JPH01227038A - Compensating method of load change on vibration stage and compensating apparatus thereof - Google Patents

Abstract

PURPOSE:To automate the compensation of a change in vibration acceleration accompanying a change in a load, by detecting a hydraulic pressure in a hydraulic pressure chamber of a hydraulic cylinder and by adding a compensation signal calculated on the basis of a detected value to an output signal of an automatic computation circuit. CONSTITUTION:Hydraulic pressures P1 and P2 in a pair of hydraulic pressure chambers of a hydraulic cylinder 2 are detected by pressure detectors 21 and 22, the respective detection signals of the pressure detectors 21 and 22 are amplified by an amplifier 23, and a differential pressure is calculated by an adder 24. Next, a compensation signal circuit 25 adds the detected differential pressure of the hydraulic cylinder 2 to an input voltage of a servo amplifier 9 by means of an adder 26. By giving a compensation signal to a servo value control signal in this way to prevent an output speed from suffering an effect of an operating force, the output speed is fixed even when the weight of a substance mounted on a vibration stage is varied, and a change in a load can be compensated automatically even in a system wherein the load changes with a large degree.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an electrohydraulic servo-controlled vibration table that can automatically compensate for changes in the weight of a mounted object and provide a constant vibration acceleration. An improved load change compensation method,
and a load change compensation device.

[Conventional technology]

Regarding this type of vibration table, a vibration tester described in Japanese Patent Publication No. 53-43061 is known.

FIG. 3 is a system diagram of the electro-hydraulic servo control mechanism in the above-mentioned known example.

A vibration table 1 on which a test object is mounted is vibrated by a hydraulic cylinder 2.

The hydraulic cylinder 2 is connected to a hydraulic power source 4 via a servo valve 3.

On the other hand, the input signal supply section 14 outputs a voltage signal E d corresponding to displacement, a voltage signal EV corresponding to velocity, and a voltage signal Ea corresponding to acceleration.

The amount of displacement of the vibration table 1 is detected by a displacement detector 10, the speed by a speed detector 12, and the acceleration by an acceleration detector 13.
are respectively detected and fed back via the amplifier 11.

The feedback signal is added to the voltage signal Edt ``''Vw Ea by the adder 8 and controls the servo valve 3 via the servo amplifier 9 .

FIG. 4 is a block diagram of the above-mentioned known example, and the meanings of the symbols are as follows.

Cross-sectional area of the piston of the Ap Niji cylinder 2 db = viscous drag coefficient kg s / amC: constant representing the law of the drive system cd / kgK = gain of the servo amplifier 9 m A / VKa: feedback gain of acceleration V S ' / anKv: Speed feedback gain V s / cmKy: Displacement feedback gain V / aaKi: Flow rate gain of servo valve 3
Al? / S m AKp: Decrease rate of output flow rate due to internal leakage of servo valve 3 ci / s kg m: Mass of moving part of shaking table 1 kgs2/cmRa
: Acceleration input gain (dimensionless) Rv: Velocity input gain 1/sRy: Displacement input gain 1/s2 In the block diagram shown in FIG. 2 above. Here, if we choose E=C=A, F=D=B...(3),
The above equation (1) is as follows.

That is, if each input Ra, Rv, Ry and each feedback Ka, Kv, Ky are set under the conditions of equation (3), the servo control system is approximated to a first-order system, and the characteristics are improved.

[Problem to be solved by the invention]

In the prior art described above (see FIG. 3), if it is assumed that there is no internal leakage in the servo valve 3 and that the transmission system connecting the hydraulic cylinder 2 and the vibration table 1 is a completely rigid body,
The vibration acceleration should not be affected by changes in the weight of the test object mounted on the vibration table 1.

However, as a practical matter, if the mounted weight increases, the oil pressure must be increased in order to provide the same acceleration, and as a result, leakage within the servo valve increases (effective output decreases). Furthermore, since the amount of elastic deformation of the transmission member also increases, in the above-mentioned known technology, the vibration acceleration also changes as the mounted weight (load) changes.

This can be explained based on a mathematical formula as follows.

The values of A and B above change depending on the moving part mass m (load m) as shown in equation (2), so when m changes, readjust Kv, Ka, Rv, and Ra each time. Otherwise, constant vibration acceleration cannot be obtained.

For example, in a system such as a shaking table for earthquake simulation in which most of the mass is fixed to the movable part of a shaking table and the load m does not change much, the conventional technique is sufficiently effective. However, if the load m changes significantly due to a vibrating object such as a vehicle vibration table, readjustment must be made each time to satisfy the condition of equation (3).

From a practical point of view, there is a problem in that each adjustment is very complicated and significantly impedes the operability of the shaking table system.

In view of the above, an object of the present invention is to provide a method and a compensating device for automatically compensating to obtain a constant vibration acceleration even if the weight of the load on the vibration table changes.

[Means to solve the problem]

The compensation means according to the present invention created to achieve the above object will be explained with reference to FIG. 4 (known example).

Input voltage E (S) + operating force F (S) + output speed V (S
) is obtained from the above equation (5), and the output speed v(S) is obtained from the above equation (5).

As is clear from equation (6), the output speed V (S), which is the final control target of the shaking table, is the input voltage E (S
) and the actuation force F (S).

That is, if there is a change in the operating force F (S), the output speed V (
6. Fluctuations in the operating force F (S) that cause changes in S) are caused by load fluctuations, and since both are the same, this means that the output speed v(s), which is the target of control, fluctuates due to changes in the load. Therefore, in order to eliminate the influence of load changes, (
In equation 6), a compensation signal G (S) that cancels the term of the actuation force F (S) may be added.

Compensation signal a < S) is expressed as F in equation (6) in equation (5).
It can be found as a value that cancels out the term (S), and is as follows.

Once the compensation signal G (S) shown in equation (7) is obtained, adding it to equation (6) will result in the output speed V (S) being equal to the input voltage E C5) of the servo amplifier. Proportional (Note: AP + K t k i is a constant).

[Effect]

If the above compensation signal G (S) is given so that V (S) is not affected by the actuation force F (S), V (S) will remain constant even if the mounted mass of the shaking table changes. . Therefore, a constant vibration acceleration is obtained.

〔Example〕

1 and 2 show one embodiment of the invention.

This embodiment is an improvement by applying the present invention to the above-mentioned known technique.

FIG. 1 is a control system diagram corresponding to FIG. 3 in the known example.

The compensation loop Cr shown in FIG. 1 is a loop that returns the hydraulic pressure p<s) of the hydraulic cylinder detected by the pressure detectors 21 and 22 described later in FIG. 2 to the input voltage E<s> of the servo amplifier as feedback. It constitutes. The transfer function of this compensation loop Cr is as follows.

The transfer function of equation (9) above is expressed by converting the operating force F (S) into the hydraulic pressure P
(s) and the gain K of the servo amplifier.

In a loop that takes into account the flow rate gain kP of the servo valve, (
7) It can be obtained so that it is equivalent to the signal in Eq.

Using the transfer function G (S) of equation (9), the above P
(S) to the input of the servo amplifier, the output speed V
C5) is the value of equation (8) above, and the load weight (mass m
) will no longer be affected by

FIG. 2 is a block diagram of an apparatus of the present invention configured to carry out the method of the present invention described above.

Pressure detectors 21 and 22 are provided to detect oil pressure P1°R2 in a pair of pressure chambers of the hydraulic cylinder 2.

The detection signals of the pressure detectors 21 and 22 are amplified by an amplifier 23, and a differential pressure is calculated by an adder 24. Here, the differential pressure of the hydraulic cylinder 2 becomes the hydraulic pressure P (S) that generates the operating force of the hydraulic cylinder 2.

Further, the compensation signal circuit 25 receives the above-mentioned differential pressure P (S) and operates as follows.

That is, the transfer function of the compensation signal circuit 25 is as shown in equation (10) below.

However, α1... R4 partial pressure ratio (0 to 1) α2・
...Partial pressure ratio of R5 (0 to 1) In order to realize the transfer function of equation (9) using the transfer function of equation (10), the following settings are made.

In addition, 5CR2 is set to the minimum value within a range that does not pose a problem with respect to noise, and the detected P(S) is set to a value that can be ignored as 5CR(αlR1+R2)>5CR2. When added to the input voltage of the servo amplifier 9 by the adder 26, it becomes equivalent to the compensation signal of equation (7). According to the device of this embodiment, it is possible to compensate for load fluctuations in the manner described above.

〔Effect of the invention〕

According to the compensation method of the present invention, even in a system where the load changes significantly due to a vibrated object such as a vehicle vibration table, the control characteristics can be prevented from being affected by the load change.

The circuit of the present invention was applied to a known vibration tester (Japanese Patent Publication No. 53-4306).
If it is added as a minor compensation for 1), it is possible to eliminate the need for adjustment every time the load changes so as to satisfy the condition of equation (3). By using the circuit of the present invention not only for the vibration testing machine of the above-mentioned known example, but also for general control of a vibration table consisting of an electro-hydraulic servo mechanism, it is possible to eliminate the influence of load changes, thereby improving control characteristics. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the compensation method according to the present invention, and FIG.
The figure is a control system diagram showing a compensation device according to the present invention. FIGS. 3 and 4 are explanatory diagrams of known techniques. DESCRIPTION OF SYMBOLS 1... Vibration table, 2... Hydraulic cylinder, 3... Servo valve, 4... Hydraulic source, 8... Adder, 9... Servo amplifier, 10... Displacement detector, 11...Amplifier, 1
2... Speed detector, 13... Acceleration detector, 14.
...Input signal supply section, 21, 22...Pressure detector,
23...Amplifier, 24...Adder, 25...Compensation signal circuit, 26...Adder. Representative Patent Attorney Miyu Akimoto! @

Claims (1)

[Scope of Claims] 1. A vibration table on which a test object is mounted, a hydraulic cylinder that vibrates the vibration table, a servo valve that controls pressure oil applied to the hydraulic cylinder, and the servo valve described above. When using a vibration table equipment equipped with an automatic calculation circuit that provides a control signal to the test object, in the method of providing a constant vibration acceleration by compensating for changes in the weight of the test object, (a) the hydraulic chamber of the hydraulic cylinder is (b) calculates a compensation signal based on the detected value; and (c) adds the compensation signal to the output signal of the automatic calculation circuit. load change compensation method. 2. The constant representing the rigidity of the drive system connecting the hydraulic cylinder and the vibration table is c (cm^3/kg), and the reduction rate of the output flow rate due to internal leakage of the servo valve is k_P (cm^3/sk).
g) The method for compensating for load changes in a shaking table according to claim 1, wherein: the compensation signal is proportional to c and k_P. 3. A vibration table on which the test object is mounted, a hydraulic cylinder that vibrates the vibration table, a servo valve that controls the pressure oil applied to the hydraulic cylinder, and an automatic system that provides control signals to the servo valve. When using a vibration table equipment equipped with an arithmetic circuit, in the device that compensates for changes in the weight of the object to be tested and gives a constant vibration acceleration, (a) detecting the hydraulic pressure in the hydraulic chamber of the hydraulic cylinder; (b) a compensation signal circuit that receives the output signal of the pressure detector and calculates a compensation signal; (c) adds the compensation signal to the servo valve control signal; A load change compensator for a vibration table, comprising: an adder for compensating for load changes in a vibration table.