JPH0434761B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a control device for a material testing machine, and in particular,
This invention relates to a control device for a material testing machine suitable for tests such as Kth tests that require a high average level of micro-width load.

(b) Prior Art Many high-performance material testing machines use an electro-hydraulic servo mechanism as their control mechanism. In such a material testing machine, when a load is applied repeatedly by load control, for example, the configuration of the control mechanism can be represented by a block diagram as shown in FIG. In this case, in order to perform the test as accurately as possible, the range of load amplifier 1 (usually 4 to 5
Steps). Next, the amplitude value and average value of the repetitive waveform are set as numerical values for the full scale of the range, and the hydraulic load mechanism 3 including the servo valve is controlled in feedback via the servo amplifier 2.

If it is necessary to change the amplitude target value and average value target value of the repetitive load over time, the fourth
According to the conventional control device shown in the figure, in a test in which both the amplitude value and the average value decrease or increase, control accuracy can be maintained by sequentially changing the range of the load amplifier 1 during the test. However, in a test where only the amplitude value decreases or increases over time and the average value remains at a high level and hardly changes, it is difficult to maintain control accuracy throughout the test. That is, when applying repeated loads as shown in Fig. 5a, for example, in the fourth range in the area and in the third range in the area.
By changing the range of the load amplifier 1 and changing each setting signal accordingly, high control accuracy can be maintained. However, when repeated loads are applied as shown in FIG. 5b, the range cannot be changed as the amplitude value decreases, and the fourth range must be used consistently. Therefore, there is a problem in that the degree of amplitude increase is low in the minute amplitude range, and highly accurate control cannot be performed. Furthermore, in the test shown in Figure 5a, with the conventional equipment, it is necessary to temporarily return the load to 0 and interrupt the test when switching ranges, and there is also the problem that continuous tests cannot be performed. Ta.

(c) Purpose The present invention has been made in view of the above, and is applicable to tests such as the Kth test, which require repeated loads such that only the amplitude changes over time while the average value remains at a high level. The object of the present invention is to provide a control device for a material testing machine that can maintain high control accuracy at all times and perform continuous testing without interrupting testing.

(d) Configuration In order to achieve the above object, the present invention compares a detected value signal and a target value signal of a physical quantity that changes in relation to the load on the test object in a comparison section, and calculates the In a material testing machine equipped with a control mechanism for controlling the load on a test object, in a control device for applying repeated loads, an average value that generates an average value signal corresponding to the average value component of the repeated load to be applied to the test object. A signal generating means, a waveform generating means for generating a repetitive waveform signal corresponding to the waveform component of the repetitive load, inputting a signal obtained by subtracting the average value signal from the detected value signal, and supplying the output to the comparing section. and amplification setting means for setting the amplification degree of the variable amplification means and the output waveform amplitude of the waveform generation means in accordance with the amplitude value of the repetitive load to be applied to the test object. The repetitive load signal to be applied is separated into the average value signal and the repetitive waveform signal, and outputted.
Further, the repetitive waveform signal is supplied to the comparison section as a target value signal, the difference between the repetitive waveform signal and the output of the variable amplification means is outputted as a deviation signal, and the amplification degree setting means It is characterized by being configured to set the degree of amplification in the amplification means to the maximum value at which the signal is not saturated within the control mechanism.

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

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The hydraulic loading mechanism 11 includes a servo valve, and can load the test object based on a signal from the servo amplifier 12. The load acting on the test object due to the load is detected by the load cell 13 and the load amplifier 14. The detection signal is fed back to a comparator 17 via an addition point 15 and a multiplier 16. An inverted signal of the average value of the repeated loads to be applied to the test object is added to the addition point 15, and an amplification degree setting signal, which will be described later, is input to the multiplier 16. The signal fed back to 17 is a signal obtained by multiplying the difference between the load detection signal and the weight average value signal by the amplification degree setting signal. A load waveform signal corresponding to the waveform of the repeated load to be applied to the test object is supplied to the comparator 17 as a target value signal for feedback control. The above-mentioned weight average value signal, amplification degree setting signal, and load waveform signal are calculated and outputted by a computer system 18 including a CPU, ROM, RAM, DA converter, etc. .

Next, how to set each of the above-mentioned signals by the computer system 18 will be explained based on a flowchart using the Kth test as an example. FIG. 2 is a flowchart showing a program for the Kth test in the computer system 18. Note that the range of the load amplifier 14 is fixed to a predetermined range, and therefore its full scale value remains unchanged throughout the test. Further, it is assumed that the resolution of the weighted average value signal and the setting of the amplification degree are each about 12 bits (±1/2000).

First, the initial crack length of the set test piece is measured, and based on the measurement results, the amplitude target value and average target value of the repeated load to be applied to the test piece are calculated by known calculations. Next, comparison section 1
The amplitude of the load waveform signal to be supplied to the load waveform signal 7 is set to an arbitrary value of a considerable magnitude so as to enable a highly accurate control device. At the same time, the degree of amplitude is calculated from the set value, the full scale value of the load amplifier 14, and the above-mentioned amplitude target value using the following formula.

Amplification degree = Load waveform signal amplitude setting value × Full scale value of load amplifier 14 / Load amplitude target value Then, the amplitude of the load waveform signal is output as the above setting value, and the load average value signal is the calculated load. It is supplied to the addition point 15 as the inverted value of the average target value, and further an amplification degree setting signal is supplied to the multiplier 16 based on the amplification degree calculated by the above-mentioned formula, and the load is started.

The crack length, which changes depending on the load, is measured each time, and the load amplitude target value and average target value are updated based on the measurement results.
There are cases where repeated loads are applied as shown in Figure b. Corresponding to the changes in each target value, the weighted average value signal causes its value to follow the average target value, but the amplitude of the weighted waveform signal and the amplification degree setting signal change their values as follows. In other words, when the load amplitude target value is decreased, the amplitude of the load waveform signal is not changed, but the amplitude is increased first, and the amplitude is actually applied to the test piece with respect to the amplitude target value. The amplitude can be increased to the maximum degree without reducing the amplitude too much. Then, with respect to the degree of width increase, the test piece is loaded with a width corresponding to the target width value.
The amplitude of the load waveform signal is finely adjusted. Therefore, the feedback signal always contains only the amplitude component, and the degree of amplification thereof is always automatically set to the maximum value in response to changes in the amplitude target value, thereby changing the setting input to the servo amplifier 12. The signal maintains a high degree of amplification, enabling high-precision control.

If the load amplifier 14 is provided with a function that allows continuous amplification from the outside, the present invention can be applied using a block diagram as shown in FIG.

Further, in the above embodiments, an example using load control was shown, but it goes without saying that the present invention can be applied to any physical quantity related to load such as displacement control, strain control, etc. as a control amount.

(f) Effects As explained above, according to the present invention, the average target value of the repetitive load is subtracted from the detection signal at the stage before the amplification means in the feedback loop, and the degree of amplification of the amplification means is , is automatically set to be as high as possible, so a waveform signal with a large amplitude can always be supplied as a target value signal without saturating the signal in the load amplifier like in the past, resulting in high control accuracy. can be maintained. In particular, compared to conventional equipment, the accuracy of fine amplitude control at a high average level is significantly improved, and this has a great effect on Kth tests and the like. In addition, since continuous automatic operation is possible, even when repeated loads are applied as shown in Figure 5a, there is no need to interrupt the test unlike conventional equipment, and there is no load fluctuation on the test object. reliability is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a flowchart showing a Kth test program by the computer system 18.
Fig. 3 is a block diagram showing the configuration of another embodiment of the present invention, Fig. 4 is a block diagram showing the configuration of a conventional device, and Figs. 5 a and b are examples of repeated loads to be applied to the test piece. This is a graph showing. 11... Hydraulic load mechanism, 12... Servo amplifier, 13... Load cell, 14... Load amplifier, 14... Addition point, 16... Multiplier, 17...
Comparison section, 18...computer system.

Claims (1)

[Claims] 1 A material testing machine equipped with a control mechanism that compares a detected value signal and a target value signal of a physical quantity that changes in relation to the load on the test object in a comparison section, and controls the load on the test object according to the deviation signal. , a control device for applying a repetitive load, comprising an average value signal generating means for generating an average value signal corresponding to an average value component of the repetitive load to be applied to a test object, and a waveform component of the repetitive load. waveform generating means for generating a repetitive waveform signal to be applied to the test object; variable amplifying means for inputting a signal obtained by subtracting the average value signal from the detected value signal and supplying the output to the comparing section; and amplification setting means for setting the amplification degree of the variable amplification means and the output waveform amplitude of the waveform generation means according to the amplitude value of the load, so that the repetitive load signal to be applied to the test object is repeated with the average value signal. The repeating waveform signal is supplied to the comparing section as a target value signal, and the difference between the repeating waveform signal and the output of the variable amplifying means is output as a deviation signal. , the amplification degree setting means sets the amplification degree in the variable amplification means,
A repetitive load control device for a materials testing machine, characterized in that the control mechanism is configured to set a signal to a maximum value at which the signal is not saturated.