Method and apparatus for monitoring cavitation of ship propellers based on acoustic signals

Abstract

A method and apparatus for monitoring cavitation of a ship propeller based on an acoustic signal are disclosed. The method for monitoring cavitation of a ship propeller may include the steps of: obtaining an acoustic signal from an acoustic sensor that measures acoustics generated from the ship propeller, or obtaining a vibration signal from a vibration sensor that measures vibrations generated from the ship propeller; obtaining a demon spectrum by performing invelop analysis on the acoustic signal or the vibration signal; detecting frequency components from the demon spectrum; and determining that cavitation is occurring in the propeller if the detected frequency components include 2SR (Shaft Rate), BR (Blade Rate), or 2BR.

Description

Technology Field

[0001] The present invention relates to a method and apparatus for monitoring cavitation in a ship propeller, and more specifically, to a method and apparatus for monitoring whether cavitation occurs in a ship propeller using an acoustic signal or a vibration signal. Background Technology

[0002] Cavitation noise in ship propellers occurs when the fluid velocity near the propeller increases and the pressure drops below a certain level.

[0003] When cavitation noise occurs, the level of underwater radiated noise rises sharply, which can become a fatal threat, particularly for vessels, as it increases the probability of detection.

[0004] Conventional cavitation monitoring methods involved placing external sensors at a certain distance from the hull using cables, and determining that cavitation had occurred if the sound pressure or vibration level measured by the placed external sensors exceeded a certain threshold value. However, conventional cavitation monitoring methods

[0005] There was a problem in that it could not be evaluated quantitatively because the presence of a sound pressure signal at a specific frequency was determined subjectively through the change in sound pressure magnitude according to speed and the envelop analysis of the sound pressure signal.

[0006] Therefore, a method is required to quantitatively determine the occurrence of cavitation using acoustic and vibration signals measured independently by sensors installed on board. The problem to be solved

[0007] The present invention provides a method and apparatus for determining whether cavitation occurs in a ship's propeller using an acoustic signal or a vibration signal, and providing information regarding whether cavitation has occurred to a user. means of solving the problem

[0008] A method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may include the steps of: obtaining an acoustic signal from an acoustic sensor that measures acoustics generated from the ship's propeller or obtaining a vibration signal from a vibration sensor that measures vibrations generated from the ship's propeller; obtaining a demon spectrum by performing invelop analysis on the acoustic signal or the vibration signal; detecting frequency components from the demon spectrum; and determining that cavitation is occurring in the propeller if the detected frequency components include 2SR (Shaft Rate), BR (Blade Rate), or 2BR.

[0009] A method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include: a step of determining whether a plurality of frequency components are simultaneously detected when SR is included in the detected frequency component; and a step of determining that cavitation occurs in the propeller when a plurality of frequency components are simultaneously detected.

[0010] A method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include a step of determining that cavitation does not occur in the propeller if at least one of 2SR, BR, and 2BR is not included in the detected frequency component, or if only the SR component is included.

[0011] The step of acquiring the demon spectrum of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may be to perform envelop analysis by applying a Hilbert transform to an acoustic signal or a vibration signal to extract an envelope time signal representing the envelope of the acoustic signal or vibration signal, and the step of detecting the frequency components may be to convert the envelope time signal into the frequency domain to extract an SR frequency component or a BR frequency component.

[0012] A method for monitoring cavitation of a ship propeller according to an embodiment of the present invention may include: a step of obtaining an acoustic signal from an acoustic sensor that measures acoustics generated from the ship propeller or obtaining a vibration signal from a vibration sensor that measures vibrations generated from the ship propeller; a step of obtaining a demon spectrum by performing invelop analysis on the acoustic signal or the vibration signal; a step of determining whether the kurtosis value of the acoustic signal or the vibration signal for the demon spectrum at a specific frequency exceeds a threshold kurtosis value; and a step of determining that cavitation is occurring in the propeller if the kurtosis value of the acoustic signal or the vibration signal exceeds a threshold kurtosis value.

[0013] A method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include a step of determining that cavitation does not occur in the propeller when the kurtosis value of the acoustic signal or vibration signal is below a threshold kurtosis value.

[0014] A method for monitoring cavitation of a ship propeller according to an embodiment of the present invention may include: a step of determining a minimum level of propeller noise by considering a marine environment and a sound pressure level detectable by sonar; a step of determining a sound pressure level of an acoustic signal measured using an acoustic sensor; a step of determining that cavitation does not occur when the sound pressure level of the acoustic signal is less than or equal to the minimum level; and a step of determining that cavitation occurs when the sound pressure level of the acoustic signal exceeds the minimum level.

[0015] A method for monitoring cavitation of a ship propeller according to an embodiment of the present invention further comprises the step of determining a maximum level of propeller noise by considering a state in which cavitation occurs in the propeller above a certain level; and the step of determining whether cavitation occurs may include the step of determining that cavitation occurs when the sound pressure level of the acoustic signal exceeds the maximum level; and the step of determining whether cavitation occurs by considering additional conditions when the sound pressure level of the acoustic signal is less than or equal to the maximum level.

[0016] The step of determining whether cavitation occurs by considering the additional conditions of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may include: a step of obtaining an acoustic signal from an acoustic sensor that measures acoustics generated from the ship propeller or a step of obtaining a vibration signal from a vibration sensor that measures vibrations generated from the propeller; a step of obtaining a demon spectrum by performing invelop analysis on the acoustic signal or the vibration signal; a step of detecting frequency components from the demon spectrum; and a step of determining that cavitation occurs in the propeller if 2SR, BR, or 2BR is included in the detected frequency components.

[0017] The step of determining whether cavitation occurs by considering the additional conditions of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include: a step of checking whether a plurality of frequency components are simultaneously detected when SR is included in the detected frequency component; and a step of determining that cavitation occurs in the propeller when a plurality of frequency components are simultaneously detected.

[0018] The step of determining whether cavitation occurs by considering the additional conditions of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include the step of determining that cavitation does not occur in the propeller if at least one of 2SR, BR, and 2BR is not included in the detected frequency component, or if only the SR component is included.

[0019] The step of determining whether cavitation occurs by considering the additional conditions of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may include: a step of obtaining an acoustic signal from an acoustic sensor that measures acoustics generated from the ship propeller or a step of obtaining a vibration signal from a vibration sensor that measures vibrations generated from the ship propeller; a step of obtaining a demon spectrum by performing invelop analysis on the acoustic signal or the vibration signal; a step of checking whether the kurtosis value of the acoustic signal or the vibration signal for the demon spectrum at a specific frequency exceeds a threshold kurtosis value; and a step of determining that cavitation occurs in the propeller if the kurtosis value of the acoustic signal or the vibration signal exceeds a threshold kurtosis value.

[0020] The step of determining whether cavitation occurs by considering the additional conditions of the method for monitoring cavitation of a ship propeller according to one embodiment of the present invention may further include the step of determining that cavitation does not occur in the propeller when the kurtosis value of the acoustic signal or vibration signal is below a threshold kurtosis value.

[0021] A cavitation monitoring device for a ship propeller according to one embodiment of the present invention may include: an acoustic sensor that measures sound generated from a ship propeller and outputs an acoustic signal; and a processor that determines a minimum level of propeller noise by considering the marine environment and a sound pressure level detectable by sonar, and determines that cavitation is occurring when the sound pressure level of the acoustic signal exceeds the minimum level, and determines that cavitation is not occurring when the sound pressure level of the acoustic signal is less than or equal to the minimum level.

[0022] The processor of the cavitation monitoring device for a ship propeller according to one embodiment of the present invention determines a maximum level of propeller noise by considering a state in which cavitation occurs in the propeller above a certain level, and determines that cavitation is occurring when the sound pressure level of the acoustic signal exceeds the maximum level, and when the sound pressure level of the acoustic signal is less than or equal to the maximum level, determines whether cavitation is occurring by considering additional conditions.

[0023] The processor of the cavitation monitoring device for a ship propeller according to one embodiment of the present invention obtains a demon spectrum by performing invert analysis on an acoustic signal obtained from an acoustic sensor that measures acoustics generated from the ship propeller, or a vibration signal obtained from a vibration sensor that measures vibrations generated from the propeller, detects frequency components from the demon spectrum, and if the detected frequency components include 2SR, BR, or 2BR, it can determine that cavitation is occurring in the propeller.

[0024] The processor of the cavitation monitoring device for a ship propeller according to one embodiment of the present invention obtains a demon spectrum by performing invelop analysis on an acoustic signal obtained from an acoustic sensor that measures acoustics generated from the ship propeller, or a vibration signal obtained from a vibration sensor that measures vibrations generated from the propeller, and checks whether the kurtosis value of the acoustic signal or vibration signal for the demon spectrum at a specific frequency exceeds a threshold kurtosis value, and if the kurtosis value of the acoustic signal or vibration signal exceeds the threshold kurtosis value, it can determine that cavitation is occurring in the propeller. Effects of the invention

[0025] According to one embodiment of the present invention, an acoustic signal or a vibration signal can be used to determine whether cavitation occurs in a ship's propeller, and information regarding whether cavitation has occurred can be provided to a user. Brief explanation of the drawing

[0026] FIG. 1 is a drawing illustrating a cavitation monitoring device for a ship propeller according to an embodiment of the present invention. FIG. 2 is an example of a daemon spectrum of a signal according to an embodiment of the present invention. FIG. 3 is an example of a daemon spectrum kurtosis according to an embodiment of the present invention. FIG. 4 is an example of a demon spectrum analysis process according to an embodiment of the present invention. FIG. 5 is a flowchart illustrating a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating another example of a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention. FIG. 7 is a flowchart illustrating another example of a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention. Specific details for implementing the invention

[0027] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0028] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0031] FIG. 1 is a drawing illustrating a cavitation monitoring device for a ship propeller according to an embodiment of the present invention.

[0032] A cavitation monitoring device (100) for a ship propeller according to one embodiment of the present invention may include an acoustic sensor (110), a vibration sensor (120), and a processor (130) as shown in FIG. 1.

[0033] The acoustic sensor (110) is installed on the ship and can output an acoustic signal by measuring the sound generated from the ship's propeller.

[0034] A vibration sensor (120) is installed on the ship and can measure vibrations generated from the ship's propeller and output a vibration signal.

[0035] The processor (130) can determine whether cavitation is occurring in the propeller of a ship using an acoustic signal or a vibration signal. The processor (130) can provide information to the user regarding whether cavitation is occurring based on the result of the cavitation determination.

[0036] The processor (130) can determine the minimum level of propeller noise by taking into account the marine environment. For example, the minimum level of propeller noise is a reference value of sound pressure at which sonar mounted on an external threat can detect and identify the ship's acoustic signal, and it may change depending on the marine environment. For example, the external threat may be a warship or submarine of a hostile nation. Additionally, the minimum level of propeller noise may increase in marine environments where noise increases, such as rain or typhoons, and decrease in marine environments where noise decreases, such as clear weather.

[0037] The processor (130) can set the maximum level of propeller noise to a sound pressure level that can be exceeded only when cavitation occurs in the propeller. Specifically, when cavitation occurs in the propeller above a certain level, the resulting sound pressure level may be higher than the sound pressure level generated by the marine environment, such as rain or waves, or by marine organisms adjacent to the vessel. Therefore, if the processor (130) sets the maximum level of propeller noise to a sound pressure level higher than the sound pressure level generated by the marine environment or by marine organisms adjacent to the vessel, the sound pressure level exceeding the maximum level when cavitation occurs in the propeller may be measured by the acoustic sensor (110) or estimated by the vibration sensor (120).

[0038] The processor (130) can determine the sound pressure level of the acoustic signal measured using the acoustic sensor (110). Additionally, the processor (130) can estimate the sound pressure level radiated from the propeller of the ship using the vibration signal measured by the vibration sensor (120).

[0039] If the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, exceeds the maximum level, the processor (130) may determine that cavitation is occurring in the propeller of the vessel. Additionally, if the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, is below the maximum level, the processor (130) may determine whether cavitation is occurring by considering additional conditions.

[0040] Specifically, if the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, is below the maximum level and exceeds the minimum level, the processor (130) may determine that cavitation is occurring in the propeller of the ship. Additionally, if the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, is below the minimum level, the processor (130) may determine that cavitation is not occurring in the propeller of the ship.

[0041] A processor (130) can obtain a demon spectrum by performing envelop analysis on an acoustic signal or a vibration signal, and can detect a Shaft Rate (SR) frequency component or a Blade Rate (BR) frequency component from the demon spectrum. Specifically, the processor (130) can extract an envelope time signal representing the envelope of an acoustic signal or a vibration signal by performing envelop analysis with a Hilbert transform applied to the acoustic signal or the vibration signal. Next, the processor (130) can obtain a demon spectrum by performing a Fast Fourier Transform (FFT) on the envelope time signal. Then, the processor (130) can extract an SR frequency component or a BR frequency component by converting the demon spectrum into the frequency domain.

[0042] If at least one of the 2SR frequency component, the BR frequency component, and the 2BR frequency component is detected in the acoustic signal or vibration signal, the processor (130) may determine that cavitation is occurring in the propeller of the ship. In this case, the 2SR frequency component may be twice the component of the SR frequency component, and the 2BR frequency component may be twice the component of the BR frequency component. Additionally, if the SR frequency component is detected simultaneously with at least one of the 2SR frequency component, the BR frequency component, or the 2BR frequency component, the processor (130) may determine that cavitation is occurring in the propeller of the ship. Additionally, if only the SR frequency component is detected in the acoustic signal or vibration signal, the processor (130) may determine that cavitation is not occurring in the propeller of the ship.

[0043] The processor (130) can determine the kurtosis of an acoustic signal or vibration signal for a spectrum at a specific frequency. The process by which the processor (130) determines the kurtosis of an acoustic signal or vibration signal for a spectrum at a specific frequency is described in detail with reference to FIG. 3. Furthermore, if the kurtosis value of an acoustic signal or vibration signal for a spectrum at a specific frequency exceeds a threshold kurtosis, the processor (130) can determine that cavitation is occurring in the propeller of the ship. Additionally, if the kurtosis value of an acoustic signal or vibration signal is below the threshold kurtosis, the processor (130) can determine that cavitation is not occurring in the propeller of the ship.

[0044] And, the processor (130) determines that cavitation occurs in the propeller of the ship when all of the following conditions are satisfied: condition 1, where the sound pressure level of the acoustic signal or the sound pressure level estimated based on the vibration signal exceeds the minimum level; condition 2, where the SR frequency component and the BR frequency component are simultaneously detected in the acoustic signal or the vibration signal; and condition 3, where the kurtosis value of the acoustic signal or the vibration signal for the spectrum at a specific frequency exceeds the threshold kurtosis. If there is a condition that does not satisfy any of condition 1, condition 2, and condition 3, it may determine that cavitation does not occur in the propeller of the ship.

[0045] In addition, if the sound pressure level of the acoustic signal, or the sound pressure signal estimated based on the vibration signal, exceeds the maximum level, the processor (130) may determine that cavitation has occurred regardless of whether conditions 1, 2, and 3 are satisfied.

[0046] The present invention can determine whether cavitation occurs in a ship's propeller using an acoustic signal or a vibration signal, and provide information regarding whether cavitation has occurred to a user.

[0047] FIG. 2 is an example of a daemon spectrum of a signal according to an embodiment of the present invention.

[0048] Graph (210) is an example of the result of the processor (130) performing a daemon spectrum analysis of an acoustic signal or a vibration signal when cavitation does not occur. Additionally, graph (220) is an example of the result of the processor (130) performing a daemon spectrum analysis of an acoustic signal or a vibration signal when cavitation occurs. When cavitation occurs, components of a specific frequency may increase as shown in graph (220).

[0049] FIG. 3 is an example of a daemon spectrum kurtosis according to an embodiment of the present invention.

[0050] The demon spectrum obtained by the processor (130) performing invelop analysis on an acoustic signal or vibration signal may be in a state where the BR component (310) and 2BR component (320) are increased and the kurtosis is increased.

[0051] At this time, the processor (130) uses mathematical formula 1 to determine the spectral kurtosis K representing the kurtosis of the acoustic signal or vibration signal for the spectrum at a specific frequency. X can decide.

[0052]

[0053] Here, E{} is the average function, and X(t) is the time domain signal at a specific frequency.

[0054] FIG. 4 is an example of a demon spectrum analysis process according to an embodiment of the present invention.

[0055] The processor (130) can perform envelope analysis by applying a Hilbert transform to the acoustic signal or vibration signal to extract an envelope time signal (440) representing the envelope of the acoustic signal or vibration signal.

[0056] When acoustic signals or vibration signals having different periods are modulated, the processor (130) can separate each signal before modulation through envelop analysis of the modulated signal, for example, when two sine signals (410, 420) with different periods occur simultaneously in the acoustic signal or vibration signal and amplitude modulation occurs, an amplitude-modulated signal (430) can be generated.

[0057] Next, the processor (130) uses mathematical formula 2 to signal (430) It can be Hilbert transformed.

[0058]

[0059] At this time, Is It is the function to be Hilbert transformed from, where t is time, and can be an integration variable. Also, the Hilbert-transformed signal It can be expressed as a complex-dimensional interpretation signal like Equation 3.

[0060]

[0061] And, the processor (130) uses mathematical formula 4 to obtain an interpretation signal of complex dimensions, an envelope time signal (440). It can be converted to.

[0062]

[0063] Next, the processor (130) envelope time signal (440) By converting it into a frequency domain signal (450) by performing a Fourier transform, the SR frequency component or the BR frequency component can be extracted.

[0064] FIG. 5 is a flowchart illustrating a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention.

[0065] In step (510), the processor (130) can determine a minimum level of propeller noise by taking into account the marine environment. For example, the minimum level of propeller noise may be a reference value of sound pressure that can be measured at a minimum distance by each of the acoustic sensor (110) and the vibration sensor (120).

[0066] In step (520), the processor (130) can determine the maximum level of propeller noise by considering when cavitation exceeding a preset value occurs in the propeller.

[0067] In step (530), the processor (130) can determine the sound pressure level of the propeller measured using the acoustic sensor (110). Additionally, the processor (130) can estimate the sound pressure level based on the vibration signal measured using the vibration sensor (120).

[0068] In step (540), the processor (130) can check whether the sound pressure level of the acoustic signal determined in step (530), or the sound pressure level estimated based on the vibration signal, exceeds the minimum level determined in step (510). If the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, exceeds the minimum level, the processor (130) can perform step (560). Additionally, if the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, is less than or equal to the minimum level, the processor (130) can perform step (550).

[0069] In step (550), the processor (130) can determine that no cavitation occurs.

[0070] In step (560), the processor (130) can check whether the sound pressure level of the acoustic signal determined in step (530), or the sound pressure level estimated based on the vibration signal, exceeds the maximum level determined in step (520). If the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, exceeds the maximum level, the processor (130) can perform step (570). Additionally, if the sound pressure level of the acoustic signal, or the sound pressure level estimated based on the vibration signal, is less than or equal to the maximum level, the processor (130) can perform step (580).

[0071] In step (570), the processor (130) can determine that cavitation is occurring in the propeller of the ship.

[0072] In step (570), the processor (130) may determine whether cavitation occurs in the propeller of the vessel by considering additional conditions. Specifically, step (570) may be operated according to the flowchart illustrated in FIG. 6 or FIG. 7. Additionally, step (570) may perform both the cavitation determination process illustrated in FIG. 6 and the cavitation determination process illustrated in FIG. 7, and if both the cavitation determination condition illustrated in FIG. 6 and the cavitation determination condition illustrated in FIG. 7 are satisfied, it may be determined that cavitation is occurring.

[0073] FIG. 6 is a flowchart illustrating another example of a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention, or a process for determining whether cavitation has occurred considering additional conditions. Steps (620) through (680) of FIG. 6 may be included in step (570) of FIG. 5. Additionally, steps (610) through (680) of FIG. 6 may be operated in an embodiment different from FIG. 5.

[0074] In step (610), the processor (130) can obtain an acoustic signal from the acoustic sensor (110) or obtain a vibration signal from the vibration sensor (120).

[0075] In step (620), the processor (130) can obtain a demon spectrum by performing envelop analysis on the acoustic signal or vibration signal obtained in step (610). Specifically, the processor (130) can extract an envelope time signal representing the envelope of the acoustic signal or vibration signal by performing envelop analysis by applying a Hilbert transform to the acoustic signal or vibration signal.

[0076] In step (630), the processor (130) can detect frequency components from the daemon spectrum obtained in step (620). Specifically, the processor (130) can convert the envelope time signal into the frequency domain to extract SR frequency components or BR frequency components.

[0077] In step (640), the processor (130) can check whether an SR frequency component was detected in step (630). If an SR frequency component is detected, the processor (130) can perform step (660). If an SR frequency component is not detected, the processor (130) can perform step (650).

[0078] In step (650), the processor (130) can determine whether at least one of the 2SR frequency component, the BR frequency component, and the 2BR frequency component was detected in step (630). If at least one of the 2SR frequency component, the BR frequency component, and the 2BR frequency component is detected, the processor (130) can perform step (670). If at least one of the 2SR frequency component, the BR frequency component, and the 2BR frequency component is not detected, the processor (130) can perform step (680).

[0079] In step (660), the processor (130) can determine whether multiple frequency components are detected simultaneously in step (630). Step (660) is performed when an SR frequency component is detected in step (630). Accordingly, if an SR frequency component is detected simultaneously with at least one of a 2SR frequency component, a BR frequency component, or a 2BR frequency component, the processor (130) can determine that multiple frequency components are detected simultaneously. Additionally, if only an SR frequency component is detected alone, the processor (130) can determine that multiple frequency components are not detected simultaneously.

[0080] If multiple frequency components are detected simultaneously, the processor (130) can perform step (670). If multiple frequency components are not detected simultaneously, the processor (130) can perform step (680).

[0081] In step (670), the processor (130) can determine that cavitation is occurring in the propeller of the ship.

[0082] In step (680), the processor (130) can determine that no cavitation occurs.

[0083] FIG. 7 is a flowchart illustrating another example of a method for monitoring cavitation of a ship propeller according to an embodiment of the present invention, or a process for determining whether cavitation has occurred considering additional conditions. Steps (720) through (760) of FIG. 7 may be included in step (570) of FIG. 5. Additionally, steps (710) through (760) of FIG. 7 may be operated in an embodiment different from FIG. 5.

[0084] In step (710), the processor (130) can obtain an acoustic signal from the acoustic sensor (110) or obtain a vibration signal from the vibration sensor (120).

[0085] In step (720), the processor (130) can obtain a demon spectrum by performing envelop analysis on the acoustic signal or vibration signal obtained in step (710). Specifically, the processor (130) can extract an envelope time signal representing the envelope of the acoustic signal or vibration signal by performing envelop analysis by applying a Hilbert transform to the acoustic signal or vibration signal.

[0086] In step (730), the processor (130) can detect frequency components from the daemon spectrum obtained in step (720). Specifically, the processor (130) can convert the envelope time signal into the frequency domain to extract SR frequency components or BR frequency components.

[0087] In step (730), the processor (130) can determine the kurtosis value of the acoustic signal or vibration signal for the daemon spectrum at a specific frequency. Then, the processor (130) can check whether the kurtosis value of the acoustic signal or vibration signal for the spectrum at a specific frequency exceeds a threshold kurtosis value. If the kurtosis value of the acoustic signal or vibration signal for the spectrum at a specific frequency exceeds the threshold kurtosis value, the processor (130) can perform step (750). Additionally, if the kurtosis value of the acoustic signal or vibration signal is less than or equal to the threshold kurtosis value, the processor (130) can perform step (760).

[0088] In step (750), the processor (130) can determine that cavitation is occurring in the propeller of the ship.

[0089] In step (760), the processor (130) can determine that no cavitation occurs.

[0090] The present invention can determine whether cavitation occurs in a ship's propeller using an acoustic signal or a vibration signal, and provide information regarding whether cavitation has occurred to a user.

[0091] Meanwhile, the cavitation monitoring device for a ship propeller based on ignition data or the cavitation monitoring method for a ship propeller based on ignition data according to the present invention is written as a program that can be executed on a computer and can also be implemented on various recording media such as magnetic storage media, optical reading media, and digital storage media.

[0092] Implementations of the various technologies described herein may be implemented as digital electronic circuits, or as computer hardware, firmware, software, or combinations thereof. Implementations may be implemented as computer programs tangibly embodied in a computer program product, for example, a machine-readable storage device (computer-readable medium), for processing by the operation of a data processing device, e.g., a programmable processor, a computer, or a plurality of computers, or for controlling such operation. Computer programs such as the computer program(s) described above may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. Computer programs may be deployed to be processed on one computer or a plurality of computers at one site, or distributed across a plurality of sites and interconnected by a communication network.

[0093] Processors suitable for processing computer programs include, for example, both general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Generally, the processor will receive instructions and data from read-only memory or random access memory, or both. The elements of the computer may include at least one processor that executes instructions and one or more memory devices that store instructions and data. Generally, the computer may include one or more mass storage devices that store data, for example, magnetic, magneto-optical disks, or optical disks, or may be combined to receive data from these, transmit data to these, or both. Information carriers suitable for embodying computer program instructions and data include, for example, semiconductor memory devices, magnetic media such as hard disks, floppy disks, and magnetic tapes; optical media such as CD-ROMs (Compact Disk Read Only Memory) and DVDs (Digital Video Disks); magneto-optical media such as floptical disks; ROMs (Read Only Memory); RAMs (Random Access Memory); flash memory; EPROMs (Erasable Programmable ROM); EEPROMs (Electrically Erasable Programmable ROM); etc. Processors and memory may be supplemented by or included in special-purpose logic circuit organizations.

[0094] Additionally, a computer-readable medium may be any available medium accessible by a computer and may include all computer storage media.

[0095] Although this specification contains details of a number of specific embodiments, they should not be understood as limiting the scope of any invention or claimables, but rather as descriptions of features that may be characteristic of a specific embodiment of a specific invention. Specific features described in this specification in the context of individual embodiments may be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any appropriate sub-combination. Furthermore, while features may operate in a specific combination and be described as initially claimed, one or more features from the claimed combination may be excluded from the combination in some cases, and the claimed combination may be changed to a sub-combination or a variation of the sub-combination.

[0096] Likewise, although operations are depicted in the drawings in a specific order, this should not be understood as requiring that such operations be performed in that specific or sequential order depicted to obtain a desirable result, or that all depicted operations must be performed. In certain cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various device components of the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and devices can generally be integrated together into a single software product or packaged into multiple software products.

[0097] Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples provided to aid understanding and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that other variations based on the technical concept of the present invention are possible in addition to the embodiments disclosed herein. Explanation of the symbols

[0098] 100: Cavitation monitoring device 110: Acoustic sensor 120: Vibration sensor 130: Processor

Claims

Claim 1 A step of acquiring an acoustic signal from an acoustic sensor that measures acoustics generated from a ship's propeller, or acquiring a vibration signal from a vibration sensor that measures vibrations generated from a ship's propeller; a step of acquiring a demon spectrum by performing envelop analysis on the acoustic signal or the vibration signal; a step of detecting frequency components from the demon spectrum; a step of determining that cavitation is occurring in the propeller if 2SR (Shaft Rate), BR (Blade Rate), or 2BR is included in the detected frequency components; a step of checking whether, if SR is included in the detected frequency components, SR is simultaneously detected with at least one of 2SR, BR, or 2BR; a step of determining that cavitation is occurring in the propeller if SR is simultaneously detected with at least one of 2SR, BR, or 2BR. A method for monitoring cavitation in a ship propeller, comprising the step of determining that cavitation does not occur in the propeller if at least one of 2SR, BR, and 2BR is not included in the detected frequency component, or if only the SR component is included. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete

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