A method for estimating mutual inductance of a drone hovering wireless charging system

Abstract

This invention discloses a method for estimating mutual inductance in a hovering wireless charging system for unmanned aerial vehicles (UAVs). The charging system includes: a transmitting system for transmitting electromagnetic energy, a receiving system for receiving electromagnetic energy, and a charging control system. The transmitting system includes a DC voltage source, an inverter, a transmitting-side compensation capacitor, and a transmitting coil. The receiving system includes a receiving coil, a receiving-side compensation capacitor, a rectifier, a filter capacitor, and a charging load. The charging control system includes a sampling module, an equivalent circuit vector model, and a mutual inductance estimation module. The sampling module samples the voltage and current at the inverter output. The equivalent circuit vector model represents the dynamic equations of the equivalent circuit of the charging system in complex form. The mutual inductance estimation module estimates the mutual inductance using the voltage and current collected by the sampling module and the equivalent circuit vector model. This invention can track the mutual inductance to adjust the input voltage (phase shift angle) in a timely manner, making the receiving-side current approximately constant.

Description

Technical Field

[0001] This invention relates to a control method for a hovering wireless charging system for unmanned aerial vehicles (UAVs), and more particularly to a method for estimating the mutual inductance of a hovering wireless charging system for UAVs. Background Technology

[0002] Currently, electrically powered multi-rotor drones are developing rapidly and are already being used in various industrial scenarios, such as inspection and surveying. However, due to battery capacity limitations, the flight time of these drones is often insufficient to meet the demands of large-scale, long-duration continuous operations. Existing solutions primarily involve manual battery swapping, but this requires the drone to turn back and forth for takeoff and landing, limiting its effective operating range and failing to meet continuous operation requirements. Hovering wireless charging technology for drones has emerged as an ideal solution to these problems, as it can replenish the energy of drones in a timely manner, enabling them to operate continuously.

[0003] In practical applications, hovering drones are often susceptible to environmental interference and cannot maintain a constant hovering position. This causes continuous misalignment between the transmitting coil and the receiving coil on the drone side of the wireless charging system, inevitably leading to continuous changes in mutual inductance and affecting the stability of energy transmission. Therefore, it is necessary to estimate and track mutual inductance changes in a timely manner to provide the necessary system information for achieving stable energy transmission. Existing solutions estimate mutual inductance outside the charging process by using methods such as frequency sweeping, open circuit, and short circuit for fixed coil misalignment. However, these solutions cannot estimate the changing mutual inductance in real time during the charging process, and thus cannot adjust the system input in a timely manner to achieve stable energy transmission. Therefore, for the specific needs of drone hovering wireless charging systems, a novel mutual inductance estimation method must be designed that can track mutual inductance changes in a timely manner during the charging process, providing the necessary prerequisite for achieving stable energy transmission. Summary of the Invention

[0004] This invention provides a method for estimating mutual inductance in a hovering wireless charging system for unmanned aerial vehicles (UAVs) to address the technical problems existing in the prior art.

[0005] The technical solution adopted by this invention to solve the technical problems existing in the prior art is: a method for estimating the mutual inductance of a drone hovering wireless charging system. The charging system used in this method includes: a transmitting system for transmitting electromagnetic energy, a receiving system for receiving electromagnetic energy, and a charging control system; the transmitting system includes a DC voltage source, an inverter, a transmitting-side compensation capacitor, and a transmitting coil; the DC voltage source is connected to the DC input side of the inverter; the transmitting-side compensation capacitor and the transmitting coil are connected in series and then in parallel to the AC output side of the inverter; the receiving system includes a receiving coil, a receiving-side compensation capacitor, a rectifier, a filter capacitor, and a charging load; The transmitting coil and receiving coil are electromagnetically coupled to each other; the receiving-side compensation capacitor is connected in series with the receiving coil and then 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, an equivalent circuit vector model and a mutual inductance estimation module; the sampling module is used to sample the voltage and current signals on the output side of the inverter; the equivalent circuit vector model uses complex numbers to characterize the equivalent circuit dynamic equation of the charging system; the mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coil using the voltage and current signals collected by the sampling module and the equivalent circuit vector model.

[0006] Furthermore, it includes the following steps:

[0007] Step 1: Establish the equivalent circuit vector model, determine the resistance and capacitance values ​​of the transmitting-side compensation capacitor, the self-inductance and internal resistance of the transmitting coil, the system operating angular frequency, and the receiving-side impedance Z. r ;

[0008] Step 2: Detect the current and voltage signals on the inverter output side and calculate the amplitude of the transmitter current;

[0009] Step 3: Determine the voltage amplitude on the inverter output side by the phase shift angle of the inverter phase shift control;

[0010] Step 4: Calculate the amplitude of the induced voltage in the transmitting coil using the equivalent circuit vector model and the amplitude of the transmitting current;

[0011] Step 5: Calculate the estimated value of the mutual inductance between the transmitting coil and the receiving coil based on the amplitude of the induced voltage in the transmitting coil.

[0012] Further, in step 1, the equivalent circuits of the transmitting system and the receiving system are drawn, and the following equivalent circuit vector model is established from the equivalent circuits:

[0013]

[0014] In the formula, C t L is the compensation capacitor on the transmitting side. t For the self-inductance of the transmitting coil, R t R is the internal resistance of the transmitting coil. rR is the internal resistance of the receiving coil. L For the equivalent load of the receiving system, L r For the self-inductance of the receiving coil, C r M is the receiving-side compensation capacitor, M is the mutual inductance between the transmitting and receiving coils, and I is the receiving-side compensation capacitor. dqt Let I be the emitter-side current vector. dqr U is the receiver-side current vector, ω0 is the system operating angular frequency, and U s This represents the input voltage amplitude.

[0015] Furthermore, in step 1, the system operating angular frequency is a set value, and the receiving-side impedance Z... r The calculation formula is as follows:

[0016]

[0017] Furthermore, in step 2, the method for detecting the current and voltage signals on the inverter output side and calculating the amplitude of the transmitter current is as follows: when the instantaneous value of the output voltage on the inverter output side is 0 and the derivative of the output voltage is greater than 0, the instantaneous value of the transmitter current at this time is sampled and recorded as I. qt When the output voltage on the inverter output side reaches its positive peak value, the instantaneous value of the transmitter current at this moment is sampled and recorded as I. dt ;Suppose I t Let I be the amplitude of the transmitting current. t The calculation formula is as follows:

[0018]

[0019] Furthermore, in step 3, the method for calculating the voltage amplitude on the inverter output side based on the phase shift angle controlled by the inverter phase shift is as follows:

[0020]

[0021] In the formula, U dc α is the DC power supply voltage, and α is the phase shift angle of the inverter's phase shift control.

[0022] Furthermore, in step 4, the method for calculating the amplitude of the induced voltage of the transmitting coil is as follows: Let I r I represents the amplitude of the receiving current. dr For the receiving side current I in orthogonal system dqr The real part, I qr For the receiving side current I in orthogonal system dqr The imaginary part of is obtained from the equivalent circuit vector model, as follows:

[0023]

[0024] Substitute the values ​​of the following known parameters: C t Lt R t I qt I qt , ω0, U s The following induced voltage U of the transmitting coil is further obtained. Mt The calculation formula is as follows:

[0025]

[0026] Furthermore, in step 5, the formula for calculating the estimated value of the mutual inductance between the transmitting coil and the receiving coil is as follows:

[0027]

[0028] The advantages and positive effects of this invention are as follows: This invention enables real-time mutual inductance estimation during the charging process. Compared to existing methods such as frequency sweeping, open-circuit, and short-circuit methods, which can only estimate mutual inductance during non-charging processes due to fixed coil misalignment, this invention can be well applied to drone hovering wireless charging systems, providing necessary control parameters for maintaining a constant charging effect (e.g., constant current). Furthermore, this invention only performs mutual inductance estimation on the energy transmitting side, eliminating the need for additional wireless communication equipment, reducing system cost and complexity, and meeting the lightweight design requirements of drones. The mutual inductance values ​​and other data obtained by this invention can be applied to the closed-loop control of inverters. By rapidly tracking the mutual inductance, the input voltage (phase shift angle) can be adjusted in a timely manner to ensure approximately constant current on the receiving side. Attached Figure Description

[0029] Figure 1 This is a circuit diagram of a drone hovering wireless charging system used in this invention;

[0030] Figure 2 This is an equivalent circuit diagram of a drone hovering wireless charging system used in this invention;

[0031] Figure 3 This is an equivalent circuit vector model of a drone hovering wireless charging system used in this invention;

[0032] Figure 4 This is a schematic diagram of the structure of a drone hovering wireless charging system used in this invention;

[0033] Figure 5 This is a flowchart illustrating the mutual inductance estimation method for the drone hovering wireless charging system of the present invention.

[0034] In the diagram: C t L is the compensation capacitor on the transmitting side. t For the self-inductance of the transmitting coil, R t R is the internal resistance of the transmitting coil. rR is the internal resistance of the receiving coil. L For the equivalent load of the receiving system, L r For the self-inductance of the receiving coil, C r The receiving side compensation capacitor is M, where M is the mutual inductance between the transmitting and receiving coils, and R is R. l For the charging load resistor, C l For the filter capacitor, I dqt Let I be the emitter-side current vector. dqr U is the receiver-side current vector, ω0 is the system operating angular frequency, and U s U is the input voltage amplitude. dc I is the DC power supply voltage. r I represents the amplitude of the receiving current. t The amplitude of the transmitter current is represented by S1 to S4, which correspond to the first to fourth switching transistors constituting the inverter; D1 to D4 correspond to the first to fourth power diodes constituting the rectifier. This indicates the phase angle by which the emitter current lags behind the input voltage. This indicates the phase angle by which the receiving current lags behind the input voltage. Detailed Implementation

[0035] 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:

[0036] Please see Figures 1 to 5 A method for estimating mutual inductance in a hovering wireless charging system for unmanned aerial vehicles (UAVs) is disclosed. The charging system comprises: a transmitting system for transmitting electromagnetic energy, a receiving system for receiving electromagnetic energy, and a charging control system. The transmitting system includes a DC voltage source, an inverter, a transmitting-side compensation capacitor, and a transmitting coil. The DC voltage source is connected to the DC input side of the inverter. The transmitting-side compensation capacitor and the transmitting coil are connected in series and then in parallel to the AC output side of the inverter. The receiving system includes a receiving coil, a receiving-side compensation capacitor, a rectifier, a filter capacitor, and a charging load. The transmitting coil and the receiving coil are electromagnetically coupled to each other. The receiving-side compensation capacitor and the receiving coil are connected in series and then 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, an equivalent circuit vector model, and a mutual inductance estimation module. The sampling module samples the voltage and current signals from the inverter output side. The equivalent circuit vector model uses complex numbers to characterize the dynamic equations of the equivalent circuit of the charging system. The mutual inductance estimation module uses the voltage and current signals collected by the sampling module and the equivalent circuit vector model to estimate the mutual inductance between the transmitting coil and the receiving coil.

[0037] The equivalent circuit vector model uses complex numbers to characterize the dynamic equations of the equivalent circuit of the charging system, which simplifies the dynamic equations of the equivalent circuit of the charging system.

[0038] The charging control system may also include a digital signal processor (DSP). The DSP takes in the mutual inductance feedback signal from the mutual inductance estimation module and outputs a drive signal to drive the power switching transistors of the inverter, thus putting the inverter into operation. The sampling module may include a high-bandwidth current sensor, etc.

[0039] Preferably, the method may include the following steps:

[0040] Step 1: Establish the equivalent circuit vector model, determine the resistance and capacitance values ​​of the transmitting-side compensation capacitor, the self-inductance and internal resistance of the transmitting coil, the system operating angular frequency, and the receiving-side impedance Z. r .

[0041] Step 2: Detect the current and voltage signals on the inverter output side and calculate the amplitude of the transmitter current.

[0042] Step 3: Determine the voltage amplitude on the inverter output side by the phase shift angle controlled by the inverter phase shift control.

[0043] Step 4: Calculate the amplitude of the induced voltage in the transmitting coil using the equivalent circuit vector model and the amplitude of the transmitting current.

[0044] Step 5: Calculate the estimated value of the mutual inductance between the transmitting coil and the receiving coil based on the amplitude of the induced voltage in the transmitting coil.

[0045] Preferably, in step 1, the equivalent circuits of the transmitting system and the receiving system can be drawn, and the following equivalent circuit vector model can be established from the equivalent circuit:

[0046]

[0047] In the formula, C t L is the compensation capacitor on the transmitting side. t For the self-inductance of the transmitting coil, R t R is the internal resistance of the transmitting coil. r R is the internal resistance of the receiving coil. L For the equivalent load of the receiving system, L r For the self-inductance of the receiving coil, C r The receiving side compensation capacitor is M, where M is the mutual inductance between the transmitting and receiving coils, and R is R. l For charging load, C l For the filter capacitor, I dqt Let I be the emitter-side current vector. dqr U is the receiver-side current vector, ω0 is the system operating angular frequency, and U s This represents the input voltage amplitude.

[0048] Preferably, in step 1, C t L t R t R r RL L r C r These are the parameter values ​​of the components themselves; the system operating angular frequency can be a set value; and the receiving-side impedance Z... r The calculation formula is as follows:

[0049]

[0050] Preferably, in step 2, the method for detecting the current and voltage signals on the inverter output side and calculating the amplitude of the transmitter current is as follows: when the instantaneous value of the output voltage on the inverter output side is 0 and the derivative of the output voltage is greater than 0, the instantaneous value of the transmitter current at this time is sampled and recorded as I. qt When the output voltage on the inverter output side reaches its positive peak value, the instantaneous value of the transmitter current at this moment is sampled and recorded as I. dt ;Suppose I t Let I be the amplitude of the transmitting current. t The calculation formula is as follows:

[0051]

[0052] Current and voltage signals can be obtained through high-frequency sampling, and synchronized current and voltage waveforms can be obtained based on the amplitude and timing of the sampled signals. I0 can then be derived from these synchronized current and voltage waveforms. qt and I dt The value of I can also be obtained through other functional modules or software. qt and I dt

[0053] Preferably, in step 3, the method for calculating the voltage amplitude on the inverter output side based on the phase shift angle controlled by the inverter phase shift can be as follows:

[0054]

[0055] In the formula, U dc α is the DC power supply voltage, and α is the phase shift angle of the inverter's phase shift control.

[0056] Preferably, in step 4, the method for calculating the amplitude of the induced voltage of the transmitting coil can be as follows: Let I r I represents the amplitude of the receiving current. dr For the receiving side current I in orthogonal system dqr The real part, I qr For the receiving side current I in orthogonal system dqr The imaginary part of can be derived from the equivalent circuit vector model as follows:

[0057]

[0058] Substitute the values ​​of the following known parameters: C t Lt R t I qt I qt , ω0, U s The following induced voltage U of the transmitting coil can be further obtained. Mt The calculation formula is as follows:

[0059]

[0060] Preferably, in step 5, the formula for calculating the estimated value of the mutual inductance between the transmitting coil and the receiving coil can be as follows:

[0061]

[0062] The working principle of the present invention will be further explained below with reference to a preferred embodiment:

[0063] This invention discloses a mutual inductance estimation method for a hovering wireless charging system for unmanned aerial vehicles (UAVs). By measuring the instantaneous current value on the energy-emitting side using a current sensor, the mutual inductance is estimated in real time based on the current information and known system parameters. This effectively tracks changes in mutual inductance, providing a necessary foundation for achieving stable energy transmission. Furthermore, this method only collects current information on the energy-emitting side, eliminating the need for wireless communication and avoiding the addition of extra equipment on the UAV side, thus meeting the lightweight design requirements of UAVs.

[0064] Please see Figure 1 The charging system employed in this method includes: a transmitting system for emitting electromagnetic energy, a receiving system for receiving electromagnetic energy, and a charging control system; the transmitting system includes a DC voltage source, an inverter, a transmitting-side compensation capacitor, and a transmitting coil; the DC voltage source is connected to the DC input side of the inverter; the transmitting-side compensation capacitor and the transmitting coil are connected in series and then in parallel to the AC output side of the inverter; the receiving system includes a receiving coil, a receiving-side compensation capacitor, a rectifier, a filter capacitor, and a charging load; the transmitting coil and the receiving coil are electromagnetically coupled to each other; the receiving-side compensation capacitor and the receiving coil are connected in series and then 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, an equivalent circuit vector model, and a mutual inductance estimation module; the sampling module is used to sample the voltage and current signals on the output side of the inverter; the equivalent circuit vector model uses complex numbers to characterize the equivalent circuit dynamic equations of the charging system; the mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coil using the voltage and current signals collected by the sampling module and the equivalent circuit vector model.

[0065] Figure 2 To obtain the equivalent circuit diagram of the drone hovering wireless charging system used in this invention based on fundamental wave analysis; where U s I represents the amplitude of the system input voltage, which is also the amplitude of the inverter output voltage.t I is the amplitude of the transmitting side current. r Let ω0 be the amplitude of the receiving current, and let ω0 be the system operating angular frequency. The relationship between ω0 and the system operating frequency f is shown in formula (3). The phase difference between the transmitter current and the input voltage. This represents the phase difference between the receiving current and the input voltage.

[0066] Figure 3 This is an equivalent circuit vector model of a drone hovering wireless charging system used in this invention; where I dqt For the emitter current in an orthogonal system, I dqr The current on the receiving side in the orthogonal system is given by the expression of the equivalent circuit vector model as shown in formula (1).

[0067] Figure 4 This is a schematic diagram of a hovering wireless charging system for unmanned aerial vehicles (UAVs) used in this invention. A digital signal processor (DSP) outputs a drive signal to put the inverter into operation. A high-bandwidth current sensor detects the instantaneous value of the transmitter current at a specific moment and feeds the current information back to the DSP. The DSP performs real-time mutual inductance estimation based on stored system parameters, the phase shift angle information of the input voltage drive signal, and the detected instantaneous value of the transmitter current.

[0068] Figure 1 The hovering wireless charging system for drones shown employs the method of this invention to estimate and track the mutual inductance M. Specific steps are as follows: Figure 5 As shown:

[0069] Step A: Establish the equivalent circuit vector model and determine the system emitter-side compensation capacitor C. t , self-inductance of transmitting coil L t and internal resistance R t Receiver impedance Z r The numerical value determines the system operating frequency f;

[0070] Step B: Detect the instantaneous value of the transmitter current and determine the input voltage amplitude U based on the phase shift angle α. s ;

[0071] Step C: Calculate the transmitter-side current amplitude I t Calculate the induced voltage U of the transmitting coil. Mt ;

[0072] Step D: Estimate mutual inductance based on the above information.

[0073] In step A, the equivalent circuit vector model of the UAV hovering wireless charging system is shown in formula (1):

[0074]

[0075] Among them, R r R is the internal resistance of the receiving coil. L For the equivalent load, L r For the self-inductance of the receiving coil, C r For receiving-side compensation capacitors, M is the mutual inductance, and I is the mutual inductance. dqt For the emitter current in an orthogonal system, I dqr Let ω0 be the receiving current in an orthogonal system, and ω0 be the system operating angular frequency.

[0076] In step A, the receiving side impedance Z r As shown in formula (2):

[0077]

[0078] In step A, the system operating frequency f is as shown in formula (3):

[0079]

[0080] In step B, the method for detecting the instantaneous value of the transmitting-side current is as follows: taking one cycle as an example, when the instantaneous value of the system output voltage is 0 and the derivative of the output voltage is greater than 0, the instantaneous value of the transmitting-side current at this time is detected and recorded as I. qt When the system output voltage reaches its positive peak value, the instantaneous value of the transmitting side current at this moment is detected and recorded as I. dt Simultaneously, the emitter-side current I under orthogonal systems dqt It can be represented as:

[0081] I dqt =I dt +jI qt (4);

[0082] In step B, the system input voltage is adjusted by phase-shift control, therefore the input voltage amplitude U s As shown in formula (5):

[0083]

[0084] Among them, U dc This is the DC power supply voltage.

[0085] In step C, the amplitude I of the transmitting side current is calculated based on the detected instantaneous value of the transmitting side current. t The formula is shown in (6):

[0086]

[0087] In step C, the induced voltage U of the transmitting coil is calculated. MtThe method is as follows: decompose the first equation in formula (1) into two equations, one with a real part and the other with an imaginary part. Let I r I represents the amplitude of the receiving current. dr For the receiving side current I in orthogonal system dqr The real part, I qr For the receiving side current I in orthogonal system dqr The imaginary part of the is obtained from the equivalent circuit vector model, as shown in the following formula (7):

[0088]

[0089] Substituting the system parameters of the energy transmitting side, the instantaneous value of the transmitting side current, and the input voltage, the induced voltage U of the transmitting coil can then be calculated. Mt As shown in formula (8):

[0090]

[0091] Among them, I r I represents the amplitude of the receiving current. dr and I qr The receiving side current I in the orthogonal system are respectively dqr The real and imaginary parts, ω0MI dr and ω0MI qr All can be calculated by decomposing the first equation in formula (1).

[0092] In step D, the method for estimating mutual inductance is as follows: Given the system parameters, the energy receiving side impedance Z... r And the operating angular frequency ω0, and the calculated transmitter current amplitude I t and the induced voltage U of the transmitting coil Mt Substituting into the receiving side loop voltage equation, the mutual inductance estimation expression shown in formula (9) is derived:

[0093]

[0094] 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 method for estimating mutual inductance in a hovering wireless charging system for unmanned aerial vehicles (UAVs), characterized in that, The charging system employed in this method includes: a transmitting system for emitting electromagnetic energy, a receiving system for receiving electromagnetic energy, and a charging control system. The transmitting system includes a DC voltage source, an inverter, a transmitting-side compensation capacitor, and a transmitting coil. The DC voltage source is connected to the DC input side of the inverter. The transmitting-side compensation capacitor and the transmitting coil are connected in series and then in parallel to the AC output side of the inverter. The receiving system includes a receiving coil, a receiving-side compensation capacitor, a rectifier, a filter capacitor, and a charging load. The transmitting coil and the receiving coil are electromagnetically coupled to each other. The receiving-side compensation capacitor and the receiving coil are connected in series and then 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, an equivalent circuit vector model, and a mutual inductance estimation module. The sampling module is used to sample the voltage and current signals on the output side of the inverter. The equivalent circuit vector model uses complex numbers to characterize the dynamic equations of the equivalent circuit of the charging system. The mutual inductance estimation module is used to estimate the mutual inductance between the transmitting coil and the receiving coil using the voltage and current signals collected by the sampling module and the equivalent circuit vector model. The method includes the following steps: Step 1: Establish an equivalent circuit vector model, determine the resistance and capacitance values ​​of the transmitting-side compensation capacitor, the self-inductance and internal resistance of the transmitting coil, the system operating angular frequency, and the receiving-side impedance Z. r ; Step 2: Detect the current and voltage signals on the inverter output side and calculate the amplitude of the transmitter current; Step 3: Determine the voltage amplitude on the inverter output side by the phase shift angle of the inverter phase shift control; Step 4: Calculate the amplitude of the induced voltage in the transmitting coil using the equivalent circuit vector model and the amplitude of the transmitting current; Step 5: Calculate the estimated value of the mutual inductance between the transmitting coil and the receiving coil based on the amplitude of the induced voltage in the transmitting coil.

2. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 1, characterized in that, In step 1, draw the equivalent circuits of the transmitting and receiving systems, and establish the following equivalent circuit vector model based on the equivalent circuits: ； In the formula, For transmitting-side compensation capacitors, For the self-inductance of the transmitting coil, R is the internal resistance of the transmitting coil. r R is the internal resistance of the receiving coil. L For the equivalent load of the receiving system, L r For the self-inductance of the receiving coil, C r M is the receiving-side compensation capacitor, M is the mutual inductance between the transmitting and receiving coils, and I is the receiving-side compensation capacitor. dqt Let I be the emitter-side current vector. dqr Let ω0 be the receiving-side current vector, and ω0 be the system operating angular frequency. This represents the input voltage amplitude.

3. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 2, characterized in that, In step 1, the system operating angular frequency is a set value, and the receiving side impedance Z... r The calculation formula is as follows: 。 4. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 2, characterized in that, In step 2, the method for detecting the current and voltage signals on the inverter output side and calculating the amplitude of the transmitter current is as follows: when the instantaneous value of the output voltage on the inverter output side is 0 and the derivative of the output voltage is greater than 0, the instantaneous value of the transmitter current at this time is sampled and recorded as I. qt When the output voltage on the inverter output side reaches its positive peak value, the instantaneous value of the transmitter current at this moment is sampled and recorded as I. dt ;set up If the amplitude is the transmitting side current, then The calculation formula is as follows: 。 5. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 2, characterized in that, In step 3, the calculation method for determining the voltage amplitude on the inverter output side based on the phase shift angle of the inverter phase shift control is as follows: ； In the formula, U dc This is the DC power supply voltage. This is the phase shift angle for inverter phase shift control.

6. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 5, characterized in that, In step 4, the method for calculating the amplitude of the induced voltage in the transmitting coil is as follows: Let I r I represents the amplitude of the receiving current. dr For the receiving side current I in orthogonal system dqr The real part, I qr For the receiving side current I in orthogonal system dqr The imaginary part of is obtained from the equivalent circuit vector model, as follows: ； Substitute the values ​​of the following known parameters: , , I qt I qt ,ω0, The following induced voltage U of the transmitting coil is further obtained. Mt The calculation formula is as follows: 。 7. The mutual inductance estimation method for a drone hovering wireless charging system according to claim 6, characterized in that, In step 5, the formula for calculating the estimated value of the mutual inductance between the transmitting coil and the receiving coil is as follows: 。

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