A simulation method for non-uniform broadband modulated noise in ship maneuvering state

Abstract

This invention discloses a method for simulating non-uniform broadband modulation noise under ship maneuvering conditions. First, the basic parameters of the ship target and the propeller speed during the simulation time period are set. Then, an energy accumulation model between propeller speed and ship speed is established, and the time series of ship speed and acceleration during this time period are calculated. Next, based on the ship's basic parameters, propeller speed, and ship speed and acceleration, the frequency-division wideband continuous spectrum components and envelope modulation spectrum components of the ship's broadband modulation noise are obtained. Finally, the above components of each frequency band are superimposed to obtain the simulation signal sequence of non-uniform broadband modulation noise under ship maneuvering conditions. Using this method, a more realistic model of the relationship between propeller speed and ship speed and acceleration can be obtained, and by employing frequency-division modulation, a more refined simulation of ship broadband modulation noise with maneuvering characteristics can be achieved.

Description

Technical Field

[0001] This invention relates to a method for simulating non-uniform broadband modulation noise under ship maneuvering conditions, belonging to the field of signal processing. Background Technology

[0002] In marine research, underwater acoustics is the primary means of acquiring underwater information. The radiated noise signals generated by ships during their movement contain important characteristic information, making the study of ship noise a key direction in marine technology. Such research requires a large amount of measured or simulated data to verify and test the design of signal processing algorithms. Compared to measured data, simulation data is more cost-effective to acquire, allowing for convenient and rapid acquisition of large amounts of data and addressing the problem of insufficient measured data. Furthermore, using simulation data facilitates variable control and makes it easier to obtain data under different parameters. Additionally, since simulation parameters are known in advance, it is more conducive to calibrating the parameters of signal processing algorithms or building large labeled datasets. Broadband modulation noise is the most significant component of ship radiated noise and has the highest simulation requirements, thus research on broadband modulation noise simulation methods has practical significance and promising application prospects.

[0003] Existing broadband modulation noise simulation methods often assume, on the one hand, that the target is in a stable motion state, and the simulated broadband modulation signal remains unchanged in the time domain; on the other hand, the broadband modulation signal is generally obtained by simply multiplying the broadband continuous spectrum and the envelope modulation spectrum. However, in real-world scenarios and algorithm research, ship maneuvers often occur, resulting in changes in the propeller shaft frequency. Changes in the propeller shaft frequency of the simulated ship target cause changes in the ship's speed and acceleration. These changes further lead to changes in the spectral levels and peak shifts of the broadband continuous spectrum, as well as changes in the modulation depth of the envelope modulation spectrum. Furthermore, the modulation depth also shifts to some extent across different noise frequencies. Traditional broadband modulation noise simulation methods cannot satisfy the various characteristics of ship maneuvers described above and cannot effectively reflect the overall trend of broadband modulation noise changes caused by target maneuvers. Summary of the Invention

[0004] Objective: To address the problems existing in the prior art, this invention proposes a simulation method for non-uniform broadband modulation noise under ship maneuvering conditions. By calculating a more realistic model of the relationship between propeller speed and ship speed and acceleration, and employing frequency-band modulation, a more refined broadband modulation spectrum model of ship radiated noise with maneuvering characteristics is effectively established. The method first sets the basic parameters of the ship target and the propeller speed within the simulation time period; then, it establishes an energy accumulation model between propeller speed and ship speed, calculating the time series of ship speed and acceleration within that time period; next, based on the ship's basic parameters, propeller speed, and ship speed and acceleration, it obtains the frequency-band continuous spectrum components and envelope modulation spectrum components of the ship's broadband modulation noise; finally, based on the above components of each frequency band, it superimposes to obtain the simulation signal sequence of non-uniform broadband modulation noise under ship maneuvering conditions.

[0005] Technical Solution: To achieve the above objectives, the technical solution adopted by this invention is: a simulation method for non-uniform broadband modulation noise under ship maneuvering conditions, the simulation method comprising the following steps:

[0006] Step 1: Set the basic parameters of the simulated ship target, including its maximum speed v. max Maximum propeller speed R max And the ship's displacement (m).

[0007] Step 2: Set the time series R of the propeller speed of the simulated ship target within the simulation period. T = {R[1],R[2],…,R[T]}, where the propeller speed R[t] at any time t is less than the maximum speed R. max The value is a non-negative number, with the unit being revolutions per minute (rpm). t is the simulation time number, and T is the length of the simulation signal sequence.

[0008] Step 3: Based on the physical model of the ship's navigation, establish the energy accumulation model of the simulated target, obtain the relationship between propeller speed and the ship's real-time speed and acceleration, and thus obtain the time series R of the propeller speed of the simulated ship target. T Obtain the time series of real-time airspeed v T ={v[1],v[2],…,v[T]} and the time series of acceleration a T ={a[1],a[2],…,a[T]}, where v[t] and a[t] are the real-time speed and acceleration at time t, respectively, as follows:

[0009] The real-time speed v[t] of the simulated ship target at time t is calculated using equation (1):

[0010]

[0011] Wherein, coefficients k1 and k2 are positive numbers, used to adjust the kinetic energy provided by a certain propeller speed per unit time. The relationship between coefficients k1 and k2 satisfies equation (2):

[0012]

[0013] When the simulation time interval is t0, the acceleration a[t] of the simulated ship target at time t is calculated by equation (3):

[0014]

[0015] Step 4: Time series n of the frequency-division continuous spectrum components of the broadband modulation noise of the simulated ship target. T The calculation method is as follows:

[0016] The total noise level L above 100Hz is calculated using equation (4). S [t]:

[0017]

[0018] The corresponding frequency f of the continuous spectrum component peak of the simulated ship noise is calculated using equation (5). m [t]:

[0019]

[0020] Construct a Butterworth filter for shaping filtering, with the filter parameters set as follows: passband cutoff frequency W pl Take (f) m [t]-30Hz), W ph Take (f) m [t]+30Hz), passband cutoff frequency W sl Take f m [t] / 2, W sh Take 8000Hz, passband ripple R p Take 3dB, stopband attenuation R s Take 6dB. Multiply the numerator coefficient b of the Butterworth filter by... This yields the shaping filter. Finally, unit-variance Gaussian white noise is passed through this shaping filter at a sampling rate f. s Obtain the time series n of broadband modulated noise continuous spectrum components of the simulated ship target. T ={n[1],n[2],…,n[T·f s ]}, where n[i] is the broadband modulation noise continuous spectrum component of sampling point i.

[0021] Step 5: Construct P bandpass filters with their passbands connected end-to-end within the frequency domain of the broadband modulation noise. Then, filter the continuous spectrum components n of the broadband modulation noise of the simulated ship target.T By sequentially passing the P bandpass filters, the time series set of broadband continuous spectrum components in the frequency band is obtained. in, Let be the time series of the broadband continuous spectrum components of the p-th frequency band obtained by passing through the p-th bandpass filter.

[0022] Step 6: The time series calculation method for the envelope modulation spectrum component of the broadband modulation noise of the simulated ship target is as follows:

[0023] The modulation depth of the q-th modulation spectrum in the p-th frequency band at time t is calculated using equation (6).

[0024]

[0025] Among them, f q [t] represents the frequency of the q-th modulation spectrum at time t, and λ q μ q π is the modulation depth coefficient corresponding to this modulation spectrum. p α is the adjustment coefficient for the p-th frequency band, and β and γ are adjustment coefficients related to propeller speed, ship speed and acceleration.

[0026] The p-th frequency band of the simulated ship target at time t is calculated using equation (7), with a sampling rate f. s Obtain the non-uniform broadband modulation noise envelope modulation spectrum component m at sampling point i p [i]:

[0027]

[0028] Where N is the total number of line spectra of the shaft frequency and its harmonics, and f[t] is the propeller shaft frequency at time t. This is the initial phase.

[0029] Step 7: By sampling point i in the p-th frequency band, the continuous spectral component n of the broadband modulation noise of the simulated ship target is obtained. p [i], Envelope modulation spectrum m p [i], the simulation signal sequence s[i] of non-uniform broadband modulation noise under maneuvering state is obtained by superposition calculation using equation (8):

[0030]

[0031] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0032] In existing broadband modulation noise simulation methods, on the one hand, the target is often assumed to be in a stable motion state, and the simulated broadband modulation signal does not change in the time domain; on the other hand, the broadband modulation signal is generally obtained by simply multiplying the broadband continuous spectrum and the envelope modulation spectrum. Traditional broadband modulation noise simulation methods cannot effectively reflect the overall trend of broadband modulation noise caused by target maneuvering. The simulation method adopted in this invention first establishes an energy accumulation model of the simulated target through a physical model of ship navigation, obtaining the relationship between propeller speed and real-time ship speed and acceleration, which conforms to the actual physical meaning; then, in the process of generating the broadband continuous spectrum and the envelope modulation spectrum, parameters related to real-time propeller speed, ship speed, and acceleration are set to effectively reflect the ship's maneuvering characteristics; finally, the modulation depth of different frequencies is dynamically adjusted in the form of frequency bands, and then superimposed for calculation, which is more in line with the actual situation. Attached Figure Description

[0033] Figure 1 This is a flowchart of the present invention;

[0034] Figure 2 The curves showing the changes in propeller speed, speed, and acceleration of the simulated ship target over time during the simulation period in the example;

[0035] Figure 3 The example shows the broadband modulation noise time-domain plot of the simulated ship target at simulation time 1200s.

[0036] Figure 4 The image shows the broadband modulation noise frequency domain diagram of the simulated ship target in the example at simulation time 1200s.

[0037] Figure 5 The image shows the time-domain plot of non-uniform broadband modulation simulation noise of the simulated ship target in the example during the simulation period.

[0038] Figure 6 The image shows the DEMON spectrum of the non-uniform broadband modulation simulation noise of the simulated ship target in the example during the simulation period. Detailed Implementation

[0039] The invention will be further described below with reference to the accompanying drawings.

[0040] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0041] Example:

[0042] (1) Set the basic parameters of the simulated ship target, including its maximum speed v. max It is 20 knots, and the maximum propeller speed R max It has a speed of 300 revolutions per minute and a ship displacement of 2000 tons.

[0043] (2) Set the length T of the simulation signal sequence to 1500, and set the propeller speed R[t] of the simulated ship target at time t according to equation (1):

[0044]

[0045] (3) Set coefficients k1 and k2 to regulate the kinetic energy provided by a certain propeller speed per unit time, and make them satisfy equation (2):

[0046]

[0047] In this example, the coefficients k1 and k2 are set to 1815 and 500, respectively.

[0048] The real-time speed v[t] of the simulated ship target at time t is calculated using equation (3):

[0049]

[0050] The acceleration a[t] of the simulated ship target at time t is calculated using equation (4):

[0051]

[0052] The curves showing the changes in propeller speed, speed, and acceleration of the simulated ship target over time within the simulation period of 0 to 1500 seconds are as follows: Figure 2 As shown.

[0053] (4) The time series n of the frequency-band continuous spectrum component of the broadband modulation noise of the simulated ship target. T Perform the calculation. Calculate the total noise level L above 100Hz using equation (5). S [t]:

[0054]

[0055] The corresponding frequency f of the continuous spectrum component peak of the simulated ship noise is calculated using equation (6). m [t]:

[0056]

[0057] Construct a Butterworth filter for shaping filtering, with the filter parameters set as follows: passband cutoff frequency W pl Take (f) m [t]-30Hz), W ph Take (f) m [t]+30Hz), passband cutoff frequency W sl Take f m [t] / 2, W shTake 8000Hz, passband ripple R p Take 3dB, stopband attenuation R s Take 6dB. Multiply the numerator coefficient b of the Butterworth filter by... This yields the shaping filter. Finally, unit-variance Gaussian white noise is passed through this shaping filter at a sampling rate f. s =16384Hz to obtain the broadband modulation noise continuous spectrum component n of the simulated ship target. T ={n[1],n[2],…,n[T·f s ]}.

[0058] (5) Construct four bandpass filters with passband frequency ranges of 50–2000 Hz, 2000–4000 Hz, 4000–6000 Hz, and 6000–8000 Hz. Calculate the broadband modulation noise continuous spectrum component n of the simulated ship target. T By sequentially passing the data through these four bandpass filters, a set of time series of broadband continuous spectral components in each frequency band can be obtained. in Let be the time series of the broadband continuous spectrum components of the p-th frequency band obtained by passing through the p-th bandpass filter.

[0059] (6) Calculate the time series of the envelope modulation spectrum components of the broadband modulation noise of the simulated ship target. In this example, it is assumed that there are 5 frequencies f in the ship radiated noise. q [t] are respectively and The modulation spectrum. Where the modulation depth coefficient λ of the q-th modulation spectrum. q μ q Configure as shown in Table 1.

[0060] Table 1

[0061] <![CDATA[f q [t]]]> R[t] / 60 R[t] / 30 R[t] / 20 R[t] / 15 2R[t] / 15 <![CDATA[λ q ]]> 0.1 0.1 0.1 0.1 0.1 <![CDATA[μ q ]]> 0.1 0.1 0.15 0.1 0.16

[0062] In this example, the adjustment coefficients related to propeller speed, ship speed, and acceleration are set to α = 0.001, β = 0.01, and γ = 0.5. The adjustment coefficients π for each frequency band are... p Configure as shown in Table 2.

[0063] Table 2

[0064] passband range 50~2000Hz 2000~4000Hz 4000~6000Hz 6000~8000Hz <![CDATA[π p ]]> 0.8 1.2 1.2 1

[0065] The modulation depth of the q-th modulation spectrum in the p-th frequency band at time t is calculated using equation (6).

[0066]

[0067] The p-th frequency band of the simulated ship target at time t is calculated using equation (7), with a sampling rate f. s =16384Hz to obtain the broadband modulation noise envelope modulation spectrum component m of sampling point i p [i]:

[0068]

[0069] Among them, the initial phase All are taken as π / 2.

[0070] (7) By sampling point i in the p-th frequency band, the continuous spectral component n of the broadband modulation noise of the simulated ship target is obtained. p [i], Envelope modulation spectrum m p [i], the simulation signal sequence s[i] of non-uniform broadband modulation noise under maneuvering state is obtained by superposition calculation using equation (8):

[0071]

[0072] The broadband modulated noise signal of the simulated ship target calculated in this example has the following time-domain graph at simulation time t = 1200s: Figure 3 As shown, its frequency domain plot is as follows Figure 4 As shown. The time-frequency diagram of the broadband modulated noise signal during the simulation period is as follows. Figure 5 As shown, its DEMON spectrum is as follows Figure 6 As shown.

[0073] The above provides a detailed description of a simulation method for non-uniform broadband modulation noise in ship maneuvering states provided by embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for simulating non-uniform broadband modulation noise under ship maneuvering conditions, characterized in that: The simulation method includes the following steps: Step 1: Set the basic parameters of the simulated ship target; Step 2: Set the time series of propeller speed of the simulated ship target within the simulation time period; Step 3: Based on the basic parameters of the simulated ship target, establish an energy accumulation model between propeller speed and ship speed, and use the time series of propeller speed of the simulated ship target as input parameters to calculate the time series of ship speed and acceleration within that time period based on the energy accumulation model. Step 4: Based on the propeller speed of the simulated ship target, calculate the total noise level and peak frequency of the broadband continuous spectrum component to obtain the time series of the broadband continuous spectrum component. Step 5: Pass the obtained broadband continuous spectrum components through several bandpass filters to obtain the time series set of broadband continuous spectrum components divided by frequency band; Step 6: Based on the propeller speed, ship speed, and acceleration of the simulated ship target, calculate the modulation depth of the envelope modulation spectrum components in each frequency band to obtain the time series of the non-uniform envelope modulation spectrum components in each frequency band. Step 7: Based on the broadband continuous spectrum component and envelope modulation spectrum component of the simulated broadband modulation noise, calculate the simulated signal sequence of non-uniform broadband modulation noise under the maneuvering state by frequency band division.

2. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In the first step, the basic parameters of the simulated ship target are set, including its maximum speed v. max Maximum propeller speed R max And the ship's displacement (m).

3. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In the second step, the time series R of the propeller speed of the simulated ship target within the simulation period is set. T = {R[1], R[2], ..., R[T]}, where the propeller speed R[t] at any time t is less than the maximum speed R. max The value is a non-negative number, with the unit being revolutions per minute (rpm). t is the simulation time number, and T is the length of the simulation signal sequence.

4. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In the third step, an energy accumulation model of the simulated target is established based on the physical model of the ship's navigation, obtaining the relationship between propeller speed and the ship's real-time speed and acceleration. This allows the calculation of the time series R of the simulated ship's propeller speed. T Obtain the time series of real-time airspeed v T ={v[1], v[2], ..., v[T]} and the time series of acceleration a T ={a[1], a[2], ..., a[T]}, where v[t] and a[t] are the real-time speed and acceleration at time t, respectively, as follows: (4.1) Calculate the real-time speed v[t] of the simulated ship target at time t using equation (1): Wherein, coefficients k1 and k2 are positive numbers, used to adjust the kinetic energy provided by a certain propeller speed per unit time, and the relationship between coefficients k1 and k2 satisfies equation (2): (4.2) When the simulation time interval is t0, the acceleration a[t] of the simulated ship target at time t is calculated by equation (3):

5. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In the fourth step, the time series n of the frequency-band continuous spectral components of the broadband modulation noise of the simulated ship target is calculated. T The calculation method is as follows: (5.1) Calculate the total noise level L above 100Hz using equation (4). S [t]: (5.2) The corresponding frequency f of the continuous spectrum component peak of the simulated ship noise is calculated by equation (5). m [t]: (5.3) Construct a Butterworth filter for shaping filtering. The filter parameters are set as follows: passband cutoff frequency W pl Take f m [t]-30Hz, W ph Take f m [t]+30Hz, passband cutoff frequency W sl Take f m [t] / 2, W sh Take 8000Hz, passband ripple R p Take 3dB, stopband attenuation R s Take 6dB, and multiply the numerator coefficient b of the Butterworth filter by... This yields a shaping filter, which is then used to pass unit variance Gaussian white noise at a sampling rate f. s Obtain the time series n of broadband modulated noise continuous spectrum components of the simulated ship target. T ={n[1],n[2],...,n[T·f s ]}, where n[i] is the broadband modulation noise continuous spectrum component of sampling point i.

6. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In the fifth step, within the frequency domain of the broadband modulation noise, P bandpass filters with their passbands connected end-to-end are constructed to filter the continuous spectrum components n of the broadband modulation noise of the simulated ship target. T By sequentially passing the P bandpass filters, the time series set of broadband continuous spectrum components in the frequency band is obtained. in, Let p be the time series of the broadband continuous spectrum component of the p-th frequency band obtained by passing through the p-th bandpass filter, where p ranges from 1 to p.

7. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 1, characterized in that: In step six, the time series calculation method for the envelope modulation spectrum component of the broadband modulation noise of the simulated ship target is as follows: (6.1) Calculate the modulation depth of the q-th modulation spectrum in the p-th frequency band at time t using equation (6). Among them, f q [t] represents the frequency of the q-th modulation spectrum at time t, and λ q μ q π is the modulation depth coefficient corresponding to this modulation spectrum. p Let be the adjustment coefficient for the p-th frequency band, and α, β, and γ be adjustment coefficients related to propeller speed, ship speed, and acceleration. (6.2) The p-th frequency band of the simulated ship target at time t is calculated using equation (7), with a sampling rate f. s Obtain the non-uniform broadband modulation noise envelope modulation spectrum component m at sampling point i p [i]: Where N is the total number of line spectra of the shaft frequency and its harmonics, and f[t] is the propeller shaft frequency at time t. This is the initial phase.

8. The simulation method for non-uniform broadband modulation noise under ship maneuvering conditions according to claim 7, characterized in that: In step seven, the continuous spectral component n of the broadband modulation noise of the simulated ship target at sampling point i in the p-th frequency band is obtained. p [i], Envelope modulation spectrum m p [i], the simulation signal sequence s[i] of non-uniform broadband modulation noise under maneuvering state is obtained by superposition calculation using equation (8):

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