JPH08327725A - Underwater-sonar designing system - Google Patents

Abstract

PURPOSE: To achieve the shortening of designing period and the high performance of the underwater sonar as an object by arbitrarily changing the design parameters such as the materials and shapes of piezoelectric elements and other structures, and readily analyzing the electric vibration characteristics and the sound pressure characteristics. CONSTITUTION: Element-matrix forming parts 5, 6 and 7 based on a finite element method are provided so as to facilitate the analysis of an electricity- structure compound. Analysis data required for a vibration analysis means 10 are formed in an element-matrix forming part 8 of the structure system. The vibration response obtained in the vibration analysis means 10 is used as the external force. The radiated vibration sound is analyzed in a sound analysis means 11, and fluid load is adequately evaluated in a fluid-load operating part 12. The adequate element is obtained in a correcting part 13. The element matrix obtained in this way and the element matrix, which is obtained from the finite element method of the electric system are used, and the dynamic behavior of the structure-electric system is obtained in analysis means 15. Furthermore, the radiated vibration sound is obtained in a sound analysis means 16, and the result is displayed on a display means 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for designing a structure for obtaining appropriate electric and vibration radiation frequency characteristics of an underwater sonar.

[0002]

2. Description of the Related Art Among underwater acoustic devices, an underwater sonar is constructed by connecting a piezoelectric element and this piezoelectric element and a general structure with an adhesive, and includes a piezoelectric element by applying an AC voltage to this piezoelectric element. Vibrates the structure to generate vibrating sound,
This propagation of sound waves is used.

At this time, the electrical characteristics of the piezoelectric element are converted into mechanical characteristics of a structure composed of the piezoelectric element, a general structure and an adhesive, and further converted into sound. A characteristic of the piezoelectric element in terms of dynamic characteristics is that when an AC voltage is applied, a resonance phenomenon occurs at the natural frequency of the piezoelectric element that matches the excitation frequency, and the vibration speed and vibration radiation sound show peaks. On the other hand, when the piezoelectric element is excited by a sound wave with a certain frequency,
When this excitation frequency matches the natural frequency of the piezoelectric element, a peak voltage is generated in the piezoelectric element. The resonance frequency can be changed by coupling another structure to the piezoelectric element.

In order to design such an underwater sonar,
MASON is Physical Acoustic IPART A (ACADEMIC P
RESS PP234〜247 (1964)) proposed a method to find the dynamic characteristics by replacing the electric and mechanical characteristics of the piezoelectric element with an equivalent electric circuit. In addition, a method of discretizing the electrical characteristics and mechanical characteristics of a piezoelectric element using the finite element method and analyzing the dynamic characteristics is reported in Journal of Acoustical Society of Japan, Volume 37, No. 7 (1981).

[0005]

In the above-mentioned prior art, the electrical and mechanical characteristics of the piezoelectric element, the mechanical characteristics of the general structure connected to the piezoelectric element, and the bonding for connecting the piezoelectric element and the general structure. It has been insufficient to predict the characteristics of the agent by coupling the vibration radiation sound of the structure including the piezoelectric element and the general structure in terms of analysis accuracy and design efficiency. Furthermore, it is difficult to model a medium such as water and consider it in the analysis.

An object of the present invention is to provide a design system for a designer to design a highly accurate underwater sonar efficiently and simply.

[0007]

In order to achieve the above-mentioned object, an element matrix generating section, an adhesive, and the like, which are discretized based on the finite element method for obtaining electric characteristics and structural vibration characteristics of a piezoelectric element, An element matrix generator that discretizes the structure based on the finite element method to determine its vibration characteristics, an element matrix generator that determines the electrical characteristics and structural vibration characteristics of the piezoelectric element, and these are discretized. The structural element matrix generator that superimposes the equations of motion for the elements of the structural system, the structural vibration analysis means that obtains the vibration characteristics of the structural system using the data of these structural element matrix generators, and the vibration velocity obtained from this Fluid load analysis means for evaluating the fluid load in water based on the structural system, and the additional mass and additional damping obtained by the fluid load analysis means Using the mass matrix, damping matrix, and correction matrix of the structural element matrix stored in the rigidity matrix of the elementary matrix generation section and the electrical system element matrix of the element matrix generation section of the piezoelectric element, the structure-electricity The coupling element matrix generating unit superimposes the matrices, and using this matrix, the dynamic response analysis means of the structure-electric coupling system determines the vibration response of the structural system and the input admittance of the electric system, and further the vibration velocity of the structural system. With external force as the external force, the sound pressure radiated into the water by the acoustic analysis means is obtained based on the boundary element method, and the structure at a position 1 m away from the vibration boundary surface with respect to the input admittance of the electric system and the input voltage to the piezoelectric element by the display means The sensitivity of the transmitted voltage, which is the oscillating radiation sound pressure emitted from the system, is displayed.

In order to obtain a vibration model of a structure in water, a structural system including a piezoelectric element in air is discretized based on the finite element method to derive a mass matrix, a stiffness matrix and a damping matrix, and By superposing the equations of motion derived from the elements, obtaining the natural frequency of the structural system from the obtained synthetic equation, and then applying an arbitrary excitation force to the structural system, the vibration radiation sound generated from the structural system is brought close The radiant impedance is obtained from the sound pressure, the radiative impedance is obtained from the sound pressure, the additional mass and the additional attenuation of the fluid are obtained, and the natural frequency is calculated again in addition to the discretized matrix. By repeating such calculations, the additional mass and additional damping at which the natural frequency reaches a constant value are obtained, and the vibration model of the fluid is obtained.

Further, the piezoelectric element is displayed so that the piezoelectric element can be evaluated based on the calculation result, which enables efficient design.

[0010]

According to the present invention, the electric characteristics of the piezoelectric element and the vibration characteristics of the structure including the piezoelectric element are analyzed as a coupled behavior based on the finite element method, and the electric impedance of the piezoelectric element when a voltage is applied to the piezoelectric element is analyzed. Obtain and display the frequency characteristics. The frequency characteristic display of the electric impedance is characterized in that the electric impedance characteristic obtained by using the material and shape of the piezoelectric element or the general structure as a design parameter is displayed. This makes it possible to effectively design the shapes and materials of the piezoelectric element and the general structure that satisfy the target electrical impedance of the underwater sonar in which the piezoelectric element and the general structure are combined.

Further, according to the present invention, in the underwater sonar in which the piezoelectric element and the general structure are combined, the load of water is evaluated as the additional mass and additional damping to the structure, and added to the mass and modal damping ratio of the structure. Then, the coupled behavior of the piezoelectric element and the vibration characteristic of the structural system including the piezoelectric element is analyzed based on the finite element method. Thereby, the dynamic behavior of the underwater sonar can be evaluated accurately.

Further, according to the present invention, the vibration radiation sound analysis means links the electric characteristics of the piezoelectric element when a unit voltage is applied to the piezoelectric element and the vibration characteristics of the structure including the piezoelectric element based on the finite element method. Frequency vibration response analysis is performed as the behavior, and by using this result, the transmitted voltage sensitivity expressed by the vibration radiation sound pressure generated from the structural system at the position 1 m from the vibration boundary surface of the structural system is calculated and displayed. Is characterized by.
The frequency characteristic of the transmitted voltage sensitivity is characterized in that the transmitted voltage sensitivity characteristic obtained by using the material and shape of the piezoelectric element or the general structure as design parameters is displayed. This makes it possible to effectively design the shapes and materials of the piezoelectric element and the general structure that satisfy the target transmission voltage sensitivity of the underwater sonar in which the piezoelectric element and the general structure are combined.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples. The feature of this embodiment is that the fluid load calculation unit 13, the structure element matrix correction unit 14, the structure-electric coupling system element matrix generating unit 15, the structure-electric coupling system dynamic characteristic analysis unit 16, and the display unit 18 are provided. Is provided. FIG. 1 is a block diagram showing an embodiment of the system of the present invention.
FIG. 2 shows a state in which the piezoelectric element is bonded to a general structure via an adhesive. In FIG. 2, 101 is a piezoelectric element, 102 is an adhesive, and 103 is a general structure. Detailed description will be made below based on an embodiment of the system of the present invention shown in FIG. The element data generation units 1 and 2 respectively divide the general structure and the adhesive used to bond the general structure with the piezoelectric element into finite elements, and use the attribute data generated by the attribute data generation unit 4
The element matrix generation unit 6 generates the rigidity matrix and mass matrix required for structural vibration analysis. Further, the piezoelectric element element generation unit 3 divides the piezoelectric element into finite elements, and the attribute value of the piezoelectric element generated by the attribute data generation unit 4 is used to generate the piezoelectric elements by the element matrix generation unit 7 based on the finite element method. Finite element models of the electrical and mechanical systems of the device are generated. This finite element model is given below.

The number 1 of the piezoelectric phenomenon is given by the element matrix generator 7 based on the attribute data generator of the piezoelectric element.

[0015]

[Equation 1]

When the equation 1 is discretized based on the finite element method, the following equation is given.

[0017]

[Equation 2]

[0018] Here, [K _p]: stiffness matrix [M _p]: Weight Matrix [theta _p]: electromechanical coupling matrix [G _p]: electrostatic matrix {d _p}: vibration displacement {Q}: electrode Potential ω: Angular frequency p: Piezoelectric element In the element matrix generation unit 7, the number 2 [K _p ], [M _p ],
[Θ _p ] and [G _p ] are stored.

Next, the mass matrix [M of the general structure, the adhesive and the piezoelectric element generated by the structural element matrix generating section 8 in the element matrix generating sections 5, 6, 7 [M
_s ], [M _a ], [M _p ], stiffness matrix [K _s ], [K
_a ] and [K _p ] are superposed as shown in 301, 302 and 303 of FIG. 3 on the common nodes of the respective elements, and as shown in 300, structural system element matrices [M] and [K] are obtained. .

The structural vibration analysis means 10 finds the natural frequency and frequency response of the structure using the structural element matrix and the damping coefficient and boundary conditions obtained from the attribute data generator 4. On the other hand, sound receiving point data and the like necessary for analyzing the vibration radiation sound from the structural vibration are generated by the acoustic analysis data generation unit 9 and acoustic analysis is performed by using the frequency response obtained by the structural vibration analysis means 10 as an external force. The means 11 determines the frequency response of sound pressure based on the boundary element method. Further, when the structure is in the fluid, the fluid load calculation unit 12 needs to evaluate the fluid as additional mass and additional damping. The method for obtaining the additional mass and additional damping will be described below. FIG. 4 shows a flow of analysis.

A vibration velocity of an arbitrary element i of the discretized structure system is set to u _i , and a sound receiving surface having the same shape and area s _i as the structure is set at a position a minute distance from the vibration boundary surface of the structure. , The sound pressure P _i at this position is obtained using the boundary element method.
At this time, the radiation impedance Z _Ri of the structure is defined by the following equation.

[0022]

(Equation 3)

Here, R _Ri and X _Ri are the real and imaginary parts of the radiation impedance Z _Ri , respectively, j is the imaginary unit, and p _i is the sound pressure. Now, assume that the fluid load is a vibration model in which the mass and the damping are coupled in series when the vibration radiation sound propagates in the fluid and is damped. At this time, the element i of the structure
(I = 1, ..., N ) mechanical impedance Z _i which is defined from the force F _i and the vibration velocity u _i which acts on the

[0024]

[Equation 4]

Assuming that the mechanical impedance and the radiation impedance of the structure are equal, the mass and damping coefficient of the element i can be obtained by equation (5).

[0026]

(Equation 5)

The mass and damping coefficient obtained by the equation 5 are the added mass and damping coefficient of the fluid acting on the structure.

The additional mass and additional damping coefficient obtained by the equation 5 are used for the structural analysis mass matrix and attribute data generation unit 4
Vibration analysis is performed again by superposing it on the damping matrix obtained from, and the natural frequency and frequency response are obtained. When the calculated natural frequency is different from the natural frequency calculated by the analyzing means 10, frequency response calculation and radiation sound calculation are further performed, and based on the results, the fluid added mass and the additional damping coefficient are calculated again using Equation 5. Then, structural vibration analysis is performed to obtain the natural frequency and compare it with the previously calculated value of the natural frequency. By repeating this process, the additional mass and additional damping coefficient of the fluid when the natural frequency becomes constant are evaluated.

Next, the additional mass and the additional damping coefficient of the fluid obtained by the fluid load calculation unit 12 are the same as those of the element matrix generated by the structure element matrix generation unit 8 by the structure element matrix correction unit 13. Superimpose at the node position.

From the above, the data of the structural system including the piezoelectric element necessary for the vibration analysis was obtained.

The structure-electric coupling element matrix is formed by using the mass, damping, and stiffness matrices obtained from the structural element matrix correcting section 13 and the electrostatic matrix and the electromechanical coupling matrix of the piezoelectric element obtained from the element matrix generating section 7. The generator 14 obtains the matrix [A (ω)] of the entire system. The equation at this time is shown in Equation 6, and the element matrix and the state vector are shown in Equation 7.

[0032]

(Equation 6)

[0033]

(Equation 7)

However, the subscript s indicates a general structure, a indicates an adhesive, and p indicates a piezoelectric element. (S) is a general structure,
(S)-(a)-(p) is a vibration displacement when a general structure, an adhesive, and a piezoelectric element are piled up, and (p) _e is a potential of the piezoelectric element. Expression 7 is a case where the area of the adhesive is the same as the area of the piezoelectric element and at the same position.

Using the element matrix generated by the structure-electric coupling system element matrix generating section 14, the structure-electric coupling system dynamic characteristic analyzing means 15 solves the following equation.

[0036]

(Equation 8)

Where {d _A } is the vibration displacement of the structural system,
{Φ _p } represents the electric potential of the electric system. Further, {F _A } is a general external force acting on the structural system, and {Q} is the electric charge applied to the electrode. The general external force {F _A } is given by Equation 8. When the electric potential {φ _p } is also given,
The vibration response of the structural system can be analyzed by Equation 8. When a unit potential is given and a general external force is given by the equation (8), the electric charge {Q} acting on the piezoelectric element can be obtained. The charge at this node i is Q
_{When i} is set, the charge Q _i and the current I _i are given by the following expressions.

[0038]

[Equation 9]

The input admittance Y _in is given by the following equation when the sum of all the elements constituting the electrode is taken.

[0040]

[Equation 10]

Input admittance Y found by equation 10
_in is a complex number and can be expressed as follows by dividing it into a real number part and an imaginary number part.

[0042]

[Equation 11]

The input admittance Y _in is obtained as a function of the angular frequency ω with the material of the piezoelectric element and the material and shape of the general structure as design parameters. When k is used as the design parameter at this time, the transmitted voltage sensitivity when k = k _i is obtained and displayed on the complex plane using the display means 17 to obtain FIG. Also, the absolute value of the input admittance Y _in and the absolute value of the real part B (ω) of the input admittance Y _in are used as a function of frequency by using the display means 17, and the material and shape of the piezoelectric element and the general structure are designed. 6 and 7 are obtained as display using parameters. It is possible to design in consideration of the electrical characteristics of the underwater sonar by using FIGS. 5, 6 and 7.

Next, the vibration response of the structural system when an arbitrary voltage is applied is obtained by the equation (8). Using the vibration analysis as an external force, the acoustic analysis means 17 can be used to calculate the sound pressure distribution at a position distant from the vibration boundary surface by an arbitrary distance. At this time, in the design of the piezoelectric element, in order to effectively evaluate the propagating sound pressure characteristic, there is a sound pressure characteristic with respect to the input voltage of the piezoelectric element at a position 1 m apart, and this is called the transmission voltage sensitivity. There is. This transmitted voltage sensitivity is calculated as a function of frequency. The target design guideline for the underwater sonar is determined by the magnitude of this voltage sensitivity. Therefore, this transmitted voltage sensitivity is at an arbitrary sound receiving point i (i + 1, ...,) 1 m away from the vibration boundary surface,
Materials and shapes of general structures and piezoelectric elements are given as design parameters. The transmitted voltage sensitivity at this time is shown in FIGS. FIG. 8 shows values when the frequency response of the transmitted voltage sensitivity is the sound receiving point i and the design parameter is k. Further, FIG. 9 shows the sound receiving point number, the transmission voltage sensitivity and the frequency three-dimensionally.

As described above, by obtaining the input admittance Y _in and the transmitted voltage sensitivity and expressing them on the display means as described above, the characteristics with respect to the design parameters of the electric system and the structural system can be easily evaluated, and thus the piezoelectric element. The underwater sonar including can be efficiently designed.

[0046]

According to the present invention, when designing an underwater sonar, the designer should consider how the material and shape of the piezoelectric element and the material and shape of the general structure influence their electrical characteristics and sound pressure characteristics. Since it is possible to easily determine whether or not to affect the display screen, the design period can be shortened and the design can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a design system of the present invention.

FIG. 2 is an explanatory view showing a state where a piezoelectric element is bonded to a general structure with an adhesive.

FIG. 3 is a block diagram showing generation of a structural system element matrix by superposing structural system element matrices.

FIG. 4 is a flow chart showing a procedure for modeling a fluid load into additional mass and additional damping.

FIG. 5 is a characteristic diagram showing the input impedance of the piezoelectric element in the design parameter represented by the material and shape of the piezoelectric element and the general structure on a complex plane.

FIG. 6 is a characteristic diagram showing the frequency characteristic of the absolute value of the input impedance for arbitrary design parameters.

FIG. 7 is a characteristic diagram showing the frequency characteristic of the absolute value of the real part of the input impedance for arbitrary design parameters.

FIG. 8 is a characteristic diagram showing transmission voltage sensitivity with respect to an arbitrary sound receiving point and a certain design parameter.

FIG. 9 is a characteristic diagram showing the transmitted voltage sensitivity with respect to an arbitrary sound receiving point and design parameters.

[Explanation of symbols]

8 ... Structural element matrix generation unit, 10 ... Structural vibration analysis means, 11, 16 ... Acoustic analysis means, 12 ... Acoustic load calculation unit, 13 ... Structural element matrix correction unit, 14 ...
Structure-electric coupling system element matrix generation unit, 15 ... Structure-electric coupling system dynamic characteristic analysis means, 16 ... Display means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiko Minami 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi Ltd. Information & Communication Division

Claims (2)

[Claims] 1. A system for designing an underwater sonar for connecting a general structure and a piezoelectric element with an adhesive and applying a voltage to the piezoelectric element to excite the structure and the piezoelectric element to generate vibration radiation sound. A part that generates a discretized element matrix of the object and the adhesive based on the finite element method,
The electric-structure of the piezoelectric element is discretized based on the finite element method, and the discretized element matrix of the general structure and the adhesive and the discretized element matrix of the piezoelectric element are superposed. A structural element matrix generation unit, a structural vibration analysis unit that obtains vibration characteristics such as a natural frequency and a vibration response using the structural element matrix, and a frequency response analysis result obtained from the vibration analysis unit as an external force. The acoustic analysis means for obtaining the sound pressure of the vibration radiation sound generated by the vibration of the object, the fluid load calculation means for obtaining the load characteristics of the fluid from the vibration analysis means and the acoustic analysis means, and the fluid load calculation means are obtained. An element matrix and a piezoelectric element of a conserved structure system for composing and storing a fluid load and a finite element model obtained in the structure Of the structure-electric coupling system element matrix generation unit that superimposes the discretized electric system matrix of, and the structure-electric coupling system dynamic characteristic from the attribute data generation unit that inputs the element matrix and boundary conditions. Means for analyzing, and acoustic analysis means for calculating vibration radiation sound pressure using the vibration response obtained from this analysis means as an external force,
Structure-Equipped with a display means for displaying the electrical input admittance obtained from the dynamic characteristic analysis means and the transmitted voltage sensitivity obtained from the acoustic analysis means, and the designer can see the display screen and An underwater sonar design system characterized by being able to judge its mechanical and electrical characteristics and design its structure and electrical characteristics. 2. The underwater sonar design system according to claim 1, wherein the fluid is modeled as an additional mass and an additional damping based on the radiation impedance at a position separated from the vibration boundary surface of the structure by a minute distance.