A constant amplitude control method, device and ultrasonic transducer system

Abstract

The present application relates to a constant amplitude control method, device and ultrasonic transducer system, including: obtaining the output voltage vector, input current vector and the first phase difference between the output voltage vector and the input current vector of the ultrasonic transducer; obtaining the dynamic branch current vector of the resonant branch of the ultrasonic transducer according to the input current vector and the first phase difference; judging whether the dynamic branch current value is within the target current interval, the dynamic branch current value is the length of the dynamic branch current vector; if not, adjusting the driving power of the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current interval, so that the dynamic branch current value is within the target current interval. Constant amplitude control of ultrasonic waves can be achieved by controlling the dynamic branch current of the ultrasonic transducer.

Description

Technical Field

[0001] The present application relates to the field of ultrasound, and in particular to a constant amplitude control method, device and ultrasonic transducer system. Background Art

[0002] Ultrasonic transducers are devices that convert input electrical power into mechanical power. During the operation of ultrasonic equipment, the amplitude of its vibration system will decay, and the amplitude decay will affect the working effect of the ultrasonic equipment. Therefore, it is necessary to control the amplitude of the ultrasonic system to be constant in order to improve the efficiency and stability of the ultrasonic equipment. Summary of the invention

[0003] Based on this, it is necessary to provide a constant amplitude control method, device and ultrasonic transducer system to address the problem of unstable ultrasonic amplitude in the prior art.

[0004] In order to achieve the above objectives, in a first aspect, the present application provides a constant amplitude control method for controlling an ultrasonic transducer, the method comprising:

[0005] Acquire an output voltage vector, an input current vector, and a first phase difference between the output voltage vector and the input current vector of the ultrasonic transducer;

[0006] Acquire a dynamic branch current vector of a resonant branch of the ultrasonic transducer according to the input current vector and a first phase difference;

[0007] Determine whether a dynamic branch current value is within a target current interval, wherein the dynamic branch current value is the length of the dynamic branch current vector;

[0008] If not, the driving power of the ultrasonic transducer is adjusted according to the relationship between the dynamic branch current value and the target current range so that the dynamic branch current value is within the target current range.

[0009] In one embodiment, adjusting the driving power of the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current range includes:

[0010] If the dynamic branch current value is less than the minimum value of the target current interval, increasing the driving power;

[0011] If the dynamic branch current value is greater than the maximum value of the target current interval, the driving power is reduced.

[0012] In one embodiment, before determining whether the dynamic branch current value is within the target current range, the method further includes:

[0013] Get the reference current and current error range;

[0014] A target current interval is obtained according to the reference current and the current error interval.

[0015] In one embodiment, before adjusting the driving power of the ultrasonic transducer, the method further comprises:

[0016] adjusting the driving frequency of the ultrasonic transducer according to the output voltage vector, the input current vector and the first phase difference so that the driving frequency is within a preset frequency range;

[0017] Wherein, the resonant branch includes a resonant inductor and a resonant capacitor, and the preset frequency range is determined according to the values ​​of the resonant inductor and the resonant capacitor.

[0018] In one embodiment, adjusting the driving frequency of the ultrasonic transducer according to the output voltage vector, the input current vector and the first phase difference comprises:

[0019] Acquire a second phase difference between the dynamic branch current vector and the output voltage vector according to the output voltage vector, the input current vector and the first phase difference;

[0020] When the second phase difference is less than 0, reducing the driving frequency;

[0021] When the second phase difference is greater than 0, the driving frequency is increased.

[0022] In one embodiment, the second phase difference is obtained by using the following formula:

[0023]

[0024] in, is the input current vector, is the output voltage vector, θ is the first phase difference, and φ is the second phase difference.

[0025] In one embodiment, the preset frequency is the frequency when the ultrasonic transducer is in a resonant state.

[0026] In a second aspect, the present application provides a constant amplitude control device for controlling an ultrasonic transducer, comprising:

[0027] A data acquisition module, used for acquiring an output voltage vector and an input current vector of the ultrasonic transducer;

[0028] A first phase difference acquisition module, used to acquire a first phase difference between an output voltage vector and an input current vector of the ultrasonic transducer;

[0029] A branch current acquisition module, used for acquiring a dynamic branch current vector of a resonant branch of the ultrasonic transducer according to the input current vector and the first phase difference;

[0030] A judging module, used to judge whether a dynamic branch current value is within a target current interval, wherein the dynamic branch current value is the length of the dynamic branch current;

[0031] A power regulating module is used to, if not, regulate the driving power of the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current interval so that the dynamic branch value is within the target current interval.

[0032] In a third aspect, the present application also provides an ultrasonic transducer system, comprising:

[0033] Ultrasonic transducer;

[0034] A driving board, connected to the ultrasonic transducer and used to drive the ultrasonic transducer;

[0035] A sampling module, located on the driving board, for sampling the output voltage vector and input current vector of the ultrasonic transducer;

[0036] A processor, located on the driver board, is used to obtain a first phase difference between the output voltage vector and the input current vector in the form of a digital signal; obtain a dynamic branch current vector of the resonant branch of the ultrasonic transducer according to the input current vector and the first phase difference; determine whether the dynamic branch current value is within a target current interval, the dynamic branch current value being the length of the dynamic branch current; if not, adjust the driving power of the driver board to drive the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current interval, so that the dynamic branch value is within the target current interval.

[0037] In one embodiment, the processor includes:

[0038] A signal processor, a phase discriminator, an effective value converter, a controller, a power amplifier and a frequency regulator, wherein the signal processor is respectively connected to the sampling module and the phase discriminator, the controller is respectively connected to the phase discriminator and the power amplifier, the effective value converter is respectively connected to the signal processor and the controller, and the frequency regulator is connected to the phase discriminator.

[0039] The above constant amplitude control method controls the current of the resonant branch so that the current value of the dynamic branch can be stabilized within the target current range, thereby achieving the purpose of maintaining a constant amplitude and realizing constant amplitude control of the ultrasonic wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 is a flow chart of a constant amplitude control method provided in one embodiment;

[0042] Figure 2 is an equivalent circuit diagram of a piezoelectric transducer provided in an embodiment;

[0043] Figure 3 is one of the vector relationship diagrams of an ultrasonic transducer provided in an embodiment;

[0044] Figure 4 The second vector relationship diagram of an ultrasonic transducer provided in an embodiment;

[0045] Figure 5 The third vector relationship diagram of an ultrasonic transducer provided in an embodiment;

[0046] Figure 6 A fourth vector relationship diagram of an ultrasonic transducer provided in an embodiment;

[0047] Figure 7 is a schematic diagram of a constant amplitude control device provided in an embodiment;

[0048] Figure 8 Schematic diagram of an ultrasonic transducer system provided in one embodiment.

[0049] Description of reference numerals:

[0050] Ultrasonic transducer: 100; data acquisition module: 101; first phase difference acquisition module: 102; branch current acquisition module: 103; judgment module: 104; power regulation module: 105; drive board: 106; sampling module: 107; signal processor: 108; phase discriminator: 109; effective value converter: 110; controller: 111; power amplifier: 112; frequency regulator: 113; output interface: 114. DETAILED DESCRIPTION

[0051] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0053] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe vector relationships, and these terms are only used to distinguish the first vector relationship from another vector relationship. For example, without departing from the scope of this application, a first phase difference may be referred to as a second phase difference, and similarly, a second phase difference may be referred to as a first phase difference. Both the first phase difference and the second phase difference are phase differences, but they are not the same phase difference.

[0054] The ultrasonic system includes an ultrasonic generator, an ultrasonic transducer and other tools and equipment. The ultrasonic generator can convert industrial frequency AC into ultrasonic frequency oscillations to drive the ultrasonic transducer to work. The oscillating current of the ultrasonic frequency enters the ultrasonic transducer, and the ultrasonic transducer can convert it into mechanical energy and then transmit it out. In addition to allowing the ultrasonic transducer to work normally, the above-mentioned generator can also stabilize the output power and perform frequency tracking. In the application of ultrasonic technology, the attenuation of the amplitude will affect the normal operation. Due to factors such as temperature and load changes, the resonant frequency of the ultrasonic transducer will shift under the same excitation voltage. However, if the frequency of the generator power signal does not change, the system will be detuned, resulting in a decrease in amplitude. At the same time, even in the case of good frequency tracking, when the working conditions change and the additional dielectric loss increases, the amplitude will still attenuate. Therefore, it is necessary to control the ultrasonic amplitude to improve the stability of the operation of the ultrasonic equipment.

[0055] See also Figure 1 , Figure 1 : is a flow chart of a constant amplitude control method provided in an embodiment. The present application provides a constant amplitude control method for controlling an ultrasonic transducer. The method includes steps S100, S200, S300 and S400, which are specifically as follows:

[0056] Step S100: acquiring an output voltage vector, an input current vector, and a first phase difference between the output voltage vector and the input current vector of the ultrasonic transducer.

[0057] Common ultrasonic transducers include magnetostrictive transducers, piezoelectric transducers, and electrostatic transducers. This embodiment uses a piezoelectric transducer as an example for explanation, which utilizes the piezoelectric effect of certain single crystal materials and the electrostrictive effect of certain polycrystalline materials to convert electrical energy into acoustic energy. Specifically, Figure 2 is an equivalent circuit diagram of a piezoelectric transducer provided in an embodiment, wherein Figure 2 The static branch and dynamic branch of (a) are connected in parallel. The static branch includes capacitor C o , the dynamic branch includes the equivalent inductance L m , equivalent capacitance C m And the equivalent resistance R m When the voltage driving frequency of the piezoelectric transducer is equal to the mechanical resonance frequency f s When Figure 2 As shown in (b), the resonant inductance L of the dynamic branch m and resonant capacitor C m When series resonance occurs, the dynamic branch can be simplified to an equivalent resistance R m .

[0058] Although online measurement of amplitude is very difficult, given that the amplitude of the piezoelectric transducer is proportional to the dynamic branch current, the dynamic branch current can be selected as the control parameter to control the amplitude stability according to the change of the dynamic branch current value. However, the dynamic branch current cannot be directly measured when the piezoelectric transducer is working. Therefore, it is necessary to establish the relationship between the input current and output voltage of the piezoelectric transducer and the dynamic branch current when it is working, and use this relationship to characterize the dynamic branch current.

[0059] Therefore, when the piezoelectric transducer is powered on and initialized, it is necessary to obtain the output voltage vector, input current vector and the first phase difference between the output voltage vector and the input current vector of the piezoelectric transducer, and characterize the dynamic branch current vector through the vector relationship between the three.

[0060] Step S200: obtaining a dynamic branch current vector of a resonant branch of the ultrasonic transducer according to an input current vector and a first phase difference.

[0061] like Figure 3 As shown, the output voltage vector As the horizontal axis, the current flowing through the static branch as the vertical axis, establish a vector relationship diagram, the vertical axis can be expressed as jwC o The phase of the static branch current leads the output voltage vector 90°. Figure 2 It can be known that the dynamic branch current vector It can be obtained by formula (1):

[0062]

[0063] The dynamic branch current vector is converted into exist Figure 3 When the dynamic branch current vector With the output voltage vector When they are parallel, that is, the two are in phase, the resonant branch is purely resistive, and the ultrasonic transducer works at the series resonant frequency point. It can be seen from the figure that:

[0064]

[0065] So in the resonant state, according to the input current vector The product of the cosine value of the first phase difference θ can represent the dynamic branch current vector of the resonant branch of the ultrasonic transducer.

[0066] Step S300: determining whether the dynamic branch current value is within the target current interval, where the dynamic branch current value is the length of the dynamic branch current vector.

[0067] It is understandable that in order to maintain the constant amplitude, the current of the dynamic branch needs to be controlled. When the dynamic branch current value fluctuates, if it is still within the target current range, it means that the amplitude is controlled. If it is not within the target current range, it means that the amplitude is not maintained stable, and step S400 needs to be taken to control the amplitude to be constant.

[0068] Step S400: According to the relationship between the dynamic branch current value and the target current range, the driving power of the ultrasonic transducer is adjusted to make the dynamic branch current value within the target current range.

[0069] The amplitude can be adjusted by changing the output power of the ultrasonic generator, that is, the driving power of the ultrasonic transducer, so that the dynamic branch current value is stable within the target current range to keep the amplitude constant. When the constant amplitude control method of the above embodiment is applied to ultrasonic machining, the quality of ultrasonic machining can be guaranteed.

[0070] In the above example, by controlling the dynamic branch current of the resonant branch, the amplitude can be kept constant, thereby achieving constant amplitude control of the ultrasonic wave.

[0071] In one embodiment, step S400 further includes the following steps of adjusting the driving power of the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current interval: if the dynamic branch current value is less than the minimum value of the target current interval, increasing the driving power; if the dynamic branch current value is greater than the maximum value of the target current interval, reducing the driving power. By changing the output of the ultrasonic generator, the dynamic branch current value is kept within the target current interval to maintain a constant amplitude of the ultrasonic transducer.

[0072] In one embodiment, before step S300 determines whether the dynamic branch current value is within the target current range, the following steps are further included: obtaining a reference current and a current error range, and obtaining a target current range according to the reference current and the current error range.

[0073] The reference current can be the current value corresponding to the ultrasonic transducer in the resonant state or the current value that can make the amplitude reach the expected value. When the dynamic branch current value is close to the reference current, the error between the two is already very small, so a current error interval is set to form a target current interval. Within this interval, it can be considered that the amplitude of the ultrasonic transducer has reached the expected amplitude. Since the resonant frequency and expected amplitude of the ultrasonic transducer will change during operation, the above target current interval can be flexibly determined according to the working conditions.

[0074] In one embodiment, before step S400 adjusts the driving power of the ultrasonic transducer, the following steps are also included: adjusting the driving frequency of the ultrasonic transducer according to the output voltage vector, the input current vector and the first phase difference so that the driving frequency is within a preset frequency range; wherein the resonant branch includes a resonant inductor and a resonant capacitor, and the preset frequency range is determined according to the values ​​of the resonant inductor and the resonant capacitor.

[0075] It is understandable that the method for stabilizing the amplitude can be to first perform frequency tracking to put the system in a resonant state, and then adjust the driving power, or directly change the driving power without frequency modulation, but this cannot guarantee that the amplitude control is performed on the basis of successful frequency tracking. Since at the resonant frequency point, the impedance of the ultrasonic transducer is the smallest and the output current is the largest, the efficiency of converting its electrical energy into mechanical energy is the highest, and one of the purposes of amplitude control is to improve the efficiency of the ultrasonic equipment, so the efficiency of the first method in maintaining a constant amplitude under a resonant state is higher than that of the second method. Therefore, in the face of amplitude attenuation, it is necessary to make the driving frequency close to the preset frequency on the basis of frequency tracking, and then change the driving power to achieve amplitude control. In one embodiment, the preset frequency is the frequency when the ultrasonic transducer is in a resonant state.

[0076] according to Figure 2 (b) The dynamic branch is simplified to an equivalent resistor in the resonant state, where the series resonant frequency f s It can be expressed as:

[0077]

[0078] Therefore, the preset frequency can be determined according to the above formula (3), and the preset frequency range is determined accordingly, allowing a very small error range between the driving frequency and the preset frequency.

[0079] Specifically, see Figure 3 , when the dynamic branch current is in phase with the output voltage vector, there exists The resonant branch is purely resistive; see Figure 4 and Figure 5 , when the dynamic branch current lags behind the output voltage vector, there exists The resonant branch appears inductive; see Figure 6 , when the dynamic branch current leads the output voltage vector, there is The resonant branch is capacitive. That is, when Sometimes, there is at this time and In phase, the ultrasonic transducer works at the series resonant frequency point. When the ultrasonic generator drives the ultrasonic transducer, the current flowing to the ultrasonic transducer is defined as the positive direction. At this time, there is only one frequency point satisfy Therefore, there will be no loss of lock in the phase-locked control, and the stability is better than the phase-locked control based on the current and voltage zero phase. Therefore, through the vector relationship between the output voltage vector, the input current vector and the first phase difference, it can be known whether the ultrasonic transducer is in a resonant state. If not, the driving frequency of the ultrasonic transducer is adjusted so that the driving frequency is within the preset frequency range.

[0080] In one embodiment, the above-mentioned adjusting the driving frequency of the ultrasonic transducer according to the output voltage vector, the input current vector and the first phase difference includes the following steps: obtaining the second phase difference between the dynamic branch current vector and the output voltage vector according to the output voltage vector, the input current vector and the first phase difference. When the second phase difference is less than 0, the driving frequency is reduced; when the second phase difference is greater than 0, the driving frequency is increased; when the second phase difference is equal to 0, the driving frequency is kept unchanged.

[0081] Specifically, in one embodiment, when Figure 3 When the dynamic branch shown is in a resonant state, the second phase difference φ is obtained using the following formula:

[0082]

[0083] in, is the input current vector, is the output voltage vector, θ is the first phase difference, and φ is the second phase difference. The second phase difference is the dynamic branch current vector With the output voltage vector The phase difference is due to Therefore The second phase difference φ can be used as a feedback quantity for frequency tracking: when φ<0, the resonant branch is inductive, and the resonant frequency is less than the driving frequency. The driving frequency of the ultrasonic transducer needs to be reduced accordingly; when φ>0, the resonant branch is capacitive, and the resonant frequency is greater than the driving frequency. The driving frequency of the ultrasonic transducer needs to be increased accordingly; when φ=0, the resonant branch is purely resistive, and the resonant frequency is equal to the driving frequency, keeping the driving frequency of the ultrasonic transducer unchanged.

[0084] By adjusting the driving frequency according to the second phase difference, the ultrasonic transducer can be stably operated at the series resonant frequency point, and then the driving power is adjusted to control the dynamic branch current value so that it is within the target current range, thereby achieving constant amplitude control.

[0085] The present application provides a constant amplitude control device for controlling an ultrasonic transducer, comprising: a data acquisition module 101, a first phase difference acquisition module 102, a branch current acquisition module 103, a judgment module 104 and a power adjustment module 105. Figure 7 As shown, Figure 7 Schematic diagram of the constant amplitude control device provided in this embodiment.

[0086] Specifically, the data acquisition module 101 is connected to the ultrasonic transducer 100, and is used to obtain the output voltage vector and input current vector of the ultrasonic transducer 100; the first phase difference acquisition module 102 is connected to the data acquisition module 101, and is used to obtain the first phase difference between the output voltage vector and the input current vector of the ultrasonic transducer 100; the branch current acquisition module 103 is connected to the data acquisition module 101 and the first phase difference acquisition module 102 respectively, and is used to obtain the dynamic branch current vector of the resonant branch of the ultrasonic transducer 100 according to the input current vector and the first phase difference; the judgment module 104 is connected to the branch current acquisition module 103, and is used to judge whether the dynamic branch current value is within the target current interval, and the dynamic branch current value is the length of the dynamic branch current; the power adjustment module 105 is connected to the judgment module 104 and the ultrasonic transducer 100 respectively, and is used to adjust the driving power of the ultrasonic transducer 100 according to the relationship between the dynamic branch current value and the target current interval when the dynamic branch current value is not within the target current interval, so that the dynamic branch value is within the target current interval.

[0087] The present application also provides an ultrasonic transducer system, comprising: an ultrasonic transducer 100 and a driving board 106, wherein a sampling module 107 and a processor are located on the driving board 106. Figure 8 As shown, Figure 8 A schematic diagram of an ultrasonic transducer system provided in one embodiment.

[0088] Specifically, the driving board 106 is connected to the ultrasonic transducer 100 and is used to drive the ultrasonic transducer 100 to work. The driving board 106 includes a sampling module 107, a processor and an output interface 114, wherein the processor includes a signal processor 108, a phase discriminator 109, an effective value converter 110, a controller 111, a power amplifier 112 and a frequency regulator 113. The sampling module 107 collects the current signal and the voltage signal through the sampling resistor, and transmits the collected signals to the signal processor 108, which includes a zero-crossing comparator circuit and a filter.

[0089] In one embodiment, the zero-crossing comparator circuit converts the voltage and current signals into square wave signals and sends them to the phase discriminator 109. The phase discriminator 109 can use a field-programmable gate array (FPGA) as a phase detection chip. The FPGA can use the model EP4CE10F17C8 to obtain the digital value of the first phase difference between the current and the voltage, and transmit the digital first phase difference and some other control signals (contact signals) to the controller 111 through the universal parallel port (UPP).

[0090] In other embodiments, the filter converts the voltage and current signals into bandpass filtered voltage and current signals and sends them to the effective value converter 110, thereby obtaining the voltage effective value and the current effective value, and transmitting them to the controller 111, wherein the effective value converter 110 may be of the model AD8436. The controller 111 obtains the digital value of the voltage effective value and the current effective value through its own analog-to-digital converter.

[0091] Specifically, the controller 111 can adopt a digital signal processor (Digital Signal Processing, DSP), and the DSP processor can be of model TMS320F28377D. During the operation of the controller 111, the dynamic branch current value is obtained through the built-in virtual reference feedback tuning (VRFT) algorithm, and the relationship between the dynamic branch current value and the target current range is judged through the fuzzy PID controller, and the judgment result is transmitted to the power amplifier 112 for amplitude control. The power amplifier 112 includes a multiplier, and the multiplier can be of model AD633. At the same time, the digital quantities of the collected voltage effective value and current effective value, and the digital quantity of the first phase difference are used to obtain the relationship between the driving frequency signal and the preset frequency range based on the frequency tracking of the vector method, and the result is transmitted to the phase discriminator 109 through the serial peripheral interface (Serial Peripheral Interface, SPI), and the phase discriminator 109 encodes and generates the corresponding frequency control word, which is transmitted to the frequency regulator 113 for frequency control, so that the driving frequency of the ultrasonic transducer 100 is close to the resonant frequency. Optionally, the frequency regulator 113 can use a direct digital frequency synthesizer (Direct Digital Synthesizer, DDS), and the DDS chip can be used as AD9833. After the above amplitude control is completed, the electrical signal is transmitted to the ultrasonic transducer 100 through the output interface 114.

[0092] It should be understood that although Figure 1The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple steps or multiple stages. These steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed in turn or alternately with other steps or at least part of the steps or stages in other steps.

[0093] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0094] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features of the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A constant amplitude control method, characterized in that: For controlling an ultrasonic transducer, the method comprises: Acquire an output voltage vector, an input current vector, and a first phase difference between the output voltage vector and the input current vector of the ultrasonic transducer; Acquire a dynamic branch current vector of a resonant branch of the ultrasonic transducer according to the input current vector and a first phase difference; Determine whether a dynamic branch current value is within a target current interval, wherein the dynamic branch current value is the length of the dynamic branch current vector; If not, the second phase difference between the dynamic branch current vector and the output voltage vector is obtained by using the following formula according to the output voltage vector, the input current vector and the first phase difference; in, is the input current vector, is the output voltage vector, is the first phase difference, is the second phase difference; When the second phase difference is less than 0, the driving frequency is reduced; when the second phase difference is greater than 0, the driving frequency is increased so that the driving frequency is within a preset frequency range; the resonant branch includes a resonant inductor and a resonant capacitor, and the preset frequency range is determined according to the values ​​of the resonant inductor and the resonant capacitor; According to the relationship between the dynamic branch current value and the target current interval, the driving power of the ultrasonic transducer is adjusted to make the dynamic branch current value within the target current interval.

2. The constant amplitude control method according to claim 1, characterized in that: The step of adjusting the driving power of the ultrasonic transducer according to the relationship between the dynamic branch current value and the target current interval includes: If the dynamic branch current value is less than the minimum value of the target current interval, increasing the driving power; If the dynamic branch current value is greater than the maximum value of the target current interval, the driving power is reduced.

3. The constant amplitude control method according to claim 1, characterized in that: Before determining whether the dynamic branch current value is within the target current range, the method further includes: Get the reference current and current error range; A target current interval is obtained according to the reference current and the current error interval.

4. The constant amplitude control method according to claim 1, characterized in that: The preset frequency is the frequency when the ultrasonic transducer is in a resonant state.

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