Dynamic tracking measurement method and device for continuous shape adjustment of mold surface

Abstract

The invention relates to a dynamic tracking measurement method and device for continuous shape adjustment of a mold profile, and solves the problems of feature point determination, profile curvature continuity, feature point adjustment sequence reasonability, adjustment precision and the like during mold profile adjustment. And converting the coordinates of the measured image and the design coordinates of the measured die, calculating the design target position points of the measured die and the optimal corresponding points on the surface of the to-be-measured die, and adjusting the Euclidean distances between all the target position points and the optimal corresponding points to meet error requirements. The device comprises a binocular tracking measurement unit, a mounting bracket, a holder, a computer and a calibration plate, and further comprises a signal generator and two groups of circular mark points which are respectively fixed at the edge position of rigid connection of the molded surface of the mold and on the surface of the molded surface. The method has the beneficial effects that the determination of the optimal control point during mold profile adjustment and the tracking measurement of the mold adjustment process are realized, the number and the positions of the dynamically tracked control points are not limited, and the mold adjustment efficiency and the mold adjustment accuracy are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of non-contact measurement (machine vision), and in particular to a dynamic tracking measurement method and device used in a large-scale continuously adjustable mold for a molding surface during a continuous molding adjustment process. Background Art

[0002] For molds with large molding areas and moldings that need to be adjusted, the prior art generally uses a continuously adjustable mold structure (such as a large stamping covering plate mold). A group of adjustable auxiliary supports are set on the back of the molding surface part of the mold, and local elastic deformation of the mold molding surface is achieved by adjusting the auxiliary supports.

[0003] Due to the fact that there are many control points (auxiliary support points) that need to be adjusted when adjusting the mold surface, and the large adjustment scale, even experienced professionals find it difficult to ensure the curvature continuity, the rationality of the control point adjustment sequence, and the adjustment accuracy during the mold surface adjustment process.

[0004] In the prior art, there are two main means of deformation measurement for mold surfaces. One is a measurement technology represented by a non-contact photogrammetry system, which takes multi-angle images of the object to be measured to resolve a set of high-precision relative three-dimensional coordinates of specific feature points. It has high measurement accuracy and many data points, but it cannot achieve continuous measurement; the other is a measurement technology represented by a laser tracker, which can statically or dynamically track moving points in a single space, and obtain high-precision absolute spatial coordinates of the target point. It has high measurement accuracy and can track continuously, but the data points are insufficient. Based on the technical defects of the above-mentioned existing measurement methods, designing a dynamic tracking measurement method and device specifically for continuous adjustment of mold surfaces is a key technology that urgently needs to solve the adjustment problem of mold surfaces. Summary of the invention

[0005] In order to ensure the determination of characteristic points, continuity of curvature of the surface, rationality of the control point adjustment sequence and adjustment accuracy when adjusting a large-scale continuously adjustable mold surface, the present invention discloses a dynamic tracking measurement method and device for continuous adjustment of the mold surface.

[0006] The method steps adopted by the present invention to achieve the purpose of the dynamic tracking measurement method are:

[0007] Step 1. Calibrate the binocular tracking measurement unit composed of a pair of CCD image sensors according to the perspective projection imaging model;

[0008] Place the mold to be tested under the bracket on which the measuring device is installed, and adjust the binocular tracking measurement unit so that the mold is in the visible area of ​​the CCD image sensor;

[0009] Randomly fix m circular marking points on the edge positions of the rigid connection of the mold surface that needs to be adjusted, as the mold surface adjustment reference group A;

[0010] At the same time, n circular marking points are randomly fixed on the mold surface that needs to be adjusted as the mold surface adjustment target group B;

[0011] Step 2. Send a synchronization signal through the signal generator, use two CCD image sensors to capture the measurement image, and extract the image coordinates of the circular mark points for stereo matching to obtain the three-dimensional coordinates M of the centers of all the circular mark points of the profile adjustment reference group A and the profile adjustment target group B. i =(x i ,y i ,z i ) and N k =(x k ,y k ,z k );

[0012] Where: 1≤i≤m, 1≤k≤n;

[0013] Step 3. Construct the three-dimensional covariance matrix COV(A) based on the coordinates of all circular markers of the reference group A according to the profile adjustment.

[0014]

[0015] in: The average value of m three-dimensional coordinates in the profile adjustment reference group A;

[0016] Step 4. Since the matrix of formula (1) above is a symmetric third-order square matrix, the covariance matrix can be decomposed into the following form using SVD decomposition;

[0017] COV(A)=USV -1 (2)

[0018] Among them, the matrix S is a diagonal matrix composed of eigenvalues ​​and is arranged in the order of ||λ1||≥||λ2||≥||λ3||, and V is the corresponding eigenvector matrix;

[0019]

[0020] Step 5. Take the cross product of vectors v1 and v2 and put them into vector v3, and normalize v1, v2 and v3 to get t1, t2 and t3;

[0021] by As the origin, an orthogonal coordinate system is established with t1, t2 and t3 as the x, y and z axes, where

[0022]

[0023] Step 6. According to the design coordinate system of the mold to be tested, calculate the translation vector T and the rotation matrix R between the above coordinate system and the above coordinate system;

[0024] Step 7. Use the above translation vector T and rotation matrix R to transform the three-dimensional coordinates of the midpoint of the target group B into the design coordinate system of the mold to be tested, and obtain the target position point The coordinate transformation relationship is:

[0025] P k =RN k +T (5)

[0026] Step 8. Calculate P using the closest point iteration algorithm k The best corresponding point Q on the surface of the mold to be tested k ;

[0027]

[0028] Step 9. Calculate P k With Q k The Euclidean distance between:

[0029]

[0030] Step 10. When d k When there is an error greater than the preset error e in the mold surface, the above steps are repeated during the mold surface adjustment process to achieve multi-point dynamic tracking measurement of the mold surface. k When it is less than the error e, the tracking measurement ends.

[0031] The technical solution adopted by the present invention to achieve the invention purpose of the dynamic tracking measurement device is:

[0032] The device comprises: a binocular tracking measurement unit consisting of a pair of image sensors, a mounting bracket, a pan-tilt platform, a computer, a signal generator, a calibration plate and a circular marking point. The binocular tracking measurement unit is fixed on the mounting bracket through the pan-tilt platform. The binocular tracking measurement unit and the pan-tilt platform are respectively connected to the computer for communication. The signal generator is respectively connected to the binocular tracking measurement unit and the computer for communication.

[0033] The beneficial effects of the present invention are: realizing real-time dynamic multi-point tracking measurement during continuous adjustment of the mold surface, the number and position of the dynamic tracking feature points are not limited, and the problem of lack of reference on the mold surface and inability to accurately measure errors is completely solved, and the mold adjustment efficiency and reliability are greatly improved. The method and device are low in cost, simple to operate, and easy to automate.

[0034] The present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Attached Figure 1 It is a schematic diagram of the structure of the device of the present invention.

[0036] In the attached drawings: 1. CCD image sensor, 2. CCD image sensor, 3. mounting bracket, 4. pan / tilt, 5. computer, 6. signal generator, 7. calibration plate, 8. circular marking point, 9. mold surface. DETAILED DESCRIPTION

[0037] A dynamic tracking measurement method for continuous adjustment of mold surface, which is based on the measurement images of a surface adjustment reference group A with a group of circular mark points and a surface adjustment target group B with a group of circular mark points collected by a binocular tracking measurement unit, and the dynamic tracking measurement method is realized by stereo matching the coordinates of the circular mark points in the extracted images with the design coordinate system of the mold to be measured. The dynamic tracking measurement method is realized by the following steps:

[0038] Step 1. Calibrate the binocular tracking measurement unit consisting of a pair of CCD image sensors according to the perspective projection imaging model.

[0039] Place the mold to be tested under the bracket on which the measuring device is installed, and adjust the binocular tracking measurement unit so that the mold is in the visible area of ​​the CCD image sensor.

[0040] Randomly fix m circular marking points on the edge positions of the rigid connections of the mold surface that needs to be adjusted, as the mold surface adjustment reference group A.

[0041] The profile adjustment reference group A is composed of m circular marking points. During the profile adjustment process of the mold, the profile adjustment reference group A is a fixed point that does not move in position and is used for the conversion between the profile coordinates of the mold to be measured obtained by the binocular tracking measurement unit and the design coordinates of the profile of the mold to be measured.

[0042] The surface adjustment target group B is composed of n circular marking points, wherein each marking point serves as a surface adjustment feature point and a measurement point in the process of surface adjustment. Since the surface adjustment is achieved by controlling the elastic deformation of a single-point or multi-point mold surface, the elastic deformation of the surface causes a linkage displacement of the multi-point positions of the surface adjustment target group B. Only by dynamically tracking and measuring all the displaced variables of the surface adjustment target group B can all of them meet the error requirements. The dynamic tracking measurement can also determine the surface adjustment feature points based on the positions of the surface adjustment target group B.

[0043] Step 2. Send a synchronization signal through the signal generator, use two CCD image sensors to capture the measurement image, and extract the image coordinates of the circular mark points for stereo matching to obtain the three-dimensional coordinates M of the centers of all the circular mark points of the profile adjustment reference group A and the profile adjustment target group B. i =(x i,y i ,z i ) and N k =(x k ,y k ,z k );

[0044] Where: 1≤i≤m, 1≤k≤n;

[0045] Step 3. Construct the three-dimensional covariance matrix COV(A) based on the coordinates of all circular markers of the reference group A according to the profile adjustment.

[0046]

[0047] in: The average value of m three-dimensional coordinates in the profile adjustment reference group A;

[0048] Step 4. Since the matrix of formula (1) above is a symmetric third-order square matrix, the covariance matrix can be decomposed into the following form using SVD decomposition;

[0049] COV(A)=USV -1 (2)

[0050] Among them, the matrix S is a diagonal matrix composed of eigenvalues ​​and is arranged in the order of ||λ1||≥||λ2||≥||λ3||, and V is the corresponding eigenvector matrix;

[0051]

[0052] Step 5. Take the cross product of vectors v1 and v2 and put them into vector v3, and normalize v1, v2 and v3 to get t1, t2 and t3;

[0053] by As the origin, an orthogonal coordinate system is established with t1, t2 and t3 as the x, y and z axes, where

[0054]

[0055] Step 6. According to the design coordinate system of the mold to be tested, calculate the translation vector T and the rotation matrix R between the above coordinate system and the above coordinate system;

[0056] Step 7. Use the above translation vector T and rotation matrix R to transform the three-dimensional coordinates of the midpoint of the target group B into the design coordinate system of the mold to be tested, and obtain the target position point The coordinate transformation relationship is:

[0057] P k =RN k +T (5)

[0058] Step 8. Calculate P using the closest point iteration algorithm k The best corresponding point Q on the surface of the mold to be tested k ;

[0059]

[0060] Step 9. Calculate P k With Q k The Euclidean distance between:

[0061]

[0062] Step 10. When d k When there is an error greater than the preset error e in the mold surface, the above steps are repeated during the mold surface adjustment process to achieve multi-point dynamic tracking measurement of the mold surface. k When it is less than the error e, the adjustment of the mold surface under the guidance of the dynamic tracking measurement results is completed.

[0063] A dynamic tracking measurement device for continuous adjustment of mold surface, comprising: a binocular tracking measurement unit consisting of a pair of CCD image sensors, a mounting bracket, a pan-tilt, a computer and a calibration plate, wherein the binocular tracking measurement unit is fixed to the mounting bracket through the pan-tilt, and the binocular tracking measurement unit and the pan-tilt are respectively communicated with the computer.

[0064] The device further comprises: a signal generator 6 and two groups of circular marking points 8;

[0065] The signal generator 6 is connected to a pair of CCD image sensors and a computer in the binocular tracking measurement unit for communication;

[0066] The two groups of circular marking points 8 are respectively fixed on the edge position of the rigid connection of the mold surface that needs to be adjusted and on the surface of the mold surface that needs to be adjusted.

[0067] When the measuring device is used, the CCD image sensor 1 and the CCD image sensor 2 in the binocular tracking measuring unit are calibrated through the calibration plate 7 .

[0068] The two groups of circular marking points 8 are respectively fixed on the edge position rigidly connected to the molding surface 9 to be adjusted and on the surface of the molding surface 9 to be adjusted.

[0069] A profile adjustment reference group A is composed of a group of circular marking points 8. During the profile adjustment process of the mold, the profile adjustment reference group A is a fixed point that does not move in position and is used to convert the profile coordinates of the mold to be measured obtained by the binocular tracking measurement unit with the design coordinates of the mold to be measured.

[0070] A group of circular marking points 8 constitutes a profile adjustment target group B, wherein each marking point serves as a profile adjustment feature point and a measurement point in the profile adjustment process. Since the profile adjustment is achieved by controlling the elastic deformation of a single-point or multi-point mold profile, the elastic deformation of the profile brings about a linkage displacement of multiple positions of the profile adjustment target group B. Only by dynamically tracking and measuring all displaced variables of the profile adjustment target group B can all of them meet the error requirements. The dynamic tracking measurement can also determine the profile adjustment feature points based on the positions of the profile adjustment target group B.

[0071] The computer of the measuring device uses the nearest point iteration algorithm to calculate the design target position point of the mold surface to be measured and the best corresponding point on the surface of the mold surface to be measured, and the Euclidean distance between the design point and the best corresponding point is adjusted to meet the design error requirements, thereby completing the adjustment of the mold surface under the guidance of the dynamic tracking measurement results.

Claims

1. A dynamic tracking measurement method for continuous adjustment of mold surface, which is based on the measurement images of a surface adjustment reference group A with a set of circular marker points and a surface adjustment target group B with a set of circular marker points collected by a binocular tracking measurement unit, and the dynamic tracking measurement method is realized by stereo matching the coordinates of the circular marker points in the extracted images with the design coordinate system of the mold to be measured, and is characterized by: The dynamic tracking measurement method is implemented by the following steps: Step 1. Calibrate the binocular tracking measurement unit composed of a pair of CCD image sensors according to the perspective projection imaging model; Place the mold to be tested under the bracket on which the measuring device is installed, and adjust the binocular tracking measurement unit so that the mold is in the visible area of ​​the CCD image sensor; Randomly fix m circular marking points on the edge positions of the rigid connection of the mold surface that needs to be adjusted, as the mold surface adjustment reference group A; At the same time, n circular marking points are randomly fixed on the mold surface that needs to be adjusted as the mold surface adjustment target group B; Step 2. Send a synchronization signal through the signal generator, use two CCD image sensors to capture the measurement image, and extract the image coordinates of the circular mark points for stereo matching to obtain the three-dimensional coordinates M of the centers of all circular mark points of the profile adjustment reference group A and the profile adjustment target group B. i =(x i ,y i ,z i ) and N k =(x k ,y k ,z k ); Where: 1≤i≤m, 1≤k≤n; Step 3. Construct the three-dimensional covariance matrix COV(A) based on the coordinates of all circular markers of the reference group A according to the profile adjustment. in: The average value of m three-dimensional coordinates in the profile adjustment reference group A; Step 4. Since the matrix of formula (1) above is a symmetric third-order square matrix, the covariance matrix can be decomposed into the following form using SVD decomposition; COV(A)=USV -1 (2) Among them, the matrix S is a diagonal matrix composed of eigenvalues ​​and is arranged in the order of λ1≥λ2≥λ3, and V is the corresponding eigenvector matrix; Step 5. Take the cross product of vectors v1 and v2 and put them into vector v3, and normalize v1, v2 and v3 to get t1, t2 and t3; by As the origin, an orthogonal coordinate system is established with t1, t2 and t3 as the x, y and z axes, where Step 6. According to the design coordinate system of the mold to be tested, calculate the translation vector T and the rotation matrix R between the above coordinate system and the above coordinate system; Step 7. Use the above translation vector T and rotation matrix R to transform the three-dimensional coordinates of the midpoint of the target group B into the design coordinate system of the mold to be tested, and obtain the target position point The coordinate transformation relationship is: P k =RN k +T (5) Step 8. Calculate P using the closest point iteration algorithm k The best corresponding point Q on the surface of the mold to be tested k ; Step 9. Calculate P k With Q k The Euclidean distance between: Step 10. When d k When there is an error greater than the preset error e in the mold surface, the control points of the mold surface repeat the above steps during the mold surface adjustment process to achieve multi-point dynamic tracking measurement of the mold surface. k When it is less than the error e, the tracking measurement ends.

2. According to claim 1, the measuring device of the dynamic tracking measuring method for continuous shaping of the mold surface comprises: A binocular tracking measurement unit consisting of a pair of CCD image sensors, a mounting bracket, a pan-tilt, a computer and a calibration plate, wherein the binocular tracking measurement unit is fixed to the mounting bracket through the pan-tilt, and the binocular tracking measurement unit and the pan-tilt are respectively connected to the computer for communication, characterized in that: The device further comprises: a signal generator 6 and two groups of circular marking points 8; The signal generator 6 is connected to a pair of CCD image sensors and a computer in the binocular tracking measurement unit for communication; The two groups of circular marking points 8 are respectively fixed on the edge position of the rigid connection of the mold surface that needs to be adjusted and on the surface of the mold surface that needs to be adjusted.

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