JPS6352693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a load control device for a material testing machine, and particularly to a load control device suitable for performing dynamic tests such as fatigue tests on materials.

(b) Prior art Due to the nature of the test, test machines that use a closed load control system are generally used to perform the above-mentioned dynamic tests. Testing machines are widely used. A conventional electro-hydraulic servo type testing machine, for example, as shown in FIG. It is composed of a servo amplifier 4, a vibrator 5 that is excited by hydraulic oil from the servo valve 3, a load cell 6 and a load amplifier 7 for measuring the load acting on the test object W, and the like. The output of the load amplifier 7, that is, the measured value signal B, is fed back to the target value signal A to obtain the control operation signal C. In such a servo control type testing machine, for example, when the load frequency is increased to shorten the test time of a fatigue test, the amplitude of the target value signal remains unchanged due to the influence of the frequency characteristics of the testing machine. First, the load amplitude that actually acts on the test object decreases. In addition, even if the mechanical characteristics of the test object W change as the test progresses, such as compliance, the actual load amplitude will change even if the target value signal is the same, and the load amplitude adjuster will change each time. There were cases where it was not possible to give a constant load amplitude without operating 2.

By the way, in order to solve this problem, conventional methods detect the amplitude value of the actual load amplitude, compare the detected value with the target amplitude value, and adjust the clock output from the clock oscillator based on the comparison result. A control device has been proposed that obtains a target value signal by increasing or decreasing the frequency and supplying it to the up or down terminal of an up-down counter and multiplying the count value of the up-down counter by the load waveform signal (Japanese Patent Application Laid-Open No. Akira
55-72845). According to this technology, the target value signal changes by a constant amount corresponding to one count of the up-down counter, and therefore the actual amplitude value also changes by a corresponding amount to approach the target amplitude value. , the period of change depends on the magnitude of the deviation. Therefore, in order to make the actual amplitude value follow the target amplitude value with high precision, the above-mentioned constant amount,
In other words, it is necessary to reduce the resolution of the device, but if this resolution is reduced, if the actual amplitude value deviates significantly from the target amplitude value due to sudden changes in the load frequency, etc. Even if the cycle of change is made faster, there will naturally be a limit, and the target amplitude value will be reached more slowly. On the other hand, in order to increase the arrival speed, it is necessary to increase the amount of change per count, which has the disadvantage of decreasing accuracy.

(c) Purpose The purpose of the present invention is to quickly and accurately adjust the actual load amplitude to the target amplitude value even if the load frequency changes or the mechanical characteristics of the test object change. It is an object of the present invention to provide a load control device for a material testing machine that can be made to follow the load.

(d) Configuration The configuration for achieving the above object will be explained with reference to the functional block diagram shown in FIG. , an actual amplitude value detector that detects the amplitude value of the measured value signal of the load actually acting on the test object, and a digital conversion value D of the detected amplitude value.
a deviation calculating means for reading the amplitude every moment and calculating the deviation X from a preset target amplitude value;
A division means for dividing the deviation X by a preset constant K, an addition means for adding the division result X/K to the target amplitude value E, and the addition result (E+
It is characterized by having a multiplier that multiplies X/K) by a reference amplitude wave, and is configured to supply the output of the multiplier as the target value signal A.

(E) Effect The target value signal A changes by an amount X/K determined by the magnitude of the deviation X and the constant K in a certain period, and the actual amplitude value approaches the target amplitude value accordingly. In other words, the actual amplitude value approaches the target amplitude value at a predetermined period by an amount that depends on the magnitude of the deviation, and the accuracy (resolution) and the speed at which the target amplitude value is reached are independent of each other. , the combination of high precision and high attainment speed can be easily achieved.

(f) Examples Examples of the present invention will be described below based on the drawings.

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention.

The load applied to the test object W by the vibrator 11 of the testing machine is measured by the load cell 12 and load amplifier 13, and the measured value signal B is fed back to the target value signal A and is also fed back to the actual vibration. It is supplied to a width value detector 14. Actual amplitude value detector 1
4 detects and outputs the actual amplitude value D for each period of the measurement value signal B, and the value is converted into a digital quantity by the AD converter 15 and taken into the computer 16. In addition to the CPU 17, the computer 16 has
It consists of a ROM 18 in which a program is written, a RAM 19 in which the above-mentioned actual amplitude value D etc. are temporarily stored, a keyboard 20 for setting the target amplitude value E etc. to be added to the test object W, and others.
A commanded amplitude value F, which will be described later, is calculated from the target amplitude value E and the actual amplitude value D and is output. On the other hand, oscillator 2
1 generates a reference amplitude wave G of the required waveform to be excited, and its output is sent to the multiplier 22 along with the command amplitude value F.
The multiplier 22 multiplies these signals and outputs them as the target value signal A. The measured value signal B is fed back and becomes the control moving object signal C, which is supplied to the servo amplifier 23. The servo amplifier 23 is configured to control the servo valve 24 according to the control operation signal C, adjust the amount of hydraulic oil supplied from the hydraulic source 25, and drive the vibrator 11.

Next, we will discuss the effect. Figure 4 shows the computer 16
This is a flowchart showing the process of calculating and outputting the command amplitude value F by using the following method.

The actual amplitude value D collected for each cycle of the load is
A deviation X is calculated by comparing it with a preset target amplitude value E. Next, the deviation X is 0
It is determined whether or not it is outside the range of the dead zone ±X ₀ provided nearby, and if it is within the range, the target amplitude value E
That value is output as the command amplitude value F. When the deviation X is outside the dead zone, the command amplitude value F is calculated by the following formula and output.

F=E+X/K K: Constant That is, the command amplitude value F is the value obtained by dividing the deviation X by the constant K and adding it to the target amplitude value E. The constant K is a set value so that the actual amplitude value D reasonably approaches the target amplitude value E, and in experiments, values of 2 to 4 have shown good results. Therefore, the commanded amplitude value F is sequentially corrected every time the actual amplitude value D is sampled, that is, every cycle of the load, depending on the magnitude of the deviation X of the actual amplitude value D from the target amplitude value E. As a result, the deviation X gradually approaches 0. As a result, as shown in FIG. 5, which shows the target value signal A and the measured value signal B according to the embodiment of the present invention when the excitation frequency is increased stepwise, the amplitude value of the measured value signal B becomes the target amplitude value E. The amplitude of the target value signal A is gradually corrected so that it approaches , and is output from the multiplier 22 . Incidentally, Fig. 6 similarly shows the target value signal and measured value signal from the conventional closed-loop system control device.If the target value signal has a constant amplitude value, it will affect the response characteristics of the test machine, etc. Therefore, the amplitude value of the measured value signal decreases in stages.

Note that the dead zone provided near 0 should be selected to a size that does not affect control accuracy and does not disturb control stability, and the constant K mentioned above also affects control stability. If it is set as close to 1 as possible without causing disturbance, the amplitude correction response will be faster.

In the embodiments described above, the load was controlled using the load, but it goes without saying that it may be controlled using other physical quantities related to the load, such as displacement or, depending on the test, torque.

(g) Effects As explained above, according to the present invention, the target value signal is corrected by an amount corresponding to the deviation of the actual amplitude value from the target amplitude value, for example, at regular intervals such as every cycle of the load. is added, and the actual amplitude value asymptotically approaches the target amplitude value accordingly. Here, the speed at which the actual amplitude value reaches the target amplitude value depends only on the magnitude of the deviation and the constant K, and as in the past, it has a mutually independent relationship with the resolution.
The actual amplitude value can be made to follow the target value with high accuracy and high speed. This means that, for example, parts of an aircraft are vibrated while constantly changing the temperature and load pattern (load frequency and amplitude).
It is particularly effective when conducting flight-by-flight tests, etc., and allows high-quality analysis results to be obtained at all times.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a load control device of a conventional material testing machine, Figure 2 is a functional block diagram showing the configuration of the present invention, and Figure 3 is a block diagram showing the configuration of an embodiment of the present invention. , FIG. 4 is a flowchart showing the process of outputting the command amplitude value, FIG. 5 is a waveform diagram showing the target value signal and measured value signal according to the embodiment of the present invention, and FIG. 6 is the target value signal according to the conventional example. FIG. 3 is a waveform diagram showing a measured value signal. 11... Exciter, 12... Load cell, 13... Load amplifier, 14... Actual amplitude value detector, 16... Computer, 21... Oscillator, 22... Multiplier, 23... Servo amplifier, 24... Servo valve, A... Target Value signal, B...Measured value signal, C...Control operation signal, D...Actual amplitude value, E...Target amplitude value, F...Command amplitude value, G...
Reference amplitude.

Claims (1)

[Claims] 1 By fielding back the measured value signal of the physical quantity related to the load actually acting on the test object to the target value signal for exciting the test object,
In a device configured to obtain a control operation signal for an exciter that excites a test object, an oscillator that generates a reference amplitude wave of a required waveform to be excited and an amplitude value of the measured value signal detected. an actual amplitude value detector, which reads the digital conversion value of the detected amplitude value moment by moment, and calculates a deviation from a preset target amplitude value; comprising a division means for dividing by a set constant, an addition means for adding the division result to the target amplitude value, and a multiplier for multiplying the addition result by the reference amplitude value, and the multiplier output is A load control device for a material testing machine, characterized in that it is configured to supply the target value signal as the target value signal.