CN107263890B - Moment leveling control method and leveling device for composite material press - Google Patents
Moment leveling control method and leveling device for composite material press Download PDFInfo
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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
Technical Field
The invention relates to a passive moment leveling control method, in particular to a moment leveling control method and a leveling device for a composite material press.
Background
The composite material press is one of important equipment for manufacturing novel composite material products, has the advantages of strong automation degree, simple process technology, high forming precision and good forming quality, can realize one-step forming and continuous pressing, and is widely applied to the high and new technical fields of airplanes, spaceflight, submarines, automobiles and the like. However, in the process of press forming by a hydraulic press, due to uneven pressure distribution of the main cylinder and the return cylinder and the difference between the shape and the temperature of the composite material product, the system has strong unbalance loading characteristics, for example, unbalance loading caused by the unbalance causes the slide block to incline, thereby affecting the precision of the composite material product and even damaging the die.
In order to ensure the precision of products and protect the die, the influence of the overturning moment caused by a main cylinder, a return cylinder and a composite material on the whole press system is considered, and the most common means at present is to design a four-corner leveling system to balance the overturning moment. The design and improvement of the device are composed of the following two aspects: on the one hand, the hydraulic system and on the other hand, the control algorithm. (1) hydraulic system aspect: fast level control of the slider is achieved by active leveling or passive leveling (refer to patents 200910070144.3, 201010243672.7, 201110183255.2); (2) In the aspect of algorithm optimization, synchronous position control is carried out by adopting different control strategies (refer to patents 200910190950.4, 201110182802.5 and 201210374508.9); or combining an MIMO follow-up fuzzy control method with a surface leveling method to realize multi-point decoupling automatic leveling (refer to patent 200810055292.3); or the high-precision control is realized by adopting a control algorithm of a leveling and speed-regulating double closed loop (refer to patent 201110278650.9). The prior patent designs are beneficial to balancing the application requirements of the unbalance loading characteristics of the system, but still have the following defects, which are mainly expressed as follows:
(1) In the aspect of an existing hydraulic system, although the consumed energy of an active leveling mode is small, the active leveling mode is complex to install and difficult to control in the high-speed leveling process. Although the passive leveling system is simple to install, the passive leveling system has a blocking effect on the movement of the sliding block, so that the leveling efficiency of the system is not high.
(2) Most of the existing leveling control methods adopt the average value of the displacements of four leveling hydraulic cylinders as a virtual shaft, and the four leveling hydraulic cylinders follow the virtual shaft to realize that the four leveling hydraulic cylinders level a sliding block.
(3) In the aspect of algorithm improvement, the existing leveling control method carries out leveling control through a synchronous position PID control algorithm of each leveling hydraulic cylinder tracking virtual shaft. Due to the fact that the system has the characteristics of a multi-input multi-output system, a coupling system and an overdrive system, control parameters of the PID controller are difficult to adjust, and the requirement of high precision under the working condition of fast leveling is difficult to guarantee. For some improved algorithms, although the system characteristics are considered in the design of the controller, the leveling requirements of the system can be met, but the control algorithm is complex and is difficult to apply to engineering practice.
Disclosure of Invention
In order to solve the technical problems, the invention provides a moment leveling control method and a leveling device for a composite material press, which aim to solve the problems of low leveling efficiency, low leveling precision, low anti-interference capability and the like in a high-speed leveling system. 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.
The technical scheme of the invention is as follows:
a moment leveling control method for a composite material press is characterized in that leveling hydraulic cylinders are respectively and vertically arranged below four corners of a sliding block; comprises the following steps which are carried out in sequence:
step 1: when leveling starts, displacement values of four leveling hydraulic cylinders are respectively collected;
and 2, step: processing the displacement signal to obtain a displacement difference and a speed difference of the diagonal leveling hydraulic cylinder;
and step 3: taking the displacement difference and the speed difference in the step 2 as the input of a sliding mode variable structure control algorithm to obtain the difference of target leveling forces of the diagonal leveling hydraulic cylinder;
and 4, step 4: respectively obtaining target output forces of the four leveling hydraulic cylinders according to an optimal force distribution algorithm;
and 5: and (5) repeating the processes from the step (2) to the step (4), and adjusting the sliding block for m times until the requirement of horizontal precision is met.
Firstly creating a virtual shaft before step 1, wherein the virtual shaft is an average value of displacements of the four leveling hydraulic cylinders; the four leveling hydraulic cylinders respectively track the virtual shafts.
And 5, setting a judgment program, namely when the displacement difference between each leveling hydraulic cylinder and the virtual shaft is within a certain range, finishing automatic leveling.
In the step 3, a mathematical model of the sliding block is established through a moment balance equation of the sliding block, a geometric relation among the four leveling hydraulic cylinders and a kinematic equation, the mathematical model is converted into a state space equation, and then the sliding mode variable structure control algorithm is designed by combining a virtual shaft.
The design of the sliding mode variable structure control system comprises the design of a sliding mode surface and the design of a sliding mode variable structure control law.
Wherein the optimal slip form surface is s 1 ＝x 1 +a·x 3 、s 2 ＝x 2 +b·x 4 Wherein the values of a and b determine s 1 And s 2 The convergence rate of (c);
s 1 : a slip form surface 1;
s 2 : a slip form surface 2;
a: the convergence factor of slip form face 1;
b: the convergence factor of slip form face 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 : first leveling hydraulic cylinder and third levelingThe speed difference of the hydraulic cylinders;
x 4 : and the speed difference of the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder.
Wherein, the improved approximation law of the sliding mode variable structure control law is
Wherein k is 1 、k 2 The value of (a) determines the degree of approaching the sliding mode surface;
k 1 : an approximation law coefficient; k is a radical of 2 : an approximation law coefficient; s is (t) : a slip form surface.
The optimal force distribution algorithm in the step 4 comprises the following processes: the target leveling output force of the diagonal leveling hydraulic cylinder is d, the target leveling output force d of the leveling hydraulic cylinder with smaller target output force is always the sum of the difference between d and the target output leveling force of the diagonal leveling hydraulic cylinder.
Before the step 1, judging whether the sliding block reaches a leveling position, if not, performing position closed-loop control on the four leveling hydraulic cylinders and the sliding block together; and when the sliding block reaches the leveling position, the four leveling hydraulic cylinders output different leveling forces for leveling control.
The mode that the four leveling hydraulic cylinders track the virtual shaft is that the variance of the displacement of the four leveling hydraulic cylinders and the virtual shaft is reduced, namely the displacement difference of the diagonal leveling hydraulic cylinders is converged to zero rapidly.
The invention has the following beneficial effects:
1. according to the sliding mode variable structure control method based on the hyperbolic secant function improved approach law, the sliding block is subjected to horizontal control, the situation that a leveling system has large impact and vibration on the movement of the sliding block in leveling control is effectively avoided, and meanwhile the response speed and the leveling precision of the system are improved. In the design process of the sliding mode variable structure control system, a mathematical model is established based on a sliding block system and is converted into a state space equation. The decoupling matrix transformation is carried out on the multi-input multi-output system, so that a decoupling model is obtained, then the optimal sliding mode surface design is carried out by combining the optimal control, so that the system has a good inhibition effect on parameter perturbation and system interference, meanwhile, the traditional approach law is improved, the approach law based on the hyperbolic secant function improvement is designed, the system buffeting can be weakened, the adaptability of the algorithm is enhanced, the slider can be subjected to horizontal control at a high response speed, the unknown interference and the parameter perturbation can be well inhibited, and the robustness of the system is improved.
2. The invention adopts the mode of taking the displacement difference and the speed difference of each leveling hydraulic cylinder as the input of the controller, effectively avoids directly measuring the inclination angle of the sliding block around the x axis and the inclination angle around the y axis by the inclination angle sensor, and simplifies the mechanical structure for installing the inclination angle sensor. The difference of the leveling output forces of the hydraulic cylinders at each angle acts on the sliding block, so that the sliding block is subjected to horizontal control, and the influence of the steady-state error of the leveling output force of each leveling hydraulic cylinder on the horizontal control of the sliding block is effectively avoided. In particular, in the process of high-speed leveling, the pressure control of the leveling hydraulic cylinder cannot realize accurate pressure closed-loop control due to the influence of characteristics such as dead zone, hysteresis, leakage and the like of a system, if the diagonal cylinders have the same steady-state error at the same time, the actual control input is not changed, the higher leveling precision can still be achieved, and the system adaptability is improved.
3. The invention adopts the pressure control method of four leveling hydraulic cylinders, and the pressure control response speed is high, thereby improving the response speed of the system. Meanwhile, the moment leveling method is combined with the optimal force distribution principle, so that the overdrive problem of four-corner leveling is effectively solved, the target output leveling force of each leveling hydraulic cylinder can be optimized, the larger impact and vibration of the system are avoided, and the service life of the press is prolonged.
Drawings
FIG. 1 is a schematic view of a leveling device of the present invention;
FIG. 2 is a schematic diagram of a design method of a sliding mode variable structure control system according to the present invention;
FIG. 3 is a flow chart of the operation of the torque leveling control method for the composite press of the present invention;
fig. 4 is a schematic diagram of the controller and sensors of the present invention.
The reference numbers in the figures denote:
the leveling device comprises a main cylinder 1, a first displacement sensor 11, a sliding block 2, a return cylinder 3, a first pressure sensor 31, a second displacement sensor 41, a second pressure sensor 42, a controller 5, a data acquisition module 51, a data processing module 52, a data storage module 521, a comparison module 522, a calculation module 523, a data output module 53, a regulation module 54, a first leveling hydraulic cylinder 6, a second leveling hydraulic cylinder 7, a third leveling hydraulic cylinder 8 and a fourth leveling hydraulic cylinder 9.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
Fig. 1 and 4 represent a leveling device of a composite material press, which comprises a main cylinder 1, a slide block 2 for installing a die, a return cylinder 3 and a controller 5 which are arranged from top to bottom in sequence; the hydraulic rod of the main cylinder 1 is fixed on the upper end surface of the sliding block 2, and the hydraulic rod of the return cylinder 3 is fixed on the lower end surface of the sliding block 2; leveling hydraulic cylinders are respectively arranged at four corners below the sliding block 2; the leveling mechanism further comprises a first displacement sensor 11 for acquiring a displacement signal of the main cylinder 1, a first pressure sensor 31 for acquiring a pressure signal of the return cylinder 3 and a second displacement sensor 41 for acquiring a displacement signal of the leveling hydraulic cylinder; the controller 5 comprises a data acquisition module 51, a data processing module 52, a data output module 53 and a regulation and control module 54 which are sequentially connected by electric signals; signals of the first displacement sensor 11, the first pressure sensor 31 and the second displacement sensor 41 are acquired by the data acquisition module 51 and then transmitted to the data processing module 52 for processing to obtain a target output force of the leveling hydraulic cylinder, and the target output force signal is transmitted to the regulation and control module 54 by the data output module 53; the regulation module 54 regulates the output force of the leveling cylinder based on the target output force.
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.
The leveling hydraulic cylinder is a double-acting single-rod cavity type hydraulic cylinder.
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 each leveling hydraulic cylinder; the second pressure sensor 42 is in electrical signal connection with the data acquisition module 51.
The specific flow chart is as follows:
step 1: the controller 5 adjusts the pressure of the main cylinder 1 and the return cylinder 3 according to the signals of the first displacement sensor 11 and the first pressure sensor 31, judges whether the slide block 2 reaches a leveling position, and if the slide block does not reach the leveling start position, the first leveling hydraulic cylinder 6, the second leveling hydraulic cylinder 7, the third leveling hydraulic cylinder 8, the fourth leveling hydraulic cylinder 9 and the slide block perform position closed-loop control together. When the sliding block 2 reaches the leveling position, the four leveling hydraulic cylinders output different leveling forces for leveling control.
Step 2: when the sliding block reaches the leveling position, the system can compare and judge whether the leveling precision of each leveling hydraulic cylinder meets the requirement through the comparison module 522, if the leveling precision meets the requirement, namely the displacement difference between each leveling hydraulic cylinder and the virtual shaft in the four leveling hydraulic cylinders is within c mm, the four-corner leveling control system can keep the original leveling output force to continue to perform accurate position closed-loop control together with the main cylinder downwards. If the leveling precision can not meet the requirement, the four-corner leveling control system collects displacement signals of the four leveling hydraulic cylinders through the second displacement sensor 41 and inputs the displacement signals into the calculation module 523 for calculation.
And step 3: the calculation process of the calculation module 523 is as follows; calculating to obtain the instantaneous speeds of the four leveling hydraulic cylinders by derivation of displacement to time, and obtaining the displacement difference and the speed difference of each diagonal cylinder by program processing, namely the displacement difference x between the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8 1 Sum velocity difference x 3 And the displacement difference x of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9 2 Sum velocity difference x 4 (ii) a Obtaining the displacement difference and the speed difference of each diagonal leveling hydraulic cylinder as the input of a sliding mode variable structure control algorithm, and calculating to obtain the difference of the target leveling output forces of each required diagonal leveling hydraulic cylinder, namely the first diagonal leveling hydraulic cylinderDifference u between target leveling output force of the leveling hydraulic cylinder 6 and target leveling output force of the third leveling hydraulic cylinder 8 1 The difference u 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 2 。
And 4, step 4: the target leveling output force of each leveling hydraulic cylinder can be obtained by the four-cylinder leveling force distribution algorithm according to the target leveling output force difference of each diagonal leveling hydraulic cylinder obtained in the step 3, namely the target leveling output force F of the first leveling hydraulic cylinder 6 1 A second leveling hydraulic cylinder 7 target leveling output force F 2 And a third leveling hydraulic cylinder 8 target leveling output force F 3 And a fourth leveling hydraulic cylinder 9 target leveling output force F 4 And the leveling control device acts on the horizontal control of the sliding block 2 to improve the stability and response speed of the leveling process.
And 5: and (4) judging whether the leveling end bit is reached, and if not, repeating the process from the step (2) to the step (4). Otherwise, leveling is finished.
Fig. 2 represents a design method of a sliding mode variable structure control system of a multi-input multi-output passive leveling system.
The specific design method is as follows:
step 1: the slider is first modeled mathematically,
the tilt angles with the x-axis and the y-axis respectively; f 1 、F 2 、F 3 、F 4 The leveling forces are respectively output for the targets of the four leveling hydraulic cylinders; j. the design is a square x 、J y The rotational inertia of the slide block around the x axis and the y axis respectively; f p Is unknown offset load; the distance between the four leveling hydraulic cylinders and the x axis is l x (ii) a Distance l from y-axis y (ii) a The distance from the offset load force to the x-axis is r x (ii) a The distance from the offset force to the y-axis is r y . According to the fixed-axis rotation rule of the rigid body, the method can be obtained as follows:
according to the geometrical relationship of the four leveling hydraulic cylinders, the following can be obtained:
the combined type (1) and the formula (2) can eliminate
And &>
The speed and displacement of the four leveling hydraulic cylinders can be used for describing the inclination angle error of the slide block around the x axis and the y axis. Combining kinematic equations can result in:
y i respectively the displacement of the No. i leveling hydraulic cylinder; v. of i The speed of the No. i leveling hydraulic cylinder is respectively;
the mathematical models can be obtained by simultaneous connection of the formula (1), the formula (2) and the formula (3), and are converted into a state space equation which takes the displacement difference and the speed difference of the diagonal leveling hydraulic cylinder as state variables and the difference of the target leveling output force of the diagonal leveling hydraulic cylinder as output;
step 2: and (3) designing a sliding mode variable structure control algorithm based on the state space equation designed in the step (1). The design of the sliding mode variable structure control system is divided into two parts: one part is designed as a sliding mode surface, and the other part is designed as a sliding mode variable structure control law. The specific design process is as follows:
step 1: because the system has the characteristics of a multi-input multi-output system, firstly, decoupling operation, namely matrix transformation, needs to be carried out on a state space equation to obtain a corresponding decoupling model. Based on a decoupled model, an optimal sliding mode surface is designed by combining an optimal control principle, so that the determined sliding mode is gradually 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 Wherein the values of a and b determine s 1 And s 2 The convergence rate of (c);
s 1 : a slip form surface 1;
s 2 : a slip form surface 2;
a: the convergence factor of slip form face 1;
b: the convergence factor of slip form face 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 : and the speed difference of the second leveling hydraulic cylinder and the fourth leveling hydraulic cylinder.
Step 2: after designing the corresponding optimal sliding mode surface, the control law of the sliding mode variable structure control algorithm needs to be designed, namely how to select the sliding mode control law u + And u - And satisfying the reaching condition so as to form a sliding mode area on the switching surface. In order to ensure that the system state can approach to the sliding mode switching surface in a better motion state, a sliding mode variable structure control rule based on a hyperbolic secant function improved approach law is designed. The improved approach law is
Wherein k is 1 、k 2 The value of (a) determines the degree of approaching the sliding mode surface;
k 1 : an approximation law coefficient; k is a radical of 2 : an approximation law coefficient; s (t) : a slip form surface.
And 3, step 3: aiming at the sliding mode control algorithm designed in the step 2 and based on the hyperbolic secant function improved approach law, the displacement difference and the speed difference of the four leveling hydraulic cylinders are used as controller input, namely 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 first leveling hydraulic cylinder 6 and the third levelingDifference u between output target leveling forces of hydraulic cylinder 8 1 And the difference u between the target output leveling forces of the second leveling cylinder 7 and the fourth leveling cylinder 9 2 I.e. u 1 ＝F 1 -F 3 、u 2 ＝F 2 -F 4 。
And 4, step 4: from the step 3, the difference u between the leveling output force of the first leveling hydraulic cylinder 6 and the leveling output force of the third leveling hydraulic cylinder 8 is obtained 1 The difference u between the leveling output force of the second leveling hydraulic cylinder 7 and the target leveling output force of the fourth leveling hydraulic cylinder 9 2 . Through an optimal distribution algorithm, one target leveling output force is always d kN out of the target leveling output forces of the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8, and the target leveling output force of the diagonal leveling hydraulic cylinder is output u through a designed controller 1 Positive or negative, if positive, the target leveling output force F of the third hydraulic cylinder 8 3 = d kN, target leveling output force F of the first leveling hydraulic cylinder 6 1 ＝F 3 +u 1 On the contrary, the first hydraulic cylinder 6 outputs force F to the target leveling 1 = d kN, target leveling output force F of the third leveling hydraulic cylinder 6 3 ＝F 1 -u 1 (ii) a One target leveling force is d kN all the time among the target leveling output forces of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9, and the target leveling output force of the diagonal leveling hydraulic cylinder is output u through the designed controller 2 Positive or negative, if positive, the fourth hydraulic cylinder 9 gives the target leveling output force F 4 = d kN, target leveling output force F of the second leveling hydraulic cylinder 7 2 ＝F 4 +u 1 On the contrary, the second hydraulic cylinder 7 outputs a force F to the target leveling 2 = d kN, target leveling output force F of the fourth leveling hydraulic cylinder 9 4 ＝F 2 -u 2 . The target leveling force F of the four leveling hydraulic cylinders 1 、F 2 、F 3 、F 4 Acting on the sliding block to realize the horizontal control of the sliding block.
FIG. 3 schematically represents an operational flow diagram of a torque leveling control method for a composite press.
The specific flow chart is as follows:
step 1: firstly, whether the sliding block 2 reaches a leveling position is judged, and if the sliding block does not reach the leveling start position, the first leveling hydraulic cylinder 6, the second leveling hydraulic cylinder 7, the third leveling hydraulic cylinder 8, the fourth leveling hydraulic cylinder 9 and the sliding block perform position closed-loop control together. When the slide block 2 reaches the leveling position, the four leveling hydraulic cylinders perform leveling control by outputting different leveling forces.
Step 2: when the sliding block reaches the leveling position, the system can judge whether the leveling precision of each leveling hydraulic cylinder meets the requirement, if the leveling precision meets the requirement, namely the displacement difference between each leveling hydraulic cylinder and the virtual shaft in the four leveling hydraulic cylinders is within c mm, and the four-corner leveling control system can keep the original leveling output force to continue to perform accurate position closed-loop control together with the main cylinder. If the leveling precision can not meet the requirement, the four-corner leveling control system acquires displacement signals of the four leveling hydraulic cylinders through the displacement sensors, obtains instantaneous speeds of the four leveling hydraulic cylinders through the derivation calculation of displacement to time, and obtains the displacement difference and the speed difference of each diagonal cylinder through program processing, namely the displacement difference x between the first leveling hydraulic cylinder 6 and the third leveling hydraulic cylinder 8 1 Sum speed difference x 3 And the displacement difference x of the second leveling hydraulic cylinder 7 and the fourth leveling hydraulic cylinder 9 2 Sum velocity difference x 4 。
And step 3: obtaining the displacement difference and the speed difference of each diagonal leveling hydraulic cylinder as the input of a sliding mode variable structure control algorithm, and calculating to obtain the difference between the target leveling output forces of the required diagonal leveling hydraulic cylinders, namely the difference u 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 1 The difference u 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 2 。
And 4, step 4: the target leveling output force of each leveling hydraulic cylinder can be obtained by the four-cylinder leveling force distribution algorithm according to the target leveling output force difference of each diagonal leveling hydraulic cylinder obtained in the step 3, namely the target leveling output force F of the first leveling hydraulic cylinder 6 1 A second leveling hydraulic cylinder 7 target leveling output force F 2 Third leveling hydraulic cylinder 8 target leveling output force F 3 And a fourth leveling hydraulic cylinder 9 target leveling output force F 4 And the leveling control device acts on the horizontal control of the sliding block 2 to improve the stability and response speed of the leveling process.
And 5: and (4) judging whether the leveling end bit is reached, and if not, repeating the process from the step (2) to the step (4). Otherwise, leveling is finished.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A moment leveling control method for a composite material press is characterized in that leveling hydraulic cylinders are respectively and vertically arranged below four corners of a sliding block (2); the method is characterized in that: comprises the following steps which are carried out in sequence:
step 1: creating a virtual shaft, and respectively tracking the virtual shaft by four leveling hydraulic cylinders;
step 2: when leveling starts, displacement values of four leveling hydraulic cylinders are respectively collected;
and step 3: processing the displacement signal to obtain a displacement difference and a speed difference of the diagonal leveling hydraulic cylinder;
and 4, step 4: establishing a mathematical model of the sliding block (2) through a moment balance equation of the sliding block (2), a geometric relation among the four leveling hydraulic cylinders and a kinematic equation, converting the mathematical model into a state space equation, designing a sliding mode variable structure control algorithm by combining a virtual shaft, and taking the displacement difference and the speed difference in the step 3 as the input of the sliding mode variable structure control algorithm to obtain the difference of target leveling forces of the diagonal leveling hydraulic cylinders;
and 5: respectively obtaining target output forces of the four leveling hydraulic cylinders according to an optimal force distribution algorithm;
and 6: and (5) repeating the process from the step (3) to the step (5), and adjusting the sliding block (2) for m times until the requirement of horizontal precision is met.
2. The torque leveling control method for a composite press of claim 1, wherein: the virtual axis is the average value of the displacements of the four leveling hydraulic cylinders.
3. The torque leveling control method for a composite press of claim 2, wherein: and 6, setting a judgment program, namely when the displacement difference between each leveling hydraulic cylinder and the virtual shaft is within a certain range, finishing the automatic leveling.
4. The torque leveling control method for a composite press of claim 3, wherein: the design of the sliding mode variable structure control system comprises the design of a sliding mode surface and the design of a 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 Wherein the values of a and b determine s 1 And s 2 The convergence rate of (c); s 1 : a slip form surface 1; s 2 : a slip form surface 2; a: the convergence factor of slip form face 1; b: the convergence factor of slip form face 1; x is the number of 1 : the displacement difference between the first leveling hydraulic cylinder (6) and the third leveling hydraulic cylinder (8); x is a radical of a fluorine atom 2 : the displacement difference between the second leveling hydraulic cylinder (7) and the fourth leveling hydraulic cylinder (9); x is the number of 3 : the speed difference between the first leveling hydraulic cylinder (6) and the third leveling hydraulic cylinder (8); x is the number of 4 : the speed difference between the second leveling hydraulic cylinder (7) and the fourth leveling hydraulic cylinder (9); the improved approximation law of the sliding mode variable structure control law is
Wherein k is 1 、k 2 The value of (a) determines the degree of approaching the sliding mode surface; k is a radical of formula 1 : an approximation law coefficient; k is a radical of 2 : an approximation law coefficient; s (t) : a slip form surface.
5. The torque leveling control method for a composite press according to any one of claims 1 to 4, wherein: the optimal force distribution algorithm in step 5 comprises the following steps: the target leveling output force of the diagonal leveling hydraulic cylinder is d, the target leveling output force d of the leveling hydraulic cylinder with smaller target output force is always 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 press of claim 5, wherein: before the step 2, judging whether the sliding block (2) reaches a leveling position, if not, performing position closed-loop control on the four leveling hydraulic cylinders and the sliding block (2) together; and when the sliding block (2) reaches the leveling position, the four leveling hydraulic cylinders output different leveling forces for leveling control.
7. The torque leveling control method for a composite press of claim 6, wherein: the mode that the four leveling hydraulic cylinders track the virtual shaft is that the variance of the displacement of the four leveling hydraulic cylinders and the virtual shaft is reduced, namely the displacement difference of the diagonal leveling hydraulic cylinders is converged to zero rapidly.
8. The utility model provides a combined material press levelling device which characterized in that: comprises a main cylinder (1), a slide block (2) for installing a die, a return cylinder (3) and a controller (5) which are arranged from top to bottom in sequence; the main cylinder (1) comprises a hydraulic rod of a first main cylinder fixed on the upper end surface of the sliding block (2), and the hydraulic rod of the return cylinder (3) is fixed on the lower end surface of the sliding block (2); four corners below the sliding block (2) are respectively provided with a leveling hydraulic cylinder; the leveling mechanism further comprises a first displacement sensor (11) for acquiring a displacement signal of the main cylinder (1), a first pressure sensor (31) for acquiring a pressure signal of the return cylinder (3) and a second displacement sensor (41) for acquiring a displacement signal of the leveling hydraulic cylinder; the controller (5) comprises a data acquisition module (51), a data processing module (52), a data output module (53) and a regulation and control module (54) which are sequentially connected by electric signals; signals of the first displacement sensor (11), the first pressure sensor (31) and the second displacement sensor (41) are collected by the data collection module (51), then transmitted to the data processing module (52) to be processed to obtain a target output force of the leveling hydraulic cylinder, and the target output force signal is transmitted to the regulation and control module (54) through the data output module (53); the regulation and control module (54) regulates the output force of the leveling hydraulic cylinder according to the target output force;
the data processing module (52) establishes a mathematical model of the sliding block through a moment balance equation of the sliding block, a geometric relation among the four leveling hydraulic cylinders and a kinematics equation, converts the mathematical model into a state space equation, designs a sliding mode variable structure control algorithm by combining a virtual shaft, obtains a difference between target leveling forces of the diagonal leveling hydraulic cylinders by taking a displacement difference and a speed difference as input of the sliding mode variable structure control algorithm, and respectively obtains target output forces of the four leveling hydraulic cylinders according to an optimal force distribution algorithm.
9. The composite press leveling device of claim 8, wherein: the data processing module (52) comprises a data storage module (521), a comparison module (522) for comparing with a state space equation of the sliding block (2) and a calculation module (523) for calculating the output leveling force of the leveling hydraulic cylinder.
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| CN108958041B (en) * | 2018-08-19 | 2021-04-16 | 台州学院 | Discrete double-period repetitive control method based on hyperbolic secant attraction law |
| CN109986828B (en) * | 2019-05-13 | 2021-03-30 | 福州大学 | Composite press four-corner leveling system for realizing total tonnage control |
| CN110027243B (en) * | 2019-05-13 | 2021-06-08 | 天津市天锻压力机有限公司 | Active leveling electrical control system based on composite material press |
| CN112976667B (en) * | 2021-02-07 | 2022-03-08 | 福州大学 | Control system and method for flexible butt joint of hydraulic press movable beam and leveling system |
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| CN101985151B (en) * | 2010-08-02 | 2012-07-25 | 天津市天锻压力机有限公司 | Bidirectional couple four-corner levelling control system |
| CN202242030U (en) * | 2011-06-30 | 2012-05-30 | 天津市天锻压力机有限公司 | High speed hydraulic press for composite material products |
| CN102500735B (en) * | 2011-09-20 | 2015-05-13 | 天津市天锻压力机有限公司 | Strain rate control and multi-point leveling control method for multi-cylinder hydraulic system |
| CN202239424U (en) * | 2011-09-20 | 2012-05-30 | 天津市天锻压力机有限公司 | Bidirectional couple four-corner leveling control system for forging press sliding block |
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