Material testing machine load adaptive closed-loop control method and system

Abstract

The application relates to a material testing machine load adaptive closed-loop control method and system, which comprises the following steps: setting initial parameters; initializing the state of a crossbeam, moving the crossbeam to an initial displacement target value in an ADRC closed-loop control mode; outputting a next load target value according to set motion parameters and a final load target value; calculating an expected displacement according to initial values of load closed-loop impedance model parameters; performing displacement ADRC closed-loop control according to the expected displacement and a displacement measurement value to control the movement of the crossbeam; obtaining current load measurement values, displacement measurement values and displacement speed after executing time delay; calculating current load impedance model parameters; judging whether the final load target value is reached, ending the control if the final load target value is reached, and continuously outputting the next load target value and continuously moving if the final load target value is not reached. Compared with the prior art, the application has parameter adaptability in the closed-loop process of different materials and stages, and can always maintain consistent high-precision load control effect.

Description

Technical Field

[0001] The present invention relates to the field of intelligent control, and in particular to a load adaptive closed-loop control method and system for a material testing machine. Background Art

[0002] Materials testing machines are instruments used to measure the physical and mechanical properties of various materials (such as metals, non-metals, and composites), mechanical parts, and engineering structures under varying conditions. To meet the diverse testing standards and requirements of various materials, the control software for materials testing machines must be highly flexible and achieve high-precision control in displacement, load, and strain modes.

[0003] Currently, load control in material testing machines generally utilizes traditional PID closed-loop control strategies. This requires re-tuning parameters based on the material's characteristics when dealing with different materials, placing high demands on the technicians' technical expertise and experience. However, even after parameter tuning, it can be difficult to maintain high-precision control throughout the various stages of the material testing process. Consequently, traditional PID closed-loop control may not provide consistent control accuracy across all stages of load control, impacting the accuracy and reliability of test results. Summary of the Invention

[0004] The purpose of the present invention is to provide a load adaptive closed-loop control method for a material testing machine, which combines displacement and load measurement values ​​to identify load impedance model parameters, and implements load adaptive closed-loop control based on Active Disturbance Rejection Control (ADRC) closed-loop control, so that the system can maintain consistent high-precision control effects in the closed-loop process of different materials and different stages, improve the adaptability of system parameters, reduce the system error of the entire experiment, and ensure the accuracy of material testing.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A load adaptive closed-loop control method for a material testing machine, the method comprising:

[0007] Step S1, setting initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed loop period;

[0008] Step S2: Initialize the beam state and move the beam to the initial displacement target value through the Active Disturbance Rejection Control (ADRC) closed-loop control. While moving, calculate the initial values ​​of the load closed-loop impedance model parameters.

[0009] Step S3: outputting the next load target value according to the set load control acceleration, load control speed and final load target value;

[0010] Step S4, calculating the expected displacement based on the load closed-loop impedance model parameters and the next load target value;

[0011] Step S5, performing displacement ADRC closed-loop control based on the expected displacement and the current displacement measurement value to control the movement of the beam;

[0012] Step S6, delaying according to the set delay time, and obtaining the current load measurement value, displacement measurement value and displacement speed;

[0013] Step S7, calculating the current load closed-loop impedance model parameters based on the recursive least squares method with a forgetting factor according to the current load measurement value, displacement measurement value and displacement velocity;

[0014] Step S8, judging whether the final load target value is reached, if so, ending the control, if not, jumping to step S3.

[0015] Furthermore, in step S2, the step of initializing the beam state includes:

[0016] S201, according to the current beam state, obtain the load measurement value and the initial displacement measurement value, and clear the initial value of the displacement velocity;

[0017] S202, outputting the next displacement target value according to the set load control acceleration, load control speed and initial displacement target value;

[0018] S203, performing displacement ADRC closed-loop control based on the next displacement target value and the current displacement measurement value to control the movement of the beam;

[0019] S204, performing a delay according to the set delay time and obtaining the current load measurement value, displacement measurement value and displacement speed;

[0020] S205, calculating the stiffness coefficient and damping coefficient of the load impedance model according to the current load measurement value, displacement measurement value and displacement velocity;

[0021] S206, determine whether the initial displacement target value is reached, if not, jump to step S201;

[0022] S207, outputting the finally calculated load impedance model stiffness coefficient and damping coefficient as initial values ​​of load closed-loop impedance model parameters;

[0023] The calculation formula of the initial displacement target value in S202 includes:

[0024] x * =x0+Δx,

[0025] Among them, x * is the initial displacement target value, Δx is the initial displacement, and x0 is the initial displacement measurement value.

[0026] Furthermore, the displacement ADRC closed-loop control includes:

[0027] Obtain the target displacement value, current displacement measurement value, displacement velocity target value, extended state observer bandwidth, ADRC closed-loop period, displacement velocity calculation value, and displacement calibration coefficient, where the target displacement value includes the initial displacement target value and the expected displacement;

[0028] Calculate the current displacement estimate and the total disturbance estimate based on the current displacement measurement value, the previous moment displacement estimate, the previous moment control output value, the extended state observer bandwidth, the extended state observer bandwidth, and the ADRC closed-loop period;

[0029] According to the current displacement target value, displacement estimated value, displacement speed target value and displacement speed calculated value, a nonlinear adaptive feedback control law is constructed, and the output value of the control law is calculated according to the adaptive adjustment output range of the displacement speed target value;

[0030] According to the control law output value, the total disturbance estimate and the displacement calibration coefficient, the final ADRC control output value is calculated based on the output feedback linearization principle to control the movement of the beam;

[0031] Determine whether the target displacement value is reached. If not, repeat the above control process. If reached, end the control.

[0032] Furthermore, the calculation formulas for the displacement estimation value and the total disturbance estimation value include:

[0033]

[0034] Where n is the total displacement time, p n is the estimated displacement value at the previous moment, u n is the control output value at the previous moment, p n+1 is the current displacement estimate, x n is the current displacement measurement value, e n is the displacement estimation error, h is the ADRC closed loop period, s x is the displacement calibration coefficient, ω o is the bandwidth of the extended state observer.

[0035] Furthermore, the calculation formula of the control law output value includes:

[0036]

[0037] Among them, d, d0, a and a0 are intermediate calculation parameters, p n is the estimated displacement value at the previous moment, u n is the control output value at the previous moment, p n+1 is the current displacement estimate, x n is the current displacement measurement value, is the displacement target value, is the displacement velocity target value, v n is the calculated value of displacement velocity, c n is the output value of the control law, and sign function is the sign function.

[0038] Furthermore, the calculation formula of the final ADRC control output value includes:

[0039]

[0040] Among them, c n is the output value of the control law, q n+1 is the current total disturbance estimate, s x is the displacement calibration coefficient.

[0041] Furthermore, in step S4, at the initial moment of the cycle, the expected displacement is calculated using the initial values ​​of the load closed-loop impedance model parameters calculated when the beam state is initialized, and in subsequent cycles, the expected displacement is calculated using the load closed-loop impedance model parameters calculated in the previous cycle.

[0042] Furthermore, the load impedance model parameters include the stiffness coefficient and damping coefficient of the load impedance model, and the calculation process includes:

[0043]

[0044] T

[0045] G k =A k A k ,

[0046]

[0047] Among them, k represents the kth time period, y k is the load measurement value, x k is the displacement measurement value, v k is the calculated value of displacement velocity, κ k is the stiffness coefficient, is the damping coefficient, G k is always a 2-dimensional square matrix, and G k By G k-1Accumulated.

[0048] Furthermore, in step S5, the calculation formula for the expected displacement includes:

[0049]

[0050] Among them, k represents the kth time period, d k is the expected displacement, y k is the load measurement value, is the next load target value, x k is the displacement measurement value, v k is the calculated value of displacement velocity, κ k is the stiffness coefficient, is the damping coefficient, is the displacement velocity v k Regression prediction is performed to obtain the displacement velocity prediction value.

[0051] A load adaptive closed-loop control system for a material testing machine, the system comprising:

[0052] Parameter setting module, which sets the initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed-loop period;

[0053] Initialization module obtains the load measurement value and the initial displacement measurement value, and clears the initial displacement velocity value. Based on the initial displacement value and the initial displacement measurement value, the initial displacement target value is calculated. The crossbeam is moved to the initial displacement target value in the displacement ADRC closed-loop control mode. While moving, the initial values ​​of the load closed-loop impedance model parameters are calculated.

[0054] The load adaptive closed-loop control module outputs the next load target value based on the set motion parameters and the final load target value, calculates the expected displacement based on the load closed-loop impedance model parameters and the next load target value, performs displacement ADRC closed-loop control based on the expected displacement and displacement measurement value, controls the movement of the beam, performs a delay based on the set delay time, obtains the current load measurement value, displacement measurement value and displacement speed, and calculates the current load impedance model parameters to determine whether the final load target value has been reached. If so, the control is terminated; if not, the control is continued.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The present invention provides a load adaptive closed-loop control method for a material testing machine. Based on a recursive least squares method with a forgetting factor, it performs real-time identification of load impedance model parameters, adaptively converts load control into displacement control, and then implements load adaptive closed-loop control through displacement ADRC closed-loop control. Compared to traditional load PID control, this method eliminates the need for tuning load closed-loop control parameters. The method exhibits parameter adaptability across closed-loop processes for different materials and stages, maintaining consistent, high-precision load control.

[0057] 2. The load model parameter calculation of the present invention utilizes the forgetting recursive algorithm, which has lower time complexity, greater flexibility, and is easier to deploy on a microcontroller platform;

[0058] 3. In the movement of the crossbeam, the present invention uses an ADRC closed-loop control method with a nonlinear adaptive feedback control law to perform displacement control, without the need to adjust the control law parameters. In addition, the extended state observer therein can estimate the total disturbance outside the system model in real time, and compensate for the total disturbance through feedback linearization. It can adapt well to changes in load and structure during movement, further improving the system's anti-disturbance and parameter adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a flow chart of load adaptive closed-loop control of the present invention;

[0060] Figure 2 This is a flow chart for calculating the initial values ​​of the beam initialization and load impedance model parameters of the present invention;

[0061] Figure 3 This is a block diagram of the displacement ADRC closed-loop control structure of the present invention;

[0062] Figure 4 This is a structural diagram of the load adaptive control system of the material testing machine of the present invention. DETAILED DESCRIPTION

[0063] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0064] Example 1

[0065] This embodiment discloses a load adaptive closed-loop control method for a material testing machine. Figure 1 As shown in Figure 2, the load adaptive closed-loop control method includes the following steps:

[0066] Step S1, setting initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed loop period;

[0067] Step S2, initializing the beam state, moving the beam to the initial displacement target value through displacement ADRC closed-loop control, and calculating the initial values ​​of the load closed-loop impedance model parameters while moving;

[0068] Step S3, initializing the load position generator;

[0069] Step S4, outputting the next load target value through the load position generator according to the set load control acceleration, load control speed and final load target value;

[0070] Step S5, calculating the expected displacement based on the load closed-loop impedance model parameters and the next load target value;

[0071] Step S6, performing displacement ADRC closed-loop control based on the expected displacement and the current displacement measurement value to control the movement of the beam;

[0072] Step S7, delaying according to the set delay time;

[0073] Step S8, obtaining the current load measurement value, displacement measurement value and displacement speed;

[0074] Step S9, calculating the current load closed-loop impedance model parameters based on the recursive least squares method with a forgetting factor according to the current load measurement value, displacement measurement value and displacement velocity;

[0075] Step S10, judging whether the final load target value is reached, if so, ending the control, if not, jumping to step S3.

[0076] In this embodiment, the preliminary preparation of the load adaptive control method for a material testing machine is as follows:

[0077] Taking a certain brand of testing machine as an example, the entire set of material testing machine load adaptive closed-loop control system includes: testing machine host computer, testing machine controller, servo drive, servo motor, material testing machine mechanical platform, displacement sensor, and load sensor;

[0078] Before the test begins, set the initial displacement Δx = 1 mm and the final load target value y * =5000N, forgetting factor λ = 0.95 and delay time Δt = 1ms, the bandwidth of the extended state observer ω o =50 and ADRC closed loop period h=0.001.

[0079] Next, initialize the beam state. The specific steps are as follows: Figure 2 Shown include:

[0080] S201, according to the current beam state, obtain the load measurement value and the initial displacement measurement value, and clear the initial value of the displacement velocity to initialize the displacement position generator;

[0081] S202, the displacement position generator outputs the next displacement target value according to the set load control acceleration, load control speed and initial displacement target value;

[0082] S203, performing displacement ADRC closed-loop control based on the next displacement target value and the current displacement measurement value, controlling the servo driver to drive the motor so that the servo motor drives the beam to move;

[0083] S204, performing a delay according to the set delay time and obtaining the current load measurement value, displacement measurement value and displacement speed;

[0084] S205, calculating the stiffness coefficient and damping coefficient of the load impedance model according to the current load measurement value, displacement measurement value and displacement velocity;

[0085] S206, determine whether the initial displacement target value is reached, if not, jump to step S201;

[0086] S207, outputting the finally calculated load impedance model stiffness coefficient and damping coefficient as initial values ​​of load closed-loop impedance model parameters;

[0087] The calculation formula of the initial displacement target value in step S202 includes:

[0088] x * =x0+Δx,

[0089] Among them, x * is the initial displacement target value, Δx is the initial displacement, and x0 is the initial displacement measurement value;

[0090] The initial displacement is set to Δx = 1 mm, the initial displacement measurement value is x0, and the initial displacement target value can be calculated to obtain x * =x0+1mm.

[0091] After initialization, according to the motion parameters set by the host computer and the final load target value y * =5000N, the load position generator is initialized. In this embodiment, the load position generator is implemented using a T-type position planning method. However, in actual applications, it is not limited to using this method, and also includes, for example, S-type curve planning.

[0092] After initialization is completed, the load position generator outputs the next load target value

[0093] The expected displacement is calculated based on the load closed-loop impedance model parameters and the next load target value. The load closed-loop impedance model parameters used here are the initial values ​​of the load closed-loop impedance model parameters calculated during initialization at the beginning of the material testing machine test. In the subsequent movement control cycle, the load closed-loop impedance model parameters calculated at the end of the previous cycle are used.

[0094] The formula for calculating the expected displacement includes:

[0095]

[0096] Among them, k represents the kth time period, d k is the expected displacement, y k is the load measurement value, is the next load target value, x k is the displacement measurement value, v k is the calculated value of displacement velocity, κ k is the stiffness coefficient, is the damping coefficient, is the displacement velocity v k Regression prediction is performed to obtain the displacement velocity prediction value.

[0097] According to the expected displacement and displacement measurement x k , perform displacement ADRC closed-loop control, control the servo driver to drive the motor, so that the servo motor drives the beam to move.

[0098] The specific process of the displacement ADRC closed-loop control is as follows Figure 3 As shown, specifically including:

[0099] Obtaining a target displacement value, a current displacement measurement value, a displacement speed target value, a displacement speed calculation value, and a displacement calibration coefficient, wherein the target displacement value includes an initial displacement target value and an expected displacement;

[0100] Based on the current displacement measurement value, the displacement estimate value at the previous moment, and the control output value at the previous moment, the extended state observer (ESO) is used to calculate the current displacement estimate and the total disturbance estimate.

[0101] According to the current displacement target value, displacement estimated value, displacement speed target value and displacement speed calculated value, a nonlinear adaptive feedback control law is constructed. Based on the fhan function, the nonlinear adaptive feedback control law can be constructed, and the output range can be adaptively adjusted according to the displacement speed target value to calculate the output value of the control law;

[0102] According to the control law output value, the total disturbance estimate and the displacement calibration coefficient, the final ADRC control output value is calculated based on the output feedback linearization principle to control the movement of the beam;

[0103] Determine whether the target displacement value is reached. If not, repeat the above control process. If reached, end the control.

[0104] In ADRC control, the calculation formulas for the displacement estimate and the total disturbance estimate include:

[0105]

[0106] Where n is the total displacement time, p n is the estimated displacement value at the previous moment, u n is the control output value at the previous moment, p n+1 is the current displacement estimate, x n is the current displacement measurement value, e n is the displacement estimation error, h is the ADRC closed loop period, s x is the displacement calibration coefficient.

[0107] The calculation formula of the control law output value includes:

[0108]

[0109] Among them, d, d0, a and a0 are the intermediate calculation parameters of the fhan function, p n is the estimated displacement value at the previous moment, u n is the control output value at the previous moment, p n+1 is the current displacement estimate, x n is the current displacement measurement value, is the displacement target value, is the displacement velocity target value, v n is the calculated value of displacement velocity, c n is the output value of the control law, and sign function is the sign function.

[0110] The calculation formula of the final ADRC control output value includes:

[0111]

[0112] Among them, c n is the output value of the control law, q n+1 is the current total disturbance estimate, s x is the displacement calibration coefficient.

[0113] After moving, there is a delay of Δt, and the current load measurement value, displacement measurement value and displacement speed are obtained.

[0114] Subsequently, according to the current load measurement value, displacement measurement value and displacement velocity, the current load closed-loop impedance model parameters are calculated based on the recursive least squares method with a forgetting factor. The load impedance model parameters include the stiffness coefficient and damping coefficient of the load impedance model. The calculation process includes:

[0115]

[0116] T

[0117] G k =A k A k ,

[0118]

[0119] Among them, k represents the kth time period, y k is the load measurement value, x k is the displacement measurement value, v k is the calculated value of displacement velocity, κ k is the stiffness coefficient, is the damping coefficient, G k is always a 2-dimensional square matrix, and G k By G k-1 Accumulated, in this embodiment, λ=0.95.

[0120] The derivation process of the calculation formula of the load impedance model stiffness coefficient and damping coefficient includes:

[0121] Discretize the load impedance model and get:

[0122]

[0123] Among them, k represents the kth time period, y k is the load measurement value, x k is the displacement measurement value, v k is the calculated value of displacement velocity, κ k is the stiffness coefficient, is the damping coefficient;

[0124] Then, take β k =y k , define the matrix after obtaining load, displacement and displacement velocity in the kth time period as

[0125] According to the discrete least squares formula Γ k =(A k T A k ) -1 A kT b k The recursive least squares iterative formula of the load impedance model is obtained for the kth and k-1th time periods:

[0126]

[0127] Combined with the forgetting factor λ, take The forgetting recursive least squares calculation formula of the load impedance model is obtained:

[0128]

[0129] Among them, G k is always a 2-dimensional square matrix, and G k By G k-1 Accumulated, the time complexity is from O(n 2 ) is reduced to O(n), and there is no need to store the ever-increasing A k Matrix, greatly reducing the time and space complexity of the algorithm.

[0130] Finally, it is determined whether the final load target value is reached. If so, the control is terminated. If not, the load position generator outputs the next load target value and a new round of control is performed.

[0131] Example 2

[0132] This embodiment discloses a load adaptive closed-loop control system for a material testing machine. Taking any material testing machine as an example, the system is as follows: Figure 4 The components shown include: a testing machine host computer, a testing machine controller, a servo driver, a servo motor, a material testing machine mechanical platform, a displacement sensor, and a load sensor.

[0133] When conducting load tests on a materials testing machine, the machine's host computer configures sensor parameters, calibrates sensors, sets motion parameters, and sets the final load target. The machine's controller's built-in position generator continuously generates the next target value based on the motion parameters and the final load target. Based on displacement and load measurements, the controller uses real-time identification of the load impedance model to achieve adaptive model parameter adaptation. Combined with the load impedance model, the next target load value is converted into the desired displacement. Based on the desired displacement, displacement ADRC closed-loop control is performed, controlling the servo driver to drive the servo motor to rotate the corresponding number of revolutions. The servo motor drives the leadscrew through transmission devices such as belts and gears, which in turn actuates the crossbar on the leadscrew, achieving adaptive load closed-loop control.

[0134] Through the operation of the entire set of load adaptive closed-loop control system of the material testing machine, the testing machine is controlled to accurately follow the input target signal.

[0135] The specific details of the above system can be understood by referring to the relevant descriptions and effects in Example 1.

[0136] Example 3

[0137] This embodiment discloses a load adaptive closed-loop control system for a material testing machine. The system is divided into modules according to specific functions, including:

[0138] Parameter setting module, which sets the initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed-loop period;

[0139] Initialization module obtains the load measurement value and the initial displacement measurement value, and clears the initial displacement velocity value. Based on the initial displacement value and the initial displacement measurement value, the initial displacement target value is calculated. The crossbeam is moved to the initial displacement target value in the displacement ADRC closed-loop control mode. While moving, the initial values ​​of the load closed-loop impedance model parameters are calculated.

[0140] The load adaptive closed-loop control module outputs the next load target value based on the set motion parameters and the final load target value, calculates the expected displacement based on the load closed-loop impedance model parameters and the next load target value, performs displacement ADRC closed-loop control based on the expected displacement and displacement measurement value, controls the movement of the beam, performs a delay based on the set delay time, obtains the current load measurement value, displacement measurement value and displacement speed, and calculates the current load impedance model parameters to determine whether the final load target value has been reached. If so, the control is terminated; if not, the control is continued.

[0141] The specific details of the above modules can be understood by referring to the relevant descriptions and effects in Example 1 and Example 2.

[0142] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A load adaptive closed-loop control method for a material testing machine, characterized in that: The method comprises: Step S1, setting initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed loop period; Step S2, initializing the beam state, moving the beam to the initial displacement target value through displacement ADRC closed-loop control, and calculating the initial values ​​of the load closed-loop impedance model parameters while moving; Step S3: outputting the next load target value according to the set load control acceleration, load control speed and final load target value; Step S4, calculating the expected displacement based on the load closed-loop impedance model parameters and the next load target value; Step S5, performing displacement ADRC closed-loop control based on the expected displacement and the current displacement measurement value to control the movement of the beam; Step S6, delaying according to the set delay time, and obtaining the current load measurement value, displacement measurement value and displacement speed; Step S7, calculating the current load closed-loop impedance model parameters based on the recursive least squares method with a forgetting factor according to the current load measurement value, displacement measurement value and displacement velocity; Step S8, determining whether the final load target value is reached, if so, ending the control, if not, jumping to step S3; The displacement ADRC closed-loop control includes: Obtain the target displacement value, current displacement measurement value, displacement velocity target value, extended state observer bandwidth, ADRC closed-loop period, displacement velocity calculation value, and displacement calibration coefficient, where the target displacement value includes the initial displacement target value and the expected displacement; Calculate the current displacement estimate and the total disturbance estimate based on the current displacement measurement value, the previous moment displacement estimate, the previous moment control output value, the extended state observer bandwidth, the extended state observer bandwidth, and the ADRC closed-loop period; According to the current displacement target value, displacement estimated value, displacement speed target value and displacement speed calculated value, a nonlinear adaptive feedback control law is constructed, and the output value of the control law is calculated according to the adaptive adjustment output range of the displacement speed target value; According to the control law output value, the total disturbance estimate and the displacement calibration coefficient, the final ADRC control output value is calculated based on the output feedback linearization principle to control the movement of the beam; Determine whether the target displacement value is reached. If not, repeat the above control process. If it is reached, end the control process. The calculation formulas for the displacement estimate and the total disturbance estimate include: ， Where n is the total displacement time, is the estimated displacement value at the previous moment, is the control output value at the previous moment, is the current displacement estimate, is the current displacement measurement value, is the displacement estimation error, h is the ADRC closed loop period, is the displacement calibration coefficient, is the bandwidth of the extended state observer; The calculation formula of the control law output value includes: ， in, 、 、 and is the intermediate calculation parameter, is the estimated displacement value at the previous moment, is the control output value at the previous moment, is the current displacement estimate, is the current displacement measurement value, is the displacement target value, is the displacement velocity target value, is the calculated value of displacement velocity, is the control law output value, The function is a symbolic function; The calculation formula of the final ADRC control output value includes: ， in, is the control law output value, is the current total disturbance estimate, is the displacement calibration coefficient.

2. A material testing machine load adaptive closed-loop control method according to claim 1, characterized in that: In step S2, the step of initializing the beam state includes: S201, according to the current beam state, obtain the load measurement value and the initial displacement measurement value, and clear the initial value of the displacement velocity; S202, outputting the next displacement target value according to the set load control acceleration, load control speed and initial displacement target value; S203, performing displacement ADRC closed-loop control based on the next displacement target value and the current displacement measurement value to control the movement of the beam; S204, performing a delay according to the set delay time and obtaining the current load measurement value, displacement measurement value and displacement speed; S205, calculating the stiffness coefficient and damping coefficient of the load impedance model according to the current load measurement value, displacement measurement value and displacement velocity; S206, determine whether the initial displacement target value is reached, if not, jump to step S201; S207, outputting the finally calculated load impedance model stiffness coefficient and damping coefficient as initial values ​​of load closed-loop impedance model parameters; The calculation formula of the initial displacement target value in S202 includes: ， in, is the initial displacement target value, is the initial displacement, is the initial value of displacement measurement.

3. The load adaptive closed-loop control method for a material testing machine according to claim 1, characterized in that: In step S4, at the initial moment of the cycle, the expected displacement is calculated using the initial values ​​of the load closed-loop impedance model parameters calculated when the beam state is initialized. In subsequent cycles, the expected displacement is calculated using the load closed-loop impedance model parameters calculated in the previous cycle.

4. The load adaptive closed-loop control method for a material testing machine according to claim 1, characterized in that: The load impedance model parameters include the stiffness coefficient and damping coefficient of the load impedance model, and the calculation process includes: ， ， ， ， Among them, k represents the kth time period, is the load measurement value, is the displacement measurement value, is the calculated value of displacement velocity, is the stiffness coefficient, is the damping coefficient, is always a 2-dimensional square matrix, and Depend on Accumulated.

5. The method for load adaptive closed-loop control of a material testing machine according to claim 1, characterized in that: In step S5, the calculation formula for the expected displacement includes: ， Among them, k represents the kth time period, is the expected displacement, is the load measurement value, is the next load target value, is the displacement measurement value, is the calculated value of displacement velocity, is the stiffness coefficient, is the damping coefficient, Is the displacement speed Regression prediction is performed to obtain the displacement velocity prediction value.

6. A load adaptive closed-loop control system for a material testing machine, based on the load adaptive closed-loop control method for a material testing machine according to claim 1, characterized in that: The system comprises: Parameter setting module, which sets the initial parameters, including initial displacement value, final load target value, forgetting factor, delay time, load control acceleration, load control speed, displacement calibration coefficient, extended state observer bandwidth and ADRC closed-loop period; Initialization module obtains the load measurement value and the initial displacement measurement value, and clears the initial displacement velocity value. Based on the initial displacement value and the initial displacement measurement value, the initial displacement target value is calculated. The crossbeam is moved to the initial displacement target value in the displacement ADRC closed-loop control mode. While moving, the initial values ​​of the load closed-loop impedance model parameters are calculated. The load adaptive closed-loop control module outputs the next load target value based on the set motion parameters and the final load target value, calculates the expected displacement based on the load closed-loop impedance model parameters and the next load target value, performs displacement ADRC closed-loop control based on the expected displacement and displacement measurement value, controls the movement of the beam, performs a delay based on the set delay time, obtains the current load measurement value, displacement measurement value and displacement speed, and calculates the current load impedance model parameters to determine whether the final load target value has been reached. If so, the control is terminated; if not, the control is continued.

Images