A motion platform error correction method and computer program product

Abstract

A motion platform error correction method and a computer program product, the motion platform comprising a first motion axis and a second motion axis, the motion platform error correction method comprising: acquiring a to-be-input theoretical position coordinate of the motion platform; correcting the to-be-input theoretical position coordinate based on an orthogonality error between the first motion axis and the second motion axis to obtain a position coordinate after correction of the orthogonality error; and determining a positioning error of the first motion axis and a positioning error of the second motion axis based on the position coordinate after correction of the orthogonality error, so as to correct the position coordinate after correction of the orthogonality error by the positioning error to obtain a target position coordinate. The technical problem of low precision of the existing motion platform error correction method is solved.

Description

Technical Field

[0001] This invention relates to the field of machine vision technology, specifically to a motion platform error correction method and computer program product. Background Technology

[0002] In the inspection of plate-shaped workpieces (such as tiles, wafers, and chipsets), the field of view and measurement range of a single camera often cannot cover the entire object being measured. Industrially, fixed-shot or flying-shot methods are commonly used, where the camera moves along a trajectory to capture images of the entire object. Due to systematic errors such as mechanical manufacturing assembly, guide rail errors, or motor operating accuracy, there are discrepancies between the theoretical position coordinates input to the motion platform's controller and the actual position coordinates of the motion platform. Therefore, it is necessary to correct or compensate for these errors to improve the positioning accuracy of the motion platform. Summary of the Invention

[0003] The main technical problem solved by this invention is that the accuracy of existing motion platform error correction methods is low.

[0004] According to a first aspect, one embodiment provides a motion platform error correction method, the motion platform including a first motion axis and a second motion axis, the motion platform error correction method comprising:

[0005] Obtain the theoretical position coordinates of the motion platform to be input;

[0006] The theoretical position coordinates to be input are corrected based on the orthogonality error between the first motion axis and the second motion axis to obtain the position coordinates after correction of the orthogonality error;

[0007] Based on the position coordinates after correcting the orthogonality error, the positioning error of the corresponding first motion axis and the positioning error of the second motion axis are determined, so as to correct the positioning error of the position coordinates after correcting the orthogonality error and obtain the target position coordinates.

[0008] In some embodiments, the position coordinates after correcting for orthogonality errors are determined by the following formula:

[0009]

[0010]

[0011] in, This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical and actual directions of the first motion axis. The theoretical direction of the first motion axis is orthogonal to the second motion axis. This error angle is used to characterize the orthogonality error between the first and second motion axes. This represents the theoretical position coordinates to be input.

[0012] In some embodiments, the error angle between the theoretical direction and the actual direction of the first motion axis is calculated by the following method:

[0013] Starting from the origin of the motion platform, samples are taken on the first motion axis and the second motion axis respectively to obtain multiple sampling points on the first motion axis and multiple sampling points on the second motion axis;

[0014] A first fitted line is calculated based on multiple sampling points of the first motion axis, and a first direction vector is calculated based on the first fitted line;

[0015] A second fitted line is calculated based on multiple sampling points of the second motion axis, and a second direction vector is calculated based on the second fitted line;

[0016] Calculate the vector angle between the first direction vector and the second direction vector, and calculate the error angle between the theoretical direction and the actual direction of the first motion axis based on the vector angle.

[0017] In some embodiments, the error angle is determined by the following formula:

[0018]

[0019] in, Indicates the included angle of error. This represents the angle between the vectors.

[0020] In some embodiments, after correcting the positioning error of the position coordinates after correcting the orthogonality error, the motion platform error correction method further includes:

[0021] Based on the position coordinates after correcting the orthogonality error, the vertical error of the corresponding first motion axis and the vertical error of the second motion axis are determined; wherein, the vertical error of the first motion axis is the position error in the direction perpendicular to the actual direction of the first motion axis, and the vertical error of the second motion axis is the position error in the direction perpendicular to the actual direction of the second motion axis.

[0022] Based on the vertical errors of the first and second motion axes, the coupling errors of the first and second motion axes are calculated to correct the coupling errors of the target position coordinates, thus obtaining the final corrected target position coordinates.

[0023] In some embodiments, the coupling error of the first motion axis is determined by the following formula:

[0024]

[0025] in, This represents the coupling error of the first motion axis. This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical direction and the actual direction of the first motion axis. This represents the vertical error of the first motion axis. This indicates the vertical error of the second motion axis;

[0026] The coupling error of the second motion axis is determined by the following formula:

[0027]

[0028] in, This represents the coupling error of the second motion axis. This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical direction and the actual direction of the first motion axis. This represents the vertical error of the first motion axis. This indicates the vertical error of the second motion axis.

[0029] In some embodiments, the final corrected target position coordinates are determined by the following formula:

[0030]

[0031]

[0032] in, This represents the final corrected target position coordinates. This represents the position coordinates after correcting for the orthogonality error. This indicates the positioning error of the first motion axis. This indicates the positioning error of the second motion axis. This represents the coupling error of the first motion axis. This represents the coupling error of the second motion axis. This represents the error angle between the theoretical direction and the actual direction of the first motion axis.

[0033] In some embodiments, the positioning errors of the first motion axis and the second motion axis are calculated by pre-constructed first positioning error fitting curve and second positioning error fitting curve, respectively, and the vertical errors of the first motion axis and the second motion axis are calculated by pre-constructed first vertical error fitting curve and second vertical error fitting curve, respectively.

[0034] In some embodiments, the method for constructing the first positioning error fitting curve and the first vertical error fitting curve includes:

[0035] Starting from the origin of the motion platform, samples are taken on the first motion axis to obtain multiple sampling points on the first motion axis;

[0036] Obtain the theoretical and measured position coordinates of each sampling point;

[0037] The first fitted line is calculated based on the actual position coordinates of multiple sampling points of the first motion axis, and the first direction vector is calculated based on the first fitted line.

[0038] For each sampling point, calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the first direction vector to obtain the positioning error of each sampling point on the first motion axis. Calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the vertical direction of the first direction vector to obtain the vertical error of each sampling point on the first motion axis.

[0039] A first positioning error fitting curve is constructed based on the positioning error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point; a first vertical error fitting curve is constructed based on the vertical error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point.

[0040] The methods for constructing the second positioning error fitting curve and the second vertical error fitting curve include:

[0041] Starting from the origin of the motion platform, samples are taken on the second motion axis to obtain multiple sampling points on the second motion axis;

[0042] Obtain the theoretical and measured position coordinates of each sampling point;

[0043] The second fitted line is calculated based on the actual position coordinates of multiple sampling points of the second motion axis, and the second direction vector is calculated based on the second fitted line;

[0044] For each sampling point, calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the second direction vector to obtain the positioning error of each sampling point on the second motion axis. Calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the vertical direction of the second direction vector to obtain the vertical error of each sampling point on the second motion axis.

[0045] A second positioning error fitting curve is constructed based on the positioning error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point. A second vertical error fitting curve is constructed based on the vertical error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point.

[0046] According to a second aspect, one embodiment provides a computer program product including a computer program and / or instructions, which, when executed by a processor, implement the motion platform error correction method.

[0047] According to the motion platform error correction method and computer program product of the above embodiments, the theoretical position coordinates to be input of the motion platform are corrected based on the orthogonality error between the first and second motion axes of the motion platform to obtain the position coordinates after orthogonality error correction. Based on the position coordinates after orthogonality error correction, the positioning error of the corresponding first motion axis and the positioning error of the second motion axis are determined to correct the positioning error of the position coordinates after orthogonality error correction to obtain the target position coordinates. This means that not only the positioning error of the motion axis is considered during correction, but also the orthogonality error between the motion axes. Therefore, covering different error sources and correcting the motion platform can improve the accuracy of motion platform correction. Attached Figure Description

[0048] Figure 1 This is a flowchart of the motion platform error correction method in the embodiments of this application;

[0049] Figure 2 This is a schematic diagram of orthogonality error in one embodiment;

[0050] Figure 3 This is a schematic diagram illustrating positioning error and vertical error in one embodiment;

[0051] Figure 4 This is a schematic diagram of positioning error and vertical error in another embodiment;

[0052] Figure 5 This is a flowchart illustrating a method for calculating the error angle between the theoretical and actual directions of the first motion axis in one embodiment.

[0053] Figure 6 A flowchart of a motion platform error correction method in another embodiment;

[0054] Figure 7 This is a schematic diagram of coupling error in one embodiment;

[0055] Figure 8 This is a flowchart illustrating a method for constructing a first positioning error fitting curve and a first vertical error fitting curve in one embodiment. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0057] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0058] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0059] Currently, error correction methods for two-dimensional motion platforms typically involve measuring the actual position coordinates of the motion platform using a laser interferometer or a linear ruler. Based on these actual coordinates and the theoretical position coordinates input by the motion platform controller, error compensation using vision and calibration plates, regional compensation, or calculation of the error between the theoretical and actual positions along the motion direction are employed to correct or compensate for the error. In practical applications, vision and calibration plate compensation first requires establishing the relationship between the camera coordinate system and the motion platform coordinate system by combining the camera's image position coordinates. However, the camera's image position coordinates themselves may have positioning accuracy errors and deflection angles between the camera and the motion axis. Furthermore, large-area calibration plates may have manufacturing accuracy errors, and factors such as whether the calibration plate plane is coplanar with the object being measured and camera focusing need to be considered. This process is cumbersome and prone to error accumulation. Regional compensation typically involves error compensation using two-dimensional affine transformations. This requires sampling over the entire motion stroke and dividing the sampling point coordinates into regions. Each sub-region is solved using point-to-point affine transformations, requiring the preservation of multiple matrix transformation relationships and the specification of the sub-region boundary points. Motion direction error compensation usually involves calculating the positioning error between the theoretical position coordinates and the actual position coordinates in the motion direction, without considering the orthogonality error of the motion axis, and then calculating the compensation value for each point.

[0060] Based on the above analysis, the relevant technologies have the following main problems: (1) High computational complexity: Traditional error compensation methods usually require the use of checkerboard calibration boards or other feature arrays to calibrate the external parameters of the camera and motion platform. This is not only cumbersome to operate, but may also lead to error accumulation, making it difficult to implement quickly on the production site. (2) High memory usage: Calculating the position coordinate compensation table or coordinate affine transformation matrix by region requires storing the coordinate compensation table or a large number of compensation matrices. (3) Failure to consider error sources: Most existing calibration objects only consider the positioning error of the position coordinates, without considering factors such as the orthogonality error between the X-axis and Y-axis of the motion platform.

[0061] To address the aforementioned issues, this application provides a motion platform error correction method. The motion platform includes a first motion axis and a second motion axis. In the motion platform error correction method, the theoretical position coordinates to be input of the motion platform are obtained; the theoretical position coordinates to be input are corrected based on the orthogonality error between the first and second motion axes to obtain the position coordinates after orthogonality error correction; the positioning errors of the corresponding first and second motion axes are determined based on the position coordinates after orthogonality error correction to correct the positioning error of the position coordinates after orthogonality error correction, thereby obtaining the target position coordinates.

[0062] The motion platform error correction method provided in the embodiments of this application is described below with reference to the accompanying drawings.

[0063] Figure 1A flowchart of a motion platform error correction method provided in an embodiment of this application is shown, which will be described in detail below.

[0064] Step S10: Obtain the theoretical position coordinates of the motion platform to be input.

[0065] In some embodiments, the theoretical position coordinates of the motion platform to be input are first obtained. These theoretical position coordinates are the theoretical position of the motion platform in the direction of motion. In practical applications, there is often an error between the theoretical position and the actual position of the motion platform. Therefore, it is necessary to correct the error of the theoretical position coordinates to be input in order to correct and compensate for the positioning accuracy.

[0066] Step S20: Correct the theoretical position coordinates to be input based on the orthogonality error between the first motion axis and the second motion axis to obtain the position coordinates after correcting the orthogonality error.

[0067] In some embodiments, the motion platform includes a first motion axis and a second motion axis, wherein the first motion axis is the X-axis and the second motion axis is the Y-axis, or the first motion axis is the Y-axis and the second motion axis is the X-axis. The subsequent description in this application will be based on the scenario where the first motion axis is the X-axis and the second motion axis is the Y-axis. There is a non-ideal orthogonality between the first and second motion axes of the motion platform; that is, there is a deflection angle between the first and second motion axes, resulting in an orthogonality error in the motion platform. Therefore, it is necessary to correct the theoretical position coordinates to be input based on the orthogonality error between the first and second motion axes to obtain the position coordinates after orthogonality error correction.

[0068] Please refer to Figure 2 In some embodiments, the theoretical direction of the first motion axis is orthogonal to the second motion axis, but the actual direction of the first motion axis is not ideally orthogonal to the second motion axis. Therefore, the error angle between the theoretical and actual directions of the first motion axis can be utilized. Characterizing the orthogonality error between the first and second motion axes. This represents the theoretical position coordinates to be input, while This represents the position coordinates after correcting for orthogonality errors.

[0069] Step S30: Based on the position coordinates after correcting the orthogonality error, determine the positioning error of the corresponding first motion axis and the positioning error of the second motion axis, so as to correct the positioning error of the position coordinates after correcting the orthogonality error and obtain the target position coordinates.

[0070] In some embodiments, positioning error refers to the deviation between the actual position coordinates reached by the motion axis and the theoretical position coordinates to be input. This error reflects the positioning accuracy of the motion axis. Therefore, after obtaining the position coordinates after correcting for orthogonality error, the positioning errors of the corresponding first motion axis and the second motion axis are determined based on the position coordinates after correcting for orthogonality error, so as to correct the positioning error of the position coordinates after correcting for orthogonality error and obtain the target position coordinates.

[0071] Please refer to Figure 3 and Figure 4 In some embodiments, and All of these are the theoretical position coordinates to be input. and All coordinates are the actual positions reached. When calculating the positioning error of the first motion axis, the first motion axis is used as the reference axis, and the difference in the actual direction of the first motion axis is calculated as the positioning error of the first motion axis. When calculating the positioning error of the second motion axis, the second motion axis is used as the reference axis, and the difference in the actual direction of the second motion axis is calculated as the positioning error of the second motion axis. .

[0072] According to the motion platform error correction method of the above embodiment, the theoretical position coordinates to be input of the motion platform are corrected based on the orthogonality error between the first and second motion axes of the motion platform to obtain the position coordinates after orthogonality error correction. Based on the position coordinates after orthogonality error correction, the positioning error of the corresponding first motion axis and the positioning error of the second motion axis are determined to correct the positioning error of the position coordinates after orthogonality error correction to obtain the target position coordinates. This means that not only the positioning error of the motion axis is considered during correction, but also the orthogonality error between the motion axes. Therefore, covering different error sources and correcting the motion platform can improve the accuracy of motion platform correction.

[0073] Please return to the reference. Figure 2 In some embodiments, the position coordinates after correcting for orthogonality errors are determined using the following formula:

[0074]

[0075]

[0076] Please refer to Figure 5 In some embodiments, the error angle between the theoretical direction and the actual direction of the first motion axis is calculated by the following method, including steps S21 to S24, which are described in detail below.

[0077] Step S21: Starting from the origin of the motion platform, sample on the first motion axis and the second motion axis respectively to obtain multiple sampling points of the first motion axis and multiple sampling points of the second motion axis.

[0078] In some embodiments, the sampling interval is set according to the maximum stroke of the motion platform. For example, a sampling point is marked every 5 mm. Sampling is performed on the first and second motion axes starting from the origin of the motion platform. The sampling points need to cover the maximum stroke of the motion platform. n sampling points on the first motion axis are recorded. The m sampling points of the second motion axis are The sampling interval can be set according to the required accuracy of the correction, and is not limited here.

[0079] Step S22: Calculate the first fitted line based on multiple sampling points of the first motion axis, and calculate the first direction vector based on the first fitted line.

[0080] In some embodiments, the least squares method can be used to calculate the first fitted line. For example, the first fitted line can be constructed as ax + by + c = 0. An objective function is constructed with the goal of minimizing the distances from multiple sampling points to the constructed first fitted line, and the specific values ​​of a, b, and c are calculated to obtain the first fitted line. After obtaining the first fitted line, the angle between the first fitted line and the first motion axis can be obtained through the direction of the first fitted line. According to the included angle The first direction vector can be calculated as (cos sin Alternatively, it can be calculated based on a and b on the first fitted line, and the first direction vector can also be represented as (b, -a).

[0081] Step S23: Calculate the second fitted line based on multiple sampling points of the second motion axis, and calculate the second direction vector based on the second fitted line.

[0082] In some embodiments, the process of calculating the second fitted line and the second direction vector can refer to the calculation process of the first fitted line and the first direction vector in step S22, and will not be repeated here.

[0083] Step S24: Calculate the vector angle between the first direction vector and the second direction vector, and calculate the error angle between the theoretical direction and the actual direction of the first motion axis based on the vector angle.

[0084] In some embodiments, the expression for the vector angle between the first direction vector and the second direction vector is: ,in, Represents the first direction vector. This represents the second direction vector. Ideally, the first and second motion axes are orthogonal, and the angle between them should be... Therefore, according to The error angle between the theoretical and actual directions of the first motion axis is calculated by the angle between the vectors.

[0085] In some embodiments, the error angle is determined by the following formula:

[0086]

[0087] in, Indicates the error angle. This represents the angle between vectors.

[0088] Please refer to Figure 6 In some embodiments, after step S30: correcting the positioning error of the position coordinates after correcting the orthogonality error, the motion platform error correction method further includes steps S40 to S50, which are described in detail below.

[0089] Step S40: Determine the vertical error of the first motion axis and the vertical error of the second motion axis based on the position coordinates after correcting the orthogonality error.

[0090] In some embodiments, the vertical error of the first motion axis is the position error in the direction perpendicular to the actual direction of the first motion axis, and the vertical error of the second motion axis is the position error in the direction perpendicular to the actual direction of the second motion axis.

[0091] Please return to the reference. Figure 3 and Figure 4 In some embodiments, and All of these are the theoretical position coordinates to be input. and All coordinates are actual position coordinates, and the vertical error of the first motion axis is... The vertical error of the second motion axis is .

[0092] In some embodiments, sampling points in the same direction may not be on an ideal straight line, thus, errors may exist in the vertical direction. Generally, the vertical error will be less than the positioning error of the motion axis and close to zero. This is because the vertical error is essentially the vertical distance from the actual sampling point to the direction of the motion axis. In practical applications, the straightness of the motion guide rail affects the vertical error. During manufacturing, the motion guide rail can be made as straight as possible. The motion error in the axial direction is affected by system errors such as motor drive accuracy, which cannot be guaranteed at the manufacturing level.

[0093] Step S50: Calculate the coupling error of the first motion axis and the coupling error of the second motion axis based on the vertical error of the first motion axis and the vertical error of the second motion axis, so as to correct the coupling error of the target position coordinates and obtain the final corrected target position coordinates.

[0094] In some embodiments, after calculating the vertical error of the first motion axis and the vertical error of the second motion axis, the influence of the vertical error of the first motion axis on the directional movement of the second motion axis is considered to calculate the coupling error of the first motion axis, and the influence of the vertical error of the second motion axis on the directional movement of the first motion axis is considered to calculate the coupling error of the second motion axis. The coupling error is then corrected on the target position coordinates to obtain the final corrected target position coordinates.

[0095] Please refer to Figure 7 In some embodiments, the vertical error of the first motion axis The displacement projected onto the actual direction of the first motion axis is The displacement projected onto the actual direction of the second motion axis is The vertical error of the second motion axis The displacement projected onto the actual direction of the first motion axis is The displacement projected onto the actual direction of the second motion axis is The coupling error of the first motion axis is determined by the following formula:

[0096]

[0097] in, This represents the coupling error of the first motion axis. This represents the position coordinates after correcting for orthogonality errors. This represents the error angle between the theoretical and actual directions of the first motion axis. This indicates the vertical error of the first motion axis. This indicates the vertical error of the second motion axis;

[0098] The coupling error of the second motion axis is determined by the following formula:

[0099]

[0100] Among them, This represents the coupling error of the second motion axis. This represents the position coordinates after correcting for orthogonality errors. This represents the error angle between the theoretical and actual directions of the first motion axis. This indicates the vertical error of the first motion axis. This indicates the vertical error of the second motion axis.

[0101] In some embodiments, if the on-site implementation conditions result in only one-dimensional position errors on the first and second motion axes being measurable, then the coupling error can be disregarded and considered as zero.

[0102] In some embodiments, the final corrected target position coordinates are determined by the following formula:

[0103]

[0104]

[0105] in, This represents the final corrected target position coordinates. This represents the position coordinates after correcting for orthogonality errors. This indicates the positioning error of the first motion axis. This indicates the positioning error of the second motion axis. This represents the coupling error of the first motion axis. This represents the coupling error of the second motion axis. This represents the error angle between the theoretical direction and the actual direction of the first motion axis.

[0106] In some embodiments, the positioning error of the first motion axis and the positioning error of the second motion axis are calculated by pre-constructed first positioning error fitting curve and second positioning error fitting curve, respectively, and the vertical error of the first motion axis and the vertical error of the second motion axis are calculated by pre-constructed first vertical error fitting curve and second vertical error fitting curve, respectively.

[0107] Please refer to Figure 8 In some embodiments, the method for constructing the first positioning error fitting curve and the first vertical error fitting curve includes steps S31 to S35, which are described in detail below.

[0108] Step S31: Starting from the origin of the motion platform, sample on the first motion axis to obtain multiple sampling points on the first motion axis.

[0109] Step S32: Obtain the theoretical position coordinates and the measured actual position coordinates of each sampling point.

[0110] In some embodiments, the actual position coordinates of each sampling point are obtained using a laser interferometer or a line ruler based on the maximum travel of the motion platform and the sampling interval.

[0111] Step S33: Calculate the first fitted line based on the actual position coordinates of multiple sampling points of the first motion axis, and calculate the first direction vector based on the first fitted line.

[0112] In some embodiments, the calculation method of steps S21 to S24 is used to calculate the first fitted line and the first direction vector in step S33, which will not be described again here.

[0113] Step S34: For each sampling point, calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point on the first direction vector to obtain the positioning error of each sampling point on the first motion axis. Calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the perpendicular direction of the first direction vector to obtain the vertical error of each sampling point on the first motion axis.

[0114] Step S35: Construct a first positioning error fitting curve based on the positioning error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point; construct a first vertical error fitting curve based on the vertical error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point.

[0115] In some embodiments, the first positioning error fitting curve fits the curve of the theoretical position coordinates of the sampling points under the entire stroke of the motion platform versus the positioning error of the sampling points on the first motion axis. Considering that in actual operation, the position of the camera when taking pictures may not fall into multiple sampling points, when the position of the camera does not fall into a sampling point, the positioning error at the current position can be calculated by the first positioning error fitting curve. The same applies to the first vertical error fitting curve. A fifth-order polynomial can be used. To fit the positioning error and vertical error, x represents the theoretical position coordinates of the sampling point. This indicates the positioning error or vertical error of the sampling point on the motion axis.

[0116] In some embodiments, the method for constructing the second positioning error fitting curve and the second vertical error fitting curve includes:

[0117] Starting from the origin of the motion platform, samples are taken on the second motion axis to obtain multiple sampling points on the second motion axis;

[0118] Obtain the theoretical and measured position coordinates of each sampling point;

[0119] The second fitted line is calculated based on the actual position coordinates of multiple sampling points on the second motion axis, and the second direction vector is calculated based on the second fitted line.

[0120] For each sampling point, calculate the difference between the actual position coordinates and the theoretical position coordinates of the sampling point on the second direction vector to obtain the positioning error of each sampling point on the second motion axis. Calculate the difference between the actual position coordinates and the theoretical position coordinates of the sampling point in the perpendicular direction of the second direction vector to obtain the vertical error of each sampling point on the second motion axis.

[0121] A second positioning error fitting curve is constructed based on the positioning error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point. A second vertical error fitting curve is constructed based on the vertical error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point.

[0122] In some embodiments, the method for constructing the second positioning error fitting curve and the second vertical error fitting curve can refer to the method for constructing the first positioning error fitting curve and the first vertical error fitting curve, and will not be repeated here.

[0123] This application's motion platform error correction method addresses the problems of known error correction methods by considering the impact of different error sources on positioning accuracy and calculating the corrected position of the motion platform. Currently, in the precision machining of actual plate-shaped workpieces, it is necessary to use cameras to capture local areas of the product through either fixed-position or rapid-motion photography. Due to various system errors such as guide rail accuracy and motor accuracy, the motion platform's movement position will have a certain degree of offset, thus requiring motion accuracy error compensation. This method considers the orthogonality error and coupling error between motion axes while calculating the positioning error, making it applicable to single-axis or dual-axis positioning accuracy error correction. Compared to similar correction methods, the motion platform error correction method proposed in this application, which combines multiple error sources, achieves positioning accuracy error correction of the motion platform with convenient calculation, low storage requirements, and high efficiency. Therefore, it is applicable to both fixed-position and rapid-motion photography of large plate-shaped products, facilitating subsequent measurement and inspection. Meanwhile, compared with the current technology, this application has the following advantages: (1) Applicability: It can be used for single-axis or dual-axis error compensation of two-dimensional motion platforms, and the coupling error can be calculated according to the actual accuracy requirements; (2) Efficiency: It does not require calibration between the camera and the motion platform, there is no accumulation of visual compensation error, and it does not require storing the error compensation matrix of each region. It only needs to store the coefficients of the model function.

[0124] One embodiment provides a computer program product, including a computer program and / or instructions, which, when executed by a processor, implement a motion platform error correction method.

[0125] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.

[0126] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for correcting errors in a motion platform, wherein the motion platform includes a first motion axis and a second motion axis, characterized in that, The motion platform error correction method includes: Obtain the theoretical position coordinates of the motion platform to be input; The theoretical position coordinates to be input are corrected based on the orthogonality error between the first motion axis and the second motion axis to obtain the position coordinates after correction of the orthogonality error; Based on the position coordinates after correcting the orthogonality error, the positioning error of the corresponding first motion axis and the positioning error of the second motion axis are determined, so as to correct the positioning error of the position coordinates after correcting the orthogonality error and obtain the target position coordinates.

2. The motion platform error correction method as described in claim 1, characterized in that, The position coordinates after correcting for orthogonality error are determined by the following formula: in, This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical and actual directions of the first motion axis. The theoretical direction of the first motion axis is orthogonal to the second motion axis. This error angle is used to characterize the orthogonality error between the first and second motion axes. This represents the theoretical position coordinates to be input.

3. The motion platform error correction method as described in claim 2, characterized in that, The error angle between the theoretical direction and the actual direction of the first motion axis is calculated using the following method: Starting from the origin of the motion platform, samples are taken on the first motion axis and the second motion axis respectively to obtain multiple sampling points on the first motion axis and multiple sampling points on the second motion axis; A first fitted line is calculated based on multiple sampling points of the first motion axis, and a first direction vector is calculated based on the first fitted line; A second fitted line is calculated based on multiple sampling points of the second motion axis, and a second direction vector is calculated based on the second fitted line; Calculate the vector angle between the first direction vector and the second direction vector, and calculate the error angle between the theoretical direction and the actual direction of the first motion axis based on the vector angle.

4. The motion platform error correction method as described in claim 3, characterized in that, The error angle is determined by the following formula: in, Indicates the included angle of error. This represents the angle between the vectors.

5. The motion platform error correction method as described in claim 1, characterized in that, After correcting the positioning error of the position coordinates after correcting the orthogonality error, the motion platform error correction method further includes: Based on the position coordinates after correcting the orthogonality error, the vertical error of the corresponding first motion axis and the vertical error of the second motion axis are determined; wherein, the vertical error of the first motion axis is the position error in the direction perpendicular to the actual direction of the first motion axis, and the vertical error of the second motion axis is the position error in the direction perpendicular to the actual direction of the second motion axis. Based on the vertical errors of the first and second motion axes, the coupling errors of the first and second motion axes are calculated to correct the coupling errors of the target position coordinates, thus obtaining the final corrected target position coordinates.

6. The motion platform error correction method as described in claim 5, characterized in that, The coupling error of the first motion axis is determined by the following formula: in, This represents the coupling error of the first motion axis. This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical direction and the actual direction of the first motion axis. This represents the vertical error of the first motion axis. This indicates the vertical error of the second motion axis; The coupling error of the second motion axis is determined by the following formula: in, This represents the coupling error of the second motion axis. This represents the position coordinates after correcting for the orthogonality error. This represents the error angle between the theoretical direction and the actual direction of the first motion axis. This represents the vertical error of the first motion axis. This indicates the vertical error of the second motion axis.

7. The motion platform error correction method as described in claim 6, characterized in that, The final corrected target position coordinates are determined by the following formula: in, This represents the final corrected target position coordinates. This represents the position coordinates after correcting for the orthogonality error. This indicates the positioning error of the first motion axis. This indicates the positioning error of the second motion axis. This represents the coupling error of the first motion axis. This represents the coupling error of the second motion axis. This represents the error angle between the theoretical direction and the actual direction of the first motion axis.

8. The motion platform error correction method as described in claim 5, characterized in that, The positioning errors of the first motion axis and the second motion axis are calculated using pre-constructed first positioning error fitting curves and second positioning error fitting curves, respectively. The vertical errors of the first motion axis and the second motion axis are calculated using pre-constructed first vertical error fitting curves and second vertical error fitting curves, respectively.

9. The motion platform error correction method as described in claim 8, characterized in that, The methods for constructing the first positioning error fitting curve and the first vertical error fitting curve include: Starting from the origin of the motion platform, samples are taken on the first motion axis to obtain multiple sampling points on the first motion axis; Obtain the theoretical and measured position coordinates of each sampling point; The first fitted line is calculated based on the actual position coordinates of multiple sampling points of the first motion axis, and the first direction vector is calculated based on the first fitted line. For each sampling point, calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the first direction vector to obtain the positioning error of each sampling point on the first motion axis. Calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the vertical direction of the first direction vector to obtain the vertical error of each sampling point on the first motion axis. A first positioning error fitting curve is constructed based on the positioning error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point; a first vertical error fitting curve is constructed based on the vertical error of each sampling point on the first motion axis and the theoretical position coordinates of each sampling point. The methods for constructing the second positioning error fitting curve and the second vertical error fitting curve include: Starting from the origin of the motion platform, samples are taken on the second motion axis to obtain multiple sampling points on the second motion axis; Obtain the theoretical and measured position coordinates of each sampling point; The second fitted line is calculated based on the actual position coordinates of multiple sampling points of the second motion axis, and the second direction vector is calculated based on the second fitted line; For each sampling point, calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the second direction vector to obtain the positioning error of each sampling point on the second motion axis. Calculate the difference between the actual position coordinates of the sampling point and the theoretical position coordinates of the sampling point in the vertical direction of the second direction vector to obtain the vertical error of each sampling point on the second motion axis. A second positioning error fitting curve is constructed based on the positioning error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point. A second vertical error fitting curve is constructed based on the vertical error of each sampling point on the second motion axis and the theoretical position coordinates of each sampling point.

10. A computer program product comprising a computer program and / or instructions, characterized in that, When the computer program and / or instructions are executed by the processor, they implement the motion platform error correction method as described in any one of claims 1-9.

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