JP2000019087A - Feedback control type material-testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent shock on control mode switching and at the same time to prevent an actuator from starting operation unexpectedly immediately after the control mode switching even when an actuator drive signal generation means includes an integral element in a feedback control type material-testing machine. SOLUTION: A control system 10 of a feedback control type material-testing machine is provided with signal-processing parts 134, 234, and 334 for generating an actuator drive signal according to an error signal Ee0 in its control loop, and the signal-processing parts include integral elements. The signal of the control system 10 is compensated for so that the level of an actuator drive signal Ea0 becomes essentially the same immediately before and after control mode switching and an error signal Ee0 becomes essentially zero immediately after the control mode switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback control type material testing machine for controlling a physical quantity to be controlled of a test piece in accordance with a target value function by a feedback control method.

[0002]

2. Description of the Related Art In order to perform various material tests, there is known a feedback control type material testing machine which controls a physical quantity to be controlled of a test piece in accordance with a target value function by a feedback control method.

The physical quantity to be controlled is variously selected according to the type of material test to be performed. For example, in a material test, the elongation of the test piece caused by the tensile load is continuously measured while controlling the tensile load applied to the test piece as a control target physical quantity. Further, the displacement of the chuck to which the test piece is attached or the elongation generated in the test piece may be used as the physical quantity to be controlled.

A control mode of a material testing machine in which a compression load or a tensile load is a physical quantity to be controlled is called a load control mode, and a control mode in which the displacement of a chuck is a physical quantity to be controlled is called a displacement control mode. The control mode in which the extension of the piece is set as the control target physical quantity is called an extension control mode.

In general, this kind of feedback control type material testing machine includes a target value function signal generating means for generating a target value function signal representing a target value function, and the target value function signal is inputted thereto. A control system is provided for controlling a selected one of a plurality of physical quantities of the test piece so as to follow the target value function signal.

Further, the control system is configured so that one of a plurality of control loops corresponding to each of a plurality of physical quantities can be selectively established. In many cases, the control system includes the following components. A. ~ F. Having.

That is, a. A plurality of sensors for detecting each of the plurality of physical quantities and generating a sensor signal corresponding to the magnitude of the detected physical quantity; b. Negative feedback signal generating means for generating a negative feedback signal according to the magnitude of the sensor signal; c. Difference generating means for receiving the target value function signal and the negative feedback signal and generating an error signal proportional to the difference between the signals; d. Actuator drive signal generating means for receiving an error signal and generating an actuator drive signal corresponding to the error signal; e. An actuator system for applying a test operation to the test piece in response to the actuator drive signal; and f. A control mode selection means for selecting and establishing one of the plurality of control loops so as to perform control to set a physical quantity corresponding to the established control loop as a control target physical quantity.

In the above description, the physical quantity to be controlled is
For example, the load applied to the test piece, the displacement of the chuck to which the test piece is attached, and the elongation generated in the test piece.

Further, as an actuator system, usually,
A hydraulic actuator having an electromagnetic servo valve to which an actuator drive signal is input is used.

Further, the negative feedback signal generation means, the difference generation means, and the actuator drive signal generation means can be configured as analog circuits using an operational amplifier. Recently, however, a D / A converter and an A / D converter have been proposed. A converter and a high-speed, high-performance microcomputer are used, and the microcomputer performs digital signal processing, so that these means are configured by software.In particular, the latter method is generally used. This is called digital signal processing.

When performing a material test using such a feedback-controlled material testing machine, it is often the case that
The control mode is switched in a series of test sequences.

For example, in a material test in which measurement is performed while applying a tensile load, which changes according to a target value function, to a test piece,
During the measurement, the material testing machine is operated in the load control mode, whereas when the measurement is completed, the control mode is usually switched to the displacement control mode in order to remove the test piece from the material testing machine.

The switching of the control mode is performed by switching a plurality of control loops that can be selectively established by the control system, and thereby the sensors used are switched.

For example, when switching from the load control mode to the displacement control mode, the sensor signal sent by the load sensor is used instead of the sensor signal sent by the load sensor until then. Become so.

Therefore, in general, when the control loop is switched, the magnitude of the negative feedback signal changes stepwise at that time, and as a result, the actuator drive signal changes abruptly. Therefore, if the control loop is simply switched, the actuator suddenly starts operating at the same time as the switching, so that a harmful shock is applied to the material testing machine or the test piece is damaged. Various inconveniences may occur.

In order to avoid such inconveniences, when switching the control mode, the control unit controls the hydraulic pressure of the actuator and / or the signal of the control system while monitoring the sensor signal. The operation was prevented. However, this method includes
There is a problem that it takes time to start the operation in the new control mode, and the operating efficiency of the material test is reduced.

Recently, a material testing machine in which a main part of a control system is digitally configured using digital signal processing technology is often used. In this case, it is necessary to add compensation to a signal of the control system. Because of its ease of use, another method is used.

According to the method, the magnitude of the actuator drive signal immediately after the switching of the control mode becomes the same as the magnitude of the actuator drive signal immediately before the switching by adding compensation to the target value function signal when the control mode is switched. It is to be.

[0019]

According to the conventional control mode switching method in which the actuator drive signal is compensated, the actuator drive signal generating means for generating the actuator drive signal according to the error signal is substantially provided. Good results are obtained when configured as a proportional element.

However, if the actuator drive signal generating means is configured to include an integral element in order to eliminate a steady-state error which necessarily accompanies the proportional element, a problem occurs in this conventional control mode switching method. I do.

More specifically, when the actuator drive signal generating means is configured as a proportional element, the magnitude of the target value function signal is controlled so that the magnitude of the actuator drive signal does not change before and after control mode switching. As long as is adjusted, the control system is already in a steady state immediately after the control mode switching.

On the other hand, if the actuator drive signal generating means includes an integral element, and the target value function signal is adjusted in such a manner, the control system is not activated immediately after the control mode switching. Not always in a steady state,
Generally, it is not in a steady state.

Therefore, immediately after the switching of the control mode, the actuator which has been stationary until then starts an unintended operation aiming at a steady state of the control system, and an undesired load is applied to the test piece. The test piece was sometimes damaged.

Further, in order to start operation control in a new control mode after switching, it is necessary to wait for the control system to settle down to a steady state once, so that it takes time for the test, and the operating efficiency of the material testing machine is increased. Had been reduced.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a feedback-controlled material testing machine of the kind described above, wherein the actuator drive signal generating means includes an integrating element. Even when the control mode is switched, it is preferable to prevent a situation in which a shock is applied to the material testing machine when the control mode is switched, and that the control system is already in a steady state immediately after the control mode is switched. To allow the operation control to be started immediately.

[0026]

According to a first aspect of the present invention, there is provided a feedback control type material testing machine for controlling a physical quantity to be controlled of a test piece according to a target value function by a feedback control method. In the feedback control type material testing machine, the target value function signal generating means for generating a target value function signal representing the target value function, and the target value function signal are input, and among a plurality of physical quantities related to the test piece, And a control system that controls one selected physical quantity according to the target value function signal, wherein the control system executes one of a plurality of control loops corresponding to each of the plurality of physical quantities. The control system comprises: a. A plurality of sensors for detecting each of the plurality of physical quantities and generating a sensor signal corresponding to the magnitude of the detected physical quantity; b. Negative feedback signal generating means for generating a negative feedback signal according to the magnitude of the sensor signal; c. Difference generating means for receiving the target value function signal and the negative feedback signal and generating an error signal proportional to the difference between the signals; d. Actuator drive signal generating means for receiving the error signal and generating an actuator drive signal corresponding to the error signal, wherein the generated actuator drive signal includes an integral component of the input error signal. Signal generation means; e. An actuator system for performing a test operation on the test piece in response to the actuator drive signal;
f. Control mode selecting means for selecting one of the plurality of control loops and establishing the control loop so that a control is performed with a physical quantity corresponding to the established control loop as a control target physical quantity; g. The signals of the control system such that the magnitude of the actuator drive signal becomes substantially the same immediately before and immediately after the control mode switching, and that the error signal becomes substantially zero immediately after the control mode switching. And compensation means for compensating for

According to a second aspect of the present invention, there is provided a feedback control type material testing machine, wherein the compensating means sets the target value so that the magnitude of the error signal immediately after the control mode switching becomes substantially zero. Means for performing offset compensation on the function signal, means for resetting the actuator drive signal generating means at the time of control mode switching, and means for adjusting the magnitude of the actuator drive signal immediately after the control mode switching to the actuator immediately before the control mode switching. Means for performing offset compensation on the actuator drive signal so as to be substantially equal to the magnitude of the drive signal.

According to a third aspect of the present invention, in the feedback control type material testing machine, the compensating means may determine that the magnitude of the negative feedback signal immediately after the control mode switching is equal to the negative feedback signal immediately before the control mode switching. Means for performing offset compensation on the negative feedback signal so as to be substantially equal in magnitude.

According to the feedback control type material testing machine of the present invention, when the control mode is switched, the signal of the control system is compensated so that the control mode is switched between immediately before and after the control mode switching. The magnitude of the actuator drive signal may be substantially the same, and the error signal may be substantially zero immediately after switching the control mode.

Therefore, even when the actuator drive signal generating means includes an integral element, it is possible to suitably prevent a shock from being applied to the material testing machine when the control mode is switched, and to control the control immediately after the control mode is switched. The operation control in the new control mode can be promptly started with the system already in a steady state.

Further, according to the feedback control type material testing machine of the present invention described in claim 2, the compensating means comprises:
A means for performing offset compensation on the target value function signal; a means for resetting the actuator drive signal generating means; and a means for performing offset compensation on the actuator drive signal. When the signal generation means and the actuator drive signal generation means are composed of digital signal processors each having a program memory and a product-sum operation unit, as is usually the case, it is necessary to change the programs of the digital signal processors. It is possible to carry out the present invention simply by adding.

According to a third aspect of the present invention, the compensating means includes:
Since the present invention comprises means for performing offset compensation on the negative feedback signal, the present invention can be implemented only by monitoring the negative feedback signal and controlling the load signal generating means. The present invention can easily be retrofitted with minimal modifications to the device.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a control system 10 of a feedback control type material testing machine according to a first embodiment of the present invention.

First, the mechanical part of the material testing machine will be briefly described. This material testing machine comprises a fixed-side load loading section fixed to a testing machine frame so as to be position-adjustable, and a movable-side load driven by a hydraulic actuator system. A load section is provided, and a test piece is mounted between the load load sections via a chuck, and the operation of the hydraulic actuator system is controlled to perform a test operation on the test piece. is there.

However, since the configuration of the mechanical part of the material testing machine is not important for the present invention, the entire mechanical part is not shown, and the servo valve S / V and the hydraulic valve of the hydraulic actuator system are simply shown in the figure. One block 12 shows the hydraulic actuator ACT, the chuck driven by the hydraulic actuator system, and the test piece CHK / TP attached to the chuck.

Accordingly, the block 12 represents an element which receives an actuator drive signal supplied to the servo valve S / V and outputs a physical quantity relating to the test piece TP.

In the embodiment of FIG. 1, the physical quantities of the test piece TP that can be controlled by the control system 10 are the load applied to the test piece TP, the displacement of the chuck CHK to which the test piece TP is attached, and This is the elongation that occurs in the test piece TP, and one of those physical quantities is selected as the control target physical quantity and becomes the output of the control system 10. Control system 10
Has three sensors for detecting the three physical quantities, respectively.

The load applied to the test piece TP is detected by a load sensor 14 comprising a load cell attached to one of the load application parts and a bridge circuit attached thereto, and the load sensor 14 detects the magnitude of the detected load. Is generated as a load sensor signal SLOAD which is an analog electric signal corresponding to.

Further, a chuck CH to which the test piece TP is attached
The displacement of K is detected by a displacement sensor 16 using a potentiometer or the like, and the displacement sensor 16 generates a displacement sensor signal SDISP which is an analog electric signal corresponding to the magnitude of the detected displacement.

The elongation generated on the test piece TP is detected by an elongation sensor 18, and this elongation sensor 18
A stretch sensor signal SELNG, which is an analog electric signal corresponding to the magnitude of the detected stretch, is generated.

Of the components of the control system 10 shown in FIG. 1, the block 12 and the sensors 14 to 18 described above are used.
The other components are for generating or processing signals electrically. In the illustrated embodiment, the components are five digital signal processors DSP0.
DSP4 and a control computer 20 for monitoring the input / output signals of the digital signal processors and controlling the operation of the digital signal processors.
It is composed of

5 digital signal processors DS
Each of P0 to DSP4 has a general configuration in which a CPU, a RAM, a ROM, a multiply-accumulate unit, and the like are combined, and the functions thereof are more important than the specific configuration. In FIG. 2, the function of each digital signal processor is represented by a combination of several functional elements.

It is obvious to those skilled in the art how to configure the hardware of the digital signal processor and how to create the program in order to obtain the functions of each digital signal processor described below. Therefore, the description thereof is omitted.

The DSP 0 has a function signal generator 22 for generating a target value function signal Ei (t). The target value function signal Ei (t) is a signal representing the target value of the physical quantity to be controlled as a function of time.

The function signal generating section 22 has a connection symbol C
01 is controlled by the control computer 20, so that the function signal generator 22 and the control computer 20 generate a target value function signal generating means for generating a target value function signal representing a target value function. Is configured.

The target value function signal Ei (t) may be generated as a ramp function for a tensile strength test or as a sine function for a fatigue strength test in accordance with a command from the control computer 20. It may be generated, or even generated as any other suitable function for loading and unloading the test strip TP.

The DSP 0 further has an adder 24 and an offset signal generator 26. Offset signal generator 26
Is controlled by the control computer 20 as shown by a connection symbol C02 in the drawing, and the target value function signal E
The offset signal DOS to be added to i (t) is generated.

When the control computer 20 sets the offset signal DOS to a value other than zero (positive or negative), the adder 24 adds the offset signal DOS to the target value function signal Ei (t). .

Therefore, the adder 24, the offset signal generator 26, and the control computer 20 constitute means for performing offset compensation on the target value function signal Ei (t). This offset compensation will be described later in more detail.

Three digital signal processors DS
P1 to DSP3 are all controlled by the control computer 20.

Each of the DSP1 to DSP3 has the test piece T
Sensor signals corresponding to each of the three physical quantities related to P are input, and these DSP1 to DSP3 form part of respective control loops for controlling the respective physical quantities corresponding to the sensor signals. .

More specifically, the load sensor signal SLOAD is input to the DSP 1, and the DSP 1 forms a part of a load control loop. The DSP 2 receives a displacement sensor signal SDISP, and the DSP 2 forms a part of a displacement control loop. The extension sensor signal SELNG is input to the DSP 3, and the DSP 3 forms a part of the extension control loop.

These three digital signal processors DSP1 to DSP3 generally have their operation parameters set to different set values, respectively, but their functions are similar to each other. Therefore, in the following description,
Only DSP1 will be described in detail, and DSP2 and DS
Regarding P3, a reference number corresponding to the corresponding element in the drawing is attached, and detailed description is omitted.

The DSP 4 is controlled by the control computer 20 as indicated by a connection symbol C41 in the drawing, and the actuator drive signals Ea1 to Ea, which are digital electric signals output by the DSP1 to DSP3, respectively.
One of the three types is selected, and the selected actuator drive signal is converted into an analog signal. The DSP 4 will be described later in detail.

Now, the DSP 1 will be described in more detail. The DSP 1 has an A / D converter 130. The A / D converter 130 digitizes the analog load sensor signal SLOAD received from the load sensor 14 by sampling it at a predetermined sampling rate (for example, 100 μsec).

Therefore, the A / D converter 130 is a proportional element for transmitting a digital signal having a magnitude proportional to the magnitude of the input load sensor signal SLOAD, and its proportional coefficient (gain KC1) is used for control. Computer 2
It can be adjusted by a command from 0.

The output of the A / D converter 130 is used as a negative feedback signal FB1 of the load control loop. Therefore, the A / D converter 130 and the control computer 20 constitute a negative feedback signal generating means for generating a negative feedback signal FB1 corresponding to the magnitude of the load sensor signal SLOAD.

The gain KC1 is a feedback gain in the load control loop, and is set to a value that optimizes the control characteristics of the load control loop. DSP2 and D
SP3 also has similar A / D converters 230 and 330, and their feedback gains are represented by KC2 and KC3.

The DSP 1 has a comparator 132. The comparator 132 receives the target value function signal Ei (t) and the negative feedback signal FB1 from the DSP0 and the A / D converter 130, respectively, and receives an error signal Ee1 proportional to the difference between these signals.
Of the difference generating means for generating. Also, DSP
2 and DSP 3 also have similar comparators 232 and 332.

The DSP 1 has a signal processing unit 134. The signal processing unit 134 is controlled by the control computer 20 as indicated by a connection symbol C11 in the drawing, and performs processing on an error signal Ee1 input from the comparator 132 to generate an actuator drive signal Ea1. It is.

Therefore, the signal processing section 134 and the control computer 20 constitute an actuator drive signal generating means for receiving an error signal and generating an actuator drive signal corresponding to the error signal.

In particular, the signal processing section 134 converts the generated actuator drive signal Ea1 into an error signal E
It is configured to include the integral component of e1, and more specifically, is configured as a proportional / integral element.

By making the signal processing section 134 for generating the actuator drive signal Ea1 include an integral element,
It is possible to eliminate the steady-state deviation, thereby improving the control accuracy of the load control loop.

The proportional coefficient (gain KF 1) of the proportional / integral element constituting the signal processing section 134 can be adjusted by a command from the control computer 20. This gain KF1 is a forward gain in the load control loop, and is set to a value that optimizes the control characteristics of the load control loop.

The actuator drive signal Ea1 is
It can be reset by a command from the control computer 20, and is reset at the time of control mode switching described later. Therefore, by the control computer 20,
Means is provided for resetting the actuator drive signal generating means when the control mode is switched.

DSP2 and DSP3 also have similar signal processing units 234 and 334, and their gains are
2 and KF3.

The DSP 1 has an adder 136 and an offset signal generator 138. Offset signal generator 13
Numeral 8 is controlled by the control computer 20 as indicated by a connection symbol C12 in the figure, and generates an offset signal AOS1 to be added to the actuator drive signal Ea1.

If the control computer 20 sets the offset signal AOS1 to a value other than zero (positive or negative), the offset signal AOS1 is added to the adder 136.
Is added to the actuator drive signal Ea1.

Therefore, the adder 136, the offset signal generator 138, and the control computer 20 constitute means for performing offset compensation on the actuator drive signal Ea1. This offset compensation will be described later in more detail.

Regarding DSP2 and DSP3, those constituent elements are denoted by reference numerals obtained by changing the first digit of the reference number of the corresponding element of DSP1 from “1” to “2” and “3”, respectively. It is shown attached.

The functions of these DSP2 and DSP3 are similar to the functions of DSP1 as described above.
The signal processing units 234 and 334 of P2 and DSP3
Like the signal processing unit 134 of SP1, it is configured as a proportional / integral element.

In these DSP2 and DSP3, the error signal is represented by Ee2 and Ee3, the negative feedback signal is represented by FB2 and FB3, the actuator drive signal is represented by Ea2 and Ea3, and the offset signal is represented by AOS2 and AOS3. I have.

The negative feedback signals FB1 to FB1 of the DSP1 to DSP3
FB3 is represented by connection symbols M11, M21, and M31 in the figure.
Is monitored by the control computer 20 as shown in FIG. The actuator drive signals Ea1 to Ea3 output from the DSP1 to DSP3 are input to the DSP4, and the connection symbols M12 and M2
2, and the control computer 20 as indicated by M32.
Being monitored by

The DSP 4 generates three actuator drive signals Ea 1 to Ea 1 in accordance with a command from the control computer 20.
It has a selector 40 for selecting one of Ea3 and a D / A converter 42 for converting the selected digital actuator drive signal into an analog actuator drive signal Ea0.

The actuator drive signal Ea0 output from the DSP 4 is supplied to the servo valve S / V of the hydraulic actuator ACT to drive the servo valve S / V. Thereby, the actuator system included in the block 12 of FIG. 1 responds to the actuator drive signal Ea0,
A test operation is added to the test piece TP.

As is clear from the above description, DSP1
For example, if the actuator drive signal Ea1 is selected from among the actuator drive signals Ea1 to Ea3 sent from the DSP 3, the load sensor 14 and the DS
A load control loop including P1 is established,
The control mode of the material testing machine is the load control mode. Then, by selecting another actuator drive signal, it is possible to switch to a control mode corresponding to the selected actuator drive signal.

Accordingly, the selector 40 and the control computer 20 constitute control mode selecting means, and this control mode selecting means is provided for one of a plurality of control loops.
By selecting and establishing one of them, the control is performed with the physical quantity corresponding to the established control loop as the control target physical quantity.

As is apparent from the above description, the control system 10 is configured to selectively establish one of a plurality of control loops corresponding to a plurality of physical quantities for the test piece TP. That is, one selected physical quantity is controlled so as to follow the target value function signal.

In the feedback control type material testing machine having the above configuration, when the control mode is switched, the actuator drive signal changes stepwise at the same time as the control mode is switched, so that the hydraulic actuator ACT suddenly operates at a high speed. In order to prevent the inconvenience of starting and the inconvenience of starting the unintended operation of the hydraulic actuator ACT immediately after the switching to aim for the steady state of the control system 10 including the integral element, the following procedure is performed. I want to run.

The procedure is such that the magnitude of the actuator drive signal Ea0 becomes substantially the same immediately before and immediately after the control mode switching, and the error signal becomes substantially zero immediately after the control mode switching. Then, compensation is applied to the signal of the control system 10.

This will be described below with reference to a specific example. Here, the process of applying a repetitive load to the test piece TP in the load control mode for the fatigue strength test is described. The case where the load control mode is switched to the displacement control mode in order to remove the test piece TP from the material testing machine when finished is described.

When the control mode is switched, the control computer 20 reads the negative feedback signal FB1 of the load control loop from the DSP 1 immediately before the switching, and outputs the negative feedback signal FB2 of the displacement control loop from the DSP 2 immediately before the switching. read.

Then, immediately after the switching, a new offset signal D to be output from the offset signal generation unit 26 of the DSP 0
By setting OS (new) to an appropriate value, the error signal Ee2 of the displacement control loop becomes substantially zero immediately after switching.

In this case, since the control is being performed in the load control mode immediately before the switching, the error signal Ee1 of the load control loop is substantially zero. Therefore, using the value of the offset signal DOS (old) output from the offset signal generating unit 26 of the DSP 0 immediately before the switching, FB1−DOS (old) = FB2−DOS (n
By setting the value of DOS (new) to be ew), the error signal Ee2 of the new control loop (displacement control loop) immediately after the switching can be made substantially zero.

In parallel with the above, the control computer 20 reads the actuator drive signal Ea1 output from the DSP 1 immediately before the switching of the control mode, and immediately after the switching, the signal processing unit 2 of the DSP 2
The actuator drive signal output from the signal processor 234 is reset to zero.

At the same time, the control computer 20
The actuator drive signal output from the signal processing unit 234 is subjected to an appropriate offset compensation through the adder 236 and the offset signal generation unit 238 of the DSP 2 so that the post-offset compensation output from the DSP 2 to the DSP 4 is performed. The magnitude of the actuator drive signal Ea2 of
The magnitude is set to be substantially equal to the magnitude of the actuator drive signal Ea1 read earlier.

As a result, the magnitude of the actuator drive signal Ea1 used immediately before the switching of the control mode and the magnitude of the actuator drive signal Ea
2 becomes substantially equal, so that the magnitude of the actuator drive signal Ea0 supplied to the servo valve S / V can be made substantially the same immediately before and immediately after the control mode switching.

Therefore, since the magnitude of the actuator drive signal Ea0 does not change before and after the control mode switching, there is no possibility that the hydraulic actuator ACT suddenly starts a high-speed operation when the control mode is switched, and the error signal is not controlled by the control mode. Since it becomes zero immediately after the switching, the control loop corresponding to the new control mode is already in a steady state at that time, and therefore, even if the control loop includes the integral element, the hydraulic pressure is not changed after the switching of the control mode. Actuator AC
T does not start an unintended operation aiming at the steady state of the control system 10.

Next, a second embodiment of the present invention will be described. FIG. 2 is a block diagram showing a control system 10 'of a feedback control type material testing machine according to a second embodiment of the present invention. Since the components of the mechanical part of the material testing machine are the same in the first embodiment and the second embodiment, the same reference numerals are given and the detailed description is omitted.

In the second embodiment, too, the control system 10 '
The physical quantity of the test piece TP that can be controlled is
The load applied to the test piece TP, the displacement of the chuck CHK to which the test piece TP is attached, and the elongation generated in the test piece TP. One of those physical quantities is selected as a control target physical quantity, and the control system 10 '.

The control system 10 'includes three sensors for detecting the above three physical quantities, respectively.
Since these sensors are the same as those of the first embodiment, they are denoted by the same reference numerals. Further, the sensor signals generated by these sensors are the same as those described in the first embodiment.

[0092] Of the components of the control system 10 'shown in Fig. 2, components other than the block 12 and the sensors 14 to 18 are for generating or processing signals electrically. In the form, the components are two digital signal processors DSP0 'and DSP1
And a control computer 20 'for monitoring the input / output signals of the digital signal processors and controlling the operations of the digital signal processors.

Two digital signal processors DS
Each of P0 'and DSP1' is a CPU, RAM, RO
M, and a general configuration in which a multiply-accumulate unit and the like are combined. Since the function is more important than the specific configuration, FIG. It is represented by a combination of these functional elements.

It is obvious to those skilled in the art how to configure the hardware of the digital signal processor and how to create the program in order to obtain the functions of each digital signal processor described below. Therefore, the description thereof is omitted.

DSP0 'is the target value function signal Ei (t)
Is generated. The target value function signal Ei (t) is a signal representing the target value of the physical quantity to be controlled as a function of time.

The function signal generating section 22 has a connection symbol C
01, the control signal is generated by the control computer 20 '. Therefore, the function signal generator 22 and the control computer 20' generate a target value function signal for generating a target value function signal representing the target value function. Means are configured.

The target value function signal Ei (t) may be generated as a ramp function for a tensile strength test or a sine function for a fatigue strength test according to a command from the control computer 20 '. May be generated as
Further, it may be generated as another appropriate function for mounting and removing the test piece TP.

The DSP0 'of FIG. 2 is different from the DSP0 of the embodiment of FIG. 1 in that it does not include means for performing offset compensation on the target value function signal Ei (t).

The other digital signal processor DSP1 'has a function substantially corresponding to the whole of the four digital signal processors DSP1 to DSP4 of the embodiment shown in FIG. The components corresponding to the functional elements included in the DSP1 to DSP4 are denoted by the same reference numerals.

The DSP 1 'is controlled by a control computer 20', and receives sensor signals corresponding to each of the three physical quantities relating to the test piece TP.
The DSP 1 'constitutes a part of each control loop for controlling each physical quantity corresponding to the sensor signal.

Therefore, the load sensor signal SLOAD, the displacement sensor signal SDISP, and the elongation sensor signal SELNG are input to the DSP 1 '.

The DSP 1 'has three A / D converters 1
30, 230, and 330. These A / D converters 130, 230, and 330 respectively include sensor signals SLOAD, SDISP, and SEL, which are analog electric signals.
NG is set to a predetermined sampling rate (for example, 100 μsec)
Sampling and digitization.

Therefore, these A / D converters 130,
Numerals 230 and 330 are proportional elements for transmitting digital signals of a magnitude proportional to the magnitude of the input sensor signal, and their proportional coefficients (gains KC1, KC2, KC3)
Can be adjusted by a command from the control computer 20 '.

The A / D converters 130, 230,
The outputs of 330 are negative feedback signals FB1, FB2, FB of the load control loop, the displacement control loop, and the elongation control loop, respectively.
Used as 3. Accordingly, each A / D converter and the control computer 20 'constitute a negative feedback signal generating means for generating a negative feedback signal according to the magnitude of each sensor signal. Further, gains KC1, KC2, K
C3 is a feedback gain in each control loop, and is set to a value that optimizes the control characteristics of the corresponding control loop.

The DSP 1 'has three adders 144 and 24.
4, 344, and three offset signal generators 146, 246, 346 associated with each of them.
The offset signal generators 146, 246, 346 are controlled by the control computer 20 'as shown by connection symbols C11, C12, C13 in the figure, and the offsets to be added to the negative feedback signals FB1, FB2, FB3, respectively. It generates signals EOS1, EOS2 and EOS3.

The control computer 20 'sets the offset signals EOS1 to EOS3 to a value other than zero (positive or negative).
Once set to the magnitude, these offset signals EOS
1 to EOS3 are added to the negative feedback signals FB1 to FB3 by adders 144, 244 and 344, respectively.

Therefore, the adders 144, 244, 344
And offset signal generators 146, 246, and 346;
With the control computer 20 ', the negative feedback signals FB1, F
Means for performing offset compensation on B2 and FB3 is configured. This offset compensation will be described later in more detail.

The DSP 1 'selects one of the three negative feedback signals FB1 to FB3 according to a command from the control computer 20' as indicated by the connection symbol C14, and is selected by the selector 40. And a comparator 32 to which the negative feedback signal FB0 is input.

The comparator 32 receives the above-mentioned target value function signal Ei (t) from the DSP 0 ′.
2 generates an error signal Ee0 proportional to the difference between these signals. Therefore, the comparator 32 constitutes a difference generating means similar to the comparator 132 in the first embodiment.

The DSP 1 'has a signal processing unit 34.
The signal processing unit 34 is controlled by the control computer 20 ′ as indicated by a connection symbol C15 in the drawing, and performs processing on an error signal Ee0 input from the comparator 32 to generate an actuator drive signal Ea. Things.

Therefore, the signal processing section 34 and the control computer 20 'constitute an actuator drive signal generating means for receiving an error signal and generating an actuator drive signal corresponding to the error signal.

The signal processing unit 34 is configured such that the generated actuator drive signal Ea includes an integral component of the input error signal Ee0, similarly to the signal processing units 134, 234, and 334 in the first embodiment. More specifically, it is configured as a proportional / integral element.

The signal processing section 34 for generating the actuator drive signal Ea includes an integral element so that a steady-state deviation can be eliminated, thereby improving the control accuracy of the control loop.

The proportional coefficient (ie, forward gain KF 0) and integration time constant (ie, T 0) of the proportional / integral elements constituting the signal processing section 34 are controlled by the control computer 20.
'Can be adjusted by a command from'. KF0 and T0 are set to values that optimize the control characteristics of the control loop according to the currently selected physical quantity to be controlled.

The DSP 1 'of the embodiment shown in FIG. 2 is different from the DSP 1, DSP 2 or DSP 3 of the embodiment shown in FIG. 1 in that it does not include means for performing offset compensation on the actuator drive signal.

Negative feedback signals FB1 to FB3 of DSP1 '
Are monitored by the control computer 20 ′ as indicated by connection symbols M11 to M13 in the figure, and the actuator drive signal Ea output from the signal processing unit 34 is
Is also monitored by the control computer 20 'as shown by a connection symbol M14 in the figure.

The DSP 1 'has a D / A converter 42. The D / A converter 42 converts a digital actuator drive signal Ea output from the signal processing section 34 into an analog actuator drive signal Ea0. is there.

The analog actuator drive signal Ea0 output from the D / A converter 42 is supplied to the servo valve S / V of the hydraulic actuator ACT, and the servo valve S / V
/ V. Thus, the actuator system included in the block 12 of FIG. 2 performs a test operation on the test piece TP in response to the actuator drive signal Ea0.

As apparent from the above description, for example, if the negative feedback signal FB1 is selected from the negative feedback signals FB1, FB2, FB3 sent from the A / D converters 130, 230, 330, As a result, a load control loop including the load sensor 14 and the DSP 1 'is established, and the control mode of the material testing machine becomes the load control mode. Then, by selecting another negative feedback signal, it is possible to switch to a control mode corresponding to the selected negative feedback signal.

Accordingly, the selector 40 and the control computer 20 'constitute control mode selecting means, and this control mode selecting means comprises one of a plurality of control loops.
By selecting and establishing one of them, the control is performed with the physical quantity corresponding to the established control loop as the control target physical quantity.

As is clear from the above, the control system 10 'is configured to selectively establish one of a plurality of control loops corresponding to a plurality of physical quantities for the test piece TP. And controls the selected one physical quantity so as to follow the target value function signal.

In the feedback control type material testing machine having the configuration shown in FIG. 2, when the control mode is switched, the actuator drive signal changes stepwise at the same time as the control mode is switched, so that the hydraulic actuator ACT suddenly operates at a high speed. In order to prevent the inconvenience of starting the operation and the inconvenience of starting the unintended operation of the hydraulic actuator ACT aiming at the steady state of the control system 10 'including the integral element immediately after the switching, the following will be described. The steps are to be performed.

The outline of the procedure is similar to that of the feedback control type material tester of the first embodiment, and the actuator drive signal Ea is obtained immediately before and after the control mode switching.
0 is substantially the same, and the error signal is substantially zero immediately after the control mode switching,
The compensation is applied to the signal of the control system 10 ', but the details of the procedure are different from those of the first embodiment.

This will be described in accordance with the same situation as exemplified for the first embodiment, that is, the repetition of the test specimen TP which has been performed in the load control mode for the fatigue strength test. A description will be given of a case in which the return load application process is completed and the load control mode is switched to the displacement control mode in order to remove the test piece TP from the material testing machine.

When the control mode is switched, first, immediately before the switching, the control computer 20 transmits the negative feedback signal FB1 before the offset compensation of the load control loop and the negative feedback signal FB2 before the offset compensation of the displacement control loop. And read.

Then, using the value of the negative feedback signal and the value of the offset signal EOS1 of the load control loop, the offset signal generation unit 246 of the displacement control loop immediately after switching.
The error signal Ee0 of the new control loop (displacement control loop) becomes substantially zero immediately after the switching of the control mode by appropriately determining the value of the offset signal EOS2 to be output from the controller.

In this case, since the control is being performed in the load control mode immediately before the control mode is switched, the error signal Ee0 is substantially zero. Therefore, FB1 +
When the value of EOS2 is determined so that EOS1 = FB2 + EOS2, the magnitude of the negative feedback signal input to the comparator 32 immediately after the switching of the control mode causes the negative feedback signal input to the comparator 32 immediately before the switching. The error signal Ee at the time immediately after the switching is substantially equal to the signal magnitude.
0 can be made substantially zero.

Further, since the signal processing section 34 continues to generate the actuator drive signal Ea based on the error signal Ee0 even before the control mode is switched,
If the error signal Ee0 is zero before and after the switching,
The actuator drive signal Ea does not change by switching the control mode.

Accordingly, since the magnitude of the actuator drive signal Ea does not change before and after the control mode switching, there is no possibility that the hydraulic actuator ACT suddenly starts high-speed operation when the control mode is switched, and the error signal is not controlled by the control mode. Since it becomes zero immediately after the switching, the control loop corresponding to the new control mode is already in a steady state at that time, and therefore, even if the control loop includes the integral element, the hydraulic pressure is not changed after the switching of the control mode. Actuator ACT
Does not start an unintended operation aiming at the steady state of the control system 10 '.

When the switching procedure is completed, the control computer 20 sets the gain KF0 and the integration constant T0 of the signal processing unit 34 to a new control mode (displacement control mode).
And a desired target value function signal E
The control in the displacement control mode is started by generating i (t).

Here, differences in operation and effect between the first embodiment and the second embodiment will be described. In each of the control systems 10 and 10 ', the signal processing units 134, 234, 334, and 3 execute the most complicated processing.
4.

In the first embodiment, a dedicated signal processing unit 134, 234, 334 is provided for each physical quantity to be controlled.
Therefore, the configuration of these signal processing units can be configured to increase the ratio of hardware and reduce the ratio of software, and therefore, high-speed processing is possible and more excellent control characteristics are achieved. Can be achieved.

On the other hand, in the second embodiment, since the same signal processing unit 34 is shared by a plurality of physical quantities to be controlled, the configuration is highly dependent on software and the processing speed is inferior. Become.

However, the negative feedback signals FB1 to FB3
The present invention can be implemented with only minor modifications to existing feedback-controlled material testing machines, since the features of the present invention can be incorporated by simply performing offset compensation on Can be said to be generally more advantageous than the first embodiment.

[0135]

As described above, the feedback control type material testing machine of the present invention according to the first aspect controls the physical quantity to be controlled of the test piece in accordance with the target value function by the feedback control type. In the tester, a target value function signal generating means for generating a target value function signal representing the target value function, the target value function signal being input, and a selected one of a plurality of physical quantities relating to the test piece And a control system for controlling the control value so as to follow the target value function signal, wherein the control system can selectively establish one of a plurality of control loops corresponding to each of the plurality of physical quantities. Wherein the control system comprises: a. A plurality of sensors for detecting each of the plurality of physical quantities and generating a sensor signal corresponding to the magnitude of the detected physical quantity; b. Negative feedback signal generating means for generating a negative feedback signal according to the magnitude of the sensor signal; c. Difference generating means for receiving the target value function signal and the negative feedback signal and generating an error signal proportional to the difference between the signals; d. Actuator drive signal generating means for receiving the error signal and generating an actuator drive signal corresponding to the error signal, wherein the generated actuator drive signal includes an integral component of the input error signal. Signal generation means; e. An actuator system for applying a test operation to the test piece in response to the actuator drive signal; f. Control mode selection means for selecting one of the plurality of control loops and establishing the control loop so that control is performed with a physical quantity corresponding to the established control loop as a control target physical quantity;
g. The signals of the control system such that the magnitude of the actuator drive signal becomes substantially the same immediately before and immediately after the control mode switching, and that the error signal becomes substantially zero immediately after the control mode switching. And a compensating means for compensating for.

Therefore, by compensating the signals of the control system when switching the control mode, the magnitude of the actuator drive signal becomes substantially the same immediately before and immediately after the control mode switching, and Immediately after the control mode switching, the error signal can be made substantially zero. Therefore, even when the actuator drive signal generating means includes an integral element, it is possible to suitably prevent a situation in which a shock is applied to the material testing machine when the control mode is switched, and the control system is already in place immediately after the control mode is switched. The operation control in the new control mode can be started promptly in the steady state.

According to a second aspect of the present invention, in the feedback control type material testing machine, the compensating means sets the target value so that the magnitude of the error signal immediately after the control mode switching becomes substantially zero. Means for performing offset compensation on the function signal, means for resetting the actuator drive signal generating means at the time of control mode switching, and means for adjusting the magnitude of the actuator drive signal immediately after the control mode switching to the level of the actuator immediately before the control mode switching. Means for performing offset compensation on the actuator drive signal so as to be substantially equal to the magnitude of the drive signal.

Therefore, the compensating means includes means for performing offset compensation on the target value function signal, means for resetting the actuator drive signal generating means, and means for performing offset compensation on the actuator drive signal. In the case where the target value function signal generating means and the actuator drive signal generating means are constituted by a digital signal processor having a program memory and a product-sum operation unit, as is usually the case, The present invention can be implemented only by changing the programs of the digital signal processors.

According to a third aspect of the present invention, in the feedback control type material testing machine, the compensating means may determine that the magnitude of the negative feedback signal immediately after the control mode switching is smaller than that of the negative feedback signal immediately before the control mode switching. The negative feedback signal is offset-compensated so as to be substantially equal in magnitude.

Therefore, since the compensating means comprises means for performing offset compensation on the negative feedback signal, the present invention can be implemented only by monitoring the negative feedback signal and controlling the load signal generating means. Therefore, the present invention can easily be retrofitted with minimal modifications to existing feedback material testing machines.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system of a feedback control type material testing machine according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a control system of a feedback control type material testing machine according to a second embodiment of the present invention.

[Explanation of symbols]

10, 10 'control system 14 load sensor 16 displacement sensor 18 elongation sensor 20 control computer 22 function signal generation unit 24 adder 26 offset signal generation unit 32 comparator 34 signal processing unit 40 selector 42 D / A converter 130, 230, 330 A / D converter 132,232,332 Comparator 134,234,334 Signal processing unit 136 Adder 138 Offset signal generator 144,244,344 Adder 146,246,346 Offset signal generator S / V Servo valve ACT Hydraulic actuator CHK Chuck TP Test piece DSP0-DSP4 Digital signal processor DSP0 ', DSP1' Digital signal processor

Claims (3)

[Claims] 1. A feedback control type material testing machine for controlling a physical quantity to be controlled of a test piece in accordance with a target value function by a feedback control method, wherein a target value function signal generating a target value function signal representing the target value function is generated. Means, and a control system to which the target value function signal is input and which controls a selected one of a plurality of physical amounts related to the test piece so as to follow the target value function signal, the control system Is configured to selectively establish one of a plurality of control loops corresponding to each of the plurality of physical quantities, and the control system includes: a. A plurality of sensors that detect each of the plurality of physical quantities and generate a sensor signal corresponding to the magnitude of the detected physical quantity; b. Negative feedback signal generating means for generating a negative feedback signal according to the magnitude of the sensor signal; c. Difference generating means for receiving the target value function signal and the negative feedback signal and generating an error signal proportional to the difference between the signals; d. Actuator drive signal generating means for receiving the error signal and generating an actuator drive signal corresponding to the error signal, wherein the generated actuator drive signal includes an integral component of the input error signal. Signal generation means; e. An actuator system for applying a test operation to the test piece in response to the actuator drive signal; f. Control mode selection means for selecting one of the plurality of control loops and establishing the control loop so that control is performed using a physical quantity corresponding to the established control loop as a control target physical quantity; g. The signals of the control system such that the magnitude of the actuator drive signal becomes substantially the same immediately before and immediately after the control mode switching, and that the error signal becomes substantially zero immediately after the control mode switching. And a compensating means for compensating for: a feedback-controlled material testing machine. 2. The system according to claim 1, wherein the compensating means performs offset compensation on the target value function signal so that the magnitude of the error signal immediately after the control mode switching becomes substantially zero. Means for resetting said actuator drive signal generating means, and said actuator drive signal is generated such that the magnitude of the actuator drive signal immediately after control mode switching is substantially equal to the magnitude of the actuator drive signal immediately before control mode switching. 2. A feedback control type material testing machine according to claim 1, further comprising means for performing offset compensation on the material. 3. The compensation means performs offset compensation on the negative feedback signal such that the magnitude of the negative feedback signal immediately after the control mode switching is substantially equal to the magnitude of the negative feedback signal immediately before the control mode switching. 2. A feedback controlled material testing machine according to claim 1, further comprising means for applying.