Patent Publication Number: US-2023146614-A1

Title: Material testing machine

Description:
CROSS REFERENCE 
     The present application claims priority under 35 U.S.C.§ 119 to Japanese Patent Application No. 2021-152405 filed on Sep. 17, 2021. The content of the application is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a material testing machine. 
     Related Art 
     A control parameter that specifies operation of an actuator included in a testing machine is known. For example, JP 2009-002900 A discloses a motor that causes a crosshead as an actuator included in a testing machine to move up and down, and discloses a gain of PID control that controls driving of the motor as a control parameter that specifies operation of the motor. 
     SUMMARY 
     However, in the testing machine described in JP 2009-002900 A, in a case where an operator adjusts a value of the control parameter, a test for obtaining a response characteristic of the material testing machine is performed every time the value of the control parameter is changed, and it is confirmed whether or not the value of the control parameter after the change is appropriate. 
     According to an embodiment of the present disclosure, there is provided a material testing machine that includes a testing machine main body having an actuator, the material testing machine including an estimation unit that estimates a response characteristic of the material testing machine, in which the estimation unit obtains the response characteristic of the testing machine main body in a state in which a first set value used for a material test performed by the material testing machine is set as a control parameter specifying operation of the actuator, and estimates, based on the obtained response characteristic of the testing machine main body, the response characteristic of the material testing machine in a state in which a second set value different from the first set value is set as the control parameter. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an example of a configuration of a tensile testing machine according to the present embodiment; 
         FIG.  2    is a diagram illustrating an example of a configuration of a control device; 
         FIG.  3    is a diagram illustrating an example of a configuration of a feedback control unit; 
         FIG.  4    is a gain diagram illustrating an experiment result for confirming estimation accuracy of an estimation unit; 
         FIG.  5    is a diagram illustrating an example of a gain diagram displayed by a display control unit; 
         FIG.  6    is a diagram illustrating an example of a phase diagram displayed by a display control unit; 
         FIG.  7    is a diagram illustrating an example of a gain diagram displayed by a display control unit; 
         FIG.  8    is a diagram illustrating an example of a phase diagram displayed by a display control unit; 
         FIG.  9    is a diagram illustrating an example of a gain diagram displayed by a display control unit; 
         FIG.  10    is a diagram illustrating an example of a phase diagram displayed by a display control unit; and 
         FIG.  11    is a flowchart illustrating an example of processing of a control unit. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure is to provide a material testing machine capable of reducing labor of an operator in adjustment of a control parameter. 
     According to an embodiment of the present disclosure, it is possible to obtain the response characteristic of the material testing machine in a case where the value of the control parameter is changed, and thus the operator can adjust the control parameter without performing a test for obtaining the response characteristic of the material testing machine. Therefore, it is possible to reduce the labor of the operator in adjusting the control parameter. 
     Hereinafter, the embodiment of the present disclosure will be described with reference to the drawings. 
     1. CONFIGURATION OF TENSILE TESTING MACHINE 
       FIG.  1    is a diagram illustrating an example of a configuration of a tensile testing machine  1  according to the present embodiment. 
     The tensile testing machine  1  of the present embodiment applies a testing force to a specimen SP to perform a tensile test for measuring mechanical properties such as a tensile strength, a yield point, elongation, and a reduction area of the specimen SP. The testing force is a tensile force. 
     The tensile testing machine  1  includes a testing machine main body  2  that applies the testing force to the specimen SP, which is a material to be tested, to perform the tensile test, and a control unit  3  that controls tensile test operation performed by the testing machine main body  2 . 
     The tensile testing machine  1  corresponds to an example of a “material testing machine”. The tensile test corresponds to an example of a “material test”. 
     As illustrated in  FIG.  1   , the testing machine main body  2  is configured so that a load frame is formed on a base  20 , the load frame being formed by a pair of support columns  21  and  22 , and a yoke  23 , and a crosshead  24  is fixed to the support columns  21  and  22 . 
     A hydraulic actuator  25  is disposed to the base  20 , and a lower gripper  26  for gripping a lower end of the specimen SP is attached to a piston rod  25 A of the hydraulic actuator  25 . An upper gripper  28  for gripping an upper end of the specimen SP is attached to the crosshead  24  via a load cell  27 . 
     The hydraulic actuator  25  corresponds to an example of an “actuator”. 
     A hydraulic direction and a hydraulic amount of the hydraulic actuator  25  are controlled by a servo valve  29 , and the piston rod  25 A extends and contracts. As a result, a distance between the upper gripper  28  and the lower gripper  26  is increased and decreased, and the testing force is applied to the specimen SP fixed between the upper gripper  28  and the lower gripper  26 . A stroke of the hydraulic actuator  25 , that is, displacement of the specimen SP is detected by a differential transformer  30  attached to the hydraulic actuator  25 . 
     The load cell  27  is a sensor that measures the testing force, which is a tensile load applied to the specimen SP, and outputs a testing force measurement signal SG 1  to the control unit  3 . 
     The differential transformer  30  is a sensor that measures a displacement amount of the specimen SP and outputs a displacement measurement signal SG 2  corresponding to the displacement amount to the control unit  3 . 
     A displacement sensor  31  is disposed on the specimen SP. For example, a dumbbell-shaped test piece formed to be constricted in the central portion is used as the specimen SP. The displacement sensor  31  is a sensor that measures an elongation measurement value ED by measuring a distance between a pair of marked points of the specimen SP, and outputs an elongation measurement signal SG 3  to the control unit  3 . The pair of marked points are disposed at an upper portion and a lower portion of the constricted region of the specimen SP. 
     The testing machine main body  2  further includes a power source GE and a hydraulic source GP. 
     The power source GE supplies power to each unit of the testing machine main body  2 . The power source GE supplies power to, for example, various motors and drives the motors. The power source GE supplies power to a hydraulic pump and a hydraulic control valve (which are not illustrated), and drives the hydraulic pump and the hydraulic control valve. 
     The power source GE is configured as, for example, a voltage source. The power source GE supplies power corresponding to each unit of the testing machine main body  2 . For example, the power source GE supplies a voltage of 100 V to the hydraulic pump and the various motors, and supplies a voltage of 10 V to the control unit  3 . 
     The hydraulic source GP supplies a hydraulic pressure to a hydraulic device constituting the testing machine main body  2 . The hydraulic source GP supplies, for example, hydraulic pressure to the hydraulic actuator  25  and drives the hydraulic actuator  25 . That is, the hydraulic actuator  25  is driven by the hydraulic pressure supplied from the hydraulic source GP, and the piston rod  25 A is extended and contracted. 
     The hydraulic source GP includes a hydraulic pump and a hydraulic control valve (which are not illustrated), and generates hydraulic pressure by driving the hydraulic pump. Power is supplied from the power source GE to the hydraulic pump. The hydraulic control valve adjusts the hydraulic pressure output from the hydraulic source GP. 
     The control unit  3  includes a signal input and output device  40  and a control device  50 . 
     The signal input and output device  40  configures an input and output interface circuit that transmits and receives a signal to and from the testing machine main body  2 . The signal input and output device  40  according to the present embodiment includes a first sensor amplifier  41 , a second sensor amplifier  42 , a third sensor amplifier  43 , and a servo amplifier  44 . 
     The first sensor amplifier  41  is a device that amplifies the testing force measurement signal SG 1  output from the load cell  27  to generate a testing force measurement value FD, and outputs the testing force measurement value FD to the control device  50 . The testing force measurement value FD indicates the testing force applied to the specimen SP. 
     The second sensor amplifier  42  is a device that amplifies the elongation measurement signal SG 3  output from the displacement sensor  31  to generate an elongation measurement value ED, and outputs the elongation measurement value ED to the control device  50 . The elongation measurement value ED indicates the elongation of the specimen SP. 
     The third sensor amplifier  43  is a device that amplifies the displacement measurement signal SG 2  output from the differential transformer  30  to generate a displacement measurement value XD, and outputs the generated displacement measurement value XD to the control device  50 . The displacement measurement value XD indicates displacement X of the hydraulic actuator  25 . 
     The servo amplifier  44  is a device that controls the servo valve  29  according to the control of the control device  50 . The control device  50  generates a command value CD based on at least one of the testing force measurement value FD or the displacement measurement value XD, and outputs the generated command value CD to the servo amplifier  44 . The servo amplifier  44  generates a command signal SG 4  indicating the command value CD and outputs the generated command signal SG 4  to the servo valve  29 . The servo valve  29  controls the hydraulic direction and the hydraulic amount with respect to the hydraulic actuator  25  according to the command signal SG 4  output from the servo amplifier  44 . 
     2. CONFIGURATION OF CONTROL DEVICE 
     The control device  50  controls the operation of the testing machine main body  2  based on an operation from the user. The control device  50  causes the testing machine main body  2  to execute the tensile test. 
     In the present embodiment, the “user” includes an operator who adjusts a control parameter  543 . 
     The control device  50  includes a computer including a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), an interface circuit with each of the signal input and output device  40  and an operation panel  51 , and various electronic circuits. 
     The control device  50  is not limited to the computer, and may be configured of one or more appropriate circuits such as an integrated circuit such as an IC chip or an LSI. 
       FIG.  2    is a diagram illustrating an example of a configuration of the control device  50 . 
     The control device  50  includes the operation panel  51  and a control unit  52 . 
     The operation panel  51  includes a touch panel  511  and an input device  512  other than the touch panel  511 , such as a button or a numeric keypad. 
     The touch panel  511  includes a liquid crystal display (LCD), and displays various images on the LCD according to an instruction from the control unit  52 . The touch panel  511  includes a touch sensor disposed along a display surface of the LCD. The touch sensor detects a touch with a user&#39;s fingertip or a pen, and transmits a detection signal to the control unit  52 . 
     The control unit  52  includes, for example, a personal computer, and controls the operation of the control device  50 . The control unit  52  includes a processor  53  and a memory  54 . 
     The processor  53  includes a central processing unit (CPU), and a micro-processing unit (MPU). 
     The memory  54  includes a read only memory (ROM), and a random access memory (RAM). The memory  54  stores a control program  541 , target data  542 , and the control parameter  543 . 
     The target data  542  is time-series data indicating a temporal change in a target value of a physical quantity in the material test. The target data  542  of the present embodiment is time-series data of the target value of the testing force in the tensile test. 
     The control parameter  543  is a parameter that specifies the operation of the hydraulic actuator  25 . In the present embodiment, the operation of the hydraulic actuator  25  is controlled by two-degree-of-freedom PID control. Therefore, the control parameter  543  of the present embodiment includes a proportional gain P, a differential gain D, an integration gain I, a first coefficient b, and a second coefficient c. 
     The control unit  52  is not limited to the personal computer, and may be configured of one or more appropriate circuits such as an integrated circuit such as an IC chip or an LSI. The control unit  52  may be configured as, for example, a tablet terminal or a smartphone. 
     The control unit  52  may include programmed hardware such as a digital signal processor (DSP) and a field programmable gate array (FPGA). The control unit  52  may include a system-on-a-chip (SoC)-FPGA. 
     3. CONFIGURATION OF CONTROL UNIT 
     As illustrated in  FIG.  2   , the control unit  52  includes a communication unit  531 , a feedback control unit  532 , a reception unit  533 , an estimation unit  534 , a first measurement unit  535 , a second measurement unit  536 , and a display control unit  537 . 
     Specifically, the processor  53  of the control unit  52  executes a control program  541  stored in the memory  54  to function as the communication unit  531 , the feedback control unit  532 , the reception unit  533 , the estimation unit  534 , the first measurement unit  535 , the second measurement unit  536 , and the display control unit  537 . 
     The communication unit  531  controls communication with the signal input and output device  40 . 
     For example, the communication unit  531  receives the testing force measurement value FD, the elongation measurement value ED, and the displacement measurement value XD from the signal input and output device  40 . For example, the communication unit  531  transmits the command value CD to the signal input and output device  40 . 
     [3-1. Configuration of Feedback Control Unit] 
     The feedback control unit  532  feedback-controls the hydraulic actuator  25  in the tensile test. 
     In the present embodiment, a case where the feedback control unit  532  performs position control on the testing force measurement signal SG 1  output from the load cell  27  will be described. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement signal SG 2  so that the testing force measurement value FD matches a testing force target value FE, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . 
     The position control indicates that a detection value measured by the sensor or the like is controlled to match the target value. 
     In the present embodiment, a case where the position control is performed on the testing force measurement value FD will be described, but the feedback control unit  532  may perform the position control on the elongation measurement value ED. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement value XD so that the elongation measurement value ED measured by the displacement sensor  31  matches an elongation target value, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . 
     The feedback control unit  532  may execute the position control on the displacement measurement value XD. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement value XD so that the displacement measurement value XD matches a displacement target value, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . 
     The feedback control unit  532  may execute speed control on the testing force measurement value FD. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement value XD so that a testing force measurement value speed matches a target value of a testing force speed, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . The testing force measurement value speed indicates a change amount per unit time of the testing force measurement value FD, and the target value of the testing force speed indicates a target value of the testing force measurement value speed. 
     The speed control indicates that a change amount per unit time of the detection value measured by the sensor or the like is controlled to match the target value. 
     The feedback control unit  532  may execute the speed control on the elongation measurement value ED. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement value XD so that an elongation measurement value speed matches a target value of an elongation speed, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . The elongation measurement value speed indicates a change amount per unit time of the elongation measurement value ED, and the target value of the elongation speed indicates the target value of the elongation measurement value speed. 
     The feedback control unit  532  may execute the speed control on the displacement measurement value XD. In this case, the feedback control unit  532  calculates the command value CD of the displacement measurement value XD so that a displacement measurement value speed matches a target value of a displacement speed, and outputs the command signal SG 4  indicating the command value CD to the servo valve  29 . The displacement measurement value speed indicates a change amount per unit time of the displacement measurement value XD, and the target value of the displacement speed indicates the target value of the displacement measurement value speed. 
     For example, a dynamic strain meter, a pressure gauge, an accelerometer, and the like may be incorporated in the signal input and output device  40 , and the feedback-control may be performed on other measurement values. 
       FIG.  3    is a diagram illustrating an example of a configuration of the feedback control unit  532 . 
     In the present embodiment, two-degree-of-freedom proportional-integral-differential (PID) control is used for the feedback-control. The feedback control unit  532  includes a proportionator  5321 , an integrator  5322 , and a differentiator  5323 . The feedback control unit  532  includes a first multiplier  5324 , a second multiplier  5325 , a first subtractor  5326 , a second subtractor  5327 , a third subtractor  5328 , a first adder  5329 , and a second adder  5330 . 
     The first multiplier  5324  outputs, to the first subtractor  5326 , a first multiplication value MV 1  obtained by multiplying the testing force target value FE by the first coefficient b. The first subtractor  5326  outputs, to the differentiator  5323 , a first deviation E 1  obtained by subtracting the testing force measurement value FD from the first multiplication value MV 1 . The differentiator  5323  outputs a first operation amount U 1  to the first adder  5329 . 
     The second multiplier  5325  outputs, to the second subtractor  5327 , a second multiplication value MV 2  obtained by multiplying the testing force target value FE by the second coefficient c. The second subtractor  5327  outputs, to the first adder  5329 , a second deviation E 2  obtained by subtracting the testing force measurement value FD from the second multiplication value MV 2 . 
     The third subtractor  5328  outputs, to the integrator  5322 , a third deviation E 3  obtained by subtracting the testing force measurement value FD from the testing force target value FE. The integrator  5322  outputs a second operation amount U 2  to the first adder  5329 . 
     The first adder  5329  outputs, to the proportionator  5321 , a first addition value KV 1  obtained by adding the first operation amount U 1 , the second deviation E 2 , and the second operation amount U 2 . The proportionator  5321  outputs a third operation amount U 3  to the second adder  5330 . The second adder  5330  outputs, to the testing machine main body  2 , an operation amount U obtained by adding external disturbance d to the third operation amount U 3 . The operation amount U input to the testing machine main body  2  indicates, for example, an opening and closing amount of the servo valve  29 . 
     Returning to the description of  FIG.  2   , the reception unit  533  receives a second set value as a candidate for a set value to be set as the control parameter  543  in the adjustment of the control parameter  543  by the user. The second set value indicates a set value different from a first set value to be described later, and does not indicate a specific set value. The reception unit  533  can receive a plurality of candidates having different values by receiving a third set value different from the second set value. The reception unit  533  may receive a candidate from the user via the operation panel  51 , or may receive a candidate determined by a functional unit that automatically determines the candidate. The third set value indicates a set value different from the second set value, and does not indicate a specific set value. 
     [3-2. Configuration of Estimation Unit] 
     In a case where the reception unit  533  receives the second set value, the estimation unit  534  estimates a response characteristic of the tensile testing machine  1  in a state in which the second set value is set as the control parameter  543 . In other words, the estimation unit  534  estimates the response characteristic of the tensile testing machine  1  in a case where the second set value is set as the control parameter  543 . The estimation unit  534  estimates, as the response characteristic of the tensile testing machine  1 , a gain characteristic that is a characteristic of a gain to a frequency and a phase characteristic that is a characteristic of a phase to the frequency. 
     The estimation unit  534  estimates the response characteristic of the tensile testing machine  1  based on the following Equations (1) and (2). The response characteristic of the tensile testing machine  1  is a response characteristic of a system including the testing machine main body  2 , the specimen SP attached to the testing machine main body  2 , and the control unit  3 . 
     
       
         
           
             [ 
             
               Math 
               . 
                   
               1 
             
             ] 
           
         
       
       
         
           
             
               
                 
                   
                     Gry 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       P 
                       · 
                       
                         P 
                         ⁡ 
                         ( 
                         s 
                         ) 
                       
                       · 
                       
                         ( 
                         
                           
                             
                               D 
                               · 
                               c 
                               · 
                               s 
                             
                             
                               
                                 s 
                                 N 
                               
                               + 
                               1 
                             
                           
                           + 
                           
                             I 
                             s 
                           
                           + 
                           b 
                         
                         ) 
                       
                     
                     
                       
                         P 
                         · 
                         
                           P 
                           ⁡ 
                           ( 
                           s 
                           ) 
                         
                         · 
                         
                           ( 
                           
                             
                               
                                 D 
                                 · 
                                 s 
                               
                               
                                 
                                   s 
                                   N 
                                 
                                 + 
                                 1 
                               
                             
                             + 
                             
                               I 
                               s 
                             
                             + 
                             1 
                           
                           ) 
                         
                       
                       + 
                       1 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Where Gry(s) represents a transfer function of the tensile testing machine  1  in a case where a configuration of the feedback control unit  532  is the configuration of  FIG.  3   . In Equation (1), the external disturbance d is set to zero. P represents a proportional gain of the proportionator  5321 . P(s) represents a response characteristic of the testing machine main body  2 . D represents a differential gain of the differentiator  5323 . I represents an integration gain of the integrator  5322 . b represents a first coefficient. c represents a second coefficient. s represents a variable in Laplace transform. N represents a filter coefficient. 
     
       
         
           
             [ 
             
               Math 
               . 
                   
               2 
             
             ] 
           
         
       
       
         
           
             
               
                 
                   
                     P 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       
                         Gry 
                         · 
                         
                           s 
                           2 
                         
                       
                       + 
                       
                         Gry 
                         · 
                         N 
                         · 
                         s 
                       
                     
                     
                       
                         
                           
                             
                               
                                 ( 
                                 
                                   
                                     D 
                                     · 
                                     N 
                                     · 
                                     P 
                                     · 
                                     c 
                                   
                                   + 
                                   
                                     P 
                                     · 
                                     b 
                                   
                                   + 
                                   
                                     
                                       ( 
                                       
                                         
                                           
                                             - 
                                             D 
                                           
                                           · 
                                           Gry 
                                           · 
                                           N 
                                         
                                         - 
                                         Gry 
                                       
                                       ) 
                                     
                                     · 
                                     P 
                                   
                                 
                                 ) 
                               
                               · 
                               
                                 s 
                                 2 
                               
                             
                             + 
                           
                         
                       
                       
                         
                           
                             
                               
                                 ( 
                                 
                                   
                                     N 
                                     · 
                                     P 
                                     · 
                                     b 
                                   
                                   + 
                                   
                                     
                                       ( 
                                       
                                         
                                           
                                             ( 
                                             
                                               1 
                                               - 
                                               Gry 
                                             
                                             ) 
                                           
                                           · 
                                           I 
                                         
                                         - 
                                         
                                           Gry 
                                           · 
                                           N 
                                         
                                       
                                       ) 
                                     
                                     · 
                                     P 
                                   
                                 
                                 ) 
                               
                               · 
                               s 
                             
                             + 
                             
                               
                                 ( 
                                 
                                   1 
                                   - 
                                   Gry 
                                 
                                 ) 
                               
                               · 
                               I 
                               · 
                               N 
                               · 
                               P 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Equation (2) is an equation obtained by solving Equation (1) for P(s). 
     The estimation by the estimation unit  534  will be described in detail. 
     Here, Gry(s) obtained by the estimation unit  534  is denoted as Gry_predict(s). 
     The estimation unit  534  obtains P(s) in a state in which the first set value is set as the control parameter  543 . P(s) is denoted as P_actual(s). The first set value is a set value of the control parameter  543  used in the tensile test performed by the tensile testing machine  1 , and is a set value set as the control parameter  543  when the estimation unit  534  performs estimation. The first set value includes a value of the proportional gain P, a value of the integration gain I, a value of the differential gain D, a value of the first coefficient b, and a value of the second coefficient c. Here, the value of the proportional gain P included in the first set value is denoted as P_actual. The value of the differential gain D included in the first set value is denoted as D actual. The value of the integration gain I included in the first set value is denoted as I_actual. The value of the first coefficient b included in the first set value is denoted as b_actual. The value of the second coefficient c included in the first set value is denoted as c_actual. The first set value is included in the control parameter  543  stored in the memory  54 . 
     The estimation unit  534  obtains P_actual(s) by substituting P_actual for P in Equation (2), D actual for D in Equation (2), I_actual for I in Equation (2), b_actual for b in Equation (2), c_actual for c in Equation (2), and Gry_actual(s) for Gry(s) in Equation (2). 
     Gry_actual(s) is the actually measured transfer function of the tensile testing machine  1 . Gry_actual(s) is obtained, for example, by system identification in an autoregressive moving average model (ARMA model). Gry_actual(s) is obtained by the estimation unit  534 . Gry_actual(s) may be obtained in advance before the estimation unit  534  estimates the response characteristic of the tensile testing machine  1 , or may be obtained when the estimation unit  534  estimates the response characteristic of the tensile testing machine  1 . 
     In a case where Gry_actual(s) is obtained by the system identification in the ARMA model, the estimation unit  534  obtains Gry_actual(s) based on the following Equations (3) and (4). 
       [Math. 3] 
         y   t =φ 1   y   t-1 +φ 2   y   t-     2   + . . . +φ p   y   t-     p     +u   t −θ 1   y   t     −1   −θ 2   u   t-2 − . . . −θ q   y   t     −q     (3)
 
     Where y is a response value, and is the testing force measurement value FD in the present embodiment. A subscript “t-p” of y indicates a sampling period. u is a target value and is the testing force target value FE in the present embodiment. A subscript “t-q” of u indicates a sampling period. φ 1 , φ 2 , . . . φ p , θ 1 , θ 2 , . . . θ q  are parameters. 
     
       
         
           
             [ 
             
               Math 
               . 
                   
               4 
             
             ] 
           
         
       
       
         
           
             
               
                 
                   y 
                   = 
                   
                     
                       
                         
                           1 
                           - 
                           
                             
                               θ 
                               1 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                           - 
                           
                             
                               θ 
                               2 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 2 
                               
                             
                           
                           - 
                           … 
                           - 
                           
                             
                               θ 
                               q 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 q 
                               
                             
                           
                         
                         
                           1 
                           - 
                           
                             
                               φ 
                               1 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                           - 
                           
                             
                               φ 
                               2 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 2 
                               
                             
                           
                           - 
                           … 
                           - 
                           
                             
                               φ 
                               p 
                             
                             ⁢ 
                             
                               z 
                               
                                 - 
                                 p 
                               
                             
                           
                         
                       
                       ⁢ 
                       u 
                     
                     = 
                     
                       
                         G 
                         ⁡ 
                         ( 
                         z 
                         ) 
                       
                       · 
                       u 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     Equation (4) is an equation obtained by modifying Equation (3) in a case where y t-p =y t ·z −p  and u t-q =u t ·z −q . Here, z is a variable of Z transform. 
     The estimation unit  534  obtains φ 1 , φ 2 , . . . φ p , θ 1 , θ 2 , . . . θ q  based on an algorithm in the ARMA model by using data of y that is the response value and data of u that is a target value. The estimation unit  534  substitutes the obtained φ 1 , φ 2 , . . . φ p , θ 1 , θ 2 , . . . θ q  into Equation (4) to obtain G(z) of Equation (4). In a case where the estimation unit  534  obtains Gry_actual(s) when estimating the response characteristic of the tensile testing machine  1 , the data of y which is the response value and the data of u which is the target value are stored in the memory  54 . 
     The variable z in the Z transform corresponds to e sT . Here, e is a Napier&#39;s constant, s is a variable in Laplace transform, and T is a sampling period in Z transform. The estimation unit  534  sets z=e sT , and transforms the obtained G(z) into G(s) of Laplace transform. The estimation unit  534  obtains the transformed G (s) as Gry_actual(s). 
     The estimation unit  534  obtains Gry_predict(s) by substituting the obtained P_actual(s) and the second set value received by the reception unit  533  into Equation (1). The second set value includes a value of the proportional gain P, a value of the integration gain I, a value of the differential gain D, a value of the first coefficient b, and a value of the second coefficient c. Here, the value of the proportional gain P included in the second set value is denoted as P candidate. The value of the differential gain D included in the second set value is denoted as D candidate. The value of the integration gain I included in the second set value is denoted as I_candidate. The value of the first coefficient b included in the second set value is denoted as b_candidate. The value of the second coefficient c included in the second set value is denoted as c_candidate. 
     The estimation unit  534  obtains Gry_predict(s) by substituting the obtained P_actual(s) for P(s) in Equation (1), P candidate for P in Equation (1), D candidate for D in Equation (1), I_candidate for I in Equation (1), b_candidate for b in Equation (1), and c_candidate for c in Equation (1). 
     The estimation unit  534  estimates the gain characteristic and the phase characteristic as the response characteristic of the tensile testing machine  1  based on the obtained Gry_predict(s). 
     In a case where the reception unit  533  receives the third set value in addition to the second set value, the estimation unit  534  estimates a first response characteristic that is the response characteristic of the tensile testing machine  1  in a case where the second set value is set as the control parameter  543  and a second response characteristic that is the response characteristic of the tensile testing machine  1  in a case where the third set value is set as the control parameter  543 . The estimation unit  534  estimates the second response characteristic similarly to the estimation for the second set value described above. 
     [3-3. Experiment Result for Estimation Accuracy] 
     An experiment result for confirming the estimation accuracy of the estimation unit  534  will be described. 
       FIG.  4    is a gain diagram illustrating the experiment result for confirming the estimation accuracy of the estimation unit  534 . 
     A graph G 1  in  FIG.  4    indicates gain characteristic estimated by the estimation unit  534 . A graph G 2  in  FIG.  4    indicates actually measured gain characteristic. The gain characteristic indicated by the graph G 2  is a gain characteristic measured in a state in which the second set value used for estimating the gain characteristic indicated by the graph G 1  is set as the control parameter  543 . The gain characteristic indicated by the graph G 2  is a characteristic obtained by an experiment in a case where the frequency is linearly increased from 1 Hz to 50 Hz for 49 seconds with an amplitude range set to ±0.3 mm. 
     An amplitude value indicated by the graph G 1  and an amplitude value indicated by the graph G 2  substantially coincide with each other, and it is found that the estimation unit  534  can accurately estimate the response characteristic of the tensile testing machine  1 . 
     Returning to  FIG.  2   , the first measurement unit  535  measures the response characteristic of the tensile testing machine  1  in a state in which the first set value is set as the control parameter  543 . The first measurement unit  535  inputs a random wave or a sweep wave into the two-degree-of-freedom PID control illustrated in  FIG.  3    in a state in which the first set value is set as the control parameter  543 . According to this, the first measurement unit  535  measures the response characteristic of the tensile testing machine  1  in a state in which the first set value is set as the control parameter  543 . The first measurement unit  535  measures the gain characteristic and the phase characteristic as the response characteristic of the tensile testing machine  1 . 
     The second measurement unit  536  measures the response characteristic of the tensile testing machine  1  in a state in which the second set value received by the reception unit  533  is set as the control parameter  543 . The second measurement unit  536  inputs a random wave or a sweep wave into the two-degree-of-freedom PID control illustrated in  FIG.  3    in a state in which the second set value received by the reception unit  533  is set as the control parameter  543 . According to this, the second measurement unit  536  measures the response characteristic of the tensile testing machine  1  in a state in which the second set value is set as the control parameter  543 . The second measurement unit  536  measures the gain characteristic and the phase characteristic as the response characteristic of the tensile testing machine  1 . 
     The display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , on the touch panel  511 . The display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 , in a superimposing manner. The display control unit  537  displays a Bode diagram to display the response characteristic of the tensile testing machine  1 . 
       FIG.  5    is a diagram illustrating an example of a gain diagram displayed by the display control unit  537 .  FIG.  6    is a diagram illustrating an example of a phase diagram displayed by the display control unit  537 . 
     A graph G 3  and a graph G 5  indicate the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 . In the first set value set as the control parameter  543  at the time of measuring the response characteristic of the tensile testing machine  1 , which is indicated by the graph G 3  and the graph G 5 , the value of the proportional gain P is “203”, the value of the integration gain I is “0.031”, the value of the differential gain D is “0.00”, the value of the first coefficient b is “0.51”, and the value of the second coefficient c is “0.5”. 
     A graph G 4  and a graph G 6  are the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and indicate the response characteristic of the tensile testing machine  1  in a state in which the second set value is set as the control parameter  543 . In the second set value used for estimating the response characteristic indicated by the graph G 4  and the graph G 6 , the value of the proportional gain P is “202”, the value of the integration gain I is “0.144”, the value of the differential gain D is “24.00”, the value of the first coefficient b is “0.91”, and the value of the second coefficient c is “0.5”. 
     As illustrated in  FIGS.  5  and  6   , the display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 , in a superimposing manner. Therefore, without performing a test for obtaining the response characteristic of the tensile testing machine  1  in a case where the set value of the control parameter  543  is changed, the user can confirm a difference between the response characteristic of the tensile testing machine  1  before the set value of the control parameter  543  is changed and the response characteristic of the tensile testing machine  1  in a case where the set value of the control parameter  543  is changed. Accordingly, in the adjustment of the control parameter  543 , the user&#39;s labor can be reduced, and the user can easily determine an appropriate value of the control parameter  543 . 
     In a case where the estimation unit  534  estimates the response characteristic of the tensile testing machine  1  a plurality of times, the display control unit  537  displays a plurality of the response characteristics of the tensile testing machine  1  in a superimposing manner. That is, in a case where the estimation unit  534  estimates the first response characteristic and the second response characteristic, the display control unit  537  displays the first response characteristic and the second response characteristic in a superimposing manner. 
       FIG.  7    is a diagram illustrating an example of a gain diagram displayed by the display control unit  537 .  FIG.  8    is a diagram illustrating an example of a phase diagram displayed by the display control unit  537 . 
     Each of the response characteristic of the tensile testing machine  1 , which is indicated by a graph G 8  and a graph G 13 , the response characteristic of the tensile testing machine  1 , which is indicated by a graph G 9  and a graph G 14 , the response characteristic of the tensile testing machine  1 , which is indicated by a graph G 10  and a graph G 15 , and the response characteristic of the tensile testing machine  1 , which is indicated by a graph G 11  and a graph G 16 , corresponds to an example of the first response characteristic and the second response characteristic. 
     A graph G 7  indicates a gain characteristic measured by the first measurement unit  535 . when measuring the gain characteristic indicated by the graph G 7 , in the first set value set as the control parameter  543 , the value of the proportional gain P is “168”, the value of the integration gain I is “5”, the value of the differential gain D is “40”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     The graphs G 8 , G 9 , G 10 , and G 11  indicate the gain characteristic estimated by the estimation unit  534 . Each of the candidates of the set value used for estimating each of the gain characteristics indicated by the graphs G 8 , G 9 , G 10 , and G 11  corresponds to an example of the second set value and the third set value. 
     In the candidate of the set value used for estimating the gain characteristic indicated by the graph G 8 , the value of the proportional gain P is “192”, the value of the integration gain I is “0.047”, the value of the differential gain D is “50”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     In the candidate of the set value used for estimating the gain characteristic indicated by the graph G 9 , the value of the proportional gain P is “184”, the value of the integration gain I is “0.062”, the value of the differential gain D is “45”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     In the candidate of the set value used for estimating the gain characteristic indicated by the graph G 10 , the value of the proportional gain P is “176”, the value of the integration gain I is “0.083”, the value of the differential gain D is “52”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     In the candidate of the set value used for estimating the gain characteristic indicated by the graph G 11 , the value of the proportional gain P is “165”, the value of the integration gain I is “0.12”, the value of the differential gain D is “63”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     In  FIG.  8   , a graph G 12  indicates a phase characteristic measured by the first measurement unit  535 . The first set value set as the control parameter  543  in the measurement of the phase characteristic indicated by the graph G 12  is the same as the first set value set as the control parameter  543  in the measurement of the gain characteristic indicated by the graph G 7 . 
     In  FIG.  8   , the graphs G 13 , G 14 , G 15 , and G 16  indicates the phase characteristic estimated by the estimation unit  534 . A candidate of the set value used for estimating the phase characteristic indicated by the graph G 13  is the same as the candidate of the set value used for estimating the gain characteristic indicated by the graph G 8 . A candidate of the set value used for estimating the phase characteristic indicated by the graph G 14  is the same as the candidate of the set value used for estimating the gain characteristic indicated by the graph G 9 . A candidate of the set value used for estimating the phase characteristic indicated by the graph G 15  is the same as the candidate of the set value used for estimating the gain characteristic indicated by the graph G 10 . A candidate of the set value used for estimating the phase characteristic indicated by the graph G 16  is the same as the candidate of the set value used for estimating the gain characteristic indicated by the graph G 11 . 
     As illustrated in  FIGS.  7  and  8   , the display control unit  537  displays a plurality of the response characteristics of the tensile testing machines  1  in a superimposing manner. Therefore, without performing a test for obtaining the response characteristic of the tensile testing machine  1 , the user can confirm how the response characteristic of the tensile testing machine  1  change when the set value of the control parameter  543  is changed. Accordingly, in the adjustment of the control parameter  543 , the user&#39;s labor can be reduced, and the user can easily determine an appropriate value of the control parameter  543 . 
     The display control unit  537  can display the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , and the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , in a superimposing manner. 
       FIG.  9    is a diagram illustrating an example of a gain diagram displayed by the display control unit  537 .  FIG.  10    is a diagram illustrating an example of a phase diagram displayed by the display control unit  537 . 
     A graph G 17  and a graph G 20  indicate the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 . when measuring the response characteristic indicated by the graph G 17  and the graph G 20 , in the first set value set as the control parameter  543 , the value of the proportional gain P is “168”, the value of the integration gain I is “5”, the value of the differential gain D is “40”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     A graph G 18  and a graph G 21  are the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and indicate the response characteristic of the tensile testing machine  1  in a state in which the second set value is set as the control parameter  543 . In the second set value substituted into Equation (1) when estimating the response characteristic of the tensile testing machine  1 , which is indicated by the graph G 18  and the graph G 21 , the value of the proportional gain P is “192”, the value of the integration gain I is “0.047”, the value of the differential gain D is “50”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     A graph G 19  and a graph G 22  indicate the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 . when measuring the response characteristic indicated by the graph G 19  and the graph G 22 , in the second set value set as the control parameter  543 , the value of the proportional gain P is “192”, the value of the integration gain I is “0.047”, the value of the differential gain D is “50”, the value of the first coefficient b is “1”, and the value of the second coefficient c is “1”. 
     As illustrated in  FIGS.  9  and  10   , the display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , in a superimposing manner. Therefore, the user can easily confirm the accuracy of the estimated response characteristic of the tensile testing machine  1 . 
     4. PROCESSING OF CONTROL UNIT 
       FIG.  11    is a flowchart illustrating an example of processing of the control unit  52 . 
     Next, in Step S 1 , the estimation unit  534  estimates the response characteristic of the tensile testing machine  1 . In a case where the reception unit  533  receives a plurality of candidates, the estimation unit  534  estimates a plurality of the response characteristics of the tensile testing machine  1 . 
     Next, in Step S 2 , the display control unit  537  generates graph data indicating the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 . 
     Next, in Step S 3 , the display control unit  537  generates graph data indicating the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 . 
     Next, in Step S 4 , the display control unit  537  determines whether or not the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , is set to be displayed. 
     In a case where it is determined that the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , is not set to be displayed (Step S 4 : NO), in Step S 5 , the display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 , in an superimposing manner. 
     In a case where it is determined that the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , is set to be displayed (Step S 4 : YES), in Step S 6 , the display control unit  537  generates graph data indicating the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 . 
     Next, in Step S 7 , the display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 , and the response characteristic of the tensile testing machine  1 , which is measured by the second measurement unit  536 , in a superimposing manner. 
     As described above, the display control unit  537  displays the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 , and the response characteristic of the tensile testing machine  1 , which is measured by the first measurement unit  535 , in a superimposing manner. However, the display control unit  537  may display only the response characteristic of the tensile testing machine  1 , which is estimated by the estimation unit  534 . 
     5. EMBODIMENTS AND EFFECTS 
     It will be understood by those skilled in the art that the above-described embodiments and modification examples are specific examples of the following aspects. 
     (Item 1) 
     According to the present embodiment, there is provided a material testing machine that includes a testing machine main body having an actuator, the material testing machine including an estimation unit that estimates a response characteristic of the material testing machine, in which the estimation unit obtains the response characteristic of the testing machine main body in a state in which a first set value used for a material test performed by the material testing machine is set as a control parameter specifying operation of the actuator, and estimates, based on the obtained response characteristic of the testing machine main body, the response characteristic of the material testing machine in a state in which a second set value different from the first set value is set as the control parameter. 
     In the material testing machine according to Item 1, it is possible to obtain the response characteristic of the material testing machine in a case where the value of the control parameter is changed, and thus the operator can adjust the control parameter without performing a test for obtaining the response characteristic of the material testing machine. Therefore, it is possible to reduce the labor of the operator in adjusting the control parameter. 
     (Item 2) 
     In the material testing machine according to Item 1, a display control unit that displays the response characteristic of the material testing machine, which is estimated by the estimation unit, is provided. 
     In the material testing machine according to item 2, the operator can confirm the response characteristic of the material testing machine in a case where the value of the control parameter is changed, and thus the operator can adjust the control parameter without performing a test for obtaining the response characteristic of the material testing machine. Therefore, it is possible to reduce the labor of the operator in adjusting the control parameter. 
     (Item 3) 
     In the material testing machine according to Item 2, the estimation unit estimates a first response characteristic that is the response characteristic of the material testing machine in a state in which the second set value is set as the control parameter and a second response characteristic that is the response characteristic of the material testing machine in a state in which a third set value different from the second set value is set as the control parameter, and the display control unit displays the first response characteristic estimated by the estimation unit and the second response characteristic estimated by the estimation unit in a superimposing manner. 
     In the material testing machine according to Item 3, without performing a test for obtaining the response characteristic of the tensile testing machine, the operator can confirm how the response characteristic of the material testing machine changes when the set value of the control parameter is changed. Therefore, in the adjustment of the control parameter, the operator&#39;s labor can be reduced, and the operator can easily determine an appropriate value of the control parameter. 
     (Item 4) 
     In the material testing machine according to Item 2 or 3, a first measurement unit that measures the response characteristic of the material testing machine in a state in which the first set value is set as the control parameter is provided, and the display control unit displays the response characteristic of the material testing machine, which is estimated by the estimation unit, and the response characteristic of the material testing machine, which is measured by the first measurement unit, in a superimposing manner. 
     In the material testing machine according to Item 4, Therefore, without performing a test for obtaining the response characteristic of the material testing machine in a case where the set value of the control parameter is changed, the operator can confirm a difference between the response characteristic of the material testing machine before the set value of the control parameter is changed and the response characteristic of the material testing machine in a case where the set value of the control parameter is changed. Therefore, in the adjustment of the control parameter, the operator&#39;s labor can be reduced, and the operator can easily determine an appropriate value of the control parameter. 
     (Item 5) 
     In the material testing machine according to any one of Items 2 to 4, a second measurement unit that measures the response characteristic of the material testing machine in a state in which the second set value is set as the control parameter is provided, and the display control unit displays the response characteristic of the material testing machine, which is estimated by the estimation unit, and the response characteristic of the material testing machine, which is measured by the second measurement unit, in a superimposing manner. 
     In the material testing machine according to Item 5, the operator can compare the estimated response characteristic of the material testing machine with the response characteristic of the material testing machine, and thus the operator can easily confirm the accuracy of the estimated response characteristic of the material testing machine. 
     6. ANOTHER EMBODIMENT 
     The tensile testing machine  1  according to the present embodiment is merely an example of an aspect of the material testing machine according to the present disclosure, and can be arbitrarily modified and applied without departing from the gist of the present disclosure. 
     For example, in the embodiment described above, a case in which the material testing machine is the tensile testing machine  1  is described, but the present embodiment is not limited to this. The material testing machine is only required to apply the testing force to the specimen SP, and deform the specimen SP to perform the material test. For example, the material testing machine may be a compression tester, a bending tester, or a torsion tester. 
     Each functional unit illustrated in  FIGS.  1  and  2    indicates a functional configuration, and a specific mounting form is not particularly limited. That is, hardware corresponding to each functional unit is not necessarily needed to be mounted, and functions of a plurality of the functional units can also be implemented by one processor executing a program. In the above-described embodiment, a part of the functions implemented by software may be implemented by hardware, or a part of the functions implemented by the hardware may be implemented by the software. 
     The processing units of the flowchart illustrated in  FIG.  11    is divided depending on a main processing content for easy understanding of the processing of the control unit  52 . Dividing the processing units is not limited by a dividing method and names of the processing units indicated in the flowchart of  FIG.  11   , and the processing units can be divided into more processing units depending on the processing content, and one processing unit also can be divided to include more processing units. The processing order of the above-described flowcharts is not limited to the illustrated example. 
     The control device  50  of the tensile testing machine  1  can execute the control program  541  corresponding to the display method in the tensile testing machine  1  on the processor  53  included in the control unit  52 . The control program  541  can also be recorded on the recording medium that can be read by the computer. As the recording medium, a magnetic or optical recording medium or a semiconductor memory device can be used. Specifically, a portable recording medium such as a flexible disk, an HDD, a compact disk read only memory (CD-ROM), a DVD, a Blu-ray (registered trademark) disc, a magneto-optical disk, a flash memory, and a card-type recording medium, or a fixed recording medium is exemplified. The recording medium may be a non-volatile storage device such as a RAM, a ROM, and an HDD, which is an internal storage device included in the control unit  52 . The control program  541  may be stored in a server apparatus or the like, and the control program  541  may be downloaded from the server apparatus to the control unit  52 .