Data fitting method and system for piezoelectric transducer equivalent circuit parameter matching

Abstract

The application belongs to the technical field of ultrasonic transducer, and discloses a data fitting method and system for equivalent circuit parameter matching of a piezoelectric transducer. Firstly, the phase difference between voltage and current, the frequency of voltage of the piezoelectric transducer are obtained by sampling, and a nonlinear equation group containing parameters Lm, Cm, Rm and C0 is listed by using a formula. Secondly, the nonlinear equation group is converted into a linear equation group containing parameters A, B and C, and the least square method is used to obtain the values of the parameters A, B and C. Thirdly, the values of the elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer are calculated by using a formula. Finally, the parameter values of the elements L1, L2 and C1 in the matching circuit for the piezoelectric transducer are calculated by using a formula. The application can be applied to parameter matching of piezoelectric transducers in different scenes, and can be implemented in various programming environments. The piezoelectric transducer matched by using the calculation method can achieve high efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultrasonic transducers, and particularly relates to a data fitting method and system for equivalent circuit parameter matching of a piezoelectric transducer. BACKGROUND

[0002] A piezoelectric transducer is a device that converts mechanical energy and electrical energy. They use the characteristics of piezoelectric materials, which can generate voltage when subjected to force; conversely, when a voltage is applied to these materials, they will deform. This characteristic makes piezoelectric transducers very useful in various applications, such as precision positioning devices, various sensors, sonar systems, and some types of power generation equipment.

[0003] The matching circuit is particularly important for piezoelectric transducers, which can make the signal source output current and voltage in phase to reduce the reactive component in the circuit, so that the output power of the signal source is converted into the transmission power of the transducer, and the efficiency of the entire system is improved; secondly, the optimal impedance matching is to make the active resistance of the entire circuit and the output resistance of the signal source close to achieve the best output power.

[0004] Currently, dynamic matching methods on the market mostly use genetic algorithms, particle swarm algorithms, neural networks, Q value methods, and fuzzy algorithms.

[0005] Intelligent algorithms such as genetic algorithms, particle swarm algorithms, and neural network algorithms can achieve good matching in theory, but the modeling is complex, the iteration time required is long, the calculation amount is large, and a special digital processor is often needed, which increases the development cost of the system; the matching based on Q value uses the solution space section of the T-type network device to determine Q, and then calculates the network parameters through the Q value method. This method has a large fluctuation in the calculated matching element value, and the design cost is high.

[0006] Piezoelectric transducers are widely used in medical treatment, industrial processing, detection, cleaning, and other directions, and have a clear trend of development in other industries. Reasonable matching circuit design can improve the output efficiency of the transducer, and also has an important influence on the stability and life of the piezoelectric transducer.

[0007] Most of the current matching circuits are static matching, relying on manual debugging, and the dynamic matching calculation methods used in most documents are too complex, which also increases the cost of the matching circuit and the control circuit.

[0008] Through the above analysis, the problems and defects of the prior art are:

[0009] (1) The matching based on Q value uses the solution space section of the T-type network device to determine Q, and then calculates the network parameters through the Q value method. This method has a large fluctuation in the calculated matching element value, and the design cost is high.

[0010] (2) Most of the current matching circuits are static matching, which rely on manual debugging. The dynamic matching calculation methods used in most literature are too complicated and also increase the cost of matching circuits and control circuits. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a data fitting method for matching equivalent circuit parameters of piezoelectric transducers.

[0012] This invention is implemented as follows: a data fitting method for matching equivalent circuit parameters of a piezoelectric transducer includes:

[0013] Step 1: By repeatedly changing the frequency of the voltage in the ultrasonic power supply circuit, the phase difference between the voltage and current of the piezoelectric transducer is obtained. The frequency ω of the voltage;

[0014] Step 2: Substitute the corresponding phase difference and frequency for each group into the equation. Then, by combining the equations, a nonlinear system of equations containing parameters Lm, Cm, Rm, and C0 is obtained.

[0015] Step 3: Transform the nonlinear equation system containing parameters Lm, Cm, Rm, C0 into a linear equation system containing parameters A, B, C.

[0016] Step 4: Use the least squares method to fit the linear equation system containing parameters A, B, and C to obtain the values ​​of parameters A, B, and C, and then use the formula to calculate the values ​​of components Lm, Cm, Rm, and C0 in the equivalent circuit of the piezoelectric transducer.

[0017] Step 5: Calculate the parameter values ​​of components L1, L2, and C1 in the matching circuit used for the piezoelectric transducer using the formula.

[0018] The minimum number of times the voltage frequency needs to be adjusted is 3 to obtain a system of 3 equations, which can then be used to solve the system of linear equations containing three linearly independent parameters A, B, and C.

[0019] Furthermore, the step of substituting the corresponding phase difference and frequency of each group into the equation... A system of nonlinear equations with parameters Lm, Cm, Rm, and C0 is then obtained by combining the equations. The system is characterized by... Represented as:

[0020]

[0021] In the formula, is the phase difference between the voltage and the current of the piezoelectric transducer; ω is the voltage frequency; Lm is the dynamic inductance of the piezoelectric transducer equivalent circuit; Cm is the dynamic capacitance of the piezoelectric transducer equivalent circuit; Rm is the dynamic resistance of the piezoelectric transducer equivalent circuit; C0 is the static capacitance of the piezoelectric transducer equivalent circuit;

[0022] Substitute the corresponding phase difference and frequency of each group into the equation Substitute the corresponding phase difference and frequency of each group into the equation

[0023]

[0024] In the formula: is the phase difference between the voltage and the current of the piezoelectric transducer when the voltage frequency is ω1, ω2, and ω3.

[0025] Further, the nonlinear equation group containing parameters Lm, Cm, Rm, and C0 is converted into a linear equation group containing parameters A, B, and C, and the linear equation group containing parameters A, B, and C is expressed as:

[0026]

[0027] Further, the linear equation group containing parameters A, B, and C is expressed, and the relationship between A, B, and C and Lm, Cm, Rm, and C0 is expressed as:

[0028]

[0029]

[0030] Further, the B(L m ,C m ,R m ,C0) expression is expressed, and in the B(L m ,C m ,R m ,C0) expression, C0R m is much smaller than

[0031] The linear equation group containing parameters A, B, and C is fitted using the least squares method, and the values of parameters A, B, and C are fitted, and the fitting method is:

[0032] (1), the partial derivatives of parameters A, B, and C in the linear equation group containing parameters A, B, and C are calculated to obtain a matrix J, and the expression of J is as follows:

[0033]

[0034] (2), calculate the transpose matrix J of J T , J T The expression is as follows:

[0035]

[0036] (3), calculate (J T J) -1 J T ;

[0037] (4), given the initial value A_Init, B_Init, C_Init, bring it into the formula , calculate the tangent value of the phase difference between the voltage and current of the piezoelectric transducer at different frequencies Get the matrix f, the expression of f is as follows:

[0038]

[0039] (5), get the phase difference between the voltage and current of the piezoelectric transducer sampled and calculate its tangent value Get the matrix y, the expression of y is as follows:

[0040]

[0041] (6), calculate the difference r between y and f, and then use the formula to calculate Δa, the expression is as follows:

[0042] Δa=(J T J) -1 J T r=[ΔAΔBΔC] T ;

[0043] In the formula: ΔA is the difference between the actual parameter A and the initial value A_Init, ΔB is the difference between the actual parameter B and the initial value B_Init, and ΔC is the difference between the actual parameter C and the initial value C_Init;

[0044] (7), add the initial values A_Init, B_Init, C_Init and the calculated parameters ΔA, ΔB, ΔC respectively, to get the values of the actual parameters A, B and C.

[0045] Further, the formula is used to calculate the values of the elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer, characterized in that the expressions of the parameters Lm, Cm and Rm are as follows:

[0046]

[0047]

[0048] The parameter values ​​of components L1, L2, and C1 in the matching circuit used for piezoelectric transducers are calculated using formulas, characterized in that the expressions for parameters L1, L2, and C1 are:

[0049]

[0050] Another object of the present invention is to provide a data fitting system for matching equivalent circuit parameters of piezoelectric transducers, comprising:

[0051] The frequency changing module is used to obtain the phase difference between the voltage and current of the piezoelectric transducer and the voltage frequency ω by changing the frequency of the voltage in the ultrasonic power supply circuit multiple times.

[0052] The simultaneous equation module is used to substitute each corresponding phase difference and frequency into the equation and then combine them to obtain a nonlinear equation system with parameters Lm, Cm, Rm, and C0.

[0053] The conversion module is used to convert a nonlinear system of equations containing parameters Lm, Cm, Rm, and C0 into a linear system of equations containing parameters A, B, and C.

[0054] The fitting module is used to fit the linear equation system containing parameters A, B, and C using the least squares method to obtain the values ​​of parameters A, B, and C, and then use the formula to calculate the values ​​of components Lm, Cm, Rm, and C0 in the equivalent circuit of the piezoelectric transducer.

[0055] The calculation module is used to calculate the parameter values ​​of components L1, L2, and C1 in the matching circuit for the piezoelectric transducer using formulas.

[0056] Another object of the present invention is to provide a computer device including a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps of the data fitting method for matching equivalent circuit parameters of a piezoelectric transducer.

[0057] Another object of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the data fitting method for matching equivalent circuit parameters of a piezoelectric transducer.

[0058] Another objective of this invention is to provide an information data processing terminal for implementing the data fitting system for matching the equivalent circuit parameters of a piezoelectric transducer.

[0059] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0060] First, for the above existing technical problems, some creative technical effects are brought after solving the problems. The specific description is as follows:

[0061] The application provides a data fitting method for piezoelectric transducer matching.

[0062] The fitting method can be calculated by using Python, Matlab and other software on the computer, and can also be calculated by using a single-chip microcomputer containing an FPU. The calculation is simple, the application range is wide, and the cost is greatly reduced compared with other methods.

[0063] For a piezoelectric transducer with unknown equivalent circuit parameters, the parameter matching process is as follows:

[0064] Step 1, by changing the frequency of the voltage in the ultrasonic power supply circuit for multiple times, the phase difference between the voltage and the current of the piezoelectric transducer is obtained The frequency of the voltage is ω.

[0065] Step 2, each corresponding phase difference and frequency is substituted into the equation A nonlinear equation group containing parameters dynamic inductance Lm, dynamic capacitance Cm, dynamic resistance Rm and static capacitance C0 is obtained by simultaneous solving.

[0066] Step 3, the nonlinear equation group containing parameters Lm, Cm, Rm and C0 is converted into a linear equation group containing parameters A, B and C

[0067] Step 4, the linear equation group containing parameters A, B and C is fitted by using the least square method, the values of parameters A, B and C are obtained, and then the formula The values of elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer are calculated.

[0068] The method for fitting the linear equation group containing parameters A, B and C by using the least square method is as follows:

[0069] (1), the partial derivatives of parameters A, B and C in the linear equation group containing parameters A, B and C are calculated, and a matrix J is obtained, and the expression of J is as follows:

[0070]

[0071] (2), the transposed matrix J of J is calculated T , and the expression of J T is as follows:

[0072]

[0073] (3), calculate (J T J) -1 J T ;

[0074] (4), given initial values A_Init, B_Init, C_Init, bring them into the formula , calculate the tangent value of the phase difference between the voltage and the current of the piezoelectric transducer at different frequencies Get the matrix f, the expression of f is as follows:

[0075]

[0076] (5), get the phase difference between the voltage and the current of the sampled piezoelectric transducer and calculate the tangent value Get the matrix y, the expression of y is as follows:

[0077]

[0078] (6), calculate the difference r between y and f, and calculate Δa using the formula, the expression is as follows:

[0079] Δa=(J T J) -1 J T r=[ΔAΔBΔC] T ;

[0080] In the formula: ΔA is the difference between the actual parameter A and the initial value A_Init, ΔB is the difference between the actual parameter B and the initial value B_Init, and ΔC is the difference between the actual parameter C and the initial value C_Init;

[0081] (7), add the initial values A_Init, B_Init, C_Init and the calculated parameters ΔA, ΔB, ΔC respectively, to obtain the values of the actual parameters A, B and C.

[0082] Step 5, use the formula to calculate the parameter values of the elements L1, L2 and C1 in the matching circuit of the piezoelectric transducer.

[0083] The method for matching the piezoelectric transducer equivalent circuit parameters provided by the application can be applied in the optimization and development of the matching circuit and control circuit of the piezoelectric transducer, and the piezoelectric transducer matched by using the method can meet the demand of higher efficiency and lower cost, and provides a new parameter matching method for the matching of high-performance piezoelectric transducers.

[0084] Second, in the automatic matching method used at present, impedance needs to be calculated, that is, the effective value of voltage and current needs to be obtained, and the voltage and current need to be sampled to obtain a direct current signal through a signal processing circuit, and the control system analyzes the signal to obtain the effective value of the voltage and current signal. First, if a resistor is directly used for sampling during sampling, the resistance value of the sampling resistor will also have an error, and if a transformer is used for sampling, even if the transformer indicates the ratio of the input and output signals, the error of many transformers can only be controlled within 5%, and there is still an error; meanwhile, in the subsequent signal processing circuit, the circuit loss cannot be determined, so it cannot be determined whether the effective value of the sampled voltage and current signal is accurate.

[0085] The parameter matching method provided in the application only needs to obtain a phase difference in calculation, and the voltage and current are directly sampled using a resistor during sampling, so that the phase shift of the alternating current signal is not generated, in the subsequent signal processing circuit, a symmetrical circuit is adopted, that is, the signal processing circuits through which the voltage and current signals pass are completely the same, even if the signals are phase-shifted, but the frequency of the voltage signal and the current signal is completely the same, and the phase shift value is also completely the same, so that the phase difference in the signal processing circuit can be avoided, and the precision is improved.

[0086] The matching algorithm used at present is more of an intelligent algorithm, a genetic algorithm, and a neural network, which can calculate the result, but needs to obtain a large amount of data for modeling and then perform prediction, and the calculation amount is large and the calculation time is long.

[0087] The parameter matching method provided in the application directly calculates the equivalent circuit parameter value of the piezoelectric transducer by using the phase difference at three different frequencies, so that automatic matching can be performed without analyzing and modeling the sampled value and performing a large amount of calculation, and therefore the calculation speed is faster than that of other methods.

[0088] The matching method used at present adopts an intelligent algorithm, a genetic algorithm, a neural network and the like, and requires that the equipment is mostly a computer device, and the cost of the automatic matching device for the piezoelectric transducer is too high.

[0089] The matching method provided in the application is simple to calculate, and a single-chip microcomputer (for example, an STM32F4 series single-chip microcomputer) with an FPU unit can efficiently complete the calculation work, which greatly reduces the automatic matching cost of the piezoelectric transducer.

[0090] In the automatic matching method used at present, impedance needs to be calculated, that is, the effective value of voltage and current needs to be obtained, and the commonly used chip for calculating the effective value of the alternating current signal is AD536A and AD637, and the price of such a chip is nearly 100 times higher than the D flip-flop and XOR gate chip used in the application for detecting the phase difference, so that the signal processing circuit used in the matching method provided in the application has a lower cost.

[0091] Thirdly, the technical scheme of the present application fills the technical gap in the industry at home and abroad:

[0092] The parameter matching method proposed by the present application is the first to use parameter calculation for automatic matching. Previously, automatic matching was mostly achieved through intelligent algorithms or fuzzy control methods. Intelligent algorithms require the collection of multiple sets of data for modeling, and then the analysis of the parameter values of the matching components. This method is too complex, time-consuming, and costly. The fuzzy control method uses an FPGA development board for control, but the fuzzy control accuracy is not high, and the system will be unstable after a long time of operation.

[0093] The parameter matching method of the present application uses the formula between phase difference and frequency to perform data fitting to obtain the parameters of the equivalent circuit of the piezoelectric transducer, and then calculates the component parameters of the matching circuit and the resonant frequency of the piezoelectric transducer for automatic matching. Compared with intelligent algorithms, the calculation method is simple, and only three sets of samples are needed for calculation, which shortens the matching time and reduces the calculation amount. Compared with fuzzy algorithms, this method directly calculates the component parameters of the matching circuit, and has higher accuracy.

[0094] The technical scheme of the present application solves the technical problems that people have been eager to solve but have always failed to succeed:

[0095] Previously, the equipment used to calculate the values of the matching components was a PC, and Python was used for calculation. This matching method is costly. Without a PC, only the fuzzy control method can be used. In this case, it is impossible to determine the values of the matching component parameters, and the stability of fuzzy control is difficult to guarantee. Simple fuzzy control will reduce the control accuracy, and the quality of automatic matching will deteriorate. If the accuracy is to be improved, it will lead to a large search range, which will affect the speed of automatic matching.

[0096] The technical scheme of the present application only uses a single-chip microcomputer to clearly calculate the values of the matching component parameters, and the single-chip microcomputer used only needs to contain an FPU module.

[0097] Fourthly, the present application proposes a new data fitting method to address the deficiencies of the equivalent circuit parameter matching method of piezoelectric transducers in the prior art. The traditional method has low precision, complex calculation, and low efficiency in the parameter matching process, which cannot meet the actual application requirements. Especially for complex circuits and multiple frequency conditions, the existing technology cannot accurately and efficiently match the equivalent circuit parameters, resulting in the performance of the piezoelectric transducer not being fully utilized.

[0098] The application provides a data fitting method for equivalent circuit parameter matching of a piezoelectric transducer, comprising the following steps: firstly, the phase difference between the voltage and the current of the piezoelectric transducer and the voltage frequency omega are obtained by changing the frequency of the voltage in the ultrasonic power supply circuit multiple times; then, each corresponding phase difference and frequency are substituted into the equation to obtain a nonlinear equation group containing parameters Lm, Cm, Rm and C0; the nonlinear equation group containing parameters Lm, Cm, Rm and C0 is converted into a linear equation group containing parameters A, B and C; the least square method is used to perform data fitting on the linear equation group containing parameters A, B and C to obtain the values of parameters A, B and C; finally, the values of the elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer are calculated by using the formula, and the parameter values of the elements L1 and L2 and C1 in the matching circuit for the piezoelectric transducer are further calculated.

[0099] The application obtains phase difference data under different conditions by changing the voltage frequency multiple times, and uses the double-teacher distillation model and the least square method to perform parameter fitting, thereby greatly improving the precision and efficiency of the equivalent circuit parameter matching of the piezoelectric transducer.

[0100] The application has the innovation of providing a nonlinear equation group conversion and data fitting method based on a double-teacher distillation model, which uses the least square method to perform fitting on the linear equation group to accurately calculate the parameters of the equivalent circuit of the piezoelectric transducer.

[0101] Fifthly, the application introduces the method of changing the voltage frequency multiple times to obtain the phase difference between the voltage and the current of the piezoelectric transducer under different frequencies and the frequency omega, thereby solving the problem that it is difficult to accurately measure the dynamic parameters of the piezoelectric transducer in the prior art.

[0102] This invention proposes a system of nonlinear equations containing parameters Lm, Cm, Rm, and C0, which is transformed into a system of linear equations containing parameters A, B, and C through mathematical model conversion. This innovation greatly simplifies computational complexity, enabling complex nonlinear problems to be solved using linear methods. In particular, the introduction of the least squares method for data fitting of the linear equations containing parameters A, B, and C not only improves computational efficiency but also ensures the accuracy of the fitting results, thus solving the problem of low accuracy in existing technologies.

[0103] This invention optimizes the feature extraction and parameter fitting process by constructing a dual-teacher distillation model, using two teacher models to guide the training of the student model. This mathematical model combines the advantages of complex and simple models, ensuring both high-precision feature extraction and improved computational speed. This approach solves the problems of poor adaptability and low accuracy caused by a single model in existing technologies, resulting in more accurate and efficient matching of piezoelectric transducer equivalent circuit parameters.

[0104] This invention introduces specific steps such as partial derivative calculation, matrix transpose, and difference calculation in the least squares data fitting process, forming a complete and systematic parameter solution method. These innovative mathematical methods and algorithms significantly improve the accuracy and efficiency of piezoelectric transducer parameter matching, reducing experimental complexity and errors. Compared with traditional methods, this invention can accurately obtain the key parameters of piezoelectric transducers with fewer measurements, possessing significant practical application value and broad industrial application prospects, achieving a significant advancement in piezoelectric transducer performance optimization and application technology. Attached Figure Description

[0105] Figure 1 This is a flowchart of a data fitting method for matching equivalent circuit parameters of a piezoelectric transducer, provided in an embodiment of the present invention.

[0106] Figure 2 This is a block diagram of a data fitting system for matching equivalent circuit parameters of a piezoelectric transducer, provided in an embodiment of the present invention.

[0107] Figure 3 This is an equivalent circuit diagram of the piezoelectric transducer used in the embodiments of the present invention.

[0108] Figure 4 This is a fitting flowchart provided in an embodiment of the present invention.

[0109] Figure 5 This is a time graph of data fitting using an STM32F4 microcontroller under different impedances, provided in an embodiment of the present invention.

[0110] Figure 6 This is a time-fitting graph of data using Matlab under different impedances provided in an embodiment of the present invention.

[0111] Figure 7 is a time graph of data fitting under different impedances using Python provided by an embodiment of the application.

[0112] Figure 8 is a voltage and current signal graph before automatic matching provided by an embodiment of the application.

[0113] Figure 9 is a voltage and current signal graph after automatic matching provided by an embodiment of the application.

[0114] Figure 10 is a comparison graph of parameter fitting calculation speed and other methods provided by an embodiment of the application. DETAILED DESCRIPTION

[0115] In order to make the objects, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0116] As shown in Figure 1 , a data fitting method for equivalent circuit parameter matching of a piezoelectric transducer provided by an embodiment of the application includes the following steps:

[0117] S101, by changing the frequency of the voltage in the ultrasonic power supply circuit multiple times, obtaining the phase difference between the voltage and the current of the piezoelectric transducer of the voltage;

[0118] S102, substituting each corresponding phase difference and frequency into the equation and then simultaneously obtaining a nonlinear equation group containing parameters Lm, Cm, Rm and C0;

[0119] S103, converting the nonlinear equation group containing parameters Lm, Cm, Rm and C0 into a linear equation group containing parameters A, B and C;

[0120] S104, using the least square method to perform data fitting on the linear equation group containing parameters A, B and C, obtaining the values of parameters A, B and C, and then calculating the values of elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer by using the formula

[0121] S105, calculating the parameter values of elements L1 and L2 and C1 in the matching circuit for the piezoelectric transducer by using the formula

[0122] The minimum number of times of adjusting the voltage frequency is 3, and a equation group of 3 equations is obtained, so as to solve the linear equation group containing three linearly independent parameters A, B and C.

[0123] The embodiment of the present application provides the equation into which each group of corresponding phase difference and frequency is substituted After being substituted, a nonlinear equation group containing parameters Lm, Cm, Rm and C0 is obtained, and the nonlinear equation group is characterized in that is expressed as

[0124]

[0125] In the formula, is a phase difference between voltage and current of the piezoelectric transducer; ω is a voltage frequency; Lm is a dynamic inductance of an equivalent circuit of the piezoelectric transducer; Cm is a dynamic capacitance of the equivalent circuit of the piezoelectric transducer; Rm is a dynamic resistance of the equivalent circuit of the piezoelectric transducer; and C0 is a static capacitance of the equivalent circuit of the piezoelectric transducer;

[0126] The equation into which each group of corresponding phase difference and frequency is substituted After being substituted, a nonlinear equation group containing parameters Lm, Cm, Rm and C0 is obtained, and the nonlinear equation group is characterized in that

[0127]

[0128] In the formula, is a phase difference between voltage and current of the piezoelectric transducer corresponding to the voltage frequency ω1, ω2 and ω3.

[0129] The embodiment of the present application provides the nonlinear equation group containing parameters Lm, Cm, Rm and C0 into a linear equation group containing parameters A, B and C, and the linear equation group containing parameters A, B and C is expressed as

[0130]

[0131] The embodiment of the present application provides the linear equation group containing parameters A, B and C, and the relationship expression of A, B and C and Lm, Cm, Rm and C0 is

[0132]

[0133]

[0134] The embodiment of the present application provides the B(L m ,C m ,R m ,C0) expression, and the C0R m ,C m ,R m ,C0) expression in the B(L m is far less than

[0135] The least squares method is used to fit the data of a system of linear equations containing parameters A, B, and C, and the values ​​of parameters A, B, and C are obtained. The fitting method is characterized by the following:

[0136] (1) Calculate the partial derivatives of parameters A, B, and C in the system of linear equations containing parameters A, B, and C, and obtain matrix J. J is expressed as follows:

[0137]

[0138] (2) Calculate the transpose matrix J of J. T J T The expression is as follows:

[0139]

[0140] (3), calculate (J) T J) -1 J T ;

[0141] (4) Given initial values ​​A_Init, B_Init, and C_Init, substitute them into the formula. In this study, the tangent of the phase difference between the voltage and current of a piezoelectric transducer at different frequencies is calculated. The matrix f is obtained, and its expression is as follows:

[0142]

[0143] (5) Obtain the phase difference between the sampled voltage and current of the piezoelectric transducer and calculate its tangent value. The matrix y is obtained, and its expression is as follows:

[0144]

[0145] (6) Calculate the difference r between y and f, and then use the formula to calculate Δa, the expression of which is as follows:

[0146] Δa=(J T J) -1 J T r = [ΔAΔBΔC] T ;

[0147] In the formula: ΔA is the difference between the actual parameter A and the initial value A_Init, ΔB is the difference between the actual parameter B and the initial value B_Init, and ΔC is the difference between the actual parameter C and the initial value C_Init;

[0148] (7) Add the initial values ​​A_Init, B_Init, and C_Init to the calculated parameters ΔA, ΔB, and ΔC respectively to obtain the actual values ​​of parameters A, B, and C.

[0149] The embodiment of the present application provides a formula for calculating the values of elements Lm, Cm, Rm and C0 in the equivalent circuit of a piezoelectric transducer, characterized in that the expression of the parameters Lm, Cm and Rm is as follows:

[0150]

[0151]

[0152] The embodiment of the present application provides a formula for calculating the values of elements L1, L2 and C1 in the matching circuit of a piezoelectric transducer, characterized in that the expression of the parameters L1, L2 and C1 is as follows:

[0153]

[0154] As shown in Figure 2 The embodiment of the present application provides a data fitting system for matching parameters of an equivalent circuit of a piezoelectric transducer, which comprises:

[0155] The frequency changing module is configured to obtain the phase difference between the voltage and the current of the piezoelectric transducer and the frequency ω of the voltage by changing the frequency of the voltage in the ultrasonic power supply circuit multiple times.

[0156] The simultaneous module is configured to obtain a nonlinear equation group containing the parameters Lm, Cm, Rm and C0 by simultaneously solving the equation after substituting each corresponding phase difference and frequency.

[0157] The conversion module is configured to convert the nonlinear equation group containing the parameters Lm, Cm, Rm and C0 into a linear equation group containing the parameters A, B and C.

[0158] The fitting module is configured to perform data fitting on the linear equation group containing the parameters A, B and C by using the least square method, to obtain the values of the parameters A, B and C, and to calculate the values of the elements Lm, Cm, Rm and C0 in the equivalent circuit of the piezoelectric transducer by using the formula.

[0159] The calculation module is configured to calculate the values of the elements L1, L2 and C1 in the matching circuit of the piezoelectric transducer by using the formula.

[0160] Another object of the present application is to provide a computer device, which comprises a memory and a processor, and the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the data fitting method for matching parameters of an equivalent circuit of a piezoelectric transducer.

[0161] Another object of the present application is to provide a computer readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the data fitting method for matching equivalent circuit parameters of a piezoelectric transducer.

[0162] Another object of the present application is to provide an information data processing terminal for implementing the data fitting system for matching equivalent circuit parameters of a piezoelectric transducer.

[0163] The present application is embodied as follows:

[0164] The present application provides a data fitting method for matching a piezoelectric transducer, which works as follows:

[0165] The frequency of the circuit is changed to obtain the phase difference φ of the transducer and the frequency ω of the current circuit. The frequency is adjusted at least three times to obtain a system of three equations, so that a linear equation group containing three linearly independent parameters A, B and C can be solved.

[0166] The phase difference and the frequency are substituted into the equation φ(ω), and three equations are solved to obtain a nonlinear equation group containing parameters Lm, Cm, Rm and C0.

[0167] Each group of phase difference and frequency is substituted into the function The expression of φ(ω) is as follows:

[0168]

[0169] The expression of the nonlinear equation group containing parameters Lm, Cm, Rm and C0 is as follows:

[0170]

[0171] The nonlinear equation group containing parameters Lm, Cm, Rm and C0 is simplified to a linear equation group containing parameters A, B and C. The linear equation group containing parameters A, B and C is expressed as follows:

[0172]

[0173] The parameters A, B and C are obtained by least square fitting, and the values of the equivalent circuit elements Lm, Cm, Rm and C0 of the piezoelectric transducer are calculated. The specific method of obtaining parameters A, B and C by least square fitting is as follows:

[0174] The partial derivatives of A, B and C are calculated and arranged into a matrix J, which is expressed as follows:

[0175]

[0176] Transposing J, we get J T , J T The expression of J is as follows:

[0177]

[0178] Through the above calculation, we get (J T J) -1 J T ;

[0179] Given the initial values A_Init, B_Init, C_Init (calculated by Lm_Init, Cm_Init, Rm_Init, C0_Init using the formula), we bring them into the formula φ(ω) to calculate tanφ at different frequencies, and list the matrix f. The expression of f is as follows:

[0180] f = [tanφ1 | f1 tanφ2 | f2 tanφ3 | f3] T

[0181] Get the sampled tanφ, and list the matrix y. The expression of y is as follows:

[0182] y = [tanφ1 | y1 tanφ2 | y2 tanφ3 | y3] T

[0183] Calculate the difference between y and f as r, and then calculate Δa. The expression of Δa is as follows:

[0184] Δa = (J T J) -1 J T r = [ΔA ΔB ΔC] T

[0185] Add A_Init, B_Init, C_Init and ΔA, ΔB, ΔC respectively to complete the fitting, and get A, B, C.

[0186] Calculate the parameter values of Lm, Cm, Rm, C0.

[0187] The expression of A, B, C is as follows:

[0188]

[0189] Among them, C0R m in the expression of B is much smaller than Therefore, it can be omitted in the calculation, and the values of Lm, Cm, Rm, C0 can be calculated more easily.

[0190] Since C0 is a static capacitance, its change is very small when the piezoelectric transducer is working, thus, it is more convenient for the following calculation to assume that C0 is known, and the expression of the equivalent circuit element Lm, Cm, Rm of the piezoelectric transducer is calculated according to parameters A, B, C.

[0191]

[0192] The parameter values of the matching elements L1, L2, C1 of the T-type matching circuit are calculated.

[0193] The expression of the matching elements L1, L2, C1 of the T-type matching circuit is calculated by using Lm, Cm, Rm, C0.

[0194]

[0195] The present application provides a new fitting algorithm for the complex calculation method in the dynamic matching of the piezoelectric transducer, a set of equations is derived through the functional relationship between the phase difference and the frequency, the nonlinear equation set is changed into a linear equation set containing new parameters, the least square method is used for the data fitting of the linear equation set, the value of the new parameter is calculated, the equivalent circuit parameter value of the piezoelectric transducer is obtained, and finally the element parameter value of the matching circuit is obtained.

[0196] As shown in Figure 3 The equivalent circuit of the piezoelectric transducer adopted by the present application is a series circuit, which contains a dynamic inductance Lm, a dynamic capacitance Cm, a dynamic resistance Rm, and a static capacitance C0, wherein Lm, Cm, and Rm are connected in series, and C0 is connected in parallel. Thus, the relationship of φ(ω) can be derived as follows:

[0197]

[0198] The converted formula is as follows:

[0199]

[0200] Thus, the expression of the equivalent circuit element parameters Lm, Cm, and Rm of the piezoelectric transducer is as follows:

[0201]

[0202] In summary, the present application includes the conversion of the nonlinear equation φ(ω) into a linear equation, the calculation, the fitting of the parameters by using the least square method, the calculation of the element parameters of the equivalent circuit of the transducer, and finally the calculation of the element values in the matching circuit.

[0203] II. Application Examples. In order to prove the creativity and technical value of the technical solutions of the present application, this part is the application examples of the technical solutions of the claims on specific products or related technologies.

[0204] The following will be specifically described with examples:

[0205] The application examples of the present application use data of a specific piezoelectric transducer for experiments, and the parameter values are Lm=2000e-3H, Cm=45e-12F, Rm=85Ω, C0=17e-9F. The initial value parameters are given as Lm_init=1850e-3H, Cm_init=40e-12F, Rm_init=80Ω.

[0206] The matrix J is:

[0207]

[0208] The transpose matrix J of J is calculated T Then, J is calculated T J is:

[0209]

[0210] The inverse of J is obtained (J T J) -1 is:

[0211]

[0212] Using the initial value parameters Lm_init=1850e-3H, Cm_init=40e-12F, Rm_init=80Ω to calculate A_Init, B_Init, C_Init, which are brought into the formula φ(ω), the f is obtained:

[0213] f=[-166620 -3504 -83001] T

[0214] The tanφ when the parameter values are Lm=2000e-3H, Cm=45e-12F, Rm=85Ω, C0=17e-9F is obtained, and the matrix y is listed as:

[0215] y=[-42709 -19612 -239432] T

[0216] The difference between f and y is calculated, and r is:

[0217] r=[-123910 16107 156431] T

[0218] The values ​​of ΔA, ΔB, and ΔC are calculated using the formula, and Δa is:

[0219] Δa=[7.27*10 -11 1.878 -3.4*10 10 ] T

[0220] Therefore, we can obtain A = -8 * 10¹⁰, B = 17.801, and C = -9.9 * 10¹⁰. Using the formulas to calculate Lm, Cm, and Rm, we get Lm = 2016.6e⁻³H, Cm = 44.6e⁻¹²F, and Rm = 86.4Ω. The relative errors for Lm are 0.83%, Cm is 0.89%, and Rm is 1.65%, proving that this algorithm can accurately calculate the component parameters in the equivalent circuit of the piezoelectric transducer.

[0221] Figure 4 This is a fitting flowchart provided in an embodiment of the present invention;

[0222] This application example is implemented on three different devices or software:

[0223] Example 1:

[0224] Fitting is performed on a microcontroller by changing the value of resistor Rm in the equivalent circuit and performing data fitting multiple times.

[0225] 1. Substitute the corresponding phase difference and frequency of each group into the equation φ(ω), and solve the equations simultaneously to obtain a nonlinear equation system containing parameters Lm, Cm, Rm, and C0;

[0226] 2. Transform the nonlinear equation system containing parameters Lm, Cm, Rm, C0 into a linear equation system containing parameters A, B, C;

[0227] 3. After obtaining the values ​​of parameters A, B, and C by data fitting using the least squares method, the values ​​of components Lm, Cm, Rm, and C0 in the equivalent circuit of the piezoelectric transducer are calculated using the formula;

[0228] The procedure for fitting is as follows:

[0229]

[0230]

[0231]

[0232] 4. Calculate the parameter values ​​of components L1, L2, and C1 in the matching circuit used for the piezoelectric transducer using the formula. The fitting calculation time for different impedances is as follows: Figure 5 As shown.

[0233] Example two:

[0234] The data fitting is performed multiple times by changing the value of the resistance Rm in the equivalent circuit using Matlab.

[0235] 1. Substitute each corresponding phase difference and frequency into the equation φ(ω), and solve the equations to obtain a nonlinear equation group containing parameters Lm, Cm, Rm, and C0;

[0236] 2. Convert the nonlinear equation group containing parameters Lm, Cm, Rm, and C0 into a linear equation group containing parameters A, B, and C;

[0237] 3. Perform data fitting using the least squares method to obtain the values of parameters A, B, and C, and calculate the values of elements Lm, Cm, Rm, and C0 in the equivalent circuit of the piezoelectric transducer using the formula;

[0238] The program in this part is:

[0239]

[0240]

[0241] 4. Calculate the parameter values of elements L1, L2, and C1 in the matching circuit for the piezoelectric transducer using the formula.

[0242] The fitting calculation time for different impedances is shown in Table 1. Figure 6

[0243] Example three:

[0244] The data fitting is performed multiple times by changing the value of the resistance Rm in the equivalent circuit using Python.

[0245] 1. Substitute each corresponding phase difference and frequency into the equation φ(ω), and solve the equations to obtain a nonlinear equation group containing parameters Lm, Cm, Rm, and C0;

[0246] 2. Convert the nonlinear equation group containing parameters Lm, Cm, Rm, and C0 into a linear equation group containing parameters A, B, and C;

[0247] 3. After obtaining the values of parameters A, B, and C by performing data fitting using the least squares method, calculate the values of elements Lm, Cm, Rm, and C0 in the equivalent circuit of the piezoelectric transducer using the formula;

[0248] 4. Calculate the parameter values of elements L1, L2, and C1 in the matching circuit for the piezoelectric transducer using the formula.

[0249] The fitting calculation time for different impedances is shown in Table 1. Figure 7 ​as shown.

[0250] It should be noted that the embodiments of the present application can be realized by hardware, software, or a combination of software and hardware. The hardware part can be realized by special logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or a specially designed hardware. Those skilled in the art can understand that the above-mentioned devices and methods can be realized by computer executable instructions and / or included in processor control code, such as provided on a carrier medium, such as a magnetic disk, CD or DVD-ROM, a programmable memory, such as a read-only memory (firmware), or a data carrier, such as an optical or electronic signal carrier. The device of the present application and its modules can be realized by hardware circuit, such as ultra-large-scale integrated circuit or gate array, semiconductor, such as logic chip, transistor, etc., or programmable hardware device, such as field programmable gate array, programmable logic device, etc., or by software executed by various types of processors, or by a combination of the above-mentioned hardware circuit and software, such as firmware.

[0251] III. Evidence of the effects related to the embodiments. The embodiments of the present application have achieved some positive effects in the process of research and development or use, and indeed have great advantages compared with the prior art. The following contents are described in combination with the data and graphs of the test process.

[0252] The embodiment of the present application uses data of a specific piezoelectric transducer for experiment, and the parameter values are Lm=2000e-3H, Cm=45e-12F, Rm=85Ω, C0=17e-9F. The resonant frequency is 16785Hz. In order to reduce the influence of frequency change on the operation of the transducer, the frequency change step is set to 15Hz when the frequency is changed, that is, the phase difference is measured at 16785Hz, 16800Hz, 16815Hz and 16830Hz, and the initial value parameters are given as Lm_init=1850e-3H, Cm_init=40e-12F, Rm_init=80Ω. Data fitting is performed by using an STM32F4 single-chip microcomputer. The specific steps are as follows:

[0253] (1) The sampling circuit uses resistance to sample the voltage and current signals. The voltage and current signals enter the zero-crossing comparator after the filtering circuit to convert the signals into square waves with high level 5V and low level 0V. The square waves enter the D flip-flop to obtain the leading or lag relationship of the voltage and current, enter the XOR gate to obtain the square wave signal, and the duty cycle*180° is the absolute value of the phase difference. The single-chip microcomputer obtains the duty cycle of the square wave signal output by the XOR gate through PWM input capture, and thus the phase difference can be obtained. The voltage frequency is directly controlled by the PWM signal output by the single-chip microcomputer, so detection is not required.

[0254] (2) Single-chip three times change frequency, get three corresponding frequency and phase difference, as shown in Table 1.

[0255]

[0256] Table 1. Circuit frequency and phase difference (3) using STM32F4 single-chip microcomputer for data fitting, the program of fitting part is as follows:

[0257]

[0258]

[0259]

[0260] B=Dataa[1]+B_value;

[0261] C=Dataa[2]+C_value;

[0262] Cm=(-(4*A*C*C0-B*B*C0)+sqrt((4*A*C*C0-B*B*C0)*(4*A*C*C0-B*B*C0)

[0263] -4*A*C*(4*A*C*C0*C0-B*B*C0*C0))) / (2*A*C);

[0264] Rm=-(Cm+C0) / C / Cm / Cm;

[0265] Lm=B*Cm*Rm / (2*C0+Cm);

[0266] }

[0267] (4) Single-chip microcomputer output signal control matching circuit, voltage and current signal before and after matching as shown in Figure 8 , 9.

[0268] Meanwhile, the application compares the calculation speed with other algorithm calculation speed, as shown in Figure 10 , the calculation speed of the application is better than other algorithms.

[0269] The above is only a specific embodiment of the application, but the protection scope of the application is not limited to this, any skilled person in the art can make any modification, equivalent replacement and improvement within the technical range disclosed by the application, which should be covered in the protection scope of the application.

Claims

1. A data fitting method for matching equivalent circuit parameters of a piezoelectric transducer, characterized in that, Includes the following steps: Step 1: By repeatedly changing the frequency of the voltage in the ultrasonic power supply circuit, the phase difference between the voltage and current of the piezoelectric transducer is obtained. The frequency ω of the voltage; Step 2: Substitute the corresponding phase difference and frequency for each group into the equation. Then, by combining the equations, we obtain a result containing parameter L. m C m R m The nonlinear equation system of C0; Step 3, include parameter L m C m R m The nonlinear equation system of C0 is transformed into a linear equation system containing parameters A, B, and C. Step 4: Use the least squares method to fit the linear equations containing parameters A, B, and C to obtain the values ​​of parameters A, B, and C. Then, use the formula to calculate the element L in the equivalent circuit of the piezoelectric transducer. m C m R m The value of C0; Step 5: Calculate the parameter values ​​of components L1, L2, and C1 in the matching circuit used for the piezoelectric transducer using the formula. The minimum number of times the voltage frequency needs to be adjusted is 3 to obtain a system of 3 equations, which can then be used to solve the system of linear equations containing three linearly independent parameters A, B, and C. The step involves substituting the corresponding phase difference and frequency of each group into the equation. Then, by combining the equations, we obtain a result containing parameter L. m C m R m The nonlinear equations of C0 Represented as: ； In the formula, This refers to the phase difference between the voltage and current of the piezoelectric transducer. L is the voltage frequency; m C is the dynamic inductance of the equivalent circuit of the piezoelectric transducer; m R is the dynamic capacitance of the equivalent circuit of the piezoelectric transducer. m C0 is the dynamic resistance of the equivalent circuit of the piezoelectric transducer; C0 is the static capacitance of the equivalent circuit of the piezoelectric transducer. Substitute the corresponding phase difference and frequency for each group into the equation. Then, by combining the equations, we obtain a result containing parameter L. m C m R m The nonlinear equation system of C0 is expressed as follows: ； In the formula: , , The voltage frequency is , , The phase difference between the voltage and current of the piezoelectric transducer at that time; The term containing parameter L m C m R m The nonlinear equation system of C0 is transformed into a linear equation system with parameters A, B, and C. The linear equation system with parameters A, B, and C is expressed as: 。 2. The data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in claim 1, characterized in that, The expression for the linear equation system containing parameters A, B, and C, where A, B, C and L... m C m R m The relational expression for C0 is: ； ； 。 3. The data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in claim 2, characterized in that, expression, In the expression Less than ; The least squares method was used to fit the data of the linear equation system containing parameters A, B, and C, and the values ​​of parameters A, B, and C were obtained. The fitting method is as follows: (1) Calculate the partial derivatives of parameters A, B, and C in the system of linear equations containing parameters A, B, and C, and obtain the matrix J. The expression of J is as follows: ； (2) Calculate the transpose matrix of J. , The expression is as follows: ； (3) Calculate ; (4) Given initial values ​​A_Init, B_Init, and C_Init, substitute them into the formula. In this study, the tangent of the phase difference between the voltage and current of a piezoelectric transducer at different frequencies is calculated. We obtain matrix f, and the expression for f is as follows: ； (5) Obtain the phase difference between the sampled voltage and current of the piezoelectric transducer and calculate its tangent value. We obtain matrix y, whose expression is as follows: ； (6) Calculate the difference r between y and f, and then use the formula to calculate Its expression is as follows: ； In the formula: The difference between the actual parameter A and the initial value A_Init. The difference between the actual parameter B and the initial value B_Init. The difference between the actual parameter C and the initial value C_Init; (7) Combine the initial values ​​A_Init, B_Init, and C_Init with the calculated parameters. , , Add them together to get the values ​​of the actual parameters A, B, and C.

4. The data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in claim 1, characterized in that, The formula is used to calculate element L in the equivalent circuit of the piezoelectric transducer. m C m R m The value of C0, parameter L m C m R m The expression is as follows: ； ； ； The parameter values ​​of components L1, L2, and C1 in the matching circuit used for the piezoelectric transducer are calculated using the formula. The expressions for parameters L1, L2, and C1 are as follows: ； ； 。 5. A data fitting system for matching equivalent circuit parameters of a piezoelectric transducer, characterized in that, The data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in any one of claims 1-4, wherein the data fitting system for matching equivalent circuit parameters of a piezoelectric transducer comprises: The frequency changing module is used to obtain the phase difference between the voltage and current of the piezoelectric transducer and the voltage frequency ω by changing the frequency of the voltage in the ultrasonic power supply circuit multiple times. The simultaneous equation module is used to substitute the corresponding phase difference and frequency into the equations and then solve them simultaneously to obtain a result containing parameters L. m C m R m The nonlinear equation system of C0; The conversion module is used to convert data containing parameter L. m C m R m The nonlinear equation system of C0 is transformed into a linear equation system containing parameters A, B, and C. The fitting module is used to fit a system of linear equations containing parameters A, B, and C using the least squares method, obtaining the values ​​of parameters A, B, and C, and then using formulas to calculate the element L in the equivalent circuit of the piezoelectric transducer. m C m R m The value of C0; The calculation module is used to calculate the parameter values ​​of components L1, L2, and C1 in the matching circuit for the piezoelectric transducer using formulas.

6. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in any one of claims 1-4.

7. A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the data fitting method for matching equivalent circuit parameters of a piezoelectric transducer as described in any one of claims 1-4.

8. An information data processing terminal, characterized in that, The information data processing terminal is used to implement the data fitting system for matching equivalent circuit parameters of piezoelectric transducers as described in claim 5.

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