SU862018A1 - Method of forming random wide-band vibration spectrum - Google Patents

Description

The invention relates to a test technique, in particular to methods of forming a spectrum of random broadband vibrations, and can be used in mechanical engineering. A known method of forming a spectrum of random broadband vibrations in which sequentially form narrowband random signals, adjust the level in each policy, memorize and reproduce on a vibrating stand 1. The disadvantage of the method is that during playback only one dispersion band is adjusted to the vibrosten, while the remaining frequency bands are supplied unregulated. Moreover, after adjusting to the required level, they do not take into account the shape of the spectrum, which significantly reduces the accuracy of spectrum formation The closest to the proposed invention to the technical essence is a method of forming a spectrum of random broadband vibrations, which consists in the fact that using narrowband s filters posledovatelftQ formed narrowband random uncorrelated signals of which are fed to .vibrostend with poms tsyu feedback signal level is adjusted in accordance with a predetermined dispersion value in .Each narrow band signals stored adjusted, summed and reproduced on a shaker C2. The method allows vibrations to be excited over all frequency adjusted bands at the same time; however, when forming a spectrum of a complex shape, only the dispersion control in each band significantly reduces the accuracy of spectrum formation, so Kajc does not take into account the shape of the spectrum. The aim of the invention is to improve the accuracy of shaping the spectrum of random broadband vibrations. This is achieved by first adjusting the level of the first group of signals with nonoverlapping frequency bands by dispersion and adjusting the levels of the signals adjusted according to dispersion in accordance with the ratio c ,,) Г - и before adjustment. . , q -riw "W-i (A) avu" J-t

where is the average spectral density in the i -th frequency and the frequency A is the spectral density

signal input filters; - gain factor i

forming channel; Jj (u;) - frequency response of the lth Uekopolo filter

{L; - frequency response of the vibrostand at the middle frequency of the 1st frequency band. Then, the same adjustment and correction of the levels of the second group of signals with nonoverlapping frequency bands is carried out.

The drawing shows the block diagram of the device that implements the proposed method.

The device contains a white noise generator 1, a tunable filter 2, forming frequency bands in series, a level adjustment unit 3, a vibration table 4, a switch 5, a memory unit 6.

The essence of the method is as follows.

When sequentially forming the frequency bands, the required spectral density at the input of the vibrostand can be represented as

, (u;) Aec (. (iU) 3, (I) /

where A is the spectral density of the signal at the input of the filters C, is the gain of the i-th

forming channel; NW, (UJ) - Frequency response 1 -f-o narrowband filter

cfl-. - frequency response of the vibrostand at the middle frequency of the i -th band: frequencies.

Polygean functions that approximate GT. (W) orthogonal, the coefficients Ci can be determined from

- 6irCV; AuJ) olu;

l W1

---) (one)

(,.

 A (f4wi (4) au)

| 4- ...

lU

where Gi is the average spectral density in the 1st frequency band,

The device that implements the method works as follows.

The first stage is that the formed frequency bands are divided into two groups with nonoverlapping frequencies in each group, the Even Hoviepa are assigned. the bands of one group, and the odd ones - frequency bands of the other.

In each group of bands, the signal level is adjusted in accordance with the desired value of the dispersion; since the frequencies are non-overlapping, then at that stage the adjustment at this stage satisfies one of the conditions of the orthogonality of the generated signals.

The second stage involves adjusting the gain of the adjusted band in accordance with the expression 0

l in, -itl), C-i -

H -.

) (L,.

0} l

Where the meanings are the same as above. For this, the value of the gain adjusted by the dispersion of the band is multiplied by the value C obtained from relation (2). The adjusted gain is set in adjustment block 3 and the signal level in the band is adjusted again. By the very SAMEL 1, the orthogonality conditions for the generated signals are fulfilled, From - t the corrected signal is supplied to memory block 6. After the same, everything is adjusted

0, the frequency bands that I received from the signal of the white noise generator 1 using a tunable filter 2 simultaneously read the signals of all the bands from the memory block 6 and serve to

5 shakers 4 with power switch 5. The invention improves the accuracy of forming a spectrum of random broadband vibrations.

Claims (2)

The invention of the method of forming a spectrum of random broadband vibrations, is that using narrow-band filters sequentially form uncorrelated narrow-band random signals, each of which 5 is fed to a shaker, with the help of feedback, they adjust the level of the signals in accordance with a given dispersion value in each narrow band, the adjusted signals are memorized, summed and reproduced on a vibrostend, characterized in that, in order to improve the accuracy of | reproduction of the spectrum of random vibrations First, the level of the first group of signals with non-overlapping frequency bands is adjusted according to Persian's dis5 and, before recording, they adjust the levels of the signals adjusted by the dispersion in accordance with the ratio ) cf. uJi, uJ-1 de Ctf - average spectral density in the second frequency band, And the spectral density of the signal at the input of filters C, - - gain factor of the i-th forming channel 9 (/ (W) - frequency response of the 1st narrowband filter (L; - frequency response of the vibrostand at the middle frequency of the 4th frequency band; then the same adjustment and correction of the levels of the second group of signals with nonoverlapping frequency bands is carried out,  Sources of information: taken into account in the examination 1, USSR Copyright Certificate o 504957, cl. G 01.M 7/00, 1975. 2. USSR author's certificate on application 2651800/28, cl. G 01 M 7/00, 1978 (prototype), 7