Four-roller closed-loop cooperative control method based on consistency of axial dimension of veneer roll

Abstract

This invention belongs to the field of metal sheet forming control technology, specifically relating to a four-roller closed-loop collaborative control method based on the consistency of axial dimensions of the coiled sheet. The method includes: acquiring the basic elongation of the rear roll, characterizing the ideal rolling trajectory; real-time acquisition of driving torque and elongation data for the left and right sides of the rear roll, determining the equivalent deformation resistance on both sides, and acquiring the equivalent resistance imbalance factor; differentially distributing the basic elongation of the rear roll according to the equivalent resistance imbalance factor to obtain the initial target elongation on both sides of the rear roll; proportionally scaling and limiting the displacement difference of the initial target elongation based on the limit deflection difference to generate the final target elongation on both sides of the rear roll; and controlling the underlying actuator to perform differential pressing action based on the final target elongation. This invention can adapt to material differences in metal sheets, eliminate forming taper defects, and achieve dual protection of rolling quality and equipment operation safety within safety boundaries.

Description

Technical Field

[0001] This invention relates to the field of metal sheet forming control technology. More specifically, this invention relates to a four-roll closed-loop collaborative control method based on the consistency of axial dimensions of coiled sheets. Background Technology

[0002] In the field of sheet metal forming, four-roll plate bending machines are core equipment for manufacturing cylindrical and other metal parts, and are commonly used in the production of pressure vessels and heavy machinery. In conventional rolling processes, the upper and lower rolls are responsible for clamping the sheet metal and providing power, while the rear roll is driven by a servo system and moves along a set trajectory, applying a bending moment to the sheet metal to cause plastic deformation. The forming quality of the cylinder is highly dependent on the precise control of the rear roll displacement during production.

[0003] In practical applications, control systems typically use theoretical geometric derivations based on the static mechanical parameters of the equipment, the target radius, and the thickness to calculate the basic elongation required for the rear roller under ideal uniform conditions. In this mode, existing technology assumes that the internal material of the metal sheet is absolutely uniform and outputs identical synchronous displacement commands to the drive ends on both sides of the rear roller during the rolling process, aiming to roll a standard cylinder with consistent diameters at both ends.

[0004] However, this existing synchronous drive technology has significant drawbacks: due to the unavoidable residual internal stress and slight thickness deviations during the initial processing of the metal sheet, there is an objective difference in the actual deformation resistance on the left and right sides of the sheet. When both sides are subjected to absolutely the same displacement, the unloading springback on the harder side will be significantly larger, resulting in severe taper defects in the formed cylinder. If compensation is simply made by manually adjusting both ends afterward, it will not only be lagging but will also easily cause the limit displacement difference between the two ends to exceed the limit, thereby causing irreversible damage to the flexible self-aligning bearings of the equipment. Summary of the Invention

[0005] To address the technical problems of existing synchronous rolling processes failing to adapt to differences in sheet material, resulting in taper defects in the forming cylinder, and the inherent lag and potential damage to equipment caused by manual compensation, this invention provides a four-roller closed-loop collaborative control method based on the consistency of the axial dimensions of the rolled sheet, comprising: The following steps are taken: First, the base elongation of the rear roller, representing the ideal rolling trajectory, is obtained. During the metal sheet rolling process, real-time driving torque and elongation data for the left and right sides of the rear roller are collected. Based on the driving torque and corresponding elongation data, the equivalent deformation resistance on the left and right sides are determined respectively. Then, an equivalent resistance imbalance factor, representing the difference in material properties between the two sides, is obtained based on the equivalent deformation resistance on the left and right sides. The base elongation of the rear roller is differentially distributed according to the equivalent resistance imbalance factor to obtain the initial target elongation on the left and right sides of the rear roller. The allowable limit deflection difference of the four-roll plate rolling machine is obtained, and the displacement difference between the initial target elongation on the left and right sides of the rear roller is proportionally scaled and limited based on the limit deflection difference to generate the final target elongation on the left and right sides of the rear roller. Finally, the underlying actuator is controlled to perform differential pressing based on the final target elongation on the left and right sides of the rear roller to compensate for the deformation resistance difference between the left and right sides of the metal sheet in real time.

[0006] This invention uses physical modeling of real-time collected drive torque and elongation data during the rolling process to convert electromechanical equipment signals into equivalent resistance imbalance factors characterizing the internal properties of the sheet metal. This enables online measurement of the material property differences on both sides of the metal sheet and, based on this, differential allocation of the rear roller running reference. This allows the drive mechanism to perform differential pressing actions highly matched to the sheet metal deformation characteristics, adaptively offsetting the cylinder taper deviation caused by inconsistent unloading and springback, thus improving the geometric accuracy and quality stability of the formed product. Simultaneously, by combining the limit deflection difference to dynamically limit the differential displacement, the tilt of the equipment is strictly locked within the physical safety boundary while meeting the correction requirements. This effectively avoids mechanical structural damage caused by over-adjustment and achieves simultaneous optimization of production efficiency and equipment reliability under complex working conditions.

[0007] Preferably, the equivalent deformation resistance on the left side is the ratio of the driving torque data on the left side of the rear roller to the corresponding elongation data, the equivalent deformation resistance on the right side is the ratio of the driving torque data on the right side of the rear roller to the corresponding elongation data, and the equivalent resistance imbalance factor is the ratio of the equivalent deformation resistance on the left side to the equivalent deformation resistance on the right side.

[0008] Preferably, the differential allocation includes: the arithmetic mean of the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller is equal to the basic elongation of the rear roller, and the ratio of the initial target elongation on the left side of the rear roller to the initial target elongation on the right side of the rear roller is equal to the equivalent resistance imbalance factor.

[0009] Preferably, the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller satisfy the following expression: ; ; In the formula, This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; This represents the equivalent resistance imbalance factor.

[0010] Preferably, the proportional scaling limit includes: calculating the absolute value of the difference between the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller; in response to the absolute value of the difference being greater than the limit deflection difference, using the ratio of the limit deflection difference to the absolute value of the difference as the displacement safety scaling factor, and compressing the deviation of the initial target elongation from the basic elongation of the rear roller according to the displacement safety scaling factor.

[0011] Preferably, the final target elongation on the left side of the rear roller and the final target elongation on the right side of the rear roller satisfy the following expression: ; ; In the formula, This indicates the final target elongation on the left side of the rear roller; This indicates the final target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; Indicates the displacement safety scaling factor; This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller.

[0012] Preferably, the differential pressing action is performed by the control bottom actuator based on the final target elongation of the left and right sides of the rear roller, including: taking the final target elongation of the left and right sides of the rear roller as a given value, taking the real-time feedback elongation data of the left and right sides of the rear roller as a feedback value, performing closed-loop tracking calculation to generate control commands and send them to the motion controller.

[0013] The beneficial effects of this invention are as follows: By mapping real-time acquired drive torque data and elongation data to equivalent deformation resistance, this invention constructs an equivalent resistance imbalance factor characterizing the material property differences on both sides of the metal sheet. Then, based on this equivalent resistance imbalance factor, the basic elongation of the rear roller is differentially distributed, allowing the left and right pressing action of the rear roller to adapt to the local deformation characteristics of the sheet material. This effectively compensates for the unloading springback differences caused by uneven material hardness, eliminates the taper defect of the rolled cylinder, and improves forming accuracy. Simultaneously, by proportionally scaling and limiting the initially allocated displacement difference based on the equipment's allowable limit deflection difference, the actual tilt posture of the rear roller is strictly limited within the physical safety boundaries of the mechanical structure while maximizing the correction effect. This effectively avoids rigid damage to the flexible bearing caused by excessive differential adjustment, ultimately achieving dual protection of product forming quality and equipment operation safety under complex working conditions. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating a four-roller closed-loop collaborative control method based on the consistency of the axial dimensions of the coil in this invention; Figure 2 This is a schematic diagram of the geometric structure of a four-roll plate bending machine; Figure 3 This is a schematic diagram showing the changes in the equivalent deformation resistance and the equivalent resistance imbalance factor on both sides of the rear roller. Figure 4 The curves show the variation of the basic elongation of the rear roller and the initial target elongation on both sides of the rear roller. Figure 5 This is a schematic diagram of the dynamic limiting process for equipment safety under physical boundary constraints. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] This invention discloses a four-roll closed-loop collaborative control method based on the consistency of the axial dimensions of the coil, referring to... Figure 1 This includes steps S1-S6: S1: Obtain the back roll base elongation that characterizes the ideal winding trajectory.

[0018] It should be noted that traditional four-roll plate rolling machines often lack a unified theoretical benchmark when determining the basic motion trajectory, leading to blind control in the early stage of forming and resulting in deviations in the rolled plate size. Therefore, this invention derives the basic rolled plate radius and the basic elongation of the rear roller required to achieve the target springback curvature under an ideal and uniform rigid body state based on the static mechanical mathematical model of the equipment body, thereby providing a theoretical correction reference for subsequent dynamic differential feedback control.

[0019] Specifically, refer to Figure 2 A two-dimensional coordinate system is established with the intersection of the vertical line of the fixed lower roller center and the extension line of the rear roller's motion trajectory as the origin. Figure 2 In the diagram, A is the center point of the lower roller, B is the center point of the rear roller, and C is the center point of the upper roller, with coordinates (0, 1). The radius of the upper roller is denoted as . The radius of the rear roller is denoted as The ordinate of the center point C of the upper roller upper roller radius and the radius of the rear roller The measurements were obtained by the implementers through actual measurements of the four-roll plate bending machine. During the rolling and forming process of the metal sheet, the positions of the upper and lower rolls remain unchanged. The rear roll, driven by the servo system, moves along the inclined guide rail towards the coordinate origin to achieve the extrusion and bending of the metal sheet. The angle between the rear roll's trajectory line and the longitudinal axis is measured using an inclination measuring tool and recorded as the geometric angle of the rear roll's trajectory. Then the trajectory of the rear roller satisfies the equation ,in It is the tangent function.

[0020] Receive the target springback coil radius from the manufacturing execution system. With the thickness of the coil , Figure 2 Let D be the center of the bending circle of the rolled plate, and let its coordinates be (0, ...). Based on the constructed two-dimensional coordinate system and the thickness of the roll plate. Derivation of the ordinate position parameter of the rear roller center point B Let the radius of the roll be... Its satisfaction Then the ordinate of the bending center D of the rolled plate satisfies Draw a circle with center D of the coil bending point and passing through center B of the rear roller. The equation of the circle satisfies... The equation of the rear roller's running trajectory line. ordinate with the center of the bending circle of the rolled plate Substituting the equation of the circle and expanding it, we can obtain the ordinate position parameter of the center point B of the rear roller by taking the negative value of the quadratic equation. : The length from the original position of the rear roller center point to the origin is recorded as the total length at the starting position. The maximum mechanical retraction stroke of the rear roller in the four-roll plate bending machine is obtained by the implementers through actual measurement. The total length at the starting position is used. Subtract the ordinate position parameter of the rear roller center point B The absolute value of the projection along the running trajectory line is used to obtain the base elongation of the rear roller. : ,in, It is a cosine function.

[0021] During the bending deformation of a metal sheet, the outer side of the sheet elongates under tensile stress, while the inner side shortens under compressive stress. Therefore, there must exist a physical reference plane within the sheet whose length does not undergo strain deformation, i.e., a neutral layer. This invention targets the radius of the spring-loaded sheet. The radius of the outer circle after the sheet is formed is calibrated. Since the neutral layer is approximately located at the geometric center of the sheet thickness, the target springback roll radius is determined. Subtract the thickness of the coil Half of the material's macroscopic thickness can be used to remove the interference of the material's macroscopic thickness on the bending radius, thus obtaining the neutral layer radius. : ,in, Indicates the radius of the target springback plate; Indicates the thickness of the sheet.

[0022] There is an elastic recovery difference between the mechanical bending curvature of a metal sheet during compression forming and the curvature of the neutral layer after unloading and springback. To compensate for this springback error, this invention introduces the inherent mechanical properties of the metal sheet itself. Based on the physical evolution law of stress release and springback during elastic-plastic bending of the metal sheet, the actual bending radius of the coil required for processing is derived: According to the theory of metal plastic forming, the curvature difference before and after unloading is directly proportional to the yield strength of the material and inversely proportional to the elastic modulus and the sheet thickness. Its underlying physical equation is expressed as: In the formula, This represents the actual bending radius of the rolled sheet during the forming transient. Indicates the radius of the neutral layer after unloading and rebound; Indicates the thickness of the coil; Indicates the yield strength of the metal sheet; This indicates the elastic modulus of a metal sheet. This represents the theoretical constant for springback compensation. (For) By performing algebraic transformations and finding a common denominator, the actual bending radius of the rolled plate required for processing is derived. The expression is: To simplify the real-time load calculation at the underlying level of the subsequent control system, this invention extracts and integrates the inherent mechanical property constants of the material with the theoretical constants of springback compensation, defining the basic material property constants. Satisfying the expression: Material basic property constants Substitute the roll radius In the expression, the final derivation calculates the actual bending radius of the rolled plate. The simplified expression is: Among them, the yield strength of metal sheets With elastic modulus The springback compensation theoretical constants were obtained by the implementers by consulting the material mechanics parameter handbook for the corresponding metal. The calibration is obtained by the implementers based on the classic elastoplastic bending springback model in the existing technology, or by combining empirical experimental data from actual wide plate rolling on machine tools.

[0023] Furthermore, the radius of the rolled plate and the ordinate position parameter of the rear roller center point B Substitute into the base elongation of the rear roller The elongation of the rear roller base can be calculated from the expression. .

[0024] In one specific embodiment, the ordinate of the upper roller center point C is measured. upper roller radius mm, rear roller radius Geometric angle of the rear roller's running trajectory Total length of the starting position mm, substitute with the base elongation of the rear roller The expression is: The metal sheet that needs to be bent is Q235 steel plate, and its yield strength is... elastic modulus Theoretical constant for rebound compensation Based on the experimental data from actual four-roll plate bending machines under wide plate compression conditions, the implementation personnel calibrated the value to be 5, thus determining the material's fundamental property constant. Substitute the bending radius of the coil plate In the expression, it is .

[0025] Before actually performing Q235 steel plate coil processing, the control system only needs to receive the target springback coil radius from the manufacturing execution system. With the thickness of the coil This can be achieved by considering the elongation of the rear roller base as described above. Expression and bending radius of the coil The expression is used to calculate the theoretical basic elongation required for the rear roller. .

[0026] Back roll base elongation At the physical level, the ideal rolling trajectory of the four-roll plate bending machine is characterized. This refers to the theoretical geometrical motion path that the rear roll of the four-roll plate bending machine must follow to achieve the target forming radius, assuming the metal sheet to be processed is an ideal isotropic body with absolutely homogeneous material, absolutely uniform thickness, and no local hardening defects. Based on this, the basic elongation of the rear roll constitutes the standard action anchor point of the machine under synchronous equal displacement pressure, thus providing a reliable mathematical benchmark for subsequent dynamic differential displacement allocation based on the differences in local deformation resistance within the sheet.

[0027] S2: During the metal sheet rolling process, real-time data on the driving torque and elongation of the left and right sides of the rear roller are collected.

[0028] It should be noted that metal coil forming is a continuously evolving dynamic elastic-plastic deformation interaction process. Due to differences in physical properties, the left and right sides of the sheet will feed back significantly different resistance loads to the roller system in real time during the yielding and forming stage. In order to capture this asymmetric physical characteristic at the micro level, this invention uses a dual-drive servo system to directly collect the dynamic load state and kinematic displacement state fed back in real time by the drive shafts at both ends of the rear roller, so as to fully and without delay grasp the force distortion divergence of the sheet in the axial cross section.

[0029] Specifically, during the sheet metal forming process, the current feedback data from the servo motor driver on the left side of the rear roller is analyzed via an industrial real-time Ethernet bus and multiplied by a preset motor torque constant to obtain the real-time torque of the left side of the rear roller. Simultaneously, the real-time elongation of the left side of the rear roller is obtained via an absolute magnetostrictive displacement sensor arranged on the sliding guide rail of the bearing seat on the left side of the rear roller. Similarly, the current feedback data from the servo motor driver on the right side of the rear roller is analyzed via the same industrial real-time Ethernet bus and multiplied by a preset motor torque constant to obtain the real-time torque of the right side of the rear roller. Simultaneously, the real-time elongation of the right side of the rear roller is obtained via an absolute magnetostrictive displacement sensor arranged on the sliding guide rail of the bearing seat on the right side of the rear roller. To eliminate invalid displacement interference caused by the lack of contact with the sheet metal during the initial stage of equipment operation, the real-time elongation of the left and right sides of the rear roller are the effective pressing displacement after deducting the unloaded free travel.

[0030] Among them, the motor torque constant is a physical inherent attribute parameter that characterizes the proportional relationship between the output electromagnetic torque and the input armature current of the servo motor. It is calculated by the implementer based on the physical ratio of the rated torque to the rated current specified on the factory nameplate of the servo motor mounted on the four-roll plate bending machine.

[0031] S3: Based on the driving torque data and the corresponding elongation data, determine the equivalent deformation resistance on the left and the equivalent deformation resistance on the right respectively, and obtain the equivalent resistance imbalance factor that characterizes the difference in material properties on both sides based on the equivalent deformation resistance on the left and the equivalent deformation resistance on the right.

[0032] It should be noted that real-time torque reflects the deformation resistance of the sheet at the corresponding physical contact position, while real-time elongation reflects the actual mechanical displacement generated after the force is applied. This invention calculates the physical ratio of real-time torque to real-time elongation and uses this ratio to characterize the driving torque cost that must be paid to force the local sheet to produce a unit bending displacement, i.e., the equivalent deformation resistance. Then, by synchronously comparing the equivalent deformation resistance on the left and right sides, the external mechanical performance is traced back to the internal physical properties, thereby extracting the material hardness difference hidden at the left and right ends of the metal sheet.

[0033] Specifically, the equivalent resistance imbalance factor is calculated based on the real-time torque of the left side of the rear roller, the real-time torque of the right side of the rear roller, the real-time elongation of the left side of the rear roller, and the real-time elongation of the right side of the rear roller: In the formula, Indicates the equivalent resistance imbalance factor; This indicates the real-time torque on the left side of the rear roller; This indicates the real-time elongation of the left side of the rear roller; This indicates the real-time torque on the right side of the rear roller; This indicates the real-time elongation of the right side of the rear roller; It represents the equivalent deformation resistance on the left side, reflecting the degree of local deformation resistance on the left side of the metal sheet. Specifically, it is the driving torque cost that must be paid for each unit of actual bending displacement on the left side of the metal sheet. It represents the equivalent deformation resistance on the right side, reflecting the degree of local deformation resistance on the right side of the metal sheet. Specifically, it is characterized by the driving torque cost that must be paid for each unit of actual bending displacement on the right side of the metal sheet. This represents the physical ratio of the equivalent deformation resistance on the left and right sides. When the yield strength inside the left half of the metal sheet is relatively higher, meaning the left half is harder, the left side needs to overcome a greater resistance than the right side to produce the same unit displacement, resulting in an equivalent resistance imbalance factor. Greater than 1; when the yield strength of the right half of the metal sheet is relatively high, that is, the right half is harder, the same unit displacement on the right side requires overcoming greater resistance than on the left side, resulting in an equivalent resistance imbalance factor. Less than 1.

[0034] It should be noted that the real-time elongation of the left side of the rear roller is... At this time, the characterization equipment is in a static starting state where the pressing command has just been issued but the left mechanical shaft has not yet produced actual physical yield displacement. To avoid the equivalent deformation resistance denominator on the left side of the equivalent resistance imbalance factor expression being 0, which would cause the control system's underlying layer to overflow and crash due to division by zero, the control system forcibly assigns the real-time elongation of the left side of the rear roller at this moment a very small non-zero positive number that matches the hardware resolution of the underlying magnetostrictive displacement sensor; when the real-time elongation of the right side of the rear roller... At this time, the characterization device is in a static starting state where the pressing command has just been issued but the right mechanical shaft has not yet produced actual physical yield displacement. To avoid the equivalent deformation resistance denominator on the right side of the equivalent resistance imbalance factor expression being 0, which would cause the control system's underlying layer to overflow and crash due to division by zero, the control system forcibly assigns the real-time elongation of the right side of the rear roller at this moment a value that matches the hardware resolution of the underlying magnetostrictive displacement sensor. The extremely small non-zero positive number has the same physical length unit as the actual elongation and is set by the implementer according to the minimum effective detection step of the magnetostrictive displacement sensor. In one embodiment, the specific value is 0.001 mm.

[0035] For example, Figure 3 The diagram shows the changes in equivalent deformation resistance and equivalent resistance imbalance factor on both sides of the rear roller. It illustrates the quantitative monitoring process of material property differences by the system when rolling metal sheets with local hardening zones. When the rolling enters the middle stage, the equivalent deformation resistance on the left side shows a significant local upward trend, reflecting physical defects such as hardening or thickness deviation in the metal sheet at this position. At the same time, the equivalent resistance imbalance factor also jumps away from the reference value of 1.

[0036] S4: Differentially distribute the base elongation of the rear roller according to the equivalent resistance imbalance factor to obtain the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller.

[0037] It should be noted that after successfully identifying and extracting the equivalent resistance imbalance factor characterizing the difference in equivalent deformation resistance between the left and right sides, if the traditional synchronous equal displacement compression strategy is adopted, the material on the harder side will inevitably produce a greater elastic rebound after being unloaded. This unequal release of residual stress will still lead to a tapered defect with inconsistent diameters at both ends of the final formed roll. Therefore, in order to eliminate this rebound difference in physical space in advance, this invention introduces the concept of over-bending compensation, requiring the differential displacement distribution strategy to simultaneously consider the proportional constraint of equivalent deformation resistance and the mean value conservation constraint.

[0038] Specifically, based on the differential intervention logic to offset springback, the side with higher local yield strength must be pressed deeper to implement physical over-bending, thereby offsetting its larger springback after unloading in advance. According to the elastic-plastic deformation theory of sheet metal, the elastic springback amplitude of a local material has a linearly proportional relationship with its deformation resistance; that is, the greater the equivalent deformation resistance on a certain side, the greater the springback after unloading. In order to smooth out this unequal linear springback difference in physical space, the control system must implement proportional displacement compensation for areas with greater springback potential. Based on this, this invention establishes a hard constraint rule for displacement distribution, limiting the ratio of the target elongation at the left and right ends of the rear roller to be strictly equal to the ratio of the equivalent deformation resistance on the left and right sides of the rear roller, i.e., the equivalent resistance imbalance factor. The underlying logic is: if the equivalent deformation resistance on the left side is detected to be greater than that on the right side... If the multiple is used, it will be forcibly assigned to the left side. The relative target displacement is times that of the target, thus perfectly offsetting the proportionally amplified material springback with a proportionally amplified mechanical compression. Let the elongation of the target on the left be... The initial target elongation on the right side of the rear roller is ,but ,in It is the equivalent resistance imbalance factor.

[0039] Meanwhile, to prevent excessive compensation on one side from causing a lateral shift in the overall center of gravity of the roller system, which could lead to sheet misalignment or edge slippage, the mean value conservation constraint requires that the average value of the target elongation on both sides of the rear roller must be absolutely equal to the base elongation of the rear roller, i.e. ,in This is the base elongation of the rear roller.

[0040] This invention addresses the two constraints based on the aforementioned physical motivation. , By solving the simultaneous equations, we obtain the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller: In the formula, This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; This represents the equivalent resistance imbalance factor.

[0041] For example, Figure 4The curves show the changes in the basic elongation of the rear roller and the initial target elongation on both sides of the rear roller. When the deformation resistance on the left side is detected to increase, the initial target elongation on the left side of the rear roller shifts upward to apply a larger downward displacement to overcome the springback; correspondingly, the initial target elongation on the right side of the rear roller shifts downward.

[0042] S5: Obtain the allowable limit deflection difference of the four-roll plate bending machine, and based on the limit deflection difference, proportionally scale and limit the displacement difference of the initial target elongation on the left and right sides of the rear roll to generate the final target elongation on the left side of the rear roll and the final target elongation on the right side of the rear roll.

[0043] It should be noted that under certain extreme operating conditions, the initially calculated target elongation of the left side of the rear roller and the initial target elongation of the right side of the rear roller may differ significantly from the expected physical load. The objective root cause of this deviation lies primarily in the uneven physical properties of the metal sheet itself. Extreme batch differences or severe localized work hardening can lead to drastic changes in the material's hardness distribution, resulting in a significant deviation in the equivalent resistance imbalance factor. Furthermore, during the instantaneous start-up of the equipment, the system introduces extremely small non-zero positive values ​​at the hardware resolution level to avoid bottom-level division-by-zero crashes, thus ensuring the continuous issuance of control commands. However, this may also be accompanied by a brief amplification effect in the calculated values ​​within the extremely short sampling period. If the absolute displacement deviation is allowed to exceed the maximum physical deflection limit allowed by the self-aligning bearing of the equipment, it will cause mechanical damage to the self-aligning structure. Therefore, this invention applies a forced proportional scaling limit within the mechanical safety boundary to the initially calculated initial target elongation of the left side of the rear roller and the initial target elongation of the right side of the rear roller to ensure the absolute physical safety of the executed action.

[0044] Specifically, it is determined whether the absolute value of the difference between the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller is greater than the limit deflection difference. If so, the ratio of the limit deflection difference to the absolute value of this difference is used as the displacement safety scaling factor; otherwise, the displacement safety scaling factor is 1. The limit deflection difference is the maximum allowable height difference in tilting and misalignment of the rear roller mechanical bearing housing in physical space, obtained by the implementers based on the mechanical parameter manual of the self-aligning roller bearings of the equipment.

[0045] Based on the displacement safety scaling factor, the basic elongation of the rear roller, the initial target elongation on the left side of the rear roller, and the initial target elongation on the right side of the rear roller, calculate the final target elongation on the left side of the rear roller and the final target elongation on the right side of the rear roller: In the formula, This indicates the final target elongation on the left side of the rear roller; This indicates the final target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; Indicates the displacement safety scaling factor; This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller. This indicates the differential compensation section on the left side of the rear roller. This invention represents the differential compensation portion on the right side of the rear roller. The differential compensation portion is multiplied by a displacement safety scaling factor. This enables forced proportional contraction of over-limit displacement commands. When the difference between the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller is large enough to exceed the limit deflection difference, the displacement safety scaling factor... The corresponding reduction leads to a final target elongation on the left side of the compressed rear roller. Forced elongation of the rear roller base By tightening the clamps, the actual physical deflection angles at both ends of the equipment are strictly controlled within the safety drawing boundaries, effectively preventing rigid mechanical breakage and damage.

[0046] For example, Figure 5 This diagram illustrates the dynamic limiting process for equipment safety under physical boundary constraints. It compares the initial displacement difference between the initial target elongation on the left and right sides of the rear roller, the final displacement difference between the final target elongation on the left and right sides of the rear roller, and the limit deflection difference. When extreme unevenness in the local material of the plate causes the calculated initial displacement difference to exceed the limit deflection difference, the system activates a proportional scaling limiting mechanism. This ensures that the final displacement difference exhibits a controlled flattening trend in the over-limit area and is strictly contained within the limit deflection difference. Figure 5 As can be seen, in the process of pursuing the optimal correction effect, this invention can forcibly converge the over-limit command through the displacement safety scaling coefficient, ensuring that the tilting posture of the rear roller is always within the physical bearing range of the self-aligning bearing, effectively avoiding damage to the rigid structure of heavy equipment caused by excessive differential adjustment, and ensuring the robustness of the system in complex production environments.

[0047] S6: Control the bottom actuator to perform differential pressing action based on the final target elongation on the left and right sides of the rear roller, so as to compensate for the difference in deformation resistance on the left and right sides of the metal sheet in real time.

[0048] It should be noted that heavy-duty hydraulic actuators exhibit significant mechanical inertia and fluid hysteresis when responding to displacement commands. Therefore, this invention introduces a closed-loop tracking algorithm to dynamically feedforward and smooth the final target elongation after safety limiting, thereby eliminating the phase hysteresis defect at the actuator end.

[0049] Specifically, based on the final target elongation of the left side of the rear roller and the real-time elongation of the left side of the rear roller, combined with the proportional gain constant, integral gain constant, and derivative gain constant, the comprehensive closed-loop control command for the left side is calculated: In the formula, Indicates the current sampling step The displacement deviation on the left side of the rear roller; This indicates the final target elongation on the left side of the rear roller; This indicates the real-time elongation of the left side of the rear roller; This indicates the integrated closed-loop control command for the left side of the rear roller; Represents the proportional gain constant; Represents the integral gain constant; Represents the differential gain constant; Indicates sampling step The displacement deviation on the left side of the rear roller This indicates the time from the initial sampling step to the current sampling step. The discrete integral sum of the left displacement deviation; Indicates the previous sampling step The left-side displacement deviation. This invention utilizes the final target elongation on the left side of the rear roller. As a feedforward reference value, and combined with the displacement deviation of the left side of the rear roller in the current sampling step fed back by the actual sensor. Multi-dimensional dynamic compensation is performed when the real-time elongation of the left side of the rear roller is... Because the hydraulic inertia lags significantly behind the final target elongation on the left side of the rear roller. This causes a displacement deviation on the left side of the rear roller in the current sampling step. As the value increases, the proportional and integral compensation terms increase rapidly, thereby amplifying the comprehensive closed-loop control command on the left side of the rear roller. The forced hydraulic push rod system accelerates the propulsion, improves the system's start-up response speed, and suppresses steady-state static error.

[0050] Among them, the proportional gain constant Integral gain constant and differential gain constant The critical proportional gain was obtained by the implementers through debugging the discrete control domain under no-load operation of the equipment using the critical proportional gain method. Specifically, under no-load conditions, the critical proportional gain and critical oscillation period when the rear roller hydraulic servo system exhibits constant amplitude oscillation were obtained through pure proportional closed-loop testing. Subsequently, based on the Ziegler-Nichols empirical criterion, the proportional gain constant in the continuous domain was obtained. Integral time constant With differential time constant Finally, the discrete sampling period of the underlying programmable logic controller is considered. Calculate the discrete-domain integral gain constant. Discrete-domain differential gain constant .

[0051] Similarly, calculate the integrated closed-loop control command for the right side of the rear roller. .

[0052] Finally, the integrated closed-loop control commands for the left and right sides of the rear roller are sent in real time to the underlying motion controller responsible for driving the left and right bearing seats of the rear roller. This underlying motion controller coordinates the underlying actuators, converting the differential compensation algorithm in the digital domain into asynchronous pressing actions in the physical domain. The underlying actuators are a heavy-duty electro-hydraulic hardware assembly responsible for driving the roller system to generate physical displacement and output forming torque. They include core hardware such as hydraulic servo cylinders, electro-hydraulic proportional servo valves, and absolute displacement sensors. In specific implementation, after receiving the integrated closed-loop control commands from the left and right sides of the rear roller, the underlying actuators precisely regulate the flow and pressure through the matching electro-hydraulic proportional servo valves, independently driving the hydraulic servo cylinders supported under the bearing seats at the left and right ends of the rear roller. At the same time, combined with the high-frequency actual motion position feedback from the absolute magnetostrictive displacement sensors, it is ensured that the hydraulic servo cylinders on both sides strictly execute the differential smooth pressing extension action according to the commands until the overall forming process is completed.

Claims

1. A four-roll closed-loop collaborative control method based on the consistency of axial dimensions of rolled plates, characterized in that, include: Obtaining the base elongation of the rear roll, characterizing the ideal rolling trajectory, includes: during the rolling process of the metal sheet, the positions of the upper and lower rolls remain unchanged, and the rear roll, driven by a servo system, moves along an inclined guide rail towards the coordinate origin to achieve compression bending of the metal sheet. An inclination measuring tool is used to measure the angle between the rear roll's running trajectory line and the longitudinal axis, which is taken as the geometric angle of the rear roll's running trajectory and denoted as . The trajectory of the rear roller satisfies the equation ,in It is the tangent function; Receive the target springback coil radius from the manufacturing execution system. With the thickness of the coil Let the coordinates of the bending center D of the rolled plate be (0, ..., ...) Based on the constructed two-dimensional coordinate system and the thickness of the roll plate. Derivation of the ordinate position parameter of the rear roller center point B Let the radius of the roll be... ,satisfy Then the ordinate of the bending center D of the rolled plate satisfies Draw a circle with the bending center D of the coil as its center and passing through the center point B of the rear roller. The equation of the circle satisfies... The equation of the rear roller's running trajectory line ordinate with the center of the bending circle of the rolled plate Substituting into the circle equation and expanding it, then using the quadratic formula to find the negative value, we obtain the ordinate position parameter of the rear roller center point B. : ； In the formula, Let C be the ordinate of the center point C of the upper roller. The radius of the upper roller is... The radius of the rear roller is denoted as ; the length from the original position of the rear roller center point to the origin is denoted as the total length at the starting position. The total length of the starting position is obtained by actually measuring the maximum mechanical retraction stroke of the rear roller in the four-roll plate bending machine; using the total length of the starting position Subtract the ordinate position parameter of the rear roller center point B The absolute value of the projection along the running trajectory line is used to obtain the base elongation of the rear roller. : ,in, It is a cosine function; During the metal sheet rolling process, the driving torque data and elongation data of the left and right sides of the rear roller are collected in real time. Based on the driving torque data and the corresponding elongation data, the equivalent deformation resistance on the left and right sides are determined respectively. Based on the equivalent deformation resistance on the left and right sides, the equivalent resistance imbalance factor characterizing the difference in material properties between the two sides is obtained. The equivalent deformation resistance on the left side is the ratio of the driving torque data of the left side of the rear roller to the corresponding elongation data, the equivalent deformation resistance on the right side is the ratio of the driving torque data of the right side of the rear roller to the corresponding elongation data, and the equivalent resistance imbalance factor is the ratio of the equivalent deformation resistance on the left side to the equivalent deformation resistance on the right side. The base elongation of the rear roller is differentially allocated based on the equivalent resistance imbalance factor to obtain the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller; the differential allocation includes: the arithmetic mean of the initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller is equal to the base elongation of the rear roller, and the ratio of the initial target elongation on the left side of the rear roller to the initial target elongation on the right side of the rear roller is equal to the equivalent resistance imbalance factor; The permissible limit deflection difference of the four-roll plate bending machine is obtained, and the displacement difference of the initial target elongation on the left and right sides of the rear roll is proportionally scaled and limited based on the limit deflection difference to generate the final target elongation on the left and right sides of the rear roll. The proportional scaling and limiting includes: calculating the absolute value of the difference between the initial target elongation on the left and right sides of the rear roll; in response to the absolute value of the difference being greater than the limit deflection difference, the ratio of the limit deflection difference to the absolute value of the difference is used as the displacement safety scaling factor, and the deviation of the initial target elongation from the basic elongation of the rear roll is compressed according to the displacement safety scaling factor. The control mechanism at the bottom layer performs differential pressing based on the final target elongation on the left and right sides of the rear roller to compensate for the difference in deformation resistance between the left and right sides of the metal sheet in real time.

2. The four-roller closed-loop collaborative control method based on the consistency of axial dimensions of the rolled plate according to claim 1, characterized in that, The initial target elongation on the left side of the rear roller and the initial target elongation on the right side of the rear roller satisfy the following expression: ； ； In the formula, This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; This represents the equivalent resistance imbalance factor.

3. The four-roller closed-loop collaborative control method based on the consistency of axial dimensions of the rolled plate according to claim 1, characterized in that, The final target elongation on the left side of the rear roller and the final target elongation on the right side of the rear roller satisfy the following expression: ； ； In the formula, This indicates the final target elongation on the left side of the rear roller; This indicates the final target elongation on the right side of the rear roller; Indicates the base elongation of the rear roller; Indicates the displacement safety scaling factor; This indicates the initial target elongation on the left side of the rear roller; This indicates the initial target elongation on the right side of the rear roller.

4. The four-roller closed-loop collaborative control method based on the consistency of axial dimensions of the rolled plate according to claim 1, characterized in that, The differential pressing action is performed by controlling the underlying actuator based on the final target elongation on the left and right sides of the rear roller, including: The final target elongation on both sides of the rear roller is used as the given value, and the real-time feedback elongation data on both sides of the rear roller is used as the feedback value. Closed-loop tracking calculation is performed to generate control commands and send them to the motion controller.

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