JPS6341495B2 - - 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 is applied to testing machines that apply repeated loads to samples, such as fatigue testing machines.

(b) Prior art Figure 1 shows a conventional example in block diagram form. sine wave,
The output of a function generator 1 that generates an analog signal using a periodic function wave with a constant amplitude repeating wave such as a triangular wave is used as a setting signal, and the output of a signal detector 2 that detects displacement, velocity, acceleration, etc. of the sample W is used as a sensor amplifier 3. The amplified actual signal is used as a feedback signal, a comparator 4 detects the deviation of the feedback signal from the set signal, and an analog closed loop circuit is formed in which the servo amplifier 5 drives the load device 6 according to the deviation, and the deviation becomes zero. The load device is controlled as follows.

However, in such a circuit configuration, as a characteristic of analog control, the deviation between the average value of the actual signal and the set average value often does not become zero due to the gain of the servo amplifier, the constant of the integral element, or the drift of the circuit. . Furthermore, depending on the system, it may be necessary to lower the gain in order to avoid resonance, and in such cases the deviation becomes even more pronounced.

(c) Purpose An object of the present invention is to provide a control device for a material testing machine in which the deviation between a set value and a measured value is completely zero.

(d) Configuration In summary, the control device for the material testing machine of the present invention outputs a periodic function having a predetermined average value and amplitude waveform as an analog signal, and outputs measured values regarding the displacement of the sample, displacement, velocity, acceleration, etc. In a feedback control system in which a load device is driven based on the deviation from a predetermined periodic function, an A/D converter converts the analog signal fed back into a digital signal, and a measured value such as the average value of the periodic function is used. A digital memory that stores the above A/D
Calculate the actual average value, etc. from the output of the converter, find the deviation of the actual average value, etc. from the set average value, etc. stored in the digital memory, and change the analog output of the above time function in a direction to cancel the deviation. The present invention is characterized in that it is provided with function output adjustment means for adjusting the function output.

(E) Embodiment FIG. 2 shows a block diagram of an embodiment of the present invention, and FIG. 3 shows a flowchart of a program for controlling the CPU shown in FIG. 2.

Hereinafter, parts that are different from the conventional example shown in FIG. 1 will be explained, and the same parts will be denoted by the same reference numerals.

A/D converter 7 converts the feedback signal into a digital signal. The CPU (central processing unit for digital microcomputer) 8 includes a RAM 9 for storing setting values, a ROM 10 for storing programs,
Built-in arithmetic unit 11, etc., and transfers the calculation results to buffer 12
It is output to the function generator 13 via. The function generator 13 generates a periodic function of an analog signal according to a control signal from the CPU 8.

As shown in Fig. 3, the CPU 8 reads the signal values input from the A/D converter moment by moment, calculates the actual average value of the periodic function actually acting on the sample W, and calculates the actual average value. Compare the set average values stored in RAM9, and if there is no deviation as a result of the comparison, repeat the above steps, and if there is a deviation, set the target value by an amount commensurate with the deviation. and outputs the changed target value to the function generator 13 via the buffer 12.

As a result, even if the analog circuit constants set before the start of the test are not optimal, the average value of the load actually acting on the sample W at the beginning of the test is
The target value itself is immediately corrected to be equal to the average value set in RAM 9, and from then on, only if there is a change in sample compliance or drift in the analog circuit system during the test, the target value is adjusted to cancel out these changes. is corrected, and a load having an average value equal to the set value in the RAM 9 is always applied to the sample W from the beginning of the test to the end.

(f) Effects According to the present invention, the feedback signal of the measured value regarding the displacement of the sample due to the drive of the load device is digitally converted in the feedback system, and the actual average value of the above-mentioned measured value is calculated using the digitally converted data. Then, the deviation between the actual average value and the set average value is calculated by digital calculation, and the average value of the output waveform (target value signal) of the function generator is changed based on the result, so the constant settings of the analog circuit system etc. Even if there are some errors, it is possible to perform accurate tests according to the set values stably over a long period of time by correcting them, and in particular, it is possible to eliminate deviations caused by analog circuit drift, which was virtually impossible to eliminate with conventional equipment. There will be none.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example. Second
The figure is a block diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart of the control program of the CPU shown in FIG. 2...Sensor, 3...Sensor amplifier, 4...Comparator, 5...Servo amplifier, 6...Load device, 7
...A/D converter, 8...CPU, 9...RAM,
10... ROM, 11... Arithmetic unit, 12... Interface, 13... Function signal generator.

Claims (1)

[Claims] 1 In a device that outputs a predetermined periodic function as an analog signal, receives feedback of the measured value regarding the displacement of the sample to be tested by the load device, and controls the drive of the load device based on the deviation from the periodic function. A function generator that can change the average value of the analog periodic function wave to be applied, an A/D converter that converts the analog signal to be fed back into a digital signal, and a memory that stores the average value of the periodic function of the physical quantity to be applied to the sample. means for calculating the actual average value of the output of the A/D converter, means for determining the deviation of the actual average value from the value stored in the digital storage means, and the magnitude of the deviation. A control device for a material testing machine, characterized in that a control device for a material testing machine is provided, comprising means for giving a command to the function generator to cancel the deviation according to the deviation.