Multi-channel constant current output unmanned aerial vehicle hovering charging system and method

Abstract

The application discloses a multi-constant-current-output unmanned aerial vehicle hovering charging system, which comprises a charging control system; the charging control system comprises a sampling module, a Fourier transform module, a mutual inductance estimation module and a PI controller; the sampling module is used for sampling a current signal flowing through a transmitting coil; the Fourier transform module is used for performing Fourier transform on a primary-side current signal obtained through sampling to obtain different frequency current component signals; the mutual inductance estimation module is used for estimating mutual inductance between the transmitting coil and receiving coils of different secondary-side systems according to the different frequency current component signals; and the PI controller is used for outputting corresponding control signals to control ends of inverters so that alternating voltages output by the inverters are superpositions of different angular frequency alternating voltage components; and each angular frequency alternating voltage component corresponds to constant current output by rectifiers of each secondary-side system. The application does not need to add detection and communication modules on the secondary side, thereby realizing lightweight design of the unmanned aerial vehicle side.

Description

Technical Field

[0001] This invention relates to a charging system control system and control method, and particularly to a multi-channel constant current output hovering charging system and method for unmanned aerial vehicles. Background Technology

[0002] Currently, drones are widely used in various industries due to their flexibility, convenience, economy, and unmanned operation, including power line inspection, package delivery, natural gas pipeline inspection, military, construction, and agriculture. However, limited by battery capacity, the maximum flight range of drones is often only 3 to 33 km, which is far from sufficient for some long-distance applications. Increasing battery capacity increases the drone's power consumption and does not significantly improve its range. Therefore, it is necessary to establish charging facilities to allow drones to replenish energy mid-operation. Existing wireless charging stations for drones are relatively expensive and can achieve functions such as automatic return, fast charging, and edge computing, performing well in energy replenishment within a 7 km operating radius of the station. However, the cost of these stations is very high, making them unsuitable for large-scale deployment, and each station can only charge one drone, leading to even higher costs when there are many drones.

[0003] Multi-drone hovering charging based on WPT technology offers a good solution to the aforementioned problems. The advantages of multi-drone hovering charging are threefold: First, the cost of building a charging base station solely for wireless energy replenishment is lower than that of a drone nest with storage, charging, and data analysis functions; second, hovering charging can directly utilize the drone's flight control system to resist external interference such as strong winds, avoiding the need for additional auxiliary ground equipment such as robotic arms; third, the small size of drones and the development of drone collision avoidance technology make a charging mode where multiple drones hover and charge simultaneously at a single charging base station feasible. This mode significantly improves the utilization rate of each charging base station, thereby reducing the number of base stations and further lowering costs. However, this novel energy replenishment method also brings new challenges. The drone's flight control system cannot guarantee that the drones will remain completely stationary in the air; multiple drones inevitably experience irregular vibrations, which can cause continuous disturbances in the mutual inductance between the transmitting coil and multiple receiving coils. This leads to unstable current flowing through the receiving coil of the multi-channel WPT system, affecting battery charging performance.

[0004] To ensure constant current output characteristics under continuous mutual inductance disturbances, a constant current output control method based on mutual inductance estimation is required. However, existing constant current output control methods for UAV hovering charging systems only address single-UAV hovering charging systems, and there are no multi-constant current output control methods for multi-UAV hovering charging systems. Existing research on multi-channel WPT systems mainly focuses on system design, particularly the design of the primary-side structure and circuits, and lacks research on overcoming continuous disturbances from multiple mutual inductances. The main problem in achieving multi-mutual inductance estimation for multi-UAV hovering charging systems based on existing multi-channel WPT system research is that the traditional method of detecting current on the secondary side and transmitting it back to the primary side via a communication module for control increases the load on the UAV side, leading to increased power loss during UAV flight. Therefore, for multi-UAV hovering charging systems, a multi-constant current output control strategy is needed that does not require additional current detection and communication modules on the secondary side. Summary of the Invention

[0005] This invention provides a multi-channel constant current output hovering charging system and method for drones to solve the technical problems existing in the prior art.

[0006] The technical solution adopted by this invention to solve the technical problems existing in the prior art is: a multi-channel constant current output drone hovering charging system, which includes a primary-side system for transmitting electromagnetic energy, n secondary-side systems for receiving electromagnetic energy, and a charging control system; the primary-side system includes a DC voltage source, an inverter, a primary-side resonant compensation network, and a transmitting coil; the DC voltage source is connected to the DC input side of the inverter; the primary-side resonant compensation network includes a primary-side main capacitor, the first to the (n-1)th primary-side compensation capacitors, and the first to the (n-1)th primary-side compensation capacitors... One primary-side compensation inductor; the first to (n-1)th primary-side compensation capacitors are connected in parallel with the first to (n-1)th primary-side compensation inductors, then in series, and finally in series with the primary-side main capacitor and the transmitting coil, and then connected in parallel to the AC output side of the inverter; each secondary-side system includes a receiving coil, a secondary-side resonant compensation network, a rectifier, a filter capacitor, and a charging load; the transmitting coil and each receiving coil are electromagnetically coupled to each other; the secondary-side resonant compensation network includes the secondary-side main capacitor, the first to (n-1)th secondary-side compensation capacitors, and the first to (n-1)th secondary-side compensation capacitors... The system consists of a primary-side compensation inductor, a secondary-side compensation capacitor (numbered 1 to n-1), a secondary-side compensation capacitor (numbered 1 to n-1), a primary-side compensation capacitor (numbered 1 to n-1), a secondary-side compensation capacitor (numbered 1 to n-1), a secondary-side main capacitor, a receiving coil, and a secondary-side main capacitor (numbered 1 to n-1), and a secondary-side main capacitor (numbered 1 to n-1), which are then connected in series with the AC input side of the rectifier. The DC side of the rectifier is connected in parallel with the filter capacitor and the charging load. The charging control system includes a sampling module, a Fourier transform module, a mutual inductance estimation module, and a PI controller. The sampling module samples the current signal flowing through the transmitting coil. The Fourier transform module performs a Fourier transform on the sampled primary-side current signal to obtain current component signals of different frequencies. The mutual inductance estimation module estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary-side systems based on the different frequency current component signals. The PI controller outputs corresponding control signals to the inverter's control terminal based on different mutual inductance values, ensuring that the AC voltage output by the inverter is a superposition of AC voltage components of different angular frequencies. Each angular frequency corresponds one-to-one with the system angular frequency of the secondary-side system, and the AC voltage components of each angular frequency ensure that the current output by the rectifier of each secondary-side system remains constant.

[0007] Furthermore, the sampling module samples the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the primary system.

[0008] Furthermore, the inverter is a full-bridge inverter composed of four MOSFETs.

[0009] The present invention also provides a method for hovering charging of a drone using the above-mentioned multi-channel constant current output drone hovering charging system, the method comprising the following steps:

[0010] Step 1, let the m-th system angular frequency be... Given m = 1, 2…n, determine the component parameters of the primary and secondary resonant compensation networks so that the corresponding angular frequencies are… At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; making the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than angular frequency; i=m;

[0011] Step 2: The sampling module samples the current signal flowing through the transmitting coil, and the Fourier transform module performs a Fourier transform on the sampled primary current signal to obtain current components of different frequencies.

[0012] Step 3: The mutual inductance estimation module estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary systems based on the current components at different frequencies, and obtains the estimated value of the mutual inductance between the transmitting coil and the receiving coils of different secondary systems.

[0013] Step 4: The PI controller estimates the inductance between the transmitting coil and the receiving coils of different secondary systems, performs proportional-integral regulation on each of them, and outputs an independent control signal to the inverter control terminal. This makes the AC voltage output by the inverter a superposition of AC voltage components with different angular frequencies. Each angular frequency corresponds to the system angular frequency of the secondary system, and the amplitude of each angular frequency AC voltage component corresponds to keep the current output by the rectifier of each secondary system constant.

[0014] Furthermore, step 1 includes the following sub-steps:

[0015] Step 1-1: Draw the equivalent circuit of the primary system and the equivalent circuit of each secondary system according to the superposition theorem;

[0016] Steps 1-2: Calculate the angular frequency of the system corresponding to the primary-side resonant compensation network. The impedance, and the corresponding system angular frequency of the secondary-side resonant compensation network of the i-th secondary-side system. impedance;

[0017] Steps 1-3: According to Kirchhoff's voltage law, obtain the total impedance of the inverter output and the total impedance of the i-th secondary system.

[0018] Steps 1-4: Determine the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system, so that the corresponding system angular frequency is... At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; making the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than the angular frequency.

[0019] Furthermore, in steps 1-4, the methods for determining the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system include the following methods:

[0020] The component parameters of the primary-side resonant compensation network correspond to the system angular frequency as follows: When satisfied:

[0021] ;

[0022] For the primary-side resonant compensation network at angular frequency of Reactance at the point;

[0023] The inductance of the transmitting coil;

[0024] Make the i-th secondary side system at angular frequency of The reactance is 0 at ω, and at angular frequency ω When the reactance is infinite for all other values, the component parameters of the secondary-side resonance compensation network of the i-th secondary-side system satisfy:

[0025] ;

[0026] For the secondary-side resonant compensation network of the i-th secondary-side system at angular frequency Reactance at the point;

[0027] Let be the inductance of the receiving coil of the i-th secondary system;

[0028] Let k be the compensation capacitor in the secondary-side resonance compensation network of the i-th secondary-side system;

[0029] Let be the k-th compensation inductor in the secondary-side resonant compensation network of the i-th secondary-side system.

[0030] Furthermore, in step 3, the method for estimating the mutual inductance between the transmitting coil and the receiving coils of different secondary systems is as follows: Let the estimated value of the mutual inductance between the transmitting coil and the receiving coil of the i-th secondary system be M. esi M esi The calculation formula is as follows:

[0031] ;

[0032] In the formula, U m The angular frequency corresponding to the inverter output voltage The voltage component, Z pm The measured angular frequency of the primary system The impedance, Z sim For the measured i-th secondary system at the corresponding angular frequency The impedance, αi These are the parameters used to compensate for the deviation caused by circuit non-resonance in the i-th secondary system; The current flowing through the primary coil at an angular frequency of The amplitude at that point.

[0033] Furthermore, step 4 includes the following method steps:

[0034] Let I Li Let I be the current flowing through the load resistor in the i-th secondary system; Li_set Let I be the set value of the current flowing through the load resistor in the i-th secondary system. Li_es Let I be the estimated value of the current flowing through the load resistor in the i-th secondary system. Li_es The calculation formula is as follows:

[0035] ;

[0036] Will I Li_set and I Li_es The deviation is input to the PI controller, and the PI controller outputs the input voltage U required to eliminate the deviation. m U m The input is fed into the PWM wave generator, which acts as the actuator. The PWM wave generator uses the SSPWM method to input the required drive signal to the power switching transistors of the inverter. At this time, the inverter output voltage u in satisfy:

[0037] ;

[0038] In the formula, t represents time; adjust U m This causes the current I flowing through the receiving coil to... Li Approaching the set value I Li_set .

[0039] The advantages and positive effects of this invention are:

[0040] The present invention discloses a hovering charging method for UAVs with multi-channel constant current output. It adopts a multi-channel WPT system structure based on a multi-frequency resonating compensation (MFRC) network. By detecting the current flowing through the transmitting coil of the system, multiple mutual inductances are estimated in real time, and then multiple secondary circuits are controlled to output constant current based on the estimated mutual inductances.

[0041] This invention estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary systems in real time, and outputs control signals to drive the inverter to achieve constant current output of different secondary systems. This enables the multi-channel constant current output drone hovering charging system to maintain multiple constant current outputs under continuous disturbances of multiple mutual inductances when multiple drones are hovering for charging, thus ensuring the stability and reliability of the charging process.

[0042] The primary and secondary side system of this invention employs a resonant compensation network composed of multiple resonant compensator components, which ensures the multi-frequency resonant characteristics of the primary side circuit and the bandpass characteristics of the secondary side circuit, and on this basis, realizes communication-free multi-constant current output control.

[0043] This invention eliminates the need for additional modules such as detection and communication on the secondary side, achieving a lightweight design for the UAV side. Attached Figure Description

[0044] Figure 1 This is a circuit diagram of a multi-channel constant current output drone hovering charging system according to the present invention.

[0045] Figure 2 This is an equivalent circuit diagram of a multi-channel constant current output drone hovering charging system according to the present invention.

[0046] Figure 3 This is a schematic diagram illustrating the working principle of a multi-channel constant current output drone hovering charging system according to the present invention.

[0047] Figure 4 This is a flowchart of a hovering charging method for a drone with multi-channel constant current output according to the present invention.

[0048] In the picture: U dc The voltage of the DC power supply, u in i is the inverter output voltage. p C is the current flowing through the transmitting coil. p C is the primary-side main capacitance of the primary-side resonant compensation network. p1 ...C pn-1 Corresponding to the 1st to the (n-1st)th primary-side compensation capacitor, L p1 ...L pn-1 Corresponding to the 1st to the (n-1st)th primary-side compensating inductors, L p R is the inductance of the transmitting coil. p i represents the parasitic resistance of the primary-side resonant compensation network and the transmitting coil. p L is the current flowing through the transmitting coil. si (i=1,2…n) represents the inductance of the receiving coil of the i-th secondary system, R si (i=1,2…n) represents the parasitic resistance of the receiving coil and secondary resonant compensation network of the i-th secondary system, M iM is the inductance between the transmitting coil and the receiving coil of the i-th secondary system. iw (w=1,2…n, and w≠i) is the mutual inductance between the receiving coil of the i-th secondary system and the receiving coil of the w-th secondary system, C si Let C be the secondary-side main capacitance of the secondary-side resonant compensation network of the i-th secondary-side system. si1 ...C sin-1 L corresponds to the 1st to the (n-1st)th secondary-side compensation capacitors of the secondary-side resonant compensation network of the i-th secondary-side system. si1 ...L sin-1 C corresponds to the 1st to the (n-1st)th secondary-side compensation inductors of the secondary-side resonant compensation network of the i-th secondary-side system. di R is the capacitance value of the filter capacitor in the i-th secondary system. Li Let i be the resistance of the equivalent load of the i-th secondary system. si Let I be the current flowing through the receiving coil of the i-th secondary system. Li This corresponds to the current flowing through the load resistor of the i-th secondary system.

[0049] U in I p and I si Corresponding to u in i p and i si The phasor form of X p X is the impedance of the primary-side resonant compensation network. si Let be the impedance of the secondary-side resonant compensation network of the i-th secondary-side system.

[0050] ... The corresponding primary-side resonant compensation network at an angular frequency of Up to angular frequency Reactance at the point ... The corresponding primary system at angular frequency is Up to angular frequency The current at that point.

[0051] ... The secondary resonant compensation network corresponding to the 1st to nth secondary-side systems at an angular frequency of Reactance at the point.

[0052] ... The corresponding secondary side system at angular frequencies is 1 to n. The current at that point.

[0053] ... The corresponding secondary side system at angular frequencies is 1 to n. The current at that point.

[0054] ... The corresponding primary system at angular frequency is Up to angular frequency The input voltage at that point.

[0055] ... The secondary resonant compensation network corresponding to the 1st to nth secondary systems at angular frequency is Reactance at the point.

[0056] ... The corresponding secondary side system at angular frequencies is 1 to n. The current at that point.

[0057] R eq1 ...R eqn This corresponds to the equivalent resistance of the full-bridge rectifier, filter capacitor, and equivalent load of the first to nth secondary-side systems.

[0058] This refers to the sampling frequency of the sampling module; This is the nth operating frequency of the system. The frequency value is the highest.

[0059] I L1_set ...I Ln_set This corresponds to the load current setting values ​​for the 1st to nth secondary systems.

[0060] U1……U n The corresponding control voltage output by the PI controller corresponds to an angular frequency of Up to angular frequency The amplitude at that point.

[0061] I P1 ...I P n This corresponds to the current flowing through the primary coil at an angular frequency of Up to angular frequency The amplitude at that point.

[0062] S1 to S4 correspond to the first to fourth switching transistors that constitute the inverter; D i1 ~D i4 These correspond to the first to fourth power diodes that constitute the rectifier in the i-th secondary system. Detailed Implementation

[0063] To further understand the invention's content, features, and effects, the following embodiments are provided, along with detailed descriptions in conjunction with the accompanying drawings:

[0064] The Chinese definitions of the English words and abbreviations are as follows:

[0065] WPT: Wireless Power Transfer.

[0066] PI controller: Proportional-integral controller.

[0067] Please see Figures 1 to 4 The system includes a primary-side system for transmitting electromagnetic energy, n secondary-side systems for receiving electromagnetic energy, and a charging control system. The primary-side system includes a DC voltage source, an inverter, a primary-side resonant compensation network, and a transmitting coil. The DC voltage source is connected to the DC input side of the inverter. The primary-side resonant compensation network includes a primary-side main capacitor, n-1 primary-side compensation capacitors, and n-1 primary-side compensation inductors. The n-1 primary-side compensation capacitors are connected in parallel with the n-1 primary-side compensation inductors, then in series, and finally connected in series with the primary-side main capacitor and the transmitting coil, and then in parallel to the AC output side of the inverter. Each secondary-side system includes a receiving coil, a secondary-side resonant compensation network, a rectifier, a filter capacitor, and a charging load. The transmitting coil and each receiving coil are electromagnetically coupled to each other. The secondary-side resonant compensation network includes a secondary-side main capacitor, n-1 secondary-side compensation capacitors, and n-1 secondary-side compensation inductors. The n-1 secondary-side compensation capacitors are connected in parallel with the primary-side main capacitor and the primary-side main capacitor, then in series with the primary-side main capacitor and the transmitting coil, and finally in parallel with the AC output side of the inverter. The first to the (n-1)th secondary-side compensation inductors are connected in parallel and then in series, and then in series with the secondary-side main capacitor and the receiving coil before being connected in parallel to the AC input side of the rectifier. The DC side of the rectifier is connected in parallel with the filter capacitor and the charging load, respectively. The charging control system includes a sampling module, a Fourier transform module, a mutual inductance estimation module, and a PI controller. The sampling module is used to sample the current signal flowing through the transmitting coil. The Fourier transform module is used to perform a Fourier transform on the sampled primary-side current signal to obtain current component signals of different frequencies. The mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coils of different secondary-side systems based on the current component signals of different frequencies. The PI controller is used to output corresponding control signals to the control terminal of the inverter according to different mutual inductance values, so that the AC voltage output by the inverter is the superposition of AC voltage components of different angular frequencies. Each angular frequency corresponds one-to-one with the system angular frequency of the secondary-side system, and the AC voltage components of each angular frequency correspond to keep the current output by the rectifier of each secondary-side system constant.

[0068] The sampling module may include a current sensor, which can acquire the current signal flowing through the transmitting coil. Alternatively, the sampling module may employ other current detection devices to acquire the current signal flowing through the transmitting coil.

[0069] The setpoint current of the receiving coil in each secondary system can be used as the reference signal for the inverter's closed-loop control system. A PI controller converts the mutual inductance into a feedback signal for the control system. Through closed-loop control, the inverter's output voltage is decomposed into AC voltage components of different angular frequencies. After electromagnetic coupling through the secondary coils, the resulting current closely approximates the setpoint current of the receiving coil, thus ensuring a constant rectifier output current for each secondary system.

[0070] Preferably, the sampling module can sample the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the primary system.

[0071] Preferably, the inverter can be a full-bridge inverter composed of four MOSFETs. The inverter can also be a full-bridge inverter composed of four other power switches.

[0072] The present invention also provides a method for hovering charging of a drone using the above-mentioned multi-channel constant current output drone hovering charging system, the method comprising the following steps:

[0073] Step 1, let the m-th system angular frequency be... Given m = 1, 2…n, determine the component parameters of the primary and secondary resonant compensation networks so that the corresponding angular frequencies are… At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; making the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than angular frequency; i=m;

[0074] Step 2: The sampling module samples the current signal flowing through the transmitting coil, and the Fourier transform module performs a Fourier transform on the sampled primary current signal to obtain current components of different frequencies.

[0075] Step 3: The mutual inductance estimation module estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary systems based on the current components at different frequencies, and obtains the estimated value of the mutual inductance between the transmitting coil and the receiving coils of different secondary systems.

[0076] Step 4: The PI controller estimates the inductance between the transmitting coil and the receiving coils of different secondary systems, performs proportional-integral regulation on each of them, and outputs an independent control signal to the inverter control terminal. This makes the AC voltage output by the inverter a superposition of AC voltage components with different angular frequencies. Each angular frequency corresponds to the system angular frequency of the secondary system, and the amplitude of each angular frequency AC voltage component corresponds to keep the current output by the rectifier of each secondary system constant.

[0077] Furthermore, step 1 may include the following sub-steps:

[0078] Step 1-1: The equivalent circuit of the primary system and the equivalent circuit of each secondary system can be drawn according to the superposition theorem.

[0079] Steps 1-2 can be used to calculate the angular frequency of the system corresponding to the primary-side resonant compensation network. The impedance, and the corresponding system angular frequency of the secondary-side resonant compensation network of the i-th secondary-side system. impedance;

[0080] Steps 1-3 can be used to obtain the total impedance of the inverter output and the total impedance of the i-th secondary system according to Kirchhoff's voltage law.

[0081] Steps 1-4 determine the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system, so that the corresponding system angular frequency is... At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; this makes the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than the angular frequency.

[0082] Furthermore, in steps 1-4, the method for determining the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system may include the following methods:

[0083] The component parameters of the primary-side resonant compensation network can be adjusted to correspond to the system angular frequency. When satisfied:

[0084] ;

[0085] For the primary-side resonant compensation network at angular frequency of Reactance at the point;

[0086] The inductance of the transmitting coil;

[0087] This allows the i-th secondary system to operate at an angular frequency of... The reactance is 0 at ω, and at angular frequency ω When the reactance is infinite for all other values, the component parameters of the secondary-side resonance compensation network of the i-th secondary-side system satisfy:

[0088] ;

[0089] For the secondary-side resonant compensation network of the i-th secondary-side system at angular frequency Reactance at the point;

[0090] Let be the inductance of the receiving coil of the i-th secondary system;

[0091] Let k be the compensation capacitor in the secondary-side resonance compensation network of the i-th secondary-side system;

[0092] Let be the k-th compensation inductor in the secondary-side resonant compensation network of the i-th secondary-side system.

[0093] Furthermore, in step 3, the method for estimating the mutual inductance between the transmitting coil and the receiving coils of different secondary systems can be as follows: Let the estimated value of the mutual inductance between the transmitting coil and the receiving coil of the i-th secondary system be M. esi M esi The calculation formula is as follows:

[0094] ;

[0095] In the formula, U m The angular frequency corresponding to the inverter output voltage The voltage component, Z pm The measured angular frequency of the primary system The impedance, Z sim For the measured i-th secondary system at the corresponding angular frequency The impedance, α i These are the parameters used to compensate for the deviation caused by circuit non-resonance in the i-th secondary system; The current flowing through the primary coil at an angular frequency of The amplitude at that point.

[0096] Furthermore, step 4 may include the following method steps:

[0097] Let I be an example. Li Let I be the current flowing through the load resistor in the i-th secondary system; Li_set Let I be the set value of the current flowing through the load resistor in the i-th secondary system. Li_es Let I be the estimated value of the current flowing through the load resistor in the i-th secondary system. Li_es The calculation formula is as follows:

[0098] ;

[0099] I can Li_set and I Li_es The deviation is input to the PI controller, and the PI controller outputs the input voltage U required to eliminate the deviation. m U m The input is fed into the PWM wave generator, which acts as the actuator. The PWM wave generator uses the SSPWM method to input the required drive signal to the power switching transistors of the inverter. At this time, the inverter output voltage u insatisfy:

[0100] ;

[0101] In the formula, t represents time; adjust U m This causes the current I flowing through the receiving coil to... Li Approaching the set value I Li_set .

[0102] The workflow and working principle of the present invention will be further described below with reference to a preferred embodiment:

[0103] A multi-channel constant current output hovering charging system for unmanned aerial vehicles (UAVs) includes a primary-side system for transmitting electromagnetic energy, n secondary-side systems for receiving electromagnetic energy, and a charging control system. The primary-side system includes a DC voltage source, an inverter, a primary-side resonant compensation network, and a transmitting coil. The DC voltage source is connected to the DC input side of the inverter. The primary-side resonant compensation network includes a primary-side main capacitor, n-1 primary-side compensation capacitors, and n-1 primary-side compensation inductors. Each capacitor is connected in parallel and then in series with the 1st to n-1st primary-side compensation inductors, and then in series with the primary-side main capacitor and the transmitting coil, and finally connected in parallel to the AC output side of the inverter. Each secondary-side system includes a receiving coil, a secondary-side resonant compensation network, a rectifier, a filter capacitor, and a charging load. The transmitting coil and each receiving coil are electromagnetically coupled to each other. The secondary-side resonant compensation network includes the secondary-side main capacitor, the 1st to n-1st secondary-side compensation capacitors, and the 1st to n-1st secondary-side compensation inductors. The compensation capacitors are connected in parallel and then in series with the first to (n-1)th secondary-side compensation inductors, and then in series with the secondary-side main capacitor and the receiving coil, and finally connected in parallel to the AC input side of the rectifier. The DC side of the rectifier is connected in parallel with the filter capacitor and the charging load. The charging control system includes a sampling module, a Fourier transform module, a mutual inductance estimation module, and a PI controller. The sampling module is used to sample the current signal flowing through the transmitting coil. The Fourier transform module is used to perform a Fourier transform on the sampled primary-side current signal to obtain current component signals of different frequencies. The mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coils of different secondary-side systems based on the current component signals of different frequencies. The PI controller is used to output corresponding control signals to the control terminal of the inverter according to different mutual inductance values, so that the AC voltage output by the inverter is the superposition of AC voltage components of different angular frequencies. Each angular frequency corresponds one-to-one with the system angular frequency of the secondary-side system, and the AC voltage components of each angular frequency correspond to keep the current output by the rectifier of each secondary-side system constant.

[0104] The sampling module samples the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the primary system.

[0105] A hovering charging method for a drone utilizing the aforementioned multi-channel constant current output drone hovering charging system includes the following steps:

[0106] Step A involves designing a multi-channel charging system structure based on a multi-frequency resonant compensation network, including the structure and component parameters, to ensure the independence of each channel.

[0107] Step B involves using devices such as current sensors to sample the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the circuit. A Fourier transform module is then used to obtain current components at different frequencies through the Fast Fourier Transform (FFT) method, which are used to estimate the mutual inductance between the transmitting coil and the receiving coils of different secondary systems.

[0108] Step C involves using a PI controller to control the current flowing through the receiving coil by adjusting the input voltage at different frequencies, based on the mutual inductance between the transmitting coil and the receiving coils of different secondary systems. This achieves multiple constant current outputs and ensures the stability and reliability of the multi-UAV hovering charging system.

[0109] Superposed Sinusoidal Pulse Width Modulation (SSPMW) allows the DC power supply and full-bridge inverter to generate a voltage signal with multiple superimposed frequencies. The principle is similar to conventional Sinusoidal Pulse Width Modulation (SPPWM), but the difference lies in the signal wave: conventional SPPWM uses a single-frequency sine wave, while SSPWM uses a superimposed sine wave of multiple frequencies. Using SSPWM, the output voltage can contain multiple frequency components, and the amplitude of each component is independently controllable. Therefore, the DC power supply and full-bridge inverter can be considered equivalent to an AC voltage source. The equivalent resistance of the full-bridge rectifier, filter capacitor, and equivalent load is:

[0110] (1);

[0111] The equivalent resistance of the full-bridge rectifier, filter capacitor, and equivalent load of the i-th secondary-side system.

[0112] The resistance of the equivalent load of the i-th secondary system

[0113] Therefore, the equivalent circuit diagram of the multi-channel WPT system based on the MFRC network is drawn according to the superposition theorem as follows: Figure 2 As shown. Uin I p and I si For u in i p and i si The phasor form of X p X is the impedance of the primary-side resonant compensation network. si Let be the impedance of the secondary-side resonant compensation network of the i-th secondary-side system, and its expression is as follows:

[0114] (2);

[0115] In the formula, subscript i represents the number of the secondary system; subscript k represents the k-th group of parallel LC modules of the primary-side resonant compensation network or the secondary-side resonant compensation network. The first primary-side compensation capacitor and the first primary-side compensation inductor are connected in parallel to form the first group of primary-side parallel LC modules, and the k-th primary-side compensation capacitor and the k-th primary-side compensation inductor are connected in parallel to form the k-th group of primary-side parallel LC modules. Subscript m represents the component of the variable at the m-th operating frequency, ω. m Let be the system angular frequency corresponding to the m-th operating frequency.

[0116] n is the number of secondary edge systems; This is the primary-side main capacitor; This is the secondary-side main capacitor; This is the k-th primary-side compensation capacitor; This is the k-th primary-side compensating inductor; For the i-th secondary-side system, the primary-side compensation capacitor is denoted as k. For the k-th primary-side compensating inductor of the i-th secondary-side system; For the primary-side resonant compensation network at angular frequency of Reactance at the point; For the secondary-side resonant compensation network of the i-th secondary-side system at angular frequency Reactance at the point.

[0117] According to Kirchhoff's voltage law:

[0118] (3);

[0119] In the formula:

[0120] For an angular frequency of Input voltage at the location; For an angular frequency of The primary current at the location; For an angular frequency of The total impedance of the primary side at that location; For an angular frequency of The current in the i-th secondary-side system; Let be the mutual inductance between the receiving coil of the i-th secondary system and the transmitting coil of the primary system; For an angular frequency of The total impedance of the i-th secondary-side system; Let be the mutual inductance between the receiving coil of the i-th secondary system and the receiving coil of the w-th secondary system.

[0121] In the formula, and Let be the total impedance of the primary circuit and the total impedance of the secondary circuit, respectively, and their expressions are as follows:

[0122] (4);

[0123] In the formula, The parasitic resistance of the primary-side system's transmitting coil and primary-side resonant compensation network; The inductance of the transmitting coil; Let be the inductance of the i-th receiving coil; For the secondary-side resonant compensation network of the i-th secondary-side system at angular frequency Reactance at the point. For the primary-side resonant compensation network at angular frequency of Reactance at the point. The equivalent resistance of the full-bridge rectifier, filter capacitor, and equivalent load; Let be the parasitic resistance of the receiving coil and the secondary resonant compensation network of the i-th secondary system.

[0124] The parameter design in step 1 includes the parameter design of the primary-side resonant compensation network and the secondary-side resonant compensation network. To ensure the dual-resonant frequency characteristics of the primary-side circuit, the parameter design of the primary-side resonant compensation network should meet the following requirements:

[0125] (5);

[0126] For the primary-side resonant compensation network at angular frequency of Reactance at the point;

[0127] To ensure that the reactance of the secondary circuit is 0 at the corresponding frequency and infinite at non-corresponding frequencies, the parameters of the secondary resonant compensation network should be designed to satisfy the following:

[0128] (6);

[0129] In the formula, i is the sequence number of the secondary side system; The index is the angular frequency.

[0130] After parameter design, the current I flowing through the transmitting coil p and the current I flowing through the receiving coil sisatisfy

[0131] (7);

[0132] That is, each current flowing through the receiving coil is only related to a variable of one operating frequency, and there is a one-to-one correspondence. The component of the current flowing through the transmitting coil at a certain operating frequency is only related to the variable of the secondary circuit corresponding to that frequency. The primary circuit can adjust the current flowing through the corresponding receiving coil by adjusting the input voltage at that frequency, and will not affect the current flowing through the non-corresponding receiving coil, thus realizing multi-channel simultaneous independent transmission.

[0133] In step 2, sampling the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the circuit refers to the sampling frequency f of the current sensor. s The sampling frequency should be greater than or equal to twice the circuit's highest operating frequency f2 to ensure that the discrete sampling satisfies Shannon's sampling theorem. The sampled signal is input to the charging control system for further processing. The charging control system is used for data processing and analysis, and subsequent pulse width modulation (PWM) signal generation. The function of the FFT is to discretely sample the current i flowing through the transmitting coil. p The obtained current signal is decomposed to obtain its operating frequency. Current component I pm Based on this, the estimated mutual inductance M is obtained using other known quantities and the primary edge detection value. esi The expression is

[0134] (8);

[0135] In the formula, U m The angular frequency corresponding to the inverter output voltage The voltage component, Z pm The measured angular frequency of the primary system The impedance, Z sim For the measured i-th secondary system at the corresponding angular frequency The impedance, α i These are the parameters used to compensate for the deviation caused by circuit non-resonance in the i-th secondary system; The current flowing through the primary coil at an angular frequency of The amplitude at that point.

[0136] All of the above parameters are known quantities. M esi The estimation avoids complex phasor calculations, reducing the computational load on the charging control system. Due to the multi-channel transmission advantages of the WPT system based on the MFRC network, M... esi The calculations are independent of each other, enabling real-time estimation of multiple mutual inductances.

[0137] In step 3, the PI control block diagram based on multi-mutual-inductance estimation is as follows: Figure 3 As shown. Figure 3 middle, I Li_set I is the set value of the current flowing through the receiving coil. Li The estimated value I Li_es The expression is

[0138] (9);

[0139] I Li_set and I Li_es The deviation is input to the PI controller, and the PI controller outputs the input voltage U required to eliminate the deviation. m U m The input signal is fed into the PWM wave generator, which acts as the actuator. The PWM wave generator uses the SSPWM method to input the required drive signal into the four MOSFETs of the full-bridge inverter. At this time, the DC power supply and the input voltage u generated by the full-bridge inverter... in satisfy

[0140] (10);

[0141] In the formula, t represents time. As U... m The adjustment of the current I flowing through the receiving coil Li The approximation setpoint I will be adjusted accordingly. Li_set It achieves multiple constant current outputs.

[0142] DC voltage source, inverter, primary side resonant compensation network, transmitting coil, receiving coil, secondary side resonant compensation network, rectifier, filter capacitor, charging load, primary side main capacitor, primary side compensation capacitor, primary side compensation inductor, secondary side main capacitor, secondary side compensation capacitor, secondary side compensation inductor, sampling module, Fourier transform module, mutual inductance estimation module, PI controller, PWM wave generator, full-bridge inverter, current sensor, etc. can all use existing components and functional modules, or be constructed using existing components and functional modules and conventional technical means.

[0143] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The patent scope of the present invention should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. A multi-channel constant current output hovering charging system for unmanned aerial vehicles (UAVs), characterized in that, The system includes a primary-side system for transmitting electromagnetic energy, n secondary-side systems for receiving electromagnetic energy, and a charging control system; the primary-side system includes a DC voltage source, an inverter, a primary-side resonant compensation network, and a transmitting coil. A DC voltage source is connected to the DC input side of the inverter; the primary-side resonant compensation network includes a primary-side main capacitor, the first to (n-1)th primary-side compensation capacitors, and the first to (n-1)th primary-side compensation inductors; the first to (n-1)th primary-side compensation capacitors are connected in parallel with the first to (n-1)th primary-side compensation inductors, then in series, and finally connected in series with the primary-side main capacitor and the transmitting coil, and then connected in parallel to the AC output side of the inverter; each secondary-side system includes a receiving coil, a secondary-side resonant compensation network, a rectifier, a filter capacitor, and a charging load; the transmitting coil and each receiving coil are electromagnetically coupled to each other; the secondary-side resonant compensation network includes a secondary-side main capacitor, the first to (n-1)th secondary-side compensation capacitors, and the first to (n-1)th secondary-side compensation inductors; the first to (n-1)th secondary-side compensation capacitors are connected in parallel with the first to (n-1)th secondary-side compensation inductors, then in series, and finally connected in series with the secondary-side main capacitor and the receiving .... The AC input side of the rectifier is connected to the DC side of the rectifier, which is connected in parallel with the filter capacitor and the charging load. The charging control system includes a sampling module, a Fourier transform module, a mutual inductance estimation module, and a PI controller. The sampling module is used to sample the current signal flowing through the transmitting coil. The Fourier transform module is used to perform a Fourier transform on the sampled primary current signal to obtain current component signals of different frequencies. The mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coils of different secondary systems based on the current component signals of different frequencies. The PI controller is used to output corresponding control signals to the control terminal of the inverter according to different mutual inductance values, so that the AC voltage output by the inverter is the superposition of AC voltage components of different angular frequencies. Each angular frequency corresponds one-to-one with the system angular frequency of the secondary system, and the AC voltage components of each angular frequency correspond to keep the current output by the rectifier of each secondary system constant. The mutual inductance estimation module estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary systems based on the current components at different frequencies, using the following method: Let the estimated value of the mutual inductance between the transmitting coil and the receiving coil of the i-th secondary system be M. esi M esi The calculation formula is as follows: ； In the formula, U m The angular frequency corresponding to the inverter output voltage The voltage component, Z pm The measured angular frequency of the primary system The impedance, Z sim For the measured i-th secondary system at the corresponding angular frequency The impedance, α i These are the parameters used to compensate for the deviation caused by circuit non-resonance in the i-th secondary system; The current flowing through the primary coil at an angular frequency of The amplitude at that point.

2. The multi-channel constant current output UAV hovering charging system according to claim 1, characterized in that, The sampling module samples the current signal flowing through the transmitting coil at a sampling frequency greater than or equal to twice the highest operating frequency of the primary system.

3. The multi-channel constant current output UAV hovering charging system according to claim 1, characterized in that, The inverter is a full-bridge inverter composed of four MOSFETs.

4. A method for hovering charging a drone using a multi-channel constant current output drone hovering charging system according to any one of claims 1 to 3, characterized in that, The method includes the following steps: Step 1, let the m-th system angular frequency be... Given m = 1, 2…n, determine the component parameters of the primary and secondary resonant compensation networks so that the corresponding angular frequencies are… At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; making the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than angular frequency; i=m; Step 2: The sampling module samples the current signal flowing through the transmitting coil, and the Fourier transform module performs a Fourier transform on the sampled primary current signal to obtain current components of different frequencies. Step 3: The mutual inductance estimation module estimates the mutual inductance between the transmitting coil and the receiving coils of different secondary systems based on the current components at different frequencies, and obtains the estimated value of the mutual inductance between the transmitting coil and the receiving coils of different secondary systems. Step 4: The PI controller estimates the inductance between the transmitting coil and the receiving coils of different secondary systems, performs proportional-integral regulation on each of them, and outputs an independent control signal to the inverter control terminal. This makes the AC voltage output by the inverter a superposition of AC voltage components with different angular frequencies. Each angular frequency corresponds to the system angular frequency of the secondary system, and the amplitude of each angular frequency AC voltage component corresponds to keep the current output by the rectifier of each secondary system constant.

5. The UAV hovering charging method with multi-channel constant current output according to claim 4, characterized in that, Step 1 includes the following sub-steps: Step 1-1: Draw the equivalent circuit of the primary system and the equivalent circuit of each secondary system according to the superposition theorem; Steps 1-2: Calculate the angular frequency of the system corresponding to the primary-side resonant compensation network. The impedance, and the corresponding system angular frequency of the secondary-side resonant compensation network of the i-th secondary-side system. impedance; Steps 1-3: According to Kirchhoff's voltage law, obtain the total impedance of the inverter output and the total impedance of the i-th secondary system. Steps 1-4: Determine the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system, so that the corresponding system angular frequency is... At this time, the absolute value of the inductance of the transmitting coil is equal to the absolute value of the impedance of the primary resonant compensation network, but with opposite signs; making the total impedance of the i-th secondary system zero, and the secondary system operates at... The total impedance is infinite at frequencies other than the angular frequency.

6. The UAV hovering charging method with multi-channel constant current output according to claim 5, characterized in that, In steps 1-4, the methods for determining the component parameters of the primary-side resonant compensation network and the secondary-side resonant compensation network of each secondary-side system include the following: The component parameters of the primary-side resonant compensation network correspond to the system angular frequency as follows: When satisfied: ； For the primary-side resonant compensation network at angular frequency of Reactance at the point; The inductance of the transmitting coil; Make the i-th secondary side system at angular frequency of The reactance is 0 at ω, and at angular frequency ω When the reactance is infinite for all other values, the component parameters of the secondary-side resonant compensation network of the i-th secondary-side system satisfy: ； For the secondary-side resonant compensation network of the i-th secondary-side system at angular frequency Reactance at the point; Let be the inductance of the receiving coil of the i-th secondary system; Let k be the compensation capacitor in the secondary-side resonance compensation network of the i-th secondary-side system; Let be the k-th compensation inductor in the secondary-side resonant compensation network of the i-th secondary-side system.

7. The UAV hovering charging method with multi-channel constant current output according to claim 4, characterized in that, Step 4 includes the following steps: Let I Li Let I be the current flowing through the load resistor in the i-th secondary system; Li_set Let I be the set value of the current flowing through the load resistor in the i-th secondary system. Li_es Let I be the estimated value of the current flowing through the load resistor in the i-th secondary system. Li_es The calculation formula is as follows: ； Will I Li_set and I Li_es The deviation is input to the PI controller, and the PI controller outputs the input voltage U required to eliminate the deviation. m U m The input is fed into the PWM wave generator, which acts as the actuator. The PWM wave generator uses the SSPWM method to input the required drive signal to the power switching transistors of the inverter. At this time, the inverter output voltage u in satisfy: ； In the formula, t represents time; adjust U m This causes the current I flowing through the receiving coil to... Li Approaching the set value I Li_set ; U1……U n The corresponding control voltage output by the PI controller corresponds to an angular frequency of Up to angular frequency The amplitude at that point.

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