Controller, material testing machine, and material testing system

Abstract

To provide a controller that can efficiently perform a material test using a preferred PID coefficient.SOLUTION: A controller that controls an operation of a material testing machine performing a material test for an analyte comprises a PID control part that performs PID control for the material testing machine. The PID control part calculates the optimum value of a PID coefficient of the material testing machine during the operation of the material testing machine, then selects and executes one of a plurality of operation modes including a first mode in which the material testing machine in the operation is PID-controlled using the calculated optimum value and a second mode in which the operation of the material testing machine is PID-controlled using a value of a specified PID coefficient.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a controller, a materials testing machine, and a materials testing system. [Background technology]

[0002] Material testing machines are widely used for performing material tests (specifically, for example, tensile tests, compression tests, etc.) to examine the mechanical properties of materials. It is also known that in material testing machines, PID control is performed to suitably control the output of a drive unit for performing tension or compression. For example, Patent Document 1 discloses optimizing the PID coefficients used in PID control based on measurements during material testing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-222206 Summary of the Invention [Problem to be solved by the invention]

[0004] In material testing using a material testing machine, it is necessary to appropriately determine the PID coefficients. An object of the present invention is to provide a controller, a material testing machine, and a material testing system that can efficiently perform material testing using suitable PID coefficients. [Means for solving the problem]

[0005] According to a first aspect of the present invention, there is provided a controller for controlling an operation of a materials testing machine that performs a materials test on a test specimen, comprising: A PID control unit that performs PID control on the material testing machine, The PID control unit is a first mode in which optimal values ​​of PID coefficients of the material testing machine are calculated during operation of the material testing machine, and the operation of the material testing machine during operation is PID-controlled using the calculated optimal values; a second mode in which the operation of the materials testing machine is PID controlled using specified PID coefficient values; A controller is provided for selecting and executing one of a number of operating modes, including

[0006] According to a second aspect of the present invention, there is provided a controller for controlling an operation of a materials testing machine that performs a materials test on a test specimen, comprising: A PID control unit that performs PID control on the material testing machine, The PID control unit is Initiating PID control of the operation of the materials testing machine using the specified PID coefficient values; If a predetermined condition is satisfied while the PID control is being performed with the specified PID coefficient value, an optimal value of the PID coefficient of the material testing machine is calculated; A controller is provided which, upon calculating the optimum values, thereafter performs PID control of the operation of the materials testing machine using the calculated optimum values ​​as the PID coefficients.

[0007] According to a third aspect of the present invention, there is provided a control device comprising: a receiving unit that receives a control instruction related to the PID control from the controller according to the first or second aspect; and a drive unit that performs an operation for the material test based on the control instruction.

[0008] According to a fourth aspect of the present invention, there is provided a controller according to the first or second aspect, There is provided a materials testing system comprising: a materials testing machine of the third aspect. Effect of the Invention

[0009] According to the controller, material testing machine, and material testing system of the present invention, it is possible to efficiently perform material testing using suitable PID coefficients. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing the configuration of a material testing system according to the first and second embodiments. [Diagram 2] FIG. 2 is a flow chart showing the steps of the load rate maintenance test of the first embodiment. [Diagram 3] FIG. 3 is a flowchart of the coefficient calculation process. [Figure 4] FIG. 4 is a schematic graph showing an example of a load-deformation diagram obtained by a material test. [Diagram 5] FIG. 5 is a flow chart showing the steps of the creep test. [Figure 6] FIG. 6 is a schematic diagram showing an example of the layout of the setting screen. [Figure 7] FIG. 7 is a schematic diagram showing an example of a setting screen when the load rate maintenance test is selected. [Figure 8] 8(a) and 8(b) are schematic diagrams showing an example of a setting screen and input contents when a creep test is performed by the material testing machine. [Figure 9] FIG. 9 is a flow chart showing the steps of the load rate maintenance test of the second embodiment. [Figure 10] FIG. 10 is a flow chart showing the steps of the intermediate mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First Embodiment [Materials testing] The material testing system 100 according to this embodiment is a system for conducting material tests. Examples of "material tests" include tensile tests, compression tests, bending tests, torsion tests, relaxation tests, and creep tests.

[0012] The material testing system 100 of this embodiment is configured to be capable of performing tests in which a load is applied to a test piece at a predetermined rate, such as tensile tests and compression tests (hereinafter, these are collectively referred to as load rate maintenance tests), and creep tests. However, the types of tests that the material testing system 100 can perform are not limited to these. In addition, the material testing system 100 may be configured to be capable of performing only either the load rate maintenance test or the creep test.

[0013] [Load rate maintenance test and creep test] The load rate maintenance test is a test in which a load is applied to a test specimen (hereinafter referred to as "test specimen load") at a predetermined load rate until the load reaches a target load. In the present disclosure, as an example, the target load is LT [N] and the load rate is LV [N / s]. The load rate LV [N / s] means the increase in the test specimen load per second. That is, in the load rate maintenance test, the test specimen load is increased at a predetermined pace until the test specimen load reaches the target load LT [N]. The load rate maintenance test is performed, for example, when investigating the magnitude of the load that may cause damage to the test specimen (specimen).

[0014] A creep test is a test in which a test specimen is subjected to a load for a predetermined duration while maintaining the load at a target load (e.g., LT [N]). In the present disclosure, the duration is set to D [s] as an example. That is, in a creep test, a constant target load LT [N] is continuously applied to the test specimen for the duration D [s]. A creep test is performed, for example, when investigating the durability of a test specimen (specimen).

[0015] [PID control] The material testing system according to the present disclosure is configured to be capable of performing PID (Proportional-Integral-Differential) control. PID control is a type of feedback control, and a proportionality coefficient K P Proportional control (P control) using integral coefficient K I Integral control (I control) using the differential coefficient K DIn this specification, the PID coefficient is a combination of a proportional coefficient K P , integral coefficient K I , and the differential coefficient K D In this embodiment, for example, the control target of the PID control is the motor 15, and the control amount is the test piece load.

[0016] In the load rate maintenance test, the PID control is performed to maintain the load rate LV [N / s] at a preset rate. Since the behavior of the test piece changes due to the deformation of the test piece in response to tension or compression during the test, it is difficult to maintain the load rate LV [N / s] at the same rate by simply increasing the output of the motor 15 at a predetermined pace. In this regard, by performing the PID control, it becomes easy to maintain the load rate LV [N / s] at a preset rate.

[0017] In a creep test, PID control is performed to keep the test piece load at the target load LT [N]. Since the behavior of the test piece changes due to deformation of the test piece in response to tension or compression during the test, it is difficult to keep the test piece load constant by simply keeping the output of the motor 15 constant. In this regard, by performing PID control, it becomes easier to keep the test piece load constant.

[0018] [Configuration of material testing system 100] A material testing system 100 according to a first embodiment of the present invention will be described with reference to Figures 1 to 5. As shown in Figure 1, the material testing system 100 mainly comprises a material testing machine 10, a control device (controller) 20, and an input device 30.

[0019] [Materials testing machine 10] The material testing machine 10 is a device that actually performs testing. The material testing machine 10 mainly includes a base 11, a pair of ball screws 12 extending upward from the base 11, a crosshead 13 movable along the pair of ball screws 12, a load cell 14 attached to the crosshead 13, and a motor (drive unit) 15 provided inside the base 11. A table 11a is provided on the upper surface of the base 11.

[0020] [Control device 20] The control device 20 is a device for comprehensively controlling the material testing machine 10. The control device 20 mainly includes an interface 21, a communication unit 22, a PID control unit 23, and a storage unit 24.

[0021] The interface 21 is connected to the motor 15 of the material testing machine 10 by wiring. In this embodiment, the wiring extending from the interface 21 is connected to the receiving unit 15a. The communication unit 22 is connected to a communication unit 31 (described later) of the input device 30 by wiring. Note that the connection between the material testing machine 10 and the motor 15, and the connection between the communication unit 22 and the communication unit 31 may be made wirelessly.

[0022] The PID control unit 23 performs PID control of the operation of the material testing machine 10. The PID control unit 23 includes a mode selection unit 231 that determines an operation mode (described in detail below) of the control device 20, a control execution unit 232 that performs PID control of the motor 15 according to the determined operation mode, and an optimal value calculation unit 233 that calculates optimal values ​​of PID coefficients in a predetermined operation mode. The PID control of the material testing machine 10 by the PID control unit 23 will be described in detail later. The PID control unit 23 may temporarily store values ​​of PID coefficients (usage coefficients) used in the test.

[0023] The PID control unit 23 is realized by, for example, a CPU (Central Processing Unit) etc. In addition, various functional blocks included in the PID control unit 23 may be appropriately realized by the PID control unit 23 as a CPU reading and executing program data stored in the storage unit 24.

[0024] The storage unit 24 stores data necessary for the operation of the control device 20, data generated by the operation of the control device 20, and the like. The storage unit 24 may be, for example, a hard disk or a non-volatile memory. The storage unit 24 may store, for example, program data executable by a CPU (or GPU) serving as the PID control unit 23. The storage unit 24 may also store values ​​of PID coefficients (used coefficients) used in the test. The storage unit 24 may also store, for example, test condition information and / or test log data (hereinafter simply referred to as "log data"). Details of the test condition information and the log data will be described later.

[0025] [Input device 30] The input device 30 is a device for receiving input from a user, and mainly includes a communication unit 31, an input unit 32, a display unit 33, a storage unit , and a control unit .

[0026] As described above, the communication unit 31 is connected by wiring to the communication unit 22 of the control device 20. The input unit 32 is a user interface that allows a user of the material testing system 100 to input test condition information and the like. The input unit 32 may be, for example, a touch panel, a keyboard, a mouse, or the like.

[0027] The display unit 33 is a user interface that displays information to a user of the material testing system 100. The display unit 33 may be, for example, a display. The input device 30 may include an audio output unit in addition to or instead of the display unit 33. The audio output unit presents information to the user of the material testing system 100 by audio.

[0028] The storage unit 34 stores information (data) input to the input device 30. The storage unit 34 may be, for example, a hard disk or a non-volatile memory.

[0029] The control unit 35 is connected to the communication unit 31, the input unit 32, the display unit 33, and the storage unit 34. The control unit 35 controls the overall operation of the input device 30. The control unit 35 is realized by, for example, a CPU or the like.

[0030] The control unit 35 may display a test condition setting screen on the display unit 33. The control unit 35 may also set various test conditions in response to an input operation of the user received via the input unit 32, create test condition information that summarizes the set test conditions, and store the test condition information in the storage unit 34. The test condition setting screen will be described later.

[0031] [Control device operation mode] The control device 20 of the material testing system 100 operates in one of two operating modes during various material tests. The first mode is an "optimum value calculation mode." The optimum value calculation mode is a mode in which optimal values ​​of PID coefficients are calculated while the material testing machine 10 is in operation (e.g., during a test), and the material testing machine 10 is PID-controlled using the calculated optimal values. The second mode is a "specified value use mode." The specified value use mode is a mode in which the operation of the material testing machine 10 is PID-controlled using a pre-specified PID coefficient value.

[0032] The control device 20 of this embodiment determines in which of the above-mentioned two modes the device will operate, depending on the designation of the test condition information.

[0033] [Specific steps of load speed maintenance test] The specific steps of the load rate maintenance test will be described using a tensile test as an example.

[0034] A user of the material testing system 100 mounts attachments such as jigs and sensors appropriate for a desired test (here, a tensile test) on the material testing machine 10, and then sets a test piece in the material testing machine 10.

[0035] Specifically, when performing a tensile test, the user attaches chucks for gripping a test piece to each of the table 11a and the crosshead 13 of the material testing machine 10. The chucks are attached to the crosshead 13 via a load cell 14. Figure 1 shows the state in which an upper chuck CK1 is attached to the crosshead 13 and a lower chuck CK2 is attached to the table 11a.

[0036] Next, both ends of the test piece TP are gripped by the upper chuck CK1 and the lower chuck CK2. The test piece TP is prepared in the shape of, for example, a rod or a plate. In order to measure the displacement of the test piece TP, for example, an extensometer (not shown) may be attached to the test piece TP.

[0037] Before or after setting the attachments and test pieces, the user sets the operation of the material testing machine 10 for performing a tensile test via the input device 30. As will be described in detail later, the input device 30 creates information (test condition information) indicating the test conditions including the contents of the user's input, and transmits this to the control device 20. The control device 20 can perform a tensile test with the material testing machine 10 by controlling the material testing machine 10 (and the attachments) with reference to this test condition information. In other words, it can be said that the type of material test to be performed is determined by the combination of the above-mentioned attachments attached to the material testing machine 10 and the operating direction of the material testing machine 10. Note that the test condition information may be created in advance and stored in the control device 20.

[0038] In the load rate maintenance test, the control device 20 controls the material testing machine 10 according to the flowchart of FIG.

[0039] In step S101, the control device 20 acquires test condition information (information indicating test conditions). Specifically, the PID control unit 23 acquires the test condition information from the input device 30 via the communication unit 22. The test condition information may be information input to the input device 30 by a user of the material testing system 100 via the input unit 32 of the input device 30, or may be data read out from the memory unit 34 of the input device 30 or the memory unit 24 of the control device 20.

[0040] Specifically, the test condition information used in the load rate maintenance test includes, for example, the magnitude of the target load LT [N], and the load rate LV [N / s] required to reach the target load LT [N] (described in detail later). The information included in the test condition information varies depending on the material, shape, and dimensions of the test piece TP (test specimen), the purpose of the test, and the like. Note that the test condition information may specify the time T [s] required to reach the target load LT [N] instead of the load rate LV [N / s]. In this case, the load rate LV [N / s] can be calculated, for example, by the following formula (a). Calculation formula (a): (Target load [N] - Load at start of test [N]) / Time required [s]

[0041] When the mode indicated by the acquired test condition information is the "specified value use mode", the test condition information includes PID coefficients. For example, when the PID coefficients suitable for the test to be performed are known or the approximate suitable values ​​can be predicted based on empirical rules, it is possible to set the PID coefficients in advance. When the PID coefficients are included in the test condition information in this way, the PID coefficients may be manually input by the user, or values ​​measured in a previous test may be used. This also applies to the creep test described below.

[0042] In step S102, the control device 20 specifies whether the mode to be used in the current load speed maintenance test is the "specified value use mode" or the "optimum value calculation mode". This process is performed, for example, by the mode selection unit 231. In this embodiment, the mode selection unit 231 selects and executes the operation mode specified in the test condition information acquired in step S101. That is, in this embodiment, the test condition information includes information (type information) that specifies the operation mode of the control device 20 (and the material testing machine 10). In this embodiment, the mode selection unit 231 specifies whether the operation mode specified in the test condition information is the "specified value use mode" or the "optimum value calculation mode" by referring to the type information of the test condition information acquired in step S101.

[0043] For example, when the "specified value use mode" is specified by the test condition information (step S102: YES), the control execution unit 232 operates the control device 20 in the specified value use mode. That is, the control execution unit 232 sets the PID coefficient specified in the test condition information as the initial PID coefficient to be used in the load speed maintenance test (step S103). Note that, hereinafter, the PID coefficient used in various tests (i.e., the coefficient set as the PID coefficient to be used) is also referred to as the "used coefficient".

[0044] In the next step S104, the control execution unit 232 drives the motor 15 to apply a tensile load to the test piece TP. When the motor 15 is driven, the ball screw 12 rotates and the crosshead 13 moves upward. As a result, a tensile load is applied to the test piece TP held by the upper chuck CK1 fixed to the crosshead 13 and the lower chuck CK2 fixed to the table 11a. The load applied to the test piece TP (test piece load) is measured by the load cell 14. The displacement (test piece displacement) generated in the test piece TP is measured by an extensometer (not shown) attached to the test piece TP. In addition, the amount of movement of the crosshead 13 may be acquired and used as the test piece displacement.

[0045] In step S104, the control execution unit 232 applies a load to the test piece TP at a load speed LV [N / s] defined in the test condition information by PID-controlling the motor 15 using the set usage coefficient. After starting execution of step S104, the control execution unit 232 executes step S105 at a predetermined time interval. This time interval may be freely set by the user.

[0046] In the next step S105, the control execution unit 232 determines whether the test piece load has reached the target load LT [N]. If the control execution unit 232 determines that the test piece load has not reached the target load LT [N] (S105: NO), the control execution unit 232 continues step S104.

[0047] When the control execution unit 232 determines that the test piece load has reached the target load LT [N] (S105: YES), it causes the material testing machine 10 to end the load speed maintenance test.

[0048] In the load speed maintenance test of this embodiment, steps S103 to S105, which are executed using the PID coefficients included in the test condition information, correspond to the operation in the designated value use mode.

[0049] In step S102, the mode selection unit 231 identifies the type of PID control by referring to the type information included in the test condition information. For example, the mode selection unit 231 determines whether or not the "specified value use mode" is specified in the type information. If the "specified value use mode" is not specified (i.e., if the "optimum value calculation mode" is specified, step S102: NO), the mode selection unit 231 sets a predetermined initial PID coefficient as the first PID coefficient (i.e., the first use coefficient) to be used in the load speed maintenance test (step S106). The initial PID coefficient may be changeable by changing the internal setting of the control device 20. Note that if the test condition information does not include type information (i.e., if neither the "specified value use mode" nor the "optimum value calculation mode" is specified), the mode selection unit 231 may output an error.

[0050] Thereafter, the PID control unit 23 executes the load application step S107 and the coefficient calculation step S109 in parallel. In the load application step S107, the control execution unit 232 applies a tensile load to the test piece TP in the same manner as in step S104. Specifically, the control execution unit 232 applies a load to the test piece TP at a load speed LV [N / s] defined in the test condition information while performing PID control of the motor 15 using the value of the usage coefficient. The usage coefficient is an initial PID coefficient at the start of the load application step S107, and is updated to a newly calculated optimal value every time step S83 (described later) of the coefficient calculation step S109 is executed.

[0051] In the load application step S107, as in step S104, the load applied to the test piece TP (test piece load) is measured by the load cell 14, and the displacement (test piece displacement) generated in the test piece TP is measured by an extensometer or the like.

[0052] While continuing the control process shown in step S107, the control execution unit 232 executes the judgment process shown in step S108. That is, in step S108, the control execution unit 232 judges whether the test piece load has reached the target load LT [N]. The PID control unit 23 continues the load application process shown in step S107 until the control execution unit 232 judges that the test piece load has reached the target load LT [N] (S108: YES).

[0053] On the other hand, when it is determined that the test piece load has reached the target load LT [N] (S108: YES), the control execution unit 232 ends the load application step S107. In other words, the YES determination in step S108 is the end condition for the processing of step S107. From the start of execution of step S107 to the end of step S107, the control execution unit 232 executes the determination processing shown in step S108 at a predetermined time interval. This time interval may be freely set by the user.

[0054] The optimum value calculation unit 233 executes the coefficient calculation step S109 in parallel with the load application step S107. Fig. 3 is a flowchart of the coefficient calculation step S109 included in the load speed maintenance test. In the coefficient calculation step S109, the optimum value calculation unit 233 first obtains the test piece load and test piece displacement measured up to that point from the material testing machine 10 (Fig. 3, step S81).

[0055] In the next step S82, the optimum value calculation unit 233 calculates optimum values ​​of the PID coefficients based on the relationship between the test piece load and the test piece displacement obtained from the material testing machine 10. Fig. 4 is a schematic graph showing an example of a load-deformation diagram obtained by a material test. For example, it is assumed that the values ​​of the test piece load and the test piece displacement have been measured up to any of data points P0 to P(x+1) in Fig. 4. Each data point includes a pair of a value of the test piece load and a value of the test piece displacement.

[0056] In this case, the optimum value calculation unit 233 obtains a relational equation between the test piece load and the test piece displacement based on the values ​​of the measured data points (i.e., the test piece load and the test piece displacement). Then, it calculates the optimum value of the PID coefficient based on the value of the slope of the relational equation (in the case of the graph in FIG. 4, it can be expressed as the slope of a straight line extending along the data points involved in the calculation, as an example). Note that the "optimum value" means a value estimated to be optimal at the time of calculation. As described later, the "optimum value" can be updated to a new "optimum value" as the process progresses.

[0057] The PID coefficients are calculated using, for example, the partial model matching method. The partial model matching method is a design method that approaches the transfer function of a reference model (a known system with good properties). Known reference models include those that have no overshoot or oscillation and those that converge quickly.

[0058] Since the lower-order terms of the denominator series equation of the transfer function of the reference model affect the control, in the partial model matching method, each parameter is calculated so that the lower-order coefficients of the transfer function of the reference model match. In this embodiment, the first-order lag is "L" and the time constant is "T uv ", the reference model constant is "αi (i = 1, 2, 3, 4)", and the gain of the controlled object is K. Then, the proportional coefficient K P , integral coefficient K I , and the differential coefficient K D are obtained by the following formulas, respectively.

[0059]

number

number

number

[0060] Note that σ is expressed by the following equation 4.

number

[0061] In the next step S83, the PID control unit 23 sets the optimal value of the PID coefficient calculated in step S82 as the PID coefficient (usage coefficient) to be used in the load speed maintenance test. Here, "setting" may mean that the PID control unit 23 stores the usage coefficient as a temporary variable, or that the storage unit 24 stores the usage coefficient. That is, the usage coefficient is updated from the initial PID coefficient to the optimal value calculated in step S82. After step S83 is executed, in the load application step S107 executed in parallel, PID control is performed using the updated PID coefficient.

[0062] After executing the coefficient calculation step S109, in the following step S110, the optimum value calculation unit 233 judges whether the weight application step S107 has been completed. If the weight application step S107 is still being executed (S110: NO), the optimum value calculation unit 233 executes steps S81 to S83 again. If the weight application step S107 has been completed (S110: YES), the optimum value calculation unit 232 ends the loop of the series of processes of the coefficient calculation step S109. In this way, while the weight application step S107 continues, the optimum value calculation unit 233 repeats the acquisition of the measured value (step S81), the calculation of the optimum value (step S82), and the update of the used coefficient (step S83). Note that the series of processes of steps S109 to S110 are executed at a predetermined time interval. This time interval may be the same as the interval at which the process of step S108 is executed, or may be different.

[0063] When step S82 is repeatedly executed, the optimum value calculation unit 233 may calculate the optimum value of the PID coefficient using the values ​​of the test piece load and the test piece displacement measured in the load application step S107 up to that point.

[0064] For example, the optimum value calculation unit 233 calculates the slope based on a predetermined number of the most recent data points among the data points of the measurement results that the control device 20 has acquired since the start of the test. For example, in FIG. 4, it is assumed that after the value of the data point P(x) is acquired as a measurement result, the value of the data point P(x+1) is also acquired. In this case, the optimum value calculation unit 233 calculates the slope based on the values ​​of the most recent 10 data points including the data point P(x+1), that is, the values ​​of the data points P(x-8) to P(x+1). Note that the number of data points used to calculate the slope is arbitrary and is not limited to 10. Regardless of the number of data points used to calculate the slope, it is preferable to include the most recent data point in the data points used to calculate the slope.

[0065] By repeatedly executing step S109 (steps S81 to S83) in this way, the optimum value calculation unit 233 can perform the optimum value calculation of step S82, which is executed at a certain timing, based on more substantial (i.e., more) measurement data than the optimum value calculation of step S82 executed previously. Basically, it can be said that the load and the amount of displacement increase as the test progresses (i.e., the time elapses since the load started to be applied). In the example of FIG. 4, the plot position becomes farther from the data point P0 (origin) in the positive x-axis and positive y-axis directions of the graph as the test progresses. Therefore, the slope can be calculated using a data group in which the plots farther from the origin P0 increase as the test progresses. In other words, the optimum value calculation unit 233 can calculate the optimum value of the PID coefficient with higher accuracy by repeating step S109. Then, the control execution unit 232 can apply the calculated optimum value of the PID coefficient each time.

[0066] When the load application step S107 is completed and the coefficient calculation step S109 is also completed accordingly (i.e., the determination in step S110 is YES), the PID control unit 23 executes step S111. In step S111, the PID control unit 23 stores data associating the test condition information acquired in step S101 with the optimal value of the PID coefficient finally calculated in step S82 of the coefficient calculation step S109 as log data in the storage unit 24. Note that this log data may include the measurement results in S107. Also, step S111 is not essential.

[0067] The PID control unit 23 ends the load rate maintenance test after step S111 (after both steps S108 and S110 are completed if step S111 is not executed). Through the above steps, the result of the load rate maintenance test on the test piece TP (for example, a load deformation diagram of the test piece TP) is obtained.

[0068] In the load speed maintenance test of this embodiment, steps S106 to S111 correspond to the operation in the optimum value calculation mode.

[0069] To summarize the flow of the flowchart in FIG. 2, it can be said that the mode selection unit 231 selects whether to operate in the specified value use mode (i.e., execute steps S103 to S105) or to operate in the optimal value calculation mode (i.e., execute steps S106 to S11) depending on whether the answer is YES or NO in step S102.

[0070] [Specific steps of creep testing] Next, the specific steps of the creep test will be described. As in the case of the load rate maintenance test, the user of the material testing system 100 installs attachments such as jigs and sensors appropriate for the creep test on the material testing machine 10, and then sets the test piece in the material testing machine 10.

[0071] For example, in the creep test, similarly to the load rate maintenance test, the test piece TP may be held by the upper chuck CK1 and the lower chuck CK2, and an extensometer (not shown) or the like may be attached to the test piece TP.

[0072] Before or after setting the attachment and the test piece, the user sets the operation of the materials testing machine 10 for performing a creep test via the input device 30. The input device 30 creates test condition information including the contents of the user's input and transmits it to the control device 20. The control device 20 controls the materials testing machine 10 (and the attachment) by referring to the test condition information. Note that the test condition information may be created in advance and stored in the control device 20.

[0073] In the creep test, the control device 20 controls the material testing machine 10 according to the flowchart of FIG.

[0074] In step S201, the control device 20 acquires test condition information. Specifically, the PID control unit 23 acquires the test condition information from the input device 30 via the communication unit 22. As in the load rate maintenance test, in the creep test, the test condition information may be data manually input by the user, or may be data read out from the memory unit 34 of the input device 30 or the memory unit 24 of the control device 20.

[0075] Specifically, the test condition information used in the creep test includes, for example, type information, target load LT [N], duration D [s], etc. (described in detail later). The information included in the test condition information varies depending on the material, shape, dimensions, and purpose of the test of the test piece TP (subject). The test condition information may also include information indicating the type of test.

[0076] In step S202, the control device 20 selects the mode to be used in the creep test between the "optimum value calculation mode" and the "designated value use mode." This selection is performed, for example, by the mode selection unit 231. In this embodiment, the mode selection unit 231 selects and executes the operation mode specified in the type information included in the test condition information acquired in step S201. That is, in this embodiment, the test condition information includes type information. In this embodiment, the mode selection unit 231 identifies whether the specified operation mode is the "designated value use mode" or the "optimum value calculation mode" by referring to the type information included in the test condition information acquired in step S201.

[0077] The PID control unit 23 of the control device 20 executes PID control in either the "optimum value calculation mode" or the "designated value use mode" depending on the result of the determination in step S202. For example, if the "designated value use mode" is specified in the type information (S202: YES), the control device 20 operates in the designated value use mode. Specifically, the control device 20 executes steps S203 to S206. The specifics will be described below.

[0078] If the type information specifies the "specified value use mode" (S202: YES), the mode selection unit 231 sets the PID coefficient included in the test condition information or the initial value of a predetermined PID coefficient as the first PID coefficient to be used in the creep test (step S203).

[0079] In the next step S204, the control execution unit 232 drives the motor 15 to apply a tensile load to the test piece TP. The load applied to the test piece TP (test piece load) is measured by the load cell 14. The displacement (test piece displacement) generated in the test piece TP is measured by an extensometer (not shown) attached to the test piece TP. In addition, the movement amount of the crosshead 13 may be acquired and used as the test piece displacement. In step S204, the control execution unit 232 applies a load to the test piece TP at a constant speed V [mm / s] without performing PID control.

[0080] In the next step S205, the control execution unit 232 determines whether the test piece load has reached the target load LT [N]. If the control execution unit 232 determines that the test piece load has not reached the target load LT [N] (S205: NO), the control execution unit 232 continues step S204.

[0081] When the control execution unit 232 determines that the test piece load has reached the target load LT [N] (S205: YES), it continues to apply the target load LT [N] to the test piece TP for the duration D [s] (step S206). At this time, the control execution unit 232 performs PID control of the motor 15 using the set usage coefficient. When the duration D [s] has elapsed, the control execution unit 232 ends step S206, thereby ending the creep test. In the creep test of this embodiment, steps S203 to S206, which are executed using the PID coefficients included in the test condition information, correspond to operation in the designated value usage mode.

[0082] In step S202, the mode selection unit 231 identifies the operation mode by referring to the type information included in the test condition information. For example, the mode selection unit 231 determines whether or not the "specified value use mode" is specified in the type information. If the "specified value use mode" is not specified (i.e., if the "optimum value calculation mode" is specified, step S202: NO), the PID control unit 23 executes the load application step S207 and the coefficient calculation step S209 in parallel. The load application step S207 is the same process as step S204. That is, the control execution unit 232 applies a tensile load to the test piece TP at a constant speed V [mm / s]. At this time, the control execution unit S232 does not perform PID control. Note that if the type information does not include information specifying the operation mode (i.e., neither the "specified value use mode" nor the "optimum value calculation mode" is specified), the mode selection unit 231 may output an error.

[0083] In the load application step S207, as in step S204, the load applied to the test piece TP (test piece load) is measured by the load cell 14, and the displacement (test piece displacement) generated in the test piece TP is measured by, for example, an extensometer.

[0084] While continuing the control process shown in step S207, the control execution unit 232 executes the judgment process shown in step S208. That is, in step S208, the control execution unit 232 judges whether the test piece load has reached the target load LT [N]. The PID control unit 23 continues the load application process shown in step S207 until the control execution unit 232 judges that the test piece load has reached the target load LT [N] (S208: YES).

[0085] On the other hand, when it is determined that the test piece load has reached the target load LT [N] (S208: YES), the control execution unit 232 ends the load application step S207. In other words, the determination of YES in step S208 is the end condition for the processing of step S207. From the start of execution of step S207 to the end of step S207, the control execution unit 232 executes the determination processing shown in step S208 at a predetermined time interval. This time interval may be freely set by the user.

[0086] The coefficient calculation step S209 is the same process as the coefficient calculation step S109 shown in FIG. 2 and FIG. 3. That is, the optimum value calculation unit 233 acquires the test piece load and the test piece displacement, and calculates the optimum value of the PID coefficient from these values. The method of obtaining the optimum value of the PID coefficient is the same as that in the load rate maintenance test. Then, the PID control unit 23 sets the optimum value of the PID coefficient calculated by the optimum value calculation unit 233 as the PID coefficient (usage coefficient) to be used in the creep test. Here, "setting" may mean that the PID control unit 23 stores the usage coefficient as a temporary variable, or the storage unit 24 stores the usage coefficient. By continuously calculating and updating the PID coefficient in parallel with the load application step S207, when the test piece load reaches the target load LT [N] and creep control is started, the PID coefficient suitable for the material characteristics at that time can be set as the usage coefficient.

[0087] After the coefficient calculation step S209 is executed as described above, in the subsequent step S210, the optimum value calculation unit 233 judges whether the weight application step S207 has been completed. If the weight application step S207 is still being executed (S210: NO), the optimum value calculation unit 233 executes the coefficient calculation step S209 again. If the weight application step S207 is completed (S210: YES), the optimum value calculation unit 232 ends the coefficient calculation step S209. In this way, after the start of the weight application step S207, the optimum value calculation unit 233 repeats the acquisition of the measurement value, the calculation of the optimum value, and the storage of the coefficient used in parallel with the weight application step S207. Note that the series of processes from step S209 to step S210 are executed at a predetermined time interval. This time interval may be the same as the interval at which the process of step S208 is executed, or may be different.

[0088] If it is determined that the test piece load has reached the target load LT [N] (S208: YES), the control execution unit 232 continues to apply the target load LT [N] to the test piece TP for the duration D [s] (step S211). At this time, the control execution unit 232 performs PID control of the motor 15 using the set usage coefficient (i.e., the latest value of the PID coefficient set in the coefficient calculation step S209). The control execution unit 232 ends step S211 after the duration D [s] has elapsed.

[0089] After step S211, the PID control unit 23 associates the latest values ​​of the PID coefficients (i.e., the coefficients used) with the test condition information acquired in step S201, and stores them as new log data in the storage unit 24 (S212). Note that step S212 is not an essential step. After step S212 (after step S211 if S212 is not executed), the PID control unit 23 causes the material testing machine 10 to end the creep test.

[0090] In the creep test of this embodiment, the steps from step S207 to step S212 correspond to operation in the optimum value calculation mode. To summarize the flow of the flowchart in Fig. 5, the mode selection unit 231 selects whether to operate in the designated value use mode (i.e., execute steps S203 to S206) or to operate in the optimum value calculation mode (i.e., execute steps S207 to S212) depending on whether step S202 is YES or NO.

[0091] The effects of the control device 20 and the material testing system 100 of this embodiment are summarized below.

[0092] In the control device 20 and the material testing system 100 of this embodiment, the control device 20 selects and executes either the designated value use mode or the optimal value calculation mode. In the material testing system 100, when the appropriate PID coefficient value can be specified before the test, the designated value use mode is selected, and the material test can be performed using the appropriate PID coefficient. Therefore, the material test can be performed efficiently. On the other hand, when the appropriate PID coefficient cannot be specified before the test, the optimal value calculation mode is selected, and the material test is performed efficiently while performing the calculation of the optimal value of the PID coefficient and the material test in parallel. In this way, the control device 20 and the material testing system 100 of this embodiment can select and execute either the designated value use mode or the optimal value calculation mode. As a result, the material testing system 100 can perform the material test efficiently whether the PID coefficient used in the material test can be specified in advance or not.

[0093] In the control device 20 and the material testing system 100 of this embodiment, the optimal values ​​of the PID coefficients calculated in the optimal value calculation mode are associated with the test condition information and stored as log data in the storage unit 24. Therefore, log data can be accumulated every time a test is performed.

[0094] Next, a method for setting test conditions using the input device 30 and a setting screen will be described in detail. Fig. 6 to Fig. 8 each show an example of a setting screen for test conditions displayed on the display unit 33 of the input device 30. As described above, the user can input test conditions (e.g., an operation mode) via the input unit 32 of the input device 30.

[0095] For example, the user operates the touch panel while viewing a setting screen displayed on a touch panel display serving as the input device 32 and the display device 33 to select and / or input test conditions. After the user has finished selecting and / or inputting, he or she performs an operation to save the test conditions. This causes the input test conditions to be saved as a set of data files, i.e., "test condition information." The test condition information is temporarily or non-temporarily saved in the input device 30 and transmitted to the control device 20.

[0096] 6 shows an example of a setting screen 50 and input contents when a compression test is performed by the material testing machine 10. The items displayed on the setting screen 50 are as follows. (1) Height correction value: This is an item for setting the magnitude of the correction value to be subtracted from the displayed height value. (2) Control start point: This is an item for setting the point at which the control set in the table on the right of the setting screen 50 (i.e., a table including the columns for name, control mode, control setting, and repetition) is to start. For example, it may be possible to set a "test start point" at which the above-mentioned control is performed from the beginning (at the start of the test), or a "test force" at which the above-mentioned control is started from the point at which a specified test force (3.500 N in the example of FIG. 6) is reached. It may also be possible to set the point at which the above-mentioned control is to start as a percentage from the full scale, such as "0.3% FS" or "0.006% FS." (3) PID Coefficients: If the specified value calculation mode is selected, enter the P coefficient, I coefficient, and D coefficient to be used during the test.

[0097] (4) Name: Enter the name of the test. The user may be able to enter any name. (5) Control mode: Specifies the operation mode under the test conditions. In the present embodiment, the designated value use mode or the optimal value calculation mode is selected. The information indicated by this item is type information. (6) Operation direction: Set the test direction to one of rising (UP), falling (DOWN), and hold (HOLD). Note that the test direction may be set to OFF. If hold is selected here, it may be possible to set the unit (9) described below to time. For example, when performing a tensile test, compression test, bending test, or torsion test, the test direction may be set to rising (UP) or falling (DOWN). For example, when performing a creep test, the test direction may be set to hold (HOLD). (7) Operation type: Select from "strain," "test force," and "stress." In addition to these three types, "position" may also be selectable. When "strain" is selected, the material testing machine 10 operates so that the amount of elongation of the test piece per unit time is constant. When "test force" is selected, the material testing machine 10 operates at a load rate LV [N / s]. When "stress" is selected, the material testing machine 10 operates at a stress rate SV [N / mm 2 When "Position" is selected, the material testing machine 10 operates at a constant speed V [mm / s]. This may be selected, for example, in the case of a relaxation test. (8) Operating value and (9) Unit: Specifies the parameters and units for the operation in the operation type selected in (7). The units selectable in (9) may be determined according to the operation type selected in (7). For example, if "strain" is selected in (7), the unit selectable in (9) may be strain rate (e.g., mm / min). For example, if "test force" is selected in (7), the unit selectable in (9) may be load rate (e.g., N / min or N / s). For example, if "stress" is selected in (7), the unit selectable in (9) may be stress rate (e.g., N / mm 2 / min) may be selectable. The unit of (9) may be automatically determined depending on the selection in (7). (10) Target value: Select either "Test start point" or "Test force" and input the value and unit. If you select "Test start point", set the load value from the start point. If you select "Test force", set the load value to be added to the load value set in "Control start point" in the table in the center left of the setting screen 50 in Figure 6. (11) Repeat: Set whether or not to repeat the control action set for each item.

[0098] The user can set the above items (1) to (11) on the setting screen 50. In addition, in the test condition information, the test performed by the material testing machine 10 can be divided into arbitrary phases over time, and the test conditions for each phase can be set. Hereinafter, this phase is referred to as an "area." In other words, an "area" means each period when the period from the start to the end of a test is divided into arbitrary periods. The number of areas is not limited as long as it is one or more. For example, in the case of a general tensile test and compression test, the number of areas may be one or two. Also, for example, in the case of a general creep test, the number of areas may be two or more.

[0099] For example, in the test conditions shown on the setting screen 50 shown in FIG. 6, there is one tab ("Area 1" tab) for an area including the above items (1) to (11). That is, the area for this test is 1. Note that on the setting screen 50, it is also possible to add an area and set items (1) to (11) for the next area by selecting the additional tab indicated by the dotted line. Also, the setting screen 50 may be capable of setting items other than the above items (1) to (11). Specifically, for example, the following items: (12) End Settings: Set the operation at the end of the test. This setting is done by selecting the End Settings tab (End Settings tab) in Figure 6. (13) Preload: Set whether or not to use preload and the load amount. This setting is done by selecting the Preload tab in Figure 6. (14) Specimen Settings: Set the size, shape, weight, material, etc. of the specimen. This setting is done by selecting the Specimen Settings tab in Figure 6.

[0100] The setting screen 50 may also be provided with an item for selecting or inputting the type of test. Then, the items (6) and / or (7) appropriate for the type of test designated in that item may be automatically input or selected. When the type of test is selected or input on the setting screen 50, the test condition information that stores the settings on the setting screen 50 may include information indicating the type of test.

[0101] Fig. 7 shows the setting screen 50 when the optimum value calculation mode is selected on the setting screen 50 shown in Fig. 6. If the initial PID coefficients to be used in the optimum value calculation mode are predetermined, the "PID coefficient" field for specifying the PID coefficients is not displayed in Fig. 7. On the other hand, if the initial PID coefficients can be set by the user, the "PID coefficient" field may be displayed on the setting screen 50 when the optimum value calculation mode is selected, as shown in Fig. 6, to allow the user to set the initial PID coefficients. Other points are the same as those of the setting screen 50 shown in Fig. 6.

[0102] Figures 8(a) and (b) show an example of a setting screen 50 and its input contents when a creep test is performed by the material testing machine 10. Note that in Figures 8(a) and (b), the same parts as in Figures 6 and 7 will not be described repeatedly. Figures 8(a) and (b) show conditions for the same test, with Figure 8(a) showing settings for the first area (area 1) from the start of the test, and Figure 8(b) showing settings for the second area (area 2) from the start of the test. As shown in the figure, areas 1 and 2 can be viewed and edited by switching tabs.

[0103] In the example of FIG. 8, area 1 means the period until the target load is reached in the creep test. As described above, in the creep test, regardless of the operation mode, a load is applied to the test piece at a constant speed until the target load is reached (S204 to S205 and S207 to S208 in FIG. 5). Therefore, as shown in FIG. 8(a), (6) the operation direction is set to DOWN or UP, and the target load is set to (10) the target value. In the case of the creep test, the speed (or the time until the target load is reached) may be set by the user as (8) the operation value and (9) unit, or may be constant.

[0104] In the example of FIG. 8, area 2 refers to the period after the target load is reached. In a creep test, after the target load is reached, the target load is continued to be applied to the test piece for the set duration (S206 and S211 in FIG. 5). Therefore, as shown in FIG. 8(b), in area 2, (6) Operation direction is set to HOLD. When "HOLD" is selected in the item (6) Operation direction, the duration value can be set together with the unit in (10) Target value. By setting in this manner, it is possible to make the material testing machine 10 continue to apply a constant target load for the set duration. Note that the "constant target load" referred to here is the target load set as the target value in area 1.

[0105] To summarize the test condition information shown in (a) and (b) of Figure 8, the setting of Area 1 includes a target load value, and the setting of Area 2 includes a duration value. The settings of Area 1 and Area 2 also specify the type of operation mode. Therefore, by setting the test conditions as shown in (a) and (b) of Figure 8, the control device 20 can cause the material testing machine 10 to execute a creep test.

[0106] <Second embodiment> A material testing system 200 (FIG. 1) according to a second embodiment of the present invention will be described mainly with reference to FIGS. 9 and 10. The material testing system 200 according to the second embodiment is similar to the material testing system 100 according to the first embodiment, except that in a load rate maintenance test, in addition to a designated value use mode and an optimal value calculation mode, an intermediate mode (an example of a third mode) can be executed. The following describes the differences from the material testing system 100 according to the first embodiment. Points that are not described are the same as those in the material testing system 100 according to the first embodiment.

[0107] The control device 20 of the material testing system 200 of the second embodiment controls the material testing machine 10 in accordance with the flowchart of FIG. 9 during the load rate maintenance test.

[0108] First, the PID control unit 23 of the control device 20 acquires test condition information from the input device 30 (step S301). Next, the mode selection unit 231 determines whether or not the "specified value use mode" is specified in the test condition information (step S302). If the "specified value use mode" is specified (S302: YES), the control execution unit 232 executes the specified value use mode (step S304). Specifically, the steps S103 to S105 (FIG. 2) of the first embodiment are executed.

[0109] If the operation mode specified by the type information is not the "specified value use mode" (S302: NO), the mode selection unit 231 judges whether or not the "optimum value calculation mode" is specified in the test condition information (step S303). If the "optimum value calculation mode" is specified (S303: YES), the control execution unit 232 and the optimum value calculation unit 233 execute the optimum value calculation mode (step S305). Specifically, the steps S106 to S111 of the first embodiment (FIG. 2) are executed.

[0110] If the operation mode specified by the type information is neither the "specified value use mode" nor the "optimum value calculation mode" (S303: NO), that is, if the "intermediate mode" is specified by the type information, the control execution unit 232 executes the intermediate mode (FIG. 10) (step S306). For example, in the case of this embodiment, the specified value use mode, optimal value calculation mode, and intermediate mode are selectable in the "control mode" field of the setting screen (FIGS. 6 to 8) shown in the first embodiment, and when the intermediate mode is selected here, the "intermediate mode" is specified by the type information. In the intermediate mode, the PID control unit 23 executes PID control using the specified PID coefficients until a predetermined condition is satisfied, and after the predetermined condition is satisfied, calculates the optimal value of the PID coefficient, and executes PID control using the calculated optimal value. Specifically, for example, it is as follows.

[0111] The control execution unit 232 first executes steps S103 and S104 of the first embodiment. That is, the control execution unit 232 sets the PID coefficient included in the test condition information as the first PID coefficient (i.e., the usage coefficient) to be used in the loading rate maintenance test (step S103), and applies a load to the test piece TP at the loading rate LV [N / s] specified in the test condition information while performing PID control using the set usage coefficient (S104).

[0112] In the next step S400, the PID control unit 23 judges whether a predetermined condition is satisfied. Specifically, the predetermined condition may be, for example, (1) whether a predetermined time has elapsed after the start of loading, (2) whether the load applied to the test piece TP is equal to or greater than a predetermined value, (3) whether a predetermined number of data points (e.g., 10) or more have been measured, etc. When judging (1), the PID control unit 23 may measure time using an internal clock of the control device 20 or a timer or the like separately provided in the control unit 20.

[0113] When the PID control unit 23 determines that the predetermined condition is not satisfied (S400: NO), it continues the step S104. When the PID control unit 23 determines that the predetermined condition is satisfied (S400: YES), it executes the load application step S107 and the coefficient calculation step S109 in parallel, as in the optimal value calculation mode of the first embodiment. At this time, the coefficient used first in the load application step S107 is the coefficient used set in the step S103.

[0114] Thereafter, the control execution unit 232 executes steps S107 to S111 in the same manner as in the optimum value calculation mode of the first embodiment.

[0115] In the material testing system 200 of the second embodiment, in addition to the specified value use mode and the optimal value calculation mode, an intermediate mode that combines the advantages of both can be used, making it possible to perform material testing more efficiently using more suitable PID coefficients.

[0116] In the intermediate mode, when the number of measured data points is small and it is not easy to calculate the PID coefficients based on the data points with high accuracy, PID control is performed using the specified PID coefficients. Then, when the number of measured data points increases to a certain extent (for example, when the above conditions (1), (2), and (3) are satisfied), calculation and updating of the optimal values ​​of the PID coefficients is started. In this way, according to the intermediate mode, a test can be started using appropriate PID coefficients, and when the optimal values ​​can be calculated with a certain degree of accuracy, the PID coefficients can be replaced with more appropriate PID coefficients during the test.

[0117] <Modification> In the control device 20 and the material testing systems 100 and 200 of the above-described embodiments, the following modifications may also be used.

[0118] [Variation 1] In the above-described embodiments of the material testing systems 100 and 200, a tensile test has been described as an example of a load rate maintenance test. However, the load rate maintenance test may be a compression test, a bending test, a torsion test, or other material tests.

[0119] [Variation 2] In the above embodiment, a load-deformation diagram showing the relationship between the load on the test piece and the displacement of the test piece is obtained in a material test (tensile test) using the material testing systems 100 and 200. However, this is not limited to this. Specifically, for example, a stress-strain diagram or the like may be obtained by a material test. Furthermore, the material testing machine 10 may output various measurement results simply as numerical values, rather than outputting the results as graphs such as a load-deformation diagram and / or a stress-strain diagram. Then, the control device 20 that receives the numerical values, or the input device 30 that further receives the numerical values ​​from the control device 20, may create and display graphs such as a load-deformation diagram and / or a stress-strain diagram.

[0120] [Variation 3] In the above embodiment, the optimum value calculation unit 233 calculates the PID coefficients based on the relationship between the test piece load and the test piece displacement, but this is not limiting. Specifically, for example, the optimum value calculation unit 233 may calculate the PID coefficients based on the test piece displacement and the load application time, or may calculate the PID coefficients based on the load amount and the load application time.

[0121] [Variation 4] In the above embodiment, the PID control is performed with the motor 15 as the control target and the test piece load as the control amount, but the present invention is not limited to this. For example, the control amount of the PID control may be the test piece displacement.

[0122] [Variation 5] In the material testing systems 100 and 200 of the above-described embodiments, the PID control unit 23 of the control device 20 selects an operation mode designated by the type information. However, the method of selecting an operation mode of the material testing system according to the present invention is not limited to this.

[0123] For example, when type information is included in the log data in the storage unit 24, the PID control unit 23 may operate the control device 20 in an operation mode (e.g., a designated value use mode) designated by the type information. When type information is not included in either the test condition information or the log data, the PID control unit 23 may operate the control device 20 in an optimal value calculation mode.

[0124] In this modification, the mode selection unit 231 of the PID control unit 23 refers to the log data in the storage unit 24 either before or after step S102 of the load rate maintenance test or step S202 of the creep test, or in parallel with step S102 or S202. At least one piece of log data accumulated from material tests carried out in the past is stored in the storage unit 24. In each of the at least one piece of log data, test conditions and type information are associated with each other. The mode selection unit 231 searches for log data including test conditions that match the test condition information acquired in step S101 or step S201. Then, when the log data is identified, the mode selection unit 231 reads out the type information indicated by the log data and determines that the type information has been acquired.

[0125] In this modified example, the mode selection unit 231 may not refer to the log data if the type information is included in the test condition information. Alternatively, the mode selection unit 231 may not refer to the test condition information if the operation mode is specified in the log data.

[0126] In the material testing system 100 of the first embodiment, the PID control unit 23 may select the designated value use mode when the test condition information includes a PID coefficient, and may select the optimal value calculation mode when the test condition information does not include a PID coefficient. In this case, the test condition information does not need to include type information.

[0127] In this case, when the test condition information includes a PID coefficient or when the log data in the storage unit 24 includes a PID coefficient, the PID control unit 23 operates the control device 20 in the designated value use mode with the PID coefficient as the coefficient to be used. When neither the test condition information nor the log data includes a PID coefficient, the PID control unit 23 operates the control device 20 in the optimal value calculation mode.

[0128] In this modification, the mode selection unit 231 of the PID control unit 23 refers to the log data in the storage unit 24 either before or after step S102 of the load rate maintenance test or step S202 of the creep test, or in parallel with step S102 or S202. At least one piece of log data accumulated from material tests carried out in the past is stored in the storage unit 24. In each of the at least one piece of log data, test conditions and PID coefficients suitable for the test conditions are associated with each other. The mode selection unit 231 searches for log data including test conditions that match the test condition information acquired in step S101 or step S201. Then, when the log data is identified, the PID coefficients indicated by the log data are read out and it is determined that the PID coefficients have been acquired.

[0129] In this modified example, the mode selection unit 231 may not refer to the log data if the test condition information includes a PID coefficient. Alternatively, the mode selection unit 231 may not refer to the test condition information if the log data includes a PID coefficient.

[0130] The test condition information acquired in step S101 or step S201 may or may not be a perfect match between the test conditions included in the log data. If there is no perfect match, the mode selection unit 231 may determine that the test conditions match when, for example, a predetermined specific item among a plurality of items included in the test condition information matches, when the ratio of matching items is a predetermined number or more, or when the error in each item included in the test condition information is a predetermined value or less.

[0131] [Variation 6] In the control device 20 and material testing systems 100 and 200 of the embodiment and this modification, the optimal values ​​of the PID coefficients calculated in the optimal value calculation mode are stored in the storage unit 24 as log data in association with the test condition information. Therefore, in this modification, when a second or subsequent material test is performed under the same test conditions, the designated value use mode is selected based on the test condition information and the log data even if test condition information that does not include the PID coefficients is input. Therefore, the second or subsequent material tests can be performed efficiently.

[0132] [Variation 7] In the creep test, the PID control unit 23 of the embodiment repeatedly executes the calculation of the optimal value of the PID coefficient by the optimal value calculation unit 233 (step S87) during the execution of the load application step S207, and sets the latest value among the multiple optimal values ​​as the coefficient to be used after the test piece load reaches the target load LT [N]. However, this is not limited to this. Specifically, for example, the PID control unit 23 may calculate the PID coefficient using the test piece load and test piece displacement measured up to that point only after the test piece load reaches the target load LT [N].

[0133] [Variation 8] In the embodiment, the PID control unit 23 (more specifically, the mode selection unit 231) of the control device 20 selects the operation mode of the control device 20. However, this is not limited to this, and for example, the user of the material testing system 100 may select the operation mode of the control device 20.

[0134] [Variation 9] In the embodiment, the PID control unit 23 stores log data in which the optimal values ​​of the PID coefficients calculated in the optimal value calculation mode correspond to test condition information related to the calculation in the memory unit 24 of the control device 20. However, this is not limited to this, and the PID control unit 23 may store the log data in an arbitrary memory unit. The arbitrary memory unit specifically includes, for example, the memory unit 34 of the input device 30, and external storage devices of the material testing systems 100 and 200.

[0135] [Variation 10] In the above embodiment, the log data stored in the memory unit 24 of the control device 20 is not limited to data acquired from past material tests performed by the material testing systems 100 and 200 including the memory unit 24. That is, the log data may be data acquired from material tests using another material testing system. The log data may also be data acquired from material tests previously performed as simulations on software. These log data acquired by different methods may be mixed in the memory unit 24, and the mode selection unit 233 may search for log data matching the test conditions from all of the various log data stored in the memory unit 24.

[0136] [Variation 11] The control device 20 may be taken out of the material testing systems 100 and 200 of the above-described embodiments to be a control device capable of executing PID control of an arbitrary material testing machine. Alternatively, the control device 20 may be regarded as a part of the material testing machine 10.

[0137] [Variation 12] The material testing system 200 of the embodiment may be capable of executing only the optimum value calculation mode and the intermediate mode, may be capable of executing only the designated value use mode and the intermediate mode, or may be capable of executing only the intermediate mode. These aspects also allow efficient material testing using suitable PID coefficients. In particular, even in an aspect in which only the intermediate mode is executable, a test can be started using appropriate PID coefficients and can be replaced with more appropriate PID coefficients during the test. Therefore, a material test can be efficiently performed using suitable PID coefficients.

[0138] As long as the characteristics of the present invention are maintained, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0139] 10 material testing machine; 15 motor; 15a receiving unit; 20 control device; 23 PID control unit; 231 mode selection unit; 232 control execution unit; 233 optimal value calculation unit; 24 memory unit; 30 input device; 100, 200 material testing system

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