CN106971706A - Noise initiative control method based on broad sense class Lorenz System - Google Patents

Abstract

The invention provides a kind of noise initiative control method based on broad sense class Lorenz System, this method is directed to the suppression problem of ship-radiated noise acoustic wave energy, Systems with Time Delay Feedback controlled quentity controlled variable and external excitation are added using classical Lorenz System and in this system, the control effect to noise is obtained with the determination methods of chaotic dynamics.To the broad sense class Lorenz System after deformation, the dynamics for having observed its output is programmed using Matlab, including phase path figure, bifurcation graphs and Liapunov exponent figure, system output is given in the external excitation magnitude parameters, frequency parameter and corresponding parameter area of periodic motion, quasi-periodic motion or chaotic motion state, provided using spectrum curve and apply noise source energy value and energy change value before and after active sound source under fixed frequency, specify that the inhibition of the different lower noises of sound sources effect.

Description

Noise initiative control method based on broad sense class Lorenz System

Technical field

The present invention relates to noise management technique, more particularly to a kind of noise impedance based on broad sense class Lorenz System Method.

Background technology

Naval vessel Sound stealth is always the problem of ocean military field is paid close attention to the most, and ship-radiated noise is enemy's detection target Main observation method, the noise is mainly derived from mechanical noise, propulsion system noise and hydrodynamic noise etc..Naval vessel radiation is made an uproar Sound is mainly low-frequency noise, and low-frequency noise wavelength is longer, originally using buoyant raft, flexible hose, silencer, pump spray propulsion, electric power The passive control methods such as propulsion, noise reduction by bubble screen, sound eliminating tile carry out vibration and noise reducing, are deposited for low-frequency noise using passive noise control In obvious deficiency, the proposition of 1930s active noise controlling method solves this problem.Numerous studies start master Moving noise control method is applied to the Sound stealth on naval vessel, and various active absorbing technologies and vibration isolation technique arise at the historic moment.Naval vessel is radiated Noise is the random signal of typical nonlinear and nonstationary, therefore many traditional analysis methods are when such signal is handled All will be by great limitation.With the development of chaotic dynamics, researcher has found that ship-radiated noise has chaos phenomenon, Therefore people start with Chaotic Analysis Method and ship-radiated noise problem are studied.Study at present by chaos power Method is used to analyze ship noise problem, such as detects low signal-to-noise ratio ship signaling using chaotic oscillator theory；Non-linear Phase space reconfiguration is carried out on the basis of partial projection filtering, checking can realize target identification by natural measure, correlation dimension；It is logical Cross extraction correlation dimension this chaotic characteristic and realize ship seakeeping.

However, the suppression of prior art still immature currently for the acoustic energy suppression technology of ships radiated noise signal Effect is poor.

The content of the invention

The brief overview on the present invention is given below, to provide on the basic of certain aspects of the invention Understand.It should be appreciated that this general introduction is not the exhaustive general introduction on the present invention.It is not intended to determine the pass of the present invention Key or pith, nor is it intended to limit the scope of the present invention.Its purpose only provides some concepts in simplified form, In this, as the preamble in greater detail discussed later.

In consideration of it, the invention provides a kind of noise initiative control method based on broad sense class Lorenz System, with least Solve the problem of existing acoustic energy suppression technology for ships radiated noise signal is still immature, inhibition is poor.

According to an aspect of the invention, there is provided a kind of noise impedance side based on broad sense class Lorenz System Method, being somebody's turn to do the noise initiative control method based on broad sense class Lorenz System includes：Step 1: providing speed using the first equation group The expansion in field and temperature field and incompressibility, wherein, first equation group is：

Wherein, u=u (x, y, z) represents fluid velocity, and x represents speed mould, and y represents temperature mould, and z represents thermograde Mould, temperature field is represented by T=T (x, y, z)；ε is thermal coefficient of expansion, and g is acceleration of gravity, and ρ is fluid density, and P is fluid pressure The field of force, ν is fluid viscosity coefficient, and k is the coefficient of heat conduction of fluid；

Step 2: by introducing scalar equation ψ (x, z, t) and the temperature field T=T (x, y, z) of fluid being converted into θ (x, z, t), to obtain second equation group, ψ (x, z, t) gradient is fluid velocity；Wherein, the second equation group is：

Step 3: ψ (x, z, t) and θ (x, z, t) Fourier expansion form are expressed as into formula one and formula two, to obtain the 3rd Equation group, wherein, formula one isFormula two is X (t), Y (t) and Z (t) are time t function, C₁、C₂, a and b be Fourier integral constant, a=π/L, b=π/H, L is x directions Width, H is the height in z directions；Third party's journey group is：

Step 4: using boundary condition cos (2a₂Z)=cos (π)=- 1, and makeν(a₁ ²+ a₂ ²)=σ,k(a₁ ²+a₂ ²)=1, C₁a₁a₂=Isosorbide-5-Nitrae ka₂ ²=b, to obtain the 4th equation group；Wherein, described Four equation groups are first-order ordinary differential equation system, and its expression formula is：

Wherein, σ is Prandtl number, and r is Rayleigh number, and b is the parameter relevant with container size shape；

Step 5: representing the chaos system of itself under water using the 4th equation group；

Step 6: by added in the 4th equation group amplitude be A, frequency be f trigonometric function noise signal come The 5th equation group is obtained, to represent noisy chaos system；Wherein, the 5th equation group is：

Step 7: setting σ=10, b=8/3, r=25, and x, y and z are initialized, time step is 0.5；

Step 8: using phase space reconfiguration, fork and Liapunov exponent method, being realized to the noisy chaos system Chaos controlling.

Further, the noise initiative control method also includes：Time delay is added in the noisy chaos system Feedback module, to obtain the chaos system after increase Systems with Time Delay Feedback；Wherein, the expression formula of the time delay feedback module is F (t)=- K [u (t- τ)-u (t)], τ ＞ 0 represent time lag, and K is adjustable feedback oscillator vector；After the increase Systems with Time Delay Feedback Chaos system is：

Further, the noise initiative control method also includes：In chaos system after the increase Systems with Time Delay Feedback Addition amplitude is A₁, frequency be f₁The first default external excitation, to obtain Systems with Time Delay Feedback and single external excitation chaos system；When described It is stagnant feedback with list external excitation chaos system be：

Further, the noise initiative control method also includes：In chaos system after the increase Systems with Time Delay Feedback The default external excitation of addition first and the second default external excitation, to obtain Systems with Time Delay Feedback and many external excitation chaos systems, described first The amplitude of default external excitation is A₁, frequency be f₁, and the amplitude of the described second default external excitation is A₂, frequency be f₂；The time lag Feed back and be with many external excitation chaos systems：

The noise initiative control method based on broad sense class Lorenz System of the present invention, believes mainly for ship-radiated noise Number acoustic energy suppress, be based on Lorenz System add delay active noise controlling form, using phasor, bifurcation graphs and Liapunov exponent figure, provides the rule and change curve of sound wave different parameters after chaos system.Inquire into different external excitations In the case of system chaotic characteristic changing rule, it is and main by its energy variation of frequency spectrum map analysis, and then realize to sound wave The control of energy, to reach Noise measarement and provide new theories integration and Technical Reference to ship stealth.

In the noise initiative control method of the present invention, for the suppression problem of ship-radiated noise acoustic wave energy, use Classical Lorenz System simultaneously adds Systems with Time Delay Feedback controlled quentity controlled variable and external excitation (sound source acoustic source), fortune in this system Noise measarement effect is studied with the determination methods of chaotic dynamics.To the broad sense class Lorenz System after deformation, profit Programmed with Matlab and observed its dynamics exported, including phase path figure, bifurcation graphs and Liapunov exponent figure, give Gone out system output in the external excitation magnitude parameters of periodic motion, quasi-periodic motion or chaotic motion state, frequency parameter and Corresponding parameter area, the noise source energy value and energy applied before and after active sound source under fixed frequency is provided using spectrum curve Changing value, specify that the inhibition of the different lower noises of sound source effect.Research shows：Noise suppressed when adding low-frequency range external excitation Effect is best, while it is that 3 frequencies are 400Hz and amplitude is amount of noise reduction when 10 frequencies are 350Hz external excitations to add amplitude Value is maximum, and the external signal and feedback control module of multiple different frequencies are radiated to naval vessel and can realize the frequency spectrum to noise jointly Move, reach the effect of noise suppressed.

Therefore, the above-mentioned noise initiative control method based on broad sense class Lorenz System of the invention, it is made an uproar using active Acoustic control method can preferably control low-frequency noise, and ship-radiated noise has chaos phenomenon, and chaotic dynamics method is used for Analysis ship noise problem has Research Significance.

By the detailed description below in conjunction with accompanying drawing to highly preferred embodiment of the present invention, these and other of the invention is excellent Point will be apparent from.

Brief description of the drawings

The present invention can be by reference to being better understood, wherein in institute below in association with the description given by accompanying drawing Have and used same or analogous reference in accompanying drawing to represent same or similar part.The accompanying drawing is together with following Describe the part for including in this manual and being formed this specification together in detail, and for this is further illustrated The preferred embodiment of invention and the principle and advantage for explaining the present invention.In the accompanying drawings：

Fig. 1 is one of the noise initiative control method based on broad sense class Lorenz System for schematically showing the present invention The flow chart of exemplary process；

Fig. 2 is the bifurcation graphs of Noise Lorenz System under different amplitude A；

Fig. 3 A-3H are the phase path figure and Liapunov exponent figure of system output；

Fig. 4 is the bifurcation graphs of time lag system under different delay τ；

Fig. 5 A-5H are the phase path figure and Liapunov exponent figure of broad sense class Lorenz System；

Fig. 6 A-6D are the spectrograms of different f1 time lag systems；And

Fig. 7 A-7D are the spectrograms of different A1 time lag systems.

It will be appreciated by those skilled in the art that element in accompanying drawing is just for the sake of showing for the sake of simple and clear, And be not necessarily drawn to scale.For example, the size of some elements may be exaggerated relative to other elements in accompanying drawing, with Just it is favorably improved the understanding to the embodiment of the present invention.

Embodiment

The one exemplary embodiment of the present invention is described hereinafter in connection with accompanying drawing.For clarity and conciseness, All features of actual embodiment are not described in the description.It should be understood, however, that developing any this actual implementation Many decisions specific to embodiment must be made during example, to realize the objectives of developer, for example, symbol Those restrictive conditions related to system and business are closed, and these restrictive conditions may have with the difference of embodiment Changed.In addition, it also should be appreciated that, although development is likely to be extremely complex and time-consuming, but to having benefited from the disclosure For those skilled in the art of content, this development is only routine task.

Herein, in addition it is also necessary to which explanation is a bit, in order to avoid having obscured the present invention because of unnecessary details, in the accompanying drawings It illustrate only and according to the closely related apparatus structure of the solution of the present invention and/or process step, and eliminate and the present invention The little other details of relation.

The processing that Fig. 1 gives the noise initiative control method based on broad sense class Lorenz System of the present invention is shown Example.As shown in figure 1, after this method starts, step one is first carried out.

In step one, velocity field and expansion and the incompressibility in temperature field are provided using the first equation group, wherein, First equation group is：

Wherein, u=u (x, y, z) represents fluid velocity, and x represents speed mould, and y represents temperature mould, and z represents thermograde Mould, temperature field is represented by T=T (x, y, z)；ε is thermal coefficient of expansion, and g is acceleration of gravity, and ρ is fluid density, and P is fluid pressure The field of force, ν is fluid viscosity coefficient, and k is the coefficient of heat conduction of fluid.Then, step 2 is performed.

In step 2, by introducing scalar equation ψ (x, z, t) and changing the temperature field T=T (x, y, z) of fluid For θ (x, z, t), to obtain second equation group, ψ (x, z, t) gradient is fluid velocity；Wherein, second equation group is：

Then, in step 3, ψ (x, z, t) and θ (x, z, t) Fourier expansion form are expressed as formula One and formula two, to obtain third party's journey group, wherein, formula one isFormula two isX (t), Y (t) and Z (t) are time t function, C₁、C₂, a and B be Fourier integral constant, a=π/L, b=π/H, L is the width in x directions, and H is the height in z directions；Third party's journey group is：

Then, in step 4, using boundary condition cos (2a₂Z)=cos (π)=- 1, and make ν(a₁ ²+a₂ ²)=σ,k(a₁ ²+a₂ ²)=1, C₁a₁a₂=Isosorbide-5-Nitrae ka₂ ²=b, to obtain the 4th equation group；Wherein, 4th equation group is first-order ordinary differential equation system, and its expression formula is：

Wherein, σ is Prandtl number, and r is Rayleigh number, and b is the parameter relevant with container size shape.

Then, in step 5, the chaos system of itself under water is represented using the 4th equation group.

So, it is that the trigonometric function noise that A, frequency are f is believed by adding amplitude in the 4th equation group in step 6 Number the 5th equation group is obtained, to represent noisy chaos system；Wherein, the 5th equation group is：

Then, in step 7, σ=10, b=8/3, r=25 are set, and x, y and z are initialized, time step For 0.5.

So, in step 8, phase space reconfiguration is realized by adding feedback control with external excitation, to noisy chaos system System realizes chaos controlling, and carries out qualitative and quantitative analysis using fork and Liapunov exponent method.

Wherein, phase space reconfiguration is Nonlinear Time Series Analysis, the basis of processing, and the time series generally measured is all Scalar time sequence, can not show the multidimensional phase space of dynamical system.Therefore need to deploy this multidimensional structure, construct one The auxiliary phase space of equal value with motive power system, this method is phase space reconfiguration.Takens embedding theorems point out that any m is tieed up Hyperplane, can be differentiated homeomorphically, be glossily embedded into equivalence corresponding dimension space in, reconfiguration system phase space need to only be examined Consider one-component, new sequence vector is found by the observation on the delay point of some fixations.Takens embedding theorems correspondence The method of phase space reconstruction be the embedded Reconstruction Method of delay, it is important to find suitable τ, form embedding after being delayed to scalar measurement value Enter the vector in space, reconstruct forms new space.

Fork is a kind of typical phenomenon of nonlinear system, and the change of systematic parameter amount causes as the number of equalization point and steady The change of qualitative so matter of some systematic functions.Unstability is the physical premises that fork occurs, and its essence is that Parameters variation causes System Jacobian matrix characteristic value hyperbolicity be destroyed, so as to cause the change of system architecture stability.Doubling time point It is three kinds of major ways that system leads to chaos that trouble, fork paracycle and paroxysmal, which lead to chaos, and therefore, Bifurcation Characteristics can be used In the motion state residing for judgement system.

In addition, the motion state for pointing out system that Liapunov exponent figure can be quantified, Liapunov exponent is used for Portray under conditions of there is small sample perturbations or initial condition fine difference, the transmitting case of system adjacent orbit.Work as Li Yapunuo Husband's index is just, i.e. during λ ＞ 0, adjacent orbit is gradually disengaged, and system is unstable, so as to represent that system is in chaos state；Work as Lee Ya Punuofu indexes are negative, i.e. during λ ＜ 0, represent track local contraction, system is stable, corresponding to periodic motion；Work as Li Ya Pu Nuofu indexes are 0, represent that system motion is in the critical condition of cycle and chaotic motion.

According to an implementation, noise initiative control method can also include：The time is added in noisy chaos system Delay Feedback module, to obtain the chaos system after increase Systems with Time Delay Feedback；Wherein, the expression formula of time delay feedback module is F (t)=- K [u (t- τ)-u (t)], τ ＞ 0 represent time lag, and K is adjustable feedback oscillator vector；Increase the chaos after Systems with Time Delay Feedback System is：

According to an implementation, noise initiative control method can also include：Chaos system after increase Systems with Time Delay Feedback It is A that amplitude is added in system₁, frequency be f₁The first default external excitation, to obtain Systems with Time Delay Feedback and single external excitation chaos system；When It is stagnant feedback with list external excitation chaos system be：

According to an implementation, noise initiative control method can also include：Chaos system after increase Systems with Time Delay Feedback The default external excitation of addition first and the second default external excitation in system, to obtain Systems with Time Delay Feedback and many external excitation chaos systems, first The amplitude of default external excitation is A₁, frequency be f₁, and the amplitude of the second default external excitation is A₂, frequency be f₂；Systems with Time Delay Feedback with it is many External excitation chaos system is：

Preferred embodiment

Dynamical Characteristics under line spectrum effect

The present embodiment regard the 4th equation group as the chaos system of itself under water.The frequency spectrum of submarine radiated noise sound source level is The ability of random noise part in the mixed spectrum being formed by stacking by broadband continuous spectrum and single-frequency line spectrum, continuous spectrum reflection noise signal Distribution, substantial amounts of measurement analysis shows, continuous spectrum has a peak value, and the upper limit of its spectrum peak frequency is different because of the type on naval vessel, but all Between 200Hz-400Hz, it occupies most energy of radiated noise, when more than this upper frequency limit, becomes in decay Gesture, decay about 6d B per octave.Cyclic component in single-frequency line spectrum reflection noise signal, concentrates on below 1k Hz frequencies Section, mainly as caused by the mechanical noise, propeller blade resonance line spectrum and blade velocity line spectrum and hydrodynamic force that move repeatedly Resonance is produced.Submarine is in lowsteaming, and mechanical noise is Main Noise Sources, in high speed operation, and propeller noise is its master Noise source is wanted, propeller cavitation noise is often the main component of submarine noise high band, in summary, submarine radiated noise frequency Rate scope is about 100Hz-1k Hz, while depending on the species of the headway of submarine, submerged depth and submarine^[15].This reality Example one trigonometric function of addition is applied to be studied as noise signal.Addition amplitude is A, after frequency is f trigonometric function noise System form is as shown in the 5th equation group.

It can substantially understand system bifurcation graphs such as figure after system motion variation tendency and scope, addition noise by bifurcation graphs Shown in 2, basic parameter is respectively set as σ=10, b=8/3, r=25, and primary condition is set to y0=(0.01,0.01,0.01) (i.e. the initial value of x, y and z are 0.01), time step is 0.5.In fig. 2, abscissa is A, ordinate X_maxRepresent that X is maximum Value.

From bifurcation graphs 2, system is in the cycle to chaos again to the continuous alternate process in cycle, when parameter A is in System is in a periodic state when near 250, and subsequently into chaos state, when amplitude is in 300 or so, system starts to occur Substantially diverge, system starts to be again transformed into periodic motion, when parameter A is near 320, fork occurs again.

In order to more intuitively study system motion state, the present embodiment provide phase path figure under four amplitude and specifics and Liapunov exponent figure.When simulation process selection radiated noise amplitude is respectively 250,298,320 and 332, corresponding phase rail Mark figure and largest Lyapunov exponent figure are as shown in Fig. 3 A- Fig. 3 H.

From phase path Fig. 3 A-3H, by Fig. 3 A this it appears that system is in a periodic state when amplitude is 250, Largest Lyapunov exponent also illustrates that system is in periodic state less than zero in Fig. 3 B；System is in when Fig. 3 C amplitudes are 298 Periodic state or quasi-periodicity state, largest Lyapunov exponent is equal to zero explanation system and transported in the cycle with chaos in Fig. 3 D Dynamic critical condition；By Fig. 3 E this it appears that system is in maximum Li Yapu in three periodic states, Fig. 3 F when amplitude is 320 Promise husband index also illustrates that system is in periodic state less than zero；By Fig. 3 G this it appears that system is in mixed when amplitude is 332 Largest Lyapunov exponent also illustrates that system is in chaos state more than zero in ignorant state, Fig. 3 H.Pass through phasor and Li Yapu The state change that promise husband's index map demonstrates system is consistent with bifurcation graphs.

System output dynamical property analysis under delayed-action

Noise measarement is carried out using the method for active noise controlling, time delay is added first in noisy chaos system anti- Module is presented, the dynamics of system can be changed using system mode Systems with Time Delay Feedback, system is produced complicated Nonlinear Dynamic Mechanical behavior, including periodic motion, quasi-periodic motion, chaotic motion etc..Not only can be with control chaotic system using Systems with Time Delay Feedback To periodic motion, can also revertive control system be allowed to produce more complicated chaotic motion.One negative-feedback of selection addition herein, The form of expression is：F (t)=- K [u (t- τ)-u (t)].

Wherein τ ＞ 0 represent time lag, and K is adjustable feedback oscillator vector, increase new system after Systems with Time Delay Feedback and are：

The situation of change of system motion state after increase Systems with Time Delay Feedback, basic parameter when doing bifurcation graphs are observed by bifurcation graphs σ=10, b=8/3, r=25 are respectively set as, primary condition is set to y0=(0.01,0.01,0.01,0.01), time step For 0.5, preset parameter k is 5, changes bifurcation graphs obtained by time lag τ as shown in Figure 4.

System fork is more obvious after bifurcation graphs 4, addition control, and chaos state obtains certain control.

System output dynamics under external excitation effect

In order to reach more preferable chaos controlling effect, on the basis of containing feedback module appropriate external excitation is added again and entered One step realizes chaos controlling.Addition amplitude is A₁, frequency is f₁External excitation after obtain new system and be：

Chaos controlling is realized by Systems with Time Delay Feedback and external excitation jointly, phase space reconfiguration is carried out.Provide separately below under water Itself chaos system, be system after influence of noise that 330 frequencies are 1kHz by amplitude, join delay for 0.13 Systems with Time Delay Feedback And amplitude be 1.35 frequencies be when system and external excitation frequency conversion are 400Hz after 100Hz external excitations the phase path figure of system with Liapunov exponent.Experimental result is as shown in Fig. 5 A- Fig. 5 H.

Fig. 5 A- Fig. 5 H are the phase path figure and Liapunov exponent figure of broad sense class Lorenz System.

Largest Lyapunov exponent is equal in Fig. 5 B, 5D, 5F and 5H Liapunov exponent curve, every width figure More than zero, there is assassin to judge that four kinds of states are in chaos state.Fig. 5 A are the chaos attractor under noiseless and control condition； Find out that significant change occurs for system chaos state under influence of noise by Fig. 5 C, it is amplitude 330, frequency 1kHz now to choose noise Cosine signal；Fig. 5 E can be seen that addition feedback control and be 1.35 to naval vessel radiation amplitude, and frequency swashs for the outer of 100Hz When encouraging control signal, chaotic systems state is controlled close to the original chaos state of water body；Fig. 5 G increase to control signal frequency 400Hz, it can be seen that now chaos state is more nearly reset condition, substantially it can be seen that chaos controlling diverges with Fig. 2 to Fig. 4 The situation of change that chart reveals is basically identical.

Different frequency external excitation Noise measarement effect

In order to verify denoising effect, the present embodiment mainly provides spectrogram, by the change for observing acoustic wave energy size at 1Hz Change, the different external excitation form denoising effects of quantitative checking.Fig. 6 A-6D provide frame of reference, add system after noise, add respectively The fashionable amplitude that extends to is 1, and frequency is 800 and frequency is spectrogram in the case of 400 external excitations, and sampling frequency is 100Hz, is passed through Experimental verification delay parameter is chosen for 0.13.In order to inquire into the relation of Noise measarement effect and external excitation frequency, table 1 provides multigroup The data of different frequency acoustic wave energy reduction amount.

It can be seen from Fig. 6 A-6D, correspondence acoustic wave energy is respectively 49,53.5,35 and 30dB at 1Hz, is as a result substantially pointed out Add acoustic wave energy after noise to improve, acoustic wave energy after external excitation controlled quentity controlled variable is extended to during addition substantially to be reduced, it is known that this method Noise can be suppressed.Changing external excitation frequency makes it be respectively at low-frequency range and high band, and system is not with adding control Noisy system is provided by table 1, table 2 respectively compared to the reduction amount of acoustic wave energy.

The low-frequency range of table 1 difference f1 acoustic wave energy variable quantities

f1(Hz)	800	600	400	200	100	10	1
								ΔE(dB)	18.5	22.5	23.5	19.5	18.5	11	10

The high band of table 2 difference f1 acoustic wave energy variable quantities

f1(Hz)	3k	6.5k	8k	8.5k	10k	80k	800k
								ΔE(dB)	11	10.5	13.5	10.5	10	13.5	11.5

It can substantially be obtained by the data comparison of 1 table of table 2, than acoustic wave energy in the case of high band when added external excitation is in low-frequency range Decreasing value is big, illustrates that control frequency should be chosen in low frequency segment limit, noise reduction is more preferable.When frequency is 10Hz and 1Hz in table 1 Energy reduction amount understand, when frequency is too small, noise suppression effect is also substantially deteriorated, in the present embodiment choose external excitation frequency It is best for 400Hz noise suppression effects.

Different amplitude external excitation Noise measarement effects

External excitation frequency is fixed on 400Hz, other systems parameter constant, sampling frequency is 100Hz, and delay parameter is chosen For 0.13, frame of reference and add the spectrogram of system after noise and provided by Fig. 7 A-7B, Fig. 7 C-7D, which provide two kinds, has representative Property amplitude be 1 and 2 spectrogram.The data of multigroup different amplitude acoustic wave energy reduction amounts are provided by table 3.

It can be seen from Fig. 7 A-7D, correspondence acoustic wave energy is respectively 49,53.5,40 and 26.6dB at 1Hz, as a result points out width Noise suppression effect weakens when value increases to 2, but when amplitude takes 3, acoustic wave energy reduction amount is 26.9dB, and noise reduction is more It is good.

The difference A1 acoustic wave energy variable quantities of table 3

A1	0.5	1	1.5	2	3	3.1	4
								ΔP	12.5	23.5	16	13.5	26.9	18.5	23.5

As shown in Table 3, acoustic wave energy reduction is more sensitive for external excitation amplitude, and the minor variations of amplitude are for noise suppressed Effect tool has a significant impact, and data can be seen that acoustic wave energy reduction amount is maximum when amplitude takes 3 in table 3, now noise suppressed Effect is best.

Multiple external excitation Noise measarement effects

The different external excitation of two amplitude frequencies is added, setting up new equation is：

The amplitude and frequency for changing newly-increased trigonometric function external excitation obtain acoustic wave energy reduction amount, and specific data are by table 4, table 5 provide.

The difference f2 acoustic wave energy variable quantities of table 4

f2	800	600	350	300	200	100	1
								ΔP	13.5	22.5	29.5	25.5	26	19.5	15.5

The difference A2 acoustic wave energy variable quantities of table 5

A1	1.5	2	2.5	3	4	5	10
								ΔP	17.5	19.5	9.5	19.5	23	26.5	39.5

From table 3, table 4, it is that 350Hz amplitudes are to add frequency on the basis of frequency is the external excitation that 400Hz amplitudes are 3 Acoustic wave energy reduction amount is 39.5dB to the maximum during 10 external excitation, illustrates that two trigonometric function collective effects can be with more than 26.9dB Reach more preferable effect.To reach noise suppression effect, selecting frequency is less than the external excitation of noise frequency, adds two triangle letters When number is as external excitation, the frequency of second trigonometric function is close and less than Section 1 frequency.

Joined by the way that different external excitations to phase path figure, bifurcation graphs and largest Lyapunov exponent map analysis, can be chosen Number threshold value controls system in cycle, quasi-periodicity and chaos state；External excitation and Systems with Time Delay Feedback by appropriate format are controlled jointly System can be by the chaotic systems state control after influence of noise to known chaos state；Also sent out by the quantitative analysis of spectrogram Now add Systems with Time Delay Feedback and noise signal can be made to occur frequency spectrum shift naval vessel radiation low-frequency range external excitation signal, reach noise The effect of suppression.Add two different frequency external excitations, such as A₁=3, f₁=400, A₂=10, f₂=350 is single outer more sharp than adding Encourage that noise suppression effect is good, this solution to development ship-radiated noise Denoising Problems has important theory and engineering significance.

Although describing the present invention according to the embodiment of limited quantity, above description, the art are benefited from It is interior it is clear for the skilled person that in the scope of the present invention thus described, it can be envisaged that other embodiments.Additionally, it should be noted that The language that is used in this specification primarily to readable and teaching purpose and select, rather than in order to explain or limit Determine subject of the present invention and select.Therefore, in the case of without departing from the scope and spirit of the appended claims, for this Many modifications and changes will be apparent from for the those of ordinary skill of technical field.For the scope of the present invention, to this The done disclosure of invention is illustrative and not restrictive, and it is intended that the scope of the present invention be defined by the claims appended hereto.

Claims (4)

1. the noise initiative control method based on broad sense class Lorenz System, it is characterised in that the noise initiative control method Including：

Step 1: velocity field and expansion and the incompressibility in temperature field are provided using the first equation group, wherein, described first Equation group is：

$\left\{\begin{array}{c}(\frac{\∂}{\∂t}+u\·\▿)u=\mathrm{\ϵ}g\mathrm{\Δ}T-\frac{1}{\mathrm{\ρ}}\▿P+v{\▿}^{2}u\\ (\frac{\∂}{\∂t}+u\·\▿)T=k{\▿}^{2}T\\ \▿\·u=0\end{array}\right.,$

Wherein, u=u (x, y, z) represents fluid velocity, and x represents speed mould, and y represents temperature mould, and z represents thermograde mould, temperature Field is spent to be represented by T=T (x, y, z)；ε is thermal coefficient of expansion, and g is acceleration of gravity, and ρ is fluid density, and P is Fluid Pressure Field, ν For fluid viscosity coefficient, k is the coefficient of heat conduction of fluid；

Step 2: by introduce scalar equation ψ (x, z, t) and by the temperature field T=T (x, y, z) of fluid be converted to θ (x, z, T), second equation group is obtained, ψ (x, z, t) gradient is fluid velocity；Wherein, the second equation group is：

$\left\{\begin{array}{c}\frac{\∂}{\∂t}{\▿}^2\mathrm{\ψ}=-\frac{\∂(\mathrm{\ψ},{\▿}^2\mathrm{\ψ})}{\∂(x,z)}+\mathrm{\ν}{\▿}^4\mathrm{\ψ}+\mathrm{\ϵ}g\frac{\∂\mathrm{\θ}}{\∂x}\\ \frac{\∂}{\∂t}\mathrm{\θ}=-\frac{\∂(\mathrm{\ψ},\mathrm{\θ})}{\∂(x,z)}+\frac{\mathrm{\Δ}T}{H}\frac{\∂\mathrm{\ψ}}{\∂x}+k{\▿}^2\mathrm{\θ}\\ {\▿}^2\mathrm{\ψ}=0\end{array}\right.;$

Step 3: ψ (x, z, t) and θ (x, z, t) Fourier expansion form are expressed as into formula one and formula two, to obtain the 3rd Equation group, wherein, formula one isFormula two is X (t), Y (t) and Z (t) are time t function, C₁、C₂, a and b be Fourier integral constant, a=π/L, b=π/H, L is x directions Width, H is the height in z directions；Third party's journey group is：

$\left\{\begin{array}{c}{X}^{\′}\left(t\right)=-\mathrm{\ν}({a_1}^2+{a_2}^2)X\left(t\right)+\mathrm{\ϵ}g\frac{C_2}{C_1}\frac{a_1}{{a_1}^2+{a_2}^2}Y\left(t\right)\\ Y^{\′}\left(t\right)=C_1{a}_1{a}_2\cos \left(2a_{2}z\right)X\left(t\right)Z\left(t\right)+\frac{\mathrm{\Δ}T}{H}\frac{C_1}{C_2}{a}_{1}X\left(t\right)-k({a_1}^2+{a_2}^2)Y\left(t\right)\\ Z^{\′}\left(t\right)=C_1{a}_1{a}_{2}X\left(t\right)Y\left(t\right)-4{{\mathrm{ka}}_2}^{2}Z\left(t\right)\end{array}\right.;$

Step 4: using boundary condition cos (2a₂Z)=cos (π)=- 1, and makeν(a₁ ²+a₂ ²) =σ,k(a₁ ²+a₂ ²)=1, C₁a₁a₂=Isosorbide-5-Nitrae ka₂ ²=b, to obtain the 4th equation group；Wherein, the described 4th Equation group is first-order ordinary differential equation system, and its expression formula is：

$\left\{\begin{array}{c}\stackrel{\·}{x}=-\mathrm{\σ}x+\mathrm{\σ}y\\ \stackrel{\·}{y}=rx-y-xz\\ \stackrel{\·}{z}=-bz+xy\end{array}\right.$

Wherein, σ is Prandtl number, and r is Rayleigh number, and b is the parameter relevant with container size shape；

Step 5: representing the chaos system of itself under water using the 4th equation group；

Step 6: being that the trigonometric function noise signal that A, frequency are f is obtained by adding in the 4th equation group amplitude 5th equation group, to represent noisy chaos system；Wherein, the 5th equation group is：

$\left\{\begin{array}{c}\stackrel{\·}{x}=-\mathrm{\σ}x+\mathrm{\σ}y+Acos2\mathrm{\π}ft\\ \stackrel{\·}{y}=rx-y-xz\\ \stackrel{\·}{z}=-bz+xy\end{array}\right.;$

Step 7: setting σ=10, b=8/3, r=25, and x, y and z are initialized, time step is 0.5；

Step 8: using phase space reconfiguration, fork and Liapunov exponent method, chaos is realized to the noisy chaos system Control.

2. the noise initiative control method according to claim 1 based on broad sense class Lorenz System, it is characterised in that institute Stating noise initiative control method also includes：

Time delay feedback module is added in the noisy chaos system, to obtain the chaos system after increase Systems with Time Delay Feedback；

Wherein, the expression formula of the time delay feedback module is F (t)=- K [u (t- τ)-u (t)], and τ ＞ 0 represent time lag, and K is Adjustable feedback oscillator vector；

Chaos system after the increase Systems with Time Delay Feedback is：

$\left\{\begin{array}{c}\stackrel{\·}{x}=-\mathrm{\σ}x+\mathrm{\σ}y+Acos2\mathrm{\π}f\\ \stackrel{\·}{y}=rx-y-xz\\ \stackrel{\·}{z}=-bz+xy-k(u-z)\\ \stackrel{\·}{u}=\frac{2}{\mathrm{\τ}}(z-u)-\stackrel{\·}{z}\end{array}\right..$

3. the noise initiative control method according to claim 2 based on broad sense class Lorenz System, it is characterised in that institute Stating noise initiative control method also includes：

Addition amplitude is A in chaos system after the increase Systems with Time Delay Feedback₁, frequency be f₁The first default external excitation, to obtain Obtain Systems with Time Delay Feedback and single external excitation chaos system；

The Systems with Time Delay Feedback is with single external excitation chaos system：

$\left\{\begin{array}{c}\stackrel{\·}{x}=-\mathrm{\σ}x+\mathrm{\σ}y+A\cos 2\mathrm{\π}f+A_1\sin 2{\mathrm{\πf}}_1\\ \stackrel{\·}{y}=rx-y-xz\\ \stackrel{\·}{z}=-\mathrm{\β}z+xy-k\left(u-z\right)\\ \stackrel{\·}{u}=\frac{2}{\mathrm{\τ}}\left(z-u\right)-\stackrel{\·}{z}\end{array}\right..$

4. the noise initiative control method according to claim 2 based on broad sense class Lorenz System, it is characterised in that institute Stating noise initiative control method also includes：

The default external excitation of addition first and the second default external excitation in chaos system after the increase Systems with Time Delay Feedback, to obtain Systems with Time Delay Feedback and many external excitation chaos systems, the amplitude of the described first default external excitation is A₁, frequency be f₁, and it is described second pre- If the amplitude of external excitation is A₂, frequency be f₂；

The Systems with Time Delay Feedback is with many external excitation chaos systems：

$\left\{\begin{array}{c}\stackrel{\·}{x}=-\mathrm{\σ}x+\mathrm{\σ}y+Acos2\mathrm{\π}f+A_{1}sin2\mathrm{\π}f+A_{2}sin2{\mathrm{\πf}}_2\\ \stackrel{\·}{y}=rx-y-xz\\ \stackrel{\·}{z}=-\mathrm{\β}z+xy-k(u-z)\\ \stackrel{\·}{u}=\frac{2}{\mathrm{\τ}}(z-u)-\stackrel{\·}{z}\end{array}\right..$