Error evaluation method and correction method based on digital shape adjustment of flexible clamp bent frame

Abstract

The invention discloses an error evaluation method and correction method based on digital shape adjustment of a flexible clamp bent, and the method comprises the following steps: generating a final supporting position of a supporting column digital model capable of supporting a skin digital model, and obtaining a curved surface equation of the current skin digital model; according to the final supporting position coordinate data of the supporting stand column digital model, controlling the supporting stand columns on the bent frame to move to corresponding positions; the method comprises the following steps: acquiring the movement position of each supporting column on a bent and the position coordinate of the tail end of each current supporting column, and fitting to generate a supporting curved surface equation of the supporting columns and a linear equation of a straight line passing through the position coordinate point of the tail end of each supporting column and perpendicular to the plane where the bent is located; and calculating the model fitting degree between the skin digital-analog curved surface and the supporting curved surface, and evaluating the shape adjusting error of the bent frame according to the model fitting degree. The shape error of the bent support curved surface is evaluated by adopting the model fitting degree of the shape formed at the tail end of the support upright post of the bent and the actual digital-analog curved surface shape, so that the shape adjusting quality of the bent is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital measurement, and particularly relates to an error evaluation method and a correction method for digital shape adjustment of a flexible fixture rack. Background Art

[0002] In the laser profiling processing of skin chemical milling, a flexible fixture rack is used to support the skin, and then the chemical milling laser profiling processing is carried out. The skin is virtually supported by the flexible fixture rack in a dedicated preprocessing software, and the skin is processed by a virtual processing device. Then, the corresponding support point position data and the NC code for skin processing are generated. The motion control software is used to analyze the support point data to generate the motion instructions for rack shape adjustment, and the instructions are sent to the lower computer to drive the rack to move. After the movement is completed, the skin part is directly placed on the rack and adsorbed and positioned, and finally the NC program is imported to start the processing.

[0003] In this process, since the position accuracy of the support columns of the flexible fixture rack is not rechecked, and it is defaulted that the shape formed by the support rack after shape adjustment coincides with the shape of the skin, the skin may have been deformed during the process of installing and adsorbing the skin on the flexible fixture rack, which easily leads to unqualified quality of the skin parts processed by the chemical milling laser profiling equipment. Summary of the Invention

[0004] The purpose of the present invention is to provide an error evaluation method and a correction method for digital shape adjustment of a flexible fixture rack to solve the problem that the quality of rack shape adjustment cannot be guaranteed in skin processing by the flexible fixture rack.

[0005] The present invention is realized by the following technical solutions: An error evaluation method for digital shape adjustment of a flexible fixture rack includes the following steps: Place the skin digital model on the rack digital model in a modeling software, adjust the position of the support column digital model on the rack to make the support column digital model fit the skin digital model, generate the final support position of the support column digital model that can support the skin digital model, and obtain the surface equation of the current skin digital model; According to the coordinate data of the final support position of the support column digital model, control the support columns on the rack to move to the corresponding positions; Obtain the movement positions of the support columns on the rack and the position coordinates of the ends of the current support columns; Fit and generate the support surface equation of the support columns according to the position coordinates of the ends of the support columns; Fit and obtain the straight line equation of a straight line, where the straight line is the line passing through the end position coordinate points of the support columns and perpendicular to the plane where the rack is located; Obtain the intersection points of each straight line with the skin digital model surface and the support surface, and calculate the die-fitting degree between the skin digital model surface and the support surface according to the obtained intersection point coordinate data, and evaluate the alignment error of the bent frame according to the die-fitting degree.

[0006] In some embodiments, establish a field coordinate system in the modeling software, map the relative relationships among the bent frame, the machine tool, and the field coordinate system into the modeling software, and adjust the position of the bent frame digital model in the modeling software according to the relative positions of the bent frame, the machine tool, and the field coordinate system to make the position of the bent frame digital model consistent with the field.

[0007] In some embodiments, calculate the sum of the squares of the residuals of the end position coordinates of each support column, and obtain the surface equation coefficients of the support surface equation with the condition that the sum of the squares of the residuals is the smallest.

[0008] In some embodiments, calculate the die-fitting degree between the skin digital model surface and the support surface by calculating the die-fitting degree corresponding to each support column according to the intersection point coordinates of each straight line with the skin digital model surface and the support surface respectively.

[0009] In some embodiments, evaluate the alignment error according to the die-fitting degree corresponding to each support column.

[0010] In some embodiments, compare the die-fitting degrees corresponding to each support column with a set die-fitting degree threshold. When the die-fitting degrees corresponding to each support column are all greater than the set die-fitting degree threshold, it is determined that the alignment error of the bent frame meets the requirements of skin processing.

[0011] In some embodiments, when the die-fitting degree corresponding to a support column is less than the set die-fitting degree threshold, repeat the steps of aligning the bent frame and obtaining the die-fitting degree between the skin digital model surface and the support surface until the bent frame is aligned to meet the requirements of skin processing.

[0012] On the other hand, the present invention also provides a correction method using the error evaluation method for digital alignment of the bent frame based on a flexible fixture, and correct the alignment of the bent frame according to the error evaluation result of the alignment of the bent frame.

[0013] In some embodiments, when the die-fitting degree between the skin digital model surface and the support surface does not meet the requirements, repeat the steps of aligning the bent frame and obtaining the die-fitting degree between the skin digital model surface and the support surface until the alignment error of the bent frame meets the requirements of skin processing.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention evaluates the shape error of the support surface of the bent frame by using the die-fitting degree between the shape formed by the ends of the support columns of the bent frame and the shape of the actual digital model surface, which ensures the quality of the alignment of the bent frame and provides a basis for improving the processing accuracy of skin chemical milling laser profiling.

[0015] The present invention improves the matching degree between the rack and the skin by judging the shape error of the rack and correcting the rack shape adjustment according to the judgment result of the error, improves the installation position accuracy of the skin on the rack, and only needs to use a laser tracker to scan to detect the point data, thus improving the efficiency of shape adjustment and measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic diagram of adjusting the shape of the rack digital model by placing the skin digital model on the rack digital model in the embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of the cooperation of the skin digital model surface on the support column after adjusting the shape of the rack digital model in the embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of the surface formed by fitting the ends of the support columns in the embodiment of the present invention.

[0020] Wherein: 10. Skin digital model; 20. Rack, 21. Support column; 30. Fitted straight line; 40. Fitted support surface. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] In order to make the objectives, technical solutions and advantages of the present application clearer, the following further describes the specific embodiments of the present application in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Additionally, it should be noted that for the sake of convenience of description, only parts related to the present application are shown in the drawings rather than all the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. When the operations are completed, the process can be terminated, but there can also be additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0022] The present invention evaluates the error between the actual position and shape of the support columns of the flexible fixture rack in the chemical milling laser profiling equipment after shape adjustment and the virtual position of the rack support skin in the simulation digital model, so as to avoid the problem that the support shape of the rack after digital shape adjustment cannot meet the actual skin support requirements; moreover, based on the evaluation results of the shape adjustment error, it can be used to guide the correction of the support shape of the flexible fixture rack.

[0023] Refer to Figure 1 , the flexible fixture rack 20 includes a plurality of support columns 21 arranged in the vertical direction. By adjusting the positions of the ends of the support columns, the positions of the ends of the support columns can form any surface that matches the outer shape of the skin to be processed, so as to realize the support of the skin.

[0024] The support columns on the flexible fixture rack are arranged in an array, generally not less than 3×3, and the number of support columns is not less than 9.

[0025] In some embodiments of the present invention, the error evaluation method based on the digital shape adjustment of the flexible fixture rack includes the following steps: Place the skin digital model on the rack digital model in the modeling software, adjust the positions of the support column digital models on the rack so that the support column digital models fit the skin digital model, generate the final support positions of the support column digital models that can support the skin digital model, and obtain the surface equation of the current skin digital model; According to the coordinate data of the final support positions of the support column digital models, control the support columns on the rack to move to the corresponding positions; Obtain the moving positions of each support column on the rack and the position coordinates of the ends of each support column currently; Fit and generate the support surface equation of the support column according to the position coordinates of the ends of each support column; Fit the straight line equation of the straight line according to the position coordinates of the ends of each support column. The straight line is the line passing through the position coordinate points of the ends of each support column and perpendicular to the plane where the rack is located; Obtain the intersection points of each straight line with the skin digital model surface and the support surface, and calculate the mold fitting degree between the skin digital model surface and the support surface according to the obtained intersection point coordinate data, and evaluate the error of the rack shape adjustment according to the mold fitting degree.

[0026] In some embodiments, establish a field coordinate system in the modeling software, map the relative relationships among the rack, the machine tool, and the field coordinate system into the modeling software, and adjust the position of the rack digital model in the modeling software according to the relative positions of the rack, the machine tool, and the field coordinate system, so that the position of the rack digital model is consistent with the field.

[0027] In some embodiments, the sum of the squares of the residuals of the end position coordinates of each support column is calculated, and the coefficients of the surface equation of the support surface are obtained with the condition that the sum of the squares of the residuals is minimized.

[0028] In some embodiments, the fitting degree between the skin digital model surface and the support surface is calculated as follows: the fitting degree corresponding to each support column is calculated respectively according to the intersection coordinates of each straight line with the skin digital model surface and the support surface.

[0029] In some embodiments, the shaping error is evaluated according to the fitting degree corresponding to each support column.

[0030] In some embodiments, the fitting degrees corresponding to each support column are compared with a set fitting degree threshold. When the fitting degrees corresponding to each support column are all greater than the set fitting degree threshold, it is determined that the shaping error of the bent frame meets the requirements of skin processing.

[0031] In some embodiments, when the fitting degree corresponding to the support column is less than the set fitting degree threshold, the steps of shaping the bent frame and obtaining the fitting degree between the skin digital model surface and the support surface are repeated until the bent frame is shaped to meet the requirements of skin processing.

[0032] The error evaluation method and correction method for digital shaping of the flexible fixture bent frame of the present invention will be described in detail below with reference to specific embodiments.

[0033] S01. Place the skin digital model 10 to be processed into the modeling software, and import the bent frame digital model of the chemical milling laser profiling equipment into the modeling software.

[0034] S02. As Figure 1 , establish the on-site coordinates in the modeling software, determine the relationship between the bent frame, the machine tool and the on-site coordinate system, map the relative relationship among the three to the modeling software at the same time, and adjust the position of the bent frame digital model in the modeling software according to the relative positions of the bent frame, the machine tool and the on-site coordinate system, so that the position of the bent frame digital model is consistent with the actual on-site position.

[0035] S03. Place the skin digital model on the bent frame digital model, and the skin digital model should be placed as much as possible in the middle of the bent frame; Through the modeling software and the processing auxiliary plug-in, manually adjust the skin digital model and the support column digital model of the bent frame to make the support column digital model fit the skin digital model, then generate the final support position of the support column digital model that can support the skin digital model, and obtain the surface equation of the current skin digital model.

[0036] The expression of the surface equation of the skin digital model under the support of the current support column can be expressed as: ; Among them, (x, y, z) are the point data on the skin digital model surface, which are the known coefficients of the surface equation.

[0037] S04. According to the final support position coordinate data of the support columns in step S03, use the position analysis function in the motion control software to parse the motion instructions of the bent frame and send them to the lower computer to drive the support columns on the bent frame to move to the specified position.

[0038] S05. Obtain the motion positions of the current n support columns through the motion control software. Here, the motion position of the support column refers to the position after the support column is driven to move according to the target instruction. The position coordinates of the ends of all support columns are respectively: The position coordinate of the end of the first support column is: ; The position coordinate of the end of the second support column is: ; The position coordinate of the end of the third support column is: ; The position coordinate of the end of the fourth support column is: ; …… The position coordinate of the end of the nth support column is: .

[0039] The end position data of the support columns on the bent frame are obtained by measuring the point positions with a laser tracker. The measurement method is simple, and the measurement data is accurate and reliable.

[0040] S06. Use the position coordinates of the ends of the n support columns in step S05 to perform spatial quadratic surface fitting on the surface formed by the support columns of the bent frame through the method of surface fitting to obtain the support column surface on the bent frame.

[0041] Establish a spatial quadratic surface model formed by the position coordinates of the ends of the n support columns, which can be expressed as: ; Among them, are the coefficients of the surface equation to be solved.

[0042] Using the least squares method, to fit the spatial quadratic surface of the position coordinates of the ends of the n support columns, it is necessary to first calculate the sum of squared residuals , which can be expressed as: ; To find the best-fitting spatial quadratic surface, it is necessary to minimize , according to the sum of squared residuals For the expression, take the partial derivatives of the coefficients of each surface equation to be solved and set the partial derivatives equal to zero, which is expressed as: ; ; ; ; ; .

[0043] From the above equations, the coefficients of the spatial quadratic surface equation formed by the position coordinates of the ends of n support columns can be solved, which are respectively: 、 、 、 、 、 .

[0044] Thus, the surface equation of the fitting support surface 40 fitted from the position coordinates of the ends of the support columns can be obtained as: .

[0045] S07. According to the position coordinates of the ends of n support columns and the on-site coordinate system, fit the straight-line equations of the straight lines passing through the position coordinate points of the ends of each support column and perpendicular to the X-Y plane of the on-site coordinate system. This straight line is the fitted straight line 30, as shown in Figure 2 ; They are as follows: The straight-line equation passing through the coordinate is expressed as: ; The straight-line equation passing through the coordinate is expressed as: ; The straight-line equation passing through the coordinate is expressed as: ; …… The straight-line equation passing through the coordinate is expressed as: .

[0046] S08. Combining the straight-line equations in step S07, solve the intersection points of the n straight lines and the skin digital model surface equation generated in the digital model. The intersection coordinates of each straight line and the skin digital model surface equation are respectively: The straight line and the skin digital model surface equation The intersection point is: ; The straight line and the skin digital model surface equation The intersection points are: ; The straight line and the skin digital model surface equation The intersection points are: ; …… The straight line and the skin digital model surface equation The intersection points are: .

[0047] S09. Combining with the straight line equation in step S07, solve the intersection points of n straight lines and the surface equation fitted by the supporting columns of the bent frame. Refer to Figure 3 As shown, the intersection point coordinates of each straight line and the surface fitted by the supporting columns of the bent frame are respectively: The straight line and the surface fitted by the supporting columns ; The straight line and the surface fitted by the supporting columns ; The straight line and the surface fitted by the supporting columns ; …… The straight line and the surface fitted by the supporting columns .

[0048] S10. According to the intersection point coordinate data in step S08 and step S09, calculate the fitting degree between the skin digital model surface and the supporting surface fitted by the ends of the supporting columns of the bent frame, and calculate the fitting degree corresponding to each supporting column, which are respectively expressed as: ; ; ; …… .

[0049] S11. Using the fitting degrees calculated in step S10, judge whether the fitting degrees corresponding to each supporting column are all greater than the corresponding set fitting degree threshold , which is expressed as: ; ; ; …… 。

[0050] If the above conditions are all satisfied, the judgment of the shape adjustment error is completed. At this time, the shape adjusted by the support column can meet the requirements of skin processing.

[0051] S12. If the conditions of step S11 cannot be satisfied, appropriate adjustment can be made according to the position deviation. Otherwise, it is necessary to further detect the position accuracy of the support column and adjust the position of the support column according to the position accuracy; Repeat steps S04 - S11 to judge the surface fitting degree until the conditions of step S11 are satisfied, and complete the digital shape adjustment of the flexible fixture bent frame.

[0052] In the case where the position accuracy of the support column of the bent frame cannot meet the accuracy requirements, according to the judgment result of the shape adjustment error, a shape adjustment and correction operation is performed on the bent frame, and the support column of the bent frame is adjusted.

[0053] On the other hand, the present invention also provides a method for correcting the shape adjustment error of the bent frame by using the above error evaluation method for digital shape adjustment of the flexible fixture bent frame, and correcting the shape adjustment of the bent frame according to the error evaluation result of the shape adjustment of the bent frame.

[0054] In some embodiments, when the fitting degree between the skin digital model surface and the support surface does not meet the requirements, repeat the steps of shape adjustment of the bent frame and obtaining the fitting degree between the skin digital model surface and the support surface until the shape adjustment error of the bent frame meets the requirements of skin processing.

[0055] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention falls within the protection scope of the present invention.

Claims

1. Error evaluation method for digital shape adjustment of a flexible fixture rack, characterized in that It includes the following steps: Place the skin digital model on the bent frame digital model in the modeling software, adjust the position of the support column digital model on the bent frame to make the support column digital model fit the skin digital model, generate the final support position of the support column digital model that can support the skin digital model, and obtain the surface equation of the current skin digital model; According to the coordinate data of the final support position of the support column digital model, control the support columns on the bent frame to move to the corresponding positions; Obtain the movement positions of the support columns on the bent frame and the position coordinates of the ends of the current support columns; Fit and generate the support surface equation of the support columns according to the position coordinates of the ends of the support columns; Obtain the straight line equation of the straight line according to the position coordinates of the ends of the support columns. The straight line is the line passing through the end position coordinate points of the support columns and perpendicular to the plane where the bent frame is located; Obtain the intersection points of each straight line with the skin digital model surface and the support surface, and calculate the fitting degree between the skin digital model surface and the support surface according to the obtained intersection point coordinate data, and evaluate the adjustment error of the bent frame according to the fitting degree.

2. The error evaluation method for digital shape adjustment of a flexible fixture storage rack according to claim 1, characterized in that Establish a field coordinate system in the modeling software, map the relative relationship between the bent frame, the machine tool and the field coordinate system into the modeling software, and adjust the position of the bent frame digital model in the modeling software according to the relative positions of the bent frame, the machine tool and the field coordinate system to make the position of the bent frame digital model consistent with the field.

3. The error evaluation method for digital shape adjustment of a flexible fixture rack according to claim 1, characterized in that, Calculate the sum of the squared residuals of the position coordinates of the ends of each support column, and obtain the surface equation coefficients of the support surface equation with the condition that the sum of the squared residuals is the smallest.

4. The error evaluation method for digital shape adjustment of a flexible fixture storage rack according to claim 1, characterized in that Calculating the fitting degree between the skin digital model surface and the support surface means calculating the fitting degree corresponding to each support column according to the intersection point coordinates of each straight line with the skin digital model surface and the support surface respectively.

5. The error evaluation method for digital shape adjustment of a flexible fixture rack according to claim 4, characterized in that Evaluate the adjustment error according to the fitting degree corresponding to each support column.

6. The error evaluation method based on digital shape adjustment of a flexible fixture rack according to claim 5, characterized in that, Compare the fitting degrees corresponding to each support column with the set fitting degree threshold. When the fitting degrees corresponding to each support column are all greater than the set fitting degree threshold, it is determined that the adjustment error of the bent frame meets the requirements of skin processing.

7. The error evaluation method for digital shape adjustment of a flexible fixture storage rack according to claim 6, characterized in that When the fitting degree corresponding to the support column is less than the set fitting degree threshold, repeat the steps of adjusting the bent frame and obtaining the fitting degree between the skin digital model surface and the support surface until the bent frame is adjusted to meet the requirements of skin processing.

8. A correction method for the error evaluation method based on digital shape adjustment of a flexible fixture rack according to any one of claims 1-7, characterized in that Correct the adjustment of the bent frame according to the evaluation result of the adjustment error of the bent frame.

9. The correction method according to claim 8, wherein, When the fitting degree between the skin digital model surface and the support surface does not meet the requirements, repeat the steps of adjusting the bent frame and obtaining the fitting degree between the skin digital model surface and the support surface until the adjustment error of the bent frame meets the requirements of skin processing.

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