UVW platform calibration deviation correction method and system based on linear motor

Abstract

The invention relates to the technical field of coal UVW platform deviation rectification, in particular to a UVW platform calibration deviation rectification correction method and system based on a linear motor, and the method comprises the following steps: obtaining an affine transformation matrix used for conversion of a camera coordinate system and a UVW platform coordinate system through a 9-point calibration method; obtaining a rotation center of the UVW platform coordinate system by using a rotation calibration method, and performing error correction on the rotation center to obtain an optimal rotation center; and calculating the calibration deviation correction amount of the UVW platform based on the optimal rotation center by using a system equation of the UVW platform. In the rotation calibration process of the UVW platform deviation correction work, the deviation measuring and calculating model is constructed, correction of UVW platform calibration according to the calibration deviation can be achieved, a large amount of repeated rotation calibration operation can be avoided, the accurate rotation center can be obtained, and the UVW platform deviation correction accuracy and efficiency are improved.

Description

Technical Field

[0001] The invention relates to the technical field of UVW platform deviation correction, and in particular to a UVW platform calibration deviation correction method based on a linear motor. Background Art

[0002] ‌‌The UVW platform is a high-precision mobile platform designed for high-precision alignment equipment. ‌It is a three-axis parallel motion mechanism that realizes the linear motion of the X and Y axes and The main applications of UVW platforms include high-precision alignment functions in PCB and semiconductor industries such as exposure machines, screen printers, and laminating machines. The rotation principle of the UVW platform allows rotation around any point on the platform and translation in any direction. The control accuracy of this platform is higher than that of traditional The platform can achieve higher repeatability, generally up to ±1μm. The UVW platform is connected to the visual CCD correction system to quickly complete high-precision correction work.

[0003] At present, when using the UVW platform for correction work, the rotation center of the UVW platform is usually determined by rotation calibration. During the rotation calibration process, the UVW platform needs to be controlled to perform a large number of rotation operations to accurately determine the coordinates of the rotation center. However, it is difficult to completely exhaust the rotation operations in a true sense. Therefore, there will still be calibration deviations when the rotation center is calibrated by rotation. Moreover, even if the rotation operations are exhausted, the calibration process has too much workload and takes too long, which ultimately affects the accuracy and efficiency of the correction. Summary of the invention

[0004] The purpose of the present invention is to provide a UVW platform calibration and correction method and system based on a linear motor, so as to solve the technical problems in the prior art that the rotation center is still calibrated with a calibration deviation, the calibration process is too labor-intensive, the calibration time is too long, and ultimately affects the accuracy and efficiency of the correction.

[0005] In order to solve the above technical problems, the present invention specifically provides the following technical solutions: A UVW platform calibration and correction method based on a linear motor comprises the following steps: The affine transformation matrix for converting the camera coordinate system and the UVW platform coordinate system is obtained using the 9-point calibration method; The rotation center of the UVW platform coordinate system is obtained by using a rotation calibration method, and the error of the rotation center is corrected to obtain the optimal rotation center; The UVW platform calibration correction amount is calculated based on the optimal rotation center using the system formula of the UVW platform.

[0006] As a preferred solution of the present invention, a method for obtaining an affine transformation matrix for converting a camera coordinate system and a UVW platform coordinate system using a 9-point calibration method includes: ‌ Obtain a calibration plate including 9 specific points, wherein the physical coordinates of the specific points are known in the physical world of the calibration plate; Use a camera to shoot the calibration plate from different angles and record the image coordinates of these 9 specific points; ‌ Let the U, V and W axes of the UVW platform move to the corresponding 9 specific points on the calibration plate according to the predetermined mode, and record the UVW platform coordinates of these 9 specific points; Using the correspondence between the image coordinates and UVW platform coordinates of these 9 specific points, a transformation matrix describing the transformation relationship from the image coordinate system to the UVW platform coordinate system is calculated through the visual software Halcon. The conversion matrix is ​​used as the affine transformation matrix.

[0007] As a preferred solution of the present invention, a method for obtaining the rotation center of the UVW platform coordinate system using the rotation calibration method includes: Select a marker point, control the U, V and W axes in the UVW platform to perform multiple rotations, and obtain the coordinates and rotation angles of the marker point before and after multiple rotations; Using the calculation formula of the rotation center, multiple calibration coordinates of the rotation center of the UVW platform are calculated using the coordinates before and after multiple rotations and the rotation angles; The formula for calculating the center of rotation is: ; In the formula, For the landmark point i The rotation center of the UVW platform obtained by the rotation i The calibration coordinates, are the coordinates of the landmark points, For the landmark point i The coordinates after rotation are For the landmark point i The rotation angle of the second rotation.

[0008] As a preferred solution of the present invention, a method for performing error correction on the rotation center to obtain an optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center, wherein the calculation formula of the calibration deviation is: ; In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is subjected to BP neural network learning to obtain a deviation measurement model, wherein the deviation measurement model is: ; In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; The calibration coordinates of the rotation center with the smallest calibration deviation are selected as the coordinates of the optimal rotation center.

[0009] As a preferred solution of the present invention, a method for performing error correction on the rotation center to obtain an optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center, wherein the calculation formula of the calibration deviation is: ; In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is subjected to BP neural network learning to obtain a deviation measurement model, wherein the deviation measurement model is: ; In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; All possible values ​​of the calibrated coordinates of the rotation center are corrected using the calibration deviation to obtain the coordinates of the optimal rotation center, and the coordinates of the optimal rotation center are: .

[0010] As a preferred solution of the present invention, the calculation method of the UVW platform calibration correction amount includes: According to the affine transformation matrix between the camera coordinate system and the UVW platform coordinate system, the existing coordinates of the workpiece in the camera coordinate system are converted into the existing coordinates in the UVW platform coordinate system; According to the existing coordinates of the workpiece in the UVW platform coordinate system, the standard position coordinates of the workpiece in the UVW platform coordinate system, the coordinates of the optimal rotation center, and the initial coordinates of each of the three axes U, V and W in the UVW platform, the feed amounts ΔU, ΔV and ΔW of each of the three axes U, V and W in the UVW platform are calculated through the system formula of the UVW platform; ; ; ; In the formula, ΔU, ΔV and ΔW are the feed amounts of the three axes U, V and W in the UVW platform respectively. is the initial coordinate of the U axis in the UVW platform, is the initial coordinate of the V axis in the UVW platform, is the initial coordinate of the W axis in the UVW platform, are the coordinates of the optimal rotation center, is the existing coordinate of the workpiece in the UVW platform coordinate system. It is the standard position coordinate of the workpiece in the UVW platform coordinate system.

[0011] As a preferred solution of the present invention, the movement of the three axes U, V and W in the UVW platform is controlled according to the feed amounts ΔU, ΔV and ΔW of the three axes in the UVW platform to complete the workpiece correction.

[0012] As a preferred solution of the present invention, the present invention provides a UVW platform calibration, correction and correction system based on a linear motor, which is applied to the UVW platform calibration, correction and correction method based on a linear motor, and the system includes: A nine-point calibration unit, used for obtaining an affine transformation matrix for converting a camera coordinate system and a UVW platform coordinate system using a nine-point calibration method; A rotation calibration unit, used for obtaining the rotation center of the UVW platform coordinate system by using a rotation calibration method, and performing error correction on the rotation center to obtain an optimal rotation center; The deflection correction unit is used to calculate the deflection correction amount of the UVW platform based on the optimal rotation center by using the system formula of the UVW platform.

[0013] As a preferred solution of the present invention, the deflection correction amount output by the deflection correction unit is transmitted to the driver of the UVW platform through the PLC, and the driver of the UVW platform controls the movement of the UVW platform according to the deflection correction amount so that the workpiece reaches the standard position.

[0014] As a preferred solution of the present invention, the data input by the nine-point calibration unit is a calibration plate image captured by a camera.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In the rotation calibration process of the UVW platform correction work, the present invention constructs a deviation measurement model, which can realize the correction of the UVW platform calibration according to the calibration deviation, avoid a large number of repeated rotation calibration operations and obtain an accurate rotation center, thereby improving the accuracy and efficiency of the UVW platform correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0017] Figure 1 A flow chart of a UVW platform calibration and correction method provided in an embodiment of the present invention; Figure 2 A block diagram of a UVW platform calibration and correction system provided in an embodiment of the present invention; Figure 3 A schematic diagram of a nine-point calibration method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1As shown, the present invention provides a UVW platform calibration and correction method based on a linear motor, comprising the following steps: The affine transformation matrix for converting the camera coordinate system and the UVW platform coordinate system is obtained using the 9-point calibration method; The rotation center of the UVW platform coordinate system is obtained by using the rotation calibration method, and the error of the rotation center is corrected to obtain the optimal rotation center; The UVW platform calibration correction value is calculated based on the optimal rotation center using the system formula of the UVW platform.

[0020] In order to realize the deviation correction of the UVW platform, the present invention utilizes a 9-point calibration method and a rotation calibration method to complete the deviation correction calibration of the UVW platform, and then utilizes the UVW platform after the deviation correction calibration to realize the deviation correction of the workpiece, so that the workpiece moves to the standard position.

[0021] In order to improve the correction accuracy of the UVW platform, the present invention calibrates and corrects the rotation center of the UVW platform calibrated by the rotation calibration method, eliminates the calibration deviation of the rotation center, improves the calibration accuracy of the rotation center, and further improves the accuracy of workpiece correction achieved based on the high-precision rotation center, that is, improves the workpiece correction accuracy of the UVW platform.

[0022] In the calibration and correction of the rotation center of the UVW platform, the present invention adopts a deviation measurement model to learn the mapping relationship between the calibration coordinates of the rotation center and the calibration deviation, so as to realize the measurement of the calibration deviation of any calibration coordinates of the rotation center obtained by the rotation calibration method by using the deviation measurement model, so as to realize the measurement of the rotation calibration deviation by using the deep learning algorithm without the need for the UVW platform to perform actual correction rotation operation. Therefore, the calibration deviation of the rotation center is separated from a large number of repeated UVW platform operations, and a large amount of calibration correction time is not required, which improves the calibration correction speed of the rotation center, and obtains an accurate rotation center under efficient calibration correction, that is, obtains high accuracy of workpiece correction under efficient calibration correction, and the corresponding high efficiency of workpiece correction realizes high accuracy of workpiece correction.

[0023] Therefore, the present invention can maintain the calibration efficiency of the UVW platform, that is, the correction efficiency, while improving the correction accuracy of the UVW platform, so that the accuracy and efficiency of the two are taken into account together, breaking the contradiction between the two (high correction accuracy corresponds to inefficient correction caused by a large number of complex and repeated platform operations to correct the rotation center, and low correction accuracy corresponds to efficient correction caused by a small number of complex and repeated platform operations to correct the rotation center).

[0024] Specifically, when the present invention performs calibration and correction of the rotation center, first, a limited amount of UVW platform correction rotation operation is utilized, that is, a workpiece correction rotation operation is performed according to a limited amount of rotation center calibration coordinates, and the coordinates of the workpiece after the correction rotation are used to perform error calculation to obtain the calibration deviation of the rotation center, thereby obtaining a limited amount of rotation center calibration coordinates and calibration deviation, and obtaining a mapping relationship between the rotation center calibration coordinates and the calibration deviation through the mapping properties of the BP neural network, so that the calibration deviation can be modeled and calculated according to the rotation center calibration coordinates, that is, the calibration deviation of all possible values ​​of the rotation center calibration coordinates is calculated using a neural network, and the calibration deviation obtained by a limited amount of platform operation is expanded to an infinite amount of mathematically quantified calibration deviation, so that the calibration deviation is obtained by replacing the platform operation with a deviation measurement model, thereby avoiding a large number of complex and repetitive platform operations to correct the rotation center and improving the calibration correction efficiency.

[0025] Moreover, the present invention also provides two correction methods for the calibration and correction of the rotation center. One is "to sequentially calculate the deviations of all possible values ​​of the calibration coordinates of the rotation center through a deviation measurement model to obtain the calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; and to select the calibration coordinates of the rotation center with the minimum calibration deviation as the coordinates of the optimal rotation center." This method selects the optimal calibration of the rotation center according to the calibration deviation of the rotation center, so that the rotation center has the minimum calibration deviation, and thus minimizes the correction error obtained by the UVW platform using the rotation center for correction. It is a direct correction method.

[0026] The other is "to measure the deviation of all possible values ​​of the calibrated coordinates of the rotation center in sequence through the deviation measurement model to obtain the calibration deviations of all possible values ​​of the calibrated coordinates of the rotation center; and to correct all possible values ​​of the calibrated coordinates of the rotation center using the calibration deviation to obtain the coordinates of the optimal rotation center". This method combines the calibration deviation with the calibrated coordinates of the rotation center. The calibrated coordinates of the rotation center can be arbitrarily selected, and then the rotation center can be adjusted by the calibration deviation to obtain the optimal calibration of the selected center. The deviation of the calibrated coordinates of any rotation center can be eliminated, so that the rotation center after the deviation is eliminated is close to the real rotation center of the UVW platform, thereby minimizing the correction error obtained by the UVW platform using the rotation center after the deviation is eliminated. This is an indirect correction method.

[0027] Both of the above methods can be used, and users can choose according to actual needs.

[0028] The present invention utilizes the system formula of the UVW platform to calculate the calibration correction amount of the UVW platform based on the optimal rotation center, and controls the movement of the three axes U, V and W in the UVW platform to the standard position through the calibration correction amount of the UVW platform (the feed amount ΔU, ΔV and ΔW of each axis of the three axes U, V and W in the UVW platform), thereby completing the correction of the workpiece.

[0029] In order to realize the deviation correction of the UVW platform, the present invention uses the 9-point calibration method and the rotation calibration method to complete the deviation correction calibration of the UVW platform, and then uses the UVW platform after the deviation correction calibration to realize the deviation correction of the workpiece, so that the workpiece moves to the standard position, as follows: like Figure 3 As shown, the method of obtaining the affine transformation matrix for converting the camera coordinate system and the UVW platform coordinate system by using the 9-point calibration method includes: ‌Get a calibration plate containing 9 specific points, where the physical coordinates of the specific points are known in the physical world of the calibration plate; Use a camera to shoot the calibration plate from different angles and record the image coordinates of these 9 specific points; ‌ Let the U, V and W axes of the UVW platform move to the corresponding 9 specific points on the calibration plate according to the predetermined mode, and record the UVW platform coordinates of these 9 specific points; Using the correspondence between the image coordinates and UVW platform coordinates of these 9 specific points, a transformation matrix describing the transformation relationship from the image coordinate system to the UVW platform coordinate system is calculated through the visual software Halcon. Takes the transformation matrix as an affine transformation matrix.

[0030] In order to improve the correction accuracy of the UVW platform, the present invention calibrates and corrects the rotation center of the UVW platform calibrated by the rotation calibration method, eliminates the calibration deviation of the rotation center, improves the calibration accuracy of the rotation center, and further improves the accuracy of the workpiece correction achieved based on the high-precision rotation center, that is, improves the workpiece correction accuracy of the UVW platform, specifically as follows: The method of obtaining the rotation center of the UVW platform coordinate system using the rotation calibration method includes: Select a marker point, control the U, V and W axes in the UVW platform to perform multiple rotations, and obtain the coordinates and rotation angles of the marker point before and after multiple rotations; Using the calculation formula of the rotation center, multiple calibration coordinates of the rotation center of the UVW platform are calculated using the coordinates before and after multiple rotations and the rotation angles; The formula for calculating the center of rotation is: ; In the formula, For the landmark point iThe rotation center of the UVW platform obtained by the rotation i The calibration coordinates, are the coordinates of the landmark points, For the landmark point i The coordinates after rotation are For the landmark point i The rotation angle of the second rotation.

[0031] The method of performing error correction on the rotation center to obtain the optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center. The calculation formula of the calibration deviation is: ; In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is learned by BP neural network to obtain the deviation calculation model, where the deviation calculation model is: ; In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; In the calibration and correction of the rotation center of the UVW platform, the present invention adopts a deviation measurement model to learn the mapping relationship between the calibration coordinates of the rotation center and the calibration deviation, so as to realize the measurement of the calibration deviation of any calibration coordinates of the rotation center obtained by the rotation calibration method by using the deviation measurement model, so as to realize the measurement of the rotation calibration deviation by using the deep learning algorithm without the need for the UVW platform to perform actual correction rotation operation. Therefore, the calibration deviation of the rotation center is separated from a large number of repeated UVW platform operations, and a large amount of calibration correction time is not required, which improves the calibration correction speed of the rotation center, and obtains an accurate rotation center under efficient calibration correction, that is, obtains high accuracy of workpiece correction under efficient calibration correction, and the corresponding high efficiency of workpiece correction realizes high accuracy of workpiece correction.

[0032] All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; Select the calibration coordinates of the rotation center with the smallest calibration deviation as the coordinates of the optimal rotation center .

[0033] The method of performing error correction on the rotation center to obtain the optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center. The calculation formula of the calibration deviation is: ; In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is learned by BP neural network to obtain the deviation calculation model, where the deviation calculation model is: ; In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; All possible values ​​of the calibrated coordinates of the rotation center are corrected using the calibration deviation to obtain the coordinates of the optimal rotation center. The coordinates of the optimal rotation center are: .

[0034] The present invention can maintain the calibration efficiency of the UVW platform, that is, the efficiency of correction, while improving the correction accuracy of the UVW platform, so that both accuracy and efficiency can be taken into account, breaking the contradiction between the two (high correction accuracy corresponds to inefficient correction caused by a large number of complex and repeated platform operations to correct the rotation center, and low correction accuracy corresponds to efficient correction caused by a small number of complex and repeated platform operations to correct the rotation center).

[0035] Specifically, when the present invention performs calibration and correction of the rotation center, first, a limited amount of UVW platform correction rotation operation is utilized, that is, a workpiece correction rotation operation is performed according to a limited amount of rotation center calibration coordinates, and the coordinates of the workpiece after the correction rotation are used to perform error calculation to obtain the calibration deviation of the rotation center, thereby obtaining a limited amount of rotation center calibration coordinates and calibration deviation, and obtaining a mapping relationship between the rotation center calibration coordinates and the calibration deviation through the mapping properties of the BP neural network, so that the calibration deviation can be modeled and calculated according to the rotation center calibration coordinates, that is, the calibration deviation of all possible values ​​of the rotation center calibration coordinates is calculated using a neural network, and the calibration deviation obtained by a limited amount of platform operation is expanded to an infinite amount of mathematically quantified calibration deviation, so that the calibration deviation is obtained by replacing the platform operation with a deviation measurement model, thereby avoiding a large number of complex and repetitive platform operations to correct the rotation center and improving the calibration correction efficiency.

[0036] Moreover, the present invention also provides two correction methods for the calibration and correction of the rotation center. One is "to sequentially calculate the deviations of all possible values ​​of the calibration coordinates of the rotation center through a deviation measurement model to obtain the calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; and to select the calibration coordinates of the rotation center with the minimum calibration deviation as the coordinates of the optimal rotation center." This method selects the optimal calibration of the rotation center according to the calibration deviation of the rotation center, so that the rotation center has the minimum calibration deviation, and thus minimizes the correction error obtained by the UVW platform using the rotation center for correction. It is a direct correction method.

[0037] The other is "to measure the deviation of all possible values ​​of the calibrated coordinates of the rotation center in sequence through the deviation measurement model to obtain the calibration deviations of all possible values ​​of the calibrated coordinates of the rotation center; and to correct all possible values ​​of the calibrated coordinates of the rotation center using the calibration deviation to obtain the coordinates of the optimal rotation center". This method combines the calibration deviation with the calibrated coordinates of the rotation center. The calibrated coordinates of the rotation center can be arbitrarily selected, and then the rotation center can be adjusted by the calibration deviation to obtain the optimal calibration of the selected center. The deviation of the calibrated coordinates of any rotation center can be eliminated, so that the rotation center after the deviation is eliminated is close to the real rotation center of the UVW platform, thereby minimizing the correction error obtained by the UVW platform using the rotation center after the deviation is eliminated. This is an indirect correction method.

[0038] Both of the above methods can be used, and users can choose according to actual needs.

[0039] The calculation method of UVW platform calibration correction includes: According to the affine transformation matrix between the camera coordinate system and the UVW platform coordinate system, the existing coordinates of the workpiece in the camera coordinate system are converted into the existing coordinates in the UVW platform coordinate system; According to the existing coordinates of the workpiece in the UVW platform coordinate system, the standard position coordinates of the workpiece in the UVW platform coordinate system, the coordinates of the optimal rotation center, and the initial coordinates of each of the three axes U, V and W in the UVW platform, the feed amounts ΔU, ΔV and ΔW of each of the three axes U, V and W in the UVW platform are calculated through the system formula of the UVW platform; ; ; ; In the formula, ΔU, ΔV and ΔW are the feed amounts of the three axes U, V and W in the UVW platform respectively. is the initial coordinate of the U axis in the UVW platform, is the initial coordinate of the V axis in the UVW platform, is the initial coordinate of the W axis in the UVW platform, are the coordinates of the optimal rotation center, is the existing coordinate of the workpiece in the UVW platform coordinate system. It is the standard position coordinate of the workpiece in the UVW platform coordinate system.

[0040] The movement of the three axes U, V and W in the UVW platform is controlled according to the feed amounts ΔU, ΔV and ΔW of the three axes in the UVW platform to complete the deviation correction of the workpiece.

[0041] The U, V and W axes of the UVW platform are each moved by a linear motor.

[0042] The present invention provides a correction example, which is as follows: Center of rotation , , , .

[0043] Workpiece correction sequence A to B, calculate: U axis feed: ΔU=((67.5-10)*(sin(1+0)tan(1+0)+cos(1+0))+(20+(2+0)-(-59))*tan(1+0)+10+(1+ 0)-67.5)-((67.5-10)*(sin0tan0+cos0)+(20+0-(-59))*tan0+10+0-67.5)=2.4226mm; V-axis feed: ΔV=((67.5-20)*(sin(1+0)tan(1+0)+cos(1+0))+(-59-10-(1+0))*tan(1+0)+20+(2+ 0)-67.5)-((67.5-20)*(sin0tan0+cos0)+(-59-10-0)*tan0+20+0-67.5)=0.7853mm; W axis feed: ΔW=((67.5-20)*(sin(1+0)tan(1+0)+cos(1+0))+(59-10-(1+0))*tan(1+0)+20+(2+ 0)-67.5)-((67.5-20)*(sin0tan0+cos0)+(59-10-0)*tan0+20+0-67.5)=2.8451mm; Similarly, the workpiece correction sequence is B to C, U-axis feed: ΔU = -0.8452mm, V-axis feed: ΔV = -3.4787mm, W-axis feed: ΔW = -0.6408mm.

[0044] Table 2 Workpiece correction feed amount like Figure 2 As shown, the present invention provides a UVW platform calibration, correction and correction system based on a linear motor, which is applied to a UVW platform calibration, correction and correction method based on a linear motor. The system includes: A nine-point calibration unit, used for obtaining an affine transformation matrix for converting a camera coordinate system and a UVW platform coordinate system using a nine-point calibration method; A rotation calibration unit, used to obtain the rotation center of the UVW platform coordinate system by using a rotation calibration method, and to perform error correction on the rotation center to obtain an optimal rotation center; The deflection correction unit is used to calculate the deflection correction amount of the UVW platform based on the optimal rotation center by using the system formula of the UVW platform.

[0045] The deflection correction amount output by the deflection correction unit is transmitted to the driver of the UVW platform through the PLC, and the driver of the UVW platform controls the movement of the UVW platform according to the deflection correction amount so that the workpiece reaches the standard position.

[0046] The data input to the nine-point calibration unit is the calibration plate image captured by the camera.

[0047] In the rotation calibration process of the UVW platform correction work, the present invention constructs a deviation measurement model, which can realize the correction of the UVW platform calibration according to the calibration deviation, avoid a large number of repeated rotation calibration operations and obtain an accurate rotation center, thereby improving the accuracy and efficiency of the UVW platform correction.

[0048] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A UVW platform calibration and correction method based on a linear motor, characterized in that: The following steps are involved: The affine transformation matrix for converting the camera coordinate system and the UVW platform coordinate system is obtained using the 9-point calibration method; The rotation center of the UVW platform coordinate system is obtained by using a rotation calibration method, and the error of the rotation center is corrected to obtain the optimal rotation center; The UVW platform calibration correction amount is calculated based on the optimal rotation center using the system formula of the UVW platform.

2. According to claim 1, a UVW platform calibration and correction method based on a linear motor is characterized in that: The method of obtaining an affine transformation matrix for converting a camera coordinate system and a UVW platform coordinate system by using a 9-point calibration method includes: ‌ Obtain a calibration plate including 9 specific points, wherein the physical coordinates of the specific points are known in the physical world of the calibration plate; Use a camera to shoot the calibration plate from different angles and record the image coordinates of these 9 specific points; ‌ Let the U, V and W axes of the UVW platform move to the corresponding 9 specific points on the calibration plate according to the predetermined mode, and record the UVW platform coordinates of these 9 specific points; Using the correspondence between the image coordinates and UVW platform coordinates of these 9 specific points, a transformation matrix describing the transformation relationship from the image coordinate system to the UVW platform coordinate system is calculated through the visual software Halcon. The conversion matrix is ​​used as the affine transformation matrix.

3. The UVW platform calibration and correction method based on a linear motor according to claim 1 is characterized in that: The method of obtaining the rotation center of the UVW platform coordinate system using the rotation calibration method includes: Select a marker point, control the U, V and W axes in the UVW platform to perform multiple rotations, and obtain the coordinates and rotation angles of the marker point before and after multiple rotations; Using the calculation formula of the rotation center, multiple calibration coordinates of the rotation center of the UVW platform are calculated using the coordinates before and after multiple rotations and the rotation angles; The formula for calculating the center of rotation is: ； In the formula, For the landmark point i The rotation center of the UVW platform obtained by the rotation i The calibration coordinates, are the coordinates of the landmark points, For the landmark point i The coordinates after rotation are For the landmark point i The rotation angle of the second rotation.

4. The method for calibration and correction of a UVW platform based on a linear motor according to claim 3 is characterized in that: The method of performing error correction on the rotation center to obtain the optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center, wherein the calculation formula of the calibration deviation is: ； In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is subjected to BP neural network learning to obtain a deviation measurement model, wherein the deviation measurement model is: ； In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; The calibration coordinates of the rotation center with the smallest calibration deviation are selected as the coordinates of the optimal rotation center.

5. The method for calibration and correction of a UVW platform based on a linear motor according to claim 3 is characterized in that: The method of performing error correction on the rotation center to obtain the optimal rotation center includes: Using the calibrated coordinates of the rotation center, the workpiece is rotated to obtain the coordinates of the workpiece after the rotation; The error is calculated using the coordinates of the workpiece after the correction rotation to obtain the calibration deviation of the rotation center, wherein the calculation formula of the calibration deviation is: ； In the formula, The workpiece is based on the rotation center j The coordinates after the calibration coordinates are rotated for correction, The workpiece is based on the rotation center j The rotation angle of the calibration coordinates for correction rotation, The rotation center j The calibration deviation of the calibration coordinates; The mapping relationship between the calibrated coordinates of the rotation center and the calibrated deviation is subjected to BP neural network learning to obtain a deviation measurement model, wherein the deviation measurement model is: ； In the formula, is the calibration deviation, is the calibration coordinate of the rotation center, BP is the BP neural network; All possible values ​​of the calibration coordinates of the rotation center are sequentially measured for deviation through the deviation measurement model to obtain calibration deviations of all possible values ​​of the calibration coordinates of the rotation center; All possible values ​​of the calibrated coordinates of the rotation center are corrected using the calibration deviation to obtain the coordinates of the optimal rotation center, and the coordinates of the optimal rotation center are: .

6. The method for calibration and correction of a UVW platform based on a linear motor according to claim 1, characterized in that: The calculation method of UVW platform calibration correction includes: According to the affine transformation matrix between the camera coordinate system and the UVW platform coordinate system, the existing coordinates of the workpiece in the camera coordinate system are converted into the existing coordinates in the UVW platform coordinate system; According to the existing coordinates of the workpiece in the UVW platform coordinate system, the standard position coordinates of the workpiece in the UVW platform coordinate system, the coordinates of the optimal rotation center, and the initial coordinates of each of the three axes U, V and W in the UVW platform, the feed amounts ΔU, ΔV and ΔW of each of the three axes U, V and W in the UVW platform are calculated through the system formula of the UVW platform; ； ； ； In the formula, ΔU, ΔV and ΔW are the feed amounts of the three axes U, V and W in the UVW platform respectively. is the initial coordinate of the U axis in the UVW platform, is the initial coordinate of the V axis in the UVW platform, is the initial coordinate of the W axis in the UVW platform, are the coordinates of the optimal rotation center, is the existing coordinate of the workpiece in the UVW platform coordinate system. It is the standard position coordinate of the workpiece in the UVW platform coordinate system.

7. The method for calibration and correction of a UVW platform based on a linear motor according to claim 6 is characterized in that: The movement of the three axes U, V and W in the UVW platform is controlled according to the feed amounts ΔU, ΔV and ΔW of the three axes in the UVW platform to complete the deviation correction of the workpiece.

8. A UVW platform calibration and correction system based on linear motor, characterized in that: A UVW platform calibration and correction method based on a linear motor as described in any one of claims 1 to 7, the system comprising: A nine-point calibration unit, used for obtaining an affine transformation matrix for converting a camera coordinate system and a UVW platform coordinate system using a nine-point calibration method; A rotation calibration unit, used for obtaining the rotation center of the UVW platform coordinate system by using a rotation calibration method, and performing error correction on the rotation center to obtain an optimal rotation center; The deflection correction unit is used to calculate the deflection correction amount of the UVW platform based on the optimal rotation center by using the system formula of the UVW platform.

9. The UVW platform calibration and correction system based on linear motor according to claim 8, characterized in that: The deflection correction amount output by the deflection correction unit is transmitted to the driver of the UVW platform through the PLC, and the driver of the UVW platform controls the movement of the UVW platform according to the deflection correction amount so that the workpiece reaches the standard position.

10. The UVW platform calibration and correction system based on linear motor according to claim 8, characterized in that: The data input to the nine-point calibration unit is the calibration plate image captured by the camera.

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