JP4844502B2 - Vibration analysis system and vibration analysis method - Google Patents

Description

  The present invention relates to a technique for analyzing vibration of a structure.

  It is known that the vibration / noise performance of a structure is affected by design errors, manufacturing errors, disturbances, and the like. For example, even with products of the same specification, it may happen that vibrations and noises that are problematic only in some lots are generated due to slight manufacturing variations. If the factors of vibration and noise are known, it is possible to take measures to suppress them. However, it is usually very difficult to quickly find out where, how and at what scale the factors of vibration and noise are occurring. This is because it is difficult to specify from which part of the structure the vibration that affects the evaluation point vibration and noise propagates. In particular, a structure having a complicated structure and a large number of parts, such as an automobile, becomes more difficult.

  Nonetheless, there is no effective method for predicting the effects of errors, disturbances, etc. in advance, and problems were often revealed only when products and prototypes were actually completed. Although a system for simulating the influence of variations in physical quantities such as springs, masses, and plates on the evaluation point response has been put into practical use (CDH “CDH / VAO”), this system can only be studied using a simulation model. It cannot be applied to actual structures. Factors that affect vibration and noise performance are not represented by simple physical models such as springs, masses, and plates, but the shape, dimensions, rigidity, mass, physical properties (material properties), and parts of parts. Various factors such as the contact state are complicatedly intertwined, but there is a problem that the conventional system cannot take into account this kind of error / disturbance factor.

The following techniques are available as techniques for analyzing the vibration of the structure. Japanese Patent Application Laid-Open No. 2003-228561 discloses a method of obtaining a vibration level of a response point of a vehicle body by connecting an element other than the vehicle body to the vehicle body with a dynamic spring and performing frequency analysis on the motion equation of the vehicle body. Patent Document 2 discloses an FEM analysis method for modeling a soundproof material as a spring / mass model. Patent Document 3 discloses an evaluation method for obtaining rigidity from vibration displacement at 0 Hz of an FEM model representing an analysis target part.
JP-A-8-272837 JP 2006-65466 A JP 2007-94567 A

  The present invention has been made in view of the above circumstances, and the object of the present invention is a technology that can easily and accurately predict the effect of errors, disturbances, etc. of arbitrary parts of the structure on vibration / noise performance. Is to provide.

  In order to achieve the above object, the present invention adopts the following configuration.

The vibration analysis system according to the present invention includes a first transfer function between the input point and the point of interest for a structure having an input point to which vibration is applied, an evaluation point at which a response is evaluated, and the point of interest. Transfer function acquisition means for acquiring a second transfer function between the evaluation point and the point of interest, and a third transfer function between the point of interest and the same point of interest, and the third transfer Based on the fluctuation characteristic acquisition means for acquiring the fluctuation characteristic of the function, the first to third transfer functions, and the fluctuation characteristics of the third transfer function, the fluctuation of the third transfer function is the evaluation score. Influence calculating means for calculating the influence of the evaluation point on the response, and output means for outputting the influence of the evaluation point on the response.

  Here, the “target point” is a point to which an error / disturbance is applied, and the “variation characteristic of the third transfer function” is a parameter expressing the error / disturbance to be applied to the target point. By selecting the point of interest and setting the fluctuation characteristics of the transfer function, it is possible to give an arbitrary error / disturbance to an arbitrary part in the structure. In addition, by using the form of fluctuation characteristics of the transfer function instead of limited physical quantities such as springs, masses, and plates as in the conventional system, a comprehensive range of errors and disturbance factors that can occur at the point of interest And can be expressed directly. Then, by calculating the influence of the evaluation point on the response by calculating the transfer function, it is possible to easily and accurately predict the influence of the error / disturbance of the point of interest on the vibration / noise performance of the structure. The “transfer function” may be calculated from the result of a vibration experiment using an actual structure or may be calculated by simulation.

  Preferably, the variation characteristic of the third transfer function is given by a probability distribution, and the influence on the response of the evaluation point is expressed by a probability distribution of the response of the evaluation point. By using the probability distribution, it is possible to evaluate the risk of how much error, disturbance, etc. can occur at the point of interest, and how much it affects the evaluation point response.

  Furthermore, it is preferable that the variation characteristic of the third transfer function is set according to the characteristic of the point of interest. By varying the variation characteristic of the transfer function according to the characteristic of the point of interest, the influence on the vibration / noise performance can be calculated with higher accuracy.

  The structure has a plurality of the points of interest, and the third transfer function and its variation characteristics are acquired for each of the plurality of points of interest, and a third transmission of each of the plurality of points of interest is obtained. It is preferable that the influence of the evaluation point on the response is calculated for the function variation. The user can objectively compare the magnitude of the impact on vibration and noise performance (that is, the tolerance of error and disturbance) from the output results of each point of interest, and provide useful information for measures against vibration and noise. Obtainable.

  The present invention can be understood as a vibration analysis system having at least a part of the above means. The present invention can also be understood as a vibration analysis method including at least a part of the above processing, or a program for realizing the method. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  For example, in the vibration analysis method as one aspect of the present invention, the computer includes an input point to which vibration is applied, an evaluation point at which a response is evaluated, and a structure having a point of interest, the input point and the point of interest. A process of obtaining a first transfer function between the second point, a second transfer function between the evaluation point and the point of interest, and a third transfer function between the point of interest and the same point of interest; Based on the process of obtaining the variation characteristic of the third transfer function, the first to third transfer functions, and the variation characteristic of the third transfer function, the variation of the third transfer function is The process of calculating the influence of the evaluation point on the response and the process of outputting the influence of the evaluation point on the response are executed.

Further, the vibration analysis program as one aspect of the present invention includes an input point where a vibration is applied to a computer, an evaluation point where a response is evaluated, and a structure having a point of interest. A process of obtaining a first transfer function between the second point, a second transfer function between the evaluation point and the point of interest, and a third transfer function between the point of interest and the same point of interest; A process for obtaining a variation characteristic of the third transfer function; the first to third transfer functions; and the third transfer function.
A process of calculating the effect of the variation of the third transfer function on the response of the evaluation point, and a process of outputting the effect on the response of the evaluation point, based on the variation characteristic of the transfer function of It is a computer-readable program for making it happen.

  According to the present invention, it is possible to easily and accurately predict the influence of an error, disturbance, etc. of an arbitrary part of a structure on vibration / noise performance.

  Hereinafter, a preferred embodiment of the present invention will be described by taking a vehicle vibration analysis as an example. However, the scope of application of the present invention is not limited to vehicle vibration analysis, and the present invention is preferably applicable to vibration analysis of any structure in which vibration and noise are problems.

(System overview)
In vehicle development, reduction of vibration and noise is a very important issue, and various vibration and noise levels at predetermined performance evaluation points (eg, driver's ear position, steering wheel, seat, etc.) fall below the allowable value. Measures are taken. However, even if the target level can be cleared by an ideal model such as a simulation model or a prototype vehicle, not all actual vehicles (actual products) satisfy the target level. Due to design errors, manufacturing errors, disturbances, etc., the shape, dimensions, rigidity, mass, physical properties (material properties), contact status of the parts, etc. vary, thereby changing the vibration and noise performance of the vehicle and exceeding the allowable values. This is because vibration and noise may appear.

  In order to prevent the occurrence of such vibrations and noises, it is necessary to take measures such as tightening tolerances and quality control of the corresponding parts, changing the design, and adding damping members. For this purpose, it is necessary to clarify in advance which part of the structure (vehicle) varies and how much the vibration / noise performance will cause problems, and to narrow down the part (countermeasure part) where countermeasures should be taken. .

  The vibration analysis system of the present embodiment is a system for assisting the user in identifying the countermeasure part, and the influence of errors, disturbances, etc. occurring in any part of the structure on the vibration / noise level of the performance evaluation point. It provides a function to predict and output.

(Impact prediction method)
First, the basic theory of the impact prediction method of this system will be described with reference to FIG. FIG. 1 shows a theoretical model of the transfer function synthesis method.

  The first term on the left side of FIG. 1 represents the initial state of the structure. This structure has an input point a where vibration is applied, a performance evaluation point b where a response to the input (vibration / noise performance) is evaluated, and a point of interest c where an error is assumed. In this initial state, it is assumed that the structure is an ideal vibration system [Hij] having no error factor. Hij represents a transfer function between the points i and j. In the present embodiment, as the transfer function Hij, a compliance that is a displacement of the point j when the point i is vibrated is used, but the form of the transfer function is not limited to this.

As shown on the left side of FIG. 1, an error factor (vibration system of Fc = Q · Xc) occurs at the point of interest c in the ideal vibration system [Hij], and includes an error as shown on the right side of FIG. It is assumed that the vibration system [Hij] * is formed. Here, (Equation 1) is obtained by constructing the relational expression of FIG. 1 and eliminating Q by the theory of the transfer function synthesis method.

  Hac is a transfer function between the input point a and the point of interest c, Hbc is a transfer function between the performance evaluation point b and the point of interest c, and Hcc is a transfer function between the point of interest c and the same point of interest c ( This is called excitation point compliance at the point of interest c). ΔHab is a change amount (influence) of the response of the performance evaluation point b received by the error factor, and ΔHcc is a change amount of the excitation point compliance of the point of interest c caused by the error factor.

  If (Equation 1) gives the initial transfer function Hac, Hbc, Hcc of the structure and the variation ΔHcc of the excitation point compliance at the point of interest c due to the error factor (the amount of change of the transfer function Hcc) It can be seen that it is possible to calculate the influence ΔHab that the error generated at the point c gives to the vibration / noise performance of the structure.

  The transfer functions Hac, Hbc, and Hcc of the structure may be calculated by (1) simulation or (2) the result of a vibration experiment using the actual structure. In the case of (1), a vibration / noise simulation using a FEM model of the structure is performed, and a transfer function matrix is calculated. In the case of (2), a vibration / noise transmission measuring device (configuration consisting of a noise meter, accelerometer, signal generator, and vibrator) is attached to the structure, and a vibration experiment is performed. By analyzing, the transfer function matrix of the structure is obtained. It is desirable that the transfer function in the initial state is an ideal value that does not include an error factor. Therefore, average the measurement results from multiple measurements or, if possible, average the measurement results from multiple real structures. Is preferred.

  FIG. 2 shows the measurement results of the excitation point inertance at a certain point of interest for four real structures. The upper part of FIG. 2 shows the phase of the excitation point inertance, and the lower part shows the level (absolute value) of the excitation point inertance. The excitation point inertance is the acceleration at the same point of interest when the point of interest is vibrated, and corresponds to the second order differentiation of the excitation point compliance Hcc.

  As shown in FIG. 2, there is an error in the excitation point inertance for each frequency. The cause of the error is not limited to one, but may be various such as the shape, dimension, rigidity, mass, physical property value (material property), and component contact state at the point of interest. The measurement result of the excitation point inertance reflects the result of a combination of various factors that are difficult to separate. That is, it can be said that the Hcc fluctuation characteristic ΔHcc grasped from such a measurement result comprehensively and directly expresses various error / disturbance factors that may occur at the point of interest.

  The fluctuation characteristic ΔHcc of the excitation point compliance can be expressed by a probability distribution. However, the fluctuation range (standard deviation) and the probability distribution form (normal distribution, chi-square distribution, etc.) differ depending on the component characteristics at the point of interest. For example, regarding the material of the component, the manufacturing error increases in the order of metal <resin <rubber, so the fluctuation range of Hcc also increases. In addition, depending on the optional equipment of the structure, there may be variations in the shape of the parts to be attached. Such variation due to variation parts may also be regarded as one of errors and disturbance factors. Such variation characteristics ΔHcc corresponding to the component characteristics can be determined based on experimental results, simulations, or experience values as shown in FIG.

(System configuration)
Next, a specific configuration of the vibration analysis system of this embodiment will be described.

  FIG. 3 is a block diagram showing the configuration of the vibration analysis system. The vibration analysis system 1 includes a transfer function matrix acquisition unit 10, a fluctuation characteristic acquisition unit 11, an influence calculation unit 12, and an output unit 13 as main functions. This system can be configured by a general-purpose computer system including a CPU (Central Processing Unit), a storage device, a display device, an input device, etc. in terms of hardware. Each function described above is stored in the storage device. The program is executed by the CPU.

  The transfer function matrix acquisition unit 10 has a function of acquiring transfer function matrix data of a structure to be analyzed. Here, as shown in FIG. 4, a structure including an input point A, a performance evaluation point B, and a plurality of points of interest C1 to C5 is assumed. However, the number of points of interest can be freely set according to the purpose of analysis and analysis frequency. A plurality of input points and performance evaluation points may be set. It is assumed that the transfer function matrix of this structure is obtained in advance by simulation or experiment as described above.

  The fluctuation characteristic acquisition unit 11 has a function of acquiring the fluctuation characteristic ΔHcc of the excitation point compliance of each of the points of interest C1 to C5. As described above, the variation characteristic ΔHcc is defined in advance with an appropriate probability distribution according to the characteristic of each point of interest.

  The influence calculation unit 12 uses (Expression 1) to calculate the influence ΔHab that the fluctuation ΔHcc of the excitation point compliance has on the response (vibration / noise level) of the performance evaluation point B for each of the points of interest C1 to C5. The calculation result is output to the display device or the printing device by the output unit 13.

  5 and 6 show an example of calculation result output. FIG. 5 shows the fluctuation of the vibration / noise level at the performance evaluation point when the excitation point compliance at a certain point of interest fluctuates. The horizontal axis represents the frequency [Hz], and the vertical axis represents the vibration / noise level [dB]. The level of vibration / noise is represented by a probability distribution with the initial level being an average value, and is displayed in contour lines that are color-coded according to the probability value. FIG. 6 shows a probability distribution at a certain frequency. The horizontal axis is a value obtained by standardizing the frequency, and the vertical axis is a vibration / noise level [linear value]. When one frequency is selected on the graph of FIG. 5, the probability distribution at the selected frequency is displayed in detail on the graph of FIG. The graphs of the respective points of interest C1 to C5 can be switched and displayed side by side.

  The present system described above has the following advantages.

  By using the form of fluctuation characteristics ΔHcc of the transfer function (excitation point compliance) instead of limited physical quantities like springs, masses, and plates as in the conventional system, various errors that can occur at the point of interest Disturbance factors can be expressed comprehensively and directly. Then, by calculating the influence ΔHab of the evaluation point on the response by calculating the transfer function as in (Equation 1), the influence of the error / disturbance of the point of interest on the vibration / noise performance of the structure can be easily and accurately determined. Can be predicted well. In addition, by varying the variation characteristic ΔHcc according to the characteristics of the point of interest, the influence on the vibration / noise performance can be calculated with higher accuracy.

  In addition, the error / disturbance that occurs at the point of interest is defined by the probability distribution, and the influence of the evaluation point response is expressed by the probability distribution, so how much error / disturbance can occur at the point of interest, and It is possible to evaluate the risk of the impact on the evaluation point response.

In addition, the user can objectively compare the magnitude of the impact on the vibration / noise performance (that is, the tolerance of error / disturbance) by comparing the output results of each point of interest. You can get useful information for. For example, for parts where tolerances such as errors and disturbances are small, by taking measures such as tightening quality control and tolerances, changing the shape, material or contact state of parts, etc., vibration and noise performance can be improved. Variations can be reduced.

  Further, the present system has an advantage that the result can be output in a short time of several seconds to several minutes because the influence of each point of interest can be predicted only by the calculation based on the transfer function.

  The above embodiment is merely an example of the present invention. The scope of the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea. For example, in the above embodiment, compliance is used as a transfer function, but other types of transfer functions such as inertance may be used. Further, ΔHcc and ΔHab may be expressed by a simple value range instead of the probability distribution.

FIG. 1 is a diagram illustrating a theoretical model of the transfer function synthesis method. FIG. 2 is a diagram illustrating an example of variation in excitation point inertance. FIG. 3 is a block diagram showing the configuration of the vibration analysis system according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a structure. FIG. 5 is a diagram illustrating the vibration ΔNab of the performance / evaluation point when the excitation point compliance at a certain point of interest fluctuates. FIG. 6 is a diagram showing a probability distribution at a certain frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibration analysis system 10 Transfer function matrix acquisition part 11 Fluctuation characteristic acquisition part 12 Influence calculation part 13 Output part a, A input point b, B performance evaluation point c, C1-C5 attention point

Claims (5)

For a structure having an input point to which vibration is applied, an evaluation point at which response is evaluated, and a point of interest, a first transfer function between the input point and the point of interest, the evaluation point and the point of interest Transfer function acquisition means for acquiring a second transfer function between and a third transfer function between the point of interest and the same point of interest;
Fluctuation characteristic acquisition means for acquiring fluctuation characteristics of the third transfer function;
Based on the first to third transfer functions and the fluctuation characteristics of the third transfer function, an influence calculating means for calculating the influence of the fluctuation of the third transfer function on the response of the evaluation point;
Output means for outputting the influence on the response of the evaluation point;
A vibration analysis system comprising: The variation characteristic of the third transfer function is given by a probability distribution,
The vibration analysis system according to claim 1, wherein the influence on the response of the evaluation point is represented by a probability distribution of the response of the evaluation point. The vibration analysis system according to claim 1, wherein a variation characteristic of the third transfer function is set according to a characteristic of the point of interest. The structure has a plurality of the points of interest;
For each of the plurality of points of interest, the third transfer function and its variation characteristics are acquired,
4. The vibration analysis according to claim 1, wherein an influence on a response of the evaluation point is calculated with respect to a variation of the third transfer function of each of the plurality of points of interest. 5. system. Computer
For a structure having an input point to which vibration is applied, an evaluation point at which response is evaluated, and a point of interest, a first transfer function between the input point and the point of interest, the evaluation point and the point of interest A second transfer function between and a third transfer function between the point of interest and the same point of interest; and
Processing for obtaining a variation characteristic of the third transfer function;
A process of calculating an influence of a variation of the third transfer function on a response of the evaluation point based on the first to third transfer functions and a variation characteristic of the third transfer function;
Processing to output the influence on the response of the evaluation point;
The vibration analysis method characterized by performing.

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