SU732715A1 - Method for testing products with sinusoidal vibrations - Google Patents

Description

where iA), Wit-TeKymafl, the frequency of the sinusoidal signal is programmed

0 is the natural frequency of the vibrating system;

P - signal level with frequency ttJ j; K - empirical coefficient (K

-0,1);

  additional signal level.

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

The device contains a generator 1, which is connected to the input of the regulator 2, connected to the input of the summation unit 3, the amplifier 4, the exciter 5 exciter, the fixture b for fixing the test product 7, the vibrator 8 mounted on the fixture 6, the amplifier 9, the first harmonic extractor 10 , comparison unit 11, software master 12. The circuit elements 1 through 12 are included in the first harmonic control loop. The vibrator 13, mounted on the tested product 7, the amplifier 14, the 15-fold harmonic selector, the phase shifter 16, the controller 17 and the summation block 3 form the control circuit of the selected multiple harmonics.

The method is implemented as follows. The first harmonic control loop, which is the main sinusoidal signal, works as follows.

The signal of the vibration converter 8, amplified by the amplifier 9, is fed to the input of the first harmonic extractor 10, is compared with the software in the comparison unit 11 and is fed to the input of the regulator 2, which controls the signal level of the generator 1, performs control in accordance with the program. But because of the bilinear characteristic of the fixture b for fastening the products 7 and the nonlinearity of the characteristics of the exciter 5, the signals taken from the vibration transducers 8 and 13 contain multiple components of the sinusoidal signal. Multiple harmonics can exceed the level of the main signal and distort the specified level of vibration.

To improve the accuracy of vibration tests, an additional circuit was introduced, which forms a correction signal of a certain phase 1, frequency and level. The suppression of multiple harmonics, according to the invention, occurs due to the nonlinear interaction of multiple harmonics with a correction signal, which is obtained by extracting any multiple harmonics from the vibration spectrum. The signal of the vibrator 13, amplified by the amplifier 14, is fed to a 15-fold harmonic selector, which forms the signal frequency. The correction signal phase is established experimentally, by minimizing the signal at the output of the selector 15. This

the minimization is carried out with a phase shifter 16. The required phase (tpj) is determined by the relation:

 G -.

-pagf

where K), K a are the rigidity of the sections of the characteristic of the elastic force of the device for fastening the product during its stretching and compression, respectively.

The controller 17 sets the level of the correction signal in accordance with the expression:

R

where oji is the current, the frequency of the sinusoidal signal is programmable;

We are the natural frequency of the vibrating system;

Pi is the signal level with the frequency CO i; K is an empirical coefficient (K O, I); PJ-level additional signal. The correction signal, modified in frequency, phase and level, is inputted to the driver with 5 oscillations. In this case, the system oscillates as linear. The correction process can be considered as a forced linearization of the characteristics of the system.

It is established that the adjustment of the correction contour on one of a multiple harmonic provides for the suppression of the remaining multiple harmonics. After the multiples are suppressed, oscillator 1 goes into frequency scanning mode (t) (i}.

Claims (2)

1. Abramovich S.V. Sat. Automation of research processes in the field of mechanical properties of materials and strength of structural elements, Kiev, Institute of Problems of Strength of the Academy of Sciences of the Ukrainian SSR, 1976. 2. Lykova I.M. Sat. “Vibrostables and pathogens, Kiev,“ Knowledge, 1969 (prototype).