JPH0564730B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Field of Industrial Application The present invention relates to a load speed control device for a material testing machine that uses an electric motor as a drive source and performs tensile tests, compression tests, repeated fatigue tests, etc. of materials. (b) Prior art When an electric motor is used as the load-loading power source of a material testing machine, the variable range of the load speed has conventionally been approximately 1 to 1/2 when the load mechanism has a variable speed reduction device.
100,000, approximately 1 to 1 unless a variable speed reduction device is used
It is about 1/1000. By the way, when a wide range of loading speeds from high speed to extremely low speed is required in tensile, compression or cyclic fatigue testing of materials, the speed control range does not satisfy the requirements with conventional equipment that does not use a variable reducer. When a variable speed reducer is used, there is a backlash of gears, etc., which has a negative effect on the test and makes it impossible to obtain accurate test results. (c) Purpose The purpose of the present invention is to control the load speed over a wide range from high speed to extremely low speed without using a variable speed reduction device in the load mechanism, without any adjustment or setting by the operator. This can be done automatically depending on the condition, material, etc., and the waveform of the target value signal.
An object of the present invention is to provide a load speed control device for a material testing machine that uses an electric motor as a load drive source. (d) Configuration The present invention is characterized by using a DC servo motor as the drive source of the load mechanism, and by feeding back the load detection value signal to the load target value signal to generate a frequency proportional to the absolute value of the error signal. A voltage-frequency conversion circuit that generates a pulse signal, a variable frequency divider that receives the output of the voltage-frequency conversion circuit, and a variable frequency divider that discriminates the magnitude of the absolute value of the error signal into multiple preset ranks. , a rank discrimination circuit that outputs a signal according to the discrimination result, a polarity discrimination circuit that discriminates the polarity of the error signal, a variable frequency divider output and a polarity discrimination circuit output, and a DC servo motor. It is equipped with a motor drive circuit that rotates the motor at a rotation speed corresponding to the frequency of the motor in a direction corresponding to the polarity discrimination result, and is configured to automatically change the frequency division ratio of the variable frequency divider based on the output of the rank discrimination circuit. be. (e) Examples Examples of the present invention will be described below based on the drawings. FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing the detailed configuration of the automatic variable frequency divider. Further, FIG. 3 shows an example of the configuration of a mechanical load mechanism L of a material testing machine controlled according to an embodiment of the present invention. In Fig. 3, reference numeral 1 is a DC servo motor whose power is supplied by a pulley 2, a belt 3, a pulley 4, a worm 5, a worm wheel 6, and a ball screw 7.
The signal is transmitted to the test piece W via the . Note that 8 is a load cell. Now, in FIG. 1, the setting device 10 is the test piece W.
This is for generating a target value signal for the load to be applied to the load, and can output a voltage signal such as a ramp wave as shown in FIGS. 4a and 4b, or a repetitive triangular wave as shown in FIG. The load acting on the test piece W is detected by the load cell 8 and load amplifier 11, and the detected value signal is fed back to the target value signal. The error signal generated in this feedback is amplified by an amplifier 12, and then converted into a positive DC voltage signal by an absolute value circuit 13 regardless of its polarity, and is input to a Vf converter 14. At the same time, the polarity of the error signal is determined by the polarity determining circuit 15. The V-f converter 14 generates a pulse signal with a frequency proportional to the voltage of the input signal.
It is possible to generate pulse signals with frequencies in the range of 10,000). The output pulse signal of the Vf converter 14 serves as an input signal to an automatic variable frequency divider 16, which will be described later. Further, the output signal of the absolute value circuit 13 is provided as a signal for controlling the frequency division ratio of the automatic variable frequency divider 16. The output pulse signal of the automatic variable frequency divider 16 and the output signal of the polarity discrimination circuit 15 are connected to the DC servo motor 1.
is supplied to the drive circuit 17 of. The drive circuit 17 is
Using the output signal of the polarity determination circuit 15 as a forward/reverse rotation command signal, the DC servo motor 1 can be driven to rotate at a rotation speed proportional to the input pulse frequency, for example, by using the f-V converter 17a and the servo amplifier 17b. Can be configured. The automatic variable frequency divider 16, as shown in FIG.
Using the output pulse signal of the converter 14 as an input signal, multipliers 21, 22, 23 capable of dividing the frequency from 1 to 1/10 and a multiplier 24 capable of dividing the frequency from 1 to 1/2 are connected in cascade. It consists of a variable frequency divider section, an amplifier 25, a rank discrimination circuit 26, and a logic circuit 27, and inputs the analog output signal of the absolute value circuit 13 to generate a frequency division ratio control signal to each multiplier. It is equipped with a control section. The rank discrimination circuit 26 has first to fourteenth output terminals, discriminates the magnitude of the output of the absolute value circuit 13 that has passed through the amplifier 25 into 14 preset ranks, and corresponds to the discrimination result. Only the output of the input terminal is set to H level. The logic circuit 27 receives the discrimination signal from the rank discrimination circuit 26 and operates each multiplier 21, 22, 23 in response to the signal.
and 24 supply control signals to frequency division ratio control input terminals A, B, C, D, and CL of each multiplier so that the frequency division ratios shown in Table 1 are adopted. In Table 1, R is the magnitude (unit: volt) of the input signal to the rank discrimination circuit 26, and H is the terminal number of the first to fourteenth terminal outputs of the rank discrimination circuit 26 at H level. are the frequency division ratios of the multipliers 21, 22, 23, and 24, respectively, and T is the total frequency division ratio.

[Table] As mentioned above, the V-f converter 14 corresponds to the magnitude of the input signal from the absolute value circuit 13.
Since a pulse signal with a frequency in the range of 50 kHz to 5 Hz is output, the output voltage E of the absolute value circuit 13 is
(mV) and the frequency f' (Hz) of the output pulse of the automatic variable frequency divider 16, for example, when the gain of the amplifier 25 is x100, as shown in Table 2. In the table, f (Hz) is the output frequency of the Vf converter 14. As described above, depending on the output voltage of the absolute value circuit 13, the automatic variable frequency divider 16 operates from 50kHz to 1/400Hz.
In other words, a pulse signal with a frequency in the range of 1 to 1/20000000 is output. Therefore, the rotation speed of the DC servo motor 1 is automatically controlled in the range of 1 to 1/20000000 depending on the magnitude of the error signal, and the DC servo motor 1 is used as the drive source. The load mechanism L is 1 to 1/
It is possible to control the load speed in the range of 20,000,000.

【table】

[Table] In the above embodiment, the rank determined by the rank discrimination circuit 26 is set to 14, and four multipliers are used to set the frequency division ratio in the range of 1 to 1/2000. The frequency division ratio range can be arbitrarily set by changing the number of ranks, changing the number of ranks of the rank discrimination circuit accordingly, and appropriately assembling logic circuits. In addition, in the above embodiments, an example was shown in which the controlled variable was used as a load, but other physics, such as swing width or elongation, may also be used as the controlled variable, using a swing width detector or an extensometer instead of the load cell 8. Of course, by installing the same speed control, it is possible to perform the same speed control. (f) Effects As explained above, according to the present invention, a pulse signal proportional to the magnitude of an error signal obtained by feeding back a detected value signal to a target value signal is generated, and the pulse signal is further converted into an error signal. It is configured to automatically divide the frequency at an appropriate frequency division ratio according to the size of the signal, and drive the DC servo motor, which is the drive source of the load mechanism, at a rotation speed proportional to the frequency of the divided pulse signal. Therefore, the variable speed range of the DC servo motor can be significantly expanded, for example from 1 to 1/2 without using a variable speed reducer in the load mechanism.
Load speed control over a wide range of 20,000,000 can be achieved. Furthermore, since the frequency division ratio is automatically set according to the magnitude of the error signal, it can be adjusted to suit the condition and material of the test object or the form of the target value signal, without requiring judgment or adjustment by the operator. Load speeds from high to extremely low can be automatically obtained. Being able to control the loading speed in the range of 1 to 1/20000000 means that the tensile (or compressive) loading speed of the test piece can be controlled, for example, from 350 mm/min to 0.00002
It can be controlled over a wide range of mm/min, and the repetition frequency of cyclic fatigue tests is approximately
This means that control can be performed at 2.5 Hz to 3×10 ^-8 Hz, which satisfies the requirements for a material testing machine. In addition, since a mechanical transmission device such as a variable speed reducer is not required, accurate data can always be obtained especially in repeated fatigue tests without being affected by backlash, which is highly effective.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the overall configuration of an embodiment of the present invention, Figure 2 is a block diagram showing the configuration of its automatic variable frequency divider, and Figure 3 is a load of a material testing machine controlled by the embodiment of the present invention. FIGS. 4a, 4b, and 4c are graphs showing examples of output waveforms of the setting device 10, respectively. 1...DC servo motor, 5...Worm, 6
...Worm wheel, 7...Ball screw, 8...
... Load cell, 10 ... Setting device, 13 ... Absolute value circuit, 14 ... V-f converter, 15 ... Polarity discrimination circuit, 16 ... Automatic variable frequency divider, 17 ... Drive circuit, 21, 22, 23, 24... Multiplier, 26... Rank discrimination circuit, 27... Logic circuit.

Claims (1)

[Claims] 1 It has a load mechanism using a DC servo motor as a drive source, and the load mechanism is controlled by feeding back the detection value signal of the physical quantity acting on the test object to the target value signal of the physical quantity to be applied to the test object. A voltage-frequency conversion circuit that is a control device for a material testing machine that performs drive control, and that generates a pulse signal with a frequency proportional to the absolute value of an error signal obtained by feeding back the detected value signal to the target value signal; A variable frequency divider that receives the output of the voltage-frequency conversion circuit as an input, and a rank that discriminates the magnitude of the absolute value of the error signal into a plurality of preset ranks and outputs a signal according to the discrimination result. A discrimination circuit, a polarity discrimination circuit that discriminates the polarity of the error signal, the output of the variable frequency divider, and the output of the polarity discrimination circuit are input, and the DC servo motor is driven at a rotation speed according to the frequency of the input pulse signal. and a motor drive circuit that rotates the motor in a direction according to the polarity determination result, and is configured to automatically change the frequency division ratio of the variable frequency divider based on the output of the rank discrimination circuit. Load speed control device for material testing machine.