Unmanned aerial vehicle wireless charging system with undercarriage as receiving coil and control method thereof

Abstract

The invention relates to the technical field of unmanned aerial vehicle charging, in particular to an unmanned aerial vehicle wireless charging system with an undercarriage as a receiving coil and a control method thereof. The undercarriage body of the unmanned aerial vehicle is directly used as a structural supporting piece and a wireless charging receiving coil, so that the additional weight of the unmanned aerial vehicle during wireless charging is fundamentally avoided, the additional space of the vehicle body is not occupied, the aerodynamic configuration is not influenced, and the sight lines of an airborne camera and a sensor are not interfered; by adopting two mutually independent and electrically isolated receiving coils composed of a left undercarriage and a right undercarriage and cooperating with a mode decision and control method of a transmitting end, when horizontal deviation exists in landing of the unmanned aerial vehicle, a single-coil working mode in which double coils are connected in parallel or one side with relatively strong coupling can be automatically selected, circulation loss caused by unbalanced coupling is effectively reduced, and the reliability of the unmanned aerial vehicle is improved. The tolerance of the system to landing offset is remarkably improved, and high charging efficiency can still be kept under the condition that high-precision positioning assistance is not needed.

Description

Technical Field

[0001] This invention relates to the field of drone charging technology, and in particular to a wireless charging system for drones that uses the landing gear as a receiving coil and its control method. Background Technology

[0002] Drones are increasingly used in logistics delivery, inspection and monitoring, agricultural plant protection, and emergency rescue. However, the flight time of small and medium-sized commercial drones is generally between 20 and 40 minutes, which has become a major bottleneck restricting their long-term operation. Simply increasing the battery capacity would increase the weight of the drone, affecting flight performance and handling stability, and therefore is not a feasible solution.

[0003] Wireless charging technology provides an effective way to extend the flight time of drones. In the existing wireless charging technology for drones, the receiving coil is usually installed as an additional component on the drone fuselage or landing gear. This method has the following drawbacks: (1) Increased weight: The additional receiving coil and its insulation and fixing structure will increase the take-off weight of the drone, which will directly affect the flight time and payload capacity; (2) Affected aerodynamic performance: The external coil may change the shape of the drone, increase wind resistance, and affect flight stability; (3) Interference with airborne equipment: The additional coil may block the view of key equipment such as cameras and sensors. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a wireless charging system for drones with landing gear as the receiving coil and its control method. This solves the technical problem in existing wireless charging technologies for drones, where the receiving coil is usually installed as an additional component on the drone fuselage or landing gear, thereby increasing the drone's weight, affecting aerodynamic performance, and interfering with onboard equipment.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a wireless charging system for unmanned aerial vehicles (UAVs) with the landing gear body serving as a receiving coil, comprising: The ground-based launch unit, located on the UAV landing platform, includes a double-D-type launch coil for generating an alternating magnetic field; The onboard receiving unit installed on the drone body includes at least one of a left receiving coil and a right receiving coil. The left receiving coil is made of conductive material and forms a closed loop, serving as the left landing gear of the drone. The right receiving coil is made of conductive material and forms a closed loop, serving as the right landing gear of the drone. The left or right receiving coil generates an induced current under the action of an alternating magnetic field to charge the drone battery. The receiver control module is connected to the left and right receiving coils and selects at least one of them for charging control.

[0006] Preferably, the left and right receiving coils are rectangular rings, and their loop area is related to the size of the UAV fuselage and electromagnetic coupling requirements. Both the left and right receiving coils are within the projection range of the UAV fuselage.

[0007] Preferably, when the UAV is charging on the UAV landing platform, the angle between the left and right receiving coils and the vertical plane of the plane containing the alternating magnetic field does not exceed 25°.

[0008] Preferably, the dual D-type transmitting coil is composed of two D-shaped coils of the same shape connected in parallel.

[0009] Preferably, the X-axis dimension of the D-shaped coil is greater than the sum of the distance between the left and right receiving coils in the X direction and a preset allowable offset in the X-axis direction, and the Y-axis dimension of the D-shaped coil is greater than the sum of the projected lengths of the left and right receiving coils in the Y direction and a preset allowable offset in the Y-axis direction.

[0010] Preferably, a plurality of ferrite magnetic strips for guiding magnetic lines of force are arranged below the dual D-type transmitting coil, and the plurality of ferrite magnetic strips are evenly arranged along the Y-axis direction.

[0011] Preferably, the length L and width W of the D-shaped coil satisfy the following conditions: .

[0012] Preferably, the left receiving coil and the right receiving coil are independent of each other and electrically isolated.

[0013] A charging control method for a wireless charging system for unmanned aerial vehicles (UAVs), the charging control method comprising: S1, with the dual D-type transmitting coils started in low-power mode, measures were taken of the maximum power when the left receiving coil operated alone. Maximum power when the right receiving coil operates alone Based on the difference between the two and the preset rules, it selects to enter one of the following modes: dual-coil parallel operation mode, left coil single-mode operation mode, and right coil single-mode operation mode. S2. Real-time acquisition of voltage and current at the rectifier output of the airborne receiving unit to execute the MPPT algorithm, and simultaneous acquisition of voltage and current at the battery end to execute the charging management algorithm. The smaller value between the duty cycle output by the MPPT algorithm and the duty cycle output by the charging management algorithm is taken as the final duty cycle of the power converter.

[0014] Preferably, the preset rule is: like Then it enters the dual-coil parallel working mode; like Then it enters the single-mode working mode of the left coil. like Then it enters the right coil single-mode working mode; in, This is a preset threshold.

[0015] By employing the above technical solution, the present invention provides a wireless charging system for unmanned aerial vehicles (UAVs) that uses the landing gear as a receiving coil, and its control method, which has at least the following beneficial effects: 1. This invention constructs the drone landing gear body directly as a closed loop to simultaneously serve as a structural support and a wireless charging receiving coil. This fundamentally avoids the additional weight caused by adding coils and their insulation, fixing and connection structures to the drone. It does not occupy extra space in the fuselage, does not affect the aerodynamic shape, and does not interfere with the line of sight of the airborne camera and sensors. It significantly simplifies the airborne system structure and reduces manufacturing and maintenance costs.

[0016] 2. This invention employs two independent and electrically isolated receiving coils composed of left and right landing structures. Combined with the mode decision and control method at the transmitting end, when there is a horizontal deviation during UAV landing, it can automatically select the working mode of the dual coils in parallel or the single coil working mode of the stronger coupling side. This effectively reduces the circulating current loss caused by uneven coupling, significantly improves the system's tolerance to landing deviation, and can still maintain high charging efficiency without the need for high-precision positioning assistance.

[0017] 3. This invention uses hollow aluminum tubes to form the landing gear and receiving coil. While ensuring mechanical strength, the hollow structure reduces the impact of high-frequency skin effect. The large surface area of ​​the landing gear body enables natural heat dissipation, eliminating the need for additional heat dissipation devices. Combined with MPPT and charging management collaborative control, the smaller value of the duty cycle output by the two algorithms is used to achieve dynamic impedance matching and unify the charging requirements of the lithium battery. This ensures that the system always operates at the optimal efficiency point, further improving charging efficiency and system integration. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a structural block diagram of the wireless charging system for unmanned aerial vehicles (UAVs) of the present invention. Figure 2 This is a schematic diagram of the three-dimensional structure of the drone wireless charging system of the present invention; Figure 3 This is a schematic diagram showing the positions of the ground transmitting unit and the dual D-type transmitting coils of the present invention; Figure 4 This is a schematic diagram of the airborne receiving unit circuit structure of the present invention.

[0019] In the diagram: 1. Ground transmitting unit; 2. Airborne receiving unit; 3. Left landing gear; 4. Right landing gear; 5. Receiver control module; 6. Strip magnetic core. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This will allow for a full understanding of how the present application uses technical means to solve technical problems and achieve technical effects, and to facilitate its implementation.

[0021] To address the technical problems inherent in existing wireless charging technologies for drones, where the receiving coil is typically mounted as an add-on component on the drone fuselage or landing gear, leading to increased drone weight, reduced aerodynamic performance, and interference with onboard equipment, this invention provides a wireless charging system for drones where the landing gear itself serves as the receiving coil. Figures 1-3 As shown, a wireless charging system that uses the drone's landing gear as its receiving coil achieves high-efficiency wireless charging of the drone without increasing its weight. The system mainly consists of the following three parts: The first part is the ground-based transmitting unit 1, which is set on the UAV landing platform. It includes a double D-shaped transmitting coil for generating an alternating magnetic field. In order to charge the left and right receiving coils separately, the double D-shaped transmitting coil is composed of two D-shaped coils of the same shape connected in parallel, so that the left and right receiving coils can be charged independently. In order to maximize the coupling coefficient, mutual inductance and charging efficiency, the size of the D-shaped coil is further determined according to the UAV's take-off and landing deviation.

[0022] like Figure 3 As shown, the X-axis dimension (left-right direction, i.e., along the width of the D-shaped coil): In this embodiment, the projection of the receiving coil in the X-direction is only the diameter of the aluminum tube, which is negligible. Therefore, only the distance d between the left and right receiving coils in the X-direction is considered. Thus, the X-axis dimension of the D-shaped coil is greater than the sum of the distance between the left and right receiving coils in the X-direction and the preset allowable offset in the X-axis direction, i.e., the width of the D-shaped coil. satisfy: ,in, This is the allowable offset in the X-axis direction, which is the error in the X-axis direction when the drone lands.

[0023] Y-axis dimension (front-to-back direction, i.e., the direction perpendicular to the X-axis on the plane where the D-shaped coil is located, i.e., along the length of the D-shaped coil): The projected length of the receiving coil in the Y-direction is equal to the side length 'a' of the receiving coil. Therefore, the Y-axis dimension of the D-shaped coil is greater than the sum of the projected lengths of the left and right receiving coils in the Y-direction and the preset allowable offset in the Y-axis direction. That is, the length of the transmitting coil in the Y-direction satisfies: ,in, This represents the allowable offset in the Y-axis direction, which is the error in the Y-axis direction when the drone lands. If the drone's landing position exceeds this offset... and When the coupling coefficient decreases, the transmission power decreases with the square of the coupling coefficient when the X-direction is offset; when the Y-direction is offset, the coupling coefficients of the left and right receiving coils decrease synchronously.

[0024] In this embodiment, each D-shaped coil is wound with Litz wire; the diameter of the Litz wire should match the magnetic field frequency to reduce high-frequency skin effect and proximity effect losses, therefore its wire diameter... ,in, d is the diameter of the Litz line, and d is the skin depth. The magnetic field frequency, For the conductor's permeability, is the conductivity of the conductor.

[0025] In this embodiment, to further guide the magnetic field lines, reduce magnetic leakage, and enhance coupling, multiple strip-shaped magnetic cores 6 are arranged below the dual D-shaped transmitting coils to guide the magnetic field lines. These strip-shaped magnetic cores 6 are evenly arranged along the Y-axis, and their width in the X-axis direction is the same as that of the D-shaped coils. The strip-shaped magnetic cores 6 can be ferrite strips, such as... Figure 3 As shown.

[0026] For large-scale drone parking apron applications, the double D-shaped transmitting coil can be extended along the Y-axis to form an ultra-long double D-shaped transmitting coil. The magnetic field distribution of the D-shaped coil in the Y-axis has the characteristic of "uniformity in the middle and attenuation at both ends". If the length of the D-shaped coil along the Y-axis is L and the width along the Y-axis is W, the position where the magnetic field at the end of the D-shaped coil begins to significantly attenuate is about 0.9W-1.1W away from the end. When the length L and width W of the transmitting coil satisfy L / W≥5, the proportion of the uniform magnetic field distribution area is greater than 60%, preferably L / W=8~10, and the proportion of the uniform area is 75-80%, which can improve the utilization rate of the parking apron. Therefore, in this embodiment, the length L and width W of the D-shaped coil are set to satisfy... .

[0027] The second part is the onboard receiving unit 2 installed on the drone's fuselage, which includes at least one of a left receiving coil and a right receiving coil. For ease of description in this embodiment, the left and right receiving coils are referred to as receiving coils. The left receiving coil is made of conductive material and forms a closed loop, serving as the drone's left landing gear 3. The right receiving coil is also made of conductive material and forms a closed loop, serving as the drone's right landing gear 4. This closed loop can be a single turn. No other wire coils are needed on the drone. The left and right receiving coils generate an induced current under the action of an alternating magnetic field, ultimately completing the charging process. This allows the landing gear to achieve "dual-purpose functionality." The landing gear is an essential structural component of the drone, used for supporting landing. By designing it as a closed loop to form a wireless charging receiving coil, an induced current is generated under the action of an alternating magnetic field, thereby charging the drone's battery. Figure 2 As shown.

[0028] After the induced current is rectified by the resonant capacitor, it stores electrical energy in the battery under the action of the receiver control module 5, thereby realizing battery charging. This achieves true zero weight increase design on the basis of wireless charging. In this embodiment, in order to reduce weight while ensuring mechanical strength, the landing gear is made of hollow aluminum tube, thereby further utilizing its hollow structure to reduce the influence of high frequency skin effect.

[0029] Furthermore, the left and right receiving coils are rectangular rings, and their loop areas are determined based on the UAV's fuselage size and electromagnetic coupling requirements. Since the receiving coils are integrated into the landing gear, both the left and right receiving coils must be within the UAV's projected area. A typical medium-sized UAV's landing gear occupies approximately 250mm × 250mm of space; therefore, the side length of the receiving coils cannot exceed 250mm. The induced electromotive force of the receiving coils is proportional to their area; increasing the area improves the coupling coefficient, but too small an area leads to excessively low self-inductance, affecting matching with the transmitting coil. This self-inductance can be calculated using the formula for a single-turn rectangular ring. In the above formula, Let b be the length and width of the receiving coil, m0 be the permeability of free space, and r be the radius of the aluminum tube. The mutual inductance M is proportional to the area of ​​the receiving coil, while the self-inductance... The coupling coefficient increases with size but at a slower rate, therefore... It increases with increasing area, of which and The self-inductance of the receiving coil and the transmitting coil are respectively. Therefore, the upper limit of the rectangular ring-shaped loop area can be determined by the size of the UAV fuselage, and the lower limit can be determined according to the electromagnetic coupling requirements such as self-inductance and mutual inductance.

[0030] In this embodiment, to ensure the stability of the drone when parked, the drone landing platform is horizontal, and the direction of the alternating magnetic field is also horizontal. Of course, if the drone can be parked stably at other angles, the drone landing platform can also be set to other angles. If the alternating magnetic field generated by the dual D-type transmitting coils is horizontal, the magnetic coupling efficiency of the left and right receiving coils is highest when the drone is parked on the drone landing platform for charging, provided they are placed vertically. However, a completely vertical landing gear support area is too small, resulting in poor stability and a tendency for the drone to tip over during landing and parking. Appropriate outward tilting can significantly increase the support area and improve stability; the larger the tilt angle, the better the stability, but the magnetic coupling efficiency will decrease accordingly. The relationship declined, among which, This refers to the angle between the left and right receiving coils and the plane perpendicular to the alternating magnetic field. For example, if the alternating magnetic field is horizontal, then this vertical plane is perpendicular to the horizontal plane, i.e., it is a vertical plane. Therefore, in order to achieve a balance between stability requirements and charging efficiency, this embodiment ensures that the angle between the left and right receiving coils and the plane perpendicular to the plane containing the alternating magnetic field does not exceed 25°. This allows for sufficient stability while keeping the magnetic coupling loss below 10%, because the magnetic coupling loss at this point is... .

[0031] The third part is the receiver control module 5 connected to the left and right receiving coils. It is used to select at least one of the left and right receiving coils for charging control to maximize power. Under normal circumstances, the drone will land accurately, and a dual-coil parallel charging mode will be adopted. When the drone lands off course, causing a significant difference in coupling between the two receiving coils, the receiver control module 5 will automatically select the optimal receiving coil for charging, reducing circulating current loss and significantly improving the offset tolerance and energy transmission efficiency of the wireless charging system. It can further make the left and right receiving coils independent and electrically isolated from each other.

[0032] This embodiment also provides a charging control method for a wireless charging system for unmanned aerial vehicles, the charging control method including: Step S1: Coil detection and mode decision.

[0033] S101, the dual-D type transmitting coil is started in low-power mode, and a test current I1 is passed into the dual-D type transmitting coil; S102, the microcontroller controls the coil switch, and measures the maximum power of the left receiving coil when it is working alone. Maximum power when the right receiving coil operates alone ,in, and It can be relative to the rated power The relative value; S103, Comparison and And make a decision based on the difference between the two and the preset rules: like Then it enters the dual-coil parallel working mode; like Then it enters the single-mode working mode of the left coil. like Then it enters the right coil single-mode working mode; in, The preset threshold is preferably in the range of 0.2-0.4.

[0034] Step S2: MPPT and charging management coordinated control.

[0035] S201: Dual-loop sampling and calculation.

[0036] The microcontroller runs the MPPT algorithm to read the voltage Vin and current Iin at the output of the rectifier circuit in real time and calculates the current input power Pin = Vin × Iin. The microcontroller simultaneously runs the lithium battery charging management algorithm, reads the battery terminal voltage Vbat and current Ibat, and determines the current charging stage. S202: MPPT algorithm.

[0037] The current input power Pin(i) is compared with the input power Pin(i-1) of the previous cycle as follows: If Pin(i) > Pin(i-1), and the duty cycle adjustment direction in the previous cycle was increasing, then continue to increase the duty cycle Dmppt. If Pin(i) > Pin(i-1), and the duty cycle adjustment direction of the previous cycle is decreasing, then continue to decrease the duty cycle Dmppt; If Pin(i) < Pin(i-1), and the duty cycle adjustment direction in the previous cycle was increasing, then the duty cycle D_mppt should be decreased instead. If Pin(i) < Pin(i-1), and the duty cycle adjustment direction in the previous cycle was decreasing, then the duty cycle D_mppt should be increased instead. Record the current duty cycle Dmppt and power Pin(i) as the comparison benchmark for the next cycle; S203: Charging management algorithm.

[0038] First, determine the charging target and required output power based on the battery status using the following method: If the battery voltage Vbat < constant voltage threshold Vcv (e.g., 16V) and the constant voltage stage has not been reached, the battery is in the constant current charging stage. At this time, the charging power Preq = Icc × Vbat, where Icc is the set constant current value (e.g., 3A). If the battery voltage has reached Vcv, the battery enters the constant voltage charging stage. At this time, the charging power Preq = Vcv × Ibat, where Ibat is the battery current. Ibat gradually decreases. If Ibat decreases to the termination threshold Iterm (e.g., 0.1A), the charging is considered complete and the battery is ready to stop.

[0039] Finally, calculate the required duty cycle Dchg based on Preq; S204: Duty cycle comparison.

[0040] First, the microcontroller takes the smaller value, Dmin, of the duty cycle Dmppt output by the MPPT algorithm and the duty cycle Dchg output by the charging management algorithm as the final duty cycle of the power converter. In this embodiment, the power converter can be a Buck-boost converter. Then, the PWM output is updated to control the operation of the power converter.

[0041] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0042] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Since the above embodiments are substantially similar to the method embodiments, their descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0043] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A wireless charging system for unmanned aerial vehicles (UAVs) using the landing gear body as a receiving coil, characterized in that, include: The ground-based launch unit (1) located on the UAV landing platform includes a double-D type launch coil for generating an alternating magnetic field; The onboard receiving unit (2) installed on the body of the UAV includes at least one of a left receiving coil and a right receiving coil. The left receiving coil is made of conductive material and forms a closed loop, serving as the left landing gear (3) of the UAV. The right receiving coil is made of conductive material and forms a closed loop, serving as the right landing gear (4) of the UAV. The left or right receiving coil generates an induced current under the action of an alternating magnetic field to charge the UAV battery. The receiver control module (5) is connected to the left receiving coil and the right receiving coil, and selects at least one of them for charging control.

2. The wireless charging system for unmanned aerial vehicles according to claim 1, characterized in that, The left and right receiving coils are rectangular rings, and their loop area is related to the size of the UAV fuselage and electromagnetic coupling requirements. Both the left and right receiving coils are within the projection range of the UAV fuselage.

3. The wireless charging system for unmanned aerial vehicles according to claim 1, characterized in that, When the drone is charging on the drone landing platform, the angle between the left and right receiving coils and the vertical plane of the plane where the alternating magnetic field is located does not exceed 25°.

4. The wireless charging system for unmanned aerial vehicles according to claim 1, characterized in that, The dual-D type transmitting coil is composed of two identical D-shaped coils connected in parallel.

5. The wireless charging system for unmanned aerial vehicles according to claim 4, characterized in that, The X-axis dimension of the D-shaped coil is greater than the sum of the distance between the left and right receiving coils in the X direction and the preset allowable offset in the X-axis direction. The Y-axis dimension of the D-shaped coil is greater than the sum of the projected length of the left and right receiving coils in the Y direction and the preset allowable offset in the Y-axis direction.

6. The wireless charging system for unmanned aerial vehicles according to claim 4, characterized in that, Below the dual D-type transmitting coil, there are multiple strip magnetic cores (6) for guiding magnetic lines of force, and the multiple strip magnetic cores (6) are evenly arranged along the Y-axis.

7. The wireless charging system for unmanned aerial vehicles according to claim 4, characterized in that, The length L and width W of the D-shaped coil satisfy the following... .

8. The wireless charging system for unmanned aerial vehicles according to claim 1, characterized in that, The left and right receiving coils are independent and electrically isolated from each other.

9. A charging control method for a wireless charging system for a drone according to any one of claims 1-8, characterized in that, The charging control method includes: S1, with the dual D-type transmitting coils started in low-power mode, measures were taken of the maximum power when the left receiving coil operated alone. Maximum power when the right receiving coil operates alone Based on the difference between the two and the preset rules, it selects to enter one of the following modes: dual-coil parallel operation mode, left coil single-mode operation mode, and right coil single-mode operation mode. S2. Real-time acquisition of voltage and current at the rectifier output of the airborne receiving unit to execute the MPPT algorithm, and simultaneous acquisition of voltage and current at the battery end to execute the charging management algorithm. The smaller value between the duty cycle output by the MPPT algorithm and the duty cycle output by the charging management algorithm is taken as the final duty cycle of the power converter.

10. The charging control method according to claim 9, characterized in that, The preset rule is as follows: like Then it enters the dual-coil parallel working mode; like Then it enters the single-mode working mode of the left coil. like Then it enters the right coil single-mode working mode; in, This is a preset threshold.

Images