JPH076866B2 - Vibration control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration control device used for simulating a vibration environment, and more particularly to removing a low frequency output signal which adversely affects a vibration generator.

[0002]

2. Description of the Related Art It is generally well known that a product is damaged due to random vibrations given to the product during transportation or operation. Therefore, at each stage of trial manufacture and mass production, a simulator is used to test the vibration resistance by giving random vibration to the product, which is called a vibration test. A vibration control device controls the vibration generator in such a vibration test.

The vibration applied to the equipment in the actual operating environment or transportation environment generally has an irregular waveform, and no clear regularity such as that seen in a sine wave is found. It is difficult to add such an irregular waveform itself to the device. Therefore, an irregular waveform power spectrum density actually added is calculated, and a waveform having the target power spectrum density (referred to as a target spectrum) is added to the device.

Here, it should be taken into consideration that the vibration generator itself also has frequency characteristics. Therefore, it is not possible to give a vibration having a target spectrum to the device simply by giving a drive signal having a target spectrum to the vibration generator. Therefore, in consideration of the frequency response of the vibration generator, the target spectrum is corrected, a time series signal having this as a drive spectrum is generated, and this is given to the vibration generator.

Next, the configuration and vibration control method of the vibration control device 20 disclosed in Japanese Patent Laid-Open No. 2-98717 will be described with reference to FIG. The vibration generator 2 connected to the vibration control device 20 generates vibration based on the input electric signal. The equipment to be subjected to the vibration test is
The specimen 4 is fixed to the vibration generator 2. An acceleration pickup 6 is attached to the test piece 4. The vibration of the sample 4 is converted into an electric signal by the acceleration pickup 6. This electric signal is supplied to the A / D converter 8 after the high frequency signal is removed by the low pass filter 9. Therefore, the analog signal representing the vibration state of the sample 4 is converted into a digital signal by the A / D converter 8. This digital signal is a Fourier transform means
The power spectral density is input as 10 and the absolute value of the phase angle is discarded to calculate the power spectral density. This power spectral density is called a response spectrum. In order to execute such an operation on a computer, it is necessary to discretize the transform, and in practice, the discrete Fourier transform is performed.

At this time, it is general to use a fast Fourier transform FFT algorithm having a high calculation speed. Since the discrete Fourier transform is performed as described above, the obtained response spectrum becomes a line spectrum.

The response spectrum thus calculated is compared with the target spectrum in the control calculation means 12. As a result of the comparison, the spectrum to be given next is calculated. This is called the drive spectrum, which is also the line spectrum. The inverse Fourier transform means 14 gives a random phase to this drive spectrum and performs an inverse Fourier transform. That is, it is reconverted into digital data of a time function. This digital data is converted into an analog signal by the D / A converter 18, and then the high-frequency component is removed by the low-pass filter 21 and is given to the vibration generator 2.

The above-mentioned operation is repeated, and the vibration having the target spectrum is applied to the sample 4.

By the way, since the data converted into the time function by the inverse Fourier transforming means 14 is digital data, the sample 4 is given vibration having a discretized spectrum. Therefore, the vibration control device
At 20, in order to approximate the vibration that actually exists,
The window operating means 16 makes the discretized spectrum smoothly continuous.

A specific data conversion operation of the window operating means 16 will be described. First, the data of T seconds worth of data (referred to as one frame) input to the Fourier transform means 10 is stored in the circulation memory, and the read start position is changed to create a plurality of frames of data. Next, a window operation is performed so that the data between the frames has continuity. This window operation will be described with reference to FIGS. 6 and 7.
Figure 6 shows two frames created based on one frame
It represents 101 and 102. Actually, these data are digital signals, but are displayed in the form of analog signals for easy understanding. Each of these signals 101,
102 is a half-sine wave (sine function for half wavelength) or Hannin
An appropriate window function such as a g-function is multiplied to obtain waveforms 201 and 202 shown in FIG. The output signals 300 are obtained by superimposing the waveforms 201 and 202 while shifting them on the time axis.

Looking at the data obtained by performing such processing in terms of spectrum components, the line spectrum segment 73 on each spectrum line in FIG. 8A is centered around the original component frequency as shown in FIG. 8B. Continuous spectral component with spread
Change to 74. The effect of such "bleeding" that occurs for each spectral line overlaps to form the entire spectrum 75. That is, by performing the window operation by the window operation means 16, the data having the discretized spectrum can be converted into the data having the continuous spectrum.

The entire spectrum 75 formed by overlapping the effects of "bleeding" will be described in detail with reference to FIG. The horizontal axis in both A and B in the figure is the frequency axis,
The vertical axis represents the power spectrum density, and the frequency resolution Δf is 2.5 Hz.

It is assumed that the drive spectrum 73 as shown in FIG. Drive spectrum 73
Is a spectrum necessary for realizing a target spectrum in which the power spectrum density exists in the frequency range of 10 Hz or higher and the power spectrum density is 0 in the frequency range of 10 Hz or lower. In this example, for simplicity, it is assumed that the transfer characteristic of the controlled system is flat.

Frequency domain data having such a drive spectrum 73 is created, an inverse Fourier transform is performed, and the spectral structure is made continuous by the window operating means 16, and D /
It is converted into an analog signal by the A converter 18 and given to the vibration generator 2. Then, when the analog signal representing the vibration state of the sample 4 is converted into a digital signal and the response spectrum is examined, “bleeding” is found for each spectrum line corresponding to the drive spectrum 75 shown in FIG. 8B. It has occurred.

[0015]

However, the conventional vibration control device 20 has the following problems. The "bleeding out" caused by the window operation is naturally shown in FIG.
As shown in B, it also occurs in a portion with a frequency of 10 Hz or less.
As a result, a drive signal containing such low spectral component "bleeding" is provided to the vibration generator 2. As a result, the vibration of the low spectrum component which does not exist in the target spectrum is also given to the sample 4.

Here, the displacement D generated in the vibration generator 2
Becomes larger in inverse proportion to the square of the frequency fs of the spectral component. Therefore, when the frequency fs is several tens Hz or more, the absolute amount of displacement increase due to "bleeding" is small, and there is no problem that the vibration generator 2 is adversely affected. However, in the low-frequency region where the frequency fs is 10 Hz or less, the absolute amount of displacement increase due to "bleeding" becomes large, and the vibration generator 2 is rated (usually 10 to 25 mm (0-P)
Displacement) will be given.

In order to solve such a problem, conventionally,
In the vibration test having a large target spectrum component in the low frequency region (10 Hz or less), a vibration generator having a large rated displacement value is used or the frequency resolution Δf is reduced. However, in a vibration test having a large target spectrum component in the low frequency region, if a vibration generator having a large rated displacement value has to be used, the vibration generator that can perform the vibration test is limited. In addition, reducing the frequency resolution Δf causes a decrease in calculation speed and requires a larger storage capacity.

The present invention solves the above-mentioned problems, and even a vibration generator having a small rated displacement value can perform a vibration test having a large target spectrum component in the low frequency region, and the calculation speed is reduced. It is an object of the present invention to provide a vibration control device that can prevent an increase in storage capacity.

[0019]

A vibration control device according to a first aspect of the present invention includes a low frequency output signal removing means for removing an unnecessary low frequency output signal generated by the window operating means overlapping each other while shifting each frame. It is characterized by having.

The vibration control device according to a second aspect is further characterized in that the low frequency removed by the low frequency output signal removing means is 10 Hz or less.

The vibration control device according to claim 3 is further characterized in that the low frequency region removed by the low frequency output signal removing means can be selected.

[0022]

In the vibration control device according to the first and second aspects, the low-frequency output signal removing means removes an unnecessary low-frequency output signal generated by the window operating means overlapping the frames while shifting them. . Therefore, it is possible to prevent the vibration generator from being displaced beyond its rated value.

The vibration control device according to a third aspect of the present invention is further characterized in that the low frequency region removed by the low frequency output signal removing means can be selected. Therefore, the low frequency output signal to be removed can be selected.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a vibration control device according to the present invention. The vibration control device includes a high frequency input signal removing means 23, an A / D converter 8, a Fourier transforming means 10, a target spectrum storing means 11, a control calculating means 12, an inverse Fourier transforming means 14, a window operating means 16, a D / A converting means. And a high frequency output signal removing means 22 and a low frequency output signal removing means 19.

The vibration generator 2 connected to the vibration control device generates a vibration based on the input electric signal. The device to be subjected to the vibration test is fixed to the vibration generator 2 as the sample 4. Sample 4
An acceleration pickup 6 is attached to the.

The acceleration pickup 6 detects the vibration of the test piece 4 and converts it into an electric signal. This electric signal (analog signal) is supplied to the A / D converter 8 and converted into a digital signal after the high frequency input signal removing means 23 removes the high frequency signal. From this digital signal, the Fourier transform means 10 calculates the response spectrum. The calculated response spectrum is compared with the target spectrum in the control calculation means 12. As a result of the comparison, the drive spectrum is calculated and further the inverse Fourier transform means
The inverse Fourier transform is performed by 14. As a result, the drive spectrum is reconverted into time function digital data. The reconverted digital data is converted by the window operating means 16 into digital data for several frames in which the spectrum is continuous. This digital data is converted into an analog signal by the D / A converter 18, and the high frequency output signal removing means 22 removes the high frequency component.

By performing the window operation by the window operation means 16, unnecessary "bleeding" occurs in the above-mentioned low frequency region. Therefore, in the vibration control device, the high frequency output signal removing means 22 removes high frequency components, and then the low frequency output signal removing means 19 removes unnecessary low frequency output signals. Then, the output signal from which the unnecessary low frequency output signal is removed is given to the vibration generator 2. Such an operation is repeated, and the vibration having the target spectrum is applied to the sample 4. FIG. 2 shows an example of a hardware configuration in which each function of FIG. 1 is realized by using a CPU. The CPU 150 controls each unit via the bus line 50 according to the program of the ROM 154. The RAM 152 stores a drive spectrum, a target spectrum, and the like that are determined by the execution status of the test. The ROM 154 stores the control program of the CPU 150 and the like.

The operation of this apparatus will be described with reference to the flow charts of FIGS. 2 and 3. The acceleration pickup 6 detects the vibration of the sample 4 and converts it into an electric signal. This electric signal (analog signal) is supplied to the A / D converter 8 after the high frequency signal is removed by the low pass filter 9, and is converted into a digital signal. This digital signal is stored in the RAM 152. CPU150
Reads out the data stored in the RAM 152 (step S1 in FIG. 3), calculates the power spectrum density as the absolute value of the discarded phase angle, and stores the calculation result in the RAM 152 (step S2). This power spectral density is called a response spectrum. In order to execute such an operation on a computer, it is necessary to discretize the transformation, so
In this embodiment, the discrete Fourier transform is performed, and at this time, the fast Fourier transform FFT algorithm, which has a high calculation speed, is used. Since the discrete Fourier transform is performed in this way, the obtained response spectrum becomes a line spectrum.

Next, the CPU 150 compares the target spectrum previously stored in the RAM 152 with the response spectrum, calculates the drive spectrum to be given next, and stores the calculation result in the RAM 152 (step S
3). The drive spectrum is also a line spectrum.
The CPU 150 gives a random phase to the drive spectrum stored in the RAM 152, performs an inverse Fourier transform, reconverts it into digital data of a time function, and stores the converted data in the RAM 152 (step S4).

The CPU 150 commands the window operating means 16 to perform window operation on the conversion data stored in the RAM 152. The window operating means 16 is composed of a DSP capable of high-speed processing, stores one frame of data in a circular memory, and changes the read start position to create a plurality of frames of continuous spectrum data (see FIG. 7).

Next, the plurality of frames thus obtained are converted into analog signals by the D / A converter 18,
The low pass filter 21 removes high frequency components.

The analog signal from which the high frequency component has been removed is
An unnecessary low frequency output signal is removed by the high pass filter 29 which is the low frequency output signal removing means 19. This makes it possible to remove unnecessary low-frequency output signals from the “bleeding-out” generated by performing the window operation. An output signal from which an unnecessary low-frequency output signal is removed is applied to the vibration generator 2, and by repeating such an operation, vibration having a target spectrum is applied to the sample 4.

As described above, in this embodiment, the high-pass filter 29 is provided after the window operating means 16. Therefore, it is possible to remove an unnecessary low-frequency output signal generated by the window operation, and it is possible to prevent the vibration generator 2 from being displaced beyond its rated value.

The structure of the high pass filter 29 is shown in FIG.
The high-pass filter 29 includes a capacitor C, resistors R ₁ , R ₂ ,
It is a primary filter that combines R ₃ . The cutoff frequency f _C of the high pass filter 29 is expressed by the following equation.

F _C = 1 / (2πC · R) Therefore, the capacitor C and the resistors R ₁ , R ₂ and R ₃ may be set according to the desired cutoff frequency f _C. In this embodiment, since the cutoff frequency f _C was set to 1 Hz, 2 Hz and 10 Hz, the capacitor C was set to 1 μF, and the resistors R ₁ , R ₂ and R ₃ were set to 160 KΩ and 80 KΩ 16 KΩ, respectively.

As described above, the three types of resistors R ₁ , R ₂ and R ₃ are provided and the analog switches S _{1 to} S ₄ are switched, whereby the high pass filter 29 is operated in accordance with the frequency characteristic of the desired target spectrum. The low frequency output signal to be removed can be selected.

Further, depending on the desired frequency characteristic of the target spectrum, the high-pass filter 29 may adversely affect the target spectrum. Therefore, in the high pass filter 29, the analog switch S ₁ is turned on and S ₂
It is also possible not to use the high-pass filter 29 by turning off all of ~ S ₄ .

Since the characteristic of the high-pass filter 29 is not so steep, there is a possibility that the necessary low-frequency output signal may be removed. However, since the feedback loop including the vibration control device 1 provides the data that compensates for the removed amount as the drive spectrum, the target spectrum can be reproduced.

The high-pass filter 29 may be a secondary filter, and a positive feedback type or negative feedback type active filter may be used.

In the vibration control device 1 shown in FIG. 1, the D / A converter 18 converts the analog signal and then the low frequency output signal removing means 19 removes unnecessary low frequency output signals. I have to. However, a digital high-pass filter as the low frequency output signal removing means 19,
It may be provided between the window operating means 16 and the D / A converter 18. The operation in this case is as follows. The digital high-pass filter removes unnecessary low-frequency output signals from the created data of a plurality of frames. After that, the D / A converter 18 converts the converted analog signal into a high-frequency component by the high-frequency output signal removing means 22, and the converted analog signal is supplied to the vibration generator 2.

Further, the low pass filter 21 and the high pass filter 29 may be combined to form a band pass filter.

In the present embodiment, the cutoff frequency of the high pass filter 29 is 10 Hz or less. However, the cutoff frequency of the high pass filter 29 may be determined according to the rated displacement of the vibration generator 2.

Further, in the vibration control device 1, in order to realize its function, the CPU 150 is used and this is realized by software. However, some or all of them may be realized by a logic circuit.

Instead of the ROM 154 and the RAM 152, another storage medium such as a memory card may be used.

[0045]

In the vibration control device according to the first and second aspects of the present invention, the low frequency output signal removing means produces an unnecessary low frequency output signal generated by the window operating means overlapping the frames while shifting them. Remove. Therefore, it is possible to prevent the vibration generator from being displaced beyond its rated value. Accordingly, even a vibration generator having a small rated displacement value can perform a vibration test having a large target spectrum component in the low frequency region. Further, since the frequency resolution Δf does not have to be made smaller than necessary, it is possible to prevent the calculation speed from decreasing and the storage capacity from increasing. That is, it is possible to provide a vibration control device that is inexpensive and yet highly accurate.

The vibration control device according to a third aspect of the present invention is further characterized in that the low frequency region removed by the low frequency output signal removing means can be selected. Therefore, it is possible to provide the vibration control device capable of selecting the low-frequency output signal to be removed according to the frequency characteristic of the target spectrum.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a vibration control device that is an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a hardware configuration in which each function of the vibration control device is realized by using a CPU.

FIG. 3 is a flowchart showing the operation of CPU 150.

FIG. 4 is a diagram showing a structure of a high-pass filter 29.

FIG. 5 is a diagram showing a configuration of a conventional vibration control device 20.

FIG. 6 is a diagram for explaining the function of window operating means 16.

FIG. 7 is a diagram for explaining the function of the window operating means 16.

FIG. 8 is a diagram for explaining “bleeding out” caused by a window operation.

[Explanation of symbols]

 8 ... A / D converter 10 ... Fourier transform means 11 ... Target spectrum storage means 12 ... Control calculation means 14 ... Inverse Fourier transform means 16 ... Window operation means 18 ... D / A converter 19 ... Low frequency output signal removing means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Horiuchi 51 Tianjin Fujinoki, Itami City, Hyogo Prefecture BM Co., Ltd. (56) References Japanese Patent Publication Sho 57-16685 (JP, B2)

Claims (3)

[Claims] 1. A / A for converting a detection signal from an acceleration pickup for measuring the acceleration of a specimen into a digital signal.
D converter, Fourier transform means for analyzing the digital signal into a frequency spectrum and outputting it as a response spectrum, target spectrum storage means for storing a target spectrum, control operation means for comparing the response spectrum and the target spectrum, and obtaining a drive spectrum An inverse Fourier transform means for converting the drive spectrum to a digital signal of a time function after giving a random phase to the digital signal, and a predetermined number N of words of the digital signal of the time function as one frame A window is stored by storing a signal in a one-frame storage unit having a circulating action and changing a take-out leading position to generate a plurality of frames, multiplying each frame by window function data, and then shifting each frame while shifting them. The output from the operating means and window operating means is In a vibration control device including a D / A converter that converts the signal into a signal and supplies the signal to a vibration generator, a low frequency that removes an unnecessary low frequency output signal generated by overlapping the windows operating means while shifting each frame. A vibration control device comprising output signal removing means. 2. The vibration control device according to claim 1, wherein the low frequency removed by the low frequency output signal removing means is 10 Hz or less. 3. The vibration control device according to claim 1 or 2, wherein the low frequency region removed by the low frequency output signal removing means is selectable.