JPH0145012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a material testing machine, and particularly to a material testing machine suitable for applying a dynamic load to a test piece.

(b) Prior art In conventional material testing machines in which the load is controlled by a servo mechanism, the transfer function of the entire system is not constant due to various conditions such as the testing machine itself, the test piece, the detector, etc. Therefore, each time a test is performed, adjustment using PID operation, etc. is required, and this adjustment work requires intuition and skill, as well as individual differences or human error, which may result in a decrease in measurement accuracy and control accuracy. There were problems with reliability. Additionally, mechanical parts and detectors generally have low resonant frequencies, so in order to perform tests based on flat frequency response characteristics, tests must be performed only in a frequency range that is approximately a fraction of the resonant frequency of the detector, etc. I couldn't do it. In general, the above-mentioned adjustment work involves preparing a dummy equivalent to the test object, attaching it to the test machine, and driving the test machine under the actual test conditions to check the error in the measured value signal relative to the target value signal. Adjust the gain as close to 0 as possible to optimally set the sensitivity of the system. Here, in a material testing machine, usually
The higher the average sensitivity of the system, the closer the error will be to 0, but due to the phase characteristics of the test object and the detector used,
When the sensitivity is increased, positive feedback becomes strong and hunting occurs. Therefore, during the above-mentioned adjustment, a method is adopted in which the gain is raised once to cause hunting, and then the gain is gradually lowered. If a dummy of the test object cannot be obtained, and the test object is a large structure, for example, it is necessary to perform the above-mentioned adjustment using the test object itself, but if hunting occurs at this time, There is a risk of damaging the test object and affecting the actual test results. This is especially dangerous when testing brittle materials such as concrete.

(c) Purpose The purpose of the present invention is to know the transmission characteristics of the entire system before testing without using dummies, even if there are uncertain transmission elements in the system, and to determine the frequency characteristics of the system electrically based on that. It is an object of the present invention to provide a material testing machine that can always perform highly reliable tests without individual differences by compensating the material and can obtain flat frequency characteristics in a wide frequency range.

(D) Configuration The material testing machine of the present invention has an oscillator that generates white noise, and selectively switches between the white noise from the oscillator and the waveform signal from the load wave generator, and supplies it to the control system as a target value signal. A target value signal switching means, a variable transmission element that is inserted into the control system and can change the transmission characteristics based on a command, and a test object inserted into the control system, and white noise in the control system. operates with the supply of
The apparatus is equipped with an arithmetic control means that calculates an inverse transfer function of the control system from the supplied white noise and the measured value signal in that state to change the transfer characteristic of the variable transfer element. The waveform signal from the load wave generator is supplied as the target value signal with the transfer characteristic of the variable transfer element set to a characteristic equivalent to the calculated inverse transfer function.

(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, and shows an example in which an electro-hydraulic type servo mechanism is adopted as the servo mechanism.

A target value signal for the load to be tested is supplied from a function generator 1 for generating load waves. A physical quantity related to the load acting on the test piece W, such as displacement, is detected by an extensometer 2 and a detection amplifier 3 attached to the test piece W, and the output, that is, the measured value signal, is the target value signal. The control device is configured to receive feedback to obtain a control operation signal. This control operation signal is
After passing through the variable transmission element 4, it is supplied to the servo amplifier 5, and the servo amplifier 5 controls the servo valve 6 according to the input signal, adjusts the flow rate of hydraulic oil from the hydraulic source 7, and drives the exciter 8. Control. The variable transfer element 4 can arbitrarily set its own transfer characteristics based on an external command, and can be configured by, for example, an equalizer.

As the target value signal to this system, in addition to the target value signal of the load to be tested from the load wave generation function generator 1 described above, white noise from the white noise oscillator 9 can be supplied, and any signal It is up to the arithmetic control unit 1 whether to input it as a target value signal.
The selection is made by the changeover switch 11 which is operated based on the command signal from 0. Arithmetic control unit 10
The system can be placed in test mode or characterization mode based on external commands.
That is, in the characteristics investigation mode, the above-mentioned changeover switch 11 is operated so that the white noise is input as the target value signal, and the white noise and the measured value signal at that time are input to calculate the transfer function of the entire system. An inverse function is calculated, the calculation result is supplied to the variable transfer element 4, and its transfer characteristic is set to a characteristic equivalent to the inverse transfer function of the entire system. In the test mode, the test machine is driven by inputting a load wave to be tested as a target value signal while maintaining the transfer characteristic of the variable transfer element 4 at the characteristic set in the characteristic investigation mode.

Note that the method of inputting white noise and a measured value signal of a system driven by the white noise and calculating the inverse transfer function of the system can be achieved by a known technique, such as a fast Fourier transformer. The arithmetic control unit 10 has these hardware, an output function to drive it, and a function to generate other control signals, and can be implemented by, for example, a computer. It can be configured as follows.

Next, the operation of the above-described embodiment of the present invention will be described along with its usage method.

After mounting the test piece W, first, the test machine is set to characteristic investigation mode and the test machine is excited with white noise. This excitation is desirably so small that it does not affect the test piece W. Due to the excitation by this white noise, the variable transfer element 4
The transfer characteristic of is set to be equivalent to the inverse transfer function of the system. Next, the test mode is set and the test machine is driven using the output from the load wave generation function generator 1 as a target value signal. As a result, the conventional system which had the frequency characteristics as shown in FIG. 2a becomes as shown in FIG. 2c by inserting the variable transmission element 4 whose characteristics are set as shown in FIG. 2b. The system is improved to have flat frequency characteristics over a wide range.
Then perform PID adjustment. At this time, even if the testing machine is operated under actual test conditions, there is no risk of hunting because the characteristics of the entire system are flat.

(f) Effects As explained above, according to the present invention, even if conventional detectors and mechanical parts with low resonance points are used,
The system is compensated for with flat frequency characteristics over a wide range, allowing highly reliable and stable tests to be performed. Furthermore, there is no need to use a dummy when adjusting the PID prior to the test, and there is no need to worry about hunting occurring during adjustment, and the average can be easily adjusted without damaging the test object and without relying on intuition or experience. Increase sensitivity and reduce error to 0
It is possible to approach the test results close to the actual test results, making it difficult for individual differences to interfere with the test results, making it particularly effective for testing brittle materials, and also making it possible to use it as an online fully automated material testing machine. Furthermore, since flat frequency characteristics over a wide range can be easily obtained, it is also possible to extend the limits in complex testing fields using actual stress, program waves, etc.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the embodiment of the present invention, and Fig. 2 is an explanatory diagram of the operation, in which Fig. a shows the frequency characteristics of the conventional system, and Fig. b shows the variable transmission in the characteristic investigation mode of the embodiment of the present invention. Frequency characteristics set for the elements, Figure c is a graph showing the frequency characteristics of the system in the test mode of the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Function generator for load wave generation, 2... Extensometer, 3... Detection amplifier, 4... Variable transfer element, 5
...Servo amplifier, 6...Servo valve, 8...
Exciter, 9... White noise oscillator, 10...
Arithmetic control unit, 11... changeover switch.

Claims (1)

[Claims] 1 A control operation signal is generated by feeding back a measured value signal of a physical quantity related to the load that is actually acting on the test object to a target value signal from a load wave generator that generates a waveform signal of the load to be applied to the test object. In a materials testing machine having a control system configured to obtain a a target value signal switching means for supplying a target value signal; a variable transmission element inserted into the control system and capable of changing the transmission characteristics based on a command; The control system operates with the white noise supplied to the system, calculates the inverse transfer function of the control system from the supplied white noise and the measured value signal in that state, and changes the transfer characteristic of the variable transfer element. and arithmetic control means, configured to supply the waveform signal from the load wave generator to the control system with the transfer characteristic of the variable transfer element set to a characteristic equivalent to the inverse transfer function. A material testing machine featuring: