Half-controlled variable-scan mode ultrasonic excitation signal generation device and method

Abstract

The application provides a half-controlled step frequency scanning variable scanning mode ultrasonic excitation signal generating device and method, and relates to the technical field of ultrasonic power supplies.The device structure comprises four parts of a power stage power conversion circuit, signal sampling and conditioning, a main controller and peripheral circuit, and a button and display circuit.The power stage power conversion circuit is composed of AC-DC conversion, power regulation, DC-AC inversion, impedance matching and series tuning modules.Through the program design of the main controller, different ultrasonic excitation signal frequency modes can be realized, including a constant frequency mode of keeping the center frequency, a constant scanning mode of constant step frequency scanning, and a variable scanning mode of half-controlled step frequency scanning.The variable scanning mode of half-controlled step frequency scanning provides a novel frequency excitation mode for ultrasonic auxiliary processing, is beneficial to the resonance of ultrasonic waves and complex material liquid, and helps to improve the acoustic-cavitation yield.

Description

TECHNICAL FIELD

[0001] The application relates to a half-controlled step-sweep mode ultrasonic excitation signal generating device and method, and belongs to the technical field of power ultrasonic excitation power supply. BACKGROUND

[0002] With the development of power electronics and switching power supply technology, the implementation mode of power ultrasonic is more and more diversified, and the application range is also becoming more and more extensive. From ultrasonic cleaning, it is gradually popularized to industrial and agricultural spraying, mechanical industry processing, food and biological raw material processing, etc. When the ultrasonic transducer works, the acoustic-electric conversion efficiency is an extremely important technical index, which requires that the front-end ultrasonic excitation signal generating device, namely the ultrasonic generator, and the transducer have excellent impedance matching and resonance performance.

[0003] In addition, the frequency mode of the ultrasonic excitation signal generating device (namely the ultrasonic generator) is another important index affecting its effect. According to whether the ultrasonic generator works at the resonance frequency (center frequency) of the transducer, there are currently commonly used constant frequency mode working at the center frequency and sweep frequency mode deviating from the center frequency according to a set step. The constant frequency mode can lock the resonance frequency through sound tracking or electric tracking, so that the ultrasonic generator can still quickly adjust to the real-time center frequency when the environmental parameters change or the ultrasonic transducer is mechanically damaged. The frequency adjustment in the sweep frequency mode is relatively complex in power supply design. The Chinese invention patent "Pulse multi-frequency ultrasonic biological processing device, method and application of sweep frequency mode" (ZL200910212707.8) proposes an excitation signal output by the ultrasonic generator, which is based on the center frequency and changes in the positive and negative steps with a constant step in the vicinity of the center frequency. The sweep frequency ultrasonic biological processing device greatly improves the shortcomings of constant frequency ultrasonic and improves the processing efficiency. However, both constant frequency and constant step sweep frequency ultrasonic are regularly changed at the center frequency or in the vicinity of the center frequency. When the processing object is a complex liquid material, the oscillation frequency of the liquid material is randomly changed. When the ultrasonic frequency and the oscillation frequency of the liquid material are greatly different, strong cavitation cannot be generated, and the ultrasonic effect is affected.

[0004] Therefore, the application discloses an electric signal frequency adjusting device and method for exciting an ultrasonic transducer, which can generate a half-controlled step frequency signal based on the center frequency and constantly changing, so as to adapt to the complex ultrasonic cavitation process of the processing object and improve the acoustic-cavitation conversion efficiency of the ultrasonic effect. SUMMARY

[0005] In order to overcome the defects of the prior art, the application discloses a sweep frequency ultrasonic power supply device capable of generating sweep frequency ultrasonic waves with a frequency in a certain range and an arbitrary step length, and an implementation method thereof, and the application widens the frequency excitation mode of the ultrasonic waves and provides a wider frequency spectrum adaptation for the application of power ultrasonic waves.

[0006] A half-controlled step sweep frequency ultrasonic excitation signal generating device, which comprises a power stage power conversion circuit, a signal sampling and conditioning circuit, a main controller and a peripheral circuit, a key and a display module. The parts are connected by wires for electric signal transmission. The power stage power conversion circuit is the main line, and the signal sampling and conditioning circuit is connected to the output end of the power stage circuit; the driving signal output by the main controller and peripheral circuit is connected to the gate of the power switch tube of the power stage circuit; the key and display module are used for command input and main state signal display of the power stage circuit, but the signal input and output are realized by the main controller. The power stage power conversion circuit refers to a high-power main circuit, which is divided into AC-DC conversion, power regulation, DC-AC inversion, impedance matching and series tuning modules. In order to convert the 220V, 50Hz AC power into the high-frequency excitation electric signal required by the ultrasonic transducer, AC-DC conversion is first performed to realize rectification. The power size is controlled during or after this process, and the power level starts from zero and is adjusted to the maximum power in multiple gears.

[0007] The power stage inversion and frequency modulation circuit converts the DC power obtained by AC-DC conversion into a high-frequency electric signal in front of the transducer. The high-frequency AC signal is a square wave pulse, and the center frequency is adjustable in the range of 16-70 kHz, so as to be suitable for ultrasonic transducers of different frequency bands.

[0008] The high-frequency AC signal is matched and adjusted before being connected to the ultrasonic transducer. The application uses a high-frequency transformer to adjust the impedance and a series inductor to adjust the total load to be close to pure resistance, so as to maximize the working efficiency of the ultrasonic generator, and when the output electric signal frequency is the center frequency, the transducer can work in a resonant state, the inductive reactance of the circuit and the capacitive reactance of the transducer are offset, and the maximum active power is output.

[0009] The signal sampling and conditioning circuit includes voltage and current sampling at the output end. The sampled electric signal is sent to the A / D conversion interface of the main controller for phase-locked tracking after proportional amplification by an operational amplifier. The center frequency of the transducer is searched by comparing the phase difference between the voltage signal and the current signal to adjust the frequency.

[0010] The main controller of the half-controlled step sweep frequency ultrasonic generator is a single-chip microcomputer, and the peripheral circuit of the single-chip microcomputer comprises a frequency locking controller, a reset circuit and an interface module and the like. The frequency locking controller receives the phase difference of the sampling voltage and current signals, and sends the phase difference to the single-chip microcomputer, and the single-chip microcomputer sends the duty cycle of the power adjustment and the gate drive signal of the inverter stage power switch tube, and the final output signal of the device is determined by the frequency control mode of the main controller.

[0011] The key and display part is a window for manual operation and display of the working state of the power device. The operation key is used to set the power level, frequency mode (constant frequency, constant step sweep frequency or half-controlled step sweep frequency), start and stop of the device and the like. The liquid crystal screen displays the power size, voltage and current effective value and the like.

[0012] Based on the above device, the application further discloses a half-controlled step sweep frequency ultrasonic excitation signal generation method, which is performed according to the following steps:

[0013] Step one: initializing the register and setting the frequency initial value as the nominal value f0 of the ultrasonic transducer.

[0014] Step two: center frequency capture stage

[0015] (1) The signal sampling and conditioning circuit transmits the voltage u o and current signal i o output by the ultrasonic generator to the frequency locking module, and calculates the phase difference φ dif therebetween.

[0016] (2) The phase difference φ dif is sent to the A / D sampling port of the single-chip microcomputer, and the frequency of the drive pulse signal output by the PWM port of the single-chip microcomputer is rapidly increased or decreased by setting the frequency step value m|φ dif | in the single-chip microcomputer program. If φ dif > 0, f0 is increased by m|φ dif | steps, and if φ dif < 0, f0 is decreased by m|φ dif | steps, wherein m is a step coefficient.

[0017] (3) When the phase difference |φ dif | ≤ φ e (φ e is the allowed phase error), the current PWM port output frequency is the resonance frequency (center frequency) f c of the ultrasonic generator and the transducer.

[0018] Step three: frequency mode detection and execution stage

[0019] The frequency mode set by the end of the scanning button is scanned, and there are three buttons SW1, SW2 and SW3 to set three different ultrasonic frequency modes, which correspond to the constant frequency mode of keeping the center frequency, the constant scanning mode of constant step frequency scanning and the variable scanning mode of half-controlled step frequency scanning respectively. In different modes, the frequency of the excitation electric signal emitted by the ultrasonic generator is called the working frequency f w .

[0020] (1) When the main controller detects that SW1 is pressed, the frequency control enters the constant frequency working subroutine. The PWM port output frequency of the single-chip microcomputer is f c , and in this mode f w = f c , and the change trend of the ultrasonic excitation signal frequency with time is shown in the attached Figure 3 .

[0021] (2) When the main controller detects that SW2 is pressed, the frequency control enters the constant scanning working subroutine. In the subroutine, f w is periodically changed, and the change range is (f c -f △ )~(f c +f △ ), and f △ can be set between 1kHz and 2kHz. f w increases from f c to (f c +f △ ), and then gradually decreases to (f c -f △ ), and then gradually increases to f c , and the time of the above-mentioned complete process is called a frequency period. In a frequency period, f w increases and decreases by f s , and f s can be set between 1Hz and 10Hz. f △ and f s are pre-adjusted and set before starting the ultrasonic generator, that is, the step of frequency change after the ultrasonic generator starts in the constant scanning mode is constant. The change trend of the ultrasonic excitation signal frequency with time in this mode is shown in the attached Figure 4 .

[0022] (3) When the main controller detects that SW3 is pressed, the frequency control enters the variable scanning working subroutine. In the subroutine, f w is constantly changed, and the change range is (f c -f △ )~(f c +f △ ), and f △It can be set between 1 kHz ~ 2 kHz.f w From f c , it is increased to (f c + f △ ), then gradually decreased to (f c - f △ ), and then gradually increased to f c , the time of the above complete process is called a frequency period. In a frequency period, f w is increased or decreased by f s , f s can be set between 1 Hz ~ 10 Hz. But unlike the step (2) in step three, after the ultrasonic generator is started, the step of frequency change in any adjacent two frequency periods is unknown, generated by a pseudo-random function, and it is possible that the steps in any two adjacent frequency periods are not equal. It can be seen that the rate of frequency increase or decrease is not controllable, but the minimum and maximum values of the rate are 1 Hz and 10 Hz respectively, and cannot exceed the range, so it is called a semi-controlled step frequency sweep mode. Under this mode, the trend of the frequency change of the ultrasonic excitation signal with time is shown in Fig. 2. Figure 5

[0023] (4) The steps (2) and (3) of the above step three, in a frequency period, the trend of frequency change can be two isosceles triangles or two right triangles, which is realized by a frequency control subroutine.

[0024] (5) If the three buttons SW1, SW2 and SW3 are not pressed, the same frequency mode as step (1) is executed, and the constant frequency working subroutine is entered. The PWM port output frequency of the single-chip microcomputer is f c , and under this mode, f w = f c .

[0025] The beneficial effects of the present application are that by using switching power supply technology and single-chip microcomputer program control, a plurality of different ultrasonic excitation signal generation modes can be generated on the same ultrasonic device, including a constant frequency mode with a working frequency equal to a center frequency, a constant sweep mode with a constant step frequency sweep, and a variable sweep mode with a semi-controlled step frequency sweep. To exert more effective ultrasonic cavitation effect and promote the significant physicochemical property change of the processing object, novel ultrasonic working modes are provided. When the device and method are applied to the extraction of organic acids, the effective components of waste fruit peels such as pomelo peels, the constant frequency, constant sweep and variable sweep modes all increase the extraction rate compared with no ultrasonic action, and the semi-controlled step frequency sweep in the variable sweep mode has the best extraction effect, with an extraction rate increase of 64.24%. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a structure diagram of an ultrasonic generator device.​

[0027] Figure 2 This is a flowchart of the ultrasonic generator's operation.

[0028] Figure 3 This is a frequency trend graph of an ultrasonic generator in constant frequency mode.

[0029] Figure 4 This is a frequency trend graph of an ultrasonic generator in constant sweep mode.

[0030] Figure 5 This is a frequency trend graph of the ultrasonic generator in variable sweep mode. Detailed implementation method:

[0031] To clearly illustrate the content of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings.

[0032] A semi-controlled stepping frequency sweeping ultrasonic excitation signal generator, as shown in the attached... Figure 1 As shown, its structure comprises four main components: a power-stage power conversion circuit, signal sampling and conditioning, a main controller and peripheral circuits, and a button and display module. These components are connected by wires for signal transmission. The power-stage power conversion circuit serves as the main circuit, with signal sampling and conditioning connected to its output. The drive signals output by the main controller and peripheral circuits are connected to the gates of the power switching transistors in the power-stage circuit. The button and display module provides command input and displays key status signals for the power-stage circuit, but the input and output of these signals are handled by the main controller. The power-stage power conversion circuit, a high-power main circuit, is further divided into several modules: AC-DC conversion, power regulation, DC-AC inversion, impedance matching, and series tuning. To convert the 220V, 50Hz AC power into the high-frequency excitation signal required by the ultrasonic transducer, AC-DC conversion is performed for rectification. Power control is implemented during or after this process, with power levels starting from zero and gradually adjusted to the maximum power.

[0033] The power stage inverter and frequency modulation circuit converts the DC power obtained from AC-DC conversion into a high-frequency electrical signal at the front end of the transducer. The high-frequency AC signal is a square wave pulse, and the center frequency is adjustable in the range of 16 to 70 kHz to be suitable for ultrasonic transducers of different frequency bands.

[0034] Before the high-frequency AC signal is connected to the ultrasonic transducer, impedance matching and adjustment are performed. This invention uses a high-frequency transformer to adjust the impedance and a series inductor to adjust the total load to be close to pure resistivity. This maximizes the working efficiency of the ultrasonic generator and enables the transducer to work in a resonant state when the output electrical signal frequency is the center frequency. The inductive reactance of the circuit cancels out the capacitive reactance of the transducer, and the maximum active power is output.

[0035] The signal sampling and conditioning circuit includes voltage and current sampling at the output terminal. The sampled electrical signal is amplified proportionally by an operational amplifier and then sent to the A / D conversion interface of the main controller for phase-locked tracking. The frequency is adjusted by comparing the phase difference between the voltage signal and the current signal to search for the center frequency of the transducer.

[0036] The main controller of the semi-controlled stepper sweep frequency ultrasonic generator is a microcontroller. The microcontroller's peripheral circuitry includes a frequency lock controller, a reset circuit, and an interface module. The frequency lock controller receives the phase difference between the sampled voltage and current signals and sends the phase difference to the microcontroller. The microcontroller then issues the duty cycle for adjusting the power and the gate drive signals for the inverter stage power switching transistors. The final output signal of the device is determined by the frequency control method of the main controller.

[0037] The button and display section serves as the window for manual operation and displays the power supply's working status. The operation buttons are used to set the power level, frequency mode (constant frequency, constant step sweep, or semi-controlled step sweep), and to start and stop the device. The LCD screen displays the power level, voltage, and RMS current values.

[0038] Based on the above device, the present invention also discloses a method for generating a semi-controlled stepping frequency-sweeping ultrasonic excitation signal, as shown in the appendix. Figure 2 As shown, proceed with the following steps:

[0039] Step 1: Initialize the register and set the initial frequency value to the nominal value f0 of the ultrasonic transducer.

[0040] Step 2: Center Frequency Acquisition Phase

[0041] (1) The signal sampling and conditioning circuit converts the voltage u output by the ultrasonic generator into voltage u. o and current signal i o The data is transmitted to the frequency locking module, which calculates the phase difference φ between the two components. dif .

[0042] (2) The phase difference φ dif The signal is sent to the A / D sampling port of the microcontroller, and the frequency step value m|φ is set in the microcontroller program. dif This causes the frequency of the drive pulse signal output from the microcontroller's PWM port to increase or decrease rapidly. If φ dif >0, so that f0 is m|φ dif |Increase the step size, if φ dif <0, so that f0 is equal to m|φ dif | The step decreases, where m is the step coefficient.

[0043] (3) When the phase difference |φ dif |≤φ e Time (φ)e For the allowed phase error, the current PWM port output frequency is the resonance frequency (center frequency) f of the ultrasonic generator and transducer c .

[0044] Step three: frequency mode detection and execution phase

[0045] Scan the frequency mode set by the key end, there are SW1, SW2 and SW3 three keys to set three different ultrasonic frequency modes, corresponding to the constant frequency mode of keeping the center frequency, constant sweep mode of constant step sweep frequency and variable sweep mode of half-controlled step sweep frequency. In different modes, the frequency of the excitation signal emitted by the ultrasonic generator is called the working frequency f w .

[0046] (1) When the main controller detects that SW1 is pressed, the frequency control enters the constant frequency working subroutine. The output frequency of the PWM port of the single-chip microcomputer is f c , the driving pulse in this mode, f w = f c , the trend of the ultrasonic excitation signal frequency changing with time in this mode is shown in the attached Figure 3 .

[0047] (2) When the main controller detects that SW2 is pressed, the frequency control enters the constant sweep working subroutine. In the subroutine, f w is constantly changing periodically, the range of change is (f c -f △ )~(f c +f △ ), f △ can be set between 1kHz~2kHz. f w increases from f c to (f c +f △ ), and then gradually decreases to (f c -f △ ), and then gradually increases to f c , the time of the above complete process is called a frequency period. In a frequency period, f w increases and decreases by f s , f s can be set between 1Hz~10Hz. f △ and f s are pre-adjusted and set before starting the ultrasonic generator, that is, the step of frequency change after the ultrasonic generator starts in the constant sweep mode is constant. The trend of the ultrasonic excitation signal frequency changing with time in this mode is shown in the attached Figure 4 .

[0048] (3) When the main controller detects that SW3 is pressed, the frequency control enters the variable-scan working subroutine. In the subroutine, f w is constantly changing, and the range of change is (f c -f △ )~(f c +f △ ), and f △ may be set between 1 kHz and 2 kHz. f w increases from f c to (f c +f △ ), and then gradually decreases to (f c -f △ ), and then gradually increases to f c . The time of one complete process is called a frequency period. In one frequency period, f w increases or decreases by f s , and f s may be set between 1 Hz and 10 Hz. However, unlike step three (2), after the ultrasonic generator is started, the step of frequency change in any two adjacent frequency periods is unknown and is generated by a pseudo-random function, and it is possible that the steps in any two adjacent frequency periods are not equal. It can be seen that the rate of frequency increase or decrease is not controllable, but the minimum and maximum values of the rate are 1 Hz and 10 Hz, respectively, and cannot exceed this range, so it is called a semi-controlled step-scan frequency mode. In this mode, the change trend of the frequency of the ultrasonic excitation signal with time is shown in FIG. 6. Figure 5

[0049] (4) In steps three (2) and (3), the change trend of the frequency in one frequency period can be two isosceles triangles or two right-angled triangles, which is realized by the frequency control subroutine.

[0050] (5) If SW1, SW2, and SW3 are not pressed, the same frequency mode as step three (1) is executed, and the constant-frequency working subroutine is entered. The frequency of the driving pulse output by the PWM port of the single-chip microcomputer is f c , and in this mode, f w =f c .

[0051] Example 1

[0052] ​The ultrasonic generator operates in constant frequency mode. A piezoelectric transducer with a nominal value f0 of 28kHz is connected to the output terminal of the ultrasonic generator described in this invention. The mains power supply is turned on, the device is started, and the power level is adjusted to maximum. Then, the SW1 key is pressed, and the ultrasonic generator operates in constant frequency mode. The voltage and current signals across the ultrasonic transducer are measured using an oscilloscope. The frequency of the output voltage signal is displayed as the center frequency of 27.5kHz (f0). c The peaks and troughs of the voltage and current signals occur at approximately the same time, indicating a small phase difference. This means the ultrasonic generator can capture the transducer's resonant frequency. (See attached image) Figure 3 As shown, at this time, the operating frequency f w The center frequency is constant and equal to the center frequency f. c .

[0053] The extraction of organic acids from grapefruit peel was conducted using an ultrasonic generator operating in the aforementioned constant frequency mode. Fresh grapefruit peel was dried, pulverized, and passed through a 40-mesh sieve. Using 95% ethanol as the solvent, the ultrasonic treatment lasted 30 minutes, with a material-to-liquid mass-to-volume ratio of 1:20 g / mL, an ultrasonic temperature of 80℃, and an ultrasonic power of 60 W / L. The extract was centrifuged at 10000×g for 10 minutes, and the supernatant was used to determine the total organic acid content. The calculated extraction rate of organic acids was 2.92 mg / g.

[0054] Example 2

[0055] The ultrasonic generator operates in constant sweep mode. The frequency variation amplitude f is set in the program of the main controller microcontroller. △ The operating frequency is 1kHz, f. w The increment / decrement step is f s =10Hz. Connect the piezoelectric transducer with a nominal value f0 of 28kHz to the output terminal of the ultrasonic generator described in this invention, turn on the power frequency power supply, start the device, and adjust the power level to the maximum. Use an oscilloscope to measure the voltage and current signals across the ultrasonic transducer, and display the frequency of the output voltage signal as the center frequency of 27.5kHz (f c Then press the SW2 key, and the ultrasonic generator will operate in a constant-rate sweep mode with 10Hz steps. The frequency change trend is shown in the attached figure. Figure 4 As shown, at this time, the operating frequency f w Within one frequency cycle, first from f c Gradually increase to a maximum value of 28.5kHz (f c +f △ ), and then gradually decrease to a minimum value of 26.5kHz (f c -f △ Then increase it to the center frequency of 27.5kHz (f c The trend of change can be not only attached.Figure 4 The isosceles triangle shown can also be set to a right triangle trend by the constant scanning work subroutine.

[0056] The ultrasonic generator works in the constant scanning mode to carry out the extraction test of the organic acid of the grapefruit peel. Fresh grapefruit peel is dried, crushed, and passed through a 40-mesh sieve. The volume fraction of 95% ethanol is used as the solvent, the ultrasonic time is 30 min, the solid-liquid mass volume ratio is 1:20 g / mL, the ultrasonic temperature is 80°C, and the ultrasonic power is 60 W / L. The extraction liquid is centrifuged at 10,000 x g in a high-speed centrifuge for 10 min, and the supernatant is taken to determine the total organic acid content, and the extraction rate of the organic acid is calculated to be 3.21 mg / g.

[0057] Example 3

[0058] The ultrasonic generator works in the variable scanning mode. The program in the main controller single-chip microcomputer is set to a frequency change amplitude f △ of 1 kHz, and the working frequency f w is increased or decreased by a step generated by a pseudo-random function. The f s generated by the main controller single-chip microcomputer in each machine cycle is random and uncontrollable, but the minimum value and the maximum value are limited to 1 Hz and 10 Hz, respectively, and cannot exceed this range. The piezoelectric transducer with a nominal value f0 of 28 kHz is connected to the output end of the ultrasonic generator described in the application, the power supply is turned on, the device is started, and the power level is adjusted to the maximum. The oscilloscope is used to measure the voltage signal and the current signal across the ultrasonic transducer, and the frequency of the output voltage signal is displayed as the center frequency 27.5 kHz (f c ). Then, the SW3 key is pressed, and the ultrasonic generator works in the variable scanning mode with uncontrollable step f s . The trend of frequency change is shown in the attached Figure 5 , at this time, the working frequency f w is first gradually increased from the center frequency 27.5 kHz (f c ) to the maximum value 28.5 kHz (f c + f △ ), then gradually decreased to the minimum value 26.5 kHz (f c - f △ ), and then increased to the center frequency 27.5 kHz (f c ). The trend of change can not only be the isosceles triangle shown in the attached Figure 5 , but also can be set to a right triangle trend by the variable scanning work subroutine.

[0059] The ultrasonic generator works in the above variable scanning mode to carry out the extraction test of the organic acid of the grapefruit peel. Fresh grapefruit peel is dried, crushed, and passed through a 40-mesh sieve. Ethanol with a volume fraction of 95% is used as the solvent, the ultrasonic time is 30 min, the solid-liquid mass volume ratio is 1:20 g / mL, the ultrasonic temperature is 80°C, and the ultrasonic power is 60 W / L. The extraction liquid is centrifuged at 10,000 x g for 10 min in a high-speed centrifuge, and the supernatant is taken to determine the total organic acid content, and the extraction rate of the organic acid is calculated to be 4.73 mg / g.

[0060] Control test of Example 1, Example 2 and Example 3: The control is the extraction of organic acid without ultrasonic. Except that there is no ultrasonic effect in the extraction process, the other extraction parameters are the same as those of the above three examples, and the extraction rate of the organic acid is calculated to be 2.88 mg / g. The three ultrasonic modes all increase the extraction rate of the organic acid, and the constant frequency, constant scanning and variable scanning modes increase the extraction rate of the organic acid by 1.39%, 11.46% and 64.24% respectively compared with the case without ultrasonic effect.

[0061] The above is a specific embodiment of the three frequency modes of the application, which further illustrates the technical problems solved by the application and the technical solutions. It should be understood that the above is only a specific embodiment of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application should be included within the scope of the application.

Claims

1. A signal generating method of a half-controlled step-swept variable-scan mode ultrasonic excitation signal generating apparatus, characterized by According to the following steps: Step one: initialize the register and set the frequency initial value as the nominal value of the ultrasonic transducer f 0; Step two: center frequency capture phase (1) Signal sampling and conditioning circuit transmits the voltage and current signals outputted by the ultrasonic generator to the frequency locking module, and calculates the phase difference between the two signals u o i o φ dif ;​​ (2) the phase difference φ dif is sent to the A / D sampling port of the single-chip microcomputer, and the driving pulse signal frequency output by the PWM port of the single-chip microcomputer is made to increase or decrease rapidly by setting a frequency step value m in the single-chip microcomputer program; if φ dif > 0, the driving pulse signal frequency output by the PWM port of the single-chip microcomputer is made to increase by m steps; if φ dif 0, the driving pulse signal frequency output by the PWM port of the single-chip microcomputer is made to decrease by m steps f 0 to increase by m φ dif steps; if φ dif < 0, the driving pulse signal frequency output by the PWM port of the single-chip microcomputer is made to decrease by m steps; and if f 0 to decrease by m φ dif steps, wherein m is a step coefficient. (3) when phase difference φ dif |≤ φ e the current PWM port output frequency is the resonance frequency of the ultrasonic generator and the transducer f c ; wherein φ e is the allowable phase error, and the resonance frequency is the center frequency; Step three: frequency mode detection and execution phase The scanning button end sets the frequency mode, and there are three buttons SW1, SW2 and SW3 to set three different ultrasonic frequency modes, which correspond to the constant frequency mode of keeping the center frequency, the constant scanning mode of constant step frequency scanning and the variable scanning mode of half-controlled step frequency scanning respectively; in different modes, the frequency of the excitation electric signal emitted by the ultrasonic wave generator is called the working frequency f w ; (1) When the main controller detects that SW1 is pressed, the frequency control enters the constant frequency working subroutine; the frequency of the PWM port output of the single-chip microcomputer is f c drive pulses, in this mode f w = f c ; (2) When the main controller detects that SW2 is pressed, the frequency control enters the constant sweep working subroutine; in the subroutine f w is constantly changing periodically, the range of change is (f f c - f △ )~(f f c + f △ ), f △ is set between 1 kHz ~2 kHz; f w from f c increases to (f f c + f △ ), and then gradually decreases to (f f c - f △ ), and then gradually increases to f c The time of the above complete process is called a frequency period; within a frequency period, f w the step of increasing and decreasing is f s , f s is set between 1 Hz ~10 Hz; f △ and f s are pre-adjusted and set before starting the ultrasonic wave generator, that is, the step of frequency change after the ultrasonic wave generator is started in the constant sweep mode is constant; (3) When the main controller detects that SW3 is pressed, the frequency control enters the variable scanning subprogram; in the subprogram f w is constantly changing, the range of change is ( f c - f △ )~( f c + f △ ), f △ set between 1 kHz ~2 kHz; f w from f c increased to ( f c + f △ ), gradually decreased to ( f c - f △ ), and then gradually increased to f c The time of the above complete process is called a frequency period; within a frequency period, f w increment or decrement step f s , f s set between 1 Hz ~10 Hz; but unlike step three (2), after the ultrasonic generator is started, the frequency change step in any two adjacent frequency periods is unknown, generated by a pseudo-random function. It can be seen that the rate of frequency increase or decrease is uncontrollable, but the minimum and maximum values of the rate are 1 Hz and 10 Hz, respectively, and cannot exceed this range, therefore, it is called a semi-controlled step frequency scanning mode; (4) the step three (2) and (3) steps, a frequency cycle, the trend of frequency change is two isosceles triangles or two right triangles, which is realized by the frequency control subprogram; (5) If SW1, SW2 and SW3 are not pressed, the same frequency mode as step three (1) is executed, and the constant frequency operation subroutine is entered; the frequency of the PWM port output of the single-chip microcomputer is f c the driving pulse, and in this mode f w = f c .

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