A method and system for curved surface grinding of an automobile stamping die

Abstract

The present application relates to the field of industrial polishing, and particularly relates to a curved surface polishing method and system for an automobile stamping die, the present application determines the interface contact feature of a virtual grinding head and a three-dimensional model, performs a moving vector analysis on each marching point based on a spatial coordinate set and the three-dimensional model, subsequently determines a thermal stress coupling coefficient of a marching point cluster, distinguishes a thermal stress coupling marching point cluster, when the grinding head marches to the thermal stress coupling marching point cluster, determines a gradient optimization screening of part of the marching points, and optimizes the control parameters corresponding to the remaining marching points of the thermal stress coupling marching point cluster, the present application pre-senses a plurality of marching points with potential thermal stress coupling risks, adaptively selects an optimal optimization mode to optimize the control parameters of each marching point, and thus reduces the gradual accumulation of stress and thermal effects to form complex thermal stress coupling superposition, causes the phenomenon of uneven polishing surface and existing polishing texture when polishing a specific area, and improves the polishing quality.

Description

Technical Field

[0001] This invention relates to the field of industrial grinding, and more particularly to a method and system for grinding curved surfaces of automotive stamping dies. Background Technology

[0002] Surface grinding of automotive stamping dies is a key process to ensure the forming accuracy and service life of the dies. With the development of digital manufacturing technology, digital control methods have been gradually introduced into the field of die grinding. By using relevant sensors to monitor the grinding process and control grinding parameters, grinding efficiency and accuracy can be improved. In recent years, digital die grinding technologies have received widespread attention and importance due to their advantages in accuracy and quality assurance.

[0003] For example, Chinese Patent Publication No. CN119238222A discloses a method and system for controlling the trial and assembly of stamping dies. This method includes scanning the actual surface of the stamping die to generate actual three-dimensional point cloud data; determining the difference value based on the actual three-dimensional point cloud data and virtual three-dimensional point cloud data; determining a first area to be repaired based on the difference value and a preset tolerance range; simulating the deformation of the stamped part under different pressures based on a preset virtual assembly simulation model to predict the contact area and pressure distribution between the stamping die and the stamped part during the actual stamping process; determining a second area to be repaired based on the contact area and pressure distribution; determining a grinding area based on the first and second areas to be repaired; generating a grinding path based on the grinding area using a path planning algorithm; and controlling a grinding equipment to perform grinding actions on the stamping die according to the grinding path. This improves the efficiency of the entire trial and assembly process.

[0004] However, the following problems still exist in the existing technology. During continuous grinding, due to the morphological differences in different areas of the stamping die surface and the differences in the grinding head's own parameters, the contact stress and grinding stress of the grinding head on the complex curved surface will dynamically change. At the same time, as the grinding head moves along the planned path, the stress and thermal effects gradually accumulate, forming a complex thermal stress coupling superposition effect. This may affect the grinding quality in specific areas, causing uneven surface grinding or abnormal grinding textures. Summary of the Invention

[0005] Therefore, the present invention provides a method and system for grinding curved surfaces of automotive stamping dies, in order to solve the problem in the prior art that the gradual accumulation of stress and thermal effects leads to complex thermal stress coupling and superposition, resulting in uneven grinding surfaces and grinding textures in specific areas, which affect the grinding quality.

[0006] To achieve the above objectives, in one aspect, the present invention provides a method for grinding the curved surface of an automotive stamping die, comprising: Construct a three-dimensional model of the stamping die and a set of spatial coordinates for several travel points of the grinding head in three-dimensional space; Virtual grinding heads are constructed at each of the travel points based on the spatial coordinate set, so as to determine the interface contact characteristics between each virtual grinding head and the three-dimensional model; Based on the spatial coordinate set and the three-dimensional model, the movement vector analysis of each movement point is performed, including determining the movement vector of the movement point according to the spatial coordinate set, determining the principal curvature vector of the three-dimensional plane where the movement point is located, and analyzing the vector angle characteristics. Construct a cluster of travel points, and determine the thermal stress coupling coefficient of the travel point cluster based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, so as to distinguish thermal stress coupled travel point clusters. In response to the grinding head traveling to the thermal stress coupling travel point cluster, based on the traveling sequence of the grinding head, a portion of the travel points in the thermal stress coupling travel point cluster are determined, and the control parameters of each travel point are subjected to gradient optimization and screening according to the path sequence of the grinding head. Based on the gradient optimization screening results, the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster are optimized. The gradient optimization screening includes adjusting the control parameters corresponding to each travel point by different adjustment ratios, and monitoring the thermal stress characteristics when the grinding head moves to the corresponding travel point in real time, so as to screen the travel points.

[0007] Furthermore, the process of determining the interface contact characteristics between each virtual grinding head and the three-dimensional model includes, Determine the interface profile between the virtual grinding head and the 3D model corresponding to the travel point; The ratio of the maximum width to the minimum width of the interface contour is determined as a contact morphology parameter; The difference ratio between the radius of curvature of the grinding head and the radius of curvature of the three-dimensional model at the travel point is determined to obtain the contact curvature parameter; The contact morphology parameter and the contact curvature parameter are defined as the interface contact features.

[0008] Furthermore, the process of determining the movement vector of the travel point based on the spatial coordinate set, and determining the principal curvature vector of the three-dimensional plane where the travel point is located, in order to analyze the characteristics of the vector angle, includes the following: Determine the direction of movement of the starting point, and construct a movement vector in the direction of movement, using the starting point as the origin. The minimum curvature of the vertical projection point of the travel point on the surface of the three-dimensional model is determined as the principal curvature. The direction of the principal curvature is determined, and the principal curvature vector is constructed in the direction of the principal curvature, starting from the vertical projection point. The angle between the moving vector and the principal curvature vector is defined as the vector angle feature.

[0009] Furthermore, the process of constructing a cluster of travel points and determining the thermal stress coupling coefficient of the travel point cluster based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster includes the following steps: The surface of the 3D model is divided into several ranges, and the corresponding travel points within a single range are defined as a travel point cluster. Determine the interface contact characteristics and vector angle characteristics of the travel points; The ratio of the contact morphology parameter to the preset contact morphology parameter threshold is the contact morphology interference factor. The ratio of the contact curvature parameter to the preset contact curvature parameter threshold is the contact curvature interference factor. The ratio of the vector angle feature to the preset vector angle feature threshold is the vector angle interference factor; The single-coordinate thermal stress coupling coefficient is obtained by weighted summing of the contact morphology interference factor, contact curvature interference factor, and vector angle interference factor corresponding to the travel point. The mean value of the thermal stress coupling coefficient of each single coordinate corresponding to the travel point cluster is calculated as the thermal stress coupling coefficient.

[0010] Furthermore, the process of distinguishing thermal stress-coupled travel point clusters includes, The thermal stress coupling coefficient is compared with the preset thermal stress coupling threshold. If the thermal stress coupling coefficient is greater than or equal to the thermal stress coupling threshold, then the travel point cluster is determined to be a thermal stress coupled travel point cluster.

[0011] Furthermore, the process of determining a subset of travel points within the thermal stress-coupled travel point cluster based on the travel sequence of the grinding head includes, The travel points are sorted according to the travel sequence of the grinding head; The predetermined proportion of the movement point is determined from the beginning of the sorted sequence.

[0012] Furthermore, the process of adjusting the control parameters corresponding to each travel point by different adjustment ratios includes, The control parameters of the points are adjusted based on the sorting sequence, and the adjustment ratio is set according to the gradient of the sorting sequence. The control parameters include the grinding head rotation speed and the grinding head moving speed, and the gradient difference between the adjustment ratios of the control parameters corresponding to each travel point is related to the thermal stress coupling coefficient.

[0013] Furthermore, the process of real-time monitoring of the thermal stress characteristics as the grinding head moves to the corresponding travel point to screen travel points includes, Monitor the grinding head amplitude data and grinding head contact surface temperature data when the grinding head moves from the corresponding travel point to the next travel point; The vibration dispersion of the grinding head is determined based on the grinding head amplitude data, and the temperature dispersion is determined based on the grinding head contact surface temperature data. The thermal stress characterization features are determined based on the discrepancy of the grinding head vibration and the discrepancy of the temperature. Verify whether the screening criteria are met based on the thermal stress characterization characteristics; If the filtering conditions are met, the travel point is filtered, and the control parameters corresponding to the travel point are recorded. The screening condition is that the thermal stress characterization feature is less than a predetermined thermal stress characterization feature threshold.

[0014] Furthermore, the process of optimizing the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results includes, The selected travel points are determined, and the adjustment ratio of the control parameters corresponding to the travel points is determined. The control parameters of the travel points are then optimized based on the adjustment ratio.

[0015] On the other hand, a system for grinding curved surfaces of automotive stamping dies is also provided, comprising: The simulation module is used to construct a three-dimensional model of the stamping die and a set of spatial coordinates of several travel points of the grinding head in three-dimensional space, and to construct a virtual grinding head at each travel point based on the set of spatial coordinates to determine the interface contact characteristics between each virtual grinding head and the three-dimensional model. The vector analysis module is used to perform movement vector analysis on each travel point based on the spatial coordinate set and the three-dimensional model. This includes determining the movement vector of the travel point based on the spatial coordinate set and determining the principal curvature vector of the three-dimensional plane where the travel point is located, so as to analyze the vector angle characteristics. The cluster analysis module is used to construct a travel point cluster. Based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, the thermal stress coupling coefficient of the travel point cluster is determined to distinguish thermal stress coupled travel point clusters. The grinding control module responds to the grinding head traveling to the thermal stress coupling travel point cluster, determines a portion of the travel points in the thermal stress coupling travel point cluster based on the travel sequence of the grinding head, and performs gradient optimization and filtering of the control parameters of each travel point according to the path sequence of the grinding head. This is used to optimize the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results.

[0016] Compared with existing technologies, this invention constructs a virtual grinding head at the travel point, determines the interface contact characteristics between the virtual grinding head and the 3D model, performs movement vector analysis on each travel point based on the spatial coordinate set and the 3D model, determines the vector angle characteristics, and subsequently determines the thermal stress coupling coefficient of the travel point cluster based on the interface contact characteristics and vector angle characteristics, distinguishing thermal stress coupling travel point clusters. When the grinding head travels to the thermal stress coupling travel point cluster, some travel points are identified, and the control parameters of each travel point are gradient optimized and screened according to the path sequence of the grinding head. The control parameters corresponding to the remaining travel points of the thermal stress coupling travel point cluster are also optimized. This invention pre-senses several travel points with potential thermal stress coupling risks, conducts experimental optimization through gradient optimization screening, and subsequently selects a better optimization method to optimize the control parameters of the remaining travel points, thereby reducing the gradual accumulation of stress and thermal effects to form complex thermal stress coupling superposition, which leads to uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving grinding quality.

[0017] In particular, this invention determines the interface contact characteristics of the three-dimensional model. These interface contact characteristics include contact morphology parameters and contact curvature parameters. In practice, the contact morphology parameter reflects the uniformity of the interface contact. A larger contact morphology parameter indicates uneven distribution of the contact surface between the grinding head and the stamping die, with contact pressure concentrated along the wider direction, easily leading to line contact or local point contact effects. This results in increased local stress peaks, concentrated heat flux density, and a significantly increased risk of thermal stress. The contact curvature parameter reflects the degree of fit between the grinding head and the curved surface. A larger contact curvature parameter indicates poorer fit between the grinding head and the stamping die surface, making it more prone to... Edge contact or local point contact is prone to occur, which can significantly increase the risk of thermal stress. Based on this, the present invention characterizes the potential risk of thermal stress coupling from the contact angle between the grinding head and the surface of the stamping die by the interface contact characteristics. This provides data support for the subsequent calculation of the thermal stress coupling coefficient, and facilitates the subsequent advance perception of several travel points with potential thermal stress coupling risks. The invention also allows for the adaptive selection of the optimal optimization method to optimize the control parameters of each travel point, thereby reducing the gradual accumulation of stress and thermal effects that form complex thermal stress coupling superposition, which can lead to uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving the grinding quality.

[0018] In particular, this invention performs moving vector analysis, considering the stress applied by the grinding head to the surface of the stamping die during continuous grinding, and finally determines the vector angle characteristics. In reality, the direction of movement of the grinding head is the main direction of stress diffusion, and the direction of the principal curvature vector corresponds to the flattest direction of the surface. Therefore, the vector angle characteristics reflect the difference between the main direction of stress diffusion and the flattest direction of the surface. When the vector angle characteristics are small, it indicates that the stress applied by the grinding head diffuses smoothly towards the flattest direction of the surface, avoiding local accumulation. When the vector angle characteristics are large, it indicates that the stress is forced to concentrate in the direction of drastic curvature change, such as moving towards a convex surface, which can easily induce thermal stress effects. By determining the vector angle characteristics through moving vector analysis, data support is provided for the subsequent calculation of the thermal stress coupling coefficient.

[0019] In particular, this invention calculates the thermal stress coupling coefficient by comprehensively considering the thermal stress coupling superposition phenomenon during the grinding process, taking into account the contact angle between the grinding head and the surface of the stamping die, as well as the stress diffusion angle brought about by the grinding head's movement direction. This allows for the differentiation of thermal stress coupling travel point clusters and the prediction of several travel points with potential thermal stress coupling risks. Consequently, it facilitates the subsequent adaptive selection of a better optimization method to optimize the control parameters of each travel point, reducing the gradual accumulation of stress and thermal effects that form complex thermal stress coupling superposition, which can lead to uneven grinding surfaces and grinding textures in specific areas during grinding, thereby improving grinding quality.

[0020] In particular, when the grinding head travels to a cluster of thermal stress coupling travel points, this invention selects some travel points and sets control parameters with gradient differences for each travel point to determine reasonable parameter adjustment boundaries. In actual grinding, appropriately reducing control parameters may sacrifice grinding efficiency to some extent, but it can effectively alleviate thermal stress accumulation. Therefore, this invention employs gradient optimization screening to determine the thermal stress characterization characteristics under each adjustment ratio. When thermal stress coupling is significant, thermal stress concentration leads to fluctuations in the grinding head feedback force, resulting in abnormal morphologies such as ripples on the grinding surface. By analyzing the changes in thermal stress characterization characteristics under different adjustment ratios, control parameter adjustment boundaries that can significantly improve the thermal stress superposition phenomenon can be identified. This allows for maintaining high grinding efficiency while ensuring grinding quality. This invention optimizes the control parameters of each travel point by selecting a superior optimization method, reducing the gradual accumulation of stress and thermal effects that leads to complex thermal stress coupling superposition, which causes uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving grinding quality. Attached Figure Description

[0021] Figure 1 A schematic diagram illustrating the steps of a method for grinding the curved surface of an automotive stamping die according to an embodiment of the invention; Figure 2 A logic block diagram for distinguishing thermal stress coupled travel point clusters in an embodiment of the invention; Figure 3 A logic block diagram for whether to perform gradient optimization filtering in an embodiment of the invention; Figure 4 This is a logic block diagram for filtering travel points according to an embodiment of the invention. Detailed Implementation

[0022] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] Please see Figure 1 The diagram illustrates the steps of a method for grinding the curved surface of an automotive stamping die according to an embodiment of the invention. The method includes: Step S1: Construct a three-dimensional model of the stamping die and a set of spatial coordinates for several travel points of the grinding head in three-dimensional space; Step S2: Construct virtual grinding heads at each of the travel points based on the spatial coordinate set, so as to determine the interface contact characteristics between each of the virtual grinding heads and the three-dimensional model; Step S3, based on the spatial coordinate set and the three-dimensional model, performs movement vector analysis on each travel point, including determining the movement vector of the travel point according to the spatial coordinate set, determining the principal curvature vector of the three-dimensional plane where the travel point is located, and analyzing the vector angle characteristics. Step S4: Construct a travel point cluster. Determine the thermal stress coupling coefficient of the travel point cluster based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, so as to distinguish thermal stress coupled travel point clusters. Step S5: In response to the grinding head traveling to the thermal stress coupling travel point cluster, a portion of the travel points in the thermal stress coupling travel point cluster are determined based on the travel sequence of the grinding head, and the control parameters of each travel point are gradient optimized and filtered according to the path sequence of the grinding head. Step S6: Optimize the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results; The gradient optimization screening includes adjusting the control parameters corresponding to each travel point by different adjustment ratios, and monitoring the thermal stress characteristics when the grinding head moves to the corresponding travel point in real time, so as to screen the travel points.

[0025] Specifically, the present invention does not limit the specific form of the grinding head. Those skilled in the art can select a matching grinding head according to the specific structure of the stamping die. The driving device of the grinding head can be a robotic arm or an automated grinding machine tool, as long as it can drive the grinding head to move in space along a set path. This is the prior art and will not be described in detail here.

[0026] Specifically, the travel point is the coordinate point on the corresponding travel path of the grinding head. The coordinate point of the corresponding travel path of the grinding head can be obtained in advance, and a travel point can be selected at a predetermined distance, for example, a travel point can be selected every 0.5cm, thereby reducing the amount of data analysis and reflecting the overall travel of the grinding head.

[0027] Specifically, when creating a virtual grinding head, the virtual grinding head can be modeled according to the actual size of the grinding head in order to reflect the interference between the grinding head and the three-dimensional model as much as possible during the actual grinding process.

[0028] Specifically, the process of determining the interface contact characteristics between each virtual grinding head and the three-dimensional model includes, Determine the interface profile between the virtual grinding head and the 3D model corresponding to the travel point; The ratio of the maximum width to the minimum width of the interface contour is determined as a contact morphology parameter; The difference ratio between the radius of curvature of the grinding head and the radius of curvature of the three-dimensional model at the travel point is determined to obtain the contact curvature parameter; The contact morphology parameter and the contact curvature parameter are defined as the interface contact features.

[0029] It is understandable that the interface divides the virtual grinding head, and the part closer to the 3D model reflects the contact between the grinding head and the 3D model during the actual grinding process. Therefore, the radius of curvature of the grinding head is the average radius of curvature of the virtual grinding head surface closer to the 3D model.

[0030] It is understandable that, due to the physical dimensions of the grinding head, the travel point may be located outside the 3D model. In practice, for ease of calculation, the vertical projection point of the travel point on the surface of the 3D model can be determined, and the radius of curvature of this projection point along the direction of movement of the grinding head can be calculated. This radius of curvature is taken as the radius of curvature of the 3D model at the travel point.

[0031] In practice, the difference ratio is the ratio of the absolute difference between two values ​​to the mean of the two values.

[0032] This invention determines the interface contact characteristics of a three-dimensional model. These characteristics include contact morphology parameters and contact curvature parameters. In practice, the contact morphology parameter reflects the uniformity of the interface contact. A larger contact morphology parameter indicates uneven distribution of the contact surface between the grinding head and the stamping die, with contact pressure concentrated along the wider direction, easily leading to line contact or local point contact effects. This results in increased local stress peaks, concentrated heat flux density, and a significantly increased risk of thermal stress. The contact curvature parameter reflects the degree of fit between the grinding head and the curved surface. A larger contact curvature parameter indicates poorer fit between the grinding head and the stamping die surface, making it more prone to... Edge contact or local point contact can also significantly increase the risk of thermal stress. Based on this, the present invention characterizes the potential risk of thermal stress coupling from the contact angle between the grinding head and the stamping die surface by analyzing the interface contact characteristics. This provides data support for the subsequent calculation of the thermal stress coupling coefficient, and facilitates the advance detection of several travel points with potential thermal stress coupling risks. It also allows for the adaptive selection of the optimal optimization method to optimize the control parameters of each travel point, thereby reducing the gradual accumulation of stress and thermal effects that lead to complex thermal stress coupling and superposition, which can cause uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving grinding quality.

[0033] Specifically, the process of determining the movement vector of the travel point based on the spatial coordinate set, determining the principal curvature vector of the three-dimensional plane where the travel point is located, and analyzing the characteristics of the vector angle includes, Determine the direction of movement of the starting point, and construct a movement vector in the direction of movement, using the starting point as the origin. The minimum curvature of the vertical projection point of the travel point on the surface of the three-dimensional model is determined as the principal curvature. The direction of the principal curvature is determined, and the principal curvature vector is constructed in the direction of the principal curvature, starting from the vertical projection point. The angle between the moving vector and the principal curvature vector is defined as the vector angle feature.

[0034] In practice, the included angle of the vectors is an acute angle.

[0035] This invention employs moving vector analysis, considering the stress applied by the grinding head to the stamping die surface during continuous grinding, to ultimately determine the vector angle characteristics. In reality, the direction of the grinding head's movement is the primary stress diffusion direction, and the direction of the principal curvature vector corresponds to the flattest direction on the surface. Therefore, the vector angle characteristics reflect the difference between the primary stress diffusion direction and the flattest direction of the surface. A smaller vector angle characteristic indicates that the stress applied by the grinding head diffuses smoothly towards the flattest direction of the surface, avoiding local accumulation. A larger vector angle characteristic indicates that the stress is forced to concentrate in the direction of drastic curvature change, such as moving towards a convex surface, which can easily trigger thermal stress effects. Determining the vector angle characteristics through moving vector analysis provides data support for subsequent calculations of the thermal stress coupling coefficient. Specifically, the process of constructing a cluster of travel points and determining the thermal stress coupling coefficient of the cluster based on the interface contact characteristics and vector angle characteristics corresponding to the cluster includes the following steps: The surface of the 3D model is divided into several ranges, and the corresponding travel points within a single range are defined as a travel point cluster. Determine the interface contact characteristics and vector angle characteristics of the travel points; The ratio of the contact morphology parameter to the preset contact morphology parameter threshold is the contact morphology interference factor. The ratio of the contact curvature parameter to the preset contact curvature parameter threshold is the contact curvature interference factor. The ratio of the vector angle feature to the preset vector angle feature threshold is the vector angle interference factor; The single-coordinate thermal stress coupling coefficient is obtained by weighted summing of the contact morphology interference factor, contact curvature interference factor, and vector angle interference factor corresponding to the travel point. The mean value of the thermal stress coupling coefficient of each single coordinate corresponding to the travel point cluster is calculated as the thermal stress coupling coefficient.

[0036] The surface of the 3D model can be divided into several ranges by meshing. It can be understood that the range corresponds to the travel point. In practice, the vertical projection point of the travel point on the surface of the 3D model can be determined. If the projection point falls into the corresponding range, then the travel point and the range have a corresponding relationship. This will not be elaborated further.

[0037] During implementation, the preset contact morphology parameter threshold, contact curvature parameter threshold, and vector angle feature threshold are all pre-set. The process includes: Several stamping dies that have been polished were verified by a person skilled in the art, and the range of polishing textures or uneven polishing in each stamping die was recorded. Three-dimensional models of the stamping dies corresponding to each grinding are constructed, and the travel point of the grinding head is determined. A virtual grinding head is constructed at the travel point, and the contact morphology parameters, contact curvature parameters, and vector angle characteristics are recorded when the travel point is within the corresponding range. The statistical normal distributions of contact morphology parameters, contact curvature parameters, and vector angle features were determined respectively, so as to determine the 95% confidence intervals corresponding to the contact morphology parameters, the contact curvature parameters, and the vector angle features respectively. Set the lower limit of the 95% confidence interval corresponding to the contact morphology parameter as the contact morphology parameter threshold, set the lower limit of the 95% confidence interval corresponding to the contact curvature parameter as the contact curvature parameter threshold, and set the lower limit of the 95% confidence interval corresponding to the vector angle feature as the vector angle feature threshold.

[0038] Understandably, using the lower limit of the 95% confidence interval as the threshold means that in historical cases of grinding anomalies, this parameter value has a 95% probability of being greater than or equal to this threshold. Therefore, when the parameter value in the current grinding process is lower than this threshold, it can be considered to be relatively within a safe range.

[0039] In implementation, it is necessary to comprehensively consider the interference factors of contact morphology, contact curvature, and vector angle. Therefore, the weights are close when weighted summing. The weight of the contact morphology interference factor is set to 0.3, the weight of the contact curvature interference factor is set to 0.3, and the weight of the vector angle interference factor is set to 0.4. The vector angle feature directly affects the relative relationship between the grinding head movement direction and the principal curvature direction of the surface. This vector angle feature determines the contact pressure and pressure direction during grinding, and has a more significant impact on thermal stress accumulation and coupling effect. Therefore, it is given a slightly higher weight to improve the sensitivity and accuracy of the thermal stress coupling coefficient.

[0040] This invention calculates the thermal stress coupling coefficient by comprehensively considering the thermal stress coupling superposition phenomenon during grinding, taking into account the contact angle between the grinding head and the surface of the stamping die, as well as the stress diffusion angle brought about by the grinding head's movement direction. This allows for the differentiation of thermal stress coupling travel point clusters, predicting several travel points with potential thermal stress coupling risks. This facilitates the subsequent adaptive selection of a better optimization method to optimize the control parameters of each travel point, reducing the gradual accumulation of stress and thermal effects that form complex thermal stress coupling superposition, which can lead to uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving grinding quality.

[0041] Specifically, please refer to Figure 2 As shown, it is a logic block diagram of distinguishing thermally stressed coupled travel point clusters according to an embodiment of the invention. The process of distinguishing thermally stressed coupled travel point clusters includes, The thermal stress coupling coefficient is compared with the preset thermal stress coupling threshold. If the thermal stress coupling coefficient is greater than or equal to the thermal stress coupling threshold, then the travel point cluster is determined to be a thermal stress coupled travel point cluster.

[0042] It is understandable that when the thermal stress coupling threshold is equal to 1, it reflects the boundary where the grinding surface becomes abnormal due to the superposition of thermal stress coupling. Considering that there is a certain data error, the thermal stress coupling threshold can be slightly lower than 1, and is selected in the range [0.85, 0.95], preferably 0.85.

[0043] Specifically, the process of determining a subset of travel points in the thermal stress-coupled travel point cluster based on the travel sequence of the grinding head includes, The travel points are sorted according to the travel sequence of the grinding head; The predetermined proportion of the movement point is determined from the beginning of the sorted sequence.

[0044] It is understandable that the grinding head passes through the points in the corresponding order during operation, with the points that are passed first being listed first. The purpose of setting a predetermined ratio is to perform gradient optimization screening only on a small number of travel points in the future, so as to guide the adjustment of the control parameters corresponding to the remaining travel points. In practice, the predetermined ratio is selected within the range of [20%, 30%], preferably 25%, so as to minimize the negative impact on grinding efficiency while ensuring that statistically significant gradient optimization screening results can be obtained.

[0045] Specifically, please refer to Figure 3 The diagram shown is a logic block diagram of whether to respond to gradient optimization screening according to an embodiment of the invention. When the grinding head moves to the cluster of thermal stress coupling travel points, the response begins and gradient optimization screening is performed. During gradient optimization screening, the process of adjusting the control parameters corresponding to each travel point by different adjustment ratios includes... The control parameters of the points are adjusted based on the sorting sequence, and the adjustment ratio is set according to the gradient of the sorting sequence. The control parameters include the grinding head rotation speed and the grinding head moving speed, and the gradient difference between the adjustment ratios of the control parameters corresponding to each travel point is related to the thermal stress coupling coefficient.

[0046] During implementation, when adjusting the control parameters, the corresponding adjustment ratio of the control parameters will be reduced. It is understandable that appropriately reducing the grinding head speed and travel speed can alleviate the superposition of thermal stress coupling to a certain extent. Furthermore, the reduction of grinding head speed and travel speed has little impact on the final grinding quality, but it will affect the final grinding efficiency. Based on this, the present invention adopts a gradient optimization screening strategy to find the parameter adjustment boundary that can significantly improve the thermal stress coupling phenomenon by using the thermal stress characterization characteristics of different travel points, so as to ensure the effect of adjusting the control parameters while reducing the reduction of grinding efficiency.

[0047] In practice, the gradient difference is positively correlated with the thermal stress coupling coefficient. The larger the thermal stress coupling coefficient, the larger the gradient difference should be set, and vice versa.

[0048] It is understandable that when the thermal stress coupling coefficient is high, it indicates a significant risk of thermal stress superposition, requiring rapid adjustment of control parameters with a large step size to find the parameter boundary that can effectively suppress thermal stress within a limited number of travel points, thus avoiding the occurrence of surface anomalies. When the thermal stress coupling coefficient is low, a smaller gradient difference can be used to finely adjust the parameters, minimizing efficiency loss while ensuring grinding quality.

[0049] In practice, optional The ratio of the thermal stress coupling coefficient to the thermal stress coupling threshold is calculated and used as an adjustment coefficient. The product of the adjustment factor and the baseline gradient difference is determined as the current gradient difference.

[0050] The baseline gradient difference is selected within the interval [5%, 10%], preferably 5%.

[0051] For example, taking 5 travel points as an example, the calculated gradient difference is 6%; The adjustment ratios for each step are 0%, 6%, 12%, 18%, and 24%, respectively, showing a gradient difference of 6%.

[0052] During implementation, it is recommended to set the upper limit of the adjustment ratio to 50% to avoid excessive intervention in control parameters affecting the polishing quality.

[0053] When the adjustment ratio reaches the upper limit or the control parameters of some determined travel points have been adjusted, the gradient optimization screening is terminated.

[0054] Specifically, please refer to Figure 4 The diagram shown is a logic block diagram for screening travel points according to an embodiment of the invention. The process of screening travel points by real-time monitoring of the thermal stress characteristics when the grinding head moves to the corresponding travel point includes... Monitor the grinding head amplitude data and grinding head contact surface temperature data when the grinding head moves from the corresponding travel point to the next travel point; The vibration dispersion of the grinding head is determined based on the grinding head amplitude data, and the temperature dispersion is determined based on the grinding head contact surface temperature data. The thermal stress characterization features are determined based on the discrepancy of the grinding head vibration and the discrepancy of the temperature. Verify whether the screening criteria are met based on the thermal stress characterization characteristics; If the filtering conditions are met, the travel point is filtered, and the control parameters corresponding to the travel point are recorded. The screening condition is that the thermal stress characterization feature is less than a predetermined thermal stress characterization feature threshold.

[0055] Specifically, there are no limitations on the methods for acquiring the grinding head amplitude data and the grinding head contact surface temperature data. The grinding head is mounted on a robotic arm or automatic grinding machine. An accelerometer can be installed on the mounting base of the grinding head to monitor the vibration amplitude data. The contact surface temperature data can be detected non-contactly using an infrared temperature sensor. Of course, those skilled in the art can also use other methods to monitor the grinding head amplitude data and the grinding head contact surface temperature data, which will not be elaborated here. Specifically, the grinding head vibration dispersion is the standard deviation of the grinding head amplitude within a time period, and the temperature dispersion is the standard deviation of the grinding head contact temperature within a time period. After normalizing the discrepancies of the grinding head vibration and temperature to the range of [0,1], the thermal stress characterization features are obtained by weighted summation. The influence of the discrepancies of the grinding head vibration and temperature is comprehensively considered during the weighted summation, with each having a weight of 0.5.

[0056] The thermal stress characterization threshold is predetermined and verified by a person skilled in the art on several completed grinding stamping dies, and the range of grinding texture or uneven grinding in each stamping die is recorded. Record the thermal stress characterization characteristics when the grinding head moves to the corresponding travel point in each range, solve the statistical normal distribution of the thermal stress characterization characteristics, and set the lower limit of the 95% confidence interval as the threshold of the thermal stress characterization characteristics after reducing it by a predetermined proportion.

[0057] The lower limit of the 95% confidence interval reflects the minimum critical value of thermal stress characterization when anomalies occur on the polished surface. To avoid the subsequent polishing process remaining risky due to hitting the critical boundary during actual optimization of control parameters, a certain safety redundancy is required. Therefore, the lower limit value is multiplied by a predetermined ratio less than 1 to appropriately reduce the threshold of thermal stress characterization. The predetermined ratio is selected within the interval [0.75, 0.85], preferably 0.8.

[0058] Specifically, the process of optimizing the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results includes, The selected travel points are determined, and the adjustment ratio of the control parameters corresponding to the travel points is determined. The control parameters of the travel points are then optimized based on the adjustment ratio.

[0059] Specifically, determine the adjustment ratio of the control parameters corresponding to the selected travel points, and reduce the adjustment ratio of the control parameters of the remaining travel points.

[0060] This invention, when the grinding head travels to a cluster of thermal stress coupling travel points, selects a subset of travel points and sets control parameters with gradient differences for each travel point to determine reasonable parameter adjustment boundaries. In actual grinding, appropriately reducing control parameters may sacrifice grinding efficiency to some extent, but it can effectively alleviate thermal stress accumulation. Therefore, this invention employs gradient optimization screening to determine the thermal stress characteristics under different adjustment ratios. When thermal stress coupling is significant, thermal stress concentration leads to fluctuations in the grinding head feedback force, resulting in abnormal morphologies such as ripples on the ground surface. By analyzing the changes in thermal stress characteristics under different adjustment ratios, the control parameter adjustment boundaries that can significantly improve the thermal stress superposition phenomenon can be identified. This allows for maintaining high grinding efficiency while ensuring grinding quality. This invention optimizes the control parameters of each travel point by selecting a superior optimization method, reducing the gradual accumulation of stress and thermal effects that leads to complex thermal stress coupling superposition, which causes uneven grinding surfaces and grinding textures in specific areas during grinding, thus improving grinding quality.

[0061] This embodiment also provides a system for applying a method for grinding curved surfaces of automotive stamping dies, comprising: The simulation module is used to construct a three-dimensional model of the stamping die and a set of spatial coordinates of several travel points of the grinding head in three-dimensional space, and to construct a virtual grinding head at each travel point based on the set of spatial coordinates to determine the interface contact characteristics between each virtual grinding head and the three-dimensional model. The vector analysis module is used to perform movement vector analysis on each travel point based on the spatial coordinate set and the three-dimensional model. This includes determining the movement vector of the travel point based on the spatial coordinate set and determining the principal curvature vector of the three-dimensional plane where the travel point is located, so as to analyze the vector angle characteristics. The cluster analysis module is used to construct a travel point cluster. Based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, the thermal stress coupling coefficient of the travel point cluster is determined to distinguish thermal stress coupled travel point clusters. The grinding control module responds to the grinding head traveling to the thermal stress coupling travel point cluster, determines a portion of the travel points in the thermal stress coupling travel point cluster based on the travel sequence of the grinding head, and performs gradient optimization and filtering of the control parameters of each travel point according to the path sequence of the grinding head. This is used to optimize the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results.

[0062] It should be noted that the multiple functional modules involved in this application are only a logical division based on the functions implemented according to the present invention, and are not a strict limitation on the physical structure; in practical applications, the above functional modules can be implemented by one or more integrated circuits, a processor executing program code in memory, or a combination of the above devices.

[0063] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for grinding curved surfaces of automotive stamping dies, characterized in that, include: Construct a three-dimensional model of the stamping die and a set of spatial coordinates for several travel points of the grinding head in three-dimensional space; Virtual grinding heads are constructed at each of the travel points based on the spatial coordinate set, so as to determine the interface contact characteristics between each virtual grinding head and the three-dimensional model; Based on the spatial coordinate set and the three-dimensional model, the movement vector analysis of each movement point is performed, including determining the movement vector of the movement point according to the spatial coordinate set, determining the principal curvature vector of the three-dimensional plane where the movement point is located, and analyzing the vector angle characteristics. Construct a cluster of travel points, and determine the thermal stress coupling coefficient of the travel point cluster based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, so as to distinguish thermal stress coupled travel point clusters. In response to the grinding head traveling to the thermal stress coupling travel point cluster, based on the traveling sequence of the grinding head, a portion of the travel points in the thermal stress coupling travel point cluster are determined, and the control parameters of each travel point are subjected to gradient optimization and screening according to the path sequence of the grinding head. Based on the gradient optimization screening results, the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster are optimized. The gradient optimization screening includes adjusting the control parameters corresponding to each travel point by different adjustment ratios, and monitoring the thermal stress characteristics when the grinding head moves to the corresponding travel point in real time, so as to screen the travel points.

2. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of determining the interface contact characteristics between each virtual grinding head and the three-dimensional model includes, Determine the interface profile between the virtual grinding head and the 3D model corresponding to the travel point; The ratio of the maximum width to the minimum width of the interface contour is determined as a contact morphology parameter; The difference ratio between the radius of curvature of the grinding head and the radius of curvature of the three-dimensional model at the travel point is determined to obtain the contact curvature parameter; The contact morphology parameter and the contact curvature parameter are defined as the interface contact features.

3. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of determining the movement vector of the travel point based on the spatial coordinate set, determining the principal curvature vector of the three-dimensional plane where the travel point is located, and analyzing the characteristics of the vector angle includes the following steps: Determine the direction of movement of the starting point, and construct a movement vector in the direction of movement, using the starting point as the origin. The minimum curvature of the vertical projection point of the travel point on the surface of the three-dimensional model is determined as the principal curvature. The direction of the principal curvature is determined, and the principal curvature vector is constructed in the direction of the principal curvature, starting from the vertical projection point. The angle between the moving vector and the principal curvature vector is defined as the vector angle feature.

4. The method for grinding curved surfaces of automotive stamping dies according to claim 2, characterized in that, The process of constructing a cluster of travel points and determining the thermal stress coupling coefficient of the cluster based on the interface contact characteristics and vector angle characteristics corresponding to the cluster includes the following steps: The surface of the 3D model is divided into several ranges, and the corresponding travel points within a single range are defined as a travel point cluster. Determine the interface contact characteristics and vector angle characteristics of the travel points; The ratio of the contact morphology parameter to the preset contact morphology parameter threshold is the contact morphology interference factor. The ratio of the contact curvature parameter to the preset contact curvature parameter threshold is the contact curvature interference factor. The ratio of the vector angle feature to the preset vector angle feature threshold is the vector angle interference factor; The single-coordinate thermal stress coupling coefficient is obtained by weighted summing of the contact morphology interference factor, contact curvature interference factor, and vector angle interference factor corresponding to the travel point. The mean value of the thermal stress coupling coefficient of each single coordinate corresponding to the travel point cluster is calculated as the thermal stress coupling coefficient.

5. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of distinguishing thermal stress coupled travel point clusters includes, The thermal stress coupling coefficient is compared with the preset thermal stress coupling threshold. If the thermal stress coupling coefficient is greater than or equal to the thermal stress coupling threshold, then the travel point cluster is determined to be a thermal stress coupled travel point cluster.

6. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of determining a subset of travel points in the thermal stress-coupled travel point cluster based on the travel sequence of the grinding head includes, The travel points are sorted according to the travel sequence of the grinding head; The predetermined proportion of the movement point is determined from the beginning of the sorted sequence.

7. The method for grinding curved surfaces of automotive stamping dies according to claim 6, characterized in that, The process of adjusting the control parameters corresponding to each travel point by different adjustment ratios includes: The control parameters of the points are adjusted based on the sorting sequence, and the adjustment ratio is set according to the gradient of the sorting sequence. The control parameters include the grinding head rotation speed and the grinding head moving speed, and the gradient difference between the adjustment ratios of the control parameters corresponding to each travel point is related to the thermal stress coupling coefficient.

8. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of real-time monitoring of the thermal stress characteristics as the grinding head moves to the corresponding travel point, in order to screen the travel point, includes the following: Monitor the grinding head amplitude data and grinding head contact surface temperature data when the grinding head moves from the corresponding travel point to the next travel point; The vibration dispersion of the grinding head is determined based on the grinding head amplitude data, and the temperature dispersion is determined based on the grinding head contact surface temperature data. The thermal stress characterization features are determined based on the discrepancy of the grinding head vibration and the discrepancy of the temperature. Verify whether the screening criteria are met based on the thermal stress characterization characteristics; If the filtering conditions are met, the travel point is filtered, and the control parameters corresponding to the travel point are recorded. The screening condition is that the thermal stress characterization feature is less than a predetermined thermal stress characterization feature threshold.

9. The method for grinding curved surfaces of automotive stamping dies according to claim 1, characterized in that, The process of optimizing the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results includes: The selected travel points are determined, and the adjustment ratio of the control parameters corresponding to the travel points is determined. The control parameters of the travel points are then optimized based on the adjustment ratio.

10. A system for grinding the curved surface of an automotive stamping die according to any one of claims 1-9, characterized in that, include: The simulation module is used to construct a three-dimensional model of the stamping die and a set of spatial coordinates of several travel points of the grinding head in three-dimensional space, and to construct a virtual grinding head at each travel point based on the set of spatial coordinates to determine the interface contact characteristics between each virtual grinding head and the three-dimensional model. The vector analysis module is used to perform movement vector analysis on each travel point based on the spatial coordinate set and the three-dimensional model. This includes determining the movement vector of the travel point based on the spatial coordinate set and determining the principal curvature vector of the three-dimensional plane where the travel point is located, so as to analyze the vector angle characteristics. The cluster analysis module is used to construct a travel point cluster. Based on the interface contact characteristics and vector angle characteristics corresponding to the travel point cluster, the thermal stress coupling coefficient of the travel point cluster is determined to distinguish thermal stress coupled travel point clusters. The grinding control module responds to the grinding head traveling to the thermal stress coupling travel point cluster, determines a portion of the travel points in the thermal stress coupling travel point cluster based on the travel sequence of the grinding head, and performs gradient optimization and filtering of the control parameters of each travel point according to the path sequence of the grinding head. This is used to optimize the control parameters corresponding to the remaining travel points of the thermal stress coupled travel point cluster based on the gradient optimization screening results.

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