Material testing machine and control method of material testing machine

Abstract

The present invention provides a material testing machine and a control method for the material testing machine that can improve responsiveness and stability to perform feedback control of test conditions. A monitoring quantity conversion unit (23) multiplies the control rigidity of a test piece (TP) by the elongation measured by an elongation measurement unit (22) to calculate an estimated test force. A material test control unit (24) determines, based on the estimated test force, an operation amount for a servo motor (43) to reduce the deviation between the actual test force applied to the test piece (TP) and the target test force corresponding to the test conditions, and performs a tensile test on the test piece (TP).

Description

Technical Field

[0001] The invention relates to a material testing machine and a control method of the material testing machine. Background Art

[0002] In the past, in a material testing machine, in order to perform a material test while maintaining the test conditions, feedback control of the test conditions (test force applied to a test object, tensile speed in a tensile test, etc.) was performed (for example, see Patent Document 1). The material testing machine described in Patent Document 1 includes a load cell for measuring the test force applied to a test piece, applies a tensile load to the test piece so that the test force increases at a constant speed to a target value, and then feedback controls the test force under the condition that the test force is maintained at the target value.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-96841 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In the case of feedback control of conditions set according to test conditions, it is ideal to increase the feedback gain to improve responsiveness. However, if the feedback gain is increased, the noise component superimposed on the detection signal of the sensor used in the measurement of the conditional element is also amplified, so the control is likely to become unstable. In order to reduce the noise component, a structure in which the detection signal of the sensor is input via a low-pass filter is also adopted, but in this case, there is a disadvantage that the stability of the control is reduced due to the delay of the detection signal caused by the low-pass filter.

[0008] The present invention has been made in view of the above background, and an object of the present invention is to provide a material testing machine and a control method of the material testing machine that can perform feedback control of test conditions with improved responsiveness and stability.

[0009] [Technical means to solve the problem]

[0010] The first invention includes: a load mechanism that applies a load to a test object; a first monitoring quantity measuring unit that measures a first monitoring quantity that is a change in a physical quantity generated in the test object or the load mechanism according to the load; a second monitoring quantity measuring unit that measures a second monitoring quantity that is a physical quantity that becomes a test target; a monitoring quantity conversion unit that converts the first monitoring quantity measured by the first monitoring quantity measuring unit into a second monitoring quantity estimated value that is regarded as a measured value of the second monitoring quantity based on a relevant condition that represents the correlation between the first monitoring quantity and the second monitoring quantity in the test object or the load mechanism; and a material test control unit that determines an operation amount for the load mechanism based on the second monitoring quantity estimated value to reduce a deviation between an actual second monitoring quantity in the test object and a target second monitoring quantity corresponding to the test conditions, and performs a material test on the test object.

[0011] According to the first invention, in the second invention, the material test control unit determines the operation amount based on an integrated value of a deviation between a measurement value obtained by the second monitoring amount measuring unit and the target second monitoring amount and the second monitoring amount estimated value.

[0012] According to the second invention, in the third invention, the first monitoring quantity measuring unit measures the movement amount of the load mechanism applied to the test object as the first monitoring quantity, and the second monitoring quantity measuring unit measures the test force applied to the test object by the load as the second monitoring quantity, and the related condition is a control rigidity which is an increase or decrease amount of the test force relative to the movement amount of the load mechanism applied to the test object, and the monitoring quantity conversion unit converts the movement amount of the load mechanism measured by the first monitoring quantity measuring unit into the second monitoring quantity estimated value which is regarded as an estimated value of the test force applied to the test object by multiplying the control rigidity by the measured value obtained by the first monitoring quantity measuring unit.

[0013] According to the third invention, the fourth invention includes a control stiffness calculation unit that calculates the control stiffness based on a correlation between a measurement value obtained by the first monitoring amount measuring unit and a measurement value obtained by the second monitoring amount measuring unit within a predetermined period during execution of the material test.

[0014] According to the third invention or the fourth invention, in the fifth invention, the load mechanism comprises: a pair of clamps, clamping the test object; and a head, connected to one of the pair of clamps, sliding in the direction of changing the interval between the pair of clamps by the rotation of the ball screw; the first monitoring quantity measuring part comprises: an encoder, mounted on the ball screw, outputting a pulse each time the ball screw rotates a specified angle; and a counter, counting the pulses output from the encoder; and the movement amount of the load mechanism is measured based on the count value of the counter.

[0015] The sixth invention is a control method for a material testing machine, which is performed by the following material testing machine, wherein the material testing machine includes: a load mechanism that applies a load to a test object; a first monitoring quantity measuring unit that measures a first monitoring quantity that is a change in a physical quantity generated in the test object or the load mechanism according to the load; a second monitoring quantity measuring unit that measures a second monitoring quantity that is a physical quantity that becomes a test target; and a control device; and the control method of the material testing machine includes: a monitoring quantity conversion step, wherein the control device converts the first monitoring quantity measured by the first monitoring quantity measuring unit into a second monitoring quantity estimated value regarded as a measured value of the second monitoring quantity based on a correlation condition indicating the correlation between the first monitoring quantity and the second monitoring quantity in the test object or the load mechanism; and a material test control step, wherein the control device determines an operation amount for the load mechanism to reduce a deviation between an actual second monitoring quantity in the test object and a specified target second monitoring quantity based on the second monitoring quantity estimated value, and performs a material test on the test object.

[0016] Note that this specification encompasses the entire contents of Japanese Patent Application No. 2018-233186 filed on December 13, 2018.

[0017] [Effects of the Invention]

[0018] According to the first invention, the first monitoring quantity measured by the first monitoring quantity measuring unit is converted into a second monitoring quantity estimated value regarded as a measured value of the second monitoring quantity by a monitoring quantity conversion unit based on the correlation conditions indicating the correlation between the first monitoring quantity and the second monitoring quantity in the test object. Then, the operation amount for the load mechanism is determined by the material test control unit based on the second monitoring quantity estimated value to reduce the deviation between the actual second monitoring quantity in the test object and the target second monitoring quantity corresponding to the test condition. In the above case, when it is difficult to suppress the influence of noise when measuring the second monitoring quantity, the influence of noise can be suppressed by using the measurement value obtained by the first monitoring quantity measuring unit with high noise resistance to perform feedback control of the second monitoring quantity. As a result, the feedback control of the second monitoring quantity as the test condition can be performed with improved responsiveness and stability.

[0019] According to the second invention, by determining the operating amount of the load mechanism based on the deviation between the measured value obtained by the second monitoring amount measuring unit and the target second monitoring amount, the influence of the error when the measured value of the first monitoring amount is converted into the estimated value of the second monitoring amount by the monitoring amount conversion unit can be reduced, and the accuracy of feedback control can be improved.

[0020] According to the third invention, the first monitoring amount, which is the amount of movement of the load mechanism measured by the first monitoring amount measuring unit, is converted into a second monitoring amount estimated value, which is regarded as a measured value of the second monitoring amount, by the monitoring amount converting unit by multiplying the control rigidity of the test object or the load mechanism. Then, the material test control unit determines the amount of operation of the load mechanism based on the second monitoring amount estimated value, thereby enabling feedback control of the test force applied to the test object.

[0021] According to the fourth invention, the control stiffness calculation unit calculates the control stiffness of the test object based on the correlation between the measurement value obtained by the first monitoring quantity measuring unit and the measurement value obtained by the second monitoring quantity measuring unit within a predetermined period during the execution of the material test. Thus, when the control stiffness of the test object changes during the execution of the material test, the conversion error of the second monitoring quantity estimated value can be reduced.

[0022] According to the fifth invention, the amount of movement of the load mechanism is measured using an encoder mounted on a ball screw that slides a head connected to a fixture that clamps a test object. This eliminates the influence of looseness or backlash in a transmission mechanism from a drive source such as a motor that drives the ball screw to the ball screw, and allows the amount of movement of the load mechanism to be measured with good accuracy.

[0023] According to the sixth invention, by implementing the method of the sixth invention using a material testing machine, the same effects as those of the first invention can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a diagram schematically showing the structure of a material testing machine according to an embodiment of the present invention.

[0025] Figure 2 It is the block diagram of the control system.

[0026] Figure 3 It is a flow chart of the feedback control of the test force.

[0027] Figure 4 This is a measurement chart of a tensile test performed using a conventional material testing machine.

[0028] Figure 5 This is a measurement chart when a tensile test is performed using the material testing machine of this embodiment.

[0029] [Explanation of Symbols]

[0030] 1: Material testing machine

[0031] 2: Testing machine body

[0032] 10: Control device

[0033] 16: Displacement measurement unit

[0034] 20: CPU

[0035] 21: Control rigidity calculation unit

[0036] 23: Monitoring quantity conversion department

[0037] 24: Material Testing and Control Department

[0038] 36: Load sensor

[0039] 40: Loading mechanism

[0040] 43: Servo motor

[0041] 45: Encoder

[0042] 90: Extensometer

[0043] 100: PC

[0044] TP: Test piece DETAILED DESCRIPTION

[0045] [1.Structure of material testing machine]

[0046] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0047] Figure 1 It is a diagram schematically showing the structure of a material testing machine 1 according to the present embodiment.

[0048] The material testing machine 1 of the present embodiment is a so-called tensile testing machine, and is a testing machine for testing mechanical properties inherent in a material that determine durability against external forces such as tension and shear.

[0049] The material testing machine 1 includes: a testing machine body 2 for applying a test force as a load to a test piece TP of a material to be tested to perform a tensile test; and a control device 10 for controlling the tensile test operation by the testing machine body 2. Figure 1, an extensometer 90 used when measuring the strain of a test piece TP described later is shown. The extensometer 90 is an automatic extensometer that holds and releases the test piece TP without relying on manual work by the user, and includes an upper arm 92 and a lower arm 93 that hold the test piece TP and displace together with the test piece TP, and a strain gauge 91 that detects the displacement of the upper arm 92 and the lower arm 93.

[0050] [2. Structure of the testing machine body]

[0051] The testing machine body 2 includes: a workbench 30; a pair of screws 31 and 32, which are erected on the workbench 30 and can rotate in a state facing the vertical direction; a crosshead 33, which can move along these screws 31 and 32; a load mechanism 40, which moves the crosshead 33 to apply a load to the test piece TP; and a load sensor 36. The load sensor 36 is a sensor that measures the test force as the tensile load actually acting on the test piece TP and outputs a test force measurement signal A1 representing the measured test force to the control device 10. The test force is equivalent to the second monitoring quantity of the present invention, and the load sensor 36 is equivalent to the second monitoring quantity measuring unit of the present invention. Furthermore, it is also possible to set it as a structure in which the screw is one.

[0052] The pair of screws 31 and 32 include ball screws, and the crosshead 33 is connected to each screw 31 and 32 via a nut (not shown). The load mechanism 40 includes: worm reducers 41 and 42 connected to the lower end of each screw 31 and 32; and a servo motor 43 connected to each worm reducer 41 and 42. In addition, an encoder 45 is mounted on the screw 32, and the encoder 45 generates a position measurement signal A2 that outputs one pulse every time the screw 32 rotates a predetermined angle.

[0053] The load mechanism 40 transmits the rotation of the servo motor 43 to the pair of screws 31 and 32 via the worm reducers 41 and 42 , and the screws 31 and 32 rotate synchronously, whereby the crosshead 33 moves up and down along the screws 31 and 32 .

[0054] An upper clamp 34 for holding the upper end of the test piece TP is attached to the crosshead 33, and a lower clamp 35 for holding the lower end of the test piece TP is attached to the table 30. When the test machine body 2 performs a tensile test, the upper end of the test piece TP is held by the upper clamp 34, and the lower end of the test piece TP is held by the lower clamp 35. The crosshead 33 is raised by the control of the control device 10, thereby applying a test force to the test piece TP. The interval between the upper clamp 34 and the lower clamp 35 is changed by the up-and-down sliding of the upper clamp 34. The upper clamp 34 and the lower clamp 35 correspond to a pair of clamps of the present invention, and the crosshead 33 corresponds to the head of the present invention to which the clamps are connected.

[0055] [3. Structure of control device]

[0056] The control device 10 controls the operation of the test machine body 2 and measures the test status. A personal computer (PC) 100 as an external control device is connected to the control device 10, and the PC 100 communicates with the control device 10 to set the test conditions of the tensile test, instruct the start of the tensile test, monitor the progress of the tensile test, and display and analyze the measured data.

[0057] The control device 10 is an electronic circuit unit composed of a central processing unit (CPU) 20, a memory 11, an interface circuit (not shown), etc. The control device 10 includes: a sensor amplifier 12 for amplifying the test force measurement signal A1 output from the load sensor 36; a counter 13 for counting the number of pulses of the position measurement signal A2 output from the encoder 45; and a servo amplifier 14 for supplying a driving current to the servo motor 43.

[0058] The encoder 45 and the counter 13 constitute a displacement measuring unit 16 for measuring the elongation of the test piece TP. The elongation corresponds to the first monitoring amount of the present invention, and the displacement measuring unit 16 corresponds to the first monitoring amount measuring unit of the present invention. The servo amplifier 14 generates a drive voltage corresponding to the current indication Ic input from the CPU 20 and outputs it to the servo motor 43.

[0059] The control device 10 functions as a control rigidity calculation unit 21, an elongation measurement unit 22, a monitoring amount conversion unit 23, and a material test control unit 24 by executing the control program of the material testing machine 1 stored in the memory 11 by the CPU 20. The control rigidity calculation unit 21 calculates the control rigidity as the increase or decrease amount of the test force relative to the displacement (the movement amount of the upper clamp 34) based on the test force measured by the load sensor 36 and the displacement measured by the displacement measurement unit 16 during the tensile test. The control rigidity is equivalent to the relevant condition of the present invention. The displacement measurement unit 16 and the elongation measurement unit 22 constitute the first monitoring amount measurement unit of the present invention.

[0060] The elongation measuring unit 22 calculates the elongation of the test piece TP by subtracting the displacement at the start of the material test from the displacement measured by the free displacement measuring unit 16. The elongation is equivalent to the movement amount and the first monitoring amount of the present invention. The monitoring amount conversion unit 23 multiplies the control rigidity calculated by the control rigidity calculation unit 21 by the elongation of the test piece TP calculated by the elongation measuring unit 22, and converts the elongation into a test force estimation value regarded as a measured value of the test force applied to the test piece TP. The test force estimation value is equivalent to the second monitoring amount estimation value of the present invention. The material test control unit 24 performs processing for the tensile test of the test piece TP. The processing performed by the monitoring amount conversion unit 23 is equivalent to the monitoring amount conversion step in the control method of the material testing machine of the present invention. The processing performed by the material test control unit 24 is equivalent to the material test control step in the control method of the material testing machine of the present invention.

[0061] The control device 10 receives the test condition command TCd, the test start command TSc, etc. sent from the PC 100. When receiving the test start command TSc, the material test control unit 24 performs the tensile test according to the test conditions indicated by the test condition command TCd. The test condition command TCd indicates the test conditions such as the origin adjustment, the test force, and the tensile speed.

[0062] The material test control unit 24 identifies the measured value of the test force applied to the test piece TP (hereinafter referred to as the measured test force Fs) based on the test force measurement signal A1 amplified by the sensor amplifier 12 during the tensile test. In addition, the material test control unit 24 identifies the displacement amount (elongation, hereinafter referred to as the measured elongation ΔPs) of the test piece TP in the upward direction since the start of the tensile test based on the displacement amount of the test piece TP measured by the displacement amount measurement unit 16. Then, the material test control unit 24 sends the measurement data Md including the measured test force Fs and the measured elongation ΔPs to the PC 100.

[0063] The PC 100 acquires the test conditions of the tensile test set by the operation of the user P, and sends the test condition command TCd to the control device 10. In addition, the PC 100 receives the start of the tensile test instructed by the operation of the user P, and sends the test start command TSc to the control device 10. Furthermore, the PC 100 receives the measurement data Md sent from the control device 10, and displays a monitoring screen showing the measured test force Fs and the measured elongation ΔPs.

[0064] [4. Structure of control system]

[0065] Reference Figure 2 A configuration for performing feedback control on the test force applied to the test piece TP will be described. Figure 2This is a block diagram of the test force control system of this embodiment. The material test control unit 24 performs Figure 2 The I-PD control (Proportional Integral Differential (PID) control) of the block diagram shown in the figure determines the manipulated variable u(t) for the servo motor 43. The material test control unit 24 updates the manipulated variable u(t) in each preset control cycle. Figure 2 The t in represents the execution time point of the control cycle.

[0066] Figure 2 The block diagram of FIG. 5 includes a first processing block 50, which performs a calculation of the deviation e obtained by subtracting the measured test force Fs(t) from the target test force Fc(t) in each control cycle. r (t) related processing. In addition, Figure 2 The block diagram of includes a second processing block 60, which performs processing related to the measured elongation ΔPs(t) (=Ps(t)-Ps(t0)) obtained by subtracting the measured displacement Ps(t0) of the test piece TP at the start of the tensile test from the measured displacement Ps(t) of the test piece TP in each control cycle. Furthermore, Figure 2 The block diagram includes an adder-subtractor 70, which adds the initial value u0 of the operation amount to the first processed value C1(t) obtained by the first processing block 50 and subtracts the second processed value C2(t) obtained by the second processing block 60 to calculate the operation amount u(t) of the servo motor 43 as the control object. The target test force Fc(t) is equivalent to the target second monitoring amount of the present invention.

[0067] In the first processing block 50, the measured test force Fs(t) is subtracted from the target test force Fc(t) by the first subtractor 51 to calculate the deviation e r (t). Then, the deviation e r (t) is input to the first proportional device 52, the integrator 53 and the first differentiator 54, and the outputs of the first proportional device 52 and the first differentiator 54 are added to the output (integrated value) of the integrator 53 by the first adder 55, thereby calculating the first processed value C1(t).

[0068] In the second processing block 60, the measured elongation ΔPs(t) is converted into an estimated test force Fe(t) by a monitoring quantity converter 61. Then, the estimated test force Fe(t) is input to a second proportional device 62 and a second differentiator 63, and the outputs of the second proportional device 62 and the second differentiator 63 are added by a second adder 64, thereby calculating a second processing value C2(t). Figure 2 The transfer function of the block diagram is expressed by the following equation (1).

[0069] [Formula 1]

[0070]

[0071] Among them, u(t): operation amount, e r (t): Deviation obtained by subtracting the measured test force Fs(t) from the target test force Fc(t), K P1 : Proportional gain of the first proportional device 52, T I : Integral gain of the integrator, T D1 : differential gain of the first differentiator 54, ΔPs(t): measured elongation, Stiff: control stiffness of the test piece TP, K P2 : Proportional gain of the second proportional device 62, T D2 : differential gain of the second differentiator 63, u0: initial value of the operation amount.

[0072] [5. Determination of the amount of operation]

[0073] in accordance with Figure 3 The flowchart shown in FIG. 1 illustrates the feedback control of the test force performed when the target value of the test force applied to the test piece TP is set as the experimental condition of the tensile test. The control device 10 performs the feedback control based on the control cycle in each predetermined control period during the tensile test. Figure 3 The test force applied to the test piece TP is feedback-controlled by the processing of the flowchart shown in FIG.

[0074] exist Figure 3 In step S1, the control rigidity calculation unit 21 measures the test force applied to the test piece TP (measures the test force Fs(t)) based on the test force measurement signal A1 output from the load sensor 36. Next, in step S2, the control rigidity calculation unit 21 measures the displacement of the test piece TP (measures the displacement Ps(t)) based on the count value of the counter 13 of the displacement measurement unit 16. In the next step S3, the control rigidity calculation unit 21 calculates the control rigidity Stiff(t) of the test piece TP according to the following formula (2).

[0075] [Formula 2]

[0076]

[0077] Here, Stiff is the control rigidity of the test piece TP, and t to t-1 is the measurement period corresponding to the changes in the test force and the displacement, which corresponds to the predetermined period of the present invention.

[0078] In the above formula (2), the control stiffness Stiff(t) used in the current control cycle is calculated based on the amount of change between the measured value in the previous control cycle and the measured value in the current control cycle. As another configuration, the control stiffness Stiff(t) used in the current control cycle may be calculated based on the amount of change in the measured value in the most recent multiple control cycles. Alternatively, the average value of the control stiffness calculated based on the amount of change in the measured value in the most recent multiple control cycles may be used as the control stiffness Stiff(t) used in the current control cycle.

[0079] In addition, when the change of the control stiffness of the test piece TP during the material test is within an allowable range, the control stiffness may be set to a certain value. Alternatively, when the change of the control stiffness of the test piece TP during the material test can be assumed based on the characteristics of the test piece TP, etc., the control stiffness Stiff(t) in this control cycle may be set based on a pre-set change pattern of the control stiffness.

[0080] In the next step S4, the elongation measuring unit 22 calculates the measured elongation ΔPs(t) by subtracting the measured displacement Ps(t0) at the start of the tensile test from the measured displacement Ps(t) in the current control cycle measured in step S2. Next, steps S5 to S8 are processed by the material test control unit 24. In step S5, the material test control unit 24 obtains the target test force Fc(t) set under the test conditions. The target test force Fc(t) is set to keep the tensile speed of the test piece TP constant, for example, by increasing the test force at a constant speed.

[0081] In the next step S6, the material test control unit 24 subtracts the measured test force Fs(t) from the target test force Fc(t) to calculate the deviation e r Then, in step S7, the material test control unit 24 converts the deviation e r (t) and the measured elongation ΔPs(t) are substituted into the transfer function of the above formula (1) to calculate the operation amount u(t) in this control cycle. The fourth term of the above formula (1) includes the following processing: the control stiffness Stiff(t) is multiplied by the measured elongation ΔPs(t) by the monitoring amount conversion unit 23, thereby converting the measured elongation ΔPs(t) into the estimated test force Fe(t).

[0082] Next, in step S8, the material test control unit 24 outputs a current instruction Ic corresponding to the operation amount u(t) to the servo amplifier 14. Thus, the output torque of the servo motor 43 is adjusted to reduce the deviation between the test force applied to the test piece TP and the target test force Fc(t), thereby feedback controlling the test force.

[0083] [6. Verification of the Effects Obtained by the Present Invention]

[0084] according to Figure 4 and Figure 5 The measurement chart of the tensile test shown in the figure is used to explain the effect of applying the present invention to a material testing machine to perform a tensile test. Figure 4 and Figure 5 Shown as Figure 1 As shown in FIG. 1 , an extensometer 90 is mounted on the test piece TP, and the strain (equivalent to the elongation) of the test piece TP during the tensile test is measured by the strain gauge 91. The test conditions are set to set the strain increase rate (tensile speed) to a constant 0.025 (% / sec), and the target test force Fc (t) of the embodiment in which the test force is increased at a constant speed is set according to the test conditions.

[0085] Figure 4 and Figure 5 In the graph, the horizontal axis is set to the strain (%) of the test piece TP, the left vertical axis is set to the strain increase rate (% / sec), and the right vertical axis is set to the stress (N / mm 2 ) (corresponding to the test force applied to the test piece), and the strain increase rate and stress changes corresponding to the increase in strain are shown.

[0086] Figure 4 As in the conventional material testing machine, the test force is feedback-controlled by PID control, and the deviation e between the measured test force Fs(t) measured by the load sensor 36 and the target test force Fc(t) is shown. rp (=Fc(t)-Fs(t)) decreases. In this case, the influence of the noise superimposed on the test force measurement signal A1 output from the load cell 36 becomes greater. Figure 4 In the equation, Fm1 represents stress, Pm1 represents strain increase rate, and R1 represents the time point when the test piece TP breaks. Figure 4 As shown in E, the variation range of the strain increase rate measured by the extensometer 90 is ±10% or more with respect to 0.025 (% / sec) which is the target value of the strain increase rate.

[0087] In contrast, Figure 5 The test results when the test force is feedback controlled using the estimated test force Fe(t) obtained by converting the measured elongation ΔPs(t) based on the displacement of the test piece TP measured by the displacement measuring unit 16 using the structure of the present embodiment are shown. Figure 5 In the equation, Fm2 represents stress, Pm2 represents strain increase rate, and R2 represents the time point when the test piece TP breaks. Figure 5In the experiment, the variation range of the strain increase rate based on the measured value of the extensometer 90 was about ±2% with respect to the target value of the strain increase rate of 0.025 (% / sec), and it was verified that the accuracy of the feedback control of the test force was improved.

[0088] [7. Other embodiments]

[0089] In the embodiment described, Figure 2 As shown in the block diagram, the deviation e is obtained by subtracting the measured test force Fs(t) from the target test force Fc(t). r (t) is input to the first proportional device 52, the integrator 53, and the first differentiator 54. As another configuration, a configuration in which both or one of the first proportional device 52 and the first differentiator 54 is omitted may be adopted.

[0090] In the embodiment described, Figure 2 As shown in the block diagram shown in FIG. 1 , the test force feedback control is performed by I-PD control. As another structure, the test force feedback control can also be performed by general PD control or PID control. In the above case, the structure is as follows: the deviation obtained by subtracting the estimated test force Fe(t) from the target test force Fc(t) is input to the second proportional device 62 and the second differentiator 63. In addition, when the calculation error of the control stiffness Stiff is not a problem, it can also be set to omit the deviation e from the target test force Fc(t) and the measured test force Fs(t). r (t) The structure of the first processing block 50 is concerned.

[0091] In the embodiment, the following example is shown: the elongation of the test piece TP is used as the first monitoring quantity of the present invention, and the test force applied to the test piece TP is used as the second monitoring quantity of the present invention, and the test force is feedback-controlled. The combination of the first monitoring quantity and the second monitoring quantity is not limited to this. If the influence of the noise overlapping with the measurement signal output by the measuring device used in the measurement of the second monitoring quantity becomes a problem, and the noise resistance of the measuring device of the first monitoring quantity is higher than that of the measuring device of the second monitoring quantity, the effect of the present invention can be obtained. For example, the second monitoring quantity may be torque, pressure, displacement, etc. As measuring devices with which noise is easily overlapped, in addition to force sensors such as load sensors, strain gauges of the type that measure small displacements, etc. can also be listed.

[0092] In the above embodiment, the displacement of the test piece TP is measured by the encoder 45 mounted on the screw 32, but the displacement may be measured by a displacement sensor, a length sensor, a linear meter, a potentiometer, etc. In addition, the displacement may be measured by an encoder mounted on the servo motor 43, a linear scale (linear encoder), etc. As the linear scale, a transmission type photoelectric scale, a reflection type photoelectric scale, a laser holographic scale, an electromagnetic induction scale, etc. may be used.

[0093] In the above embodiment, the servo motor 43 is used as the driving source of the load mechanism 40, but other driving sources such as a hydraulic source may also be used. Figure 2 The approximate formula of the operation object in the block diagram is set according to the specifications of the load mechanism.

[0094] In the described embodiment, Figure 1 The functional blocks shown are schematic diagrams showing components classified according to the main processing contents for easy understanding of the present invention, and may be classified into more components according to the processing contents. In addition, one component may be classified to perform more processing.

[0095] In the above embodiment, the material testing machine 1 for performing a tensile test is shown as the material testing machine of the present invention, but the present invention can be widely applied to a material testing machine that applies a test force to a test object to measure a change in a physical quantity of the test object. For example, the present invention can be applied to a material testing machine that performs a compression test, a bending test, a peeling test, etc.

[0096] In the above embodiment, the displacement measuring unit 16 and the elongation measuring unit 22 constitute a first monitoring amount measuring unit, and the displacement of the upper jig 34 is measured as the first monitoring amount. As another configuration, two or more physical quantities may be measured as the first monitoring amount.

Claims

1. A material testing machine, comprising: A loading mechanism applies a load to the test object; A first monitoring amount measuring unit that measures a first monitoring amount, wherein the first monitoring amount is a change in an amount of elongation generated in the test object or the load mechanism according to the load; a second monitoring quantity measuring unit for measuring a test force serving as a test target as a second monitoring quantity; a monitoring amount conversion unit that calculates a control rigidity as an increase or decrease of the test force relative to the elongation based on the elongation and the test force in the test object or the load mechanism, and converts the elongation measured by the first monitoring amount measuring unit into a test force estimated value to be regarded as a second monitoring amount estimated value of the measured value of the second monitoring amount by multiplying the control rigidity by the elongation; and The material test control unit determines, based on the test force estimated value, an operation amount for the load mechanism for reducing a deviation between the actual test force in the test object and a target test force as a target second monitoring amount corresponding to the test conditions, and executes a material test on the test object.

2. The material testing machine according to claim 1, wherein: The material test control unit determines the operation amount based on an integrated value of a deviation between a measurement value obtained by the second monitoring amount measuring unit and the target second monitoring amount and the second monitoring amount estimated value.

3. The material testing machine according to claim 1, comprising a control rigidity calculation unit, The control stiffness calculation unit calculates the control stiffness based on a correlation between a measurement value obtained by the first monitoring amount measurement unit and a measurement value obtained by the second monitoring amount measurement unit within a predetermined period during execution of the material test.

4. The material testing machine according to claim 1 or 3, wherein: The load mechanism comprises: a pair of clamps for clamping the test object; and a head connected to one of the pair of clamps and sliding in a direction of changing the interval between the pair of clamps by the rotation of the ball screw; The first monitoring amount measuring unit includes: an encoder mounted on the ball screw, outputting a pulse each time the ball screw rotates a predetermined angle; and a counter, counting the pulses output from the encoder; and measuring the movement amount of the load mechanism based on the count value of the counter.

5. A control method for a material testing machine, which is performed by the following material testing machine, the material testing machine comprising: A loading mechanism applies a load to the test object; a first monitoring amount measuring unit for measuring a first monitoring amount, wherein the first monitoring amount is a change in an amount of elongation generated in the test object or the load mechanism according to the load; a second monitoring quantity measuring unit for measuring a test force serving as a test target as a second monitoring quantity; as well as Control devices; The control method of the material testing machine comprises: a monitoring amount conversion step, wherein the control device calculates a control rigidity as an increase or decrease amount of the test force relative to the elongation based on the elongation and the test force in the test object or the load mechanism, and multiplies the control rigidity by the elongation to convert the elongation measured by the first monitoring amount measuring unit into a test force estimated value to be regarded as a second monitoring amount estimated value of the measured value of the second monitoring amount; and A material test control step, wherein the control device determines, based on the test force estimate value, an operation amount for the load mechanism to reduce a deviation between the actual test force in the test object and a target test force specified as a target second monitoring amount, and executes a material test on the test object.

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