JP2007225433A - Vibration mode determination method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine accurately each characteristic vibration mode of various objects by measuring vibration in the noncontact state, and to reduce facility cost by a simple device constitution. <P>SOLUTION: A sound radiated from a vibrating measuring object W is measured near the measuring object W by using a plurality of microphones 12 held in the noncontact state near the measuring position of the measuring object W by a tool 14. Hereby, information on a vibration mode of the object included in the sound radiated from the measuring object W can be acquired accurately before being attenuated. Then, signals of the sound collected by the plurality of microphones 12 are collected in time series by a collection device 18, and collected data by the collection device 18 are subjected to complex spectral processing by a processing device 20, to thereby enable visualization of the vibration mode of the measuring object W. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibration mode determination technique for an object.

Many objects have a vibration mode (a spatial shape change of vibration of the object, also referred to as a vibration waveform). And grasping the natural vibration mode of a single component or a structure is extremely effective in taking appropriate vibration countermeasures (addition of beams, shape change, plate thickness change, material change, etc.). Therefore, conventionally, various methods for determining the vibration mode of an object have been proposed. The most common method is a mode analysis method. In order to extract the vibration mode of an object, the object is artificially excited, and the frequency response function (transfer function) is calculated from the excitation and response signals. This is a method for obtaining the vibration mode finally.
In addition, in order to determine the vibration mode of an object, it is necessary to capture the vibration generated in the object. As a method for measuring this, an acceleration sensor is attached to a plurality of measurement points of the object, and the vibration of the object is directly measured. In general, the measurement method is general. On the other hand, a technique using a laser Doppler vibrometer is widely used as a technique for performing vibration measurement in contact with an object (see, for example, Patent Document 1).

Japanese Patent Publication No. 7-85047

However, in the method of directly measuring the vibration of the object by attaching the acceleration sensor to a plurality of measurement points of the object, the vibration measurement is difficult or impossible when the measurement target is like a rotating body. There was a case. In addition, in the case of a structure (bell or the like) having a small vibration attenuation, vibration characteristics change due to the application of an acceleration sensor, making it difficult to accurately determine the vibration mode. It was. On the other hand, according to the method of measuring contacted vibration using a laser Doppler vibrometer, vibration measurement is possible even for objects that are not suitable for using a contact-type acceleration sensor as described above, but the apparatus is large. Moreover, since the price of an apparatus is expensive, it is not widely used.
The present invention has been made in view of the above problems, and the object of the present invention is to enable non-contact vibration measurement to accurately determine the natural vibration modes of various objects, and The object is to reduce equipment costs with a simple device configuration.

In order to solve the above problems, a vibration mode determination method according to the present invention is configured to simultaneously measure sound radiated from a vibrating object to be measured at a plurality of locations in the vicinity of the object to be measured, and to obtain the measurement data in time series. And the vibration mode of the object to be measured is visualized by performing complex spectrum processing on the collected data.
According to the present invention, by measuring the sound radiated from the vibrating object to be measured in the vicinity of the object to be measured, information related to the vibration mode of the object included in the sound radiated from the object to be measured is attenuated. In addition, it is possible to capture accurately. In addition, such measurement is simultaneously measured at a plurality of locations of the object to be measured, the measurement data is collected in time series, and the collected data is subjected to complex spectrum processing, whereby sound emitted from the vibrating object to be measured is obtained. It is possible to visualize the vibration mode of the object to be measured in a non-contact manner.

In addition, a vibration mode determination apparatus according to the present invention for solving the above-described problems includes a plurality of microphones, a jig for holding the plurality of microphones in a contacted state in the vicinity of the measurement position of the object to be measured, and the plurality of the plurality of microphones. It is characterized by comprising a collecting device for collecting sound signals collected by the microphones in time series, and a processing device for performing complex spectrum processing on the collected data of the collecting device.
According to the present invention, using a plurality of microphones held in contact with a jig in the vicinity of the measurement position of the object to be measured, the sound emitted from the vibrating object to be measured is measured in the vicinity of the object to be measured. . Therefore, the information regarding the vibration mode of the object included in the sound radiated from the object to be measured can be accurately captured before being attenuated. Then, the sound signals collected by the plurality of microphones are collected in time series by the collecting device, and the collected data of the collecting device is subjected to complex spectrum processing by the processing device, thereby being radiated from the object to be oscillated. It is possible to visualize the vibration mode of the object to be measured in a non-contact manner.

  Since the present invention is configured as described above, vibration measurement of an object can be performed without contact, and natural vibration modes of various objects can be accurately determined. In addition, the equipment cost can be reduced with a simple device configuration.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The object vibration mode determination apparatus 10 according to the embodiment of the present invention has a configuration schematically shown in FIG. 1, and includes a plurality of microphones 12 and a plurality of microphones 12 of the object W to be measured. A jig 14 is provided in the vicinity of the measurement position for holding it in a contacted state. The characteristics of each microphone 12 must be such that the term frequency amplitude characteristic is flat (constant), and is basically configured and has a uniform phase. The microphone 12 is preferably non-directional. The object vibration mode determination device 10 simultaneously uses a microphone amplifier 16 that amplifies a sound signal collected by a plurality of microphones 12 and data from a measurement channel assigned to each microphone 12 as time-series data. A collecting device 18 for sampling is provided. Further, a processing device 20 that performs complex spectrum processing on the collected data of the collecting device 18 is provided. The processing device 20 uses an electronic computer such as a personal computer, and performs a general complex spectrum process as a vibration analysis technique on the collected data so that the vibration mode can be easily determined by an interface such as a monitor. is there. Further, the processing device 20 includes a control logic that performs a visualization process based on the collected data subjected to the complex spectrum process. Note that the processing device 20 can also perform cross spectrum processing on the collected data of the collection device 18 using the result of complex spectrum processing (phased FFT processing) as necessary.

Here, the procedure for determining the vibration mode of the workpiece W by the vibration mode determination device 10 of FIG. 1 will be described with reference to FIG.
(1) Determine the workpiece W. The object to be measured W is not limited to a single component but may be a structure configured by combining a plurality of components. However, measurement of the inside of a closed space or a concave surface where sound radiated from an object sounds or resonates is not suitable for this method.
(2) The measurement position of the workpiece W is determined. As this measurement position, a position suitable for collecting information related to the vibration mode of the object included in the close sound radiated from the measurement object W is selected. Such a selection can be determined empirically by collecting experimental data in advance for each shape and structure of the workpiece W. Then, a plurality of microphones 12 are arranged by the jig 14 in the vicinity of the determined measurement position (position separated from the surface of the workpiece W by about 10 to 30 mm). Note that information regarding the vibration mode of the object included in the proximity sound radiated from the DUT W includes an evanescent wave.
(3) Also, shape data of the non-measurement W is created. The shape data only needs to include at least measurement position information of the workpiece W, and drawing data of the non-measurement workpiece W can also be used. The shape data of the non-measurement W is input to the processing device 20 and used when determining the vibration mode described later.
(4) Sounds radiated from the object to be measured W are collected by the plurality of microphones 12. The signals of each channel collected by the plurality of microphones 12 are amplified by the microphone amplifier 16 and simultaneously sampled as time series data by the collecting device 18.
(5) The processing device 20 performs complex spectrum processing on the collected data of the collecting device 18.
(6) The processing device 20 visualizes the vibration mode by comparing the collected data subjected to the complex spectrum processing with the shape data created in (3) above. Visualization of the vibration mode is performed for a specified frequency (mainly the natural frequency of the object W to be measured).

FIG. 3 illustrates a state in which the vibration mode is visualized by using the brake disc 22 of the automobile as an object to be measured. As the measurement positions on the surface of the brake disk 22, eight places are selected at equal intervals on the disk mounting surface near the center, and eight places are equally spaced on the braking surface, for a total of 16 selected positions. Sixteen microphones 12 are held by a jig 14. In the illustrated example, the jig 14 is formed by bending a solid round bar in accordance with the shape of the brake disk 22, and concentrically forming two wheels 14a and 14b, and arm portions 14c for supporting the two wheels 14a and 14b, The microphone 12 is held by a clip 14e that forms 14d and is fixed to the wheels 14a and 14b. Each microphone 12 is connected to a microphone amplifier 16 (FIG. 1) by a cable 13. Reference numeral 24 denotes a cushion mat on which the brake disc 22 is placed.
Since the brake disk 22 does not vibrate by itself, sound is emitted from the brake disk 22 by exciting one place with a hammer. Further, in this method, it is not necessary to measure the excitation signal (hammer force or the like), which is performed by the conventional vibration mode determination method using an acceleration sensor.

  4 to 7 show the vibration modes of the brake disk 22 at the specified frequencies in a visualized manner. In each of the drawings, (a) shows a vibration mode (the present invention) visualized based on a proximity sound, and (b) shows an acceleration sensor pasted on a place where the microphone 12 is placed as a comparative reference. The vibration mode visualized by directly measuring the vibration of the brake disc 22 (conventional method) is shown. In each figure, the shape data of the brake disk 22 is indicated by a dotted line, and the vibration mode is indicated by a solid line.

Furthermore, FIGS. 8 to 12 show the results of visualizing the vibration mode for each specified frequency, using an aluminum rod as the object to be measured W as another example. In this case, nine measurement positions are selected, and the microphone is held by a jig near each measurement position. Also, sound is emitted from the aluminum rod by vibrating one portion of the aluminum rod with a hammer.
In each of FIGS. 8 to 12, (a) shows a vibration mode (the present invention) visualized based on a proximity sound, and (b) shows an acceleration sensor as a comparison reference. The vibration mode visualized by sticking to the placement location and directly measuring the vibration of the aluminum rod (conventional method) is shown. In each figure, the shape data of the aluminum bar is indicated by a dotted line, and the vibration mode is indicated by a solid line.

As is clear from FIGS. 4 to 12 above, the vibration mode visualized by the method according to the present invention and the vibration mode visualized by the conventional method are visualized, and as a result, a high correlation is obtained between them. It can be seen that the vibration mode determination result by the method according to the invention is highly reliable.
When the non-measurement W is an object that vibrates by itself (such as an operating machine), vibration with a hammer is not necessary. Even when the non-measurement W is a structure configured by combining a plurality of parts, the microphone 12 is disposed in the vicinity of a position suitable for collecting information on the vibration mode of the structure. Thus, the determination by visualization of the vibration mode can be similarly performed.

In addition, a symmetrical object has multiple roots (two or more modes exist at one frequency), but according to the embodiment of the present invention, multiple roots in the vibration mode of the non-measurement W It is also possible to confirm this.
For example, in the case where the object to be measured W is a symmetric glass container (glass or the like), a plurality of microphones are arranged close to each other at equal intervals around the container, and the sampling theorem (frequency more than twice the input frequency) 2), the time data (number of sampling data per unit time) is sampled more in the step of FIG. 2 (4). Thereby, by increasing the frequency resolution of the complex spectrum at the specified frequency, the number of spectra increases and it becomes easier to obtain sound peaks. As a result, as shown in FIG. 13, it is possible to accurately capture the peaks of the adjacent frequencies. In general, it is extremely difficult to manufacture an object having a uniform shape even if the object has a uniform shape. Therefore, when a waveform as shown in FIG. Presence of a plurality of modes at the selected frequency).
In the FFT (Fast Fourier Transform) analyzer used for vibration analysis, the number of points of time data to be sampled is usually about 1024, 2048 to 32768 points. However, in the complex spectrum processing in the embodiment of the present invention, It is possible to collect more sampling data by taking a sufficiently long sampling time of the proximity sound. Therefore, although depending on the calculation speed of the processing device 20, for example, the number of points of time data can be increased to a huge number such as 1 million points, and finer frequency resolution can be obtained.

  Then, similarly to the step of FIG. 2 (5), the processing device 20 performs complex spectrum processing on the collected data of the collecting device 18, and the processing device 20 performs complex spectrum processing similarly to the step of FIG. 2 (6). The vibration mode can be visualized by comparing the collected data with the shape data of the glass container having a symmetrical shape created in the same manner as the step of FIG. 2 (3). 14 and 15 show the results of visualizing the multiple roots in this way. In the example shown in the figure, 16 measurement positions are selected, (a) shows the vibration mode of the symmetrical container visualized according to the present invention, and (b) visualizes the vibration mode by the conventional method. The vibration mode of the symmetrically shaped vessel is shown.

  The effects obtained by the embodiment of the present invention having the above-described configuration are as follows. That is, according to the vibration mode determination method according to the embodiment of the present invention, the sound radiated from the vibrating object W is measured in the vicinity of the object W to be radiated from the object W. It is possible to accurately capture the information about the vibration mode of the object included in the sound before the sound is attenuated. Moreover, such measurement is simultaneously measured at a plurality of locations on the workpiece W, the measurement data is collected in time series, and the collected data is subjected to complex spectrum processing, thereby visualizing the vibration mode of the workpiece W Can be performed.

In addition, according to the vibration mode determination device according to the embodiment of the present invention, the object to be vibrated using the plurality of microphones 12 held in contact with the jig 14 in the vicinity of the measurement position of the object W to be measured. The sound radiated from W is measured in the vicinity of the workpiece W. Therefore, the information (evanescent wave) related to the vibration mode of the object included in the sound radiated from the object W to be measured can be accurately captured before being attenuated. Then, the collecting device 18 collects sound signals collected by the plurality of microphones 12 in time series, and the processing device 20 subjects the collected data of the collecting device 18 to complex spectrum processing, thereby allowing the object to be measured W to be measured. It is possible to visualize the vibration mode.
When it is necessary to measure the sound radiated from each part of the object W to be measured in a plurality of times instead of simultaneously, the collected data of the collecting device 18 is subjected to complex spectrum processing in the processing device 20, and The vibration mode can be visualized by the cross spectrum processing.
Furthermore, according to the embodiment of the present invention, it is possible to visualize the multiple roots of a symmetrical object by sampling more time data.

As described above, according to the embodiment of the present invention, the vibration mode can be grasped without contact with the object to be measured. For example, an acceleration sensor such as a rotating shaft can be pasted. It is possible to accurately determine the vibration mode even for an impossible object or a structure with small attenuation that has a large adverse effect due to application of an acceleration sensor. It is also possible to visualize the transient movement of the object (for example, the movement of paper in the printer). In addition, it is possible to configure a vibration mode determination device at an extremely low cost compared to a laser Doppler vibrometer, and the price per sensor uses a microphone compared to a vibration mode determination device using an acceleration sensor. Therefore, it is possible to provide a low-cost vibration mode determination device.
Therefore, it becomes possible to accurately determine the vibration modes of various objects, and to reflect them in measures against vibrations of the objects.

It is the schematic of the vibration mode determination apparatus which concerns on embodiment of this invention. It is a flowchart of the vibration mode determination method which concerns on embodiment of this invention. It is a figure which shows the specific embodiment of the vibration mode determination apparatus which concerns on embodiment of this invention. It is the figure which visualized the vibration mode in the designated frequency (about 1.4KHz) of a brake disk, (a) shows what is based on the vibration mode determination device of FIG. 3, and (b) shows that based on the prior art as a comparative example. Yes. It is the figure which visualized the vibration mode in the designated frequency (about 2.9KHz) of a brake disk, (a) shows what is based on the vibration mode determination device of FIG. 3, and (b) shows that based on the prior art as a comparative example. Yes. It is the figure which visualized the vibration mode in the designated frequency (about 3.3KHz) of a brake disk, (a) shows what is based on the vibration mode determination device of FIG. 3, and (b) shows that based on the prior art as a comparative example. Yes. It is the figure which visualized the vibration mode in the designated frequency (about 3.8 KHz) of a brake disk, (a) shows what is based on the vibration mode determination device of FIG. 3, and (b) shows that based on the prior art as a comparative example. Yes. It is the figure which visualized the vibration mode in the designated frequency (about 64 Hz) of the aluminum rod, (a) shows what is based on the vibration mode determination device of FIG. 1, and (b) shows that based on the prior art as a comparative example. . It is the figure which visualized the vibration mode in the designated frequency (about 175 Hz) of an aluminum stick, (a) shows what is based on the vibration mode judging device of FIG. 1, and (b) shows that based on the prior art as a comparative example. . It is the figure which visualized the vibration mode in the designated frequency (about 342 Hz) of the aluminum rod, (a) shows what is based on the vibration mode determination device of FIG. 1, and (b) shows that based on the prior art as a comparative example. . It is the figure which visualized the vibration mode in the designated frequency (about 565 Hz) of an aluminum stick, (a) shows what is based on the vibration mode judging device of FIG. 1, and (b) shows that based on the prior art as a comparative example. . It is the figure which visualized the vibration mode in the specified frequency (about 1.6KHz) of the rod of aluminum, (a) shows what is based on the vibration mode judging device of FIG. 3, and (b) shows that based on the prior art as a comparative example. ing. It is a wave form diagram which shows a mode that the peak of the frequency which adjoined was caught. It is the figure which visualized one vibration mode concerning the double root of the glass container of symmetry shape, (a) is based on the vibration mode judging device of FIG. 3, (b) is based on the prior art as a comparative example. Show. It is the figure which visualized the other vibration mode which concerns on the double root of the glass container of symmetry shape, (a) is based on the vibration mode determination apparatus of FIG. 3, (b) is based on a prior art as a comparative example Is shown.

Explanation of symbols

  10: Vibration mode determination device, 12: Microphone, 14: Jig, 16: Microphone amplifier, 18: Collection device, 20: Processing device

Claims (2)

The sound radiated from the vibrating object to be measured is measured simultaneously at a plurality of locations in the vicinity of the object to be measured, the measurement data is collected in time series, and the collected data is subjected to complex spectrum processing to be measured. A vibration mode determination method characterized by visualizing a vibration mode of an object. A plurality of microphones, a jig for holding the plurality of microphones in contact with each other in the vicinity of the measurement position of the object to be measured, a collecting device that collects sound signals collected by the plurality of microphones in time series, and A vibration mode determination device comprising: a processing device that performs complex spectrum processing on the collected data of the collection device.

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