calculation; 4) Low implementation cost.

[0046] Specifically, as is well known, the leakage flux introduced by a wireless charging device needs to be as small as possible to reduce electromagnetic interference to the internal electronic equipment of the drone. Circular coils are a widely used type of coil in drone wireless charging systems. This invention selects a circular transmitting coil for comparative analysis with the proposed three-phase solenoid transmitting coil. Under the same conditions (excitation current, coil size, total wire usage, total magnetic core usage, etc.), the magnetic field strength of the two coil structures at the drone fuselage is compared, such as... Figure 4 As shown, an observation plane 10cm above the transmitting coil is selected to simulate the location of the internal electronic equipment of the UAV.

[0047] The circular transmitting coil produces a maximum magnetic field strength of 150 μT at the observation plane, while the three-phase solenoid transmitting coil produces a maximum magnetic field strength of only 15 μT, a tenfold reduction. This is because the circular transmitting coil primarily generates a vertical (z-direction) magnetic field, resulting in a stronger magnetic field at the UAV fuselage. The three-phase solenoid transmitting coil primarily generates a horizontal (xy-plane) magnetic field, while the vertical magnetic field is very weak. Therefore, the proposed three-phase solenoid transmitting coil can effectively reduce leakage flux interference at the UAV fuselage. Furthermore, the solenoid receiving coil wound around the UAV landing gear also primarily captures the horizontal magnetic field, perfectly matching the horizontal magnetic field generated by the three-phase solenoid transmitting coil.

[0048] In one embodiment, to illustrate that generating a rotating magnetic field requires maintaining the excitation phase difference of the three-phase solenoid transmitting coil at 120° and keeping the amplitude constant, the present invention designs as follows: Figure 5 The circuit topology shown is explained below. In this circuit topology, three half-bridge inverters with a 120° phase difference are used to drive the three-phase solenoid transmitting coils respectively. The three-phase solenoid transmitting coils are compensated by three LCC resonant topologies with constant current output characteristics, so that the excitation current in the three-phase solenoid transmitting coils is constant and is not affected by mutual inductance and load changes.

[0049] Furthermore, S1 and S2 are MOSFET switches used to drive the half-bridge inverter (hereinafter referred to as the A-phase inverter) for the A-phase solenoid transmitting coil; S3 and S4 are MOSFET switches used to drive the half-bridge inverter (hereinafter referred to as the B-phase inverter) for the B-phase solenoid transmitting coil; and S5 and S6 are MOSFET switches used to drive the half-bridge inverter (hereinafter referred to as the C-phase inverter) for the C-phase solenoid transmitting coil. fi C fi and C i These represent the compensation inductance, parallel compensation capacitor, and series compensation capacitor in the three LCC resonant compensation networks, i = 1, 2, 3. L1, L2, L3, and L4 are the self-inductances of the A-phase solenoid transmitting coil, B-phase solenoid transmitting coil, C-phase solenoid transmitting coil, and the main receiving coil, respectively. C4 is the series compensation capacitor on the receiving side. D1-D4 are the diodes in the full-bridge rectifier. o For the filter capacitor, R L This is a resistive load. Note that the load during actual wireless charging of a drone is a battery, whose impedance changes slowly with charging time. A resistive load can be used to simulate the battery load to simplify the analysis. dc I is the DC input voltage of the system. f1 I f2 and I f3IA, IB, IC are the output currents of the inverters in phases A, B, and C, respectively. I1, I2, I3, and I4 are the excitation currents of the solenoid transmitting coils in phases A, B, and C, respectively, and the total receiving coil. UC o This is the load voltage.

[0050] Since the parameters of each phase solenoid transmitting coil and the corresponding positions of the three LCC resonant compensation networks in the three-phase solenoid transmitting coil are almost identical, it is possible to let L f =L f1 =L f2 =L f3 C f =C f1 =C f2 =C f3 C p =C1=C2=C3,L p =L1=L2=L3, thus simplifying the analysis. Define the output voltages of the A-phase, B-phase, and C-phase inverters as U1, U2, and U3 respectively. Based on the fundamental frequency approximation method and the requirement of a 120° phase difference in the excitation current, U1, U2, and U3 can be expressed as...

[0051]

[0052] for Figure 5 L in fi and C fi The loop can be obtained by applying KVL.

[0053]

[0054] Where ω = 2πf, f is the system's operating frequency, and ω is the angular frequency. When jωL f +1 / jωC f =0, that is, C f =1 / ω 2 L f When, equation (2) can be rewritten as

[0055]

[0056] As can be seen from equation (3), the amplitudes of the excitation currents of the three-phase solenoid transmitting coils are equal, and the phase difference is 120°.

[0057] Define M 14 M 24 and M 34 These are the mutual inductances between the solenoid transmitting coil and the main receiving coil in phase A, the solenoid transmitting coil and the main receiving coil in phase B, and the solenoid transmitting coil and the main receiving coil in phase C, respectively. When jωL4 + 1 / jωC4 = 0, that is, C4 = 1 / ω 2At L4, neglecting the equivalent series resistance of the total receiving coil, based on the mutual inductance coupling theory, Figure 5 The KVL equations on the receiving side can be expressed as follows:

[0058]

[0059] in, R1 is the equivalent resistance before bridge rectification, and R4 is the equivalent series resistance of the total receiving coil.

[0060] The output power of the system can be calculated from equations (1)-(4) and expressed as follows:

[0061]

[0062]

[0063] Among them, M eq This is the equivalent mutual inductance between the transmitting module and the main receiving coil.

[0064] From equation (5), it can be seen that when the input voltage U dc Compensating inductor L f Load resistance R L Once the resistance R4 is determined, the system's output power P o From equivalent mutual inductance M eq Decision. To evaluate the omnidirectional wireless power transmission performance of the proposed system, COMSOL simulation was used to calculate the mutual inductance between the total receiving coil and the three transmitting coils when the total receiving coil rotates around the z-axis. Furthermore, the equivalent mutual inductance was calculated according to equation (6), such as... Figure 6 As shown. The relevant parameters of the coupling mechanism are described in the experimental section.

[0065] Depend on Figure 6 It can be seen that the three mutual inductances of the total receiving coil are not simultaneously zero at any rotation angle, and the equivalent mutual inductance M eq It hardly changes with the rotation angle, thus ensuring that the total receiving coil picks up approximately the same amount of electrical energy in all directions, which is beneficial for achieving omnidirectional wireless power transmission.

[0066] Specifically, adopting such as Figure 7The system experimental setup shown is used to verify the effectiveness of the invention. The system experimental setup mainly consists of a DC power supply, a three-phase inverter, an LCC resonant compensation network, a transmitting mechanism, a receiving mechanism, a receiving-side circuit, and a load. Based on the landing gear dimensions of the P450-NX UAV developed by Amu Lab, a resin frame with a length of 22cm, a side spacing of 25cm, and a diameter of 3cm was fabricated. The receiving mechanism uses 0.05mm × 600 strands of Litz wire wound 100 turns on both sides of this frame. The weight of the two solenoid receiving coils is 150g, which has a minimal impact on the UAV's payload. The three-phase solenoid transmitting coils are wound on a circular resin frame with a diameter of 50cm, a width of 4cm, and a height of 3.5cm. Thirty PC95 magnetic cores with dimensions of 50mm × 10mm × 25mm are embedded inside the frame. The transmitting mechanism is wound with 0.05mm × 1000 strands of Litz wire, with each phase solenoid transmitting coil having 100 turns. The system's DC input voltage U... dc The voltage is 150V, the operating frequency f is 100kHz, and the load resistance R is... L The resistance is 10Ω, and the relevant circuit parameters are shown in Table 1. R1, R2, R3 and R4 are the equivalent series resistances of the A-phase solenoid coil, the B-phase solenoid coil, the C-phase solenoid coil and the main receiving coil, respectively.

[0067] Table 1 System Circuit Parameters

[0068]

[0069] When the main receiving coil has no position or angular deviation, the experimentally measured three-phase inverter output voltages (U1, U2, U3) and load voltage (U) are... o Waveform as Figure 8 As shown, the waveforms of the excitation currents (I1, I2, I3) of the three-phase solenoid transmitting coil and the total receiving coil current (I4) are as follows: Figure 9 As shown. By setting the drive timing of the three-phase inverter, the phase difference between the output voltages U1, U2, and U3 of the three-phase inverter is made 120°, thereby making the phase difference between the excitation currents I1, I2, and I3 of the three-phase solenoid transmitting coils 120°. Note that due to the constant current output characteristic of the LCC resonant compensation network, Figure 9 The amplitude and phase of the three-phase excitation current do not change with variations in mutual inductance and load. At this time, the effective value of the total receiving coil current I4 is 4.9A, and the load voltage U... o The average voltage is 45.4V, the output power is 206.1W, and the transmission efficiency is 75.0%.

[0070] The system's output power and DC-DC efficiency were measured experimentally under different angular and positional offsets, as follows: Figure 10As shown. When the main receiving coil rotates arbitrarily around the z-axis, the output power remains between 203.8W and 224.5W, and the efficiency remains between 75.0% and 75.9%, as... Figure 10 As shown in (a). The reason why the output power and efficiency fluctuate relatively little at this time is that the equivalent mutual inductance does not change much with the rotation angle (see...). Figure 6 When the main receiving coil moves along the x-axis, the output power remains between 170.1W and 206.2W, and the efficiency remains between 72.3% and 75.0%. Figure 10 As shown in (b), at this point, the mutual inductance between the B-phase solenoid transmitting coil and the main receiving coil, and between the C-phase solenoid transmitting coil and the main receiving coil, is almost zero. Only the mutual inductance between the A-phase solenoid transmitting coil and the main receiving coil is relatively large. As the offset distance increases, the mutual inductance between the main receiving coil and the A-phase solenoid transmitting coil decreases. Therefore, the output power and efficiency decrease with the increase of the offset distance. When the main receiving coil moves in the y-axis direction, the output power remains between 206.2W and 247.1W, and the efficiency remains between 75.0% and 79.8%. Figure 10 As shown in (c), the mutual inductance between the phase B solenoid transmitting coil and the main receiving coil, as well as between the phase C solenoid transmitting coil and the main receiving coil, is almost zero. Only the mutual inductance between the phase A solenoid transmitting coil and the main receiving coil is relatively large. As the offset distance increases, the distance between one side of the main receiving coil and one side of the phase A solenoid transmitting coil becomes closer, and the total equivalent mutual inductance increases. Therefore, the output power and efficiency increase with the offset distance. In summary, regardless of the position or angle of the main receiving coil, the system's output power is greater than 170.1W, and the transmission efficiency is greater than 72.3%.

[0071] The proposed system exhibits low DC-DC efficiency, with the main losses concentrated in the coupling mechanism (approximately 70%). Due to the small cross-sectional area of ​​the solenoid receiving coil, the coupling coefficient (approximately 0.036) is low, requiring a larger excitation current for the same transmission power, thus increasing the losses in the coupling mechanism. In practical applications, increasing the cross-sectional area of ​​the solenoid receiving coil or using magnetically conductive materials for the landing gear can increase the coupling coefficient and improve efficiency. Furthermore, using a rotating magnetic field method also reduces efficiency compared to a magnetic field-oriented control method; therefore, a magnetic field-oriented control method can also be used to improve system efficiency in practical applications. However, the rotating magnetic field method, compared to magnetic field-oriented control, eliminates the need for detecting the receiving coil's orientation, complex calculations and control, and communication links, offering advantages in simplicity and low cost. Additionally, while the proposed system sacrifices some efficiency, it significantly increases the freedom of power transmission and greatly reduces leakage flux interference to UAV equipment.

[0072] To more intuitively demonstrate the omnidirectional wireless power transfer performance of the proposed system, the resistive load was replaced with an LED light in the experiment. Since LED lights require less power, the DC input voltage of the system was reduced to 30V for testing. The omnidirectional wireless power transfer experimental demonstration effect is as follows: Figure 11 As shown, the LED lights up with essentially the same brightness under various positions and angular offsets of the receiving coil. These experimental results further demonstrate that the proposed system possesses excellent omnidirectional wireless power transmission performance.

[0073] This invention proposes a wireless power transmission system for unmanned aerial vehicles (UAVs) based on a three-phase solenoid coil and a rotating magnetic field. Regardless of the position or angle of the receiving coil, the system's output power exceeds 170.1W, and its transmission efficiency exceeds 72.3%. The proposed system has the following advantages:

[0074] 1) The proposed three-phase solenoid transmitting coil mainly generates a horizontal magnetic field and hardly generates a vertical magnetic field, which can greatly reduce the leakage flux interference to UAV equipment.

[0075] 2) The solenoid receiving coil is wound on the drone landing gear. Compared with the traditional circular coil structure, it has advantages such as not occupying extra installation space, not increasing the drone's flight drag, and not obstructing the drone's view below.

[0076] 3) A rotating magnetic field is generated by exciting a current with a 120° phase difference in a three-phase solenoid coil, thereby realizing omnidirectional wireless power transmission at any position and angle in a simple way.

[0077] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "rotation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-leakage magnetic flux interference omnidirectional power transfer unmanned aerial vehicle wireless charging system, characterized in that, The system includes a transmitting module mounted on a wireless charging platform and a receiving module mounted on a drone. The transmitting module consists of an A-phase solenoid transmitting coil, a B-phase solenoid transmitting coil, and a C-phase solenoid transmitting coil, wherein each phase solenoid transmitting coil includes two arc-shaped solenoid coils, and the three phase solenoid transmitting coils are evenly distributed on the same plane to form a complete circumference. The drone includes a landing gear. The receiving module includes two receiving coils, which are respectively wound around the two legs of the drone's landing gear. The A-phase solenoid transmitting coil includes two arc-shaped solenoid coils, A1 and A2, connected in series; the B-phase solenoid transmitting coil includes two arc-shaped solenoid coils, B1 and B2, connected in series; the C-phase solenoid transmitting coil includes two arc-shaped solenoid coils, C1 and C2, connected in series. In the transmitting module, six arc-shaped solenoid coils are evenly distributed on the same plane to form a complete circle, wherein: With the center of the circle facing outwards, the left and right ends of the A1 arc-shaped solenoid coil are respectively adjacent to the right end of the C2 arc-shaped solenoid coil and the left end of the B2 arc-shaped solenoid coil. The left and right ends of the A2 arc solenoid coil are adjacent to the right end of the C1 arc solenoid coil and the left end of the B1 arc solenoid coil, respectively. The right end of the B2 arc solenoid coil is immediately adjacent to the left end of the C1 arc solenoid coil, and the left end of the C2 arc solenoid coil is immediately adjacent to the right end of the B1 arc solenoid coil.

2. The omnidirectional power transfer drone wireless charging system with low leakage flux interference according to claim 1, characterized in that, Each arc-shaped solenoid coil has an arc of 60°.

3. The low-leakage magnetic flux interference omnidirectional power transfer UAV wireless charging system according to claim 1, characterized in that, The arc-shaped solenoid coil includes an arc-shaped magnetic core and a coil winding spirally wound on the arc-shaped magnetic core.

4. The low-leakage magnetic flux interference omnidirectional power transfer UAV wireless charging system according to claim 1, characterized in that, In the transmitting module, the phase difference of the excitation current between the three-phase solenoid transmitting coils is 120°, wherein: When ωt = 0, the synthesized magnetic field inside the launch module points in the positive y-axis direction; When ωt = π / 2, the synthesized magnetic field inside the launch module points in the positive x-axis direction; When ωt = π, the synthesized magnetic field inside the launch module points in the negative y-axis direction; When ωt = 3π / 2, the synthesized magnetic field inside the launch module points in the negative x-axis direction; Where ω represents the angular frequency of the excitation current, and t represents time.

5. The omnidirectional power transfer drone wireless charging system with low leakage flux interference according to claim 1, characterized in that, The two receiving coils are connected in series.

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