A method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics
By collecting and analyzing local acoustic signals from the ship, generating pulse peak signals and cloud maps, the problem of accuracy in judging the local cavitation state of the ship is solved, and effective judgment of cavitation initiation and development under various environmental conditions is realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA SHIP SCIENTIFIC RESEARCH CENTER
- Filing Date
- 2024-01-22
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies struggle to accurately determine local cavitation conditions during actual ship navigation, particularly the initiation and development of cavitation in propellers and appendages. Traditional methods exhibit significant differences under various operating conditions, impacting the accuracy and effectiveness of cavitation assessment.
By collecting local acoustic signals from the ship, pulse peak signals are generated and filtered. Based on the amplitude and width of the pulse peak signals, a pulse number density distribution is generated. The cavitation state, including the cavitation initiation and development state, is determined by using the cloud map of the pulse signal combined with the number density distribution.
It improves the accuracy and effectiveness of cavitation initiation judgment, is applicable to various environmental conditions, provides accurate judgment of local cavitation state on actual ships, and solves the problem of difficulty in judging cavitation in critical state.
Smart Images
Figure CN117949169B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cavitation state determination, and in particular to a method for determining the local cavitation state of a ship based on the characteristics of acoustic signal pulses. Background Technology
[0002] Cavitation initiation is a crucial indicator of a ship's quiet navigation performance. Currently, cavitation initiation is primarily determined through two methods: visual observation and acoustic signal spectral characteristics. However, visual observation is generally only feasible under laboratory conditions, while actual ship navigation requires more complex equipment and supporting processes. Traditional acoustic signal spectral characteristics can only reflect the overall characteristics of the signal, and cavitation can only be confirmed when there are significant differences in the spectral results under different operating conditions. Furthermore, it often cannot provide definitive conclusions regarding the critical states of interest, greatly affecting the accuracy and effectiveness of cavitation initiation determination and making it impossible to accurately determine the local cavitation state of components such as the propeller and appendages on a real ship. Summary of the Invention
[0003] To address the aforementioned problems and technical requirements, the inventors have proposed a cavitation state discrimination method based on acoustic signal pulse characteristics. The technical solution of this invention is as follows:
[0004] A method for determining the local cavitation state of a ship based on the pulse characteristics of acoustic signals includes configuring a predetermined local area of the ship as the measurement object, collecting acoustic signals of the flow field where the measurement object is located within a predetermined time period, so as to obtain a result containing several original acoustic signals p after the acoustic signal acquisition. original The original acoustic signal group of (t);
[0005] Several pulse peak signals are generated based on the original acoustic signal group;
[0006] For any pulse peak signal, the pulse peak signal is filtered based on cavitation characteristics to obtain a filtered pulse peak signal that matches the filtering conditions. The filtering conditions for the pulse peak signal include the amplitude and width of the pulse peak signal.
[0007] Based on the above-mentioned filtering pulse peak signal, a filtering pulse peak signal group is generated, and based on the filtering pulse peak signal group, a pulse number density distribution corresponding to the filtering pulse peak signal group is generated.
[0008] Based on the selection of pulse peak signal groups and pulse number density distribution, a cloud map of the joint number density distribution of pulse signals is generated, and the cavitation state of the measured object is determined based on the cloud map.
[0009] The further technical solution is that the cavitation state of the measured object includes the cavitation initiation and the cavitation development state;
[0010] When cavitation occurs in the measured object, the cloud map includes several pulse ripples, and the shape of the pulse ripples in the cloud map corresponds to the development state of cavitation.
[0011] When determining the cavitation state of the measured object based on the cloud map, the cavitation initiation is determined based on the first appearance of the pulse ripple, and the cavitation development state is determined based on the morphology of the pulse ripple.
[0012] A further technical solution is that the method for generating several pulse peak signals based on the original acoustic signal group includes:
[0013] S1, for all original sound signals p in the original sound signal group original (t) is high-pass filtered to obtain several high-frequency characteristic signals p highpass (t);
[0014] S2, for all high-frequency characteristic signals p highpass (t) takes the absolute value to generate several positive phase high-frequency characteristic signals abs[p highpass (t)];
[0015] S3, for all positive phase high-frequency characteristic signals abs[p highpass (t)] is used to extract the pulse peak signal to generate several pulse peak signals (P) i ,ΔT i ).
[0016] A further technical solution is that the high-pass filter cutoff frequency F in step S1 is... highcr The value range is 1kHz-5kHz.
[0017] A further technical solution is that any selected pulse peak signal in the selected pulse peak signal group satisfies:
[0018]
[0019] Among them, P i To filter the amplitude of the pulse peak signal, ΔT i To filter the width of the pulse peak signal, P crlow To filter the lower limit of the amplitude threshold for pulse peak signals, T crlow To filter the lower threshold of the pulse peak signal width, T crhigh The upper limit of the width threshold is used to filter the peak pulse signal;
[0020] The lower limit of the width threshold for the filtered pulse peak signal The upper limit of the width threshold for the filtered pulse peak signal Among them, F s The original sound signal p original The sampling frequency of (t).
[0021] A further technical solution involves obtaining the lower limit P of the amplitude threshold for selecting the peak signal of the pulse. crlow At that time, for all original sound signals p original (t) is low-pass filtered to obtain several low-frequency characteristic signals p. lowpass (t), where,
[0022] The cutoff frequency F of the low-pass filter lowcr With the cutoff frequency F of the high-pass filter highcr equal;
[0023] All low-frequency characteristic signals p lowpass (t) average amplitude P is the lower limit of the amplitude threshold for filtering pulse peak signals. crlow .
[0024] A further technical solution is that the sampling frequency F of the original acoustic signal group is... s ≥200kHz.
[0025] A further technical solution is that, when determining the cavitation state of the measured object, it also includes determining the cavitation initiation condition parameters of the measured object at the start of cavitation, wherein,
[0026] While determining the cavitation state of the measured object, the corresponding operating parameters of the measured object are recorded in real time. The average value of the corresponding operating parameters at the start of cavitation and the corresponding operating parameters at the moment before the start of cavitation is calculated, and the average value is used as the cavitation start operating parameter.
[0027] A further technical solution is that the object being measured is a propeller or a ship appendage, wherein,
[0028] When the object being measured is a propeller, the operating parameter is the propeller's rotational speed n;
[0029] When the object of measurement is a ship appendage, the operating parameter is the ship's speed v.
[0030] A further technical solution involves acquiring acoustic signals in the form of time-domain signals using a sensor within a preset time period. The sensor's response frequency is ≥100kHz, and the sensor includes a hydrophone. The beneficial technical effects of this invention are:
[0031] This invention is based on a set of raw acoustic signals acquired in the time domain. Several pulse peak signals are generated from this raw acoustic signal set, and the amplitude and width of the pulse peak signals are simultaneously filtered to obtain a pulse number density distribution that matches the cavitation characteristics. The cavitation state is then determined using a contour map of the pulse signals combined with the number density distribution. This invention is applicable to the determination of acoustic signals indicating the onset of cavitation under various environmental conditions, solving the problem of difficulty in effectively determining the existence of cavitation in critical states. It improves the accuracy and effectiveness of cavitation initiation determination and can provide technical support for determining the local cavitation state of ship propellers, appendages, etc. Attached Figure Description
[0032] Figure 1 This is a flowchart of one embodiment provided by the present invention.
[0033] Figure 2 This is a waveform diagram of the original acoustic signal group according to an embodiment of the present invention.
[0034] Figure 3 This is a high-frequency characteristic signal waveform diagram of an embodiment of the present invention.
[0035] Figure 4 This is a waveform diagram of the positive phase high-frequency characteristic signal of an embodiment provided by the present invention.
[0036] Figure 5 This is a pulse signal joint quantity density distribution cloud map provided by an embodiment of the present invention.
[0037] Figure 6 This is a combined number density distribution cloud map of pulse signals when no cavitation occurs, provided by one embodiment of the present invention.
[0038] Figure 7 This is a cloud map showing the joint number density distribution of pulse signals when the signal is in a critical cavitation state, according to one embodiment of the present invention.
[0039] Figure 8 This is a combined number density distribution cloud map of pulse signals in a state of relatively sufficient cavitation, provided by one embodiment of the present invention. Detailed Implementation
[0040] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.
[0041] During ship navigation, the mechanical vibrations generated by the ship's propeller, appendages, etc., will cause changes in the internal pressure of the liquid. When the pressure decreases, structural fractures will occur inside the liquid or at the liquid-solid interface, thus forming cavitation. The process of the formation, development, and collapse of the cavity is called cavitation.
[0042] Actual cavitation exists in an unsteady form, meaning its state changes over time. Its occurrence is inevitably accompanied by cavitation development and collapse processes, generating corresponding high-frequency, high-amplitude signals. This invention, based on the measurement of acoustic signals, proposes a method for determining the local cavitation state of a ship based on the pulse characteristics of acoustic signals. This method involves configuring a predetermined local area of the ship as the measurement object, collecting acoustic signals from the flow field of the measurement object within a predetermined time period, and obtaining a result containing several original acoustic signals p after the acoustic signal acquisition. original The original acoustic signal group of (t);
[0043] Several pulse peak signals are generated based on the original acoustic signal group;
[0044] For any pulse peak signal, the pulse peak signal is filtered based on cavitation characteristics to obtain a filtered pulse peak signal that matches the filtering conditions. The filtering conditions for the pulse peak signal include the amplitude and width of the pulse peak signal.
[0045] Based on the above-mentioned filtering pulse peak signal, a filtering pulse peak signal group is generated, and based on the filtering pulse peak signal group, a pulse number density distribution corresponding to the filtering pulse peak signal group is generated.
[0046] Based on the selection of pulse peak signal groups and pulse number density distribution, a cloud map of the joint number density distribution of pulse signals is generated, and the cavitation state of the measured object is determined based on the cloud map.
[0047] In practical implementation, the ship's propeller or appendages can be used as the measurement object for judging the local cavitation state. The ship appendages are the appendages below the waterline of the ship, and the flow field is the fluid region near the measurement object. Acoustic signals from the flow field where the measurement object is located are collected within a preset time to obtain several original acoustic signals p within the flow field. original The original acoustic signal group of (t). Figure 2 The image shows the waveform of the original acoustic signal group in one embodiment of the present invention. Figure 2 The horizontal axis represents the corresponding acquisition time (s) of the original sound signal, and the vertical axis represents the amplitude (Pa) of the original sound signal. The original sound signal group contains pulsation information of all frequency bands, that is, the original sound signal group is a combination signal including low frequency signals and high frequency signals.
[0048] The original acoustic signal p original (t) represents the time-domain signal, and within the time domain, it represents all the original sound signals p in the original sound signal group. original (t) Peak extraction is performed to generate several pulse peak signals, that is, to generate several discrete signal data with amplitude and width. The extraction of pulse peak signals can be carried out using common methods in this technical field, which will not be elaborated here.
[0049] Based on the principle of cavitation, compared to the non-cavitation signal, i.e., the original acoustic signal p corresponding to the absence of cavitation,... original (t), the main characteristic of the cavitation signal is that the high-frequency part of the acoustic signal is significantly increased, and the high-frequency part is the higher frequency component of the original acoustic signal. The cavitation signal is the original acoustic signal p corresponding to the occurrence of cavitation. original (t). The cavitation signal described here is characterized by cavitation properties. Based on these cavitation properties, the amplitude and width of the pulse peak signal are filtered to obtain a filtered pulse peak signal that matches the filtering conditions, i.e., the cavitation properties. The filtering conditions are described below.
[0050] The pulse number density distribution corresponding to the selected pulse peak signal group, that is, the number of selected pulse peak signals with corresponding amplitude and width per unit time, can be expressed as follows: Where P i To filter the amplitude of the pulse peak signal, ΔT i To filter the width of the pulse peak signal, a contour map of the pulse signal's joint quantity density distribution is generated by combining the amplitude and width of the pulse peak signal with the pulse quantity density distribution. In one embodiment of the invention, the generated contour map of the pulse signal's joint quantity density distribution is as follows: Figure 5 As shown, the horizontal axis represents the amplitude P of the selected pulse peak signal. i The vertical axis represents the width ΔT of the filtered pulse peak signal. i The color of the cloud map represents the number of filtered pulse peak signals with corresponding amplitude and width per unit time. Optionally, the physical values corresponding to the horizontal and vertical axes of the cloud map can be interchanged. In specific implementation, the specific method of drawing the cloud map can be selected according to actual needs. The specific method for determining the cavitation state of the measured object based on the cloud map can be found in the following description.
[0051] This invention analyzes and processes the original acoustic signal group according to the above method to draw a cloud map of the combined number density distribution of pulse signals. Based on the cloud map, the cavitation state of the measured object can be quickly and intuitively determined, thereby accurately judging the onset of cavitation and improving the accuracy and effectiveness of cavitation onset judgment. Furthermore, since the acoustic signal is not affected by environmental visual conditions, this invention is applicable to judging the onset of cavitation in various environmental conditions, exhibiting strong applicability and providing effective technical support for judging the local cavitation state of ships.
[0052] Furthermore, the acoustic signal is acquired using a sensor in the form of a time-domain signal. To effectively acquire the cavitation signal, the response frequency F of the sensor is... a ≥100kHz, sampling frequency F s≥200kHz. Optionally, the sensor can be a hydrophone. In specific implementations, the specific form of the sensor can be selected according to actual needs, specifically to meet the requirements of sound signal acquisition.
[0053] Furthermore, the cavitation state of the measured object includes both the cavitation initiation and the cavitation development state;
[0054] When cavitation occurs in the measured object, the cloud map includes several pulse ripples, and the shape of the pulse ripples in the cloud map corresponds to the development state of cavitation.
[0055] When determining the cavitation state of the measured object based on the cloud map, the cavitation initiation is determined based on the first appearance of the pulse ripple, and the cavitation development state is determined based on the morphology of the pulse ripple.
[0056] Specifically, the cavitation initiation refers to the phenomenon when the local pressure within the liquid decreases to a critical value, and cavitation begins to occur. The development state of cavitation corresponds to the aforementioned process of cavity formation, development, and collapse. The state where cavitation just begins to occur, i.e., when cavitation just begins to form, is defined as the critical state, and the state where a large number of cavities have formed is defined as the state of relatively sufficient cavitation. The presence or absence of pulse ripples in the cloud image indicates whether cavitation has occurred. When pulse ripples are present in the cloud image, it indicates that cavitation has occurred in the measured object; when pulse ripples are absent, it indicates that cavitation has not occurred in the measured object. Therefore, the initiation of cavitation can be determined by the first appearance of pulse ripples in the cloud image. The pulse ripples are wavy areas in the cloud image that are different in color from the background color, where the background color is the color corresponding to when the number of filtered pulse peak signals in the cloud image is 0. In specific implementation, the presence or absence of pulse ripples in the cloud image can be determined by color recognition. When color recognition confirms that the cloud image contains wavy areas with a color different from the background color, it is considered that pulse ripples exist. In specific implementation, color recognition can be performed using methods such as OpenCV color recognition.
[0057] The number and display area of ripples in the cloud map characterize the development state of cavitation. When ripples first appear in small quantities and their display area in the cloud map is small, it indicates the critical state of cavitation. As ripples gradually appear in large quantities and their display area in the cloud map gradually increases, it indicates that cavitation has gradually developed from the critical state to a more fully developed state. Furthermore, the color composition of the pulse ripples can also qualitatively determine the development state of cavitation. When the number of selected pulse peak signals in the cloud map is high, the corresponding color has a larger display area in the pulse ripples, indicating more fully developed cavitation. Since the morphology of the pulse ripples is related to the development process of cavitation, the appearance of pulse ripples can be used to determine whether cavitation has occurred at the critical state, solving the problem of difficulty in effectively judging the existence of cavitation at the critical state. This improves the accuracy and effectiveness of cavitation initiation judgment and provides accurate and effective support for judging the initiation of cavitation.
[0058] The following is combined Figures 6-8 The method of determining the cavitation state of a measurement object using cloud maps according to the present invention will be described in detail below. Figure 6 This is a contour map of the joint number density distribution of pulse signals when the measured object does not undergo cavitation, according to one embodiment of the present invention. Figure 6 As shown, no pulse ripples appear in the cloud image, meaning that only the background color is displayed in the cloud image, which indicates that the measured object has not undergone cavitation. Figure 7 This is a contour map of the joint number density distribution of pulse signals when the measured object begins to cavitation and is in a critical state, according to one embodiment of the present invention. Figure 7 As shown, a small number of pulse ripples appear for the first time in the cloud map, and the display area in the cloud map is small. That is, a ripple-shaped area with a different color from the background color appears in the cloud map, and the area of the ripple-shaped area is small. At this time, the measured object is cavitating and is in a critical state, which characterizes the cavitation initiation phenomenon of the measured object. Figure 8 In one embodiment of the present invention, a cloud map of the joint quantity density distribution of pulse signals corresponding to the state of relatively sufficient cavitation after a period of time following the initial cavitation of the measured object. For example... Figure 8 As shown, a large number of pulse ripples appear in the cloud map, and the display area in the cloud map is relatively large. At this time, the measured object is in a state of sufficient cavitation.
[0059] Furthermore, the method for generating several pulse peak signals based on the original acoustic signal group includes:
[0060] S1, for all original sound signals p in the original sound signal group original (t) is high-pass filtered to obtain several high-frequency characteristic signals p highpass (t), due to the high-frequency characteristics of the cavitation signal, therefore, all original acoustic signals p are first processed. original (t) performs high-pass filtering to filter out some non-cavitation signals that are unrelated to cavitation, where,
[0061] The cutoff frequency F of the high-pass filter highcr The value range is 1kHz-5kHz. In specific implementation, the cutoff frequency F of the high-pass filter is... highcr You can choose according to your actual needs. Figure 3 For all high-frequency characteristic signals p in one embodiment of the present invention highpass The corresponding waveform of (t), Figure 3 Meaning of horizontal and vertical axes Figure 2 The horizontal and vertical axes of the original acoustic signal group have the same meaning; please refer to the above explanation for details.
[0062] S2. To facilitate the extraction of pulse peak signals, all the above high-frequency characteristic signals p highpass (t) Take the absolute value, and the high-frequency characteristic signal p highpassThe negative phase signal in (t) is converted into a positive phase signal to generate several positive phase high-frequency characteristic signals abs[p]. highpass (t)]. Figure 4 In one embodiment of the present invention, the high-frequency characteristic signals abs[p] are related to all positive phase signals. highpass [(t)] corresponds to the waveform, Figure 4 The meanings of the horizontal and vertical axes are also related to Figure 2 The horizontal and vertical axes have the same meaning; please refer to the above explanation for details.
[0063] S3. Using the peak statistics method, all positive phase high-frequency characteristic signals abs[p] are analyzed. highpass (t)] is used to extract pulse peak signals to generate several pulse peak signals. In one embodiment of the present invention, to facilitate the generation of pulse number density distributions corresponding to the selected pulse peak signal groups... At this point, a peak number density distribution corresponding to all pulse peak signals is generated, and after generating the above-mentioned filtered pulse peak signal group, a pulse number density distribution is generated based on the peak number density distribution. The peak number density distribution is as follows It indicates that, among them, P all Let ΔT be the amplitude of the peak pulse signal. all This refers to the width of the pulse peak signal. The specific principle of the peak statistical method is consistent with existing technologies and will not be elaborated here. In specific implementation, the method for generating the pulse peak signal can be selected according to actual needs.
[0064] Furthermore, any selected pulse peak signal in the selected pulse peak signal group satisfies:
[0065]
[0066] Among them, P i To filter the amplitude of the pulse peak signal, ΔT i To filter the width of the pulse peak signal, P crl ow is the lower limit of the amplitude threshold for filtering pulse peak signals, T crl ow is the lower limit of the width threshold for filtering pulse peak signals, T crhigh The upper limit of the width threshold is used to filter the peak pulse signal;
[0067] The lower limit of the width threshold for the filtered pulse peak signal The upper limit of the width threshold for the filtered pulse peak signal Among them, F s The sampling frequency of the original acoustic signal group.
[0068] Specifically, according to the sampling theorem, when the sampling frequency of the original acoustic signal group is F... sWhen, the corresponding highest signal analysis frequency is The lower limit of the width threshold for filtering pulse peak signals can be obtained from the highest signal analysis frequency. Obtain the lower limit P of the amplitude threshold for filtering pulse peak signals. crlow At that time, for all original sound signals p original (t) is low-pass filtered to obtain several low-frequency characteristic signals p. lowpass (t), where,
[0069] The cutoff frequency F of the low-pass filter lowcr With the cutoff frequency F of the high-pass filter highcr equal;
[0070] All low-frequency characteristic signals p lowpass (t) average amplitude P is the lower limit of the amplitude threshold for filtering pulse peak signals. crlow Since the low-frequency signal mainly originates from the unsteady pulsation of the cavitation system and is mainly related to the volume pulsation of the cavitation system, while the signal generated by the collapse process is a local impact signal, the amplitude of which generally exceeds the amplitude of the low-frequency pulsation, the average value of the low-frequency pulsation amplitude is used as the screening threshold to remove the influence of the low-amplitude collapse signal.
[0071] Furthermore, as explained above, cavitation is related to the mechanical vibrations generated by the ship's propeller, appendages, etc., and the magnitude of these mechanical vibrations is related to the corresponding operating parameters of the propeller, appendages, etc. Therefore, after configuring the measurement object, determining the cavitation state of the measurement object also includes determining the initial cavitation operating parameters of the measurement object at the start of cavitation.
[0072] While determining the cavitation state of the measured object, the corresponding operating parameters of the measured object are recorded in real time. The average value of the corresponding operating parameters at the start of cavitation and the corresponding operating parameters at the moment before the start of cavitation is calculated, and the average value is used as the cavitation start operating parameter.
[0073] Specifically, cavitation begins when the first pulse ripple appears in the cloud image; therefore, the moment the first pulse ripple appears in the cloud image is taken as the cavitation initiation moment. Furthermore, when the object of measurement is a propeller, the operating parameter is the propeller speed n. When the object of measurement is a ship appendage, the operating parameter is the ship's speed v. Taking a propeller as an example, the process of determining the cavitation initiation operating parameter is explained in detail: when the propeller cavitation initiation is detected by identifying the cloud image, the propeller speed at this moment is recorded as n1. The propeller speed n2 at the moment before the cavitation initiation is obtained, and then the propeller cavitation initiation operating parameter n is determined. in It can be represented as:
[0074]
[0075] The above descriptions are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.
Claims
1. A method for determining the local cavitation state of a ship based on the pulse characteristics of acoustic signals, characterized in that, The ship is configured as a preset local part as a measurement object, and the sound signals of the flow field where the measurement object is located are collected within a preset time to obtain a group of original sound signals containing a plurality of original sound signals after the sound signal collection ; Several pulse peak signals are generated based on the original acoustic signal group; For any pulse peak signal, the pulse peak signal is filtered based on cavitation characteristics to obtain a filtered pulse peak signal that matches the filtering conditions. The filtering conditions for the pulse peak signal include the amplitude and width of the pulse peak signal. Based on the above-mentioned filtering pulse peak signal, a filtering pulse peak signal group is generated, and based on the filtering pulse peak signal group, a pulse number density distribution corresponding to the filtering pulse peak signal group is generated. Based on the selection of pulse peak signal groups and pulse number density distribution, a cloud map of the joint number density distribution of pulse signals is generated, and the cavitation state of the measured object is determined based on the cloud map. The method for generating several pulse peak signals based on the original acoustic signal group includes: S1, for all original sound signals in the original sound signal group High-pass filtering is performed to obtain several high-frequency characteristic signals. ; S2, for all high-frequency characteristic signals Take the absolute value to generate several positive phase high-frequency characteristic signals. ; S3, for all positive phase high-frequency characteristic signals Pulse peak signal extraction is performed to generate several pulse peak signals; Any selected pulse peak signal in the selected pulse peak signal group satisfies: in, To filter the amplitude of the pulse peak signal, To filter the width of the pulse peak signal, To filter the lower limit of the amplitude threshold for pulse peak signals, To filter the lower threshold of the pulse peak signal width, The upper limit of the width threshold for filtering pulse peak signals; The lower limit of the width threshold for the selected pulse peak signal The upper limit of the width threshold of the filtered pulse peak signal ,in, Original sound signal The sampling frequency; Obtain the lower limit of the amplitude threshold for filtering pulse peak signals. At that time, for all original sound signals Perform low-pass filtering to obtain several low-frequency characteristic signals. ,in, low-pass filter cutoff frequency With the cutoff frequency of the high-pass filter equal; All low-frequency characteristic signals Average amplitude As the lower limit of the amplitude threshold for filtering pulse peak signals .
2. The method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics according to claim 1, characterized in that, The cavitation state of the measured object includes the cavitation initiation and the cavitation development state. When cavitation occurs in the measured object, the cloud map includes several pulse ripples, and the shape of the pulse ripples in the cloud map corresponds to the development state of cavitation. When determining the cavitation state of the measured object based on the cloud map, the cavitation initiation is determined based on the first appearance of the pulse ripple, and the cavitation development state is determined based on the morphology of the pulse ripple.
3. The cavitation state discrimination method based on acoustic signal pulse characteristics according to claim 1, characterized in that, High-pass filter cutoff frequency in step S1 The value range is 1kHz-5kHz.
4. The method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics according to claim 1, characterized in that, The sampling frequency of the original acoustic signal group ≥200kHz.
5. The method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics according to claim 1, characterized in that, Determining the cavitation state of the measured object also includes determining the cavitation initiation parameters of the measured object at the start of cavitation, wherein... While determining the cavitation state of the measured object, the corresponding operating parameters of the measured object are recorded in real time. The average value of the corresponding operating parameters at the start of cavitation and the corresponding operating parameters at the moment before the start of cavitation is calculated, and the average value is used as the cavitation start operating parameter.
6. The method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics according to claim 5, characterized in that, The object of measurement is a propeller or ship appendage, wherein... When the object of measurement is a propeller, the operating parameter is the propeller speed. n ; When the object of measurement is a ship appendage, the operating parameter is the ship's speed. v .
7. The method for determining the local cavitation state of a ship based on acoustic signal pulse characteristics according to any one of claims 1-6, characterized in that, Within a preset time period, a sensor is used to collect sound signals in the form of a time-domain signal. The response frequency of the sensor is ≥100kHz, and the sensor includes a hydrophone.