JPS5844359Y2 - vibration testing machine - Google Patents

Description

[Detailed description of the invention] This invention relates to a vibration testing machine equipped with an electro-hydraulic servomechanism.

Figure 1 shows the electro-hydraulic servo mechanism of a conventional vibration testing machine. It is supported by a flotation device, and its side surfaces are supported by, for example, hydrostatic bearings similar to the flotation device in order to restrain the vibrating table 1 so that it coincides with the direction of movement of the hydraulic cylinder 2 that displaces the vibration table 1.

A servo valve 3 controls the direction and flow rate of pressure oil supplied from the hydraulic source 4 to the hydraulic cylinder 2, and the servo valve 3 and the hydraulic cylinder 2 constitute a vibrator.

5 is a displacement signal generator that generates a target displacement value of the vibration table 1 as a voltage signal; 6 is a displacement detector J7 that converts the displacement of the vibration table 1 into a voltage signal; and 8 is an amplifier thereof; 8 is a unit that calculates the sum of the voltage signals. Adder 9 is a servo amplifier for power amplifying the voltage signal.

In the vibration testing machine configured as described above, a command for the displacement of the vibration table 1 is given by the displacement signal generator 5 as a reference input voltage signal Er.

On the other hand, the actual displacement y of the shaking table 1 is detected as a voltage signal Ey by the displacement detector 6, amplified by the amplifier I, fed back to the adder 8, and compared with the reference input voltage signal Er. be done.

The error voltage is transmitted as a control deviation to the servo amplifier 9, where the current is amplified and then sent to the servo valve 3.

This input current causes the servo valve 3 to control the direction and flow rate of the pressure oil supplied from the hydraulic source 4 to the hydraulic cylinder 2, so the vibration table 1 is moved in a direction that reduces the control deviation.

Thus, if the response of the servo system is sufficiently fast and the control deviation can always be kept sufficiently small, the displacement of the vibration table 1 will practically match the target value, and the vibration table 1 will be moved according to the command.

However, in the vibration testing machine described above, the control system constitutes a closed loop control system.

In order to speed up the response of this closed-loop control system, it is necessary to increase the loop gain, but generally speaking, increasing the loop gain deteriorates stability and may cause self-excited vibration.

In order to improve the stability, it is conceivable to use voltage signals corresponding to the displacement, velocity and acceleration of the shaking table as reference input signals.

To achieve this, conventionally, the displacement, velocity, and acceleration of the shaking table are determined by differential or integral operation of an electrical arithmetic circuit based on a target value of one of the displacement, velocity, and acceleration of the shaking table. I am trying to output it.

However, in this method, noise and trist are generated due to differential or integral operations in the arithmetic circuit, causing distortion in the waveform itself.

Therefore, there was a drawback that control performance was not improved.

The present invention has been developed based on the above-mentioned considerations, and aims to provide a vibration testing machine that has the ability to localize a vibration table with respect to a target value, and has good stability and high responsiveness as a control system.

The feature of this invention is the displacement of the shaking table.

a feedback circuit that feeds back one or more elements of velocity and acceleration to the input side;
an adder that adds the input signal and the feedback element;
Equipped with an electro-hydraulic servo mechanism consisting of a servo amplifier that increases the power of the voltage signal from the adder, a cylinder that drives the vibration table, and a servo valve that controls the direction and flow rate of pressure oil supplied to the cylinder. The vibration tester is equipped with an input signal generator in its input section that stores voltage signals corresponding to the displacement, velocity, and acceleration of the vibration table, simultaneously reproduces the voltage signals corresponding to these, and supplies them forward to the adder. It is something that

The vibration testing machine of this invention will be explained below with reference to the illustrated embodiment.

FIG. 2 shows -flJ of the structure of the electro-hydraulic servo mechanism in the vibration tester of this invention, and in this figure, the same reference numerals as in FIG. 1 indicate the same parts.

Reference numeral 10 denotes an input signal generator that can simultaneously generate voltage signals corresponding to the output of the vibrator or the displacement, velocity, and acceleration of the vibration table 1. For example, a magnetic storage device that stores information corresponding to the displacement, velocity, and acceleration of the exciter output using a tape or core, and reproduces this information as a voltage signal, or an oscillation device as shown in Figure 3. A device is used.

This oscillator is constructed by first emitting an amplitude signal of a square wave signal corresponding to the acceleration of the exciter output from the oscillator U, and an amplitude signal of a triangular wave signal corresponding to the velocity of the exciter output from the oscillator V. The amplitude signal from U passes through the integrator ■ and is compared with the amplitude signal from the oscillator V in the comparators CO□ and CO2, and then the coil S is excited and demagnetized by the flip-flop circuit FF, and the contacts Sa and Sb are alternately connected. Close to.

As a result, the terminal A receives a square wave acceleration voltage signal ra based on the amplitude signal from the oscillator U, and the terminal B receives a triangular wave velocity voltage signal rv obtained by integrating the voltage signal ra with the integrator ■. , furthermore, the voltage signal rv is applied to the terminal C.
The device is configured to supply a parabolic displacement voltage signal ra obtained by integrating RA by an integrator .

Further, the feedback element according to the present invention includes a vibration table 1
The displacement detector 11 detects the displacement as a voltage signal and feeds it back to the adder 8 via the amplifier 12.In addition to this main feedback, the speed of the vibration table 1 is detected by the speed detector 13 for compensation. Speed feedback by detection and further vibration table 1
The vibration acceleration is detected by the acceleration detector 14 and the acceleration feedback is performed.

As mentioned above, this invention is applicable to the input signal generator 1 in the control system of the electro-hydraulic servomechanism in the vibration tester.
It simultaneously provides voltage signals corresponding to displacement, velocity, and acceleration of the vibration table 1 determined in advance as input signals from 0, and also includes displacement feedback as the main feedback, and velocity feedback and acceleration feedback as compensation.

As a result, we were able to increase the stability and responsiveness of this control system compared to conventional systems.

The reason why the control performance of the control system can be improved in this way will be explained using mathematical formulas.

Here, AP: Piston cross-sectional area (c/rI) b: Viscous drag coefficient (Ky - sec/cm) C
: Constant representing the stiffness of the drive member (Cm//Kf) ea: Acceleration feedback voltage (V) ev: Speed feedback voltage (V) ey: Displacement feedback voltage (V) i: Servo valve input current (mA) ) K: Gain of servo amplifier (m core) Ka: Feedback gain of acceleration (V s e
c'/m) Kv: Velocity feedback gain (Vse
c//Crrl) Ky: Displacement noft hack gain (
V/z) R1: Servo valve flow rate gain (Cm3/SeC
1mA) Rp: Decrease rate of servo valve output flow rate with increase in load pressure (cm5/s-Kg) m: Mass of moving part of shaking table (Ky・3e C2λ) pm
: Servo valve load pressure (Ky/m2) qm: Servo valve output flow rate (C is 5ee) r : Reference input (V) ra: Acceleration reference input (v) rv: Speed reference input (v) ry: Displacement reference input (V) Ra: Acceleration input gain Rv: Speed input gain Ry: Displacement input gain RX: Input conversion coefficient (V/Cn1) t: Time (see) V: Vibration table speed (a〆 5ee) X: Target value (cm) y: Displacement of the shaking table (crrl) The following equation holds regarding the characteristics of each component of the electrohydraulic servomechanism shown in FIG.

In other words, ■) Servo valve characteristics qm=Ri −i −Rp −pm (1)
■) Equation of continuity regarding oil flowing into the cylinder ■) Equation of motion of the vibration table ■) Characteristics of the servo amplifier 1 = K (ry + rv + ra - ey but ev - ea) (4i Ky Ky - r ■) For each detector Characteristic (7) e y"4y ' y (10) According to the above equations (1) to (10), when the electrohydraulic servo mechanism shown in FIG. 2 is shown in a block diagram, the fourth
The result will be as shown in the figure.

In this block diagram, the input signal generator 10 that gives displacement to the vibration table 1 has a reference voltage input r1, a reference voltage input r, a speed reference input □ obtained by differentiating the force r with respect to time, and a reference voltage input r. 2r, which is obtained by differentiating 2r with respect to time twice, and 7r, acceleration standard human power, are applied individually or at an appropriate ratio.

Here, the target value for the output y of the electrohydraulic servo mechanism is
Then, since the relationship r = Rx-x - (11) exists between the input r to this control system and the target value X, the input signal generator of the block diagram shown in Fig. can be rewritten into a flock diagram as shown in FIG.

The purpose of a closed-loop control system like the one shown in Figure 5 is to ensure that the controlled variable always matches the target value, and as a guideline for understanding this state, the stability and responsiveness of the control system are examined. It's good to compare.

That is, in the block diagram shown in FIG. 5, the output y
It is necessary to make this relationship match the target value X, and it is necessary for this relationship to hold true even in a steady state.

When the block diagram shown in FIG. 5 is equivalently transformed by focusing on the relationship of the above equation (12), it becomes as shown in FIG. 6.

In this figure.

As is clear from the figure, this equivalently transformed block diagram is cubic and has nonlinear characteristics.

In order to know the stability and responsiveness of this control system, if we select E=C2A and F2=B (i3), the transfer function G from input X to output y1 in Fig. 6 (S) is expressed as.

Thus, the characteristics of the control system shown in FIG. 3 are determined by the time constant T(
This is equivalent to the characteristic of the first-order lag element of s).

Therefore, the time constant T can be made as small as possible by increasing the gain of the servo amplifier, so the control system shown in Figure 3 can improve responsiveness without sacrificing stability. It is clear that

In the above case, it has been explained that the control performance of the control system can be improved under special conditions, but in the general case as well, for any constant λ (λ>0), AT=Eλ BT0C= E+Fλ (16)T+D
=E+λ If the coefficients C, D, E, and F of the transfer elements are selected for the block diagram shown in Fig. 6, the transfer function G(s) between input and output is given by: By selecting the value of the arbitrary number λ as small as possible, it is possible to improve the responsiveness without impairing the stability of the control system.

In this section 1, it has been described that the control performance of the electrohydraulic servo mechanism according to the present invention can be improved when the control system has a cubic configuration.

Furthermore, this control system can eliminate the effects of 1. especially when the influence of the compressibility of the oil supplied to the hydraulic cylinder can be omitted. Since the constant C representing the rigidity of the drive system becomes zero, the system becomes a quadratic control system as shown in FIG.

In Figure 7 shows.

The improvement in control performance of this quadratic control system will also be examined in the same manner as described above.

That is, if we select E=T1°T2+C(18) F2T1+D in Figure 7, the transfer function G(s) between input and output will be, and the output y of this control system will completely match the target value X. That is, the controlled amount always matches the target value, and the control performance of the control system is in an ideal state.

Either one of the coefficients E and C in the above (19) and F,
Either one of D can be selected arbitrarily.

For example, if C=D=O, E=T1T2°F2T1
Therefore, the above relationship can be maintained even without velocity feedback and acceleration feedback.

Although the case where the control system is represented by the second order or the third order has been described above, the same concept can be applied to the case where the control system is expressed by the fourth order or higher order.

As detailed above, in addition to the displacement feedback, which is the main feedback conventionally used as a feedback element in the control system, the vibration testing machine of this invention has only velocity feedback, only acceleration feedback, or velocity and acceleration feedback for compensation. In addition to providing a feedback signal for the vibration table, in addition to a predetermined displacement signal without waveform distortion as a reference input signal, a voltage signal corresponding to the speed and acceleration of the shaking table is simultaneously applied, thereby improving the stability of the control system. At the same time, the response can be increased at the same time, and the specimen on the shaking table can be vibrated to match the target value, making it possible to obtain sufficient data regarding the seismic resistance of the specimen. It has characteristics such as being able to

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of an electro-hydraulic servo mechanism in a conventional vibration testing machine, Figure 2 is a diagram showing an example of the configuration of an electro-hydraulic servo mechanism in a vibration test of this invention, and Figure 3 is a diagram showing an example of the configuration of an electro-hydraulic servo mechanism used in this invention. A diagram illustrating an example of an input signal generation device that can be used.
Figures 4 and 5 are block diagrams for explaining the control system of the vibration testing machine of this invention, and Figures 6 and 7 are equivalent conversions of the block diagrams shown in Figure 5. It is a block diagram. 1... Vibration table, 2... Cylinder, 3.
... Servo valve, 4 ... Hydraulic power source, 5 ...
...Displacement signal generator, 6...Displacement detector,
7...Amplifier, 8...Adder, 9...
... Servo amplifier, 10 ... Input signal generator, 11 ... Displacement detector, 12 ...
Amplifier, 13... Speed detector, 14...
Parameter detector, U...oscillator, ■...
Oscillator, I, I[...Integrator, COl. CO3... Comparator, S... Line wheel, Sa
, Sb... Contact.

Claims (1)

[Scope of utility model registration request] A feedback circuit that feeds back one or more of the displacement, velocity, and acceleration of the shaking table to the input side, an adder that adds the input signal and the feedback element, and a voltage signal from the adder. In a vibration testing machine equipped with an electro-hydraulic servo mechanism consisting of a servo amplifier that amplifies power, a cylinder that drives a vibration table, and a servo valve that controls the direction and flow rate of pressure oil supplied to the cylinder, the input section of the vibration testing machine is A vibration test characterized by comprising an input signal generation device that stores voltage signals corresponding to the displacement, velocity, and acceleration of the vibration table, simultaneously reproduces the voltage signals corresponding to these, and supplies them forward to the adder. Machine.