CN109146956B - Method for obtaining linear error correction coefficient of visual positioning system - Google Patents
Method for obtaining linear error correction coefficient of visual positioning system Download PDFInfo
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Abstract
The invention discloses a method for acquiring a linear error correction coefficient of a visual positioning system, which sequentially comprises the following steps: step 1: the target is driven to do circular motion along a unit circle, and then the center of the unit circle is used as a seat of the vision positioning systemMarking an original point; step 2: the vision positioning system measures the moving target once to obtain the measuring coordinate (X) of the target at the moment0,Y0) (ii) a And step 3: mixing X0And Y0Substituting formula Y1=[（1‑X0 2）1/2+Y0]In/2, to calculate Y1(ii) a Then Y is put0And Y1Substituting into formula K1=Y1/Y0In order to calculate K1And finally K1And X0Substituting formula X1=K1*X0In order to calculate X1(ii) a And 4, step 4: mixing X1And Y1Substituting formula Yi+1=[（1‑Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiPerforming iteration; when Y isi+1And YiStopping iteration when the difference value between the two is less than the threshold value; then Y is put0And the last Y-axis correction coordinate Yi+1Substituting formula K = Yi+1/Y0To calculate a linear error correction coefficient K of the visual positioning system. The invention can obtain the linear error correction coefficient of the visual positioning system.
Description
Technical Field
The invention relates to a visual positioning system, in particular to a method for acquiring a linear error correction coefficient of the visual positioning system.
Background
The visual positioning system shoots a characteristic point on an object through a plurality of CCD cameras to respectively obtain the coordinates of the characteristic point on each camera image plane, and as long as the accurate relative position of each camera is known, the coordinates of the characteristic point in a coordinate system for fixing one camera can be obtained by a geometric method, namely the position of the characteristic point is determined.
The structural parameters of the CCD camera are directly related to the image acquisition and detection precision, the parameters are divided into internal parameters and external parameters, a visual positioning system needs to carry out equipment calibration before being used, and the internal parameters and the external parameters are solved, so that the quantitative relation between the space position of the space characteristic point and the coordinates of the corresponding point of the two-dimensional image is obtained. However, the vision positioning system may have a deviation in the coefficient calibration result during the calibration process, and this phenomenon may cause a linear error in the calculated measured coordinate values, resulting in an equal-scale enlargement or reduction relationship between the measured coordinate values and the actual coordinate values. Meanwhile, if the difference between the use environment and the calibration environment is large, the actual size factor and the calibration result are in and out, and a linear error of the measurement coordinate value also occurs. In addition, due to the problem of automatic focusing response, when the spatial features dynamically operate, focusing lag causes poor imaging effect, the imaging size changes, and linear errors of measurement coordinate values also occur. Therefore, a linear error exists between the measured coordinate value output by the existing visual positioning system and the actual coordinate value, and a linear error correction coefficient is required to correct the measured coordinate value.
Disclosure of Invention
The invention aims to provide a method for acquiring a linear error correction coefficient of a visual positioning system, which can acquire the linear error correction coefficient of the visual positioning system so as to correct the measurement coordinate of the visual positioning system.
In order to achieve the above purpose, the solution of the invention is:
a method for obtaining linear error correction coefficient of visual positioning system includes:
step 1: driving a target to do circular motion along a unit circle, and then taking the center of the unit circle as the origin of coordinates of the unit circle by the vision positioning system;
step 2: the vision positioning system measures the moving target once to obtain the measurement of the target at the momentCoordinate (X)0,Y0）；
And step 3: mixing X0And Y0Substituting formula Y1=[（1-X0 2）1/2+Y0]In/2, the first time Y-axis correction coordinate Y is obtained by calculation1(ii) a Then Y is put0And Y1Substituting into formula K1=Y1/Y0In order to calculate the first linear error correction coefficient K1And finally K1And X0Substituting formula X1=K1*X0In order to calculate and obtain the first X-axis corrected coordinate X1；
And 4, step 4: mixing X1And Y1Substituting formula Yi+1=[（1-Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiWhere i is a positive integer greater than 0, YiCorrecting the coordinates for the ith Y-axis, XiCorrection of coordinates for the ith X-axis, Yi+1Correction of coordinates for the i +1 th Y-axis, Xi+1Correcting the coordinates for the (i + 1) th X-axis; when Y isi+1And YiStopping iteration when the difference value between the two is less than the threshold value; then Y is put0And the last Y-axis correction coordinate Yi+1Substituting formula K = Yi+1/Y0To calculate a linear error correction coefficient K of the visual positioning system.
In step 1, the method for the vision positioning system to use the center of the unit circle as its origin of coordinates includes: the target stays at a plurality of designated positions on the unit circle, the visual positioning system performs static measurement on the target staying at the designated positions to acquire three-dimensional space coordinates of the designated positions, then the visual positioning system calculates the three-dimensional space coordinates of the center of the unit circle according to the three-dimensional space coordinates of the designated positions, and finally the visual positioning system sets the position of the center of the unit circle as the origin of coordinates of the visual positioning system.
In the step 2, the target is fixed on a measuring head of a three-coordinate measuring machine, and the three-coordinate measuring machine drives the target to do circular motion along the unit circle.
In the step 2, the target is fixed on a tool of a numerical control machine tool, and the numerical control machine tool drives the target to do circular motion along the unit circle.
The threshold is one in a thousand.
After the scheme is adopted, the vision positioning system measures the moving target once to obtain the measurement coordinate (X) of the target at the moment0，Y0) And since the target actual coordinates (X, Y) satisfy X2+Y2=1, such that X0Substitution of X2+Y2In =1 to give X0Theoretically corresponding to the Y-axis coordinate Y being (1-X)0 2）1/2Since the actual coordinate Y of the target is between Y0To Y, thus to Y0Performing a first correction to correct the coordinate Y on the Y axis1Is equal to { [ (1-X)0 2）1/2+Y0]/2}, then the first correction factor K can be obtained1=Y/Y0Then through K1To X0Performing a first correction to correct the coordinate X for the first X-axis1Is equal to (K)1*X0) Subsequently combining X1And Y1Substituting formula Yi+1=[（1-Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiIn the iteration, X is madei+1And Yi+1Respectively and continuously approaching X and Y; when Y isi+1And YiWhen the difference between the values is less than the threshold value, stopping the iteration, and Xi+1And Yi+1The values are very close to X and Y, and the linear error correction coefficient K of the visual positioning system is obtained, wherein K is equal to (Y)i+1/Y0) The measurement coordinates of the visual positioning system can be corrected by a linear error correction factor K, where X0Modified to (K X)0），Y0Modified to (K X Y)0）。
Drawings
FIG. 1 is a graph of a measured coordinate curve and an actual coordinate curve of a target of the present invention.
Detailed Description
In order to further explain the technical solution of the present invention, the present invention is explained in detail by the following specific examples.
The invention discloses a method for acquiring a linear error correction coefficient of a visual positioning system, which sequentially comprises the following steps:
step 1: driving a target to do circular motion along a unit circle, and then taking the center of the unit circle as the origin of coordinates of the unit circle by the vision positioning system; the method for the vision positioning system to take the center of the unit circle as the origin of coordinates of the unit circle comprises the following steps: the target stays at a plurality of designated positions on the unit circle, the visual positioning system performs static measurement on the target staying at the designated positions to acquire three-dimensional space coordinates of the designated positions, then the visual positioning system calculates the three-dimensional space coordinates of the center of the unit circle according to the three-dimensional space coordinates of the designated positions, and finally the visual positioning system sets the center position of the unit circle as the origin of coordinates of the visual positioning system;
step 2: the vision positioning system measures the moving target once to obtain the measuring coordinate (X) of the target at the moment0,Y0) (ii) a The target can be fixed on a measuring head of a three-coordinate measuring machine, and the three-coordinate measuring machine drives the target to do circular motion along the unit circle; the target can also be fixed on a cutter of a numerical control machine tool, and the numerical control machine tool drives the target to do circular motion along the unit circle;
and step 3: mixing X0And Y0Substituting formula Y1=[（1-X0 2）1/2+Y0]In/2, the first time Y-axis correction coordinate Y is obtained by calculation1(ii) a Then Y is put0And Y1Substituting into formula K1=Y1/Y0In order to calculate the first linear error correction coefficient K1And finally K1And X0Substituting formula X1=K1*X0In the middle, inCalculating to obtain a first X-axis correction coordinate X1；
And 4, step 4: mixing X1And Y1Substituting formula Yi+1=[（1-Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiWhere i is a positive integer greater than 0, YiCorrecting the coordinates for the ith Y-axis, XiCorrection of coordinates for the ith X-axis, Yi+1Correction of coordinates for the i +1 th Y-axis, Xi+1Correcting the coordinates for the (i + 1) th X-axis; when Y isi+1And YiWhen the difference value between the two is smaller than a threshold value, stopping iteration, wherein the threshold value can be one in a thousand; then Y is put0And the last Y-axis correction coordinate Yi+1Substituting formula K = Yi+1/Y0To calculate a linear error correction coefficient K of the visual positioning system.
As shown in FIG. 1, the actual coordinates (X, Y) of the target satisfy X2+Y2=1, the amplitude of the X-axis measured coordinate curve a1 is smaller than the amplitude of the X-axis actual coordinate curve A3, and the amplitude of the Y-axis measured coordinate curve a2 is also smaller than the amplitude of the Y-axis actual coordinate curve a 4; the working principle of the invention is as follows:
as shown in FIG. 1, the vision positioning system of the present invention measures a moving target once to obtain the measured coordinates (X) of the target at that time0，Y0) And since the target actual coordinates (X, Y) satisfy X2+Y2=1, such that X0Substitution of X2+Y2In =1 to give X0Theoretically corresponding to the Y-axis coordinate Y being (1-X)0 2）1/2Since the actual coordinate Y of the target is between Y0To Y, thus to Y0Performing a first correction to correct the coordinate Y on the Y axis1Is equal to { [ (1-X)0 2）1/2+Y0]/2}, then the first correction factor K can be obtained1=Y1/Y0Then through K1To X0Performing a first correction to correct the coordinate X for the first X-axis1Is equal to (K)1*X0) Subsequently combining X1And Y1Substituting formula Yi+1=[（1-Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiIn the iteration, X is madei+1And Yi+1Respectively and continuously approaching X and Y; when Y isi+1And YiWhen the difference between the values is less than the threshold value, stopping the iteration, and Xi+1And Yi+1The values are very close to X and Y, and the linear error correction coefficient K of the visual positioning system is obtained, wherein K is equal to (Y)i+1/Y0) The measurement coordinates of the visual positioning system can be corrected by a linear error correction factor K, where X0Modified to (K X)0），Y0Modified to (K X Y)0）。
The above embodiments and drawings are not intended to limit the form and style of the present invention, and any suitable changes or modifications thereof by those skilled in the art should be considered as not departing from the scope of the present invention.
Claims (5)
1. A method for obtaining linear error correction coefficient of visual positioning system is characterized in that: sequentially comprises the following steps:
step 1: driving a target to do circular motion along a unit circle, and then taking the center of the unit circle as the origin of coordinates of the unit circle by the vision positioning system;
step 2: the vision positioning system measures the moving target once to obtain the measuring coordinate (X) of the target at the moment0,Y0）；
And step 3: mixing X0And Y0Substituting formula Y1=[（1-X0 2）1/2+Y0]In/2, the first time Y-axis correction coordinate Y is obtained by calculation1(ii) a Then Y is put0And Y1Substituting into formula K1=Y1/Y0In order to calculate the first linear error correction coefficient K1And finally K1And X0Substituting formula X1=K1*X0To calculateObtaining a first X-axis correction coordinate X1；
And 4, step 4: mixing X1And Y1Substituting formula Yi+1=[（1-Xi 2）1/2+Yi]/2、Ki+1=Yi+1/YiAnd Xi+1=Ki+1*XiWhere i is a positive integer greater than 0, YiCorrecting the coordinates for the ith Y-axis, XiCorrection of coordinates for the ith X-axis, Yi+1Correction of coordinates for the i +1 th Y-axis, Xi+1Correcting the coordinates for the (i + 1) th X-axis; when Y isi+1And YiStopping iteration when the difference value between the two is less than the threshold value; then Y is put0And the last Y-axis correction coordinate Yi+1Substituting formula K = Yi+1/Y0To calculate a linear error correction coefficient K of the visual positioning system.
2. The method of claim 1, wherein the method comprises: in step 1, the method for the vision positioning system to use the center of the unit circle as its origin of coordinates includes:
the target stays at a plurality of designated positions on the unit circle, the visual positioning system performs static measurement on the target staying at the designated positions to acquire three-dimensional space coordinates of the designated positions, then the visual positioning system calculates the three-dimensional space coordinates of the center of the unit circle according to the three-dimensional space coordinates of the designated positions, and finally the visual positioning system sets the position of the center of the unit circle as the origin of coordinates of the visual positioning system.
3. The method of claim 1, wherein the method comprises: in the step 2, the target is fixed on a measuring head of a three-coordinate measuring machine, and the three-coordinate measuring machine drives the target to do circular motion along the unit circle.
4. The method of claim 1, wherein the method comprises: in the step 2, the target is fixed on a tool of a numerical control machine tool, and the numerical control machine tool drives the target to do circular motion along the unit circle.
5. The method of claim 1, wherein the method comprises: the threshold is one in a thousand.
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