SU1657996A1 - Low-frequency shaker - Google Patents

Abstract

The invention relates to vibration testing equipment, in particular, to low-frequency oscillatory stands for testing seismometric equipment in the frequency range from 0.01 to 20 Hz. The purpose of the invention is to improve the accuracy of vibration reproduction by introducing compensation for portable random seismic vibrations of the base. This is achieved by the fact that an accelerometer 9 mounted on base 3, a correction unit 10 and a summation unit 6 are inserted into the low-frequency shaker. 1 Il.

Description

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The invention relates to vibration testing equipment, namely, low-frequency oscillatory test benches for seismometric equipment in the frequency range from 0.01 to 20 Hz.

The purpose of the invention is to improve the accuracy of oscillation reproduction by reducing the measurement error from random seismic vibrations of the foundation.

The drawing shows a block diagram of a low-frequency vibration stand.

The stand contains a movable system 1 connected with a parallelogram mechanism 2 with a base 3, a 4 oscillation exciter, a vibrometer 5, a summation unit 6, a generator 7, an amplifier 8, an accelerometer 9 and a correction unit 10. The vibrometer 5, which is made in the form of a capacitive displacement sensor, the summation unit 6, the amplifier 8 and the exciter exciter 4 form a system for automatically controlling the position of the moving system.

Stand raboatt as follows.

When a sinusoidal voltage is applied from the output of the generator 7 to the input of the amplifier 8, and then to the exciter 4 exciter, the latter creates a force that moves the moving vibrator system according to the law specified by the generator 7. This movement is measured by the vibrometer 5, the output of which through the summation unit 6 is fed to the second input of the amplifier 8, subtracting from the signal of the generator 7. Thus, the movements of the signal set by the bench are synchronized. Along with reproducible vibrations, the base relative to the mobile system performs random seismic vibrations. These movements are measured by the vibrometer 5, which leads to reproduction errors. In order to eliminate these errors, compensation was introduced for snooping seismic waveforms by measuring them with a broadband accelerometer 9 and then subtracting them from the signal of the vibrometer 5.

To eliminate the error due to the non-uniformity of the amplitude-frequency characteristic of the vibration stand, the transfer function of which

Wr (p) -, -, -

T p2 + 2 Тs Tc p + 1

de Ks - stand transfer ratio; Tc - constant stand time;

Јc is the attenuation coefficient of the stand; the characteristic of the broadband accelerometer 9 is corrected with the power of the correction unit with the transfer function

WK (P) - 5-

Tc + 2 s, Tc p + 1

where Kk is the accelerometer transmission coefficient, which is selected when setting up the compensation system

The precondition is a dependency.

  KKKZ / KV,

where K is the accelerometer transfer coefficient 9;

Kp is the conversion factor of the vibrometer 5.

Thus, the proposed low-frequency vibratory stand allows to increase the accuracy of reproduction of vibrations.

Claims (1)

Invention Formula A low-frequency vibration stand containing a base and a moving system connected by a parallelogram mechanism, a generator connected in series, an amplifier and a vibration exciter, a vibrometer mounted on the moving system, characterized in that it is equipped with an accelerometer mounted on the base The axis of its sensitivity and the direction of movement of the movable system are parallel, with a correction unit connected to the outputs of the accelerometer, and the unit summation, the first input of which is connected to the output of the vibrometer, the second input to the output of the correction unit, and the output to the third input of the amplifier.