JP2773355B2 - Control device for material testing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to a control device of a material testing machine for accurately measuring the load-displacement characteristics of a specimen. Electrohydraulic material testing machines for determining properties are known. In this electrohydraulic material testing machine, for example, a load frame is formed by bridging a crosshead on a pair of columns erected on a base, and a test piece is set on a jig in the load frame. The load and the displacement are measured by a load cell and a differential transformer while loading the sample.

The operation will be described with reference to FIG. 5 showing the overall configuration of this material testing machine.

When the test condition of the test piece SP is 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 condition, and the setting signal generator 23 loads, for example, while expanding and contracting the test piece SP. A setting signal of the pattern waveform to be generated is generated. This setting signal is converted by the adder 25 into a differential transformer.
The deviation between the setting signal and the displacement signal is obtained by adding the current displacement signal detected by the counter 12 to the current displacement signal. Further, this deviation signal is amplified by the servo amplifier 28 and sent to the servo valve 10g 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 displacement caused by the load are the load cell 11 and the differential transformer, respectively.
The electric signal is detected by the converter 12, converted into an electric signal, amplified by the amplifiers 29a and 30a, respectively, and transmitted to the A / D converter 31. Further, the load signal and the displacement signal converted into digital signals by the A / D converter 31 are transmitted to the recorder 32 via the control circuit 21 and are displayed in a graph.

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

The operation of this circuit will be described with reference to FIG. 6 showing the gain characteristics of the amplifiers 29a and 30a.

When the amplitude of the setting signal generated from the setting signal generator 23 is small, the amplitude of the detection signals from the detectors 11 and 12 is also small. When the detection signal having such a small amplitude is amplified by an amplifier having a constant gain as shown in FIG. 6 (a), the amplitude of the output also becomes small. If the above-described feedback control is performed based on the detection signal having such a small amplitude, the control accuracy deteriorates, and the measured data of the load-displacement characteristic of the specimen SP also deteriorates. In such a case, stop the material testing machine
By operating b and 30b, according to the amplitude of the detection signal, for example, (b)
By switching from the gain 41a to the gain 41b or 41c shown in (1), highly accurate control can be performed, and accurate load-displacement characteristics can be obtained.

C. Problems to be Solved by the Invention However, such a conventional control device for a material testing machine has a problem that the detection signal gain switching circuit cannot be switched during the test. As described above, during the test, the feedback control is performed such that the deviation between the setting signal and the detection signal is always 0. Therefore, when the detection signal gain switching circuit switches the amplification gain of the detection signal during the test, A large deviation signal is generated at the time of switching.

 This will be described with reference to FIG.

FIG. 7 is a time chart showing changes over time of the setting signal, the detection signal, and the deviation signal added by the adder 25. Until time t1, the actuator 10e is driven to follow the set signal, the specimen SP is loaded, and a load or displacement detection signal as shown in the figure is fed back. Assume that the signal is almost zero. When the detection signal gain switching circuit is switched at time t1, the amplitude of the detection signal greatly changes as shown in the figure. As a result, the deviation signal instantaneously increases by the variation of the detection signal, and is further amplified by the servo amplifier 28.
The signal is sent to the servo valve 10g as a drive signal for the actuator 10e. That is, since the actuator 10e is instantaneously driven by a large drive signal, a large load may be applied to the specimen SP to cause breakage.

The technical problem of the present invention is to increase or decrease a setting signal and a load or displacement detection signal during a test, perform drive control to accurately follow the setting signal, and obtain a highly accurate load-displacement characteristic. .

D. Means for Solving the Problem The present invention will be described with reference to FIG. 1 showing an embodiment. The present invention provides a detecting means for detecting a physical quantity accompanying deformation of a specimen SP loaded by a loading means 10. 11, 12 and the specimen SP
Setting signal generating means 23 for generating a setting signal for determining a pattern for loading the load, and load control means 25, 26 for controlling the load means 10 so that the detected signal follows the setting signal.
The present invention is applied to a control device of a material testing machine having:

Then, setting signal increasing / decreasing means 24 for increasing / decreasing the gain of the setting signal generated by the setting signal generating means 23, and detection signal increasing / decreasing means 29, 30 for increasing / decreasing the gain of the detection signal detected by the detecting means 11, 12. A signal holding unit 27 for temporarily holding the output signals of the load control units 25 and 26, and the holding unit 27 is operated when the gain of the detection signal is increased or decreased by the detection signal increasing and decreasing units 29 and 30, and the gain of the detection signal is increased or decreased. The above technical problem is achieved by providing the switching control means 21 for increasing or decreasing the gain of the setting signal accordingly.

E. Operation The setting signal generator 23 generates a setting signal for determining the load pattern of the specimen SP, and loads the specimen SP by the loading means 10. 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, 2 is controlled so that the load pattern is determined by the setting signal.
6 controls the load means 10.

When the switching control unit 21 instructs to increase the magnitude of the detection signal, first, the outputs of the load control units 25 and 26 are temporarily held by the signal holding unit 27. Further, the gain of the setting signal generated by the setting signal generating means 23 and the gain of the detection signal detected by the detecting means 11 or 12 are increased and decreased in conjunction with each other. When the gain increase / decrease processing of the setting signal and the detection signal is completed, the output hold of the load control means 25, 26 is released. The load control means 25, 26 drives and controls the load means 10 based on the setting signal and the detection signal thus increased / decreased.

In the above sections D and E for describing the configuration of the present invention, the drawings of the embodiments are used for easy understanding of the present invention, 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, reference numeral 10 denotes a tester main body for applying a compressive load or a tensile load to the test piece SP, and the tester main body 10 includes a load frame LF. The load frame LF includes a pair of columns 10k, 10m erected on a base 10d, and a yoke 10a is horizontally mounted on upper ends of the columns, and a crosshead 10b is attached to the columns 10k, 10m so as to be vertically movable. The elevation mechanism of the crosshead 10b is not shown.

A hydraulic actuator 10e for load is installed on the base 10d, and a test piece is mounted between a lower jig 10f attached to a movable portion of the hydraulic actuator 10e and an upper jig 10c attached to a crosshead 10b via a load cell 11. SP is installed. 12
Is a differential transformer that detects the stroke of the hydraulic actuator 10e, that is, the displacement of the specimen SP. The hydraulic actuator 10e is configured such that a piston (not shown) expands and contracts by controlling the direction and amount of hydraulic oil by a servo valve 10g, and a lower jig 10f is mounted on the piston rod.

The control system for controlling the tester main body 10 includes a control circuit (microcomputer) 21 for controlling the entire system,
The control circuit 21 includes a setting signal generator 23 that generates a load pattern waveform specified by the control circuit 21 from the control circuit 21 and a magnification switching circuit 24 that switches a magnification for increasing or decreasing the setting signal in accordance with a command signal from the control circuit 21. Further, an adder 25 for calculating a deviation between a setting signal increased or decreased by an appropriate magnification and a load signal detected by the load cell 11 described later or a displacement signal detected by the differential transformer 12, and an amplifier 26 for amplifying the deviation signal
A signal hold circuit 27 for holding the amplified deviation signal in accordance with a command signal from the control circuit 21, and a servo amplifier 28 for amplifying the output of the signal hold circuit 27 and inputting the amplified output to the servo valve 10g. The hold circuit 27 holds the deviation signal until the switching is completed when the magnification of the setting signal is switched and the amplification gain of the detection signal is switched, and releases the hold after the switching is completed.

Further, a first gain switching circuit 29 for amplifying the load detection signal by switching the amplification gain by a command signal from the control circuit 21, a second gain switching circuit 30 for amplifying the displacement detection signal in the same manner, A / D converter 3 that converts load signals and displacement signals into digital signals and sends them to control circuit 21
With one. Reference numeral 32 denotes a recorder, which is a specimen SP based on the load signal and the displacement signal collected by the control circuit 21.
Is graphed and displayed.

The operation of the material testing machine configured as described above will be described with reference to a flowchart showing a program executed by the control circuit 21 in FIG. Here, it is assumed that the test is performed based on a pattern waveform of a displacement applied by expanding and contracting the specimen SP.

The test specimen SP is placed between the jigs 10c and 10f, and the test condition input unit 22 sets test conditions for the test specimen SP. The test conditions include the amplitude, average displacement value, and frequency of the sine wave that determines the load pattern, the number of cycles of the sine wave, and the sampling pitch of the data.
Before the test is started, the magnification of the setting signal and the range of the amplification gain of the detection signal are changed by the command signal from the control circuit 21 based on the amplitude of the setting signal.
24 and the first and second gain switching circuits 29, 30. The signal hold function of the hold circuit 27 is released.

When the start switch of the test condition input section is operated to start the test, the setting signal of the set displacement pattern waveform is set by the command signal from the control circuit 21.
Occurs from 23. This setting signal is input to the magnification switching circuit 24, is increased or decreased by a magnification selected in advance, and is transmitted to the adder 25. In the adder 25, a deviation between the setting signal and the current displacement value detected by the differential transformer 12 is obtained,
The signal is amplified by the amplifier 26 and sent to the hold circuit 27. At this time, since the hold function has been released, the deviation signal is directly input to the servo amplifier 28, amplified and sent to the servo valve 10g. Since the servo valve 10g controls the hydraulic actuator 10e so that the difference between the instantaneous value of the deviation signal and the current displacement signal is always 0, the actuator 10e follows the displacement pattern waveform via the upper and lower jigs 10c and 10f. Load the specimen SP.

The load applied to the specimen SP during the test and the displacement caused by the load are detected by the load cell 11 and the differential transformer 12, respectively, and the first and second gain switching circuits 29,
Entered in 30. The load signal and the displacement signal are respectively amplified by a first and second gain switching circuits 29 and 30 with an amplification gain selected in advance, converted into digital signals by an A / D converter 31, and sent to the control circuit 21. Is done.

In the control circuit 21, the program shown in FIG. 2 is executed at predetermined time intervals after the start of the test. When this program is executed, first, in step S1, a detection signal is sampled. Next, the process proceeds to step S2, where the amplitude of the detection signal is compared with a predetermined value K1, and if it is equal to or smaller than K1, the process proceeds to step S3, and if it is larger than K1, the process proceeds to return.

Here, the value of K1 is determined as follows. As is well known, in the feedback control system, the closer the voltage value of each signal added in the adder 25 is to the rated value of the adder 25, the higher the control accuracy becomes. Assuming that the rated voltage of the adder 25 is 5 V for both positive and negative, the amplitude of the input control signal is 10 V
Is preferably close to Therefore, for example, K1 is set to 8V, and when it is lower than 8V, the gain of the detection signal and the setting signal is increased so that the amplitude becomes 8V or more.

In step S3, the control circuit 21 instructs the hold circuit 27 to hold the current deviation signal. Next, proceeding to step S4, the control circuit 21 instructs the second gain switching circuit 30 to switch the amplification gain. Next, proceeding to step S5, the control circuit 21 instructs 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 described with reference to FIG.

FIG. 3 shows how the magnification of the setting signal and the amplification gain of the detection signal are switched with respect to the setting condition of the setting signal, and the setting signal voltage and the detection signal voltage added by the adder 25 by the switching. Show how it changes. Here, as the setting condition of the setting signal, the amplitude 20
It is assumed that the displacement signal of the sine wave pattern having mm is selected, and 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.

Now, it is assumed that the test signal is started and the amplitude of the setting signal voltage input to the adder 25 is 2V, and the amplitude of the detection signal voltage is 2V. In this case, since 2V ≦ K1 is affirmed in step S2, the amplification gain of the second gain switching circuit 30 is increased by a command from the control circuit 21 in step S4 after step S3. Here, it is preferable that the amplitude of the detection signal after the gain is set to 10 V, The gain G1 in the calculation is obtained by the following formula, and the gain is switched to the gain closest to the gain G1. Therefore, in this case,
The gain is changed by a factor of 5 from 10/2 = 5, whereby the amplitude of the detection signal voltage is increased to 10V. Further, in step S5, the control circuit 21 commands 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 before and after the gain change of the detection signal is obtained, and the gain of the setting signal is changed according to this ratio. Accordingly, as shown in the figure, the magnification of the setting signal is changed to 5 times, and the setting signal voltage of 10 V is input to the adder 25.

Next, the process returns to the flowchart of FIG. 2 and proceeds to step S6. Then, it stands by for a predetermined time until the increased / decreased setting signal, detection signal and its deviation signal are stabilized. After a predetermined time has elapsed, the process proceeds to step S7, where the control circuit
21 instructs the hold circuit 27 to release the hold of the drive signal. After executing the above processing, the control circuit 21 returns to the main program.

The above process is shown in the time chart of FIG. FIG. 4 shows the change over time of the setting signal, the detection signal and its deviation signal added by the adder 25. The detection signal is an ideal control system with no mechanical or electrical delay for the setting signal. Shall be. 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 the detection signal added in the adder 25 increases from 2V to 8V as shown in the figure. However, since the setting signal and the detection signal have opposite polarities and have the same absolute value, the deviation signal does not change because the setting signal and the detection signal cancel each other.
Therefore, even if the hold of the drive signal is released, an excessive drive signal is not input to the actuator 10e, and it is possible to smoothly return to the feedback control state.

In this way, control can be performed by resetting the setting signal by the magnification switching circuit 24 and the detection signal to the optimum voltage level by the second gain switching circuit 30 during the test.

In the above embodiment, an example is described in which the displacement detection signal is fed back to the displacement setting signal for control, but the present invention can also be applied to feedback control of the load detection signal in response to the load setting signal.

In the above description, when the amplitude of the detection signal is equal to or smaller than the predetermined value, each gain is automatically switched and the gain after the change is calculated. However, when the gain of the detection signal is manually set, the setting signal is changed. The gain is automatically switched in conjunction with it, and then, when a switching command is issued manually, each range is switched after temporarily holding the servo valve input,
Further, the hold may be released after that.

In the configuration of the above embodiment, the tester main body 10 controls the load means, the load cell 11 and the differential transformer 12 control the detecting means, the setting signal generator 23 controls the setting signal generating means, and the adder 25 and the amplifier 26 control the load. Means, a magnification switching circuit 24 is a setting signal increasing / decreasing means, first and second gain switching circuits 29 and 20 are detection signal increasing / decreasing means, a hold circuit 27 is a signal holding means, and a control circuit 21 is a switching control means. Configure each.

G. Effects of the Invention As described above, 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. After the hold is released, the load and displacement setting and detection signals can be increased or decreased during the test. And a highly accurate load-displacement characteristic can be obtained.

[Brief description of the drawings]

1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing an example of a program of a microcomputer, and FIG. 3 is a diagram showing a relationship between a magnification of a setting signal and an amplification gain of a detection signal. FIG. 4 is a time chart showing changes in the signal and the deviation signal when the magnification of the setting signal and the amplification gain of the detection signal are switched during the test in the material testing machine of the embodiment, and FIG. FIG. 6 (a) shows the input / output characteristics of an amplifier having a constant amplification gain, and FIG. 6 (b) shows the input / output characteristics of the amplifier when the amplification gain is switched. 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 the test with the conventional material testing machine. 10: Test machine 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: Gain switching circuit 30: Gain switching circuit, 31: A / D converter 32: Recorder

Claims (1)

(57) [Claims] 1. A detecting means for detecting a physical quantity associated with deformation of a test object loaded by a load means, a setting signal generating means for generating a setting signal for determining a pattern for loading the test object, and a detected signal A load control means for controlling the load means so as to follow the setting signal, wherein the setting signal increasing and decreasing means for increasing and decreasing the gain of the setting signal generated by the setting signal generating means And detection signal increasing and decreasing means for increasing and decreasing the gain of the detection signal detected by the detection means, signal holding means for temporarily holding the output signal of the load control means,
Switching control means for operating the hold means when increasing or decreasing the gain of the detection signal by the detection signal increasing / decreasing means, and for increasing or decreasing the gain of the setting signal in accordance with an increase or decrease in the gain of the detection signal. Control device for material testing machine.