Ship shaft frequency current extraction method and system based on shaft rotating speed real-time measurement

Abstract

The invention discloses a ship shaft frequency current extraction method and system based on shaft rotating speed real-time measurement, and relates to the technical field of ship shaft frequency current extraction, shaft frequency electric field characteristic monitoring and control and the like. The ship shaft frequency current extraction method based on shaft rotating speed real-time measurement mainly comprises the steps that shaft rotating speed data is extracted, and the fundamental frequency of shaft current is calculated; and separating and extracting a fundamental component and each harmonic component of the shaft current signal, finally constructing a current time domain signal and a frequency domain characteristic signal related to the propeller shaft rotation frequency according to a shaft rotation speed data calculation result and a shaft current signal calculation result, and obtaining a propeller shaft current frequency spectrum. According to the ship shaft frequency current extraction method and system based on real-time measurement of the shaft rotating speed, the real-time performance and accuracy of propeller shaft frequency current signal extraction in a complex ship environment can be improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of ship shaft frequency current extraction, shaft frequency electric field characteristic monitoring and control, and more specifically, to a ship shaft frequency current extraction method and system based on real-time measurement of shaft speed. Background Art

[0002] When a ship is sailing in seawater, corrosion current and anti-corrosion current form a current loop between "hull propulsion shaft-propeller-seawater-hull", and then generate shaft frequency electric field signals around the ship under the modulation of the propeller. The signal amplitude can usually reach The signal frequency is concentrated between 0.5 and 30 Hz. This signal has a distinct line spectrum characteristic, making it measurable by electric field sensors and a target for detection, identification, and attack by underwater weapons such as electric field detection arrays, buoys, and mines. Therefore, accurate and stable detection of propulsion shaft current signals, especially extraction of shaft frequency current signals related to shaft rotation frequency, is crucial for monitoring and controlling the shaft frequency electric field characteristics of ships.

[0003] Measuring the current signal related to the shaft rotation frequency on a propeller shaft requires ensuring safe operation. Non-contact shaft current measurement is typically employed. Currently, non-contact measurement solutions primarily employ sensors such as current transformers, photocurrent sensors, and magnetic modulators, measuring shaft current signals through electromagnetic sensing techniques or magneto-optical effects. However, in practical applications, each solution struggles to reconcile the trade-offs between range and accuracy, interference immunity, and long-term stability. Numerous researchers have employed complex algorithm optimization methods, such as harmonic wavelet and improved generalized harmonic wavelet algorithms, to improve detection accuracy and interference immunity. In 2004, Chen Cong et al., in their paper "Research on Detection of Large Shaft Currents on Ships," proposed extracting the second harmonic signal from the magnetic core saturation characteristics to infer the shaft current intensity, providing parameters for analyzing the ship's electric field distribution. This method is simple in structure and suitable for detecting weak DC or low-frequency currents. However, it is susceptible to interference from ambient magnetic fields and requires complex post-processing algorithms to improve the signal-to-noise ratio. Linearity is poor when measuring low or high currents, significantly increasing errors. In recent years, researchers have attempted to achieve high-precision detection of electric field-related characteristic signals under low signal-to-noise ratio conditions through advanced signal processing technology. In 2024, Cheng Jinfang et al. proposed a method of "combining coherent accumulation and AR filtering" in "Ship Shaft Frequency Electric Field Signal Processing Method Combining Coherent Accumulation and AR Filtering" to improve the signal-to-noise ratio of ship shaft frequency electric field signals. This method can still maintain high detection sensitivity under low signal-to-noise ratio conditions, but it requires multi-cycle data accumulation, has high requirements for signal stability, consumes a lot of computing resources, and has limited real-time performance. It is suitable for field testing of electric fields of ships at sea, but there are still significant limitations in extracting reliable and stable shaft current characteristic signals in the complex electromagnetic environment inside the ship.

[0004] In addition, when extracting the current signal related to the shaft rotation frequency on the ship, there are interference factors such as multi-branch harmonic signal crosstalk and complex electromagnetic environment radiation in the cabin. Under certain conditions, the shaft frequency characteristic signal may even be overwhelmed, resulting in complex algorithms and signal extraction technologies being unable to accurately and stably detect the shaft frequency current signal, causing the shaft current detection equipment to fail and the shaft frequency electric field characteristic control measures to fail.

[0005] How to extract the propulsion shaft frequency current signal in real time and accurately in a complex ship environment is an urgent problem to be solved.

[0006] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0007] The purpose of the present invention is to provide a method and system for extracting shaft frequency current of a ship based on real-time measurement of shaft speed, which can improve the real-time performance and accuracy of propulsion shaft frequency current signal extraction in complex ship environments.

[0008] The present invention provides a method for extracting shaft frequency current of a ship based on real-time measurement of shaft speed, comprising the following steps: S1: acquiring an electrical signal on the shaft and a shaft speed signal, summing and averaging the electrical signal on the shaft and removing the DC component to obtain a DC component and a real part array; S2: performing FFT operation on the real part array to obtain the real part after the operation; S3: obtaining a shaft frequency signal according to the shaft speed signal; S4: confirming that the shaft frequency signal is greater than 0, obtaining the shaft frequency according to the shaft frequency signal, taking the shaft frequency as the shaft current fundamental frequency signal, and taking the frequency doubling point of the shaft frequency as the shaft current. S5: confirm that the shaft frequency signal is equal to 0, and use the maximum amplitude value in the real part array as the fundamental component of the simulated shaft current, and use the frequency corresponding to the maximum amplitude value as the fundamental frequency to obtain the shaft current fundamental component and each harmonic component according to the real part after the operation; S6: obtain the current signal spectrum related to the propulsion shaft rotation frequency according to the DC component, the shaft current fundamental component, each harmonic component and the fundamental frequency.

[0009] Furthermore, the above-mentioned on-axis electrical signal is an on-axis digital voltage or an on-axis digital current.

[0010] Furthermore, step S2 specifically includes: , , , , , in, is the rotation factor, is the rotation factor index, is the number of digital signal sampling points, is an imaginary unit, is the real part of the real array after FFT operation on the odd part, The real part of the even part of the real array after FFT operation, The current level.

[0011] The present invention also provides a system applied to the above-mentioned ship shaft frequency current extraction method based on real-time measurement of shaft speed, comprising: at least one set of magnetic / optical sensors, a signal comprehensive processing module, a data analysis and calculation module, a communication module and a power supply module; the magnetic / optical sensor is used to obtain the electrical signal on the shaft and transmit the electrical signal on the shaft to the signal comprehensive processing module; the signal comprehensive processing module is used to sample, amplify, and perform analog-to-digital conversion on the input signal, and transmit the processed signal to the data analysis and calculation module; the data analysis and calculation module is used to obtain the time domain signal and frequency domain characteristic signal of the propulsion shaft rotation frequency-related current by utilizing the above-mentioned ship shaft frequency current extraction method based on real-time measurement of shaft speed, and obtain the propulsion shaft current spectrum; the communication module is used to receive the shaft speed signal, send the current signal and equipment status and fault information related to the propulsion shaft rotation frequency, and transmit them to the data analysis and calculation module.

[0012] Furthermore, the above system also includes a rotation speed measurement sensor, which is used to obtain the shaft rotation speed signal and transmit it to the signal comprehensive processing module.

[0013] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the ship shaft frequency current extraction method based on real-time measurement of shaft speed are implemented.

[0014] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the above-mentioned method for extracting the ship shaft frequency current based on real-time measurement of the shaft speed are implemented.

[0015] The present invention also provides a computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for extracting ship shaft frequency current based on real-time measurement of shaft speed.

[0016] The implementation of the ship shaft frequency current extraction method and system based on real-time shaft speed measurement provided by the present invention has the following beneficial effects: The present invention is based on the experience of actual ship shaft current signal measurement and long-term shaft frequency electric field testing, based on the intrinsic correlation between the propulsion shaft speed and the shaft current fundamental frequency, and according to the law that the ship propeller rotation frequency is consistent with the shaft current fundamental frequency, a ship shaft frequency current extraction method based on real-time measurement of shaft speed is proposed. This method monitors the propulsion shaft speed in real time through a shaft speed measurement sensor, and can achieve accurate measurement of the shaft current frequency. The speed sensor can be flexibly arranged according to actual needs. It can be built into the equipment or installed outside the equipment, so as to adapt to different working conditions and meet diverse monitoring needs; the speed signal is used as the input variable, and the fundamental frequency of the shaft current is calculated by extracting the shaft speed data; combined with the shaft current signal measured by the magnetic field measurement sensor or the photocurrent sensor, advanced signal processing technology is used to further separate and extract the fundamental component and each harmonic component, and finally construct the current time domain signal and frequency domain characteristic signal related to the propulsion shaft rotation frequency, and obtain the propulsion shaft current spectrum. This invention fully addresses the needs of both onboard application and test and debugging, proposing a fusion extraction scheme for shaft frequency current, tailored to different operating conditions. This approach extracts the ship's shaft frequency current signal based on shaft speed measurement and a fast Fourier transform (FFT) analysis method, respectively, targeting the current generated by the rotating shaft and debugging the simulated power supply signal. This allows for fusion extraction of shaft frequency current under different operating conditions. These two methods enable automated judgment and operation, improving the device's adaptability while significantly enhancing the system's stability and reliability in diverse scenarios.

[0017] The present invention uses a non-contact shaft speed measurement solution to monitor shaft speed in real time, supplemented by a magnetic field measurement sensor or photocurrent sensor, to extract current signals related to the propulsion shaft rotation frequency through a software and hardware approach. Only a magnetic field measurement sensor or photocurrent sensor, a shaft speed sensor, and a signal acquisition and processing unit are required to extract the ship's shaft frequency current. Under low signal-to-noise ratio conditions, particularly in the complex ship, machine, and electromagnetic interference environments in which a ship's propulsion shaft is located, the present invention can reliably and stably extract shaft current signals related to the ship's shaft frequency electric field. This method can also accurately extract specified subharmonic signals.

[0018] The shaft frequency current extraction method proposed in this paper utilizes minimal computing resources and offers high computational efficiency. It replaces the previously cumbersome process and complex calculations with a more concise and efficient direct speed extraction method, significantly reducing runtime and hardware requirements. While maintaining high performance, it minimizes resource consumption and hardware dependency, achieving higher computational efficiency with fewer resources, effectively meeting the application requirements of embedded devices or real-time processing systems.

[0019] The present invention has demonstrated the advantages of high reliability and stability during long-term testing and application on actual ships. Compared with the traditional scheme of extracting propulsion shaft current through complex algorithm optimization or signal processing technology, the present invention adopts an additional shaft speed measurement sensor to monitor the propulsion shaft speed in real time, which can not only realize real-time and accurate measurement of the shaft current frequency, but also can operate stably and reliably for a long time in a complex ship environment, and is particularly suitable for ship equipment applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 This is a flow chart of a method for extracting ship shaft frequency current based on real-time measurement of shaft speed provided by the present invention; Figure 2 This is a schematic diagram of the shaft frequency current detection system provided by the present invention; Figure 3 is a schematic diagram of a shaft frequency current detection system according to another embodiment of the present invention; Figure 4 This is a flow chart of the FFT calculation program of the ship shaft frequency current extraction method based on real-time measurement of shaft speed provided by the present invention; Figure 5 It is a structural block diagram of the computer device provided by the present invention. DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0022] Figure 1 A schematic diagram of a method for extracting shaft frequency current of a ship based on real-time measurement of shaft speed in this embodiment is shown. In this embodiment, the method for extracting shaft frequency current of a ship based on real-time measurement of shaft speed includes the following steps: S1: Acquire the shaft electrical signal and shaft speed signal, sum and average the shaft electrical signal, and remove the DC component to obtain a DC component and a real part array; In an exemplary embodiment, the on-axis electrical signal is an on-axis digital voltage or an on-axis digital current; S2: Perform FFT operation on the real part array to obtain the real part after operation; In an exemplary embodiment, step S2 specifically includes: , , , , , in, is the rotation factor, is the rotation factor index, is the number of digital signal sampling points, is an imaginary unit, is the real part of the real array after FFT operation on the odd part, The real part of the even part of the real array after FFT operation, is the current level; S3: Obtaining a shaft frequency signal according to the shaft speed signal; S4: confirming that the shaft frequency signal is greater than 0, obtaining the shaft frequency according to the shaft frequency signal, taking the shaft frequency as the shaft current fundamental frequency signal, taking the multiple frequency point of the shaft frequency as the shaft current harmonic frequency, and obtaining the shaft current fundamental component, each harmonic component, and fundamental frequency according to the real part after the operation, the shaft current fundamental frequency signal, and the shaft current harmonic frequency; S5: Confirm that the shaft frequency signal is equal to 0, use the maximum amplitude value in the real part array as the fundamental component of the simulated shaft current, and based on the real part after the operation, use the frequency corresponding to the maximum amplitude value as the fundamental frequency to obtain the shaft current fundamental component and each harmonic component; S6: Obtain a current signal spectrum related to the propulsion shaft rotation frequency according to the DC component, the shaft current fundamental component, each harmonic component and the fundamental frequency.

[0023] The present embodiment provides a system applied to the above-mentioned ship shaft frequency current extraction method based on real-time measurement of shaft speed, the system comprising: at least one set of magnetic / optical sensors, a signal integration processing module, a data analysis and calculation module, a communication module and a power supply module; the magnetic / optical sensor is used to obtain the electrical signal on the shaft and transmit the electrical signal on the shaft to the signal integration processing module; the signal integration processing module is used to sample, amplify, and perform analog-to-digital conversion on the input signal, and transmit the processed signal to the data analysis and calculation module; the data analysis and calculation module is used to obtain the time domain signal and frequency domain characteristic signal of the propulsion shaft rotation frequency-related current by using the above-mentioned ship shaft frequency current extraction method based on real-time measurement of shaft speed, and obtain the propulsion shaft current spectrum; the communication module is used to receive the shaft speed signal, send the current signal and equipment status and fault information related to the propulsion shaft rotation frequency, and transmit them to the data analysis and calculation module.

[0024] In an exemplary embodiment, the system further includes a rotational speed measurement sensor, which is used to obtain a shaft rotational speed signal and transmit the signal to the signal integration processing module.

[0025] In some embodiments, the above system may also be implemented in the following manner.

[0026] like Figure 2 The system consists of two magnetic / optical sensors, a speed measurement sensor, a signal comprehensive processing module, a data analysis and calculation module, a communication module and a power supply module.

[0027] First, the shaft current-related signal (voltage or current form) is measured by a magnetic / optical sensor (magnetic field measurement sensor or photocurrent sensor), and the shaft speed information is measured by a non-contact speed measurement sensor. The signals measured by the above sensors are sent to the signal integration processing module for sampling, amplification, analog-to-digital conversion (ADC), etc. In order to improve the anti-interference ability, the signal integration processing module adopts differential sampling, signal conditioning, multi-stage amplification and other methods to improve the signal anti-interference ability and detection accuracy.

[0028] The data analysis and calculation module primarily performs computational analysis on processed digital signals, including shaft current-related signals and shaft speed signals. It employs noise suppression and online sliding FFT technology to accurately extract weak alternating currents from the propulsion shaft's current signals, extracting the shaft current's DC component and AC harmonics. Simultaneously, the measured shaft speed signal is processed in real time to obtain the shaft current's fundamental frequency. Combined with the shaft current signal extracted by the magnetic / optical sensor, the shaft current fundamental frequency corresponding to the propulsion shaft's rotational frequency is obtained, and the harmonics of the shaft current signal are extracted. This allows for the precise extraction of weak alternating currents from large DC components, with an AC current extraction error ≤ 0.25% and a minimum effective current measurement ≤ 1mA.

[0029] The communication module primarily transmits the extracted DC, AC, and harmonic signals of the propulsion shaft current signal via the CAN communication interface or analog signals, providing input for electric field characteristic monitoring, analysis, and control. It can also transmit information such as the equipment's operating status and faults.

[0030] The power supply module provides power for the magnetic / optical sensor, speed measurement sensor, signal integrated processing module, data analysis and calculation module, communication module, etc.

[0031] The speed measurement sensor in this patent can be integrated into the device, or other systems can send the measured shaft speed to the data analysis and calculation module through the communication module, such as Figure 3 shown.

[0032] In some embodiments, the above-mentioned method for extracting ship shaft frequency current based on real-time measurement of shaft speed can also be implemented in the following manner.

[0033] The software control process of the ship shaft current extraction method proposed in this embodiment is as follows: first, the shaft current signal is measured by a magnetic field measurement sensor or a photocurrent sensor, and the shaft speed sensor is used to measure the shaft speed. On the other hand, the magnetic / optical signal measured by the magnetic field measurement sensor or the photocurrent sensor is converted into analog-to-digital, and then sampling and calculation are performed to obtain floating-point data. , further sum and average the array, remove the DC component, and get the real part array The real part after operation is obtained by FFT operation module Among them, the FFT algorithm module intends to use the butterfly FFT operation structure, its basic principle and program flow chart are as follows Figure 4 shown.

[0034] The current level input sampling value is divided into odd and even parts, respectively. and , the rotation factor is , The output is: , , , , in, is the rotation factor index, For the current level (starting from 1), output: and Store them in the corresponding positions of the next level respectively.

[0035] On the other hand, the shaft speed signal measured by the shaft speed sensor is sampled and processed, and the shaft frequency signal is extracted by calculation. At this time, the shaft frequency signal is judged. When the shaft frequency signal is greater than 0, the calculated shaft frequency is used as the fundamental frequency signal of the shaft current, and the multiple frequency point of the shaft frequency is used as the harmonic frequency of the shaft current. The fundamental component, harmonic components and fundamental frequency of the shaft current are converted into the fundamental component, harmonic components and fundamental frequency of the shaft current. When the shaft frequency signal is 0, the shaft does not rotate under the actual ship working condition, and there is no shaft frequency feature in the shaft current signal. Under the laboratory working condition, it is in the debugging state, so find The maximum value of the amplitude is defined as the fundamental component of the simulated shaft current, and the corresponding frequency is the fundamental frequency of the shaft frequency, and then the fundamental component and each harmonic component are obtained.

[0036] Finally, according to the DC component and fundamental frequency of the shaft current, combined with the calculated fundamental component and each harmonic component, the current signal spectrum related to the propulsion shaft rotation frequency can be obtained.

[0037] The communication module converts the propulsion shaft current related information into digital or analog signal output, providing the necessary input for shaft frequency electric field characteristic analysis and control.

[0038] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When executed by a processor, the computer program implements the steps of the aforementioned method for extracting ship shaft frequency current based on real-time shaft speed measurement. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD), or a solid-state drive (SSD); the storage medium may also include a combination of the aforementioned types of memory.

[0039] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the above-mentioned method for extracting the ship shaft frequency current based on real-time measurement of the shaft speed are implemented.

[0040] like Figure 5 As shown, the computer device 120 may include: at least one processor 121, such as a central processing unit (CPU), at least one communication interface 123, a memory 124, and at least one communication bus 122. The communication bus 122 is used to enable communication between these components. The communication interface 123 may include a display and a keyboard. Optionally, the communication interface 123 may also include a standard wired interface or a wireless interface. The memory 124 may be a high-speed random access memory (RAM) or a non-volatile memory, such as at least one disk drive. The memory 124 may optionally be at least one storage device located remote from the processor 121. The memory 124 stores application programs, and the processor 121 invokes program code stored in the memory 124 to execute any of the aforementioned method steps. The communication bus 122 may be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, for example. The communication bus 122 can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 5 The fact that only one line is used in the figure does not mean that there is only one bus or only one type of bus. Memory 124 may include volatile memory, such as random-access memory (RAM); it may also include non-volatile memory, such as flash memory, a hard disk drive (HDD), or a solid-state drive (SSD); or it may include a combination of these types of memory. Processor 121 may be a central processing unit (CPU), a network processor (NP), or a combination of a CPU and an NP. Processor 121 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof. Optionally, the memory 124 is further configured to store program instructions. The processor 121 may call the program instructions to implement the ship shaft frequency current extraction method based on real-time measurement of shaft speed as in this embodiment.

[0041] This embodiment provides a computer program product, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for extracting ship shaft frequency current based on real-time measurement of shaft speed.

[0042] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for extracting ship shaft frequency current based on real-time measurement of shaft speed, characterized in that: The following steps are involved: S1: Acquire the shaft electrical signal and shaft speed signal, sum and average the shaft electrical signal, and remove the DC component to obtain a DC component and a real part array; S2: Perform FFT operation on the real part array to obtain the real part after operation; S3: Obtaining a shaft frequency signal according to the shaft speed signal; S4: confirming that the shaft frequency signal is greater than 0, obtaining the shaft frequency according to the shaft frequency signal, taking the shaft frequency as the shaft current fundamental frequency signal, taking the multiple frequency point of the shaft frequency as the shaft current harmonic frequency, and obtaining the shaft current fundamental component, each harmonic component, and fundamental frequency according to the real part after the operation, the shaft current fundamental frequency signal, and the shaft current harmonic frequency; S5: Confirm that the shaft frequency signal is equal to 0, use the maximum amplitude value in the real part array as the fundamental component of the simulated shaft current, and based on the real part after the operation, use the frequency corresponding to the maximum amplitude value as the fundamental frequency to obtain the shaft current fundamental component and each harmonic component; S6: Obtain a current signal spectrum related to the propulsion shaft rotation frequency according to the DC component, the shaft current fundamental component, each harmonic component and the fundamental frequency.

2. The method for extracting ship shaft frequency current based on real-time measurement of shaft speed according to claim 1 is characterized in that: The on-axis electrical signal is an on-axis digital voltage or an on-axis digital current.

3. The method for extracting ship shaft frequency current based on real-time measurement of shaft speed according to claim 1, characterized in that: Step S2 specifically includes: ， ， ， ， ， in, is the rotation factor, is the rotation factor index, is the number of digital signal sampling points, is an imaginary unit, is the real part of the real array after FFT operation on the odd part, The real part of the even part of the real array after FFT operation, The current level.

4. A system for extracting the ship shaft frequency current based on the real-time measurement of shaft speed according to any one of claims 1 to 3, characterized in that: The system includes: at least one magnetic / optical sensor, a signal comprehensive processing module, a data analysis and calculation module, a communication module and a power supply module; the magnetic / optical sensor is used to obtain the electrical signal on the shaft and transmit the electrical signal on the shaft to the signal comprehensive processing module; the signal comprehensive processing module is used to sample, amplify, and perform analog-to-digital conversion on the input signal, and transmit the processed signal to the data analysis and calculation module; the data analysis and calculation module is used to obtain the time domain signal and frequency domain characteristic signal of the propulsion shaft rotation frequency-related current by using the ship shaft frequency current extraction method based on real-time measurement of shaft speed as described in any one of claims 1-3, and obtain the propulsion shaft current spectrum; the communication module is used to receive the shaft speed signal, send the current signal related to the propulsion shaft rotation frequency and equipment status and fault information, and transmit them to the data analysis and calculation module.

5. The system according to claim 4, characterized in that: The system further comprises a rotation speed measurement sensor, which is used to obtain a shaft rotation speed signal and transmit the signal to the signal comprehensive processing module.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for extracting ship shaft frequency current based on real-time measurement of shaft speed as described in any one of claims 1 to 3 are implemented.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the ship shaft frequency current extraction method based on real-time measurement of shaft speed as described in any one of claims 1-3 are implemented.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for extracting ship shaft frequency current based on real-time measurement of shaft speed as described in any one of claims 1 to 3 are implemented.

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