A new automatic charging method and device for unmanned aerial vehicle

Abstract

The present invention discloses a new automatic charging method and device for unmanned aerial vehicles. A single-chip microcomputer is used to generate a PWM signal, which is then passed through an inverter to generate 4 PWM waves, and then the 4 MOS tubes in the full-bridge inverter circuit are driven by a driving circuit to convert direct current into high-frequency alternating current. A bilateral LCC resonant compensation network is adopted to improve the transmission efficiency and enhance the anti-offset type of the system to a certain extent. The coupling coil adopts a three-coil structure, and the interval between the transmitting coil and the receiving coil is 5cm. When the coil is offset within a specific range, the output of the coupling device will not be affected by the coupling change or the impact is small. The battery management system can display the power of each lithium battery in real time, adopts a constant voltage charging method, and automatically sleeps after being fully charged.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle charging, and in particular to a new unmanned aerial vehicle automatic charging method and device. Background Art

[0002] Drones entered a period of rapid growth in the early 21st century, and gradually expanded from the military field to the civilian field, such as farmland operations, filming, logistics distribution, and inspections. At present, drones have two main flight power modes: fuel-powered flight and battery-powered flight. Compared with the former, drones using battery-powered flight mode have a simple structure, low cost, and safety, but are limited by battery capacity and have a short flight time, usually 20-30 minutes. Although increasing battery capacity can help increase the flight time of drones, it is limited by battery technology and production costs, and the increase in flight time is limited, and it cannot fundamentally solve the problem of long-term operation of drones. A more feasible strategy is to automatically charge the drone.

[0003] Wireless charging technology refers to a technology that directly converts electrical energy into electromagnetic waves, light waves, sound waves, etc., and transfers energy from the power source to the load through space without wires or other physical contact. Therefore, it is also called non-contact power transmission technology. This technology achieves complete electrical isolation between the power source and the load, and has incomparable advantages over traditional power transmission methods such as safety, reliability, and flexibility. Therefore, it has attracted widespread attention from scholars at home and abroad.

[0004] Magnetic coupling inductive wireless charging mainly uses electromagnetic induction coupling to transfer energy in one direction. The transmitter and receiver are not connected to each other. The energy is transferred from the transmitter to the receiver through the mutual inductance between the coils of the transmitter and receiver. A device similar to a loosely coupled transformer includes a transmitting coil and a receiving coil. When the RF signal is loaded on the transmitting coil, an induced current will flow through the receiving coil. The two work by mutual inductance. The charging efficiency of wireless charging is closely related to the alignment of the transmitting coil and the receiving coil and the distance between the two coils. When the receiving coil is installed on the drone, the distance is certain. Improving the system's anti-deviability is very important to ensure charging efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a new automatic charging method and device for unmanned aerial vehicles, aiming to solve the problem that the battery capacity carried by existing unmanned aerial vehicles limits their flight time. To achieve the above purpose, the present invention adopts a new automatic charging method and device for unmanned aerial vehicles, including a transmitting end and a receiving end.

[0006] The transmitting end includes a single chip microcomputer, a driving circuit, an inverter circuit, two transmitting coils connected in series and a primary resonance compensation network.

[0007] The single chip microcomputer is used to generate a PWM signal.

[0008] The driving circuit is used to drive the four MOS tubes in the full-bridge inverter circuit.

[0009] The inverter circuit is used to convert direct current into high-frequency alternating current;

[0010] The receiving end includes a receiving coil, a secondary side resonance compensation network, a rectifier circuit and a battery management part.

[0011] The transmitting coil, the receiving coil, the primary resonance compensation network and the secondary resonance compensation network constitute a coupling device, which is used to improve the transmission efficiency and enhance the anti-deviation type of the system to a certain extent;

[0012] The rectifier circuit is used to rectify and filter the electric energy received by the receiving end;

[0013] The battery management part is used to display the power level of each lithium battery in real time, and adopts a constant voltage charging method, and automatically sleeps after being fully charged.

[0014] Wherein, the transmitting end also includes a power supply circuit, and the power supply circuit is used to power the driving circuit and the inverter circuit.

[0015] The battery management unit includes a front-end sampling circuit, a charge and discharge and current sampling circuit, an STM32 control circuit, a battery module and an integrated serial port LCD screen;

[0016] The front-end sampling circuit is used to collect output and input electrical data of the battery module;

[0017] The charging and discharging and current sampling circuit is used to charge and discharge the battery module and collect the charging and discharging current of the system;

[0018] The STM32 control circuit is used to output a control signal to BQ76920;

[0019] The battery module is used to provide power to the drone;

[0020] The integrated serial port LCD screen is used to display various parameters of the battery.

[0021] The transmitting coil and the ferrite core 1 placed and tightly fitted directly below the transmitting coil constitute a transmitting device.

[0022] The transmitting coil is composed of a large rectangular planar coil and a small planar spiral coil, and the two coils are connected in series in reverse.

[0023] A new automatic charging method for drones, comprising the following steps:

[0024] The microcontroller generates a PWM signal;

[0025] After passing through the inverter, 4 PWM waves are generated;

[0026] The driving circuit drives the four MOS tubes in the full-bridge inverter circuit respectively to convert DC power into high-frequency AC power.

[0027] The electrical energy is transmitted to the receiving end through the coupling device;

[0028] After passing through the rectifier and filter circuit, it is converted into direct current;

[0029] The battery management part manages the charging of the battery module.

[0030] A new automatic charging method and device for unmanned aerial vehicles of the present invention utilizes a single-chip microcomputer to generate a PWM signal, generates 4 PWM signals after passing through an inverter, and then drives the 4 MOS tubes in the full-bridge inverter circuit respectively through a driving circuit to convert direct current into high-frequency alternating current. A bilateral LCC resonant compensation network is adopted, which improves the transmission efficiency while also enhancing the anti-offset type of the system to a certain extent. The coupling coil adopts a three-coil structure, with a spacing of 5cm between the transmitting coil and the receiving coil. When the coil is offset within a specific range, the output of the coupling device will not be affected by the coupling change or the impact is small. The battery management system can display the power of each lithium battery in real time, adopts a constant voltage charging method, and automatically sleeps after being fully charged. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a circuit diagram of the dual LCC resonance compensation structure of the present invention.

[0033] Figure 2 It is a schematic structural diagram of the coupling device of the present invention.

[0034] FIG. 3( a ) is a coupled coil model of the present invention.

[0035] FIG3( b ) is a simplified model of the present invention. Figure 4 It is the leakage inductance equivalent circuit of the dual LCC resonant compensation network of the present invention.

[0036] Figure 5It is the double-sided LCC resonant cavity constant voltage mode equivalent circuit of the present invention.

[0037] Figure 6 It is a system structure block diagram of the present invention.

[0038] Figure 7 It is a circuit diagram of the full-bridge inverter circuit of the present invention.

[0039] Figure 8 is a circuit diagram of a driving circuit of the present invention.

[0040] Fig. 9 It is a simulation effect diagram of the coupling device of the present invention.

[0041] Fig.10 It is the principle diagram of BQ76920 battery power detection of the present invention.

[0042] Fig.11 It is the corresponding address diagram of each string of lithium batteries of the present invention.

[0043] Fig.12 It is a schematic diagram of the charging and discharging circuit of the present invention.

[0044] Fig.13 It is a flow chart of the novel automatic charging method of unmanned aerial vehicle of the present invention.

[0045] Fig.14 It is the resonance condition and output voltage diagram of the T-type circuit of the present invention to achieve constant voltage output.

[0046] In the figure: 1- ferrite core, 2- secondary coil, 3- first primary coil, 4- second primary coil, 5- air gap. DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0048] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0049] The present invention provides a new automatic charging method and device for unmanned aerial vehicles, including a transmitting end and a receiving end.

[0050] The transmitting end includes a single chip microcomputer, a driving circuit, an inverter circuit, two transmitting coils connected in series and a primary resonance compensation network.

[0051] The single chip microcomputer is used to generate a PWM signal.

[0052] The driving circuit is used to drive the four MOS tubes in the full-bridge inverter circuit.

[0053] The inverter circuit is used to convert direct current into high-frequency alternating current;

[0054] The receiving end includes a receiving coil, a secondary side resonance compensation network, a rectifier circuit and a battery management part.

[0055] The transmitting coil, the receiving coil, the primary resonance compensation network and the secondary resonance compensation network constitute a coupling device, which is used to improve the transmission efficiency and enhance the anti-deviation type of the system to a certain extent;

[0056] The rectifier circuit is used to rectify and filter the electric energy received by the receiving end;

[0057] The battery management part is used to display the power level of each lithium battery in real time, and adopts a constant voltage charging method, and automatically sleeps after being fully charged.

[0058] Furthermore, the transmitting end also includes a power supply circuit, and the power supply circuit is used to power the driving circuit and the inverter circuit.

[0059] Furthermore, the battery management part includes a front-end sampling circuit, a charge and discharge and current sampling circuit, an STM32 control part circuit, a battery module and an integrated serial port LCD screen;

[0060] The front-end sampling circuit is used to collect output and input electrical data of the battery module;

[0061] The charging and discharging and current sampling circuit is used to charge and discharge the battery module and collect the charging and discharging current of the system;

[0062] The STM32 control circuit is used to output a control signal to BQ76920;

[0063] The battery module is used to provide power to the drone;

[0064] The integrated serial port LCD screen is used to display various parameters of the battery.

[0065] For further information, see Figure 1 The transmitting coil and the ferrite core 1 placed and tightly fitted directly below the transmitting coil constitute a transmitting device.

[0066] For further information, see Figure 1 The transmitting coil is composed of a large rectangular planar coil and a small planar spiral coil, and the two coils are connected in series in reverse.

[0067] See also Fig.13 ,A new automatic charging method for drones, including the following steps,

[0068] S601: MCU generates PWM signal;

[0069] S602: Generate 4 PWM signals after passing through the inverter;

[0070] S603: The driving circuit drives the four MOS tubes in the full-bridge inverter circuit respectively to convert the DC power into a high-frequency AC power.

[0071] In this embodiment,

[0072] 1. PWM signal generation and dead time setting

[0073] Use channel 1 and its complementary channel of the advanced timer TIM1 of the STM32 microcontroller as waveform output channels, and select the PA8 and PB13 pins accordingly. The frequency of the PWM signal is determined by the TIMX_ARR register, and the duty cycle is determined by the TIMX_CCR register. The PWM signal frequency F= TIM_CLK / {(ARR+1)*(PSC+1)}. When the machine cycle of the STM32 microcontroller is 72MHz, the microcontroller generates a PWM signal with a frequency of 83.3KHz and a duty cycle of 50%. In order to avoid the MOS tubes in the full-bridge inverter from being turned on at the same time, the PWM signal should be set with a dead time. Dead time setting: controlled by the bit DTG[7:0] in the register "TIM1 and TIM8 brake and dead zone register TIMX_BDTR". The dead time set by the system is 1us.

[0074] 2. Bilateral LCC resonant compensation network

[0075] Typically, the circuit diagram of a wireless charging system based on a bilateral LCC resonant compensation network is as follows: Figure 1 As shown, L p , L s are the self-inductance of the primary coil and the secondary coil 2 of the loosely coupled transformer, M is the mutual inductance of the two coils; the series compensation inductor L1 and the parallel capacitor C f1 and the series capacitor C1 form the primary side LCC compensation network; similarly, the secondary side LCC resonant compensation network consists of L2, Cf2 and C2; U in is the DC input voltage of the inverter front end; U AB , u ab and I1, I2 are the input, output voltage and current vectors of the resonant compensation network respectively; U O ,I O are the system output voltage and current respectively; Q1-Q4 are primary inverter MOS tubes, and D1-D4 are secondary rectifier diodes. The equivalent turns ratio n and coupling coefficient k between the transmitting coil and the receiving coil can be expressed as:

[0076]

[0077]

[0078] In this system, the equivalent turns ratio n of the coupling structure is 1.

[0079] like Figure 2 As shown, the transmitting device is composed of a transmitting coil and a ferrite core 1 placed just below the transmitting coil and tightly fitted. The transmitting coil is composed of a large rectangular planar coil and a small planar spiral coil, and the two coils are connected in series in reverse. The receiving device is composed of a rectangular coil and a ferrite core 1, and is installed at the bottom of the UAV landing gear; the air gap 5 between the transmitting device and the receiving device is 50mm.

[0080] The circuit model of the coupling device is shown in Figure 3, where L Q is the self-inductance of the first primary coil 3, and is the self-inductance of the second primary coil 4, M TS and M QS are the mutual inductances of the two primary coils and the secondary coil 2, M QT is the mutual inductance between the two primary coils. The model in Figure 3(a) is simplified, and the equivalent self-inductance of the primary coil is L P The mutual inductance between the primary and secondary coils 2 is represented by M, and the relationship is shown in equation (2). After simplification, the model in Figure 3 (b) is obtained, which forms the following: Figure 1 The coupling device shown.

[0081] L P =L Q +L T -2M QT

[0082] M=M Qs —M TS (2)

[0083] 3. Circuit constant voltage output

[0084] In order to achieve a constant voltage output of the bilateral LCC resonant network that is independent of the load, a T-type circuit is used to analyze the resonant cavity, as shown in Table 1. Figure 4 The leakage inductance equivalent circuit shown in the figure has a compensation capacitor and leakage inductance (C1, L1) in series with the primary side of the resonant cavity. S1 ) can be equivalent to (L CV1 , C cV1 ), the secondary side series compensation capacitor and leakage inductance (C′2, L′ S2 ) can be equivalent to (L′ CV2 , C′ CV2 ), thus forming Figure 5 The three T-circuits shown are connected in series.

[0085] Fig.14 The equivalent variable can be expressed by formula (3), where ω CV is the resonant angular frequency of the double-sided LCC resonant cavity in constant pressure mode, and ω CV =2πf CV :

[0086]

[0087]

[0088] according to Fig.14 The analysis of the constant voltage output characteristics of the T-type circuit given in the figure shows that to make the compensation network output a constant voltage, Figure 5 The three T-type compensation networks should all meet the conditions for the constant voltage output of the corresponding T-type compensation network:

[0089]

[0090] Figure 5 The output voltage U of the resonant compensation network that realizes constant voltage output independent of load CV It can be expressed as:

[0091]

[0092] It can be seen that the bilateral LCC compensation network can achieve constant voltage output.

[0093] The present invention proposes a magnetic coupling induction wireless charging system for small drones, which uses a non-physical contact method to transmit electrical energy from the transmitter to the receiver, reducing manual intervention and thus increasing the flight time of the drone. The structural block diagram of the small drone wireless charging system of the present invention is shown in FIG. Figure 7As shown, it includes a transmitting end and a receiving end. The transmitting end includes a single chip microcomputer, a driving circuit, a power supply circuit, an inverter circuit, two transmitting coils connected in series, and a primary resonance compensation network. The receiving end includes a receiving coil, a secondary resonance compensation network, a rectifier circuit, and a battery management part. Among them, the transmitting coil, the receiving coil and the resonance compensation network constitute a coupling device. The battery management part includes a front-end sampling circuit, a charging and discharging and current sampling circuit, an STM32 control part circuit, a battery module, and an integrated serial port LCD screen.

[0094] The basic principle of wireless charging is to pass a high-frequency alternating current through the transmitting coil, thereby generating a changing magnetic field around it, completing the transformation from electric to magnetic. After the changing magnetic field is coupled with the receiving coil, an electromotive force will be induced on the receiving coil, completing the transformation from magnetic to electric, and power transmission can be achieved through non-direct contact. In order to realize wireless charging of small drones, it is necessary to pass a high-frequency alternating current through the transmitting coil of the transmitting end, so the embodiment of the present invention adopts Figure 7 The inverter circuit shown in the figure is used to convert direct current into high-frequency alternating current. The inverter circuit used in the present invention is a full-bridge inverter circuit, which is composed of a pair of bridge arms formed by MOS tubes Q1 and Q4, and a pair of bridge arms formed by Q2 and Q3. Q1 and Q4 are turned on and off at the same time; Q2 and Q3 are turned on and off at the same time. The driving signals of Q1 (Q4) and Q2 (Q3) are complementary, that is, when Q1 and Q4 have driving signals, Q2 and Q3 have no driving signals, and vice versa. The two pairs of bridge arms are alternately turned on for 180°.

[0095] In order for the full-bridge inverter circuit in the system to complete the conversion from DC to AC, a drive signal is required for each of the four MOS tubes in the inverter circuit. This system uses the STM32 microcontroller to generate PWM to drive each MOS tube in the inverter circuit. However, the PWM generated by the STM32 microcontroller is not enough to drive the MOS tube.

[0096] Therefore, this system design adopts Figure 8 The driving circuit shown in the figure is composed of a 74LS04 inverter and two IR2110 chips and their peripheral circuits. The 83.3KHz PWM signal output by the STM32 microcontroller is converted into 4 PWMs through the 74LS04 inverter, of which two PWMs are 180° out of phase with the other two PWMs. The 4 PWMs output by the 74LS04 are connected to two IR2110 chips respectively, and the two PWMs on the same IR2110 chip are 180° out of phase. The two IR2110 chips isolate and amplify the driving signal, and respectively drive the 4 MOS tubes in the full-bridge inverter circuit, so that the above two pairs of bridge arms are alternately turned on, converting DC into high-frequency AC.

[0097] Coupling device above Figure 2As shown, the first primary coils 3 and 2 at the bottom are transmitting coils, and the secondary coil 2 at the top is a receiving coil. The three coils are coaxial, and the transmitting coil and the receiving coil are spaced 50 mm apart. The coils in the embodiments of the present invention are all wound with Litz wire, wherein the first primary coil 3 and the receiving coil are planar rectangular spiral coils, and the primary coils are planar spiral coils, with a 1 mm interval between the wires. The first primary coil 3 and the primary coil are on the same plane, and the inner diameter of the first primary coil 3 is greater than the outer diameter of the primary coil 3. A flat ferrite core 1 is provided below the first primary coil 3 and the primary coil 3, and the size of the core is the same as that of the first primary coil 3; a flat core is also provided above the secondary coil 2, and the size of the core is the same as that of the receiving coil. The magnetic cores in this design all use ferrite cores 1, and the magnetic cores fit tightly with the coils.

[0098] When the primary coil and the secondary coil 2 are misaligned, the mutual inductance M QS and M TS will be reduced if M is within a certain range of misalignment. QS and M TS If the magnitude of the decrease is the same, then the difference between them is assumed to be M, that is, M = M QS -M TS , can be kept constant. Therefore, when the coil is offset within a specific range, the output of the coupling device will not be affected by the coupling change or the impact is small, that is, the system's anti-offset performance can be improved. Fig. 9 This is a simulation effect diagram.

[0099] like Fig.10 As shown, BQ76920 is set to 4S lithium battery management mode, which can detect the power of each battery separately and communicate with STM32 through analog IIC; Fig.11 It is the corresponding address information when detecting each lithium battery.

[0100] When the battery needs to be charged, the current flows from bottom to top. When CHG is at a high level, the lithium battery can be charged regardless of whether DSG is high or low. Similarly, when the lithium battery needs to be discharged, the current flows from top to bottom. When DSG is at a high level, the lithium battery can be discharged regardless of whether CHG is high or low. The circuit schematic is shown in the figure. Fig.12 shown.

[0101] The present invention proposes a magnetic coupling induction wireless charging system for a small unmanned aerial vehicle, which uses a single-chip microcomputer to generate a PWM signal, generates 4 PWM waves after passing through an inverter, and then drives the 4 MOS tubes in the full-bridge inverter circuit respectively through a driving circuit to convert direct current into high-frequency alternating current. The bilateral LCC resonant compensation network is adopted, which improves the transmission efficiency and enhances the anti-offset type of the system to a certain extent. The coupling coil adopts a three-coil structure, and the interval between the transmitting coil and the receiving coil is 5cm. When the coil is offset within a specific range, the output of the coupling device will not be affected by the coupling change or the impact is small. The battery management system can display the power of each lithium battery in real time, adopts a constant voltage charging method, and automatically sleeps after being fully charged.

[0102] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A new automatic charging device for drones, characterized in that: Including the transmitter and the receiver, The transmitting end includes a single chip microcomputer, a driving circuit, an inverter circuit, two transmitting coils connected in series and a primary resonance compensation network. The single chip microcomputer is used to generate a PWM signal. The driving circuit is used to drive the four MOS tubes in the full-bridge inverter circuit. The inverter circuit is used to convert direct current into high-frequency alternating current; The receiving end includes a receiving coil, a secondary side resonance compensation network, a rectifier circuit and a battery management part. The transmitting coil, the receiving coil, the primary resonance compensation network and the secondary resonance compensation network constitute a coupling device, which is used to improve the transmission efficiency and enhance the anti-deviation type of the system to a certain extent; The rectifier circuit is used to rectify and filter the electric energy received by the receiving end; The battery management part is used to display the power of each lithium battery in real time, and adopts a constant voltage charging method, and automatically sleeps after being fully charged; The transmitting coil and a ferrite core placed directly below the transmitting coil and in close contact form a transmitting device; The transmitting coil is composed of a large rectangular planar coil and a small planar spiral coil, and the two coils are connected in series in reverse order; The driving circuit is composed of a 74LS04 inverter and two IR2110 chips and their peripheral circuits; The coupling coil adopts a three-coil structure, with a 5cm interval between the transmitting coil and the receiving coil; The single chip microcomputer generates a PWM signal, which is then passed through an inverter to generate four PWM waves, which are then passed through the drive circuit to drive four MOS tubes in the full-bridge inverter circuit respectively, converting direct current into high-frequency alternating current.

2. The new automatic charging device for unmanned aerial vehicles as claimed in claim 1, characterized in that: The transmitting end also includes a power supply circuit, and the power supply circuit is used to power the driving circuit and the inverter circuit.

3. The new automatic charging device for unmanned aerial vehicles as claimed in claim 1, characterized in that: The battery management part includes a front-end sampling circuit, a charge and discharge and current sampling circuit, an STM32 control part circuit, a battery module and an integrated serial port LCD screen; The front-end sampling circuit is used to collect output and input electrical data of the battery module; The charging and discharging and current sampling circuit is used to charge and discharge the battery module and collect the charging and discharging current of the system; The STM32 control circuit is used to output a control signal to BQ76920; The battery module is used to provide power to the drone; The integrated serial port LCD screen is used to display various parameters of the battery.

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