CN115666125B  Machine visionbased method for detecting and compensating positioning error of XY platform of chip mounter  Google Patents
Machine visionbased method for detecting and compensating positioning error of XY platform of chip mounter Download PDFInfo
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 CN115666125B CN115666125B CN202211681882.3A CN202211681882A CN115666125B CN 115666125 B CN115666125 B CN 115666125B CN 202211681882 A CN202211681882 A CN 202211681882A CN 115666125 B CN115666125 B CN 115666125B
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Abstract
The invention relates to the technical field of chip mounter control, and particularly discloses a machine visionbased detection and compensation method for positioning errors of an XY platform of a chip mounter, wherein the detection method comprises the following steps: calculating theoretical position coordinates of each marking point in the XY platform based on a mechanical coordinate system; respectively moving a reference mark camera to each mark point, and obtaining the corresponding actual position coordinate of each mark point based on a mechanical coordinate system through the reference mark camera; and calculating the positioning error of each marking point according to the theoretical position coordinates and the actual position coordinates. According to the scheme, an error detection model is established by analyzing error sources, the size and distribution rule of the positioning errors are effectively generalized and accurately calculated, an error detection flow is designed on the basis, an efficient error detection scheme is realized, the positioning accuracy is greatly improved, and the time and cost of error detection are greatly reduced.
Description
Technical Field
The invention relates to the technical field of chip mounter control, in particular to a machine visionbased detection and compensation method for positioning errors of an XY platform of a chip mounter.
Background
The conventional chip mounter includes a mounting head module, an XY axis movement module, a transfer rail module, etc., as shown in fig. 1, in the mounting of components, an X axis 1 and a Y axis 2 move the mounting head to a target position, a reference point action of a PCB on a transfer rail 5 is recognized by a reference mark camera 3 part, and actions of component suction, component mounting, etc. are performed by a plurality of suction nozzle bars 4 on the mounting head. Therefore, the X, Y axis movement positioning precision is an important component of the precision of the mounting element, and directly influences the production quality.
X, Y axis positioning errors are mainly derived from control errors and geometric errors, wherein the control errors are usually caused by the inaccuracy of a control system, and the deviation of an actual motion trail and an ideal motion trail of a motion part, the geometric errors are mainly derived from the manufacturing and equipment precision of parts, and because of shape and position errors of a machine part and the equipment process thereof, when the X, Y axis motion part moves or rotates, the shape and position errors are reflected on the motion part, so that the geometric errors are generated. The control error can reach micronorder precision by adopting an advanced control system, so that the geometric error is a main error factor influencing the X, Y shaft positioning precision.
The conventional geometrical error correction method of the XY moving platform measures X, Y axis errors one by means of a precision test instrument, such as a laser interferometer, a laser range finder or an electronic level meter, which has the following defects for actual field error correction: firstly, a highprecision instrument needs to be used with a skilled operation, and the correction process has high requirements on the knowledge plane of engineering personnel; secondly, considering a production line consisting of a plurality of chip mounters, the correction environment space is compact, a platform based on a highprecision test instrument is difficult to effectively build, and the correction method is complicated to realize; again, the highprecision testing apparatus is usually accompanied by a long detection time, and due to the excessively long time interval for collecting the correction data, the randomness of the axis error of the chip mounter X, Y may be increased, and even the consistency and correlation between the data are affected, thereby reducing the effectiveness of the data.
In addition, the conventional chip mounter X, Y axis positioning error compensation method only comprises two parts of detection and compensation, the error compensation is realized only by modifying a program or codes, and error modeling is ignored or omitted. The effective error compensation should establish an error model, and on this basis, the error detection and compensation can be effectively performed, and the error modeling and detection are closely related and interdependent, so that the error modeling in the positioning error correction of the axis of the chip mounter X, Y is an indispensable component.
Disclosure of Invention
The invention aims to solve the problems, and provides a positioning error detection and compensation method for an XY platform of a chip mounter based on machine vision.
In order to achieve the above object, the first aspect of the present invention provides a machine visionbased XY stage positioning error detection method for a chip mounter, comprising the steps of:
calculating theoretical position coordinates of each marking point in XY platform based on mechanical coordinate systemPt(xt _{ mn } , yt _{ mn } ) The formula is as follows:
，
wherein each marking point is marked by a jig and distributed on the jig in a rectangular array, deltaθRepresents the inclination angle of the jig relative to the XY platform,、/>respectively represent the firstmLine 1nThe abscissa of the row of marking points in the jigbased coordinate system, < + >>、/>Respectively represent the horizontal and vertical coordinates of the datum point under the jigbased coordinate system,xr _{11} 、yr _{11} representing the abscissa of the actual position of the datum point in the mechanical coordinate system;
respectively moveMoving a reference mark camera to each mark point, and obtaining the corresponding actual position coordinate of each mark point based on a mechanical coordinate system by the reference mark camera to Pr #xr _{ mn } , yr _{ mn } )；
Calculating the positioning error (delta) of each mark pointx _{ mn } ，Δy _{ mn } ) The formula is deltax _{ mn } =xt _{ mn }  xr _{ mn } ，Δy _{ mn } =yt _{ mn }  yr _{ mn } 。
Preferably, the inclination angle delta of the jig relative to the XY platformθThe calculation formula is as follows:
，
，
wherein,,θ _{ T } for the theoretical angle of the jig, the jig is provided with a plurality of holes,θ _{ R } in order to achieve the actual angle of the jig,x _{ MN } 、y _{ MN } respectively represent the abscissa and the ordinate, delta of the reference point II under the mechanical coordinate systemx _{ MN } 、Δy _{ MN } Respectively represent the position deviation of the reference point II, deltax _{11} 、Δy _{11} The positional deviations of the first reference points are respectively indicated,x _{11} 、y _{11} representing the reference pointthe abscissa in the mechanical coordinate system.
Preferably, the positional deviation is obtained by the reference mark camera using an identification mark circle method.
Preferably, the jig is in a plateshaped structure and is arranged on the XY platform; the reference mark camera is fixedly arranged on the mounting head.
Preferably, the method further comprises storing the position information of each marking point and the positioning error thereofxr _{ mn, } yr _{ mn } , Δx _{ mn } , Δy _{ mn } ]。
The second aspect of the invention provides a positioning error detection system of an XY platform of a chip mounter based on machine vision, comprising
The image acquisition module is used for shooting mark point images when the mounting head moves to the positions of all mark points, and comprises a reference mark camera and a jig, wherein the reference mark camera is arranged on the mounting head, the jig is arranged on the XY platform, and all mark points are distributed on the jig in a rectangular array;
the image processing module is used for identifying the central position of the marking point on the image and calculating the position deviation of each marking point through the deviation between the marking point center and the image central position;
the operation control module is used for driving the XY axis to move the reference mark camera to the positions of all mark points;
and the calculation module is used for executing the steps of the detection method according to the position information of each marking point.
The invention provides a machine visionbased positioning error compensation method for an XY platform of a chip mounter, which comprises the following steps:
calculating the inclination angle delta of the circuit board positioned in the XY platform relative to the XY platformθ _{ R } ；
Calculating the positioning error according to the detection method, and calculating a datum point on the circuit board by using an interpolation algorithmJ _{0} The positioning error of (C) is recorded as%,/>) The following steps are:
in the middle off _{ x } 、f _{ y } X, Y axis positioning error compensation values obtained by interpolation algorithm respectivelyxr _{ J0 } ，yr _{ J0 } ) Is the datum pointJ _{0} Based on the actual position coordinates in the mechanical coordinate system;
according to the theoretical position coordinates of the mounting point P under the mechanical coordinate systemxt _{ P } , yt _{ P } ) Calculating the corresponding actual position coordinatesxr _{ P } , yr _{ P } ) The following steps are:
，
in the middle ofxt _{ J0} 、yt _{ J0} Respectively are datum pointsJ _{0} The abscissa of the theoretical position in the mechanical coordinate system;
calculating the positioning error compensation value of the mounting point P and recording the value of the positioning error compensation value,/>) The following steps are:
；
compensating the mounting point P, and marking the compensated mounting position as a mark of #,/>) The following steps are:
。
preferably, the inclination angle delta of the circuit board relative to the XY platformθ _{ R } The calculation process of (2) is as follows:
determining two fiducial points on a circuit board located within an XY stageJ _{0} AndJ _{1} two datum pointsJ _{0} AndJ _{1} theoretical position coordinates based on a mechanical coordinate system are respectively recorded asJ _{ t0} (xt _{ J0} , yt _{ J0} ) AndJ _{ t1} (xt _{ J1} , yt _{ J1} )；
identifying two fiducial points with fiducial marker cameras, respectivelyJ _{0} AndJ _{1} the positional deviations of (a) are respectively denoted as deltaJ _{0} (Δx _{ J0} ，Δy _{ J0} ) And deltaJ _{1} (Δx _{ J1} ，Δy _{ J1} ) The method comprises the steps of carrying out a first treatment on the surface of the Calculating the inclination angle delta of the circuit board relative to the XY platformθ _{ R } The formula is:
，
xr _{ J 0} =xt _{ J0 } + Δx _{ J0} ，yr _{ J0 } =yt _{ J0 } + Δy _{ J0} ，xr _{ J1 } =xt _{ J1} + Δx _{ J1 } ，yr _{ J1 } =yt _{ J1 } + Δy _{ J1 } ，
wherein,,xr _{ J1 } ，yr _{ J1 } respectively are datum pointsJ _{1} Based on the actual position abscissa in the mechanical coordinate system.
Preferably, the interpolation algorithm is implemented according to nearest neighbor interpolation, linear interpolation or bilinear interpolation.
The fourth aspect of the present invention provides a positioning error compensation system for an XY platform of a chip mounter based on machine vision, comprising: the circuit board inclination angle module is used for calculating the inclination angle delta of the circuit board positioned in the XY platform relative to the XY platformθ _{ R } ；
The datum point positioning error module is used for calculating the datum point on the circuit board by utilizing an interpolation algorithmJ _{0} The positioning error of (C) is recorded as%,/>) The following steps are:
in the middle off _{ x } 、f _{ y } X, Y axis positioning error compensation values obtained by interpolation algorithm respectivelyxr _{ J0 } ，yr _{ J0 } ) Is the datum pointJ _{0} Based on the actual position coordinates in the mechanical coordinate system;
the actual position coordinate module is used for calculating the theoretical position coordinate of the mounting point P based on the mechanical coordinate systemxt _{ P } , yt _{ P } ) Calculating the corresponding actual position coordinatesxr _{ P } , yr _{ P } ) The following steps are:
，
middle%xt _{ J0} ，yt _{ J0} ) Is the datum pointJ _{0} Theoretical position coordinates in a mechanical coordinate system;
the mounting point positioning error module is used for calculating a positioning error compensation value of the mounting point P and recording the value of the positioning error compensation value,/>) The following steps are:
；
the compensation module is used for compensating the mounting point P, and the mounting position after compensation is marked as a mark of #,/>) The following steps are: />。
Through the technical scheme, the error sources are analyzed, an error detection model is established, the size and distribution rule of the positioning errors are effectively generalized and accurately calculated, an error detection flow is designed on the basis, an efficient error detection scheme is realized, the positioning accuracy is greatly improved, and the time and cost of error detection are greatly reduced.
Drawings
Fig. 1 is a schematic structural diagram of a conventional chip mounter;
FIG. 2 is a schematic diagram of an XY stage positioning error compensating glass plate fixture;
FIG. 3 is a schematic diagram of the calibration positions of the glass plate jig in two coordinate systems;
FIG. 4 is a schematic diagram of the identification of the mark points on the jig based on machine vision;
FIG. 5 is a schematic diagram of error correction of the inclination angle of the glass plate jig;
FIG. 6 is an XY motion profile for error detection in accordance with an embodiment of the present invention;
FIG. 7 is a diagram showing the comparison of errors before and after the XY stage compensation, FIG. 7 (a) is the result before the compensation, and FIG. 7 (b) is the result after the compensation;
in the figure: 1. an X axis; 2. a Y axis; 3. a fiducial marker camera; 4. a suction nozzle lever; 5. and a transfer rail.
Detailed Description
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
In order to meet the highprecision positioning precision requirement of an XY platform of a chip mounter, firstly, a positioning error source of an XY axis is analyzed, wherein the positioning error mainly comes from an XY axis geometric error, and the analysis process of the XY axis geometric error source is specifically as follows:
when the mounting heads move along the respective edgesX、YDuring shaft feeding, neglectingZGeometric error of direction, axial edgex、yActual position point after directional movementx _{ real } , y _{ real } ) And ideal position point [ ]x _{ theory } , y _{ theory } ) At the position ofXYThe platform has two directions of error deltax _{ geo } 、Δy _{ geo } The method comprises the following steps:
（1）
in the method, in the process of the invention,E _{ x } (x, y)、E _{ y } (x, y) For attaching heads along respectivelyX、YAfter the shaft movesx、yError values generated in the direction;E _{ x } (x, y) The error value is the edgeXThe shaft moving inxThe combination of errors generated in the direction comprises the influences of positioning errors, straightness errors, rotation angle errors and perpendicularity errors. In the same way, the processing method comprises the steps of,E _{ y } (x, y) Is a rimYThe shaft moving inyAnd (3) synthesizing errors generated in the direction. The detection and compensation method of the invention is aimed atX、YGeometric errors due to shaft motion.
X、YThe geometric error of the shaft motion is measured by calibrating an XY platform by using a jig, the jig is preferably a precise glass plate, a circle of a rectangular array is used as a marking point to mark the precise glass plate, and plane comprehensive positioning correction is carried out, as shown in fig. 2, and fig. 2 is a schematic diagram of the jig for the XY platform positioning error compensation glass plate. Assume thatX _{ g } Y _{ g } In order to be a coordinate system of the jig,XYfor a mechanical coordinate system (i.e. a coordinate system constructed based on an XY platform), the glass plate can be regarded as an ideal rectangular plane array, and the row spacing of the marking points is as followsD _{ x } The column pitch isD _{ y } In the followingX _{ g } Y _{ g } Under the coordinate system of the jig, the firstmA row(s),nThe coordinate positions of the units of the measuring points are%，/>）：
（2）
As shown in fig. 3, fig. 3 shows the two coordinate systems (i.e.X _{ g } Y _{ g } Jig coordinate systemXYMechanical coordinate system) glass plate jig correction position diagram, glass plate is placed onXOYIn plane, the glass sheets being inclined on the conveying track, i.e.X _{ g } Y _{ g } Jig coordinate systemXYThe mechanical coordinate system has a small included angle error.
Assume thatF _{11} Is a datum point (marked in figure 2) byX、YIncrement of shaft movementD _{ x } Multiple and incrementD _{ y } When the multiple reaches the position of a certain mark point, obtaining the position deviation of the position image according to an image recognition circle methodAnd records that there is a deviation delta between the measured position and the theoretical position as shown in FIG. 4xAnd deltayOffset deltaxAnd deltayCan be described as the following relationship:
（3）
in the formula deltax _{ jig } Caused by the inclination of the glass plate jigXDirection error, deltax _{ geo } Is thatXGeometric errors of axis deltax _{ rec } Generated for machine vision recognition circleXDirection error. Similarly, Δy _{ jig } Caused by tilting of the glass sheetsYDirection error, deltay _{ geo } Is thatYGeometric errors of axis, Δy _{ rec } Generated for identifying circlesYDirection error.
Further, the image recognition circle method is to calculate the position of the center pixel of the marked circle by using an image processing method, and adopt a conventional least square fitting circle flow of threshold segmentation, binarization processing and edge extraction points, wherein the calculated circle center can obtain subpixel precision of about 0.1 pixel (pixel represents a pixel). Preferably, the reference mark camera used in the image recognition circle method of the present invention adopts a magnification lens, and the resolution of pixels in the image is about 5 μm/pixel, so that the machine vision can achieve the following precision: 0.1 pixel 5 μm/pixel=0.5 μm, well meeting the accuracy requirements of the detection.
Considering that the error generated by the identification of the marker circle image is small and not more than 1 μm, Δ may be ignored for ease of analysisx _{ rec } And Deltay _{ rec } Error, i.e. deltax _{ rec } =0 and Δy _{ rec } =0. Thus, formula (3) can be simplified as:
（4）
from equation (4), it is known that in order to obtain a measurement pointXYGeometric error delta of shaftx _{ geo } 、Δy _{ geo } It is necessary to eliminate the inclination error delta caused by the placement of the glass platex _{ jig } 、Δy _{ jig } 。
Secondly, based on XY axis geometric error source analysis, an XY axis geometric error detection mathematical model is constructed, and the basic principle is as follows: the reference mark camera on the mounting head can be regarded as precision equipment, a machine vision based on the reference mark camera is adopted to provide a precise reference standard, the reference mark camera is further used as a measuring tool for mechanical movement positioning errors, the positioning accuracy is jointly determined by the machine vision positioning accuracy and the mechanical movement accuracy, and an XY axis geometric error detection mathematical model is constructed on the basis.
The modeling specific process of the mathematical model for detecting the geometric errors of the XY axes is as follows:
at the position ofX _{ g } Y _{ g } In the jig coordinate system, the reference points are illustratively marked by taking the 1 st row and 1 st column mark points as the reference pointsF _{11} The coordinate position of (marked in figure 2) is,/>) Datum pointF _{ MN } The coordinate position (see label in FIG. 2) is>, ) = (/> +m*D _{ x } , /> +n*D _{ y } ) The method comprises the steps of carrying out a first treatment on the surface of the At the position ofXYIn the mechanical coordinate system, the datum point is recordedF _{11} The corresponding theoretical position coordinates are +.>(x _{11} , y _{11} ) Datum pointF _{ MN } The corresponding theoretical position coordinates are +.> (x _{ MN } , y _{ MN } )= (x _{11} +m*D _{ x } , y _{11} + n*D _{ y } )。
At the position ofXYMoving the fiducial mark camera on the placement head to be positioned at the machine coordinate system(x _{11} , y _{11} ) Position is photographed and a datum point is obtained according to the image recognition circle>The deviation was recorded as (delta)x _{11} , Δy _{11} ) Reference point>The actual position coordinate of (C) is%xr _{11} , yr _{11} ) = (x _{11} +Δx _{11} , y _{11} +Δy _{11} ). ThenXShaft movementm*D _{ x } Distance andYshaft movementn*D _{ y } Distance to reach datum point>Similarly, the identification deviation is recorded as (Δx _{ MN } , Δy _{ MN } ) Reference point>Is the actual position coordinates of (a)(xr _{ MN } , yr _{ MN } ) = (x _{ MN } +Δx _{ MN } , y _{ MN } +Δy _{ MN } ) As shown in fig. 5. The inclination angle delta of the glass plateθThe calculation formula is as follows:
Δθ =θ _{ R }  θ _{ T } （5）
in (5)θ _{ T } For the theoretical angle of the glass sheet,θ _{ R } for the actual angle of the glass plate, the relation is respectively:
（6）
（7）
elongation of default jig is 1, when glass plate is used as jig, consider glass plate inclination, under the condition ofXYMechanical coordinate system, itemmRow of linesnThe theoretical sitting mark after the column mark points eliminate the inclination error is as followsPt(xt _{ mn } , yt _{ mn } ) The following steps are:
（8）
wherein,,、/>respectively represent the firstmLine 1nThe horizontal and vertical coordinates of the row of marking points in the jigbased coordinate system.
Further eliminating glass sheet tilt errors, i.e. moving the fiducial mark camera to the mark point position according to equation (8)Pt(xt _{ mn } , yt _{ mn } ) And similarly, according to the circle image identification processing, obtaining the circle center identification offset value and marking the circle center identification offset value as (delta)x _{ mn } , Δy _{ mn } ) First, themRow of linesnThe actual position coordinates of the column mark points arePr(xr _{ mn } , yr _{ mn } ) The following steps are:
（9）
according to the formulas (4) and (9), the first can be obtainedmRow of linesnThe geometrical error values of the column mark points are:
（10）
thus, according to formula (10)XYAnd obtaining the geometric error data of each marking point under the twodimensional plane to obtain the positioning error of each marking point.
Based on the above positioning error source analysis and the constructed mathematical model, the first aspect of the invention provides a machine visionbased positioning error detection method for an XY platform of a chip mounter, comprising the following steps:
s1, calculating theoretical position coordinates of each marking point in an XY platform based on a mechanical coordinate systemPt(xt _{ mn } , yt _{ mn } ) The formula is as follows:
wherein each marking point is marked by a jig and distributed on the jig in a rectangular array, deltaθRepresents the inclination angle of the jig relative to the XY platform,、/>respectively represent the firstmLine 1nThe abscissa of the row of marking points in the jigbased coordinate system, < + >>、/>Respectively represent datum pointsF _{11} The abscissa and the ordinate under the coordinate system of the jig,xr _{ 11 } 、yr _{ 11 } respectively represent datum pointsF _{11} The abscissa of the theoretical position in the mechanical coordinate system.
Before executing step S1, a process of calculating the inclination angle of the glass plate needs to be executed, which specifically includes the following steps:
s11, firstly adjusting the width of a conveying track, placing a glass plate on the conveying track, and then clamping and fixing the glass plate by using a substrate clamp;
s12, manually moving the reference mark camera toF _{11} As far as possible within the field of view of the marking pointF _{11} The marked circle is positioned at the visual center of the camera, and is obtained by a method for identifying the marked circleF _{11} Mark point deviation (delta)x11, Δy11)；
S13, moving X, Y shaft to move the reference mark toF _{ MN } Marking point positions, and obtaining by using a method for identifying marked circlesF _{ MN } The mark point offset is denoted as (delta)x MN, ΔyMN)；
S14, calculating according to the formula (7) to obtain the inclination angle delta of the jigθ。
S2, respectively moving the reference mark camera to each mark point, and obtaining the corresponding actual position coordinate of each mark point based on the mechanical coordinate system by the reference mark camera as followsPr(xr _{ mn } , yr _{ mn } )；
After the process of calculating the inclination angle of the glass plate is performed, the reference mark camera is sequentially moved to each mark point, and as shown in fig. 6, the positions and the motion trajectories of each mark point are illustrated, and the mark points are sequentially photographed from m=1:m, n=1:n, and the motion in fig. 6 is illustratedThe track order is indicated by the arrow: 1>2>3>4, obtaining the corresponding actual position coordinates of each marking point based on the mechanical coordinate system asPr(xr _{ mn } , yr _{ mn } )。
S3, calculating the positioning error (delta) of each mark pointx _{ mn } , Δy _{ mn } ) The formula is as follows:
Δx _{ mn } =xt _{ mn }  xr _{ mn } ，
Δy _{ mn } =yt _{ mn }  yr _{ mn } 。
s4, storing the position information of each mark point and the positioning error thereofxr _{ mn } , yr _{ mn } , Δx _{ mn } , Δy _{ mn } ]Stored in a table form in a data file to provide a data set for a subsequent compensation implementation.
Based on the same inventive concept, a second aspect of the present invention provides a machine visionbased positioning error detection system for an XY platform of a chip mounter, comprising:
the image acquisition module is used for shooting mark point images when the mounting head moves to the positions of all mark points, and comprises a reference mark camera, a jig and an image acquisition card, wherein the reference mark camera is arranged on the mounting head, the jig is arranged on the XY platform, and all mark points are distributed on the jig in a rectangular array; the image acquisition card transmits the image information to the upper computer for image recognition processing;
the image processing module is used for identifying the central position of the marking point on the image and calculating the position deviation of each marking point through the deviation between the marking point center and the image central position;
the operation control module is used for driving an XY axis to move the reference mark camera to the positions of the mark points; an upper computer sends an XY axis movement control instruction to an XY axis operation control system, and a servo motor in the operation control system drives a ball screw to realize XY axis positioning; the motion control error in the operation control system is the steady state error of the control system, and the motion control error in the scheme of the invention is smaller than 4 mu m, so the system error generated by motion control is ignored;
and the calculation module is used for executing the step of the machine visionbased positioning error detection method of the XY platform of the chip mounter according to the position information of each marking point. According to the scheme, the error detection model is established by analyzing the error sources, the size and distribution rule of the positioning errors are effectively generalized and accurately calculated, and on the basis, an error detection flow is designed, so that an efficient error detection scheme is realized, the positioning accuracy is greatly improved, and the time and cost of error detection are greatly reduced.
The invention provides a machine visionbased positioning error compensation method for an XY platform of a chip mounter, which comprises the following steps:
(1) Calculating the inclination angle delta of the circuit board positioned in the XY platform relative to the XY platformθ _{ R } ；
Illustratively, taking a PCB as an example, a PCB error compensation mathematical model is established to realize error compensation. First calculate the tilt angle deltaθ _{ R } : assume that the PCB has 2 datum points respectively marked asJ _{0} AndJ _{1} in the followingXYTheoretical position coordinate data of the mechanical coordinate system is recorded asJ _{ t0} (xt _{ J0} , yt _{ J0} ) AndJ _{ t1} (xt _{ J1} , yt _{ J1} ) The deviation of the reference mark identified by the reference mark camera image is noted as deltaJ _{0} (Δx _{ J0} ，Δy _{ J0} ) And deltaJ _{1} (Δx _{ J1} ，Δy _{ J1} ) Therefore, it isJ _{0} AndJ _{1} at the position ofXYThe actual position coordinates of the mechanical coordinate system areJ _{0r} (xr _{ J0} , yr _{ J0 } ) = (xt _{ J0 } +Δx _{ J0} , yt _{ J0 } + Δy _{ J0} ) AndJ _{1r} (xr _{ J1 } , yr _{ J1 } ) = (xt _{ J1 } + Δx _{ J1} , yt _{ J1 } + Δy _{ J1} )。
according to (5), the inclination angle of the PCB is as follows:
（11）
(2) Calculating the positioning error according to the detection method, and calculating a datum point on the circuit board by using an interpolation algorithmJ _{0} Positioning errors of (a);
calculating a reference point based on the interpolation algorithm and the stored positioning error compensation dataJ _{0} The geometric error of%,/>) Is the datum pointJ _{0} The XY axis geometrical error values are identified as follows:
（12）
in the middle off _{ x } 、f _{ y } And X, Y axis geometric error compensation values obtained by an interpolation algorithm respectively.
(3) The seating mark is marked as @ according to the theoretical position of the mounting point P under the mechanical coordinate systemxt _{ P } , yt _{ P } ) Calculating the corresponding actual position coordinatesxr _{ P } , yr _{ P } ) The method comprises the steps of carrying out a first treatment on the surface of the The actual mounting position of the mounting point P is calculated according to the inclination angle of the PCB, and then the following steps are included:
（13）。
(4) Calculating the mounting point PThe compensation value of the positioning error is recorded as%,/>)；
Calculating geometrical error compensation value of the mounting point according to the calculation of (13), and recording the geometric error compensation value of the mounting point,/>) The geometrical error compensation error values for the XY stage are:
（14）。
(5) Further to the mounting pointPCompensating, and marking the compensated mounting coordinate position as%,/>) The following steps are:
（15）。
thus, inXYIn the mechanical coordinate system, after error compensation, the mounting point is pastedPThe final mounting position is%,)。
Further, the interpolation algorithm can be realized according to conventional algorithms such as nearest neighbor interpolation, linear interpolation or bilinear interpolation, and the like, so as to obtain XY axis geometric error compensation data of the target position.
Based on the same inventive concept, a fourth aspect of the present invention provides a machine visionbased positioning error compensation system for an XY platform of a chip mounter, comprising:
the PCB inclination angle module is used for calculating the inclination angle delta of the PCB positioned in the XY platform relative to the XY platformθ _{ R } ；
The datum point positioning error module is used for calculating the datum point on the circuit board by utilizing an interpolation algorithmJ _{0} The positioning error of (C) is recorded as%,/>) The following steps are:
in the middle off _{ x } 、f _{ y } Respectively obtaining positioning error compensation values by interpolation algorithmxr _{ J0 } ，yr _{ J0 } ) Is the datum point J _{0} Based on the actual position coordinates in the mechanical coordinate system;
the actual position coordinate module is used for mounting points according toPTheoretical position coordinates based on mechanical coordinate systemxt _{ P } , yt _{ P } ) Calculating the corresponding actual position coordinatesxr _{ P } , yr _{ P } ) The following steps are:
；
a mounting point positioning error module for calculating the mounting pointPThe compensation value of the positioning error is recorded as%,/>) The following steps are:
；
a compensation module for the mounting pointPCompensating, and marking the compensated mounting position as a mark of #,/>) The following steps are:
。
according to the technical scheme, a mathematical model for detecting the geometric errors of the XY axis based on machine vision is constructed according to the source of the geometric errors of the XY axis, an error automatic detection flow is designed through the error detection model, finally, a PCB error compensation mathematical model is established according to error data, a new error which is equal to the original error in size and opposite in direction is utilized to offset the positioning errors of the XY axis, the positioning precision of the XY axis of the chip mounter is greatly improved, and the purpose of improving the equipment precision is achieved.
Therefore, the scheme provides a compensation method for the X, Y axis positioning error of the chip mounter based on machine vision, an error detection model is established by analyzing error sources, the size and distribution rule of geometric errors are effectively generalized and accurately calculated, an error detection flow is designed on the basis, an efficient error detection scheme is realized, and the time and cost of error detection are greatly reduced. Further, a compensation means of software technology is provided, a new error is artificially generated to counteract the original error which is currently a problem, the validity of the method is verified,the error compensation effect of the X, Y axis of the chip mounter is remarkable, the positioning accuracy is greatly improved, an effective and accurate method for improving the positioning accuracy of the X, Y axis of the chip mounter is realized, and the purpose of improving the equipment accuracy is achieved. In order to verify the effectiveness of the technical scheme of the invention, error compensation comparison test is carried out, the detection conditions before and after compensation and the installation mode of the glass plate jig and other kits are unchanged, corresponding error compensation data are obtained, as shown in fig. 7, fig. 7 is an error comparison schematic diagram before and after XY platform compensation, wherein delta is calculated by the following stepsxThe abscissa is the actual position and the theoretical positionXDeviation of direction, similarly, deltay The ordinate of the actual position and the theoretical positionYThe direction deviation is marked as the same as the schematic diagram of fig. 4.
As can be seen from figure 7 of the drawings,Xthe directional position error was reduced from 30 μm before compensation shown in fig. 7 (a) to 5 μm after compensation shown in fig. 7 (b),Ythe direction error is reduced from 20 μm before compensation to 5 μm after compensation,X、Ythe positioning precision is well improved, the reduction amplitude of partial errors exceeds 20 mu m, the partial precision is improved by more than 50 percent, and the comparison test proves that after the technical proposal provided by the invention is used for compensation, the error compensation effect is obvious,X、Ythe positioning accuracy is greatly improved.
In summary, the technology establishes an error detection model by analyzing error sources, and effectively generalizes and accurately calculates the size and distribution rule of geometric errors. By means of the highprecision glass plate jig, an efficient error detection scheme is realized, error detection is an automatic process, time and cost of error detection are greatly reduced, a compensation means of a software technology is adopted, a PCB circuit board error compensation mathematical model is constructed, a new error counteracts the original error which is currently a problem, the effectiveness of the method is verified, the compensated positioning precision is obviously improved, the method is suitable for a X, Yaxis highprecision positioning system of a chip mounter, and the purpose of improving equipment precision is achieved.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including the combination of the individual specific technical features in any suitable way. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition. Such simple variations and combinations are likewise to be regarded as being within the scope of the present disclosure.
Claims (7)
1. The machine visionbased positioning error detection method for the XY platform of the chip mounter is characterized by comprising the following steps of:
the calculation of each marker point within the XY stage is based on the theoretical position coordinates Pt (xt _{mn} ,yt _{mn} ) The formula is as follows:
wherein each marking point is marked by a jig and distributed on the jig in a rectangular array, the jig is in a plateshaped structure and arranged on the XY platform, delta theta represents the inclination angle of the jig relative to the XY platform, and x' is the inclination angle of the jig relative to the XY platform. _{mn} 、y′ _{mn} Respectively represents the horizontal and vertical coordinates, x 'of the nth marking point of the mth row under the jigbased coordinate system' _{11} 、y′ _{11} Respectively represent the abscissa, xr of the datum point under the jigbased coordinate system _{11} 、yr _{11} Representing the abscissa of the actual position of the datum point in the mechanical coordinate system; the calculation formula of the inclination angle delta theta of the jig relative to the XY platform is as follows:
Δθ＝θ _{R} θ _{T} ，
wherein θ _{T} Is the theoretical angle of the jigDegree, θ _{R} To the actual angle of the jig, x _{MN} 、y _{MN} Respectively represent the abscissa and the ordinate, deltax of the reference point II under the mechanical coordinate system _{MN} 、Δy _{MN} Respectively represent the position deviation of the reference point II, deltax _{11} 、Δy _{11} Respectively represent the position deviation of the datum points I, x _{11} 、y _{11} Representing the abscissa of the datum point in a mechanical coordinate system; the position deviation is obtained by the reference mark camera through an identification mark circle method, and the reference mark camera is fixedly arranged on the mounting head;
moving the reference mark camera to each mark point respectively, and obtaining the corresponding actual position coordinate of each mark point based on the mechanical coordinate system by the reference mark camera to be Pr (xr) _{mn} ,yr _{mn} )；
Calculating the positioning error (Deltax) of each mark point _{mn} ，Δy _{mn} ) The formula is deltax _{mn} ＝xt _{mn} xr _{mn} ，Δy _{mn} ＝yt _{mn} yr _{mn} 。
2. The method according to claim 1, further comprising storing the position information of each of the marker points and a positioning error [ xr ] thereof _{mn} ,yr _{mn} ,Δx _{mn} ,Δy _{mn} ]。
3. Machine visionbased positioning error detection system for XY platform of chip mounter, which is characterized by comprising
The image acquisition module is used for shooting mark point images when the mounting head moves to the positions of all mark points, and comprises a reference mark camera and a jig, wherein the reference mark camera is arranged on the mounting head, the jig is arranged on the XY platform, and all mark points are distributed on the jig in a rectangular array;
the image processing module is used for identifying the central position of the marking point on the image and calculating the position deviation of each marking point through the deviation between the marking point center and the image central position;
the operation control module is used for driving the XY axis to move the reference mark camera to the positions of all mark points;
calculation module for performing the steps of the method according to claim 1 or 2 on the basis of the position information of the marking points.
4. The machine visionbased XY platform positioning error compensation method for the chip mounter is characterized by comprising the following steps of:
calculating the inclination angle delta theta of the circuit board positioned in the XY platform relative to the XY platform _{R} ；
The positioning error is calculated according to the method of claim 1 or 2, and the reference point J on the circuit board is calculated by using interpolation algorithm _{0} Is recorded as the positioning error ofThen there are:
f in _{x} 、f _{y} X, Y axis positioning error compensation values (xr) obtained by interpolation algorithm respectively _{J0} ，yr _{J0} ) Is the datum point J _{0} Based on the actual position coordinates in the mechanical coordinate system;
according to the theoretical position coordinates (xt) of the mounting point P in a mechanical coordinate system _{P} ,yt _{P} ) Calculate the corresponding actual position coordinates (xr _{P} ,yr _{P} ) The following steps are:
in xt _{J0} 、yt _{J0} Respectively is datum point J _{0} The abscissa of the theoretical position in the mechanical coordinate system;
calculating the positioning error compensation value of the mounting point P and recordingThen there are:
compensating the mounting point P, and marking the compensated mounting position asThen there are:
5. the compensation method of claim 4, wherein the circuit board is at an angle of inclination Δθ relative to the XY stage _{R} The calculation process of (2) is as follows:
determining two fiducial points J on a circuit board located within an XY stage _{0} And J _{1} Two datum points J _{0} And J _{1} Theoretical position coordinates based on the mechanical coordinate system are respectively noted as (xt) _{J0} ,yt _{J0} ) Sum (xt) _{J1} ,yt _{J1} )；
Identifying two fiducial points J with fiducial marker cameras, respectively _{0} And J _{1} The positional deviations of (a) are respectively denoted as (Δx) _{J0} ，Δy _{J0} ) And (Deltax) _{J1} ，Δy _{J1} ) The method comprises the steps of carrying out a first treatment on the surface of the Calculating the inclination angle delta theta of the circuit board relative to the XY platform _{R} The formula is:
xr _{J0} ＝xt _{J0} +Δx _{J0} ，yr _{J0} ＝yt _{J0} +Δy _{J0} ，xr _{J1} ＝xt _{J1} +Δx _{J1} ，yr _{J1} ＝yt _{J1} +Δy _{J1} ，
wherein xr is _{J1} ，yr _{J1} Respectively is datum point J _{1} Based on the actual position abscissa in the mechanical coordinate system.
6. The compensation method according to claim 4 or 5, wherein the interpolation algorithm is implemented according to nearest neighbor interpolation, linear interpolation or bilinear interpolation.
7. Machine visionbased positioning error compensation system for an XY platform of a chip mounter, which is characterized by comprising:
the circuit board inclination angle module is used for calculating the inclination angle delta theta of the circuit board positioned in the XY platform relative to the XY platform _{R} ；
The datum point positioning error module is used for calculating a datum point J on the circuit board by utilizing an interpolation algorithm _{0} Is recorded as the positioning error ofThen there are:
f in _{x} 、f _{y} X, Y axis positioning error compensation values (xr) obtained by interpolation algorithm respectively _{J0} ，yr _{J0} ) Is the datum point J _{0} Based on the actual position coordinates in the mechanical coordinate system;
an actual position coordinate module for determining theoretical position coordinates (xt) of the mounting point P based on a mechanical coordinate system _{P} ,yt _{P} ) Calculate the corresponding actual position coordinates (xr _{P} ,yr _{P} ) The following steps are:
in xt _{J0} 、yt _{J0} Respectively is datum point J _{0} The abscissa of the theoretical position in the mechanical coordinate system;
the mounting point positioning error module is used for calculating a positioning error compensation value of the mounting point P and recordingThen there are:
the compensation module is used for compensating the mounting point P, and the mounting position after compensation is marked asThen there are: />
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