JPH0442615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration testing device, and more specifically, to a vibration testing device for verifying reliability of a specimen by shaking the specimen.

FIG. 1 schematically shows a typical configuration of a conventional vibration testing apparatus, in which a piston rod 3 of a piston 4 is connected to a vibration table 2 on which a specimen 1 is mounted, and the piston 4 is connected to a cylinder tube 5. is inserted into. A control valve 6 attached to the cylinder tube 5 supplies oil for driving the piston 4 to the cylinder tube 5 . The cylinder tube 5 is fixedly attached to a mounting leg 8 erected on a foundation 7. The configuration consisting of the piston 4, cylinder tube 5, and control valve 6 will be referred to as a vibration device 9. With this configuration, driving oil to which a predetermined oil pressure is applied flows into the cylinder tube 5 via the control valve 6. Cylinder tube 5
The piston 4 is a so-called double-acting type, and when oil flows below the piston 4 by the control valve 6, the piston 4 moves upward, and when oil flows above the piston 4 due to the operation of the control valve 6, Piston 4 moves downward. This movement of the piston 4 is transmitted to the vibration table 2 via the piston rod 3, and gives vibration to the specimen 1 attached to the vibration table 2.

Since the conventional vibration test apparatus is configured as described above, a load equal to the total weight of the specimen 1, the vibration table 2, the piston rod 3, and the piston 4 presses down on the piston 4. It is necessary to constantly apply enough pressure to the oil to withstand this load. Therefore, the maximum excitation force Fmax of the conventional device is subject to the limit expressed by equation (1).

Fmax=P/A-(W _O +W _T +W _R +W _P ) ...(1) However, P: Pressure of driving oil A: Pressure-receiving area of piston 4 W _O : Weight of specimen 1 W _T : Vibration table Weight of 2 W _R : Weight of piston rod 3 W _P : Weight of piston 4 As is clear from equation (1), the conventional vibration test apparatus can When the maximum excitation force is large, the maximum excitation force decreases. To illustrate this phenomenon with a concrete example, for example, the excitation capacity P/A of the piston 4 is ±3 tons, and the total weight of the moving parts of the specimen 1, the excitation table 2, the piston rod 3, and the piston 4 is 1 ton. Assuming that, the upward excitation force of this vibration test device is
It will be 2 tons. Therefore, the actual excitation force is ±
This means that the amount has decreased from 3 tons to ±2 tons.

That is, the conventional vibration testing apparatus has a drawback that the maximum excitation force decreases when the weight of the movable part is large.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional apparatus, and an object of the present invention is to provide a vibration testing apparatus that can efficiently utilize the excitation force of an excitation apparatus.

Hereinafter, one embodiment of this invention shown in FIGS. 2 and 3 will be described. The same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and their explanation will be omitted.

In FIG. 2, a pair of vibration devices 9 are provided on the left and right sides of the vibration table 2, but this is not a particular difference from the conventional device. In FIG. 3, a preamplifier 10 amplifies a command signal for operating the vibration testing apparatus, and a displacement meter 1 detects the displacement of the vibration table 2 and provides negative feedback to the preamplifier 10.
1 is provided. However, the command signal referred to here is a time history waveform having an amplitude proportional to the displacement of the vibration table. The control valve 6 is driven by the output signal from the preamplifier 10. In addition, the front stage amplifier 10
An amplifier 13 and a load compensator 14 are included in the low-pass wave generator 12 that passes only the low frequency components of the output signal.
Connect sequentially. The load compensator 14 is a vertical driving means using hydraulic pressure or pneumatic pressure, and uses an output signal from the amplifier 13 to drive the vibration table 2.
is statically driven upwards. Reference numeral 15 denotes a vibration table mechanical system comprising a specimen 1, a vibration table 2, and the like.

Next, the operation will be explained. The output signal of the displacement meter 11 includes a displacement signal with respect to the foundation 7 of the vibration table 2 pushed down by the static load caused by the weight of the specimen 1, the vibration table 2, the piston rod 3, etc., that is, a DC signal. This DC signal is negatively fed back to the preamplifier 10. Of the output signal of the preamplifier 10, the DC signal component is selectively converted by the low-pass wave generator 12, and then passed to the amplifier 1.
3 and input to the load compensator 14.
The load compensator 14 pushes the vibration table 1 upward in accordance with this signal, and returns the vibration table 1, which has been pushed down by the static load, to a neutral position. At the same time, the output signal of the displacement meter 11 acts on the vibration device 9 as a displacement feedback, and acts to match the command signal waveform with the motion displacement of the vibration table 2.

The effects described above will be explained below based on the gains of each component. Now, the gain of the preamplifier 10 which inputs the command signal and outputs the drive voltage to the control valve 6 is _G1 , and the excitation table 2 receives the drive voltage as input.
G ₂ is the gain formed by the control valve 6 and the excitation device 9, which outputs the driving force to G ₃ is the gain formed by the amplifier 12, the amplifier 13, and the load compensator 14, and the gain of the vibration table mechanical system 15, which inputs the driving force for the vibration table 2 and outputs the displacement of the vibration table 2, is G3. G ₄ , and the gain of the displacement meter 11 which inputs the displacement of the vibration table 2 and outputs the negative feedback signal to the preamplifier 10 is G ₅ , the gain of the forward path is G ₁・G ₄・(G ₂ +
G ₃ ), the gain of the backward path is G ₅ , and the overall gain G when the command signal is input and the displacement of the vibration table 2 is output is expressed by the following equation.

G=G ₁・G ₄・(G ₂ +G ₃ )/1+G ₁・G ₄・G ₅ (G ₂ +G ₃ )…
(2a) Here, assuming that the cutoff frequency of the low-pass transducer 12 is set lower than the frequency range of vibrations used for normal vibration tests, there are cases in which the cutoff frequency is higher than this cutoff frequency, that is, dynamic The operation will be explained for each frequency lower than the frequency, that is, the static case. Note that the above-mentioned cutoff frequency is specifically determined as follows.
For example, in a vibration test that reproduces earthquake waves, the predominant frequency of the earthquake displacement waveform is in the frequency range of 0.5 [Hz] to 10 [Hz], so the cutoff frequency is set to a lower frequency, for example 0.2 [Hz].

First, at frequencies higher than the above cutoff frequency,
Since the gain of the low-pass wave generator 12 becomes small, the gain G ₃ composed of the low-pass wave generator 12, the amplifier 13, and the load compensator 14 becomes small. Therefore, the overall gain G in this case is G=G ₁・G ₄・(G ₂ +G ₃ )/1+G ₁・G ₄・G ₅ (G ₂
＋G ₃ )≒G ₁・G ₂・G ₄ /1＋G ₁・G ₂・G ₄・G ₅ …(2b) Therefore, it is almost unaffected by the gain G ₃ , and the vibration test equipment is a low-pass wave generator. 12, amplifier 1
3. The operation is substantially the same as that of the structure without the load compensator 14. That is, in the frequency range used in normal vibration testing, this vibration testing apparatus does not suffer from the adverse effects of being equipped with the load compensator 14 or the like.

Next, in the static case, ie, at a frequency lower than the cutoff frequency, the overall gain G is given by equation (2a) as described above.

Now, this invention was made in order to eliminate the drawback that the maximum excitation force is reduced due to static loads from the specimen 1, the excitation table 2, the piston rod 3, etc. acting on the excitation device 9. Therefore, the load acting on the vibrating device 9 at a frequency lower than the above-mentioned cut-off frequency, that is, when it is close to static, will be considered. If the output voltage of the preamplifier 10 is X, the driving force acting on the shaking table 2 from the vibration device 9 is y ₂ , and the driving force acting on the shaking table 2 from the load compensator 14 is y ₃ . , x, y ₂ , y ₃ can be expressed by the following equation.

y ₂ = G ₂ x y ₃ = G ₃ x …(3) On the other hand, specimen 1, vibration table 2, piston rod 3
Let W be the total weight of moving parts such as
There is a relationship between y ₂ and y ₃ as shown in the following equation.

y ₂ +y ₃ =W...(4) Therefore, the following equation is derived from equations (3) and (4).

y ₂ =W/1+G ₃ /G ₂ Here, since W is constant, when G ₃ becomes larger than G ₂ , the value of y ₂ becomes smaller. This y ₂ is
Since this is the driving force of the vibration device 9 against the vibration table 2, in other words, it is nothing but a static load that the vibration device 9 receives from movable parts such as the specimen 1, the vibration table 2, and the piston rod 3. Therefore, G3 is G2
By setting it larger than do not. In other words, the present invention compensates for this by generating an upward force equivalent to the total weight of the specimen 1, the vibration table 2, the piston rod 3, and the piston 4, which are statically movable parts. In general, it operates in the same way as the conventional device, so it is possible to avoid a decrease in the excitation force due to an increase in the weight of the movable parts.

As explained above, the present invention can reduce the static load applied to the vibrating device at low cost by using the load compensating means, and can efficiently utilize the vibrating force.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a conventional device, FIG. 2 is a schematic front view of an embodiment of the present invention, and FIG. 3 is a system diagram. DESCRIPTION OF SYMBOLS 1... Specimen, 2... Vibration table, 3... Piston rod, 6... Control valve, 7... Foundation, 9... Vibration device, 10... Front stage amplifier, 11... Displacement meter, 1
2...Low pass wave generator, 13...Amplifier, 14...
...Load compensator, 15... Vibration table mechanical system. In addition,
In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An amplifier that amplifies a command signal for operating a vibration testing device, a control valve driven by the output signal of this amplifier, and an excitation device to which this control valve is operatively attached. , a vibration test device including a vibration table driven by the vibration device, a displacement meter that detects vibration displacement of the entire vibration table with respect to the foundation and provides negative feedback to the amplifier; A vibration test comprising: a low-pass waver that passes a low-frequency component of an output signal; and a load compensator that drives the vibration table according to the output signal from the low-pass waver. Device. 2. The vibration testing device according to claim 1, wherein the low-frequency component passing through the low-pass transducer is a direct current component.