JPS60252920A - Waveform corrector for vibration tester - Google Patents

Abstract

PURPOSE:To regenerate a corrected waveform by performing the Fourier transform between an exciting waveform and an answer waveform to calculate a correction spectrum and then performing the inverse Fourier transform after substituting the real part and the imaginary part of each frequency component excluding a DC component for zero and a power square root respectively. CONSTITUTION:An output buffer 4 stores an exciting waveform and a waveform output means 6 reads out the exciting waveform. Then a vibrating base 2 is vibrated by an exciting means 8. The base 2 supplies an answer waveform to an answer waveform input means 12 through an acceleration sensor 10. This answer waveform is supplied to a Fourier transform means 14 together with the exciting waveform for fast Fourier transform. The waveform is sent to a correction spectrum calculation means 16 after transformation. Thus a correction spectrum is calculated from a transmission function. The correction spectrum is sent to a correction spectrum conversion means 18, and a converted correction spectrum is obtained. This spectrum is converted into a corrected waveform by an inverse Fourier transform means 20 and sent to the buffer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention is a vibration testing machine for performing vibration tests on structures, etc., in which the vibration table is adjusted so that the response waveform of the vibration table matches a certain set target waveform. The present invention relates to a waveform correction device that corrects an applied waveform.

(b) Prior Art Generally, in vibration tests, sine wave excitation is sometimes performed under acceleration control. When such a sine wave is input to a shaking table and excited, the acceleration response waveform of the shaking table itself is
The vibration transmission system that includes the specimen causes distortion in the excitation waveform, and the waveform actually applied to the vibration table differs from the intended excitation waveform.

This tendency is particularly noticeable when the frequency of the excitation waveform is low. In order to correct the distortion of the excitation waveform and make the response waveform from the vibration table the desired target waveform, it is necessary to know the transfer function of the vibration transfer system. For this reason, in the prior art, an attempt has been made to input a response waveform to a CPU in real time, calculate the transfer function using fast Fourier transform, and create a new corrected waveform.

(c) Problems to be Solved by the Invention When a response waveform based on a sine wave excitation waveform is imported into a CPU and the excitation waveform is corrected using the fast Fourier transform method, the timing of acquiring the response waveform data is not always constant. Therefore, the waveform corrected by the capture timing does not necessarily start from the zero point. If such a correction waveform is set as is in the output buffer as a waveform memory, a sudden rise phenomenon will occur in the middle of the time-series excitation waveform applied to the shaking table, making it impossible to apply a steady sine wave to the imaging table. . For this reason, a sudden shock is given to the specimen by the vibration test, and the reliability of the data obtained becomes poor.

The present invention solves these conventional problems and makes it possible to sequentially correct the response waveform of the shaking table in real time so that it matches the desired target waveform, and also to make it possible to sequentially correct the corrected sine waveform in time series. The purpose is to create a continuous waveform that can be used to obtain highly reliable vibration test data.

In order to achieve the above-mentioned object, the present invention performs Fourier transform on both the sine wave excitation waveform applied to the vibration table and the response waveform obtained in response to this excitation waveform. , calculate a corrected spectrum from both waveforms after Fourier transform, and apply inverse Fourier transform to this corrected spectrum by replacing the real part of each frequency component excluding the DC component with zero and the imaginary part with the square root of the power. The final corrected waveform is reproduced through conversion.

(E) Example Hereinafter, the present invention will be explained in detail based on an example shown in the drawings.

The figure is a block diagram of the waveform correction device of this embodiment. In the figure, 1V1. A waveform correction device is shown, and 2 is a vibration table of a vibration testing machine to which a specimen is attached. 4 is an output buffer in which the excitation waveform of a sine wave applied to the vibration table 2 is stored; 6 is a waveform output means for reading and outputting the excitation waveform stored in the output sofa 4; 8V'i is from the waveform output means 6; It is an excitation means that vibrates the vibration table 2 with a given excitation waveform, and is composed of, for example, a hydraulic actuator. 10
1 is an acceleration sensor attached to the vibration table 2; 12 is a response waveform input means for inputting a response waveform detected by the acceleration sensor 10 as the vibration table 2 vibrates; 14 is a response waveform provided from the response waveform input means 12; This is a Fourier transform means that performs fast Fourier transform on each of the excitation waveforms stored in the output buffer 4. 16 is Fourier transform means 1
4, a correction spectrum calculation means for calculating a correction spectrum based on the excitation waveform and response waveform subjected to Fourier transformation; 20, each frequency component of the correction spectrum calculated by the correction spectrum calculation means 16, excluding its DC component; This is a corrected spectrum conversion means that replaces the real part of the power with zero and the imaginary part with the square root of the power. Reference numeral 20 denotes an inverse Fourier transform means for fast inverse Fourier transform of the corrected spectrum converted by the corrected spectrum converter 18.

In the waveform correction device 1 having the above configuration, the sine wave excitation waveform f (t) stored in the output buffer 4 is read out by the waveform output means 6 and applied to the excitation means 8 .

The vibration means 8 uses the vibration table 2 based on this vibration waveform f(t).
vibrate. Acceleration accompanying the vibration of the vibration table 2 is detected by the acceleration sensor 10, and a response waveform g(t) of the detection signal is input to the response waveform input means 12. The response waveform g (t) input to the response waveform input means 12 is influenced by the vibration transmission system including the vibration table 2 and the specimen, and the excitation waveform f
It is distorted from (t). The Fourier transform means 14 converts the response waveform g input into the response waveform input means 12.
(t) and the excitation waveform f stored in the output buffer 4
(t) and both waveforms f(t)4g(t
) is fast Fourier transformed. The excitation waveform and response waveform after the Fourier transform are designated as F(ω) and G(ω), respectively.

Excitation waveform F subjected to Fourier transformation by Fourier transformation means 14
(ω) and the response waveform G(ω) are both sent to the corrected spectrum extracting means 16 at the next stage. The correction spectrum calculation means 16 converts the input response waveform G(ω) into an excitation waveform F(ω
), and this results in the transmission IG in the vibration transmission system (
ω) Calculate one series of functions H(ω). That is -51□. , H(
ω). Further, the correction spectrum calculating means 16 divides the excitation waveform G(ω) by the transfer function H(ω) to obtain a correction spectrum F'(ω) for the excitation waveform F(ω).
Calculate. In other words, the knee is F'(ω). The corrected spectrum F'(ω) obtained by IH(ω)j in this way is the excitation waveform F(ω
), but the sine wave starting from zero is not guaranteed. Therefore, the calculated correction spectrum is applied to the correction spectrum conversion means 18 at the next stage. The corrected spectrum conversion means 1B performs the following arithmetic processing on the corrected spectrum F'(ω) given from the corrected spectrum calculation means 16.

First, 0 of the frequency components of the corrected spectrum pr<ω)
Find the square root of the power for each frequency component except for the following DC component. That is, if the real part of the first-order frequency component is Rei and the imaginary part is Imi, then the square root of the power A1
Therefore, Ai=fi-. Then, the corrected spectrum p/(
For each frequency component other than the zero-order DC component of ω), the real parts are all replaced with zeros, and the imaginary parts are replaced with the square root A1 of the power obtained as described above. This operation means that the real part of each frequency component of the Fourier transform corresponds to a cosine wave and the imaginary part corresponds to a sine wave, so while maintaining gain compensation, the cosine wave is removed and converted back to a collection of sine waves. do. The correction spectrum f-1 converted by the correction spectrum conversion means 18 in this way is sent to the Fourier transform means 20, where it is fast inverse Fourier transformed to form a correction waveform f'
(t). This corrected waveform f'(1) is newly set in the output buffer 4. The corrected waveform f' (
Since t) is a sine wave starting from the zero point, the waveform does not fluctuate as it is set. In this way, the output buffer 4 outputs the corrected waveform f'(t) as the output waveform f(t) while being updated successively.

(F) Effect As described above, according to the present invention, both the sine wave excitation waveform applied to the vibration table and the response waveform obtained in response to this excitation waveform are Fourier-transformed, and both waveforms after Fourier transformation are A corrected spectrum is calculated, and the final corrected waveform is obtained by inverse Fourier transform by substituting the real part of each frequency component excluding the DC component with zero and the imaginary part with the square root of the power. I'm trying to reproduce it.

Therefore, correction is made in real time so that the response waveform of the shaking table matches the desired target waveform, and the corrected sinusoidal waveform becomes smooth without sudden rises in time series. Therefore, highly reliable vibration test data can be obtained, which is an excellent practical effect.

[Brief explanation of drawings]

The drawing is a block diagram of a waveform correction device in a vibration testing machine showing an embodiment of the present invention. 1. Waveform correction device, 2. Shaking table, 4. Output buffer, 14. Fourier transform means, 16. Correction spectrum calculation means, 18. Correction spectrum conversion means, 20.
- Inverse Fourier transform means. Applicant: Shimadzu Corporation Agent: Kazuhide Okada, Patent Attorney

Claims (1)

[Claims] (1) An output buffer sofa in which a sine wave excitation waveform applied to the vibration table is stored, a response waveform detected from the vibration table by applying the excitation waveform to the vibration table, and an excitation stored in the output buffer. Fourier transform means that performs Fourier transform on each waveform; correction spectrum calculation means that calculates a correction spectrum based on the excitation waveform and response waveform that have been Fourier transformed by the Fourier transform means; A correction spectrum conversion means for substituting the real part of each frequency component excluding the DC component of the spectrum with zero and the imaginary part with the square root of the power, and an inverse Fourier converter of the correction spectrum converted by the correction spectrum conversion means. 1. A waveform correction device for a vibration testing machine, comprising an inverse Fourier transform means for converting the waveform.