JPS592041B2 - Drive signal correction method for shaking table device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting disturbances in acceleration waveforms of equipment having a friction mechanism, and in particular to a method for use in a vibration table device that can faithfully reproduce an input signal given to a hydraulic servo system in its output. The present invention relates to a drive signal correction method.

Generally, equipment using hydraulic servomechanisms is used to move a test object or apply vibrations, but when applying vibrations, it is necessary to measure the response.

The component by which the response is measured is usually displacement, but some instruments measure acceleration. For example, in a shaking table device using a hydraulic servo system, this acceleration is the most important element in measurement. According to the prior art, when driving the vibration table, there is an input signal source such as a function generator, and this input signal is directly applied to the vibration excitation device via a control device. In this case, if the input signal is driven by a simple signal such as a sine wave, the displacement waveform will be reproduced clearly enough, but
When measuring the acceleration waveform, pulse-like disturbances are observed near the peaks and troughs of the sine wave, that is, near the peaks.
This occurs near the maximum acceleration, that is, when the speed of the shaking table reaches zero and its direction of motion changes. It has been found that there are three main factors responsible for the occurrence of such pulse-like waveform disturbances.

In other words, one is the vibration table support mechanism and drive device.
This is due to the frictional resistance of the actuator, seat belt, static pressure bearing, etc., and the other two are due to the flow characteristics of the servo valve. Moreover, all of these factors have nonlinear characteristics, such as vibration table amplitude, acceleration, oil flow rate,
, and many uncertain factors such as driving frequency. To deal with such waveform disturbances, conventional methods have been used such as using filters to cut out the disturbance components, but with this method, it is necessary to correct the essential cause of the waveform disturbance mentioned above The effect was merely to make the response waveform look similar to the input waveform.

Furthermore, it has been found that the main cause of waveform disturbance is mostly due to frictional resistance, but it is extremely difficult to mechanically improve the vibration table for the purpose of improving the acceleration waveform. Therefore, the object of the present invention is to provide a method for correcting waveform disturbances by processing acceleration waveforms electrically rather than mechanically. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below as illustrated in the accompanying drawings.

Figure 1 shows an example of a hydraulic servo system to which the method according to the present invention is applied, and shows a side view of a horizontal and vertical vibration type vibration table, and Figure 2 shows its applying device (vibrator ) shows an example.

The vibration table 2 is horizontally moved by a horizontal actuator 4.
It is driven vertically by a vertical actuator 6, and can be vibrated in both horizontal and vertical directions at the same time.

These actuators 4 and 6 are connected to the siebel head 8
One end is fixed to the vibration table 2, and the other end is fixed to the inner wall. The sive head 8 on the side of the shaking table is connected directly to the piston rod of the piston 12 in the actuator, and the sive head 8 on the side wall is fixed to the cylinders of the actuators 4 and 6. The operation of the piston 12 is controlled by a servo valve 10, and the servo valve 10 controls the injection and discharge of hydraulic pressure into the cylinder based on an input signal. A differential transformer 14 for detecting the movement of the vibration table 2 is installed at the tip of the piston rod.
is installed. FIG. 3 is a block diagram of a system using this shaking table apparatus suitable for carrying out the method of the present invention. According to FIG. 3, the vibration table vibration system includes the vibration table vibration machine system 20 shown in FIGS. 1 and 2, a computer and its attached frequency analyzer, a disk or magnetic tape device, and a card reader. , a paper tape reader/puncher, a digital processing device 22 including a CRT display, etc., and an analog/digital converter;
Digital control system including input/output interface 24 including digital/analog converter, buffer memory, etc.
Data processing system 26, function generator 28, data recorder 30, vertical controller 32, horizontal controller 34
and an analog control system 38 including an analog control device 36, a hydraulic system 40 including a hydraulic pump, a cooling tower, etc., and a measurement system 42 including an accelerometer, a dynamic strain meter, a displacement meter, a filter, etc. The waveform to be excited is, for example, an analog signal obtained by converting a digital signal recorded on a magnetic disk with a digital/analog converter, or an output signal from the function generator 28 or data recorder 38, and is input to the analog control device 36. be done.

The analog controller sends input signals to the servo valves via horizontal and vertical controls 34 and 32 to control the hydraulic system 40.
sends control signals to hydraulic pumps, etc. The vibration excited by the input signal is detected by the sensor 44, adjusted by the measurement system 42, and then sent to the digital control/data processing system 2.
6 is input. Next, a waveform correction method according to the present invention will be explained.

This correction method is based on the following two assumptions.

(1) The shaking table system is assumed to have a linear transfer function as a whole. (2) The average of the input wave is zero or a constant value close to zero, and it is a weakly stationary stochastic process with ergodicity.

Based on these two assumptions, correction is performed according to the steps shown in FIGS. 4 and 5.

(a) Find the inverse transfer function of the shaking table including the test object. To find this inverse transfer function, as shown in 1 to 8 in Figure 5 as an example, first create an input displacement with an optimal power spectrum, apply this to the shaking table, and measure the response acceleration. , the transfer function of the shaking table is determined from the input displacement and response acceleration, and the inverse transfer function is determined from this transfer function.

(b) Drive the vibration table with the wave you want to input (target acceleration waveform) and measure its response acceleration waveform (S [phase] in Figure 5)
).

(c) Compare the target acceleration waveform and the response acceleration waveform to determine pass/fail (@ in FIG. 5).

(d) If the judgment is passed, this process is stopped; if the judgment is not passed, the error (error acceleration waveform) between the target acceleration waveform and the response acceleration waveform is determined.

(Figure 5 [phase]). (e) Determine the amount of correction for correcting the error using the inverse transfer function. That is, the amount of correction of the displacement waveform is determined by weight integration of the error spectrum determined from the error acceleration waveform and the inverse transfer function (Fig. 5@). (f) Correct the previous input displacement waveform by the correction amount. Steps (b) to (f) are repeated until the judgment passes. This repetition depends on the accuracy of the inverse transfer function determined by the computer; for example, Digital Equipment Co., Ltd., PDPll
If it is a minicomputer of /45, 2 or 3 times,
By repeating this process about 10 times at most, a waveform that approximates the target waveform can be obtained. FIG. 7 shows an example of the response output waveform using the method according to the present invention and using a sine wave as the input signal.

According to FIG. 7, compared to FIG. 6 which shows an example of the response output waveform without using the method of the present invention, a waveform that is extremely close to the input wave is reproduced, and from this, most of the causes of disturbance in the acceleration waveform are It can be seen that this is due to the effect of frictional resistance as mentioned above. In this way, sine waves have local nonlinearity that cannot be captured by the transfer function, but good results are obtained for irregular waves such as seismic waves that almost always match the input wave. As mentioned above, in the past, even if the cause of the disturbance in the acceleration waveform seen in hydraulic servo systems was known, it was extremely difficult to improve it mechanically, both technically and cost-wise. According to the present invention, the cause of these waveform disturbances is considered to be one of the transfer functions of the hydraulic servo system, and the response waveform is compared with the input waveform while the input waveform is corrected by the inverse transfer function. It is now possible to easily correct the disturbance. As a result, the operation of the equipment can be made more accurate and reliable, making it possible to obtain more reliable data in, for example, vibration experiments. Furthermore, in other fields such as seismic engineering and control engineering, it becomes possible to accurately operate and control devices that have frictional resistance, such as actuators. Although the present invention has been described above in detail with reference to specific examples, the present invention is not limited to these specific examples, and it goes without saying that many changes and modifications can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

Figure 1 shows an example of equipment using a hydraulic servo system, Figure 2
3 is a diagram showing an example of a force applying device, FIG. 3 is a block diagram of a vibration table and drive suitable for carrying out the method according to the present invention, and FIG. 4 is a diagram schematically showing the method according to the present invention. Fig. 5 is a flowchart showing the contents of the method of the present invention, Fig. 6 is a diagram showing an example of a response waveform to a sine wave input of a hydraulic servo mechanism that does not use the method of the present invention, and Fig. 7 is a diagram showing a response waveform of a hydraulic servo mechanism using the method of the present invention. FIG. 6 is a diagram showing an example of a response waveform. 2... Vibration table, 4, 6... Actuator, 8... Siebel head, 10...
・Servo valve, 12...Piston, 14...
... Differential transformer, 20 ... Vibration table vibrator system,
22...Digital processing device, 24...
Input/output interface, 26...Digital control/data processing system, 28...Function generator, 30
...Data recorder, 32...Horizontal direction controller, 34...Horizontal direction controller, 36...
... Analog control device, 38 ... Analog control system, 40 ... Hydraulic system, 42 ... Measurement system, 44 ... Sensor.

Claims (1)

[Claims] 1. Consisting of a vibration table and horizontal and vertical actuators that vibrate the vibration table in the horizontal and vertical directions,
These actuators are driven by servo mechanisms,
In a drive signal correction method for a shaking table device that artificially reproduces an earthquake, the servo mechanism is controlled by a signal to drive the shaking table, and standard input displacements in the horizontal and vertical directions are determined in advance. a step of inputting the input displacement to the device, determining a transfer function of the device from this input displacement and its response acceleration, and determining an inverse transfer function from this transfer function, and a target acceleration of a signal to drive the vibration table and its response acceleration. A vibration table comprising the steps of: determining an error between the two, determining a correction amount from a convolution of the spectrum of this error and the inverse transfer function, and correcting an input signal to the device by the correction amount. Device drive signal correction method. 2. In the step of correcting, if there is still an error between the response acceleration of the input signal corrected by the correction amount and the target acceleration, a new correction amount is calculated from the convolution of the spectrum of the error and the inverse transfer function. 2. The method according to claim 1, wherein the input signal determined and previously corrected is corrected again using the new correction amount.