SU991384A1 - Vibration stand of self-excited oscillation type - Google Patents

Description

(54) AUTO-VIBRANT VIBROSTAND

 The invention relates to vibration testing equipment, namely, self-oscillating test benches for seismometric equipment in the range of infra-low frequencies from 0.01 to 20 Hz.

Known resonant shaker, creating vibrations in the frequency range 1 - iOOOO Hz. This stand is a single-degree oscillatory system with an electrodynamic type excitation system. The oscillation frequency of the moving system is set by the generator, the signal from the output of which, after amplification, is fed to the input of the vibration exciter. The vibration amplitude is measured with a Cl microscope.

 However, due to the absence of a system for maintaining the amplitude of vibration when the parameters of the amplifier, vibration amplifier and master oscillator change, for example, from thermal transients and time, the stability of the oscillation amplitude of this stand is negligible.

Known self-oscillating vibration table, which contains a movable system installed in an elastic suspension, a speed sensor, the movable part of which is fixed on the movable system, and the stator on the stand body. The output of the speed sensor through the amplifier is connected to the input of a magnetoelectric or electromagnetic exciter of oscillations. The excitation of harmonic oscillations in such a stand is carried out by positive feedback, containing a speed sensor, an amplifier and an exciter of 2.

The motion of the mobile stand system is described by the equations

15

4 Bh + cf FB;)

mx

(one) )

Fb

mass of the moving system;

where m b s

20 damping coefficient; coefficient of linear stiffness of the elastic suspension; the force created by the excitation of the vibration wave;

25 Qf -, -, - respectively /: inherently the transfer coefficients of the speed sensor, amplifier and exciter;

X - movement of the mobile system of the booth theme. Damping in a vibration stand is largely determined by friction. When it is linearized by the harmonic balance method from equations 11), we obtain the amplitude of self-oscillations where RTR is the strength of friction in the suspension ,; S is the feedback gain. It follows from (2) that when the friction force changes, for example, in the times and the feedback transmission coefficient, due to thermal transients in the winding of the exciter and the scientific research institute and other factors, the amplitude of self-oscillations changes. As a result, errors in the measurement of vibration parameters arise due to the nonstationarity of the amplitude of auto-oscillations. For example, when the frictional force changes by 4%, a corresponding change of 4% in the amplitude of oscillations of the mobile stand system occurs. The antshochosis ratio also occurs when the transmission coefficient of the feedback changes. The aim of the invention is to improve the oscillation reproduction accuracy. The goal is achieved by the fact that the first comparator, the first key, the first integrator, introduced in series in the self-oscillating shaker, containing the speed sensor of the moving part of the shaker installed in elastic supports, and successively connected amplifier and exciter, an adder, a second integrator and an attenuator, a second comparator connected in series, a differentiator, a first selector, a second key and a third integrator, and a source reference voltage, the second selector and the third comparator whose first input is connected to the output of the displacement sensor, the second input to the output of the third integrator and to the second input of the adder, and the output to the second input of the second key, the input of the second selector is connected to the output of the differentiator, and the output of the second the input of the first key, the output of the speed sensor is connected to the input of the second comparator and the input of the attenuator, the output connected to the input of the amplifier, the output of the first integrator is connected to the second input of the first comparator, and the output of the source is Nogo voltage is connected to the second input of the second integrator. An increase in the accuracy of reproducible oscillations in the proposed stand as compared with the known one is achieved with the introduction of automatic control of the transmission coefficient of a positive feedback. In this case, the regulation is carried out proportional to the amplitude of movements of the mobile system of the stand. FIG. 1 shows a functional diagram of the self-oscillating vibrostend; in fig. 2 - stress diagrams showing the work of the stand. The self-oscillating vibration table has a movable part 1 installed in elastic supports 2, a displacement sensor 3, for example a capacitive one, the movable part of which is fixed on the movable stand system and the fixed part on the case. The speed sensor 4 is made electrodynamically so that its coil is mounted on the movable stand system, and the magnetic system is on the case. The vibration table also contains an attenuator 5, amplifier b, the exciter pathogen 7 (electrodynamic), comparators first, third, second 8-10, integrators first, third, second 11 13, keys 14 and 15, adder 16, differentiator 17, selectors 18 and 19 pulses. The reference voltage source 20 can be any, but with adjustable output voltage. FIG. 2 are indicated by the following (.- voltage at the output of the speed sensor 4; voltage at the output of the displacement sensor 3; IR voltage at the output of the comparator 10 j (respectively, the voltage at the output of the differentiator, selector of positive and negative pulses. The stand works in a similar manner. The signal from the output of the speed sensor 4 (-Fig. 2aG through the attenuator and amplifier 6 is fed to the exciter 7. When the conditions of self-excitation, which follows from equations (1), self-oscillations occur in Cdrc-y Kg. Moving CKCieusa by means of a sensor the displacements are converted into an electrical signal (Fig. 2S) and fed to the input of the comparators 8 and 9. Comparator 10 converts the -signal from the speed sensor into square pulses (Fig. 2bj, which, after differentiation using block 17 (Fig. 21) and selections on selectors 18 (Fig. 29) and 19 (Fig. 2e) control the keys 14 and 15. Thus, the keys 14 and 15 are opened when the maxima of the signals from the displacement transducer pass. As a result, the integrators 11 and 12 memorize the amplitude values of the displacements. The adder 16 summarizes these signals and divides the resulting amount in half. From the output of the adder 16, the signal is fed to the input of the integrator 13, where it is compared with the signal of the voltage source 20, and then the difference is integrated and fed to the controlled attenuator mr 5, with which the feedback gain is changed. If for any reason a change in the amplitude of self-oscillations occurred, then a change in the signal occurs at the output of the integrator 13, resulting in the attenuator 5 changing its resistance so that the feedback gain becomes such that at the output of the integrator 13 close to zero value. The use of the amplitude of the integrator 13 in and, with the support of the amplitude of the displacement amplitude makes it possible to create a system with the amplitude of displacements. The use of the amplitude value of displacements in the test bench made it possible to create a system for maintaining the parameters of self-oscillations in the range of infra-low frequencies Q. To estimate the technical and economic efficiency, we use the equations t.2), whence the relative error of the amplitude maintenance has the form p c-f. From (3) it follows that in order to ensure a zero error of the amplitude of self-oscillations, it is necessary to perform the equality ./i a F, where dF, is the increase in the friction force and the initial value of the friction force; Kg is the initial value of the feedback coefficient; dK is the coefficient factor. Feedback and at which the exclusion of the amplitude of self-oscillations occurs. .More detailed calculations; show that the error in maintaining the amplitude of self-oscillations using the proposed technical solution is reduced by more than 5 times. The invention of the Self-oscillating vibration table, contains a speed sensor of the moving part of the vibration table, installed in elastic supports, and a series-connected amplifier and vibration exciter, characterized in that, in order to improve the accuracy of vibration playback, the vibration table contains a series-connected movement sensor of the mobile part of the vibration table, Percla Comparator, Perchl key, first integrator, yummator, second integrator and attenuator, a second comparator connected in series, a differentiator, the first with The selector, the second key and the third integrator, as well as the source of the reference voltage, the second selecto and the third comparator, the first input of which is connected to the output of the displacement transducer, the second input to the output of the third integrator and the second input of the adder, and the output to the second input of the second key, the input of the second selector is connected to the output of the differentiator, and the output is connected to the second input of the first key, the output of the speed sensor is connected to the input of the second comparator and to the input of the attenuator, the output of the amplifier connected to the input, the output of the first integrator connected to the second input of the first comparator, with the output of the voltage source connected to the second input of the second integrator. . Sources of information taken into account in the examination 1. Shkalikov B.C. et al. Measurement of vibration and shock parameters M., Publishing House of Standards, 1980, p. 205-208, 2. Author's testimony of the USSR. 169842, class G 01 M 7/00, 1963 (prototype).

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Claims (1)

The claims of maintaining amplitude have .. that to ensure From (3 I reading the zero error of amplitude, self-oscillations, it is necessary to fulfill the equality ak = where dF _Tp , F _{TP {)} ^K 0 dK ^K o ^dF rP ^r tro, respectively, the increment of the friction force and the initial value of the friction force; initial value of the feedback coefficient; - increment of the feedback coefficient, • at which the error of the amplitude of the self-oscillations is eliminated. A self-oscillating vibrostand containing a speed sensor of the movable part of the vibrostand installed in the elastic supports, and a serially connected amplifier and exciter, characterized in that: in order to increase the accuracy of reproducing vibrations, the vibrostand contains a serially connected displacement sensor of the moving part of the vibrostand, the first comparator, the first key, first integrator, Sum. a mator, a second integrator and an attenuator, a second comparator, a differentiator, a first selector, a second switch and a third integrator, as well as a reference voltage source, a second selector and a third comparator, the first input of which is connected to the output of the displacement sensor, the second input to the output of the third integrator to the second input of the adder, and the output to the second input of the second key, the input of the second selector is connected to the output of the differentiator, and the output to the second input of the first key, the output of the speed sensor is connected to the input of the second of the second comparator and with the attenuator input connected to the amplifier input, the output of the first integrator is connected to the second input of the first comparator, and the output of the reference voltage source is connected to the second input of the second integrator.