JPH065191B2 - Vibration control device - Google Patents

Description

The present invention relates to a vibration control device used for simulating a vibration environment.

[Prior Art] It is generally well known that vibrations that occur during transportation and operation can cause equipment failure. Therefore, the vibration resistance is checked by a simulator at each stage of trial manufacture and mass production, which is called a vibration test. In this vibration test, the vibration control device controls the vibration generator.

The vibration applied to the equipment placed 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, the power spectrum density of the irregularly added waveform is calculated, and a waveform having the target power spectrum density (referred to as the target spectrum) is added to the device.

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

FIG. 4 shows the configuration of a conventional vibration control device. The vibration generator 2 generates 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. Specimen 4
An acceleration pickup 6 is attached, and its output is given to an A / D converter 8. Therefore, specimen 4
The analog signal representing the vibration state of is converted into a digital signal by the A / D converter 8. This digital signal is input to the Fourier transforming means 10 and the power spectrum density as the absolute value of the phase angle is calculated. 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 which has a high calculation speed. Since the discrete Fourier transform is performed as described above, the obtained response spectrum is a line spectrum.

The response spectrum calculated in this way 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 a drive spectrum, which is also a line spectrum.
The inverse Fourier exchange means 14 uses this drive spectrum as
Inverse Fourier exchange is performed by giving a random phase. 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 given to the vibration generator 2.

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

By the way, the series of operations described above requires time. Therefore, if the data for one frame is created from the data for T seconds (referred to as one frame) input to the Fourier transform means 10 and given to the D / A converter 18, the processing cannot be completed in time. Become. Therefore, it is necessary to create data for several frames based on the input data for one frame. In addition, it is necessary to smoothly connect the created data of several frames. To do this is the window operation means
16

First, one frame of data is stored in the circulation memory, and the read head position is changed to create a plurality of frames of data. Next, the plurality of frames thus obtained are applied to the vibration generator 2 via the D / A converter 18. At this time, the data between the frames must have continuity. Otherwise, unnecessary spectrum will be generated due to discontinuity between frames.

Conventionally, window operation has been performed in order to provide continuity between frames. This window operation will be described with reference to FIGS. FIG. 5 shows two frames 101 and 102 created based on one frame. Although these data are actually digital signals, they are displayed in the form of analog signals for easy understanding.
Each of these signals 101 and 102 is multiplied by a half sine wave (sine function for half wavelength) to obtain waveforms 201 and 202 shown in FIG. An output signal 300 is obtained by superimposing the waveforms 201 and 202 while shifting them on the time axis.

As described above, the continuity between the frames is obtained.

[Problems to be Solved by the Invention] By the way, the Fourier transform means 10 performs the discrete Fourier transform (FFT) in order to implement this on a digital computer, as described above. Therefore, the response spectrum is obtained as a line spectrum, and the drive spectrum obtained based on this is also a line spectrum, and the time-series data obtained by performing inverse Fourier exchange on it is a pseudo-random signal.

Real vibrations are usually truly random with a continuous spectrum and rarely consist of line spectral components. Therefore, the vibration control device is required to be able to output a vibration signal having a continuous spectrum that is truly random.

In the conventional device, sufficient consideration and consideration were not given to the continuation of the line spectrum. However, the window operation for smoothly connecting the signals between the frames results in the continuation of the line spectrum. That is, the window operation causes the line spectrum to spread and is made continuous (true randomization).

As described above, in the related art, although the spectrum is continuously made as a result, the window operation, particularly the relation between the window function and the spread of the spectrum is not taken into consideration. That is, the conventional apparatus using the half-sine wave as the window function has a problem that it is not possible to give random vibration suitable for the purpose depending on the purpose of the vibration test.

In view of the above problems, it is an object of the present invention to provide a vibration control device capable of giving random vibration in accordance with the purpose of a vibration test.

[Means for Solving the Problem] In the vibration control device according to claim 1, W (t) = 0.5 + 0.5 · cos ((2π / T) is used as the window function.
It is characterized by using a material substantially equivalent to t).
Note that T is the time length of one frame and t is the time.

In the vibration control device according to claim 2, the window function is substantially W (t) = 0.42 + 0.5 · cos ((2π / T) t) + 0.08 · cos ((4π / T) t). The feature is that they are equivalent to each other.

The vibration control device according to claim 3 has, as a window function, W (t) = 0.35875 + 0.48829 · cos ((2π / T) t) + 0.14128 · cos ((4π / T) t) +0.01168. It is characterized in that a material substantially equivalent to cos ((6π / T) t) is used.

The vibration control device according to claim 4 uses, as a window function, W (t) = 0.3635819 + 0.4891775 · cos ((2π / T) t) + 0.1365995 · cos ((4π / T) t) +0.0106411. It is characterized in that a material substantially equivalent to cos ((6π / T) t) is used.

The vibration control device according to a fifth aspect switches two or more window functions among the window functions according to the first to fourth aspects, and selects and uses one.

[Operation and Example] A basic block diagram of the vibration control device according to the present invention is as follows.
It is similar to the conventional device (see FIG. 4). A logic circuit can be used to realize the functions of these blocks, but a microcomputer may be used as shown in FIG. Further, in FIG. 2, the window operating means 16 is provided independently, but the same function can be provided by the calculation by the CPU 150. In this case, the output is output from the bus 50 to the D / A converter 18.

An example of the window operating means 16 which is a characteristic part of the present invention,
Shown in FIGS. 1A and 1B. 1A shows a data processing unit, and FIG. 1B shows an address generating unit. Here, 1
The number I of frames created based on one frame is four. That is, in the window operation, the number of overlaps of each frame is four times. In the past, the number of overlaps was two, but by setting it to four as in this embodiment, the continuity between frames is further improved. The number of overlaps can be an arbitrary integer of 2 or more.

The window operation means is for generating a plurality of frames from one frame, multiplying them by a window function, and then performing an operation of superimposing them while shifting them.

First, the operation of creating four frames from one frame will be described. In FIG. 1A, from the system bus 50, the data resulting from the inverse Fourier exchange is C
It is sent from PU150 (see Fig. 2). The flow of this data corresponds to the flow from the inverse Fourier exchange means 14 to the window operation means 16 in FIG. Now, returning to FIG. 1A, the data for one frame sent via the bus 50 is stored in the input buffer 54. Here, it is assumed that one frame is composed of N words. The input buffer 54 is a so-called double buffer and is composed of a buffer 54a and a buffer 54b. This is to save the data by writing to the other buffer while reading from the one buffer.

The data stored in the buffer 54 is read according to the Xran read address signal. The Xran read address signal is generated by the circuit of FIG. 1B. N for processing
The counter 70 receives the processing clock and receives 0, 1, 2, ... N-2, N
-1,0,1,2 ... and its output 70a are changed. Here, this processing clock must be I (overlap count) times or more as fast as the output D / A clock. The processing N counter 70 outputs 7 when changing from N-1 to 0.
Carry out from 0b. Upon receiving this carry, the random number generator 76 generates a random number, and the τ register 78 holds the random number. The output of the τ register 78 is input to the second adder 82.

On the other hand, the output of the processing N counter 70 is inputted to the first adder 80, and the output thereof is given to the other input of the second adder 82. It should be noted that both the adders 80 and 82 return to 0 and perform addition when the addition result exceeds N-1. Therefore, from the output of the second adder 82, the address of N words is output in synchronization with the processing clock, with the random number of the random number generator 76 as the leading address. Since four frames of data are now obtained based on one frame of data, the above operation is repeated four times. Then, based on the above address, the window operation is performed while shifting each frame read from the input buffer by 1/4 frame.

By the way, in the reading as described above, a certain regularity is brought about. That is, the read start address
If Add _i , in the above case, Add _i = τ _i , and the start address is randomly selected. However, in the window operation, each frame is shifted by N / 4 and overlapped (when the number of overlaps I is 4). Therefore, if this deviation is taken into consideration, the effective start address Add _i ′ becomes Add _i ′ = τ _i- (N / 4) (i-1), and there are some restrictions on how to select the start address. Will bring about sex.

Therefore, in this embodiment, the overlap counter
72 and shifter 74 are provided. The overlap counter 72 operates by receiving a carry from the processing N counter 70. If the number of overlaps is I, then 0,1,2, ... I
The count is repeated -2, I-1,0,1,2 ... to show how many times the current overlap is. In this example, 4
Since the number of overlaps is 0, 1, 2,
The count is repeated 3, 0, 1, 2. The output of the overlap counter 72 is given to the shifter 74. Shifter 74
Is to multiply a given number by N / 4.

Specifically, when N = 2 ⁿ and I = 2 ^m , the shifter 74 is
It shifts left by m bits. Since the operation result is given to the other input of the first adder 80, Xr
The read start address is finally expressed by the following equation.

Add _i = τ _i + (N / I) (i-1) Therefore, when the frames obtained in this way are overlapped, the effective start address Add _i ′ becomes Add _i ′ = τ _i , Can be completely randomized.

Next, an operation of multiplying the data read from the input buffer 54 as described above by a window function and superimposing them while shifting them by N / 4 will be described. For the concept of superposition, see FIG. In order to perform such superposition, the circuits of FIGS. 1A and 1B are used.

First, the data read from the buffer 54 is multiplied by the multiplier 58.
, The data of the W table 56 is multiplied. W
In the table 56, discrete window function values are stored in association with 0 to N words. Therefore, the windowed data is output from the multiplier 58.

Next, this data is shifted by N / 4 for each frame and added. In this embodiment, this is realized by using the intermediate buffer 60 in order to simplify the circuit.
FIG. 3 illustrates the operation. In this figure, for convenience of explanation, the window function is shown as a triangle function. Also, it is assumed that time elapses in the order of A, B, C ... H, and each state A, B, C ... H indicates N words.

As can be seen from this drawing, the output buffer write enable signal (see FIGS. 1A and 1B) is used to sequentially write the calculated data to the output buffer 66. Then, for the data that has been output in the previous state, an addition prohibition signal is issued (see FIG. 1A and B), paying particular attention to AND62), and only new data is added to prepare the next addition data. Are doing The output buffer 66 is a double buffer and is composed of a buffer 66a and a buffer 66b. That is, when data is being written in one of the buffers, the written data in the other buffer is sequentially read and given to the D / A converter 18 (see FIG. 4).

In the above window operation, the following window function W (t) was used in this embodiment.

In what takes the form of, what is called Hanning Window, that is,
Those in which a ₀ = 0.5, a ₁ = 0.5, (R = 1).

What is called Blackman Window, that is, a ₀ = 0.42, a ₁ = 0.5, a ₂ = 0.08, (R = 2).

What is called Blackman-Harris Window, that is, a ₀ = 0.35875, a ₁ = 0.48829, a ₂ = 0.14128, a ₃ = 0.01168, (R = 3).

What is called Nuttall Window, that is, a ₀ = 0.3635819, a ₁ = 0.4891775, a ₂ = 0.1365995, a ₃ =
What is 0.0106411, (R = 3).

None of the window functions described above includes a component having an order that is an integer multiple of the number of overlaps I (4 times in this embodiment). Therefore, no extra amplitude component is introduced into the waveforms superimposed by the window operation.

FIG. 7A shows an output when a direct current is input with the conventional half-sine wave as a window function and the number of overlaps being 2.
Apparently, the ripple component is generated.

FIG. 7B shows an output when a direct current is input using the Hanning Window with the number of overlaps being 4. It can be seen that direct current is output as it is.

FIG. 8A shows the output when an alternating current with a constant amplitude is input under the same conditions as in FIG. 7A. Again, it can be seen that the envelope is wavy, resulting in an extra amplitude component.

FIG. 8B shows the output when an alternating current of constant amplitude is input under the same conditions as in FIG. 7B. You can see that the input alternating current is output as it is.

It should be noted that in the above-described embodiment, a component which does not include a component of an order which is an integral multiple of the number of overlaps I is used. However, such a component is smaller than other order components,
Even if you use a window function that can be regarded as 0,
The same effect can be obtained.

Also, the number of overlaps has been described as 4, but this number can be arbitrarily selected.

Next, the continuation of the spectrum when the window operation is performed by each of the windows 1 to 3 will be described. By operating the window
The line spectra are continuous spectra because the individual line spectra are broadened. This way of spreading
It depends on the window function.

FIG. 9A shows the spread of one line spectrum when the Blackman-Harris Window is used. As is clear from the comparison with the case of the half-sine wave in FIG. 9C, it can be seen that the side lobe is low and the dynamic range can be wide. High side lobes, such as half-sine waves, do not allow this to be achieved if the adjacent spectrum is small.

FIG. 9B shows the spread of one line spectrum when the Hanning Window is used. In this case, the main lobe is thin and the resolution is excellent.

The Blackman Window has the eclectic characteristic that the maximum side lobe is as low as -58dB and the resolution is relatively good.

The Nuttall Window has a characteristic that the maximum side lobe is as low as -98 dB and the resolution is superior to the Blackman-Harris Window.

In particular, the above-mentioned characteristics are remarkably exhibited in a region where no reference exists. This is clear when considering the rectangular end points when a signal having a rectangular spectrum is input to the window operating device.

In Fig. 10A, in the case of Blackman-Harris Window,
FIG. B shows the case of Hanning Window, and FIG. 10C shows the case of half-sine wave. In the case of the half-sine wave, the side lobe effect extends to a considerably low frequency. In the vibration test, since the acceleration is controlled, the increase of the acceleration in the low frequency range causes a problem that the absolute value of the required displacement becomes very large.

As described above, each window has different characteristics, so it is preferable to select and use a window to be used from the viewpoint of dynamic range, resolution, and the like. To achieve this, first
In the circuit of FIG. A, a plurality of W tables 56 may be provided, the required window function values may be stored in each table, and may be switched and output by a multiplexer or the like.

Instead of each of the window functions illustrated above, one substantially equivalent thereto can be used. For example, in order to eliminate the amplitude change due to the window operation, a product multiplied by a predetermined coefficient may be used. Further, even if there is a slight difference in coefficient value, it is possible to use one that produces substantially the same effect.

[Advantage of the Invention] The vibration control device according to the first aspect has a window function of W (t) = 0.5 + 0.5 · cos ((2π / T)
It is characterized by using a material substantially equivalent to t).
Therefore, as compared with the one using the half-sine wave, the dynamic range can be increased without lowering the resolution.

The vibration control device according to claim 2 has a window function of W (t) = 0.42 + 0.5 · cos ((2π / T) t) + 0.08 · cos ((4
It is characterized by using a material substantially equivalent to π / T) t).
Therefore, the dynamic range can be made larger than that of the first aspect.

The vibration control device according to claim 3 has, as a window function, W (t) = 0.35875 + 0.48829 · cos ((2π / T) t) + 0.14128 · cos ((4π / T) t) +0.01168. It is characterized in that a material substantially equivalent to cos ((6π / T) t) is used.
Therefore, an extremely large dynamic range can be taken as compared with the one using the half-sine wave.

The vibration control device according to claim 4 has, as a window function, W (t) = 0.3635819 + 0.4891775 · cos (2π / Tt) + 0.1365995 · cos ((4π / T) t) + 0.0106411 · cos ( It is characterized by using a material substantially equivalent to (6π / T) t).
Similar to the third aspect, a large dynamic range can be adopted and, in addition, the resolution is good.

The vibration control device according to a fifth aspect switches two or more window functions among the window functions according to the first to fourth aspects, and selects and uses one. Therefore, the window function can be switched and used according to the test purpose.

[Brief description of drawings]

1A and 1B are block diagrams of window operating means according to an embodiment of the present invention, and FIG. 2 shows a case where a part of the functions of the vibration control device according to the embodiment is configured by using a CPU. Block diagram, FIG. 3 is a diagram for explaining the operation of FIGS. 1A and 1B, FIG. 4 is a block diagram showing a general vibration control device, and FIGS. 5 and 6 are window operations. 7A is a diagram showing ripples that occur when a sine half wave is used as a window function for a DC input, and FIG. 7B is a Hanning Window for a DC input. FIG. 8A is a diagram showing an output when used as a function, and FIG. 8A is a diagram showing an output when a half-sine wave is used as a window function with respect to an AC input.
Figure B shows the output when a Hanning Window is used as the window function for AC input, and Figure 9A shows Blackman-Har.
FIG. 9B is a diagram showing the spread of the line spectrum when the ris Window is used, FIG. 9B is a diagram showing the spread of the line spectrum when the Hanning Window is used, and FIG. 9C is a line spectrum when the half sine wave is used. Figure 10A shows the spread of
FIG. 10B is a diagram showing the spread of the rectangular spectrum edge when the Blackman-Harris Window is used.
FIG. 10 is a diagram showing the spread of the rectangular spectrum end when w is used, and FIG. 10C is a diagram showing the spread of the rectangular spectrum end when using the sine half-wave. 2 ... Vibration generator 4 ... Specimen 6 ... Accelerometer 8 ... A / D converter 10 ... Fourier transform means 12 ... Control calculation means 14 ... Inverse Fourier exchange means 16 ... Window operation means 18 ...... D / A converter

Claims (5)

[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, control operation means for comparing the response spectrum with a target spectrum and obtaining a drive spectrum, and giving a random phase to the drive spectrum After that, an inverse Fourier exchange means for converting into a digital signal of the time function, a predetermined number N of words of the time function digital signal are set as one frame, and the digital signal of the one frame is placed in a storage means having a cyclic action. , A plurality of frames are generated by changing the extraction start position, and each frame is multiplied by the window function data, and then each frame is superposed with a shift, and the window operation means and the output from the window operation means are analog signals. Vibration control with a D / A converter In the device, a window function W (t) in the windowing unit, W (t) = 0.5 + 0.5 · cos ((2π / T)
A vibration control device, which is substantially equivalent to t). Note that T is the time length of one frame. 2. The vibration control device according to claim 1, wherein a window function substantially equivalent to the following window function is used instead of the window function. W (t) = 0.42 + 0.5 · cos ((2π / T)
t) + 0.08 · cos ((4π / T) t) 3. The vibration control device according to claim 1, wherein a window function substantially equivalent to the following window function is used instead of the window function. W (t) = 0.35875 + 0.48829.cos
((2π / T) t) + 0.14128 · cos ((4π / T) t) + 0.01168 · cos ((6π / T) t) 4. The vibration control device according to claim 1, wherein a window function substantially equivalent to the following window function is used instead of the window function. W (t) = 0.3635819 + 0.4891775 · cos ((2π / T) t) + 0.1365995 · cos ((4π / T) t) + 0.0106411 · cos ((6π / T) t) 5. 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, control operation means for comparing the response spectrum with a target spectrum and obtaining a drive spectrum, and giving a random phase to the drive spectrum After that, an inverse Fourier exchange means for converting into a digital signal of the time function, a predetermined number N of words of the time function digital signal are set as one frame, and the digital signal of the one frame is placed in a storage means having a cyclic action. , By changing the extraction start position, multiple frames are generated, and after each frame is multiplied by the window function data, the window operation unit that superimposes each frame while shifting it, and the output from the window operation unit is converted into an analog signal. Vibration control provided with a D / A converter for converting and giving to the vibration generator In the device, a window function W (t) in the window operating means according to claim 1,
Among the window functions described in 3 and 4, 2 or 3 or more window functions are switched and used.