CN109986828B - Composite press four-corner leveling system for realizing total tonnage control - Google Patents
Composite press four-corner leveling system for realizing total tonnage control Download PDFInfo
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- CN109986828B CN109986828B CN201910394427.7A CN201910394427A CN109986828B CN 109986828 B CN109986828 B CN 109986828B CN 201910394427 A CN201910394427 A CN 201910394427A CN 109986828 B CN109986828 B CN 109986828B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/32—Component parts, details or accessories; Auxiliary operations
- B29C43/58—Measuring, controlling or regulating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/007—Means for maintaining the press table, the press platen or the press ram against tilting or deflection
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/32—Component parts, details or accessories; Auxiliary operations
- B29C43/58—Measuring, controlling or regulating
- B29C2043/5808—Measuring, controlling or regulating pressure or compressing force
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Abstract
The invention provides a four-corner leveling system of a composite material press, which realizes total tonnage control, wherein the output end of the leveling system is a slide block; a plurality of leveling units are uniformly arranged on the periphery of the sliding block; the leveling unit is connected with the control unit; each leveling unit comprises a leveling cylinder, an information acquisition element and a servo valve connected with the leveling cylinder; the leveling cylinder rod is contacted with the sliding block in the leveling process, and the control unit synchronously controls the position and the output force of each leveling cylinder rod through the servo valve so as to level the sliding block; the invention can carry out closed-loop distribution and single-cylinder pressure accurate control on four basic pressures of the leveling system, and realizes effective control on the total output force of the leveling system and the levelness of the sliding block.
Description
Technical Field
The invention relates to the technical field of composite material production equipment, in particular to a four-corner leveling system of a composite material press, which realizes total tonnage control.
Background
The composite press is the most important equipment in the compression molding process, and the performance of the composite press directly determines the quality of the composite product. In the actual production process, the press is limited by the structure of the press, the working table surface of the press has the phenomena of uneven stress and uneven heating, and simultaneously, due to factors such as the geometric shapes and the temperature differences of all parts of the composite material product, the slide block is often influenced by the action of an offset load to generate overturning moment, so that the slide block inclines in different degrees, and the manufacturing precision of a molded part and the abrasion degree of a die are influenced. With the remarkable improvement of the precision requirement of composite material products, a multi-shaft leveling system is developed at the same time and is an important component of a high-end composite material press.
In order to meet the precision requirement of the actual processing technology, a synchronous leveling system is required to be arranged to reduce or even eliminate the inclination of the sliding block, so that the sliding block falls down in parallel, and the accurate opening and closing of the die are ensured, thereby improving the precision of products and prolonging the service life of the die to a certain extent. The current synchronous leveling systems can be divided into two main categories from the principle point of view: 1) the active leveling continues the traditional design idea, a closed synchronous compensation system is arranged independently of a main system, a leveling cylinder and a main cylinder fall together, and leveling control is carried out in the whole process, so that high synchronous precision can be obtained, but the active leveling is not suitable for high-speed occasions, and the production efficiency is low; 2) the leveling cylinders for passive leveling are arranged at four corners below the sliding block, and when the sliding block contacts with the leveling cylinders, the leveling is started, and the leveling is realized by preventing the corners of the sliding block from falling, so that the pressing tonnage of the main cylinder can be influenced, but the leveling moment is large, the production efficiency is high, and the composite material compression molding process is more suitable for high-speed and rapid pressing.
The control aspect of the synchronous leveling system relates to multi-cylinder position synchronous control and leveling force control, most of the prior systems only focus on the position synchronous control, adjust the opening of a proportional valve or a servo valve according to the difference between the displacement of each cylinder and the target displacement, ensure that a sliding block falls down in a horizontal posture, neglect the control of the leveling force, and have poor anti-interference performance. In addition, some systems can realize multi-cylinder position synchronous control and simultaneously consider leveling force control, convert displacement errors into equivalent force deviation values and realize leveling control through the force control of each cylinder. The total leveling force can be roughly determined according to the given reference leveling force, but the accurate control of the total leveling force cannot be realized, and when the offset load of the system is large, the equivalent force deviation value is also large, so that the final actual total leveling force is greatly different from the expected value. Although the existing leveling system can realize leveling moment control and slider parallel attitude control, the following defects exist:
(1) the main cylinder needs to be correspondingly adjusted to maintain the original track movement, pressure fluctuation is generated, load interference of the leveling system is caused, and the leveling control result is influenced.
(2) In the leveling process, the leveling cylinder falls along with the sliding block, a certain flow needs to flow out of the control valve, the opening degree of the control valve is determined by the difference between the actual pressure and the target pressure, so that the difference between the actual pressure and the target pressure is inevitably caused, uncertainty exists in the error, the actual pressure is not controllable, the result of position synchronous control is influenced, and the error between the total leveling force and the expected value is further increased.
(3) The output forces of the four cylinders are the same at the initial stage of leveling, no leveling moment is generated, the initial displacement deviation of the sliding block can be increased under the influence of unbalance loading force due to the fact that the limitation of a mechanical structure is released in the leveling process, and if the unbalance loading moment is large, the generated initial displacement deviation can be large, so that the control difficulty of a rear leveling system can be increased, and the abrasion of the main cylinder can be aggravated.
Disclosure of Invention
The invention provides a four-corner leveling system of a composite material press for realizing total tonnage control, which can perform closed-loop distribution and single-cylinder pressure accurate control on four basic pressures of the leveling system, realize effective control on the total output force of the leveling system and ensure the levelness of a slide block.
The invention adopts the following technical scheme.
A four-corner leveling system of a composite material press for realizing total tonnage control is disclosed, wherein the output end of the leveling system is a slide block (1); a plurality of leveling units are uniformly arranged on the periphery of the sliding block; the leveling unit is connected with the control unit (7); each leveling unit comprises a leveling cylinder (4), an information acquisition element and a servo valve (6) connected with the leveling cylinder; the leveling cylinder rod is contacted with the sliding block in the leveling process, and the control unit synchronously controls the position and the output force of each leveling cylinder rod through the servo valve so as to level the sliding block;
the control unit comprises a total tonnage controller (7B), a highest cylinder judgment module (7C) and a plurality of single-cylinder synchronous controllers (7A) corresponding to the leveling units, and the leveling control method comprises the following steps;
a1, the highest cylinder judgment module judges the leveling cylinder with the largest extending cylinder rod as the highest cylinder through the information acquisition element, the displacement of the cylinder rod of the highest cylinder is taken as the maximum displacement value, and the maximum displacement value is sent to a single-cylinder synchronous controller (7A), so that the highest cylinder becomes the tracking target of other leveling cylinders for executing leveling operation;
a2, the total ton controller performs closed-loop control on the total pressure of the rodless cavities of the leveling cylinders, calculates the total resultant force output by the leveling system through acquiring pressure signals of the rodless cavities of the four leveling cylinders in real time, and distributes and corrects the basic pressure of the rodless cavities of the four leveling cylinders through comparing the total resultant force with a target resultant force;
a3, controlling each leveling cylinder by the synchronous controller to target the highest cylinder, and performing single-cylinder position tracking control to realize leveling control; and the rod-free cavity pressure and the cylinder rod position of each leveling cylinder are accurately controlled in the leveling control, so that the total output force of the sliding block is accurately controlled.
Four leveling units are uniformly arranged on the periphery of the driving surface of the sliding block; the total tonnage controller comprises a leveling stage judgment module (7B 1), a target total pressure setting module (7B 2), a correction value calculation module (7B 3), a basic pressure iteration module (7B 4), a basic pressure correction module (7B 5) and a total tonnage control judgment module (7B 6);
in step A2, the total tonnage controller (7B) distributes the rodless chamber base pressure of each leveling cylinder (4) by the following method;
b1, judging the current leveling operation stage by a leveling stage judgment module (7B 1), and controlling a target total pressure setting module (7B 2) to give a target total pressure of the four-cylinder rodless cavity required by the corresponding stage; the added value of the pressure of the rodless cavities of the leveling cylinders is the actual total pressure, and a correction value calculation module (7B 3) calculates a basic pressure correction value according to the difference value of the actual total pressure and the target total pressure;
b2, a basic pressure iteration module (7B 4) gives a group of four-cylinder storage basic pressure according to the current leveling stage, a basic pressure correction module (7B 5) corrects the storage basic pressure of four leveling cylinders according to a basic pressure correction value, and if the storage basic pressure is verified to be feasible by a total tonnage control judgment module (7B 6), the corrected four-cylinder correction basic pressure is used as output; otherwise, a four-cylinder minimum base pressure is output and a command is sent to the base pressure iteration module (7B 4) to cancel the iteration of the pressure data.
The basic pressure iteration module (7B 4) records the pressure condition of the rodless cavity of each leveling cylinder in a leveling stage, and if the pressure is basically unchanged in a period of time, the pressure is considered to be stable, and the pressure is used for correcting the last iteration result.
The synchronous controller comprises a position closed-loop controller (7A 1), a pressure closed-loop controller (7A 2) and a valve port flow compensator (7A 3); the single-cylinder synchronous controller (7A) realizes the position control and the accurate pressure control of each leveling cylinder by the following method;
c1, calculating the difference value between the displacement of the corresponding leveling cylinder and the displacement of the highest cylinder by the position closed-loop controller (7A 1), converting the difference value into a pressure compensation value, and adding the pressure compensation value and the basic pressure value of the rodless cavity of the corresponding leveling cylinder given by the total ton controller (7B) to obtain the target pressure value of the rodless cavity of the leveling cylinder; the pressure closed-loop controller (7A 2) calculates the difference between the actual pressure of the rodless cavity of the corresponding leveling cylinder and the target pressure, and converts the difference into the adjusting voltage of the servo valve (6);
c2, a valve port flow compensator (7A 3) calculates the compensation voltage of the servo valve (6) according to the actual pressure of the rodless cavity of the leveling cylinder (4) and the moving speed of the sliding block, and the flow requirement required by the movement of the leveling cylinder along with the sliding block is met; and adjusting the voltage and the compensation voltage to obtain a final control voltage, and controlling the opening of a servo valve of the leveling cylinder (4) according to a set value to enable the pressure of a rodless cavity of the leveling cylinder to be accurately matched with the target pressure, so that the highest cylinder is tracked by the corresponding leveling cylinder (4).
The leveling stage judging module (7B 1) detects the moving speed of the sliding block (1) towards the material direction, if the speed is lower than a set value, the sliding block of the leveling system is judged to be in contact with the material, the material pressing advancing stage is started, and if the speed is the same as the set value, the sliding block is judged to be in the no-load moving stage.
The total tonnage judgment module (7B 6) judges the feasibility of correcting the base pressure by the four leveling cylinders so as to avoid the sudden increase of the leveling force requirement caused by special conditions, if the corrected base pressure of the four leveling cylinders is more than 0, the corrected base pressure of the four cylinders is taken as output, otherwise, the minimum base pressure of the four cylinders is output.
The valve port flow compensator (7A 3) calculates the servo valve compensation voltage reaching the required flow under the current pressure condition according to a servo valve port flow formula and the characteristic parameters of the used servo valve.
The four leveling cylinders are hydraulic cylinders; the rod cavities of the four leveling cylinders (4) are connected with a constant low-pressure oil source, oil discharge is completed through an overflow valve, and the rodless cavities are connected with the ports A of the corresponding servo valves and the pressure and the flow of the rodless cavities are controlled by the servo valves;
the information acquisition element comprises a speed sensor (2) for detecting the falling speed of the sliding block (1) in the leveling system, a displacement sensor (3) for detecting the displacement information of the cylinder rod of the leveling cylinder (4) and a pressure sensor (5) for detecting the pressure information of the rodless cavity of the leveling cylinder.
The sliding block (1) is controlled by a host hydraulic system so as to keep the sliding block falling at a constant speed in the leveling stage and force the cylinder rod of the leveling cylinder (4) to fall along.
The upper end surface of the sliding block is a driving surface, and the lower end surface of the sliding block is a material pressing surface; the leveling cylinder is fixed on the lower beam of the press and is positioned below four corners of the sliding block, a rod cavity of the leveling cylinder is introduced with a constant low-pressure oil source, and a rodless cavity of the leveling cylinder is connected with an opening A of the servo valve; the port B of the servo valve is sealed, and the port P and the port T are respectively connected with a high-pressure oil source and an oil tank; the control unit is electrically connected with the speed sensor, the displacement sensor, the pressure sensor and the servo valve.
According to the invention, the target position of each cylinder is determined through the judgment of the highest cylinder, the displacement difference value of each cylinder and the highest cylinder is controlled to be 0, and the horizontal control of the sliding block can be realized; meanwhile, the four basic pressures of the leveling system are subjected to closed-loop distribution and single-cylinder pressure accurate control through the total tonnage controller, so that the effective control of the total output force of the leveling system is realized.
The invention has the beneficial effects that:
(1) the total output force of the leveling system to the sliding block is controlled to be a fixed value, the stress of the sliding block is relatively stable, the track control of the upper die and the stability of the pressing force are facilitated, the stability of the sliding block can reduce the load disturbance of the leveling system, and the leveling control result is improved. Meanwhile, the total leveling force is set according to the requirements of each stage, the total leveling force does not need to be kept at the maximum value all the time, the energy consumption of a hydraulic system can be reduced to a certain extent, and a total tonnage control judgment module is arranged to avoid the situation of insufficient leveling force under special conditions.
(2) The valve port flow compensator is arranged, the compensation voltage of the servo valve is calculated according to the current pressure value and the required flow condition, the opening degree of the valve port required by the leveling cylinder to fall along with the sliding block is compensated, the difference value between the actual pressure and the target pressure caused by the difference value is eliminated, and the pressure of the rodless cavity of each leveling cylinder can accurately follow the target pressure, so that the leveling cylinder can accurately execute a leveling control instruction, and meanwhile, the control precision of the total output force of the leveling system is further improved.
The basic pressure iteration module is arranged, and according to the characteristic that certain commonality exists in initial unbalance loading of the same die in the pressing process, initial four-cylinder basic pressure is obtained by iterating pressure data of a rodless cavity of a leveling cylinder in the previous pressing process, so that the system has certain leveling torque at the initial leveling stage, the influence of initial large unbalance loading on the control of the leveling system is reduced, the service life of the main cylinder is prolonged, meanwhile, the deviation of initial total leveling force can be reduced, and the convergence speed of the total leveling force control is accelerated.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a schematic of the present invention;
FIG. 2 is a schematic diagram of the internal structure of a total tonnage controller;
FIG. 3 is a schematic diagram of the internal structure of the synchronous controller;
in the figure: 1-a slide block; 2-a speed sensor; 3-a displacement sensor; 4-leveling cylinder; 5-a pressure sensor; 6-a servo valve; 7-a control unit; 7A-single cylinder synchronous controller; 7a 1-closed loop controller; 7a 2-pressure closed loop controller; 7A 3-valve port flow compensator; 7B-total ton controller; 7B 1-leveling stage judgment module; 7B2 — target Total pressure given module; 7B 3-correction value calculation module; 7B 4-basic pressure iteration module; 7B5 — base pressure correction module; 7B 6-total tonnage control judgment module; 7C-highest cylinder judgment module.
Detailed Description
As shown in fig. 1-3, a four-corner leveling system of a composite material press for realizing total tonnage control, wherein the output end of the leveling system is a slide block 1; a plurality of leveling units are uniformly arranged on the periphery of the sliding block; the leveling unit is connected with the control unit 7; each leveling unit comprises a leveling cylinder 4, an information acquisition element and a servo valve 6 connected with the leveling cylinder; the leveling cylinder rod is contacted with the sliding block in the leveling process, and the control unit synchronously controls the position and the output force of each leveling cylinder rod through the servo valve so as to level the sliding block;
the control unit comprises a total tonnage controller 7B, a highest cylinder judgment module 7C and a plurality of single-cylinder synchronous controllers 7A corresponding to the leveling units, and the leveling control method comprises the following steps;
a1, the highest cylinder judgment module judges the leveling cylinder with the largest extending cylinder rod as the highest cylinder through the information acquisition element, the displacement of the cylinder rod of the highest cylinder is taken as the maximum displacement value, and the maximum displacement value is sent to the single-cylinder synchronous controller 7A, so that the highest cylinder becomes the tracking target of other leveling cylinders for executing leveling operation;
a2, the total ton controller performs closed-loop control on the total pressure of the rodless cavities of the leveling cylinders, calculates the total resultant force output by the leveling system through acquiring pressure signals of the rodless cavities of the four leveling cylinders in real time, and distributes and corrects the basic pressure of the rodless cavities of the four leveling cylinders through comparing the total resultant force with a target resultant force;
a3, controlling each leveling cylinder by the synchronous controller to target the highest cylinder, and performing single-cylinder position tracking control to realize leveling control; and the rod-free cavity pressure and the cylinder rod position of each leveling cylinder are accurately controlled in the leveling control, so that the total output force of the sliding block is accurately controlled.
Four leveling units are uniformly arranged on the periphery of the driving surface of the sliding block; the total tonnage controller comprises a leveling stage judgment module 7B1, a target total pressure setting module 7B2, a correction value calculation module 7B3, a basic pressure iteration module 7B4, a basic pressure correction module 7B5 and a total tonnage control judgment 7B 6;
in step a2, the total ton controller 7B distributes the base pressure of the rodless chamber of each leveling cylinder 4 by the following method;
step B1, judging the stage of the current leveling operation by the leveling stage judging module 7B1, and giving the target total pressure given by the control target total pressure giving module 7B2 to the target total pressure of the four-cylinder rodless cavity required by the corresponding stage; the added value of the rod-free cavity pressures of the leveling cylinders is the actual total pressure, and the correction value calculation module 7B3 calculates the basic pressure correction value according to the difference value between the actual total pressure and the target total pressure;
b2, the basic pressure iteration module 7B4 provides a group of four-cylinder storage basic pressure according to the current leveling stage, the basic pressure correction module 7B5 corrects the storage basic pressure of the four leveling cylinders according to the basic pressure correction value, and if the storage basic pressure is verified to be feasible by the total tonnage control judgment module 7B6, the corrected four-cylinder correction basic pressure is used as output; otherwise, a four-cylinder minimum base pressure is output and a command is sent to the base pressure iteration module 7B4 to cancel the iteration of the pressure data.
The basic pressure iteration module 7B4 records the pressure condition of the rodless cavity of each leveling cylinder in a leveling stage, and if the pressure is basically unchanged in a period of time, the pressure is considered to be stable, and the last iteration result is corrected by the pressure.
The synchronous controller comprises a position closed-loop controller 7A1, a pressure closed-loop controller 7A2 and a valve port flow compensator 7A 3; the single-cylinder synchronous controller 7A realizes the position control and the accurate pressure control of each leveling cylinder by the following method;
c1, calculating the difference value between the displacement of the corresponding leveling cylinder and the displacement of the highest cylinder by the position closed-loop controller 7A1, converting the difference value into a pressure compensation value, and adding the pressure compensation value and the basic pressure value of the rodless cavity of the corresponding leveling cylinder given by the total ton controller 7B to obtain the target value of the pressure of the rodless cavity of the leveling cylinder; the pressure closed-loop controller 7A2 calculates the difference between the actual pressure of the rodless cavity of the corresponding leveling cylinder and the target pressure, and converts the difference into the adjusting voltage of the servo valve 6;
c2 and a valve port flow compensator 7A3 calculate the compensation voltage of the servo valve 6 according to the actual pressure of the rodless cavity of the leveling cylinder 4 and the moving speed of the sliding block, and the flow requirement required by the movement of the leveling cylinder along with the sliding block is met; and adjusting the voltage and the compensation voltage to obtain a final control voltage, and controlling the opening of a servo valve of the leveling cylinder 4 according to a set value to enable the rodless cavity pressure to be accurately matched with the target pressure, so that the highest cylinder is tracked by the corresponding leveling cylinder 4.
The leveling stage judgment module 7B1 detects the moving speed of the slider 1 in the material direction, and if the speed is lower than a set value, judges that the slider of the leveling system has contacted with the material and enters a material pressing advancing stage, and if the speed is the same as the set value, judges that the slider is in an idle moving stage.
The total tonnage judgment module 7B6 judges feasibility of the four leveling cylinders to correct the base pressure to avoid sudden increase of the leveling force requirement caused by special situations, and if the four leveling cylinders correct the base pressure to be greater than 0, the four cylinders correct the base pressure as output, otherwise, the four cylinders minimum base pressure is output.
The valve port flow compensator 7a3 calculates the compensation voltage of the servo valve for achieving the required flow under the current pressure condition according to the valve port flow formula of the servo valve and the characteristic parameters of the servo valve.
The four leveling cylinders are hydraulic cylinders; the rod cavities of the four leveling cylinders 4 are connected with a constant low-pressure oil source, oil discharge is completed through an overflow valve, and the rodless cavities are connected with the ports A of the corresponding servo valves and the pressure and the flow of the rodless cavities are controlled by the servo valves;
the information acquisition element comprises a speed sensor 2 for detecting the falling speed of the sliding block 1 in the leveling system, a displacement sensor 3 for detecting the displacement information of a cylinder rod of the leveling cylinder 4 and a pressure sensor 5 for detecting the pressure information of a rodless cavity of the leveling cylinder.
The sliding block 1 is controlled by a host hydraulic system so as to keep the sliding block falling at a constant speed in the leveling stage and force the cylinder rod of the leveling cylinder 4 to fall along.
The upper end surface of the sliding block is a driving surface, and the lower end surface of the sliding block is a material pressing surface; the leveling cylinder is fixed on the lower beam of the press and is positioned below four corners of the sliding block, a rod cavity of the leveling cylinder is introduced with a constant low-pressure oil source, and a rodless cavity of the leveling cylinder is connected with an opening A of the servo valve; the port B of the servo valve is sealed, and the port P and the port T are respectively connected with a high-pressure oil source and an oil tank; the control unit is electrically connected with the speed sensor, the displacement sensor, the pressure sensor and the servo valve.
Example (b):
fig. 1 shows a four-corner leveling system of a composite press for realizing total tonnage control. The device comprises a slide block 1, a speed sensor 2, a displacement sensor 3, a leveling cylinder 4, a pressure sensor 5, a servo valve 6 and a control unit 7.
Wherein, the slide block is rigidly connected with a main cylinder and a return cylinder (not shown in the figure), and the speed is controlled by a main machine hydraulic system in the pressing process; the speed sensor is rigidly connected with the sliding block and used for detecting the falling speed of the sliding block; the displacement sensor 3, the leveling cylinder 4, the pressure sensor 5 and the servo valve 6 form a group of leveling execution and detection devices, and four groups are provided; the displacement sensor 3 is rigidly connected with a piston rod of the leveling cylinder 4 and is used for detecting the displacement of the leveling cylinder 4; the pressure sensor 5 is connected with the rodless cavity of the leveling cylinder 4 through an oil pipe and is used for detecting the pressure value of the rodless cavity of the leveling cylinder 4; the rod cavity of the leveling cylinder 4 is connected with a low-pressure oil source (not shown in the figure), so that the leveling cylinder 4 has certain back pressure in the descending process, and the hydraulic oil of the leveling cylinder flows out through an overflow valve (not shown in the figure); the rodless cavity of the leveling cylinder 4 is connected with an A port of the servo valve 6, and the oil inlet and outlet conditions of the leveling cylinder are controlled by the servo valve 6, so that the leveling force control is realized; the control unit 7 is electrically connected with the speed sensor 2, the displacement sensor 3, the pressure sensor 5 and the servo valves 6, acquires relevant information in the leveling process, performs calculation processing on the relevant information, outputs control voltages of the four servo valves 6, and enables the leveling cylinders 4 to execute corresponding actions.
The leveling system controller 7 is composed of a total ton controller 7B, a highest cylinder judgment module 7C and a synchronous controller 7A, and performs leveling control according to the following procedures:
the method comprises the following steps: the highest cylinder judgment module 7C determines which of the four leveling cylinders 4 is at the highest position as the tracking target of each cylinder. The module acquires displacement data of the four leveling cylinders 4 in real time, compares the displacement values of the cylinders, determines the maximum displacement value (the displacement sensor takes the upward direction as the forward direction) at the current moment, transmits the maximum displacement value to the four synchronous controllers 7A, and gives a target position to be tracked of each cylinder.
Step two: the total ton controller 7B gives the base pressure of the rodless cavities of the four leveling cylinders 4, and controls the total output force of the leveling system to be a fixed value through continuous correction. The controller obtains the pressure of the rodless cavities of the four leveling cylinders 4 and the falling speed of the sliding block in real time, and outputs the pressure to each synchronous controller 7A corresponding to the base pressure of the rodless cavities of the leveling cylinders 4. The device comprises a leveling stage judgment module 7B1, a target force setting module 7B2, a correction value calculation module 7B3, a basic pressure iteration module 7B4, a basic pressure correction module 7B5 and a total tonnage control judgment module 7B 6.
Fig. 2 represents the internal working principle of the total ton controller 7B:
the leveling stage judgment module 7B1 judges the current leveling stage according to the falling speed of the slider, and if the speed is equal to the set speed, it indicates that the current leveling stage is in the no-load descending stage; if the speed is lower than the set speed, the pressing is in a pressing descending stage at present, and the pressing speed is slowed down because the sliding block receives great resistance after the material is pressed;
the target pressure setting module 7B2 sets a target total pressure for the rodless chambers of the four leveling cylinders 4 according to the current leveling stage.
The base pressure iteration module 7B3 gives a set of stored base pressures for each leveling cylinder rodless chamber at the current stage according to the leveling stage, which is the result of an iteration of the stable pressure at that stage in the past press.
The correction value calculation module 7B4 calculates a base pressure correction value according to the difference between the actual total pressure of the rodless cavities of the four leveling cylinders 4 and the target total pressure, the value being proportional to the difference;
the base pressure correction module 7B5 corrects the rodless cavity base pressures of the four leveling cylinders 4 according to the base pressure correction value, and subtracts the correction value from the stored base pressure of each leveling cylinder 4 to obtain a set of corrected base pressures;
the total tonnage control judgment module 7B6 judges the corrected base pressure, if each corrected base pressure is greater than 0, the fact that the leveling control can be realized by currently setting the total leveling force is shown, and the corrected base pressure is output; if the corrected base pressure is less than 0, the current situation is special, the set total leveling force is not enough to realize the leveling control, the total leveling force control is cancelled, the minimum base pressure of the rodless cavities of the four leveling cylinders is output, and an instruction is sent to a base pressure iteration module to cancel the iteration of the data;
the total output force of the leveling system is controlled to be a fixed value through the dynamic adjustment of the basic pressure of the rodless cavities of the four leveling cylinders 4.
Step three: the synchronous controller 7A controls the corresponding leveling cylinder to track the highest cylinder and perform accurate pressure control. The controller obtains the base pressure of the rodless cavity of the leveling cylinder 4 obtained by the total ton controller 7B, the displacement of the highest cylinder obtained by the highest cylinder judgment module 7C, the falling speed of the sliding block acquired by the speed sensor 2 and the displacement and pressure information of the corresponding leveling cylinder 4 in real time, and outputs the control voltage of the corresponding servo valve. The internal part of the valve consists of a displacement error compensator 7A1, a pressure closed-loop controller 7A2 and a valve port flow compensator 7A 3.
Fig. 1 represents the internal working principle of the synchronous controller 7A:
the displacement error compensator 7a1 obtains the displacement of the corresponding leveling cylinder 4 and the tracking displacement value obtained by the highest cylinder judgment module 7C in real time, calculates the difference between the two values, and converts the difference between the two values into a pressure compensation value. The larger the pressure compensation value is, the larger the displacement error between the leveling cylinder 4 and the highest cylinder is, and the pressure compensation value of the leveling cylinder 4 at the highest position is 0;
adding the pressure compensation value obtained by the displacement compensator 7A1 and the basic pressure value obtained by the total ton controller 7B to obtain a target pressure value corresponding to the leveling cylinder;
the pressure closed-loop controller 7a2 realizes that the single-cylinder pressure accurately follows the target pressure. The method comprises the steps of acquiring the pressure of a rodless cavity of a corresponding leveling cylinder 4 and a target pressure value in real time, calculating the difference value of the pressure and the target pressure value, converting the difference value into the adjusting voltage of a servo valve, wherein the size of the adjusting voltage is in direct proportion to the difference value;
the valve port flow compensator 7A3 obtains the falling speed of the slider 1 and the pressure value corresponding to the rodless cavity of the leveling cylinder 4 in real time, calculates the flow rate of the leveling cylinder which falls along with the slider 1 and needs to flow out of the servo valve 6 according to the falling speed of the slider 1 and the effective area of the rodless cavity of the leveling cylinder 4, and calculates the control voltage of the servo valve 6 which realizes the required flow rate under the current pressure by combining the characteristic parameters of the servo valve 6 and a valve port flow formula, namely the valve port flow compensation voltage;
the compensation voltage obtained by the valve port flow compensator 7A3 is added with the adjustment voltage obtained by the pressure closed-loop controller 7A2 to obtain the control voltage finally corresponding to the servo valve 6, and the pressure and the flow of the rodless cavity of the leveling cylinder 4 are controlled to realize position tracking and accurate pressure control.
And (3) acquiring information acquired by a sensor in real time in the leveling process, continuously repeating the steps from the first step to the third step, and dynamically adjusting the control voltage of the four servo valves 6 to realize position synchronous control and total output force control of the four leveling cylinders 4.
Each set value and iteration data of the total ton controller 7B are only suitable for one set of die, and if the die changes, the iteration data and related set values need to be reset.
The target total pressure of the rodless cavities of the leveling cylinders 4 can be determined according to the leveling force requirement in actual pressing, under the condition of outputting the lowest basic pressure, the pressure of the rodless cavities of the leveling cylinders 4 in the pressing process is obtained, verification is carried out for multiple times to determine the total leveling force required in the stage, and the target total leveling force is slightly larger than the actual requirement.
The initial leveling stage is mainly unbalance loading caused by the gravity of the die, the required leveling force is small, and a small target total pressure can be set; when the material is contacted with the mould pressing, the unbalance loading force can be formed by factors such as the gravity of a main cylinder pressure mould, the resistance of the mould pressing material and the like, the value is relatively large, and a large total output force of the leveling system needs to be set. The pressure of the main cylinder can be reduced to some extent by matching the total tonnage of the leveling system, and the energy consumption of the whole press is reduced.
The basic pressure iteration module records the pressure information of the rodless cavity of each leveling cylinder 4, if the pressure value is basically unchanged in a period of time, the pressure in the leveling stage is considered to be stable, the leveling moment can counteract the unbalance loading moment, and the originally stored basic pressure is corrected by the pressure value to be used as the initial basic pressure for the next pressing leveling.
The characteristic parameters of the servo valve 6 are obtained by experimental tests. The experiment ensures that the pressure difference value between the oil inlet and the oil outlet of the servo valve 6 is a fixed value, the flow of the servo valve 6 under different control voltages is tested, and the relation parameters between the flow and the control voltage and the pressure difference are determined by combining a valve port flow formula.
The above description is only an embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (10)
1. The utility model provides a combined material press four corners leveling system that realizes total tonnage control which characterized in that: the output end of the leveling system is a sliding block (1); a plurality of leveling units are uniformly arranged on the periphery of the sliding block; the leveling unit is connected with the control unit (7); each leveling unit comprises a leveling cylinder (4), an information acquisition element and a servo valve (6) connected with the leveling cylinder; the leveling cylinder rod is contacted with the sliding block in the leveling process, and the control unit synchronously controls the position and the output force of each leveling cylinder rod through the servo valve so as to level the sliding block;
the control unit comprises a total tonnage controller (7B), a highest cylinder judgment module (7C) and a plurality of single-cylinder synchronous controllers (7A) corresponding to the leveling units, and the leveling control method comprises the following steps;
a1, the highest cylinder judgment module judges the leveling cylinder with the largest extending cylinder rod as the highest cylinder through the information acquisition element, the displacement of the cylinder rod of the highest cylinder is taken as the maximum displacement value, and the maximum displacement value is sent to a single-cylinder synchronous controller (7A), so that the highest cylinder becomes the tracking target of other leveling cylinders for executing leveling operation;
a2, the total ton controller performs closed-loop control on the total pressure of the rodless cavities of the leveling cylinders, calculates the total resultant force output by the leveling system through acquiring pressure signals of the rodless cavities of the four leveling cylinders in real time, and distributes and corrects the basic pressure of the rodless cavities of the four leveling cylinders through comparing the total resultant force with a target resultant force;
a3, controlling each leveling cylinder by the synchronous controller to target the highest cylinder, and performing single-cylinder position tracking control to realize leveling control; and the rod-free cavity pressure and the cylinder rod position of each leveling cylinder are accurately controlled in the leveling control, so that the total output force of the sliding block is accurately controlled.
2. The composite press four-corner leveling system for realizing total tonnage control according to claim 1, characterized in that: four leveling units are uniformly arranged on the periphery of the driving surface of the sliding block; the total tonnage controller comprises a leveling stage judgment module (7B 1), a target total pressure setting module (7B 2), a correction value calculation module (7B 3), a basic pressure iteration module (7B 4), a basic pressure correction module (7B 5) and a total tonnage control judgment module (7B 6);
in step A2, the total tonnage controller (7B) distributes the rodless chamber base pressure of each leveling cylinder (4) by the following method;
b1, judging the current leveling operation stage by a leveling stage judgment module (7B 1), and controlling a target total pressure setting module (7B 2) to give a target total pressure of the four-cylinder rodless cavity required by the corresponding stage; the added value of the pressure of the rodless cavities of the leveling cylinders is the actual total pressure, and a correction value calculation module (7B 3) calculates a basic pressure correction value according to the difference value of the actual total pressure and the target total pressure;
b2, a basic pressure iteration module (7B 4) gives a group of four-cylinder storage basic pressure according to the current leveling stage, a basic pressure correction module (7B 5) corrects the storage basic pressure of four leveling cylinders according to a basic pressure correction value, and if the storage basic pressure is verified to be feasible by a total tonnage control judgment module (7B 6), the corrected four-cylinder correction basic pressure is used as output; otherwise, a four-cylinder minimum base pressure is output and a command is sent to the base pressure iteration module (7B 4) to cancel the iteration of the pressure data.
3. The composite press four-corner leveling system for realizing total tonnage control according to claim 2, characterized in that: the basic pressure iteration module (7B 4) records the pressure condition of the rodless cavity of each leveling cylinder in a leveling stage, and if the pressure is basically unchanged in a period of time, the pressure is considered to be stable, and the pressure is used for correcting the last iteration result.
4. The composite press four-corner leveling system for realizing total tonnage control according to claim 2, characterized in that: the synchronous controller comprises a position closed-loop controller (7A 1), a pressure closed-loop controller (7A 2) and a valve port flow compensator (7A 3); the single-cylinder synchronous controller (7A) realizes the position control and the accurate pressure control of each leveling cylinder by the following method;
c1, calculating the difference value between the displacement of the corresponding leveling cylinder and the displacement of the highest cylinder by the position closed-loop controller (7A 1), converting the difference value into a pressure compensation value, and adding the pressure compensation value and the basic pressure value of the rodless cavity of the corresponding leveling cylinder given by the total ton controller (7B) to obtain the target pressure value of the rodless cavity of the leveling cylinder; the pressure closed-loop controller (7A 2) calculates the difference between the actual pressure of the rodless cavity of the corresponding leveling cylinder and the target pressure, and converts the difference into the adjusting voltage of the servo valve (6);
c2, a valve port flow compensator (7A 3) calculates the compensation voltage of the servo valve (6) according to the actual pressure of the rodless cavity of the leveling cylinder (4) and the moving speed of the sliding block, and the flow requirement required by the movement of the leveling cylinder along with the sliding block is met; and adjusting the voltage and the compensation voltage to obtain a final control voltage, and controlling the opening of a servo valve of the leveling cylinder (4) according to a set value to enable the pressure of a rodless cavity of the leveling cylinder to be accurately matched with the target pressure, so that the highest cylinder is tracked by the corresponding leveling cylinder (4).
5. The composite press four-corner leveling system for realizing total tonnage control according to claim 2, characterized in that: the leveling stage judging module (7B 1) detects the moving speed of the sliding block (1) towards the material direction, if the speed is lower than a set value, the sliding block of the leveling system is judged to be in contact with the material, the material pressing advancing stage is started, and if the speed is the same as the set value, the sliding block is judged to be in the no-load moving stage.
6. The composite press four-corner leveling system for realizing total tonnage control according to claim 2, characterized in that: the total tonnage control judgment module (7B 6) judges the feasibility of correcting the base pressure of the four leveling cylinders so as to avoid the sudden increase of the leveling force requirement caused by special conditions, if the corrected base pressure of the four leveling cylinders is greater than 0, the corrected base pressure of the four cylinders is taken as output, otherwise, the minimum base pressure of the four cylinders is output.
7. The composite press four-corner leveling system for achieving total tonnage control according to claim 4, wherein the system comprises: the valve port flow compensator (7A 3) calculates the servo valve compensation voltage reaching the required flow under the current pressure condition according to a servo valve port flow formula and the characteristic parameters of the used servo valve.
8. The composite press four-corner leveling system for realizing total tonnage control according to claim 2, 3, 4, 5, 6 or 7, characterized in that: the four leveling cylinders are hydraulic cylinders; the rod cavities of the four leveling cylinders (4) are connected with a constant low-pressure oil source, oil discharge is completed through an overflow valve, and the rodless cavities are connected with the ports A of the corresponding servo valves and the pressure and the flow of the rodless cavities are controlled by the servo valves;
the information acquisition element comprises a speed sensor (2) for detecting the falling speed of the sliding block (1) in the leveling system, a displacement sensor (3) for detecting the displacement information of the cylinder rod of the leveling cylinder (4) and a pressure sensor (5) for detecting the pressure information of the rodless cavity of the leveling cylinder.
9. The composite press four-corner leveling system for achieving total tonnage control according to claim 8, wherein: the sliding block (1) is controlled by a host hydraulic system so as to keep the sliding block falling at a constant speed in the leveling stage and force the cylinder rod of the leveling cylinder (4) to fall along.
10. The composite press four-corner leveling system for achieving total tonnage control according to claim 9, wherein: the upper end surface of the sliding block is a driving surface, and the lower end surface of the sliding block is a material pressing surface; the leveling cylinder is fixed on the lower beam of the press and is positioned below four corners of the sliding block, a rod cavity of the leveling cylinder is introduced with a constant low-pressure oil source, and a rodless cavity of the leveling cylinder is connected with an opening A of the servo valve; the port B of the servo valve is sealed, and the port P and the port T are respectively connected with a high-pressure oil source and an oil tank; the control unit is electrically connected with the speed sensor, the displacement sensor, the pressure sensor and the servo valve.
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| CN110471462A (en) * | 2019-08-16 | 2019-11-19 | 北京航天发射技术研究所 | A kind of method for automatically leveling, system, terminal and the storage medium of multi-point support equipment |
| CN110744538B (en) * | 2019-09-12 | 2022-07-05 | 四川宏华电气有限责任公司 | Hydraulic position synchronous control method applied to petroleum machinery |
| CN110789043B (en) * | 2019-11-11 | 2022-02-22 | 重庆江东机械有限责任公司 | Position differential equivalence method high-response four-corner leveling system and leveling method |
| 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 |
| CN114165487B (en) * | 2021-12-16 | 2024-01-30 | 合肥合锻智能制造股份有限公司 | Hydraulic control system of composite material |
| CN115126733B (en) * | 2022-06-29 | 2024-06-07 | 天津市天锻压力机有限公司 | Multi-cylinder dynamic coordination control system and control method of hydraulic forging press |
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