Flow and trajectory combined control system for automatic spraying of die-casting die lubricant

Abstract

The application discloses a flow and trajectory combined control system for automatic spraying of die casting die lubricant, which comprises the following steps: discretizing the die cavity surface and the spraying trajectory, calculating the deposition contribution coefficient of the trajectory sampling point to the surface sampling point according to the spraying cone space coverage relationship, and constructing the deposition contribution matrix; determining the target film thickness distribution of each surface sampling point, establishing the linear superposition relationship between the actual film thickness and the release density of each trajectory sampling point, solving the optimal release density sequence which makes the deviation of the actual film thickness distribution and the target film thickness distribution minimum under the constraints of the flow range of the flow valve and the speed range of the motion mechanism; and distributing the motion speed value and the flow value of each trajectory sampling point according to the release density sequence, and controlling the motion mechanism and the flow valve to execute spraying. The application can improve the uniformity of the lubricant film thickness distribution of the die cavity surface and the executability of the spraying control.

Description

Technical Field

[0001] This application relates to the field of die casting process control technology, specifically a combined control system for the flow rate and trajectory of automatic spraying of lubricant for die casting molds. Background Technology

[0002] In die casting production, mold cavities typically require the application of release agents or lubricants after each forming cycle to aid in casting demolding, reduce the risk of sticking, and regulate mold surface temperature. With increasing automation in die casting production units, existing equipment employs reciprocating spraying devices or multi-axis spraying robots. These devices utilize programmable logic controllers (PLCs), flow control devices, and nozzle assemblies to control the spraying position, spraying time, lubricant dosage, and air blowing process according to preset programs. Some equipment can save spraying programs for different molds and adjust parameters such as lubricant output and spraying speed.

[0003] However, die-casting mold cavities typically have deep cavities, bosses, ribs, and areas with small draft angles. The spray coverage of adjacent trajectory segments overlaps, and the actual deposition effect is also affected by factors such as spraying distance, incident angle, mold surface condition, and geometric obstruction. Therefore, the thickness of the lubricating film formed by the same amount of spraying is not consistent in different areas. During continuous production, the mold temperature also changes with the forming cycle and surface area. Under high-temperature conditions, the vaporization of droplets and the changes in the wetting properties of lubricant will further affect film formation and cooling effect. Existing spraying control usually sets the robot speed and valve flow rate separately based on trial molding experience. It lacks a unified quantitative relationship between trajectory position, spraying parameters, and surface deposition amount, making it difficult to take into account the flow range, movement speed, valve response, and mechanism acceleration and deceleration constraints. This easily leads to problems such as insufficient local spraying, lubricant accumulation, uneven film thickness distribution, or long spraying time. Further improvements are needed in the coordinated control method of spraying flow rate and movement trajectory. Summary of the Invention

[0004] The purpose of this application is to provide a combined flow and trajectory control system for automatic spraying of lubricant for die casting molds, so as to solve the problems mentioned in the background art.

[0005] According to one aspect of this application, a method for combined flow rate and trajectory control of automatic spraying of lubricant for die casting molds is provided, comprising the following steps: The surface of the mold cavity is discretized to obtain a set of surface sampling points, and the spraying trajectory path is discretized with equal arc length spacing to obtain a sequence of trajectory sampling points; For each pair of trajectory sampling points and surface sampling points, the deposition contribution coefficient is calculated based on the spatial coverage relationship of the spray cone, and all deposition contribution coefficients are assembled into a deposition contribution matrix; the deposition contribution coefficient represents the film thickness increment obtained by the corresponding surface sampling point when a unit volume of lubricant is released at the trajectory sampling point; Determine the target film thickness value at each surface sampling point to form the target film thickness distribution; Based on the deposition contribution matrix, a linear superposition relationship is established between the actual film thickness at each surface sampling point and the release density at each trajectory sampling point. Under the constraints of the flow valve flow range and the motion mechanism speed range, the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution is solved; the release density is the ratio of the flow rate value to the motion speed. Based on the optimal release density sequence, under the constraints of flow range and speed range, motion speed values ​​and flow rates are assigned to each trajectory sampling point; the motion mechanism and flow valve are controlled to perform spraying according to the assigned motion speed values ​​and flow rates.

[0006] Preferably, the step of calculating the deposition contribution coefficient based on the spatial coverage relationship of the spray cone includes: for each pair of trajectory sampling points and surface sampling points, determining whether the distance between the surface sampling point and the trajectory sampling point is within the effective spraying distance range, whether the azimuth angle of the surface sampling point relative to the trajectory sampling point is within the half-angle range of the spray cone, and whether there is mold geometry obstruction between the two; when all three conditions are met, the deposition contribution coefficient is calculated based on the cosine of the angle between the spray distribution density value at the radial position of the surface sampling point relative to the cone axis within the spray cone cross section and the spray direction and the surface normal vector at the surface sampling point; when any condition is not met, the deposition contribution coefficient is zero.

[0007] Preferably, when solving for the optimal release density sequence under the constraints of the flow valve's flow range and the motion mechanism's speed range, the applied constraints include: a boundary constraint, where the release density at each trajectory sampling point is not less than the ratio of the flow valve's minimum controllable flow rate to the motion mechanism's maximum allowable speed, and not more than the ratio of the flow valve's maximum output flow rate to the motion mechanism's minimum allowable speed; and a smoothing constraint, where the difference in release density between adjacent trajectory sampling points does not exceed the allowable change step size, which is determined based on the flow valve's maximum flow rate change rate and the motion mechanism's maximum acceleration.

[0008] Preferably, the allocation of motion speed and flow rate values ​​to each trajectory sampling point includes: for each trajectory sampling point, determining the feasible range of motion speed based on the corresponding release density value combined with flow rate range constraints and speed range constraints, and taking the upper bound as the initial motion speed value; performing a forward scan along the trajectory in ascending order of adjacent trajectory sampling points, and when the difference between the initial motion speed value of the subsequent trajectory sampling point and the motion speed value of the preceding trajectory sampling point exceeds the allowable speed increment, correcting the motion speed value of the subsequent trajectory sampling point to the sum of the motion speed value of the preceding trajectory sampling point and the allowable speed increment; performing a reverse scan along the trajectory in descending order of adjacent trajectory sampling points, and when the difference between the motion speed value of the preceding trajectory sampling point and the motion speed value of the subsequent trajectory sampling point exceeds the allowable speed increment, correcting the motion speed value of the preceding trajectory sampling point to the sum of the motion speed value of the subsequent trajectory sampling point and the allowable speed increment; the allowable speed increment is determined by the product of the maximum acceleration of the motion mechanism and the time required to pass through; and calculating the flow rate value of each trajectory sampling point based on the corrected motion speed value of each trajectory sampling point and the corresponding release density value.

[0009] Preferably, the solution for the optimal release density sequence adopts the effective set iterative method. Specifically, starting from the initial feasible solution that satisfies all bound constraints and smoothness constraints, the set of components on the constraint boundary is determined in each iteration. For the components outside the constraint boundary, the adjustment direction that reduces the deviation is solved. The process is continued along this direction until a new constraint boundary is reached or the deviation no longer decreases. The set of components on the constraint boundary is then updated and the next iteration begins, until the convergence criterion is met.

[0010] Preferably, the determination of whether there is mold geometry occlusion between the two lines is made by emitting a ray from the trajectory sampling point to the surface sampling point and detecting whether the ray intersects with the mold triangular mesh; if there is an intersection, it is determined to be occlusion.

[0011] Preferably, when the cosine of the angle between the spray direction and the surface normal vector is lower than the cutoff threshold, the corresponding deposition contribution coefficient is set to zero; the cutoff threshold is calibrated by measuring the ratio of the actual deposition amount to the theoretical deposition amount at different spraying incident angles, and the cosine of the angle corresponding to the ratio dropping to a predetermined lower limit is taken.

[0012] Preferably, determining the target film thickness value for each surface sampling point includes: setting a reference target film thickness value based on the draft angle and cavity depth of each surface region; collecting the current temperature value of each surface sampling point using an infrared temperature sensor before spraying; adjusting the reference target film thickness value proportionally based on the difference between the current temperature value of each surface sampling point and the reference temperature, as well as the temperature compensation coefficient, to obtain the target film thickness value for each surface sampling point; the temperature compensation coefficient is obtained by fitting and calibrating the relationship between the lubricant film thickness residual rate and temperature at different mold temperatures, and the reference temperature is the mold temperature at which the reference target film thickness value is calibrated.

[0013] Preferably, after each die-casting cycle in the continuous production process, the current mold surface temperature value is collected and the target film thickness distribution is updated accordingly. Based on the updated target film thickness distribution, the optimal release density sequence is recalculated and the motion speed and flow rate values ​​of each trajectory sampling point are redistributed.

[0014] In another aspect, this application also provides a combined flow and trajectory control system for automatic spraying of lubricant for die casting molds, comprising: The discretization module is used to discretize the surface of the mold cavity to obtain a set of surface sampling points, and to discretize the spraying trajectory path at equal arc length intervals to obtain a sequence of trajectory sampling points. The deposition contribution matrix construction module is used to calculate the deposition contribution coefficient for each pair of trajectory sampling points and surface sampling points based on the spatial coverage relationship of the spray cone, and assemble all the deposition contribution coefficients into a deposition contribution matrix; the deposition contribution coefficient represents the film thickness increment obtained at the corresponding surface sampling point when a unit volume of lubricant is released at the corresponding trajectory sampling point. The target film thickness determination module is used to determine the target film thickness value at each surface sampling point, and the target film thickness distribution is formed by the target film thickness values ​​at each surface sampling point. The release density optimization module is used to establish a linear superposition relationship between the actual film thickness at each surface sampling point and the release density at each trajectory sampling point based on the deposition contribution matrix, and to solve for the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution under the constraints of the flow valve flow range and the motion mechanism speed range; the release density is the ratio of the flow rate value to the motion speed. The parameter allocation and spraying control module is used to allocate motion speed and flow rate values ​​to each trajectory sampling point according to the optimal release density sequence, under the constraints of the flow rate range of the flow valve and the speed range of the motion mechanism, and control the motion mechanism and flow valve to perform spraying according to the allocated motion speed and flow rate values.

[0015] This application also provides an electronic device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the combined flow and trajectory control method for automatic spraying of lubricant for die casting molds as described above.

[0016] This application discretizes the spray trajectory and mold cavity surface, and establishes a deposition contribution matrix by combining the spray cone coverage, spray distance, incident angle, and geometric occlusion relationship, thereby forming a quantitative mapping between trajectory position, lubricant release per unit length, and surface film thickness. Simultaneously, the release density is characterized by the ratio of flow rate to motion velocity, and the optimal release density is solved under the constraints of flow valve output range, motion mechanism speed range, and smoothing of adjacent trajectory points. Then, forward and reverse scanning are used to obtain velocity sequences and corresponding flow sequences that meet acceleration and deceleration limits, enabling the spraying parameters for each trajectory segment to be coordinated and adjusted according to the cavity geometry and target film thickness requirements. This scheme can reduce film thickness deviations caused by spray overlap, oblique incidence, and local occlusion, making the actual film thickness distribution closer to the target film thickness distribution, and shortening the spraying time while ensuring the executable control parameters. Furthermore, updating the target film thickness and spraying parameters based on mold surface temperature can improve the consistency and adaptability of lubricant spraying during continuous die casting. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a method for combined flow and trajectory control of automatic spraying of lubricant for die casting molds, provided in an embodiment of this application.

[0019] Figure 2 This is a schematic diagram illustrating the principle of constructing the deposition contribution matrix as provided in the embodiments of this application.

[0020] Figure 3 A flowchart illustrating the allocation of motion speed and flow rate values ​​provided in this application embodiment.

[0021] Figure 4This is a schematic diagram illustrating the principle of joint optimization of flow rate and motion velocity based on release density, as provided in an embodiment of this application.

[0022] Figure 5 This is a schematic diagram of a combined flow and trajectory control system for automatic spraying of lubricant for die casting molds, provided in an embodiment of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] According to embodiments of this disclosure, this method is applicable to an automatic spraying system for die-casting molds equipped with a multi-axis motion mechanism and a proportional flow control valve. The motion actuator can be a 6-axis industrial robot or a multi-axis linear module, with the nozzle mounted on its end effector. Flow control employs a proportional solenoid valve or a servo needle valve, with clearly defined minimum controllable flow and maximum output flow. An infrared temperature sensor array is fixedly installed above the mold. The industrial controller possesses matrix operation capabilities. The spraying target is the cavity surface of an aluminum alloy die-casting mold, and the mold's 3D CAD model is known. Before this method is executed, the spatial motion path of the nozzle has been initially planned, and the path shape and nozzle pose at each point have been determined. However, the motion speed and flow rate at each position are given after being jointly solved by this method. The following formulas uniformly use millimeters as the unit of length and seconds as the unit of time.

[0025] The following detailed description, in conjunction with specific embodiments, illustrates the implementation process of the combined flow and trajectory control method for automatic spraying of lubricant for die-casting molds described in this application. It should be noted that this embodiment is merely for explaining this application and not for limiting the scope of protection of this application. Conventional adjustments or substitutions made by those skilled in the art to each step without departing from the concept of this application should be included within the scope of protection of this application.

[0026] like Figure 1 As shown in the figure, this application discloses a schematic diagram of a method for combined flow and trajectory control of automatic spraying of lubricant for die casting molds, including the following method steps: Step S1: Discretize the surface of the mold cavity to obtain a set of surface sampling points, and discretize the spraying trajectory path with equal arc length spacing to obtain a sequence of trajectory sampling points.

[0027] According to embodiments of this disclosure, triangular meshes of the cavity surface are extracted from the mold CAD model, and the geometric center of each triangular facet is taken as a surface sampling point, denoted as set. Simultaneously record the area of ​​each patch and the surface normal vector at that location. The planned trajectory path is arranged with equal arc length intervals. Discretized into a sequence of trajectory sampling points The spatial coordinates and orientation of the nozzle at each trajectory point are uniquely determined by the path geometry and the nozzle installation posture. Select based on the mold's external dimensions, for example, for molds with an external diameter of 400 to 800 mm. It can be configured to 2 to 5 mm, and the number of trajectory sampling points generated is generally in the range of 200 to 600.

[0028] Step S2: Calculate the deposition contribution coefficients based on the spatial coverage relationship of the spray cones and assemble them into a deposition contribution matrix. For each pair of trajectory sampling points and surface sampling points, calculate the deposition contribution coefficients based on the spatial coverage relationship of the spray cones, and assemble all deposition contribution coefficients into a deposition contribution matrix; the deposition contribution coefficients characterize the film thickness increment obtained by the corresponding surface sampling point when a unit volume of lubricant is released at the trajectory sampling point.

[0029] In one embodiment, this step establishes a quantitative correspondence between the spraying action at each point on the trajectory and the actual lubricant received at each surface point of the mold. During the spraying process of the die-casting mold, the spray originates from the nozzle and forms a cone-shaped diffusion, with the diameter of the covered area reaching 50 to 300 mm within a spraying distance of 100 to 300 mm. When the nozzle moves continuously along the trajectory, the spray coverage of adjacent trajectory segments on the mold surface overlaps, and one surface point is simultaneously affected by the spray from multiple trajectory points.

[0030] Specifically, for any trajectory sampling point With surface sampling points For points that are correct, first determine Does the spray cone cover the area? The determination includes three conditions: First, and The distance between them is within the effective spraying distance range, for example, 80 to 350 mm; secondly, Compared to The azimuth angle is within the half-angle range of the spray cone, that is... The angle of deviation from the spray cone axis is less than the nominal cone half angle of the nozzle. ;third, and There is no occlusion of mold geometry between the connecting lines. The specific method for determining occlusion is from... Towards Emit a ray and check if there is an intersecting facet between the ray and the triangular mesh of the mold. If an intersection point exists and the intersection point is located at... and If the values ​​are within the specified range, then occlusion is considered valid. Define an occlusion flag. The value is 1 if all three conditions are met, and 0 if any one condition is not met.

[0031] Among them, for Point pairs, calculate sedimentation contribution coefficient The physical meaning of the deposition contribution coefficient is that the nozzle is located at... Release a unit volume of lubricant at a time, surface sampling points The increase in film thickness obtained at the location, in units of The calculation method is as follows:

[0032] in for Vertical distance to the axis of the spray cone, in mm; for arrive The component of the distance along the cone axis, in mm; For the direction of spray and Surface normal vector The angle between them ranges from 0 to 90 degrees. The term reflects the geometric reduction of the deposition area when sprayed at an oblique angle. That is, when the spray is incident on the surface at an oblique angle, the same volume of lubricant is distributed over a larger projected area, and the film thickness per unit area is reduced accordingly.

[0033] in Let be the normalized volume distribution function of the spray cone, characterizing the spatial distribution density of a unit release volume, where is . Satisfying at any distance The integral over the entire area on the cross section is 1. Specifically, it is described using a normalized Gaussian distribution function:

[0034] Distribution standard deviation The spraying distance increases linearly:

[0035] in The spray cone angle of the nozzle is determined by the nozzle product specifications, and is commonly between 30 and 60 degrees for die-casting spraying. Taking a half-angle of 25 degrees and a spraying distance of 150 mm as an example... mm; directly below the cone axis place, mm -2 If the angle of incidence here is zero degrees, then mm -2 .

[0036] In one embodiment, when Below the cutoff threshold, due to severe droplet bounce caused by extreme oblique projection, the actual deposition amount is far lower than the theoretical calculation value. Therefore, the corresponding... Set to zero. The cutoff threshold is obtained through spraying test calibration, that is, spraying a fixed amount of lubricant onto a flat specimen at different incident angles and measuring the actual deposited film thickness. Plot the ratio of the actual value to the theoretical value as a function of the angle. Take the cosine of the angle corresponding to the ratio dropping to a predetermined lower limit (e.g., 0.1) as the cutoff threshold. The typical value is in the range of 0.1 to 0.2.

[0037] All pairs of points Assembled into dimensions Deposition contribution matrix Since the spray cone at each trajectory point covers only a limited number of surface points, the matrix is ​​sparse, with non-zero elements typically accounting for no more than 20%. In some embodiments, It can also be directly measured through static spraying calibration test, that is, after the fixed nozzle sprays at several known positions for a fixed time, the film thickness at each surface point is measured, and the contribution coefficient is calculated.

[0038] like Figure 2 As shown, Figure 2 This is a schematic diagram illustrating the principle of constructing the deposition contribution matrix as provided in an embodiment of this application. Figure 2 As shown, the spraying trajectory is discretized into multiple trajectory sampling points with equal arc length intervals. The surface of the mold cavity is discretized into multiple surface sampling points. For any pair of points consisting of a trajectory sampling point and a surface sampling point, the distance between the two points, the radial position of the surface sampling point relative to the spray cone axis, and the half-angle of the spray cone are used to determine whether the surface sampling point is within the effective spray coverage area. Simultaneously, the actual deposition amount is corrected based on the incident angle between the spray direction and the normal vector of the surface sampling point, and the intersection relationship between the ray and the mold geometry is used to determine whether occlusion exists. The corresponding deposition contribution coefficient is calculated only when the effective distance, spray cone coverage, and no-occlusion conditions are all satisfied, and the incident angle meets the deposition requirements. Otherwise, set it to zero. The nozzle is located at the trajectory sampling point. When a unit volume of lubricant is released, the surface sampling point The obtained film thickness increment. The deposition contribution coefficients of all point pairs are arranged according to the correspondence between surface sampling points and trajectory sampling points to form a sparse deposition contribution matrix (C=[ ]).

[0039] Step S3: Determine the target film thickness value at each surface sampling point to form the target film thickness distribution. Specifically, for each surface sampling point... Set the baseline target film thickness value according to the demolding process requirements of the region. The unit is mm. Higher values, such as 0.03 to 0.05 mm, are set for areas with draft angles less than 1.5 degrees or cavity depths exceeding 50 mm; lower values, such as 0.005 to 0.015 mm, are set for flat areas with ample draft angles. The baseline values ​​are determined based on the results of the first mold trial during mold change and remain fixed during continuous production with the same mold.

[0040] In one embodiment, before spraying, an infrared temperature sensor array collects the current temperature value at each surface sampling point. (Unit: °C), and the baseline value is adjusted proportionally to compensate for the accelerated evaporation effect in high-temperature regions:

[0041] in The reference temperature is the mold temperature used when the target film thickness was calibrated, for example, 200°C; Temperature compensation coefficient, unit °C -1 The physical meaning is the percentage increase in the target film thickness for every 1°C increase in temperature. The following calibration procedure was used to determine the optimal temperature range: Equal amounts of lubricant were sprayed onto the same area at multiple temperature levels (180°C, 220°C, 260°C, and 300°C). After a fixed set time, the residual film thickness was measured. A linear fit was then performed on the temperature using the ratio of the residual film thickness to the initial film thickness (i.e., the residual film thickness ratio). The absolute value of the slope of the fitted line is the final value. Typical values ​​range from 0.003 to 0.008°C. -1 The result To form the target film thickness distribution.

[0042] Step S4: Establish a linear superposition relationship based on the deposition contribution matrix and solve for the optimal release density sequence. Based on the deposition contribution matrix, establish a linear superposition relationship between the actual film thickness at each surface sampling point and the release density at each trajectory sampling point. Under the constraints of the flow valve flow range and the motion mechanism speed range, solve for the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution; the release density is the ratio of the flow rate value to the motion speed.

[0043] In one embodiment, the release density is defined. Trajectory sampling points Flow value (Unit: mm) 3 ( / s) and speed of motion The ratio (unit: mm / s) physically represents the volume of lubricant released per unit trajectory length, in mm. 2 Based on the deposition contribution matrix, surface sampling points Actual film thickness It equals the sum of the contributions from all trajectory sampling points that can cover that point:

[0044] This relationship is a linear superposition between the actual film thickness and the release density. That is, the film thickness at each surface point is obtained by weighted summation of the release densities of all trajectory points from which the spray cone can reach that point, according to their contribution coefficients. This can be written in matrix form. .

[0045] In one embodiment, the optimization objective is to minimize the deviation between the actual film thickness distribution and the target film thickness distribution, i.e., to solve for:

[0046] Two types of constraints are applied simultaneously, with the boundary constraints including the release density of each trajectory sampling point. Not less than the ratio of the minimum controllable flow rate of the flow valve to the maximum permissible speed of the moving mechanism. And not higher than the ratio of the maximum output flow of the flow valve to the minimum permissible speed of the moving mechanism. .For example mm 3 / s、 mm 3 / s、 mm / s, At mm / s mm 2 , mm 2 .

[0047] Smoothing constraints include ensuring that the difference in release density between adjacent trajectory sampling points does not exceed the allowable change step size. This step size is based on the maximum flow rate change rate of the flow valve. (Unit: mm) 3 / s 2 (as given in the valve body technical manual) and the maximum acceleration of the motion mechanism. (Unit: mm / s) 2 Joint determination: Take the median value of the velocity range. and median of flow range Calculate using the following formula:

[0048] The first term on the right-hand side of the equation reflects the contribution of flow rate change to the released density, while the second term reflects the contribution of velocity change to the released density. For example... mm 3 / s 2 , =600mm / s =4000mm 3 / s、 mm / s 2 When Δs = 3mm, ≈0.42 + 0.28 = 0.70 mm 2 .

[0049] It is understandable that the above problem is a least squares problem with bounded constraints and adjacent component difference constraints, which is solved by the effective set iterative method. The effective set method is a classic method for handling inequality constraint optimization. Its basic principle is to fix the variable components that currently fall on the constraint boundary (forming an active set), solve the unconstrained least squares direction only for the free components, and step along the direction until the new constraint boundary or the objective function no longer decreases, and then update the active set to enter the next iteration.

[0050] Specifically, starting from the initial feasible solution that satisfies all constraints (e.g., taking...) Starting from a constant set; in each iteration, the set of free variables outside the active set is... Extract the submatrix of the corresponding column from matrix C. Solving subproblems through QR decomposition The adjustment direction is obtained (r is the residual after deducting the contribution of active variables). The process proceeds along this direction until the constraint is reached or convergence occurs. This process is repeated after updating the active set. The convergence criterion is that the relative rate of decrease of the objective function is less than... .

[0051] Due to the matrix To address the sparsity of typical scales, sparse storage and sparse QR decomposition are employed. , It can be completed in 0.3 to 0.5 seconds, matching the calculation time window in the die-casting production cycle.

[0052] As an example, a mold surface has 800 sampling points and 300 trajectory points, with an initial uniform release density. mm 2 The root mean square deviation of the film thickness distribution calculated at the time from the target was approximately 0.012 mm; after 12 iterations, it decreased to below 0.002 mm, and the optimized release density was approximately 8 to 12 mm deep within the cavity. 2 The flat area is approximately 2 to 4 mm. 2 .

[0053] Step S5: Based on the optimal release density sequence, under the constraints of flow range and speed range, assign motion speed value and flow rate value to each trajectory sampling point; control the motion mechanism and flow valve to perform spraying according to the assigned motion speed value and flow rate value.

[0054] According to embodiments of this disclosure, the optimal release density sequence is obtained. After that, each one needs to be... Decomposed into specific motion velocity values and flow value .because For a given Satisfying this equation ( , The combination is not unique; this step selects the combination that minimizes the total spraying time within this degree of freedom.

[0055] Specifically, such as Figure 3 As shown, Figure 3 The flowchart for allocating motion speed and flow rate values ​​provided in this application embodiment shows that, in step S201, each trajectory sampling point... According to the corresponding release density value The feasible range of motion speed is determined by combining flow range constraints and speed range constraints. Specifically, the lower bound of the speed is taken as... The upper bound of speed is taken The upper bound is taken as the initial velocity value, ensuring that the point passes through the constraint area at the highest speed. mm 2 For example, the upper limit of the speed is min(1500,8000 / 6)≈min(1500,1333)=1333mm / s, and the lower limit of the speed is max(100,500 / 6)≈max(100,83)=100mm / s. The initial motion speed value is taken as 1333mm / s.

[0056] In step S202, adjacent trajectory sampling points are scanned forward along the trajectory in ascending order. When the difference between the initial velocity value of the subsequent trajectory sampling point and the velocity value of the preceding trajectory sampling point exceeds the allowable velocity increment for that segment, the velocity value of the subsequent trajectory sampling point is corrected to the sum of the velocity value of the preceding trajectory sampling point and the allowable velocity increment for that segment. The allowable velocity increment is determined by the maximum acceleration of the motion mechanism. and the time required to pass through this section The product is determined, that is For example, the speed at the previous point was 800 mm / s. mm / s 2 , mm, then the allowable speed increment is mm / s, the velocity at the later point is corrected to mm / s.

[0057] In step S203, after the forward scan is completed, a reverse scan is performed on adjacent trajectory sampling points in reverse order. If the difference between the velocity value of the previous trajectory sampling point and the velocity value of the next trajectory sampling point exceeds the allowable velocity increment for that segment, the velocity value of the previous trajectory sampling point is corrected to the sum of the velocity value of the next trajectory sampling point and the allowable velocity increment for that segment. The allowable velocity increment in the reverse scan is also... (The following velocity calculation takes time). The velocity sequence obtained after two scans, forward and backward, simultaneously satisfies the motion constraints in both acceleration and deceleration directions.

[0058] In step S204, based on the corrected motion velocity values ​​of each trajectory sampling point... With corresponding release density value Calculate the flow rate value at each trajectory sampling point. Optionally, the calculated flow sequence can be further checked to see if the flow difference between adjacent points exceeds the valve body response rate limit. If the flow rate exceeds the limit, the speed will be further reduced at that point until the flow rate change meets the constraint.

[0059] like Figure 4 As shown, Figure 4 This is a schematic diagram illustrating the principle of joint optimization of flow rate and motion velocity based on release density, provided in an embodiment of this application. Firstly, based on the target film thickness distribution at sampling points on each surface of the mold ( ) and sedimentary contribution matrix ( ), to establish a linear relationship between actual film thickness and release density. ), of which release density ( ), representing the volume of lubricant released per unit trajectory length. Under constraints of the flow valve output range, the motion mechanism speed range, and the smoothing of release density at adjacent trajectory points, the optimal release density sequence is obtained through constrained least squares solution. Subsequently, the feasible range of motion velocity was determined based on each release density value, and the velocity sequence was corrected using forward and reverse scanning to simultaneously meet the acceleration and deceleration capability limits; then, based on ( The corresponding flow rate sequence is calculated. The lower curve in the figure illustrates a higher release density in the deep cavity, with lubricant deposition increased by reducing the movement speed or increasing the flow rate. Flat areas utilize a lower release density and a higher movement speed. Ultimately, the movement speed sequence and flow rate sequence are executed synchronously to make the actual film thickness distribution approximate the target film thickness distribution.

[0060] In one embodiment, the obtained velocity curve and flow curve The data is sent to the motion controller and flow valve controller, both of which execute the spraying action synchronously. In continuous production, the current mold surface temperature is collected after each die-casting cycle, and the target film thickness distribution is updated accordingly. The optimal release density sequence is then resolved, and the motion speed and flow rate values ​​are redistributed. The deposition contribution matrix depends only on the spatial relationship between the mold geometry and the trajectory path, and remains unchanged throughout continuous production of the same mold, without being recalculated in cycles. The online calculation per cycle involves only constrained least squares solving and sequential scan allocation, and for a typical scale of 300 to 500 trajectory points, the time taken on an ARM Cortex-A72-level processor is no more than 0.3 to 0.5 seconds.

[0061] In some embodiments, when the temperature change amplitude of each surface sampling point between adjacent die-casting cycles does not exceed the recalculation trigger threshold, the motion speed value and flow rate value of the previous cycle are used without recalculation; recalculation and reallocation are triggered only when the temperature change amplitude exceeds the threshold. The recalculation trigger threshold is determined by statistically analyzing temperature fluctuation data from multiple cycles in continuous production, and taking the maximum temperature change amplitude corresponding to the condition that the film thickness deviation increment does not exceed a preset allowable range (e.g., 0.002 mm), typically in the range of 5 to 10°C.

[0062] This method explicitly quantifies the overlap effect of the spray cone coverage as a deposition contribution matrix, transforming the determination of trajectory velocity and flow rate from traditional segment-by-segment independent settings to joint optimization considering global spatial correlations. Within the physical constraints of the flow valve and motion mechanism, it finds the parameter combination that minimizes film thickness distribution deviation. Compared to sequential programming, this joint solution improves film thickness uniformity at the global level, reducing casting defects caused by local accumulation or insufficiency; the release density, after constraint optimization, naturally falls within the hardware's executable range, avoiding deviations caused by truncation during execution; the velocity allocation takes the highest feasible value while satisfying constraints, reducing spraying time; and parameters are updated online each cycle based on measured temperature to adapt to changes in thermal conditions.

[0063] It should be noted that although the operations of the method of this application are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flowchart can be performed in a different order. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0064] Please see Figure 5 , Figure 5 This application provides a combined flow and trajectory control system for automatic spraying of lubricant for die-casting molds. The system embodiments are similar to... Figure 1Corresponding to the illustrated method embodiments, this system can be specifically applied to various electronic devices. The system specifically includes: Discretization module 501 is used to discretize the surface of the mold cavity to obtain a set of surface sampling points, and to discretize the spraying trajectory path according to the equal arc length spacing to obtain a trajectory sampling point sequence. The deposition contribution matrix construction module 502 is used to calculate the deposition contribution coefficient for each pair of trajectory sampling points and surface sampling points according to the spatial coverage relationship of the spray cone, and assemble all the deposition contribution coefficients into a deposition contribution matrix; the deposition contribution coefficient represents the film thickness increment obtained by the corresponding surface sampling point when a unit volume of lubricant is released at the corresponding trajectory sampling point. The target film thickness determination module 503 is used to determine the target film thickness value of each surface sampling point, and the target film thickness distribution is formed by the target film thickness values ​​of each surface sampling point. The release density optimization module 504 is used to establish a linear superposition relationship between the actual film thickness of each surface sampling point and the release density of each trajectory sampling point based on the deposition contribution matrix, and to solve for the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution under the constraints of the flow valve flow range and the motion mechanism speed range; the release density is the ratio of the flow rate value to the motion speed. The parameter allocation and spraying control module 505 is used to allocate motion speed values ​​and flow values ​​to each trajectory sampling point according to the optimal release density sequence, under the constraints of the flow valve flow range and the motion mechanism speed range, and control the motion mechanism and flow valve to perform spraying according to the allocated motion speed values ​​and flow values.

[0065] Each processing unit and / or module in the embodiments of this application can be implemented by an analog circuit that implements the functions described in the embodiments of this application, or by software that executes the functions described in the embodiments of this application.

[0066] The above description represents the preferred embodiments of the present invention. It should be noted that, for those skilled in the art, various improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for combined flow rate and trajectory control of automatic spraying of lubricant for die-casting molds, characterized in that, Includes the following steps: The surface of the mold cavity is discretized to obtain a set of surface sampling points, and the spraying trajectory path is discretized with equal arc length spacing to obtain a sequence of trajectory sampling points; For each pair of trajectory sampling points and surface sampling points, the deposition contribution coefficient is calculated based on the spatial coverage relationship of the spray cone, and all deposition contribution coefficients are assembled into a deposition contribution matrix; the deposition contribution coefficient represents the film thickness increment obtained by the corresponding surface sampling point when a unit volume of lubricant is released at the trajectory sampling point; Determine the target film thickness value at each surface sampling point to form the target film thickness distribution; Based on the deposition contribution matrix, a linear superposition relationship is established between the actual film thickness at each surface sampling point and the release density at each trajectory sampling point. Under the constraints of the flow valve flow range and the motion mechanism speed range, the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution is solved; the release density is the ratio of the flow rate value to the motion speed. Based on the optimal release density sequence, under the constraints of flow range and speed range, motion speed values ​​and flow rates are assigned to each trajectory sampling point; the motion mechanism and flow valve are controlled to perform spraying according to the assigned motion speed values ​​and flow rates.

2. The method according to claim 1, characterized in that, The calculation of the deposition contribution coefficient based on the spatial coverage relationship of the spray cone includes: for each pair of trajectory sampling points and surface sampling points, determining whether the distance between the surface sampling point and the trajectory sampling point is within the effective spraying distance range, whether the azimuth angle of the surface sampling point relative to the trajectory sampling point is within the half-angle range of the spray cone, and whether there is mold geometry obstruction between the two; when all three conditions are met, the deposition contribution coefficient is calculated based on the cosine of the angle between the spray distribution density value at the radial position of the surface sampling point relative to the cone axis within the spray cone cross section and the spray direction and the surface normal vector at the surface sampling point; when any condition is not met, the deposition contribution coefficient is zero.

3. The method according to claim 1, characterized in that, When solving for the optimal release density sequence under the constraints of the flow range of the flow valve and the speed range of the motion mechanism, the applied constraints include: boundary constraints, the release density of each trajectory sampling point is not less than the ratio of the minimum controllable flow of the flow valve to the maximum allowable speed of the motion mechanism, and not more than the ratio of the maximum output flow of the flow valve to the minimum allowable speed of the motion mechanism; and smoothing constraints, the difference in release density between adjacent trajectory sampling points does not exceed the allowable change step size, the allowable change step size being determined based on the maximum flow rate change rate of the flow valve and the maximum acceleration of the motion mechanism.

4. The method according to claim 1, characterized in that, The process of assigning motion speed and flow rate values ​​to each trajectory sampling point includes: for each trajectory sampling point, determining the feasible range of motion speed based on the corresponding release density value combined with flow rate and speed range constraints, and taking the upper bound as the initial motion speed value; performing a forward scan along the trajectory in ascending order, and when the difference between the initial motion speed value of the subsequent trajectory sampling point and the motion speed value of the preceding trajectory sampling point exceeds the allowable speed increment, correcting the motion speed value of the subsequent trajectory sampling point to the sum of the motion speed value of the preceding trajectory sampling point and the allowable speed increment; performing a reverse scan along the trajectory in descending order, and when the difference between the motion speed value of the preceding trajectory sampling point and the motion speed value of the subsequent trajectory sampling point exceeds the allowable speed increment, correcting the motion speed value of the preceding trajectory sampling point to the sum of the motion speed value of the subsequent trajectory sampling point and the allowable speed increment; the allowable speed increment is determined by the product of the maximum acceleration of the motion mechanism and the time required to pass through; and calculating the flow rate value of each trajectory sampling point based on the corrected motion speed value and the corresponding release density value.

5. The method according to claim 3, characterized in that, The optimal release density sequence is solved using the effective set iterative method. Specifically, starting from an initial feasible solution that satisfies all bound constraints and smoothness constraints, the set of components on the constraint boundaries is determined in each iteration. For the components outside the constraint boundaries, the adjustment direction that reduces the deviation is solved. The process continues along this direction until a new constraint boundary is reached or the deviation no longer decreases. The set of components on the constraint boundaries is then updated before the next iteration begins, until the convergence criterion is met.

6. The method according to claim 2, characterized in that, The determination of whether there is mold geometry occlusion between the two lines is made by emitting a ray from the trajectory sampling point to the surface sampling point and detecting whether the ray intersects with the mold triangular mesh; if there is an intersection, it is determined to be occlusion.

7. The method according to claim 2, characterized in that, When the cosine of the angle between the spray direction and the surface normal vector is lower than the cutoff threshold, the corresponding deposition contribution coefficient is set to zero. The cutoff threshold is calibrated by measuring the ratio of the actual deposition amount to the theoretical deposition amount at different spraying incident angles, and the cosine of the angle corresponding to the ratio dropping to a predetermined lower limit is taken.

8. The method according to claim 1, characterized in that, The determination of the target film thickness value for each surface sampling point includes: setting a reference target film thickness value based on the draft angle and cavity depth of each surface region; collecting the current temperature value of each surface sampling point using an infrared temperature sensor before spraying; adjusting the reference target film thickness value proportionally based on the difference between the current temperature value of each surface sampling point and the reference temperature, as well as the temperature compensation coefficient, to obtain the target film thickness value for each surface sampling point; the temperature compensation coefficient is obtained by fitting and calibrating the relationship between the lubricant film thickness residual rate and temperature at different mold temperatures, and the reference temperature is the mold temperature at which the reference target film thickness value is calibrated.

9. The method according to claim 1, characterized in that, After each die-casting cycle in the continuous production process, the current mold surface temperature value is collected and the target film thickness distribution is updated accordingly. Based on the updated target film thickness distribution, the optimal release density sequence is re-solved and the motion velocity and flow rate values ​​of each trajectory sampling point are redistributed.

10. A combined flow and trajectory control system for automatic spraying of lubricant for die-casting molds, characterized in that, include: The discretization module is used to discretize the surface of the mold cavity to obtain a set of surface sampling points, and to discretize the spraying trajectory path at equal arc length intervals to obtain a sequence of trajectory sampling points. The deposition contribution matrix construction module is used to calculate the deposition contribution coefficient for each pair of trajectory sampling points and surface sampling points based on the spatial coverage relationship of the spray cone, and assemble all the deposition contribution coefficients into a deposition contribution matrix; the deposition contribution coefficient represents the film thickness increment obtained at the corresponding surface sampling point when a unit volume of lubricant is released at the corresponding trajectory sampling point. The target film thickness determination module is used to determine the target film thickness value at each surface sampling point, and the target film thickness distribution is formed by the target film thickness values ​​at each surface sampling point. The release density optimization module is used to establish a linear superposition relationship between the actual film thickness at each surface sampling point and the release density at each trajectory sampling point based on the deposition contribution matrix, and to solve for the optimal release density sequence that minimizes the deviation between the actual film thickness distribution and the target film thickness distribution under the constraints of the flow valve flow range and the motion mechanism speed range; the release density is the ratio of the flow rate value to the motion speed. The parameter allocation and spraying control module is used to allocate motion speed and flow rate values ​​to each trajectory sampling point according to the optimal release density sequence, under the constraints of the flow rate range of the flow valve and the speed range of the motion mechanism, and control the motion mechanism and flow valve to perform spraying according to the allocated motion speed and flow rate values.

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