JPH03248033A - Control apparatus of material testing machine - Google Patents

Abstract

PURPOSE:To obtain a highly accurate load-displacement characteristic when the gains of the detected signals of a load and displacement are changed by temporarily holding the input of a load means, increasing and decreasing the gains of the detected signals and preset signals, and releasing the holding. CONSTITUTION:A preset signal which is generated in a preset-signal generator 23 based on a command signal from a control circuit 21 is sent into an adder 15 through a magnification switching circuit 24. In the adder 25, the deviation between the preset signal and the displacement value that is detected with a differential transformer 12 is obtained. The value is sent into a holding circuit 27 through an amplifier 26. At this time, a holding function is released. The deviation signal is sent into a servo valve 10g through a servo-amplifier 28. The valve 10g controls a hydraulic actuator 10e so that the difference between the instantaneous value of the deviation signal and the present displacement signal becomes always 0. A load is applied on a body under test SP through jigs 10c and 10f. The load which is applied on the body under test SP and the displacement are detected with a load cell 11 and the differential transformer 12. The results are sent into the circuits 21 through gain switching circuits 29 and 30 and an A/D converter 31, and the load-displacement characteristic is displayed 32.

Description

Detailed Description of the Invention A. Industrial Field of Application The present invention relates to a control device for a material testing machine that accurately measures the load-displacement characteristics of a specimen. Electro-hydraulic material testing machines for determining properties are known. This electro-hydraulic material testing machine consists of: 1. For example, a load frame is formed by horizontally suspending a crosshead between a pair of columns erected on a base, and the specimen is placed on a jig within the load frame using a lever. The load and displacement are measured using a load cell, differential transformer, etc. while applying a load to the specimen.

The operation will be explained with reference to FIG. 5, which shows the overall configuration of this material testing machine.

When test conditions for the specimen SP are set in the test condition input section 22, a command is given from the control circuit 21 to the setting signal generator 23 according to the test conditions, and the setting signal generator 23, for example, applies a load while expanding and contracting the specimen SP. Generates a setting signal for the pattern waveform to be used.

This setting signal is added by the adder 25 to the current displacement signal detected by the differential transformer 12, and the deviation between the setting signal and the displacement signal is determined. Furthermore, this deviation signal is amplified by the servo amplifier 28 and sent to the servo valve Log as a drive signal. The actuator 10e is driven according to this drive signal, and the specimen SP is loaded.

The load applied to the specimen sp during this test and the resulting displacement are detected by the load cell 11 and the differential transformer 12, respectively, and converted into electrical signals, which are amplified by the amplifiers 29a and 30a, A, /D. The signal is sent to the converter 31.

Further, the load signal and displacement signal converted into digital signals by the A/D converter 31 are sent to the recorder 32 via the control circuit 21 and displayed in the form of a graph.

Here, switches 29b and 30b and resistors 29c to 29f and 3 are added to the input and output terminals of amplifiers 29a and 30a.
0c to 30f are elements for switching the gain of the amplifier according to the detection signal amplitude, and constitute a detection signal gain switching circuit.

The operation of this circuit will be explained with reference to FIG. 6, which shows the gain characteristics of the amplifiers 29a and 30a.

When the amplitude of the setting signal generated by the setting signal generator 23 is small, the amplitude of the detection signal from the detectors 11.12 is also small. If such a small amplitude detection signal is amplified by an amplifier with a constant gain as shown in FIG. 6(a), the amplitude of its output will also become small. If the above-described feedback control is performed based on such a small amplitude detection signal, the control accuracy will deteriorate, and furthermore, the accuracy of the measured load-displacement characteristic data of the specimen SP will also deteriorate.

In such a case, high precision can be achieved by stopping the material testing machine once and switching from gain 41a to gain 41b or 41c as shown in (b) by operating switches 29b and 30b, depending on the amplitude of the detection signal. It is possible to perform accurate control and obtain highly accurate load-displacement characteristics.

C1 Problem to be Solved by the Invention However, with such a conventional control device for a material testing machine, there is a problem in that the detection signal gain switching circuit cannot be switched during a test.

As mentioned above, during the test, feedback control is performed so that the deviation between the setting signal and the detection signal is always 0, so if the detection signal gain switching circuit switches the amplification gain of the detection signal during the test, When switching, a large deviation signal is generated.

This will be explained with reference to FIG.

FIG. 7 is a time chart showing changes over time in the setting signal, the detection signal, and their deviation signal added by the adder 25. Until time 0 t1, the actuator 10e is driven in accordance with the setting signal, and the specimen When the SP is loaded and the load or displacement detection signal as shown in the figure is fed back, the detection signal gain switching circuit is switched at time t1 when the setting signal and detection signal are balanced and the deviation signal is approximately O. , the amplitude of the detection signal fluctuates greatly as shown in the figure. As a result, the deviation signal instantaneously increases by the amount of variation in the detection signal, is further amplified by the servo amplifier 28, and is sent to the servo valve Log as a drive signal for the actuator 10e. That is, actuator 1
Since 0e is instantaneously driven by a large drive signal, there is a risk that a large load will be applied to the specimen SP and it will break.

The technical problem of the present invention is to increase/decrease the setting signal and the load/displacement detection signal during the test, perform drive control that accurately follows the setting signal, and obtain highly accurate load-displacement characteristics. .

01 Means for Solving the Problems The present invention will be explained in conjunction with FIG. 1 showing an embodiment. .12, a setting signal generating means 23 for generating a setting signal defining a pattern for loading the specimen SP, and a load control means 25 for controlling the loading means 10 so that the detected signal follows the setting signal. It is applied to a control device of a material testing machine equipped with 26.

and a setting signal increasing/decreasing means 24 for increasing/decreasing the gain of the setting signal generated by the setting signal generating means 23; and a detection signal increasing/decreasing means 29.30 for increasing/decreasing the gain of the detection signal detected by the detecting means 11.12; and signal holding means 27 for temporarily holding the output signals of the load control means 25 and 26.

When the detection signal increase/decrease means 29 and 30 increase or decrease the gain of the detection signal, the hold means 27 is operated;
The above technical problem is achieved by providing a switching control means 21 that increases or decreases the gain of the setting signal in accordance with the increase or decrease of the gain of the detection signal.

A setting signal that determines the load pattern of the E1 effect specimen SP is generated from the setting signal generator 23, and the loading means 10
Load P. Then, based on the physical quantity associated with the deformation of the specimen SP detected by the detection means 11 or 12, the load control means 25 and 26 control the load means 10 so as to achieve the load pattern determined by the setting signal.

When the switching control means 21 issues a command to increase the magnitude of the detection signal, first, the outputs of the load control means 25 and 26 are temporarily held by the signal hold means 27. Furthermore, the gain of the setting signal generated by the setting signal generating means 23 and the detection signal detected by the detecting means 11 or 12 are increased or decreased in conjunction with each other. When the gain increase/decrease process for the setting signal and the detection signal is completed, the hold on the outputs of the load control means 25 and 26 is released. The load control means 25 and 26 control the load means 10 based on the setting signal and the detection signal which have been increased or decreased in this way.

It should be noted that in the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used in order to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Embodiment FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. In the figure, 10 is a test machine main body that applies a compressive load or a tensile load to the specimen SP.

This testing machine main body 10 is equipped with a load frame LF.

The load frame LF consists of a pair of supports 1 erected on a base 10d.
．． 0, the yoke 10a is horizontally suspended at the upper end of the 10m, and the crosshead 1 is movable up and down to the support LOk, 10m.
It is configured by attaching 0b.

Note that the elevating mechanism for the crosshead 10b is omitted from illustration.

A hydraulic actuator 10e for loading is installed on the base 10d, and a lower jig 10f attached to the movable part of the hydraulic actuator 10e and a load cell 1 are attached to the crosshead 10b.
The specimen S is placed between the upper jig 10c attached via the
P is installed. 12 is a differential transformer that detects the stroke of the hydraulic actuator 10e, that is, the displacement of the specimen SP. Note that the hydraulic actuator 10e is.

A piston (not shown) expands and contracts by controlling the direction and amount of pressurized oil by a servo valve Log, and a lower jig 10f is attached to this piston rod.

The control system that controls the test machine main body 10 includes a control circuit (microcomputer) 21 that controls the whole, and a setting signal generator 23 that generates a load pattern waveform instructed from the test condition input section 22 via the control circuit 21. and a magnification switching circuit 24 that changes the magnification for increasing or decreasing the setting signal according to a command signal from the control circuit 21. In addition, the setting signal increased or decreased by an appropriate magnification and the load cell 1 described later
an adder 25 for calculating the deviation from the load signal detected by the differential transformer 1 and the displacement signal detected by the differential transformer 12; an amplifier 26 for amplifying the deviation signal; It has a signal hold circuit 27 that holds the signal, and a servo amplifier 28 that amplifies the output of the signal hold circuit 27 and inputs it to the servo valve Log.

The hold circuit 27 holds the deviation signal until the switching is completed when changing the magnification of the setting signal and when switching the amplification gain of the detection signal, and releases the hold after the switching is completed.

Furthermore, a first gain switching circuit 29 switches the amplification gain according to a command signal from the control circuit 21 to amplify the load detection signal, and a second gain switching circuit 29 similarly amplifies the displacement detection signal.
gain switching circuit 30, and an A/C converting these load signals and displacement signals into digital signals and sending them to the control circuit 21.
It has a D converter 31. Note that 32 is a recorder that graphs and displays the load-displacement characteristics of the specimen SP based on the load signal and displacement signal collected by the control circuit 21.

The operation of the material testing machine configured as described above will be explained with reference to a flowchart showing a program executed by the control circuit 21 in FIG. Here, the test is performed using a displacement pattern waveform in which the specimen SP is expanded and contracted and loaded.

The specimen sp is installed between the jigs 10c and 1Of, and the test conditions for the specimen sp are set using the test condition input section 22. Test conditions include the amplitude, average displacement value, and frequency of the sine wave that determines the load pattern, as well as the period of the sine wave and the sampling pitch at which data should be collected. Before starting the test, a command signal from the control circuit 21 changes the magnification of the setting signal and the range of the amplification gain of the detection signal based on the amplitude of the setting signal to the magnification switching circuit 24, the first and second Gain switching circuit 2
9.30. In addition, hold circuit 2
7, its signal hold function is released.

When the start switch of the test condition input section is operated to start the test, a setting signal of the set displacement pattern waveform is generated from the setting signal generator 23 in response to a command signal from the control circuit 21. This setting signal is input to the magnification switching circuit 24, is increased or decreased by a preselected magnification, and is sent to the adder 25.
sent to.

In the adder 25, this setting signal and the differential transformer 12
The deviation from the current displacement value detected by is determined, amplified by amplifier 26, and sent to hold circuit 27. At this time, since the hold function is released, the deviation signal is inputted as is to the servo amplifier 28, amplified, and sent to the servo valve 10g. The servo valve Log controls the hydraulic actuator 10e so that the difference between the instantaneous value of this deviation signal and the current displacement signal is always 0.

The actuator 10e loads the specimen SP via the upper and lower jigs 10c and 10f according to the displacement pattern waveform.

The load applied to the specimen sp during the test and the displacement caused by it are calculated by the load cell 11° and the differential transformer 1, respectively.
2 and input to the first and second gain switching circuits 29 and 30.

The load signal and displacement signal are each amplified by a preselected amplification gain in the first and second gain switching circuits 29 and 30, converted into digital signals by the A/D converter 31, and sent to the control circuit 21. be done.

The control circuit 21 executes the program shown in FIG. 2 at predetermined time intervals after the test is started. When this program is executed, first in step S1, a detection signal is sampled.

Next, the process advances to step S2, where the amplitude of the detection signal reaches a predetermined value.
If it is less than K1, the process advances to step S3, and K
If it is greater than 1, proceed to return.

Here, the value of K1 is determined as follows.

As is well known, in a feedback control system, the voltage values of each signal added in the adder 25 are:

The closer the adder 25 is to the rated value, the higher the control accuracy becomes. Assuming that the rated voltage of the adder 25 is 5V for both positive and negative, it is preferable that the amplitude of the input control signal is close to IOV. Therefore, for example, 1 is set to 8■, and if it is lower than that, the detection signal and setting signal Increase the gain to increase the amplitude to 8V
Make it so that it becomes more than that.

In step S3, the control circuit 21 instructs the hold circuit 27 to hold the current deviation signal. Next, the process proceeds to step S4, where the control circuit 21 instructs the second gain switching circuit 30 to switch the amplification gain. Next, the process proceeds to step S5, where the control circuit 21
commands the magnification switching circuit 24 to switch the magnification of the setting signal.

The switching of the amplification gain of the detection signal and the magnification of the setting signal will be explained with reference to FIG.

FIG. 3 shows how the magnification of the setting signal and the amplification gain of the detection signal are switched according to the setting conditions of the setting signal, and how the setting signal voltage and detection signal voltage added by the adder 25 are changed by switching. Here, we will show how the setting signal changes with vibration @ as the setting condition of the setting signal.
It is assumed that a displacement signal having a sine wave pattern of 20 wa is selected, and that the magnification of the setting signal and the amplification gain of the detection signal are each set to 1 before the start of the test.

Assume now that the amplitude of the setting signal voltage input to the adder 25 after starting the test is 2V, and that the amplitude of the detection signal voltage is also 2V. In this case, in step S2, 1 for 2v≦
Since this is affirmed, the amplification gain of the second gain switching circuit 30 is increased in accordance with a command from the control circuit 21 in step S4 after passing through step S3. Here, it is preferable to set the amplitude of the detection signal after setting the gain to IOV, so
It is assumed that a calculated gain G1 is obtained from the amplitude before the gain is set, and the gain is switched to the gain closest to this gain G1. Therefore, in this case, the gain is changed to 5 times from 10/2=5, thereby increasing the amplitude of the detection signal voltage to 10V. Further, in step S5, the control circuit 21 instructs the magnification switching circuit 24 to change the set signal magnification to be equal to the increased amplitude voltage of the detection signal. That is,
The ratio of the detection signal before and after the gain is changed is determined, and the gain of the setting signal is changed based on this ratio. Therefore, as shown in the figure, the magnification of the setting signal is changed to 5 times, and the IOV is sent to the adder 25.
The setting signal voltage is input.

Next, the process returns to the flowchart of FIG. 2, proceeds to step S6, and waits for a predetermined period of time until the increased/decreased setting signal, detection signal, and deviation signal thereof are stabilized. After a predetermined period of time has elapsed, the process advances to step S7, where the control circuit 21 executes one or more processes to instruct the hold circuit 27 to release the hold of the drive signal, and then returns to the main program.

The above process is shown in the time chart of FIG.

Figure 4 shows the changes over time of the setting signal, the detection signal, and their deviation signal added by the adder 25, and shows that the detection signal is an ideal control system with no mechanical or electrical delay with respect to the setting signal. When the amplification gain of the detection signal and the magnification of the setting signal are switched at time t2, the amplitude of the setting signal and detection signal added in the adder 25 increases from 2■ to 8■ as shown in the figure. do. However, since the polarity of the setting signal and the detection signal are opposite and their absolute values are equal, the deviation signal does not change because the setting signal and the detection signal cancel each other out. Therefore, the hold of the drive signal is released. Also, an excessive drive signal is not input to the actuator loe, and the feedback control state can be smoothly returned.

In this manner, control can be performed by resetting the setting signal by the magnification switching circuit 24 and the detection signal to the optimal voltage level by the second gain switching circuit 3o during the test.

In addition, in the above embodiment, an example was shown in which control is performed by feeding back a displacement detection signal to a displacement setting signal.
The present invention can also be applied to feedback control of a load detection signal with respect to a load setting signal.

In addition, in the above, when the amplitude of the detection signal is below a predetermined value, each gain is automatically switched and the gain after the change is calculated, but if the gain of the detection signal is manually set, the setting signal The gain may be automatically switched in conjunction with the gain, and then when a switching command is issued manually, the servo valve input may be temporarily held, then each range may be switched, and then the hold may be released.

In the configuration of the above embodiment, the tester main body 10 serves as the load means, the load cell 11 and the differential transformer 12 serve as the detection means, the setting signal generator 23 serves as the setting signal generation means, and the adder 2
5 and the amplifier 26 control the load control means, the magnification switching circuit 24 controls the setting signal increase/decrease means, the first and second gain switch circuits 29 and 20 control the detection signal increase/decrease means, and the hold circuit 27 controls the signal hold means. The circuits 21 respectively constitute switching control means.

As described in detail of the G5 invention, according to the present invention, when changing the gain of the load or displacement detection signal, the input of the load means is temporarily held, and then the gain of the detection signal and the setting signal is increased or decreased. Since the hold is released after the test is completed, the load means does not operate undesirably even if the load and displacement setting signals and detection signals are increased or decreased during the test, making it possible to perform control that accurately follows the setting signals. , highly accurate load-displacement characteristics can be obtained.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing an embodiment of the present invention, Fig. 2 is a flowchart showing an example of a microcomputer program, and Fig. 3 is a diagram showing the relationship between the magnification of the setting signal and the amplification gain of the detection signal. , Fig. 4 is a time chart showing the changes in the set signal magnification and the amplification gain of the detection signal when the setting signal magnification and the detection signal amplification gain are changed during the test in the material testing machine of the example, and Fig. 5 shows the changes in the signals and the deviation signal. Figure 6(a) shows the overall configuration of the material testing machine, Figure 6(,) shows the input/output characteristics of an amplifier with constant amplification gain, and Figure 6(b) shows the input/output characteristics of the amplifier when switching the amplification gain. The figure shown in FIG. 7 is a time chart showing changes in the setting signal, the detection signal, and the deviation signal when the amplification gain of the detection signal is switched during a test using a conventional material testing machine. 10: Test machine main body 11: Load cell 12: Differential transformer 21: Control circuit (microcomputer) 22: Test condition input section 23: Setting signal generator 24: Magnification switching circuit 25: Adder 26: Amplifier 27: Hold circuit 28 : Servo amplifier 29 2-gain switching circuit 30 2-gain switching circuit 31: A/D converter 32: Recorder

Claims (1)

[Claims] a detection means for detecting a physical quantity accompanying deformation of the specimen loaded by the loading means; a setting signal generating means for generating a setting signal defining a pattern for loading the specimen; A control device for a materials testing machine, comprising: a load control means for controlling the load means to follow the load means; a detection signal increase/decrease means for increasing/decreasing the gain of the detection signal detected by the load control means; a signal hold means for temporarily holding the output signal of the load control means; and a holding means when the gain of the detection signal is increased/decreased by the detection signal increase/decrease means. 1. A control device for a material testing machine, comprising: switching control means for operating the control device and increasing or decreasing the gain of the setting signal in accordance with the increase or decrease in the gain of the detection signal.