A method and system for separating cavitation noise during ultrasonic coagulation

Abstract

The present invention discloses a method and system for separating cavitation noise in ultrasonic coagulation. The method comprises: obtaining the original spectrum of the cavitation noise signal; performing segmentation, fitting and smoothing processing on the original spectrum to obtain a fitting spectrum; determining the frequency point corresponding to the maximum amplitude of the fitting spectrum in the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; determining the harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise amount; determining the frequency point corresponding to the maximum amplitude of the fitting spectrum in the harmonic frequency domain as the steady-state cavitation noise center frequency; determining the steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency; removing the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remaining is the transient cavitation noise component. The present invention can reduce the influence of the burrs of the cavitation noise spectrum and improve the quality of cavitation noise separation.

Description

Technical Field

[0001] The present invention relates to the technical field of advanced material preparation and processing, and in particular to a method and system for separating cavitation noise in an ultrasonic coagulation process. Background Art

[0002] Ultrasonic solidification refers to a material preparation method that uses high-power ultrasound to generate cavitation effect to control the solidification process of alloy melt. Among them, the strength of the cavitation effect is the main factor affecting the control effect. Therefore, accurate measurement of the cavitation effect in high-temperature melt is an important prerequisite for improving the control effect and obtaining high-performance materials.

[0003] Affected by the high temperature environment, the measurement of cavitation effect in metal melt is mainly based on cavitation noise method, which is mainly divided into two categories: time domain method and frequency domain method: (1) The time domain method uses the total sound pressure level and total sound intensity level of cavitation noise measured by the sensor as the characterization quantity of cavitation effect. However, the cavitation noise components are complex, including ultrasonic driving noise, steady-state cavitation noise, transient cavitation noise, etc. Among them, ultrasonic driving noise is irrelevant to cavitation effect. Therefore, the time domain method cannot accurately characterize the strength of cavitation effect; (2) The frequency domain method performs spectrum analysis on the cavitation noise measured by the sensor, separates different cavitation noise components through frequency domain characteristics, eliminates the influence of ultrasonic driving noise, and can accurately characterize the strength of cavitation effect. However, since cavitation is a strong nonlinear chaotic process, the cavitation noise spectrum components are complex, and there are many burrs and random frequency offset problems, which brings great difficulties to the selection of frequency domain features, the adaptive selection of separation parameters such as frequency band range, etc., which directly affects the accuracy of cavitation effect characterization. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for separating cavitation noise in an ultrasonic coagulation process, so as to reduce the influence of burrs on the cavitation noise spectrum and improve the quality of cavitation noise separation.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for separating cavitation noise during ultrasonic coagulation, comprising:

[0007] Acquire the original spectrum of the cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise;

[0008] The original spectrum is segmented, and the segmented original spectrum is fitted and smoothed based on an m-order polynomial to obtain a fitting spectrum;

[0009] Determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component;

[0010] Determining a harmonic frequency domain according to the driving frequency of the power ultrasonic transducer and the center frequency of the driving noise amount;

[0011] Determining, in the harmonic frequency domain, a frequency point corresponding to the maximum amplitude of the fitting spectrum as the center frequency of the steady-state cavitation noise;

[0012] Determine a steady-state cavitation noise component based on the original spectrum, the fitting spectrum, and the steady-state cavitation noise center frequency;

[0013] The driving noise component and the steady-state cavitation noise component are removed from the original spectrum, and the remaining component is the transient cavitation noise component.

[0014] Optionally, the obtaining of the original spectrum of the cavitation noise signal specifically includes:

[0015] Collect cavitation noise signals in alloy melt;

[0016] Performing N-point discrete Fourier transform on the cavitation noise signal to obtain the original frequency spectrum of the cavitation noise signal; N is a positive integer.

[0017] Optionally, the fitting and smoothing of the segmented original spectrum based on an m-order polynomial to obtain a fitting spectrum specifically includes:

[0018] The original spectrum after segmentation is fitted with an m-order polynomial to obtain an initial fitting spectrum;

[0019] The overlapping parts of two adjacent initial fitting spectra are spliced ​​and smoothed to obtain a fitting spectrum.

[0020] Optionally, determining a steady-state cavitation noise component based on the original spectrum, the fitting spectrum, and the steady-state cavitation noise center frequency specifically includes:

[0021] Performing spectrum subtraction on the original spectrum and the fitted spectrum, and taking an absolute value of the spectrum subtraction result;

[0022] Determine that the second extreme point on the left side of the center frequency of the steady-state cavitation noise after taking the absolute value is the starting frequency point of the line spectrum bandwidth;

[0023] Determine that the second extreme point on the right side of the center frequency of the steady-state cavitation noise after taking the absolute value is the end frequency point of the line spectrum bandwidth;

[0024] The line spectrum bandwidth is determined according to the starting frequency point of the line spectrum bandwidth and the ending frequency point of the line spectrum bandwidth; the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is a steady-state cavitation noise component.

[0025] The present invention also provides a cavitation noise separation system in an ultrasonic coagulation process, comprising:

[0026] The original spectrum acquisition module is used to acquire the original spectrum of the cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise;

[0027] A fitting spectrum acquisition module is used to segment the original spectrum, and perform fitting and smoothing processing on the segmented original spectrum based on an m-order polynomial to obtain a fitting spectrum;

[0028] A driving noise component determination module is used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component;

[0029] A harmonic frequency domain determination module, used to determine the harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise amount;

[0030] A steady-state cavitation noise center frequency determination module, used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum in the harmonic frequency domain as the steady-state cavitation noise center frequency;

[0031] A steady-state cavitation noise component determination module, used to determine the steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency;

[0032] The transient cavitation noise component determination module is used to remove the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remainder is the transient cavitation noise component.

[0033] Optionally, the original spectrum acquisition module specifically includes:

[0034] A collection unit, used for collecting cavitation noise signals in the alloy melt;

[0035] The discrete Fourier transform unit is used to perform N-point discrete Fourier transform on the cavitation noise signal to obtain the original frequency spectrum of the cavitation noise signal; N is a positive integer.

[0036] Optionally, the fitting spectrum acquisition module specifically includes:

[0037] A fitting unit is used to fit the original frequency spectrum after segmentation using an m-order polynomial to obtain an initial fitting spectrum;

[0038] The splicing and smoothing processing unit is used to splice and smooth the overlapping parts of two adjacent sections of the initial fitting spectrum to obtain a fitting spectrum.

[0039] Optionally, the steady-state cavitation noise component determination module specifically includes:

[0040] A spectrum subtraction unit, used for performing spectrum subtraction on the original spectrum and the fitted spectrum, and taking an absolute value of the spectrum subtraction result;

[0041] A line spectrum bandwidth starting frequency point determination unit is used to determine the second extreme point on the left side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth starting frequency point;

[0042] A line spectrum bandwidth end frequency point determination unit, used to determine the second extreme point on the right side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth end frequency point;

[0043] The steady-state cavitation noise component determination unit is used to determine the line spectrum bandwidth according to the starting frequency point of the line spectrum bandwidth and the ending frequency point of the line spectrum bandwidth; the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is the steady-state cavitation noise component.

[0044] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0045] The present invention provides a method for separating cavitation noise in an ultrasonic coagulation process, comprising: obtaining an original spectrum of a cavitation noise signal; segmenting the original spectrum, and fitting and smoothing the segmented original spectrum based on an m-order polynomial to obtain a fitting spectrum; determining a frequency point corresponding to a maximum amplitude of the fitting spectrum within a 1kHz neighborhood of a set power ultrasonic transducer driving frequency as a driving noise center frequency; a spectrum of the fitting spectrum corresponding to the driving noise center frequency is a driving noise component; determining a harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise; determining a frequency point corresponding to a maximum amplitude of the fitting spectrum within the harmonic frequency domain as a steady-state cavitation noise center frequency; determining a steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency; removing the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remainder is a transient cavitation noise component. The present invention obtains a smooth fitting spectrum based on a spectrum segmentation fitting and smoothing method of an m-order polynomial, suppresses the interference caused by spectrum burrs, and calculates the center frequency and occupied frequency band of each line spectrum through the deburred fitting spectrum, thereby achieving accurate separation of each component of cavitation noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 It is a flow chart of a method for separating cavitation noise during ultrasonic coagulation according to an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of segmenting the original spectrum according to an embodiment of the present invention;

[0049] Figure 3 The spectrum subtraction result of the embodiment of the present invention is At the center frequency f of the lth harmonic l Schematic diagram of the results on the left and right sides;

[0050] Figure 4 is the absolute value of the spectrum subtraction result of the embodiment of the present invention In f l Schematic diagram of nearby results;

[0051] Figure 5 Schematic diagram of determining line spectrum bandwidth according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The purpose of the present invention is to provide a method and system for separating cavitation noise in an ultrasonic coagulation process, so as to reduce the influence of burrs on the cavitation noise spectrum and improve the quality of cavitation noise separation.

[0054] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] like Figure 1 As shown, the method for separating cavitation noise during ultrasonic coagulation provided by the present invention comprises the following steps:

[0056] Step 101: obtaining an original spectrum of a cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise.

[0057] The cavitation noise signal in the alloy melt is collected by acquisition cards, high-temperature acoustic field sensors and other equipment, and a 65536-point discrete Fourier transform is performed on it to obtain the original spectrum S of the cavitation noise signal.

[0058] Step 102: segment the original spectrum, and perform fitting and smoothing processing on the segmented original spectrum based on an m-th order polynomial to obtain a fitting spectrum.

[0059] Divide S into K segments, each segment has P points, and the number of overlapping points between adjacent segments is P / 4; use an m-order polynomial to fit each segment to minimize the sum of squared residuals to obtain a segmented fitting spectrum; perform median filtering on the fitting spectrum at the overlapping points of adjacent segments to finally obtain a smooth fitting spectrum S p . The present invention obtains a smooth fitting spectrum through segmented fitting, median filtering, overlapping splicing and other methods. Compared with the traditional method, it reduces the amount of calculation, balances the overfitting and underfitting phenomena, suppresses the interference caused by spectrum burrs, retains the characteristics of the continuous spectrum part, and can significantly improve the separation effect of transient cavitation noise in cavitation noise. Through a large amount of measured data analysis and verification, the optimal algorithm parameter values ​​suitable for the ultrasonic treatment process are N=65536, K=1365, P=32, and m=3.

[0060] As a specific embodiment, the spectrum S is segmented into 1365 segments, each segment has 32 points, and the number of overlapping points between adjacent segments is 8. Figure 2 shown.

[0061] After the segmentation is completed, a third-order polynomial is used to fit each segment. The fitting polynomial is as follows:

[0062] S P (f i )=θ 0 +θ 1 f i +θ 2 f i 2 +θ 3 f i 3

[0063] Where S P is the fitted spectrum, f i m is the frequency f i mth power, θ 0 ,θ 1 ,…,θ m are polynomial coefficients. Apply the least squares algorithm, that is, find a set of θ 0 ,θ 1 ,…,θ mMake the residual sum of squares of the fitting function as minimum, that is By solving the equation, we can get the coefficients θ of the third-order fitting polynomial 0 ,θ 1 ,θ 3 ; Thus, the segmented fitting of the spectrum can be realized.

[0064] The overlapping parts of two adjacent segments of the fitting spectrum are averaged first to complete the front and back splicing of the segmented fitting spectrum. The algorithm is as follows:

[0065]

[0066] In the formula After the splicing is completed, the overlapping segments are further smoothed using the following algorithm to finally obtain the deburred fitting spectrum S P .

[0067] d=(S P (f i+2 )-S P (f i-3 ) / 5)

[0068] S P (f i-2 )=S P (f i-3 )+d

[0069] S P (f i-1 )=S P (f i-3 )+2d

[0070] S P (f i )=S P (f i-3 )+3d

[0071] S P (f i+1 )=S P (f i-3 )+4d

[0072] Where d represents the smoothing correction value.

[0073] Step 103: Determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1 kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component.

[0074] After obtaining the fitting spectrum S p Based on the set power ultrasonic transducer driving frequency f 0Find the frequency point f corresponding to the maximum amplitude in the 1kHz neighborhood of D , taking it as the real driving frequency, i.e., the driving noise center frequency, the spectrum corresponding to this frequency is the driving noise component of the cavitation noise, and its frequency offset is Δf = f D -f 0 .

[0075] Step 104: Determine a harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise amount.

[0076] According to the relationship between the line spectrum harmonic frequency and the driving frequency, a PFA consisting of L harmonic frequency domains is established, and the lth harmonic frequency domain is written as PFA l .

[0077] PFA = {[0.5 × j × (f D -Δf),0.5×j×(f D +Δf)]}

[0078] ={[l×(f D -Δf),l×(f D +Δf)]}

[0079] j=1…J∩j≠2

[0080] Step 105: determining the frequency point corresponding to the maximum amplitude of the fitting spectrum in the harmonic frequency domain as the center frequency of the steady-state cavitation noise.

[0081] In the above formula, in view of the wide bandwidth of cavitation noise and the limited spectral resolution of discrete Fourier transform, in order to avoid omission, the harmonic frequency domain is set to -Δf~Δf. The frequency point corresponding to the maximum amplitude in each harmonic frequency domain is recorded as f l , which is the center frequency of the lth harmonic. All f l The set of is the line spectrum frequency points of the cavitation noise, and the corresponding spectrum is the steady-state cavitation component in the cavitation noise.

[0082] The present invention adopts the method of measuring the driving frequency to obtain the real value f of the current cavitation noise driving frequency D And the corresponding frequency deviation Δf, then based on f D , Δf and harmonic relationship to obtain all harmonic center frequencies. Compared with the traditional method, the present invention fully considers the influence of random frequency deviation of power ultrasonic transducer, the center frequency search of the first harmonic is more accurate, and the separation quality of driving noise component and steady-state cavitation component in cavitation noise is improved.

[0083] Step 106: Determine a steady-state cavitation noise component based on the original spectrum, the fitting spectrum, and the steady-state cavitation noise center frequency.

[0084] For the spectrum S and its fitting spectrum S p Do spectral subtraction and take the absolute value of the result as Then at the center frequency f of the lth harmonic l Search on the left and right sides of The difference between the two is the bandwidth of the lth harmonic, such as Figure 5 shown.

[0085] Specifically, for the spectrum S and its fitting spectrum S p Do spectral subtraction, that is At the center frequency f of the lth harmonic (the driving frequency is the fundamental frequency of the harmonic, that is, when l=2, the bandwidth calculation method is the same) l The results on the left and right sides are as follows Figure 3 shown.

[0086] Spectral subtraction results Take the absolute value, then In f l Nearby results such as Figure 4 shown. At the lth harmonic center frequency f l The second extreme point on the left is determined as the starting frequency point of the line spectrum bandwidth f L_begin_j ; At the lth harmonic center frequency f l The second extreme point on the right is determined as the end frequency of the line spectrum bandwidth f L_end_j . Frequency band [f L_begin_j ,f L_end_j ] is the peak value f of the line spectrum peak_j Corresponding line spectrum bandwidth; traversing all harmonic peak frequencies, using the above method to obtain the bandwidth occupied by all l-th harmonics, the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is the steady-state cavitation noise component.

[0087] Step 107: removing the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remaining component is the transient cavitation noise component.

[0088] When power ultrasound is applied to the melt, the cavitation noise generated consists of the following three parts: driving noise, steady-state cavitation noise and transient cavitation noise. The driving noise is represented by a frequency spectrum with a center frequency of f D The line spectrum of steady-state cavitation noise is usually considered to be unrelated to cavitation. The spectrum of steady-state cavitation noise is characterized by a central frequency of f l The lth harmonic spectrum corresponds to the periodic vibration of the cavitation bubble; the transient cavitation noise appears as the remaining continuous spectrum on the spectrum, corresponding to the collapse of the cavitation bubble.

[0089] Using the fitted spectrum S pThe center frequency f of the driving noise and transient cavitation noise is obtained D 、f l And its corresponding bandwidth, the corresponding signal spectrum can be separated based on the above information on the original spectrum S; the remaining continuous spectrum part is the transient cavitation noise component. So far, the separation of cavitation noise has been completed.

[0090] The present invention also provides a cavitation noise separation system in an ultrasonic coagulation process, comprising:

[0091] The original spectrum acquisition module is used to acquire the original spectrum of the cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise;

[0092] A fitting spectrum acquisition module is used to segment the original spectrum, and perform fitting and smoothing processing on the segmented original spectrum based on an m-order polynomial to obtain a fitting spectrum;

[0093] A driving noise component determination module is used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component;

[0094] A harmonic frequency domain determination module, used to determine the harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise amount;

[0095] A steady-state cavitation noise center frequency determination module, used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum in the harmonic frequency domain as the steady-state cavitation noise center frequency;

[0096] A steady-state cavitation noise component determination module, used to determine the steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency;

[0097] The transient cavitation noise component determination module is used to remove the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remainder is the transient cavitation noise component.

[0098] The original spectrum acquisition module specifically includes:

[0099] A collection unit, used for collecting cavitation noise signals in the alloy melt;

[0100] The discrete Fourier transform unit is used to perform N-point discrete Fourier transform on the cavitation noise signal to obtain the original frequency spectrum of the cavitation noise signal; N is a positive integer.

[0101] Wherein, the fitting spectrum acquisition module specifically includes:

[0102] A fitting unit is used to fit the original frequency spectrum after segmentation using an m-order polynomial to obtain an initial fitting spectrum;

[0103] A splicing and smoothing processing unit is used to splice and smooth the overlapping parts of two adjacent segments of the initial fitting spectrum to obtain a fitting spectrum

[0104] Wherein, the steady-state cavitation noise component determination module specifically includes:

[0105] A spectrum subtraction unit, used for performing spectrum subtraction on the original spectrum and the fitted spectrum, and taking an absolute value of the spectrum subtraction result;

[0106] A line spectrum bandwidth starting frequency point determination unit is used to determine the second extreme point on the left side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth starting frequency point;

[0107] A line spectrum bandwidth end frequency point determination unit, used to determine the second extreme point on the right side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth end frequency point;

[0108] The steady-state cavitation noise component determination unit is used to determine the line spectrum bandwidth according to the starting frequency point of the line spectrum bandwidth and the ending frequency point of the line spectrum bandwidth; the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is the steady-state cavitation noise component.

[0109] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0110] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for separating cavitation noise during ultrasonic coagulation, characterized in that: include: Acquire the original spectrum of the cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise; The original spectrum is segmented, and the segmented original spectrum is fitted and smoothed based on an m-order polynomial to obtain a fitting spectrum; Determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component; Determining a harmonic frequency domain according to the driving frequency of the power ultrasonic transducer and the center frequency of the driving noise amount; Determining, in the harmonic frequency domain, a frequency point corresponding to the maximum amplitude of the fitting spectrum as the center frequency of the steady-state cavitation noise; Determine a steady-state cavitation noise component based on the original spectrum, the fitting spectrum, and the steady-state cavitation noise center frequency; The driving noise component and the steady-state cavitation noise component are removed from the original spectrum, and the remaining component is the transient cavitation noise component.

2. The method for separating cavitation noise during ultrasonic coagulation according to claim 1, characterized in that: The obtaining of the original spectrum of the cavitation noise signal specifically includes: Collect cavitation noise signals in alloy melt; Performing N-point discrete Fourier transform on the cavitation noise signal to obtain the original frequency spectrum of the cavitation noise signal; N is a positive integer.

3. The method for separating cavitation noise during ultrasonic coagulation according to claim 1, characterized in that: The fitting and smoothing of the segmented original spectrum based on the m-order polynomial to obtain the fitting spectrum specifically includes: The original spectrum after segmentation is fitted with an m-order polynomial to obtain an initial fitting spectrum; The overlapping parts of two adjacent initial fitting spectra are spliced ​​and smoothed to obtain a fitting spectrum.

4. The method for separating cavitation noise during ultrasonic coagulation according to claim 1, characterized in that: The determining of the steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency specifically includes: Performing spectrum subtraction on the original spectrum and the fitted spectrum, and taking an absolute value of the spectrum subtraction result; Determine that the second extreme point on the left side of the center frequency of the steady-state cavitation noise after taking the absolute value is the starting frequency point of the line spectrum bandwidth; Determine that the second extreme point on the right side of the center frequency of the steady-state cavitation noise after taking the absolute value is the end frequency point of the line spectrum bandwidth; The line spectrum bandwidth is determined according to the starting frequency point of the line spectrum bandwidth and the ending frequency point of the line spectrum bandwidth; the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is a steady-state cavitation noise component.

5. A cavitation noise separation system during ultrasonic coagulation, characterized in that: include: The original spectrum acquisition module is used to acquire the original spectrum of the cavitation noise signal; the cavitation noise includes driving noise, steady-state cavitation noise and transient cavitation noise; A fitting spectrum acquisition module is used to segment the original spectrum, and perform fitting and smoothing processing on the segmented original spectrum based on an m-order polynomial to obtain a fitting spectrum; A driving noise component determination module is used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum within the 1kHz neighborhood of the set power ultrasonic transducer driving frequency as the driving noise center frequency; the frequency spectrum of the fitting spectrum corresponding to the driving noise center frequency is the driving noise component; A harmonic frequency domain determination module, used to determine the harmonic frequency domain according to the power ultrasonic transducer driving frequency and the center frequency of the driving noise amount; A steady-state cavitation noise center frequency determination module, used to determine the frequency point corresponding to the maximum amplitude of the fitting spectrum in the harmonic frequency domain as the steady-state cavitation noise center frequency; A steady-state cavitation noise component determination module, used to determine the steady-state cavitation noise component based on the original spectrum, the fitting spectrum and the steady-state cavitation noise center frequency; The transient cavitation noise component determination module is used to remove the driving noise component and the steady-state cavitation noise component from the original spectrum, and the remainder is the transient cavitation noise component.

6. The cavitation noise separation system in ultrasonic coagulation process according to claim 5, characterized in that: The original spectrum acquisition module specifically includes: A collection unit, used for collecting cavitation noise signals in the alloy melt; The discrete Fourier transform unit is used to perform N-point discrete Fourier transform on the cavitation noise signal to obtain the original frequency spectrum of the cavitation noise signal; N is a positive integer.

7. The cavitation noise separation system during ultrasonic coagulation according to claim 5, characterized in that: The fitting spectrum acquisition module specifically includes: A fitting unit is used to fit the original frequency spectrum after segmentation using an m-order polynomial to obtain an initial fitting spectrum; The splicing and smoothing processing unit is used to splice and smooth the overlapping parts of two adjacent sections of the initial fitting spectrum to obtain a fitting spectrum.

8. The cavitation noise separation system in ultrasonic coagulation process according to claim 5, characterized in that: The steady-state cavitation noise component determination module specifically includes: A spectrum subtraction unit, used for performing spectrum subtraction on the original spectrum and the fitted spectrum, and taking an absolute value of the spectrum subtraction result; A line spectrum bandwidth starting frequency point determination unit, used to determine the second extreme point on the left side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth starting frequency point; A line spectrum bandwidth end frequency point determination unit, used to determine the second extreme point on the right side of the center frequency of the steady-state cavitation noise after taking the absolute value as the line spectrum bandwidth end frequency point; The steady-state cavitation noise component determination unit is used to determine the line spectrum bandwidth according to the starting frequency point of the line spectrum bandwidth and the ending frequency point of the line spectrum bandwidth; the frequency spectrum of the fitting spectrum corresponding to the line spectrum bandwidth is the steady-state cavitation noise component.

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