JP4390071B2 - Material testing machine - Google Patents

Description

  The present invention relates to a material testing machine, and more particularly to a material testing machine using a motor as a drive source of a load mechanism.

  In a material testing machine, in general, a load is applied to a test piece by driving the load mechanism, and a test force acting on the test piece is detected by the load cell, or position information of the load mechanism is detected momentarily. Using this detection result, selective feedback control is performed based on any of test force control, load speed control, and load mechanism displacement control.

  As a load mechanism in such a material testing machine, two screw rods are rotatably provided on a table, and both ends of the crosshead are supported on each screw rod via nuts, and each screw rod is supported by a motor. It is known that the crosshead is made to approach / separate from the table by being rotated by the rotation of the load cell, and the load mechanism is controlled by the output of the load cell that detects the test force acting on the test piece, This is performed by feeding back the position information selected as the control amount to the target value set in advance. This feedback control is digitally performed by a control device mainly composed of a CPU (see, for example, Patent Document 1).

  As a specific configuration for controlling the motor of the load mechanism by such a control device mainly composed of a CPU, an example in which the motor speed control (load mechanism displacement control) is performed is shown in FIGS. 5 and 6, respectively. What is shown in a block diagram is known.

  The example shown in FIG. 5 is an example using a pulse drive type motor driver 52, and the drive pulse is supplied from the CPU 51. The motor driver 52 supplies a control current to the motor 53 for driving the load mechanism according to the number of pulses. The encoder 54 generates a pulse signal corresponding to the number of rotations of the motor 53. The pulse signal is fed back to the motor driver 52 and simultaneously counted by the counter 55. The counting result (movement count value) is taken into the CPU 51. . The CPU 51 sequentially compares the momentary movement count value with a preset target value, and sequentially calculates the rate of the drive pulse to be supplied to the motor driver 52 in accordance with the deviation between the two.

  The example shown in FIG. 6 is an example using a motor driver 62 that operates in accordance with an analog signal. The operation signal is given by converting a digital signal supplied from the CPU 61 into an analog form by a DA converter 63. The motor driver 62 supplies a control current corresponding to the analog signal to the motor 64. The encoder 65 generates a pulse signal corresponding to the rotational speed of the motor 64. The pulse signal is fed back to the motor driver 62 in the same manner as described above, and simultaneously counted by the counter 66. The counting result (movement count value) is It is taken into the CPU 61. The CPU 61 sequentially compares the movement count value with the target value set in advance, and sequentially determines the magnitude of the signal to be supplied to the motor driver 62 via the DA converter 63 according to the deviation between the two. calculate. Note that this type of motor driver 62 includes one that generates torque proportional to the analog voltage, and one that rotates the motor 64 based on a rotational angular velocity proportional to the analog voltage.

When the load mechanism is subjected to load (test force) control, the detection output from the load cell is amplified and digitized by an A / D converter, and the measured data is sequentially compared with a target value in the CPU, whereby the motor driver The pulse rate or digital value to be supplied to 52 or 62 is calculated.
JP 2002-357521 A

  By the way, according to the conventional control of the load mechanism motor using the CPU as described above, the CPU generates pulses to be supplied to the motor driver while checking the movement count value every moment, or the motor through the DA converter. There is a problem that it is necessary to calculate the magnitude of a signal supplied to the driver, which increases the load on the CPU.

  In general, the CPU performs not only the above-described control but also data processing and display control processing. If a long time is required for such processing, processing for controlling the motor is not performed. For example, the motor may not be stopped or the speed may not be changed at the moment when the movement count value reaches a specified value. For example, even if it is set to perform a process for controlling the motor by an interrupt, since several clocks are required for the interrupt, it cannot be fundamentally improved.

  An object of the present invention is to provide a material testing machine capable of solving the above-described problems and improving the control performance as compared with the conventional one.

In order to solve the above problems, the material testing machine of the present invention detects a load mechanism using a motor as a drive source and a test force acting on the test piece when a load is applied to the test piece by driving the load mechanism. Force detection means for detecting the position of the load mechanism, and position information detection means for detecting information on the position of the load mechanism, wherein the motor is selectively controlled based on any one of test force control, load speed control, and load mechanism displacement control. In a material testing machine that performs feedback control, information relating to the operation pattern of the motor is obtained from the CPU for controlling the testing machine, and the information relating to the operation pattern and the rotation phase of the motor are associated with the CPU. FPGA which by comparison with the count value output from the encoder that outputs a pulse for controlling the driver of the motor, with one of the PLD or DSP, the C With U is configured not involved in direct control of the motor during the test, this CPU is configured to count the output from the encoder from the FPGA, PLD, or DSP is supplied It is characterized by having.

  The present invention intends to solve the problem by using a programmable logic such as FPGA, PLD, or DSP, and sharing the control of the material testing machine by this and the CPU. For example, the CPU transfers various parameters for controlling the testing machine to the FPGA, PLD, and DSP before starting the test, and is necessary for control such as sine wave control, trapezoid control, constant speed control, acceleration control, and test force control. Complicated measurement is not performed by the CPU, but by FPGA, PLD, and DSP. In this way, the CPU can control the motor only by giving a simple command regardless of the motor control directly during the test.

  That is, in the present invention, the CPU for controlling the material testing machine takes in the detection values such as the momentary test force and the displacement of the load mechanism (rotational speed of the motor) and the pulse rate for driving the motor described above. The digital value or the like is not calculated every moment for motor control, but this is assigned to the FPGA, PLD, or DSP. In particular, the FPGA can be operated at several tens of MHz or more, and since logic can be created only to control the motor, it can cope with high-speed rotation of the motor. The CPU only supplies the operation pattern to the FPGA, PLD, or DSP with respect to the motor control, and performs other processing during the test. This makes it possible to execute motor control and other processing in parallel, reducing the burden on the CPU and eliminating the possibility of delaying motor control.

  According to the present invention, in addition to the CPU for controlling the material testing machine, logic that can be arbitrarily created in advance, such as FPGA, PLD, or DSP, is provided, and the logic for controlling the motor for driving the load mechanism during the test is provided. Since the CPU is configured to perform other processing only by supplying the operation pattern of the motor to the logic, it took time for the CPU to perform other processing while the load mechanism was being driven. As a result, the control performance of the material testing machine can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and is a diagram showing a schematic diagram showing a mechanical configuration and a block diagram showing a system configuration. FIG. It is a block diagram showing.

  The testing machine main body 1 has a structure in which two screw rods 12a and 12b are rotatably arranged on a table 11, and both end portions of the crosshead 1 are supported by nuts 13 and 13b on the screw rods 12a and 12b. The screw rods 12a and 12b are rotated by a driving device 14 including a motor 14a and a transmission mechanism 14b, and thereby the cross head 13 moves so as to approach / separate from the table 11.

  The testing machine main body 1 in FIG. 1 is set to perform a tensile test, and is attached to the table 11 and the cross head 13 so that the gripping tools 15a and 15b are opposed to each other, and the gripping tools 15a and 15b are tested. A tensile load is applied to the test piece W by raising the crosshead 13 while holding both ends of the piece W.

  The test force acting on the test piece W is detected by the load cell 15 interposed between the crosshead 13 and the upper gripping tool 15b, and the elongation of the test piece W is measured by an extensometer 17 attached to the test piece W. Detected by. Furthermore, an encoder 18 is attached to the motor 14a, and the encoder 18 detects the rotational phase of the motor 14a every moment. Each of these detection outputs is taken into the control device 2.

  As shown in FIG. 2, the control device 2 includes a CPU 21 and peripheral devices (not shown) such as a ROM and a RAM, a pulse drive type motor driver 23 that drives and controls the FPGA 22 and the motor 14a, and an AD converter 24. , And amplifiers 25a and 25b for amplifying the outputs of the load cell 16 and extensometer 17, respectively. The example of FIG. 2 shows an example of a signal flow when speed control or position control of the load mechanism (crosshead 13) is performed. At the same time as the output of the encoder 18 is fed back to the motor driver 23, It is taken into the FPGA 22. The outputs of the load cell 16 and extensometer 17 are amplified by the amplifiers 25a and 25b, digitized by the A / D converter 24, and then taken into the CPU 21.

  The CPU 21 calculates the operation pattern of the motor 14a based on these when the control amount and the target value are set before the test is started, and writes them in the FPGA 22. In the FPGA 22, the operation pattern, for example, the operation pattern for position control such as constant speed control of the load mechanism or sine wave control, and the pulse output from the encoder 18 are counted and the count value is sequentially compared, and the operation is performed. A pulse having a rate corresponding to the deviation between the two is generated so that the operation of the motor 14 a follows the pattern, and is supplied to the motor driver 23. The motor driver 23 supplies a control current corresponding to the pulse to the motor 14a. Further, the FPGA 22 supplies the CPU 21 with the pulse count value (movement count value) from the encoder 18.

  On the other hand, the CPU 21 does not participate in the control of the motor 14a during the test, and the test force measurement data by the load cell 16 taken in via the amplifier 25a and the AD converter 24, the amplifier 25b and the AD converter. The extension measurement data from the acquired extensometer and the movement count value from the FPGA 22 are acquired, and for example, a load-elongation curve is created by data processing using these, and display control of a display (not shown) is performed. .

  According to the above embodiment, the CPU 21 executes data processing and display control processing regardless of the control of the motor 14a, and the control of the motor 14a is performed by the FPGA 22, and the burden on the CPU 21 can be reduced. At the same time, the control performance of the material testing machine can be improved without causing problems such as a delay in the control of the motor 14a due to processing other than the motor control of the CPU 21.

  Here, although the example using the pulse drive type motor driver 23 is shown in the above embodiment, the present invention can also be applied to a motor driver operated by an analog signal, and an example thereof is shown in FIG. The motor driver 27 in this example is of a type that operates based on an input analog signal, and the magnitude of the analog signal is obtained by counting the pulse signal from the encoder 18 in the FPGA 22 and sequentially comparing the count value with the operation pattern. A signal obtained by converting the digital value based on the calculation result into an analog signal by the DA converter 26 is supplied to the motor driver 27.

  Further, in the above embodiment, the case where the motor 14a is driven and controlled under the load speed or the position control of the load mechanism has been described, but it can also be used for test force control. FIG. 4 is a block diagram showing the signal flow in that case. This example is an example in the case where a pulse drive type motor driver 23 equivalent to that shown in FIG. 2 is used. The FPGA 22 amplifies the output of the load cell 16 by an amplifier 25a and then an A / D converter 24. Digitized test force data is captured every moment. The FPGA 22 sequentially calculates and outputs the rate of pulses to be supplied to the motor driver 23 so that the test force data matches the operation pattern supplied from the CPU 21 in advance. Of course, even when a motor driver that operates by analog signals is used, the test force control can be performed by adopting the configuration according to FIG.

  Even in the test force control as described above, the burden on the CPU 21 is reduced as in each of the previous examples, and at the same time, it is possible to eliminate problems such as delays in the control of the motor 14a due to other processes.

  Here, in each of the above embodiments, the FPGA is used as the logic for controlling the driving of the motor driver by supplying the operation pattern from the CPU. However, the same effect can be obtained by using a PLD or a DSP instead. There is an effect.

  In each of the above embodiments, an example in which the present invention is applied to a material testing machine set to perform a tensile test has been shown. However, the present invention is equally applied to other tests such as a compression test and a fatigue test. It goes without saying that it can be applied.

It is a block diagram of embodiment of this invention, and is the figure which writes together and shows the schematic diagram showing a mechanical structure, and the block diagram showing an electric structure. It is a block diagram which shows the principal part structure of the control apparatus 2 in embodiment of FIG. It is a block diagram which shows the principal part structure of the control apparatus in other embodiment of this invention. It is a block diagram which shows the principal part structure of the control apparatus in further another embodiment of this invention. It is a block diagram which shows the structural example of the conventional control apparatus which controls the motor of a load mechanism by CPU. It is a block diagram which shows the other structural example of the conventional control apparatus which controls the motor of a load mechanism by CPU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test machine main body 11 Table 12a, 12b Screw rod 13 Cross head 14 Drive device 14a Motor 14b Transmission mechanism 15a, 15b Grasping tool 16 Load cell 17 Extensometer 18 Encoder 2 Control device 21 CPU
22 FPGA
23, 26 Motor driver 24 A-D converter 25a, 25b Amplifier 17 D-A converter W Test piece

Claims (1)

A load mechanism using a motor as a drive source, force detection means for detecting a test force acting on the test piece when a load is applied to the test piece by driving the load mechanism, and detecting information relating to the position of the load mechanism In a material testing machine that includes position information detection means that selectively controls feedback of the motor based on any of test force control, load speed control, or load mechanism displacement control,
The CPU for controlling the test machine and the information related to the operation pattern of the motor are obtained from the CPU, and the output from the encoder that outputs the information corresponding to the operation pattern and the pulse corresponding to the rotation phase of the motor. FPGA which controls the driver of the motor by comparing the count value with one of the PLD or DSP, along with the CPU is configured to not involved in direct control of the motor during the test, the CPU Is configured to be supplied with the count value of the output of the encoder from the FPGA, PLD or DSP .

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