A magnetic coupling structure for wireless charging with strong anti-offset capability and strong coupling characteristics

Abstract

The application provides a magnetic coupling structure for wireless charging with strong anti-deviation capability, belongs to the technical field of power electronic magnetism, and can be specifically applied to unmanned aerial vehicles, intelligent robots and the like. The existing research on the magnetic coupling structure for unmanned aerial vehicles will affect the stable work of the unmanned aerial vehicles due to the problem of parking accuracy. The structure provided by the application comprises the following parts: a fixed layer, a ferrite matrix layer, a bipolar transmission platform and a hollow receiving coil integrated in the landing gear of the unmanned aerial vehicle. By adopting the structure of the application, the anti-deviation characteristic and the high magnetic flux coupling of the structure are realized by using the uniform annular horizontal magnetic field on the surface of the bipolar transmission coil. In addition, due to the characteristic that the magnetic fields in the central region of the bipolar transmission coil offset each other, the stray magnetic field of the abdomen of the unmanned aerial vehicle is greatly reduced. Finally, the application realizes a wireless charging magnetic coupling structure with high coupling coefficient and anti-deviation characteristic.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission, specifically relating to a magnetic coupling structure for wireless charging of drones with strong coupling and anti-offset characteristics. Background Technology

[0002] Wireless power transfer technology can efficiently and safely charge devices without contact, making it widely used in consumer electronics, electric vehicles, and passenger cars. Traditional drones still face the problem of limited battery life, which significantly impacts their operating time and range. Wireless power transfer technology can enhance drone endurance and enable unmanned and autonomous operation.

[0003] Wireless power transfer technologies often offer a high degree of spatial freedom. However, in UAV wireless power transfer systems, it is consistently difficult to achieve optimal alignment between the helipad and the UAV. This can affect the system's coupling coefficient, further reducing charging efficiency and impacting system stability. Therefore, enhancing the anti-misalignment performance of wireless power transfer systems is of great significance.

[0004] When a system experiences offset, its output current or voltage often changes. This phenomenon can be optimized through system control strategies or compensation topology design to stabilize the output voltage or current. However, the limitation on transmission efficiency caused by the change in coupling coefficient under offset conditions cannot be compensated for by the above methods. The design of the coupling structure can further address this problem. Currently, common magnetic coupling structures include circular coils, rectangular coils, and DD coils, but these structures have poor fault tolerance under offset conditions. Some scholars have proposed irregular structures such as the "I-I" type magnetic coupling structure, bipolar coil structure, and double orthogonal DD structure. These structures can better solve the system fluctuations of UAVs under rotational or horizontal offset, but they still have low efficiency and can only maintain system stability under single-direction offset or rotational offset. Summary of the Invention

[0005] This invention addresses the widespread offset problem in wireless power transmission systems for unmanned aerial vehicles (UAVs) by proposing a magnetic coupling structure suitable for wireless charging of UAVs and intelligent robots. This structure can reduce the decrease in coupling coefficient when the transmitter and receiver are offset, thereby ensuring good power transmission and stable transmission efficiency.

[0006] To achieve the above objectives, this invention proposes a magnetic coupling structure for wireless charging of unmanned aerial vehicles (UAVs) with strong anti-offset characteristics. The magnetic coupling structure comprises a bipolar transmitting platform and a receiving structure, characterized by: The launch platform includes a fixed plane, a shielding layer is disposed above the fixed plane, and a coil assembly is disposed above the shielding layer; The receiving structure includes a hollow receiving coil wound around the landing gear.

[0007] Furthermore, the coil assembly is made up of four sets of coils wound together, with each set of coils wound in alternating clockwise and counterclockwise directions.

[0008] Furthermore, the four sets of coils in the bipolar four-coil structure are connected in series, and each set of coils is wound in a single strand or multiple strands in a circular shape.

[0009] Furthermore, in the bipolar four-coil structure, the first and fourth sets of transmitting coils are wound with a single strand, while the second and third sets of transmitting coils are wound with two or more strands in parallel.

[0010] Furthermore, the launch platform generates a circular horizontal magnetic field, which can be controlled by changing the winding width of the coil group.

[0011] Furthermore, the hollow receiving coil of the receiving structure is made of three strands of 0.05mm×260 Litz wire wound in parallel.

[0012] Furthermore, the hollow receiving coil is wound around all four sides and connected in series to improve efficiency.

[0013] Furthermore, the hollow receiving coil is placed on the surface of the bipolar transmitting platform and is within the range of a horizontal magnetic field.

[0014] The beneficial effects of this invention are as follows: 1. The bipolar transmitting platform used in this invention has a circular horizontal magnetic field pointing towards the center and with adjustable width. The hollow receiving coil on the receiving side can make good use of the horizontal magnetic field generated by the transmitting coil, resulting in strong coupling between the transmitting and receiving ends of this magnetic coupling structure. Furthermore, thanks to the symmetry of the circular horizontal magnetic field of the bipolar transmitting platform, this structure has strong fault tolerance for both rotational and horizontal offsets.

[0015] 2. The hollow receiving coil on the receiving side proposed in this invention is integrated into the drone's support structure, which can significantly reduce wind resistance and the volume occupied by the receiving coil on the drone side. While achieving the above advantages, it maintains high charging efficiency. Furthermore, this structure is scalable and can be used in wireless power transmission schemes for intelligent robots. Attached Figure Description

[0016] Figure 1 This is a 3D model diagram of a magnetically coupled structure.

[0017] Figure 2 This is a schematic diagram of the topology of a wireless power transmission system.

[0018] Figure 3 This is a current flow diagram of a bipolar transmitter platform.

[0019] Figure 4 This is a schematic diagram of the magnetic field distribution within the space of the bipolar launch platform.

[0020] Figure 5 This is a schematic diagram of the magnetic field distribution within the space of a monopole coil transmitting platform.

[0021] Figure 6 This is a schematic diagram of the horizontal magnetic field lines of a bipolar launch platform.

[0022] Figure 7 It is a graph showing the changes in coupling coefficient and self-inductance at different rotation angles on the receiving side.

[0023] Figure 8 It is a graph showing the changes in coupling coefficient and self-inductance under lateral offset on the receiving side.

[0024] Figure 9 This is a schematic diagram of the prototype.

[0025] Figure 10 It is a curve showing the working characteristics when rotated 360°.

[0026] Figure 11 This is a curve showing the working characteristics under a lateral offset of 40mm. Detailed Implementation

[0027] Specific examples of the present invention will be described below with reference to the accompanying drawings, and the technical solutions of the present invention will be further described in detail. It should be understood that the specific embodiments described herein are merely intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0028] This invention includes, for example Figure 1 The diagram shows a wireless power transmission magnetic coupling structure suitable for drones or warehouse robots. The structure includes a fixed platform for the transmitting plane, a ferrite core matrix, a bipolar transmitting coil, and a receiving coil.

[0029] The overall structure of the drone wireless charging system is as follows: Figure 2 As shown, the energy transfer process is a DC power supply. U dc After passing through the inverter bridge module, it is converted into AC voltage. U in The energy is then eliminated by an LC resonant network to remove reactive power and filter out high-frequency components. The energy is then transmitted to the receiving end via magnetic field coupling, and then transferred to the rectifier bridge via the secondary LC resonant network, and finally to the output capacitor.C out After filtering, it is converted into DC current to charge the load.

[0030] The system topology is SS topology. When the system is in a resonant state, then: , in, ω 0 is the resonant frequency of the system. At this time, the resonant current on the primary side... I p Resonant current on the secondary side I s They are respectively: , in, U in The amplitude of the input voltage to the resonant cavity. M This refers to the mutual inductance between the primary and secondary coils. Specifically, when... R 1. R 2 is much smaller than R o At that time, the SS network can achieve a constant current source output that is approximately independent of the load.

[0031] During the winding of this bipolar coil structure, care should be taken to ensure that the current flows in the following direction: Figure 3 As shown, a ring-shaped horizontal magnetic field can be generated for coupling of the secondary receiving coil. Simultaneously, to enhance lateral anti-offset capability, the width of the horizontal magnetic field can be increased according to the length or width of the receiving coil. Figure 3 As shown in D.

[0032] A comparative analysis of stray magnetic fields between bipolar and unipolar coils, as shown in Figure 4. Figure 5 As shown, this verifies that bipolar coils, compared to monopolar coils, can effectively reduce stray magnetic fields, thereby minimizing the impact of magnetic fields on electronic components in the fuselage.

[0033] The cross-section of the magnetic field lines distribution in the vertical direction of the bipolar coil is as follows Figure 6 As shown in Figure 6, the bipolar coil has a strong horizontal magnetic field that is ring-shaped with a ring width of D, exhibiting good symmetry.

[0034] The transmission coils all use Litz wire instead of a single solid conductor. Compared to Litz wire, a single solid conductor results in significantly increased eddy current losses, which is detrimental to energy transmission. This hollow receiving coil can better utilize the horizontal magnetic field generated by the transmitting coil, resulting in strong coupling between the transmitting and receiving ends of this magnetic coupling structure. The coil structure is primarily designed for the receiving coil in a UAV wireless power transmission system. Considering the requirements for lightweight design and coil flexibility on the UAV receiving side, this paper selects three strands of 0.05mm × 260 Litz wire wound in parallel instead of a single strand of 0.05mm × 1040 Litz wire wound into the receiving coil.

[0035] Rotational offset tests were performed on the receiving coils, and the primary and secondary inductances, as well as the mutual inductance between them, were measured using an LCR analyzer. The measurement results are as follows: Figure 7 As shown, thanks to the symmetry of the receiving coil and the annular horizontal magnetic field of the circular bipolar transmitting platform, the self-inductance and mutual inductance of this structure are both less than 0.5% under the rotational offset test of 0-360°, and the coupling coefficient can reach more than 0.3.

[0036] Lateral offset tests were performed on the receiving coils, and the inductance of the primary and secondary sides, as well as the mutual inductance between them, was measured using an LCR analyzer. Experimental results show that within the lateral offset range of 0-6 cm, the self-inductance change is less than 0.5%, and the coupling coefficient can still be maintained above 0.2.

[0037] Meanwhile, to verify the anti-offset performance and strong coupling characteristics of this structure, a power transmission circuit and a detection circuit were built and integrated into the secondary control board. A TMS320F28335 DSP controller was used on both the transmitting and receiving sides for voltage and current data sampling and processing, as well as signal driving of the primary and secondary switching transistors. An IPD046N08N05 was used to build the inverter full-bridge on the primary side, and an ISG3202LA gallium nitride half-bridge chip was used to build the rectifier bridge on the secondary side. The circuit diagram is shown below. Figure 9 As shown in the table below: Reference Appendix Figure 10 The system has a transmission power of over 250W and an efficiency fluctuation of less than 1% within a rotational offset range of 0 to 360°, demonstrating good resistance to rotational offset.

[0038] Reference Appendix Figure 11Under lateral offset, the system coupling coefficient decreases with increasing offset distance. This indirectly leads to a decrease in system output efficiency and an increase in output current. When the offset reaches 4cm, the system output power reaches 370W, but the efficiency can still reach over 90%, further verifying the strong fault tolerance and strong coupling characteristics of the structure under lateral offset. Meanwhile, the power output can be controlled by a primary-side phase-shift frequency modulation scheme or a secondary-side impedance matching strategy.

[0039] In this embodiment, based on the SS resonant compensation network with a prototype design requirement of 52V input and 4.5A output, the magnetic coupling structure of the receiving coil with strong anti-offset coupling characteristics described in this invention was constructed and verified.

[0040] This invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as illustrative rather than restrictive, for example: 1) The applications of this magnetic coupling structure are not limited to wireless power transmission in UAVs; 2) The structure and dimensions of the receiving coil are not limited to those described in the embodiments; 3) The resonant compensation network used in the magnetic coupling structure is not limited to the SS topology. Therefore, the scope of this invention is indicated by the appended claims rather than the foregoing description. All variations falling within the meaning and scope of equivalent technical solutions of the claims are included within its scope.

Claims

1. A magnetic coupling structure for wireless charging of unmanned aerial vehicles (UAVs) with strong coupling and anti-offset characteristics, the magnetic coupling structure comprising a bipolar transmitting platform and a hollow receiving coil, characterized in that: The bipolar transmitting platform includes a fixed plane (0101), a ferrite matrix (0102) is arranged above the fixed plane (0101), and a reverse coil group (0104) and (0107) and a forward coil group (0105) and (0106) are arranged above the ferrite matrix (0102); The receiving structure includes a hollow receiving coil (0103) placed inside the landing gear.

2. The bipolar transmitting platform as described in claim 1 is characterized in that: a ferrite matrix is ​​included below the coil to focus the magnetic field, and the coil structure is made of four sets of coils.

3. The magnetic coupling structure for wireless charging of drones with strong anti-displacement characteristics as described in claim 2, characterized in that: The four coils are connected in series. After the connection, the current direction of the reverse coil group (0104) and (0107) is counterclockwise, and the current direction of the forward coil group (0105) and (0106) is clockwise.

4. The magnetic coupling structure with strong anti-displacement characteristics as described in claim 3, characterized in that: Each coil is wound in a circle, and the structure has a strong horizontal magnetic field and is distributed in a ring shape in three-dimensional space.

5. The magnetic coupling structure with anti-displacement characteristics as described in claim 4, characterized in that: The width of the circular horizontal magnetic field can be controlled by changing the width of the forward coil group (0105) and (0106), making it suitable for various types of UAV applications.

6. The magnetic coupling structure with strong coupling characteristics as described in claim 1, characterized in that: All receiving coils are hollow receiving coils. Considering the rigidity of the wire, the hollow coils are all made of three strands of 0.05mm×260 fine Litz wire wound in parallel (0103).

7. The magnetic coupling structure with strong coupling characteristics as described in claim 6, characterized in that: The hollow receiving coil is wound in series and is located above the (0105) and (0106) coils in the bipolar transmitting platform.

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