CN107263890B - Moment leveling control method and leveling device for composite material press - Google Patents

Abstract

The invention relates to a moment leveling control method and a leveling device for a composite material press, wherein the control method comprises four leveling hydraulic cylinders vertically arranged below four corners of a sliding block, and a target leveling output force of each leveling hydraulic cylinder is controlled to act on the sliding block through a sliding die variable structure control algorithm so as to realize accurate level control on the sliding block; the problems of low leveling efficiency, low leveling precision, low anti-interference capability and the like in a high-speed leveling system are solved. Meanwhile, in the quick pressing process of the press, an optimal sliding mode control algorithm based on a hyperbolic secant function improved approach law is designed to obtain an optimal target output leveling force acting on the sliding block, so that the sliding block can realize horizontal control as quickly and stably as possible, the leveling system is improved to have larger impact and vibration on the main cylinder in the leveling process, and the stability and the leveling precision of the system are improved.

Description

Torque leveling control method and leveling device for composite material press

technical field

The invention relates to a passive torque leveling control method, in particular to a torque leveling control method and a leveling device for a composite material press.

Background technique

Composite material press is one of the important equipment for manufacturing new composite material products. It has the advantages of strong automation, simple process technology, high forming precision, good forming quality, one-time forming and continuous pressing, and is widely used in aircraft , aerospace, submarines, automobiles and other high-tech fields. However, during the press molding process of the hydraulic press, due to the uneven pressure distribution between the main cylinder and the return cylinder, and the difference in the shape and temperature of the composite material product, the system has a strong eccentric load characteristic, such as the unbalanced eccentric load caused by the above reasons , will cause the slider to tilt, which will affect the accuracy of the composite product and even damage the mold.

In order to ensure the precision of the product and protect the mold, considering the impact of the overturning moment caused by the main cylinder, return cylinder and composite materials on the entire press system, the most commonly used method at present is to design a four-corner leveling system to balance the overturning moment. Its design and improvement are composed of the following two aspects: one is the hydraulic system, and the other is the control algorithm. (1) Hydraulic system: Realize rapid horizontal control of the slider through active leveling or passive leveling (refer to patents 200910070144.3, 201010243672.7, 201110183255.2); (2) Algorithm optimization: use different control strategies for synchronous position control (Refer to patents 200910190950.4, 201110182802.5, 201210374508.9); or use the combination of MIMO follow-up fuzzy control method and surface leveling method to realize multi-point decoupling automatic leveling (refer to patent 200810055292.3); or use a double closed-loop control algorithm for leveling and speed regulation Realize high-precision control (refer to patent 201110278650.9). The existing patented design helps to balance the application requirements of the partial load characteristics of the system, but there are still some shortcomings as follows, mainly as follows:

(1) In terms of the existing hydraulic system, although the active leveling method consumes less energy, its installation is relatively complicated, and it is difficult to control during the high-speed leveling process. Although the passive leveling system is easy to install, it hinders the movement of the slider, making the leveling efficiency of the system not high.

(2) In the existing leveling control methods, most of the control strategies use the average value of the displacement of the four leveling hydraulic cylinders as the virtual axis, and the four leveling hydraulic cylinders follow their virtual axes to achieve four leveling The hydraulic cylinder levels the slider. Although it can perform automatic leveling, it cannot obtain accurate leveling output force, and its response speed and leveling efficiency are difficult to meet the requirements of fast leveling.

(3) In terms of algorithm improvement, the existing leveling control methods mostly use the synchronous position PID control algorithm of each leveling hydraulic cylinder to track the virtual axis to perform leveling control. Because the system has the characteristics of multiple input and multiple output systems, coupling systems, and overdrive systems, it is difficult to adjust the control parameters of the PID controller, and it is difficult to ensure high precision requirements under fast leveling conditions. For some improved algorithms, although the system characteristics are considered in the design of the controller, it can meet the leveling requirements of the system, but the control algorithm is complex, and it is difficult to apply the algorithm to engineering practice.

Contents of the invention

In order to solve the above technical problems, the present invention provides a torque leveling control method and a leveling device for a composite material press to solve the problems of low leveling efficiency, low leveling accuracy and low anti-interference ability in a high-speed leveling system Strong and other issues. At the same time, in the rapid pressing process of the press, by designing the optimal sliding mode control algorithm based on the hyperbolic secant function to improve the reaching law, the optimal target output leveling force acts on the slider to make the slider as possible Realize level control quickly and stably, improve the leveling system's large impact and vibration on the master cylinder during the leveling process, and improve the stability and leveling accuracy of the system.

Technical scheme of the present invention is as follows:

A torque leveling control method for a composite material press, in which leveling hydraulic cylinders are vertically arranged under the four corners of the slide block; the following steps are performed in sequence:

Step 1: At the beginning of leveling, collect the displacement values of the four leveling hydraulic cylinders;

Step 2: Process the displacement signal to obtain the displacement difference and speed difference of the diagonal leveling hydraulic cylinder;

Step 3: Use the displacement difference and velocity difference in step 2 as the input of the sliding mode variable structure control algorithm to obtain the target leveling force difference of the diagonal leveling hydraulic cylinder;

Step 4: Obtain the target output forces of the four leveling hydraulic cylinders respectively according to the optimal force distribution algorithm;

Step 5: Repeat the process from step 2 to step 4, and adjust the slider m times until the horizontal accuracy requirement is met.

Wherein, before step 1, a virtual axis is first created, and the virtual axis is the average value of the displacements of the four leveling hydraulic cylinders; the four leveling hydraulic cylinders respectively track the virtual axis.

Wherein, a judgment procedure is set in step 5, that is, when the displacement difference between each leveling hydraulic cylinder and the virtual axis is within a certain range, the automatic leveling ends.

Among them, in the step 3, the mathematical model of the slider is established through the moment balance equation of the slider, the geometric relationship between the four leveling hydraulic cylinders and the kinematic equation and converted into a state space equation, and then combined with the virtual axis, the sliding mode variable structure control algorithm is designed.

Wherein, the design of the sliding mode variable structure control system includes the design of the sliding mode surface and the design of the sliding mode variable structure control law.

Among them, the optimal sliding mode surface is s ₁ =x ₁ +a·x ₃ , s ₂ =x ₂ +b·x ₄ , where the values of a and b determine the convergence rate of s ₁ and s ₂ ;

s ₁ : sliding surface 1;

s ₂ : sliding surface 2;

a: Convergence coefficient of sliding surface 1;

b: Convergence coefficient of sliding surface 1;

x ₁ : The displacement difference between the first leveling hydraulic cylinder and the third leveling hydraulic cylinder;

x ₂ : The displacement difference between the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder;

x ₃ : the speed difference between the first leveling hydraulic cylinder and the third leveling hydraulic cylinder;

x ₄ : Speed difference between the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder.

其中，k₁、k₂的取值决定趋近滑模面的程度；Wherein, the improved reaching law of the sliding mode variable structure control law is

Among them, the values of k ₁ and k ₂ determine the degree of approaching the sliding mode surface;

k ₁ : reaching law coefficient; k ₂ : reaching law coefficient; s _(t) : sliding mode surface.

Among them, the process of the optimal force distribution algorithm described in step 4 is: among the target leveling output forces of the diagonal leveling hydraulic cylinder, there is always a target leveling output force d, and the leveling with the smaller target output force The target leveling output force d of the hydraulic cylinder, the target leveling output force of the leveling hydraulic cylinder with a larger target output force is the sum of the difference between d and the target output leveling force of the diagonal leveling hydraulic cylinder.

Among them, before step 1, it is judged whether the slider has reached the leveling position. If it has not reached the leveling start position, the four leveling hydraulic cylinders and the slider will perform position closed-loop control; until the slider reaches the leveling position, the four leveling hydraulic cylinders will The leveling hydraulic cylinder performs leveling control by outputting different leveling forces.

Among them, the way for the four leveling hydraulic cylinders to track the virtual axis is to make the variance of the displacement between the four leveling hydraulic cylinders and the virtual axis tend to be small, that is, the displacement difference of the diagonal leveling hydraulic cylinders quickly converges to zero.

The present invention has following beneficial effects:

1. The present invention adopts the sliding mode variable structure control method based on the hyperbolic secant function to improve the reaching law to control the level of the slider, which effectively avoids the large impact and impact of the leveling system on the movement of the slider during the leveling control. vibration, while improving the response speed and leveling accuracy of the system. The sliding mode variable structure control system design process first establishes a mathematical model based on the slider system and converts it into a state space equation. The decoupling matrix transformation is performed on the multi-input and multi-output system to obtain the decoupling model, and then the optimal sliding mode surface is designed in combination with the optimal control, so that the system has a good inhibitory effect on parameter perturbation and system interference, and at the same time improves the traditional Reaching law, the design is based on the improved reaching law of hyperbolic secant function, which can weaken the chattering of the system, enhance the adaptability of the algorithm, and can control the level of the slider with a faster response speed and can control unknown disturbances and parameters. Perturbation has a better suppression effect and improves the robustness of the system.

2. The present invention uses the displacement difference and speed difference of each leveling hydraulic cylinder as the controller input method, which effectively avoids measuring the inclination angle of the slider around the x-axis and the y-axis directly through the inclination sensor, and simplifies the installation The mechanical structure of the tilt sensor. The difference between the leveling output force of each diagonal hydraulic cylinder acts on the slider, so that the slider can be controlled horizontally, effectively avoiding the influence of the steady-state error of the output leveling force of each leveling hydraulic cylinder on the level control of the slider. Influence. Especially in the process of high-speed leveling, the pressure control of the leveling hydraulic cylinder cannot achieve accurate pressure closed-loop control due to the dead zone, hysteresis, leakage and other characteristics of the system. The steady-state error, the actual control input has not changed, and can still achieve a high leveling accuracy, which improves the system adaptability.

3. The present invention adopts the pressure control method of four leveling hydraulic cylinders, and the pressure control response speed is fast, thereby improving the response speed of the system. At the same time, the method of torque leveling combined with the principle of optimal force distribution not only effectively solves the overdrive problem of four-corner leveling, but also optimizes the target output leveling force of each leveling hydraulic cylinder, thus avoiding large The impact and vibration of the machine increase the service life of the press.

Description of drawings

Fig. 1 is the schematic diagram of leveling device of the present invention;

Fig. 2 is a schematic diagram of the sliding mode variable structure control system design method of the present invention;

Fig. 3 is the operation flow chart of the torque leveling control method used in the composite material press according to the present invention;

Fig. 4 is a schematic diagram of the controller and various sensors of the present invention.

The reference signs in the figure represent:

1-master cylinder, 11-first displacement sensor, 2-slider, 3-return cylinder, 31-first pressure sensor, 41-second displacement sensor, 42-second pressure sensor, 5-controller, 51- Data acquisition module, 52-data processing module, 521-data storage module, 522-comparison module, 523-calculation module, 53-data output module, 54-regulation module, 6-first leveling hydraulic cylinder, 7-second Leveling hydraulic cylinder, 8-the third leveling hydraulic cylinder, 9-the fourth leveling hydraulic cylinder.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 and Figure 4 represent a composite material press leveling device, including a master cylinder 1 arranged in sequence from top to bottom, a slide block 2 for installing a mold, a return cylinder 3 and a controller 5; the master cylinder 1 The hydraulic rod of the slider 2 is fixed on the upper end surface of the slider 2, and the hydraulic rod of the return cylinder 3 is fixed on the lower end surface of the slider 2; the four corners below the slider 2 are respectively provided with leveling hydraulic cylinders; the leveling mechanism It also includes the first displacement sensor 11 for collecting the displacement signal of the master cylinder 1, the first pressure sensor 31 for collecting the pressure signal of the return cylinder 3, and the second displacement sensor 41 for collecting the displacement signal of the leveling hydraulic cylinder; The data acquisition module 51, data processing module 52, data output module 53 and control module 54 of signal connection; The signal of the first displacement sensor 11, the first pressure sensor 31 and the second displacement sensor 41 is transmitted to The data processing module 52 processes and obtains the target output force of the leveling hydraulic cylinder, and the target output force signal is transmitted to the control module 54 through the data output module 53; the control module 54 adjusts the output force of the leveling hydraulic cylinder according to the target output force.

Wherein, the data processing module 52 includes a data storage module 521 , a comparison module 522 for comparing with the state space equation of the slider 2 , and a calculation module 523 for calculating the output leveling force of the leveling hydraulic cylinder.

Wherein, the leveling hydraulic cylinder is a double-acting single-rod cavity hydraulic cylinder.

Wherein, the leveling hydraulic cylinders are respectively supplied with oil by an oil pump (not shown in the figure), and a second pressure sensor 42 is arranged in the leveling hydraulic cylinder; the second pressure sensor 42 is electrically connected to the data acquisition module 51 signal connection.

The specific flow chart is as follows:

Step 1: The controller 5 adjusts the pressure of the master cylinder 1 and the return cylinder 3 according to the signals of the first displacement sensor 11 and the first pressure sensor 31, by judging whether the slider 2 has reached the leveling position, if it has not reached the leveling start position, The first leveling hydraulic cylinder 6 , the second leveling hydraulic cylinder 7 , the third leveling hydraulic cylinder 8 , and the fourth leveling hydraulic cylinder 9 work with the slide block for position closed-loop control. When the slider 2 reaches the leveling position, the four leveling hydraulic cylinders output different leveling forces for leveling control.

Step 2: When the slider reaches the leveling position, the system will use the comparison module 522 to compare and judge whether the leveling accuracy of each leveling hydraulic cylinder meets the requirements. If the leveling accuracy meets the requirements, that is, each of the four leveling hydraulic cylinders The difference between the displacement of the horizontal hydraulic cylinder and the virtual axis is within c mm, and the four-corner leveling control system will maintain the original leveling output force and continue to perform precise position closed-loop control with the master cylinder. If the leveling accuracy cannot meet the requirements, the four-corner leveling control system collects the displacement signals of the four leveling hydraulic cylinders through the second displacement sensor 41 and inputs them to the calculation module 523 for calculation.

Step 3: The calculation process of the calculation module 523 is as follows; the instantaneous velocity of the four leveling hydraulic cylinders is obtained by calculating the derivative of the displacement with respect to time, and the displacement difference and speed difference of each diagonal cylinder are obtained through program processing, that is, the first leveling hydraulic pressure The displacement difference x ₁ and the speed difference x ₃ of the cylinder 6 and the third leveling hydraulic cylinder 8, the displacement difference x ₂ and the speed difference x ₄ of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9; The displacement difference and velocity difference of the angular leveling hydraulic cylinders are used as the input of the sliding mode variable structure control algorithm, and the difference between the target leveling output forces of the required diagonal leveling hydraulic cylinders can be obtained through calculation, that is, the first leveling hydraulic cylinder 6 The difference u ₁ between the target leveling output force of the third leveling hydraulic cylinder 8 and the target leveling output force of the third leveling hydraulic cylinder 8, the difference between the target leveling output force of the second leveling hydraulic cylinder 7 and the target leveling output force of the fourth leveling hydraulic cylinder 9 u ₂ .

Step 4: From the difference in the target leveling output force of each diagonal leveling hydraulic cylinder obtained in step 3, the target leveling output force of each leveling hydraulic cylinder can be obtained from the four-cylinder leveling force distribution algorithm, that is, the first leveling Hydraulic cylinder 6 target leveling output force F ₁ , second leveling hydraulic cylinder 7 target leveling output force F ₂ , third leveling hydraulic cylinder 8 target leveling output force F ₃ , fourth leveling hydraulic cylinder 9 target leveling output force The horizontal output force F ₄ acts on the level control of the slider 2 to improve the stability and response speed of the leveling process.

Step 5: Determine whether the leveling end position has been reached, if not, repeat the process from step 2 to step 4. Otherwise, the leveling ends.

Figure 2 represents a sliding mode variable structure control system design method for a passive leveling system with multiple inputs and multiple outputs.

The specific design method is as follows:

分别为与x轴和y轴的倾角；F₁、F₂、F₃、F₄分别为四个调平液压缸的目标输出调平力；J_x、J_y分别为滑块绕x轴和y轴的转动惯量；F_p为未知偏载力；四个调平液压缸距离x轴的距离为l_x；距离y轴的距离l_y；偏载力到x轴的距离为r_x；偏载力到y轴的距离为r_y。跟据刚体的定轴转动规律可得：Step 1: First mathematically model the slider,

are the inclination angles with the x-axis and y-axis; F ₁ , F ₂ , F ₃ , and F ₄ are the target output leveling forces of the four leveling hydraulic cylinders; J _x , J _y are the sliders around the x-axis and the The moment of inertia of the y-axis; F _p is the unknown eccentric load force; the distance from the four leveling hydraulic cylinders to the x-axis is l _x ; the distance from the y-axis is l _y ; the distance from the eccentric load to the x-axis is r _x ; The distance from the load to the y-axis is r _y . According to the law of fixed axis rotation of a rigid body, we can get:

According to the geometric relationship of the four leveling hydraulic cylinders:

和

可用四个调平液压缸的速度和位移去描述滑块绕x轴和y轴的倾角误差。结合运动学方程可得：Simultaneous formula (1) and formula (2) can be eliminated

and

The speed and displacement of the four leveling hydraulic cylinders can be used to describe the inclination error of the slider around the x-axis and y-axis. Combined with the kinematic equations:

y _i are the displacements of the i-th leveling hydraulic cylinder; v _i are the speeds of the i-th leveling hydraulic cylinder;

Combining formula (1), formula (2) and formula (3) can obtain its mathematical model, and transform it into a state variable with the displacement difference and speed difference of the diagonal leveling hydraulic cylinder, and the diagonal leveling hydraulic cylinder The difference between the target leveling output force of the leveling hydraulic cylinder is the output state space equation;

Step 2: Design a sliding mode variable structure control algorithm based on the state space equation designed in step 1. The design of the sliding mode variable structure control system is divided into two parts: one part is the design of the sliding mode surface, and the other part is the design of the sliding mode variable structure control law. The specific design process is as follows:

Step 1: Since the system has the system characteristics of multiple inputs and multiple outputs, it is first necessary to decouple the state space equation, that is, matrix transformation, to obtain the corresponding decoupling model. Based on the decoupled model, the optimal sliding mode surface is designed in combination with the optimal control principle, so that the determined sliding mode is asymptotically stable and has good dynamic quality. The designed optimal sliding mode surface is s ₁ =x ₁ +a·x ₃ , s ₂ =x ₂ +b·x ₄ , where the values of a and b determine the convergence rate of s ₁ and s ₂ ;

s ₁ : sliding surface 1;

s ₂ : sliding surface 2;

a: Convergence coefficient of sliding surface 1;

b: Convergence coefficient of sliding surface 1;

x ₁ : The displacement difference between the first leveling hydraulic cylinder and the third leveling hydraulic cylinder;

x ₂ : The displacement difference between the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder;

x ₃ : the speed difference between the first leveling hydraulic cylinder and the third leveling hydraulic cylinder;

x ₄ : Speed difference between the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder.

其中，k₁、k₂的取值决定趋近滑模面的程度；Step 2: After designing the corresponding optimal sliding mode surface, it is necessary to design the control law of the sliding mode variable structure control algorithm, that is, how to select the sliding mode control law u ⁺ and u ^- so that the arrival condition is satisfied, so that on the switching surface A sliding mode region is formed on it. In order to ensure that the state of the system tends to the sliding mode switching surface with a better motion state, a sliding mode variable structure control law based on the improved reaching law of the hyperbolic secant function is designed. The improved reaching law is

Among them, the values of k ₁ and k ₂ determine the degree of approaching the sliding mode surface;

k ₁ : reaching law coefficient; k ₂ : reaching law coefficient; s _(t) : sliding mode surface.

Step 3: For the sliding mode control algorithm based on hyperbolic secant function improved reaching law designed in step 2, the displacement difference and speed difference of the four leveling hydraulic cylinders are used as the controller input, that is, x ₁ =y ₁ - y ₃ , x ₂ =y ₂ -y ₄ , x ₃ =v ₁ -v ₃ , x ₄ =v ₂ -v ₄ , to obtain the output target adjustment of the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8 The difference u ₁ between the leveling force and the difference u ₂ between the target output leveling force of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9, namely u ₁ =F ₁ -F ₃ , u ₂ =F ₂ -F ₄ .

Step 4: From step 3, it can be seen that the difference u ₁ between the leveling output force of the first leveling hydraulic cylinder 6 and the leveling output force of the third leveling hydraulic cylinder 8, the leveling output force of the second leveling hydraulic cylinder 7 and the fourth The difference u ₂ of the target leveling output force of the leveling hydraulic cylinder 9 . Through the optimal distribution algorithm, among the target leveling output forces of the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8, there is always a target leveling output force of d kN, and the target leveling hydraulic cylinder of the diagonal The leveling output force is judged by the positive or negative of the designed controller output _u1 , if it is positive, then the target leveling output force F ₃ of the third hydraulic cylinder 8 = d kN, and the target leveling output force of the first leveling hydraulic cylinder 6 Leveling output force F ₁ =F ₃ +u ₁ , otherwise, the first hydraulic cylinder 6 will give the target leveling output force F ₁ =d kN, and the target leveling output force of the third leveling hydraulic cylinder 6 will be F ₃ =F ₁ -u ₁ ; Among the target leveling output forces of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9, there is always a target leveling force of d kN, and the target leveling force of the diagonal leveling hydraulic cylinder is The output force is judged by the positive or negative of the designed controller output u ₂ , if it is positive, the fourth hydraulic cylinder 9 will give the target leveling output force F ₄ =d kN, and the target leveling of the second leveling hydraulic cylinder 7 Output force F ₂ =F ₄ +u ₁ , otherwise, the second hydraulic cylinder 7 gives the target leveling output force F ₂ =d kN, and the target leveling output force of the fourth leveling hydraulic cylinder 9 is F ₄ =F ₂ - u ₂ . The target leveling forces F ₁ , F ₂ , F ₃ , and F ₄ of the four leveling hydraulic cylinders act on the slider to realize the horizontal control of the slider.

Fig. 3 schematically represents the operation flowchart of the torque leveling control method for a composite material press.

The specific flow chart is as follows:

Step 1: First, by judging whether the slider 2 has reached the leveling position, if it has not reached the leveling start position, the first leveling hydraulic cylinder 6, the second leveling hydraulic cylinder 7, the third leveling hydraulic cylinder 8, and the fourth leveling hydraulic cylinder The flat hydraulic cylinder 9 is used for position closed-loop control together with the slide block. When the slider 2 reaches the leveling position, the four leveling hydraulic cylinders output different leveling forces for leveling control.

Step 2: When the slider reaches the leveling position, the system will judge whether the leveling accuracy of each leveling hydraulic cylinder meets the requirements. If the leveling accuracy meets the requirements, that is, each leveling hydraulic cylinder of the four leveling hydraulic cylinders If the difference of shaft displacement is within cmm, the four-corner leveling control system will maintain the original leveling output force and continue to do precise position closed-loop control with the master cylinder down. If the leveling accuracy cannot meet the requirements, the four-corner leveling control system collects the displacement signals of the four leveling hydraulic cylinders through the displacement sensor, and calculates the instantaneous speed of the four leveling hydraulic cylinders by calculating the derivative of the displacement with respect to time, and obtains it through program processing The displacement difference and speed difference of each diagonal cylinder, that is, the displacement difference x ₁ and the speed difference x ₃ of the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8, the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder The displacement difference x ₂ and the speed difference x ₄ of the hydraulic cylinder 9 .

Step 3: Get the displacement difference and velocity difference of each diagonal leveling hydraulic cylinder as the input of the sliding mode variable structure control algorithm, and calculate the target leveling output force difference of each diagonal leveling hydraulic cylinder, which is the first The difference u ₁ between the target leveling output force of the first leveling hydraulic cylinder 6 and the target leveling output force of the third leveling hydraulic cylinder 8 , the target leveling output force of the second leveling hydraulic cylinder 7 and the target leveling output force of the fourth leveling hydraulic cylinder 9 Leveling output force difference u ₂ .

Step 4: From the difference in the target leveling output force of each diagonal leveling hydraulic cylinder obtained in step 3, the target leveling output force of each leveling hydraulic cylinder can be obtained from the four-cylinder leveling force distribution algorithm, that is, the first leveling Hydraulic cylinder 6 target leveling output force F ₁ , second leveling hydraulic cylinder 7 target leveling output force F ₂ , third leveling hydraulic cylinder 8 target leveling output force F ₃ , fourth leveling hydraulic cylinder 9 target leveling output force The horizontal output force F ₄ acts on the level control of the slider 2 to improve the stability and response speed of the leveling process.

Step 5: Determine whether the leveling end position has been reached, if not, repeat the process from step 2 to step 4. Otherwise, the leveling ends.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related technologies fields, all of which are equally included in the scope of patent protection of the present invention.

Claims (9)

1. The method is used for the torque leveling control method of the composite material press, and the leveling hydraulic cylinders are vertically arranged under the four corners of the slider (2); it is characterized in that: it includes the following steps in order: Step 1: Create a virtual axis, and four leveling hydraulic cylinders respectively track the virtual axis; Step 2: At the beginning of leveling, collect the displacement values of the four leveling hydraulic cylinders; Step 3: Process the displacement signal to obtain the displacement difference and speed difference of the diagonal leveling hydraulic cylinder; Step 4: Establish the mathematical model of the slider (2) through the torque balance equation of the slider (2), the geometric relationship between the four leveling hydraulic cylinders, and the kinematic equations and convert it into a state space equation, and then combine the virtual Shaft, design the sliding mode variable structure control algorithm, use the displacement difference and velocity difference in step 3 as the input of the sliding mode variable structure control algorithm, and obtain the target leveling force difference of the diagonally leveling hydraulic cylinder; Step 5: Obtain the target output forces of the four leveling hydraulic cylinders respectively according to the optimal force distribution algorithm; Step 6: Repeat the process from step 3 to step 5, and adjust the slider (2) m times until the requirement of horizontal precision is met. 2. The torque leveling control method for a composite material press according to claim 1, wherein the virtual axis is an average value of displacements of four leveling hydraulic cylinders. 3. The moment leveling control method for a composite material press according to claim 2, characterized in that: a judgment program is set in step 6, that is, the difference between each leveling hydraulic cylinder and the displacement of the virtual axis When it is within a certain range, the automatic leveling ends. 4. the moment leveling control method that is used for composite material press according to claim 3, is characterized in that: the design of sliding mode variable structure control system comprises the design of sliding mode surface and the design of sliding mode variable structure control law; The optimal sliding mode surface is s ₁ =x ₁ +a·x ₃ , s ₂ =x ₂ +b·x ₄ , where the values of a and b determine the convergence rate of s ₁ and s ₂ ; s ₁ : Sliding surface 1; s ₂ : Sliding surface 2; a: Convergence coefficient of sliding surface 1; b: Convergence coefficient of sliding surface 1; x ₁ : The first leveling hydraulic cylinder (6) and the third leveling The displacement difference of the hydraulic cylinder (8); x ₂ : the displacement difference between the second leveling hydraulic cylinder (7) and the fourth leveling hydraulic cylinder (9); x ₃ : the first leveling hydraulic cylinder (6) and the third The speed difference of the leveling hydraulic cylinder (8); x ₄ : the speed difference of the second leveling hydraulic cylinder (7) and the fourth leveling hydraulic cylinder (9); the improved reaching law of the sliding mode variable structure control law for

Among them, the values of k ₁ and k ₂ determine the degree of approaching the sliding mode surface; k ₁ : reaching law coefficient; k ₂ : reaching law coefficient; s _(t) : sliding mode surface. 5. The torque leveling control method for a composite material press according to any one of claims 1 to 4, characterized in that: the process of the optimal force distribution algorithm described in step 5 is: diagonal leveling Among the target leveling output forces of the hydraulic cylinders, there is always a target leveling output force d, the target leveling output force of the leveling hydraulic cylinder with the smaller target output force is d, and the leveling hydraulic cylinder with the larger target output force The target leveling output force of is the sum of the difference between d and the target output leveling force of the diagonal leveling hydraulic cylinder. 6. The torque leveling control method for a composite material press according to claim 5, wherein it is characterized in that: before step 2, it is judged whether the slider (2) has reached the leveling position, if it has not reached the leveling start position, The four leveling hydraulic cylinders and the slider (2) perform position closed-loop control; until the slider (2) reaches the leveling position, the four leveling hydraulic cylinders perform leveling control by outputting different leveling forces. 7. The moment leveling control method for a composite material press according to claim 6, characterized in that: the four leveling hydraulic cylinders track the virtual axis in such a way that the four leveling hydraulic cylinders are displaced from the virtual axis The variance tends to be smaller, that is, the displacement difference of the diagonal leveling hydraulic cylinder quickly converges to zero. 8. A leveling device for a composite material press, characterized in that it includes a master cylinder (1) arranged sequentially from top to bottom, a slide block (2) for installing a mold, a return cylinder (3) and a controller ( 5); the hydraulic rod of the master cylinder (1) comprising the first master cylinder is fixed on the upper surface of the slider (2), and the hydraulic rod of the return cylinder (3) is fixed on the lower surface of the slider (2); The four corners below the slider (2) are respectively provided with leveling hydraulic cylinders; the leveling mechanism also includes a first displacement sensor (11) for collecting the displacement signal of the master cylinder (1), and a first displacement sensor (11) for collecting the pressure signal of the return cylinder (3). A pressure sensor (31) and a second displacement sensor (41) for collecting displacement signals of the leveling hydraulic cylinder; the controller (5) includes a data acquisition module (51), a data processing module (52), Data output module (53) and control module (54); The signals of the first displacement sensor (11), the first pressure sensor (31) and the second displacement sensor (41) are collected by the data acquisition module (51) and then transmitted to the data The processing module (52) processes and obtains the target output force of the leveling hydraulic cylinder, and the target output force signal is transmitted to the control module (54) through the data output module (53); the control module (54) adjusts the output force of the leveling hydraulic cylinder according to the target output force. output force; The data processing module (52) establishes the mathematical model of the slider through the moment balance equation of the slider, the geometric relationship between the four leveling hydraulic cylinders and the kinematic equation and converts it into a state space equation, and then combines the virtual Axis, design sliding mode variable structure control algorithm, displacement difference and speed difference are used as the input of sliding mode variable structure control algorithm to obtain the target leveling force difference of the diagonal leveling hydraulic cylinder, according to the optimal force distribution algorithm, respectively obtain four The target output force of each leveling hydraulic cylinder. 9. A kind of composite material press leveling device as claimed in claim 8, is characterized in that: described data processing module (52) comprises data storage module (521), and the state space equation of slide block (2) carries out A comparison module (522) for comparison and a calculation module (523) for calculating the output leveling force of the leveling hydraulic cylinder.

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