CN111462330B - Measuring viewpoint planning method based on plane normal projection - Google Patents
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
- G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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Abstract
The invention discloses a measuring viewpoint planning method based on plane normal projection, which is characterized in that a measured curved surface is divided into a plurality of areas in three-dimensional modeling software, and a corresponding reference plane and a projection reference sketch are established; dividing the projection reference sketch into a plurality of sketch sub-areas by combining the part characteristics, the equipment parameters and the measurement process parameters; then taking the normal direction of the reference sketch plane as a projection direction, taking the sketch sub-area as a projection object, and performing projection segmentation on the measured curved surface; then, checking whether the measurement view field can cover the segmented curved surface or not according to the constraint parameters of the measurement equipment; and finally, offsetting the center point of each segmented sub-curved surface along the normal direction by a standard measurement distance to obtain a free-form surface measurement viewpoint. The invention has small calculated amount and convenient modification, can shorten the planning time of the measuring viewpoint and improve the working efficiency. The invention avoids the influence of local curvature mutation in the curved surface on the overall measurement effect, and can ensure that the measurement area covers the whole measured curved surface.
Description
Technical Field
The invention belongs to the technical field of free-form surface measurement viewpoint planning, and particularly relates to a measurement viewpoint planning method based on plane normal projection.
Background
The automatic measurement system based on the surface structured light measuring instrument has the characteristics of high measurement precision, non-contact type and high measurement efficiency, and is already applied to three-dimensional reconstruction of a plurality of products with complex curved surfaces, such as airplanes, automobiles and the like. The measurement viewpoint planning of the surface structured light measuring instrument is one of key technologies, and not only directly influences the system measurement result, but also is a necessary link for planning the joint track of the robot. Besides the characteristics of the measured part, the measurement viewpoint planning also needs to consider the field range, the standard measurement distance and other constraints of the structured light measurement system.
At present, the planning of a measurement viewpoint for the automatic measurement of structured light is mostly completed by adopting a teaching programming mode, and the mode is used for teaching through point positions of all robots needing to be parked and recording the positions of all the points. When the size of the part is large or the curved surface characteristics are complex, the method is time-consuming and cannot ensure that the finally generated measurement viewpoint can completely cover the area to be measured. Meanwhile, the robot teaching programming track planning time is long, and the equipment service time is occupied, so that the efficiency is low, and the field production progress is seriously influenced.
Disclosure of Invention
The invention aims to provide a measuring viewpoint planning method based on plane normal projection, and aims to provide a curved surface shape measuring viewpoint planning method which is small in calculation amount and convenient and fast to operate so as to generate a measuring viewpoint sequence meeting measuring requirements.
The invention is mainly realized by the following technical scheme: a measuring viewpoint planning method based on plane normal projection mainly comprises the following steps:
step S100: dividing a measured part into m areas in three-dimensional modeling software, and establishing a reference plane and a projection outline sketch for each area;
step S200: dividing the projection outline sketch of each region into a plurality of projection sketch sub-regions, and setting the projection sketch sub-region plane group of the ith region as { S'i,1,S'i,2,S'i,3,…S'i,nAnd taking the sub-region of the projection sketch as a projection object, taking the normal direction of the reference plane as a projection direction, and respectively projecting and dividing the measured curved surface to obtain a curved surface group { S of the divided sub-regioni,1,Si,2,Si,3,…Si,nN is the number of the divided sub-regions;
step S300: with the sub-region S dividedi,jIs an object, and a sub-region Si,jMeasuring direction vector of
Is the projection direction, perpendicular to
The camera plane is projected to obtain a view field subregion plane group (S) of the segmentation subregion curved surface group in the camera plane "i,1,S”i,2,S”i,3,…S”i,n}；
Step S400: calculation of { S "i,1,S”i,2,S”i,3,…S”i,nWhether the size of each subarea in the screen is within the measuring range of the equipment or not, if the size of each subarea is S "i,1,S”i,2,S”i,3,…S”i,nIf the sizes of the surfaces are smaller than the size of the view field of the surface structured light measuring instrument, the coverage inspection is passed, otherwise, the curved surface segmentation is carried out again and the coverage inspection is carried out;
step S500: calculating a segmentation sub-surface Si,jAnd the vector of the measuring direction of the curved surface
The direction offset distance D is obtained to obtain the measurement viewpoint P of the segmentation curved surfacei,j(xi,j,yi,j,zi.j) And D is a standard measuring distance of the measuring equipment.
In order to better implement the present invention, in step S100, when dividing the region of the part, an interactive method is used to perform region division in the three-dimensional modeling software, and when dividing the region, it should be ensured that the features of the part in the same region are similar and there is no region with a large curvature.
To better implement the present invention, further, in step S200, the plane group { S'i,1,S'i,2,S'i,3,…S'i,nIn the time of the measurement, the size of the sub-regions of the sketch is ensured to be smaller than the size of the view field of the surface structured light measuring instrument, and the area of the overlapped region among the sub-regions of the sketch is not less than 10% of the area of each sub-region of the sketch.
To better implement the invention, further, a curved surface S is determinedi,jMeasuring direction vector of
The method mainly comprises the following steps:
step S01: obtaining curved surface S in three-dimensional modeling softwarei,jEach corner point, denoted as pi,j,1,pi,j,2,pi,j,3…pi,j,kK is the correspondence of the curved surfaceThe number of angular points (k) is more than or equal to 3;
step S02: establishing a general plane equation expression: ax + By + Cz + D is 0 and passes through the curved surface Si,jEach corner point p ofi,j,1,pi,j,2,pi,j,3…pi,j,kFitting and calculating to obtain values of A, B, C and D;
step S03: normal vector corresponding to the plane
I.e. the curved surface Si,jMeasuring direction vector of
In order to better implement the invention, further, the three-dimensional modeling software is CATIA.
In order to better realize the invention, the field of view of the surface structured light measuring instrument is set to be w × h, for the ith area, a rectangular drawing command is called in a sketch module, a rectangular projection outline sketch with the length and width divided into a and b is drawn, the projection outline sketch is divided into n projection sketch sub-areas with the size of c × d, and the length and width of the edge of the projection outline sketch and the overlapping area of the adjacent projection sketch sub-areas are respectively e and f; the a, b, c, d, e, f, w, h, M and N satisfy the following relations:
the invention has the beneficial effects that:
the method is based on the original CAD model, has simple calculation process, small calculation amount and convenient modification, can shorten the planning time of the measuring viewpoint and improve the working efficiency; the measurement direction of the curved surface is calculated based on the curved surface angular point fitting plane, so that the influence of local curvature mutation in the curved surface on the overall measurement effect is avoided; the coverage of the measuring view field is checked on the divided curved surfaces, and the measuring area can be ensured to cover the whole measured curved surface.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic diagram of the present invention for partitioning sub-regions;
FIG. 3 is a schematic diagram illustrating the sub-division of a projection sketch according to the present invention;
FIG. 4 is a diagram illustrating the relationship between the projection sketch sub-area, the segmentation sub-area and the field of view sub-area according to the present invention.
The method comprises the following steps of 1-a curved surface to be measured, 2-a reference plane, 3-a camera plane, 4-a segmentation sub-region, 5-a projection sketch sub-region, 6-a view field sub-region, 7-a projection outline sketch, 8-a surface structure light measuring instrument, 9-a measuring viewpoint and 10-a projection sketch sub-region overlapping region.
Detailed Description
Example 1:
a method for planning a measurement viewpoint 9 based on planar normal projection, as shown in fig. 1 to 4, the method for planning a free-form surface measurement viewpoint 9 according to the present invention comprises the following steps:
1) as shown in fig. 2, in three-dimensional modeling software such as CATIA, a surface model to be measured is loaded, and is divided into m regions by an interactive method, and a reference plane 2 is established for each region.
2) As shown in fig. 3, the field size of the surface structured light measuring instrument 8 is w × h, for the ith area, a rectangular drawing command is called in the sketch module, a rectangular projection outline sketch 7 with length and width being divided into a and b is drawn, and the drawing is divided into n projection sketch sub-areas 5 with size of c × d, wherein the length and width of the edge of the projection outline sketch 7 and the overlapping area 10 of the adjacent projection sketch sub-areas are e and f respectively.
a, b, c, d, e, f, w, h, M.N satisfy the following relationship:
3) using the projection sketch sub-area 5 as a projection object, using the normal direction of the reference plane 2 as a projection direction, calling a projection command in the generative curved surface design, projecting the projection command on the measured curved surface 1 and dividing the measured curved surface 1 to obtain a curved surface group { S ] of the divided sub-area 4i,1,Si,2,Si,3,…Si,n}；
4) Obtaining a curved surface Si,jEach corner point pi,j,1,pi,j,2,pi,j,3…pi,j,kEstablishing a general plane equation expression: ax + By + Cz + D is 0 and passes through each corner point pi,j,1,pi,j,2,pi,j,3…pi,j,kThe values of A, B, C and D are obtained by fitting calculation of the coordinates. Wherein k is the number of corner points corresponding to the curved surface (k is more than or equal to 3),
5) defining a measurement direction vector of the curved surface
With the sub-curved surface S after divisioni,jIs the object of
Is a projection direction perpendicular to
The camera plane 3 as a projection, a plane group { S } of a field of view subregion 6 of the segmentation subregion 4, the curved surface group being on the camera plane 3 is obtained "i,1,S”i,2,S”i,3,…S”i,n}。
6) Is provided with S "i,jHas a size of ui,j×vi,jIf u isi,j×vi,jIf the sizes of the field coverage inspection areas are smaller than the standard field size w x h of the measuring equipment, the field coverage inspection is passed, otherwise, the inspection is carried out according to the plane S of the field sub-area 6ijThe result of comparing the length and width with w and h automatically adjusts c and d and regenerates the segmentation curved surface and the plane S of the view field subregion 6ijThe field coverage check is passed.
7) Calculating a segmentation curved surface Si,nAnd the vector of the measuring direction of the curved surface
Obtaining the measurement viewpoint 9P of the segmentation curved surface by the direction offset distance Di,j(xi,j,yi,j,zi.j) And D is a standard measuring distance of the measuring equipment.
The method is based on the original CAD model, has simple calculation process, small calculation amount and convenient modification, can shorten the planning time of the measurement viewpoint 9 and improve the working efficiency; the measurement direction of the curved surface is calculated based on the curved surface angular point fitting plane, so that the influence of local curvature mutation in the curved surface on the overall measurement effect is avoided; the coverage of the measuring view field is checked on the divided curved surfaces, and the measuring area can be ensured to cover the whole measured curved surface 1.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (5)
1. A measuring viewpoint planning method based on plane normal projection is characterized by mainly comprising the following steps:
step S100: dividing a measured part into m areas in three-dimensional modeling software, and establishing a reference plane and a projection outline sketch for each area;
step S200: dividing the projection outline sketch of each region into a plurality of projection sketch sub-regions, and recording the projection sketch sub-region plane group of the ith region as
Then, taking the sub-region of the projection sketch as a projection object, taking the normal direction of the reference plane as a projection direction, and respectively projecting and dividing the measured curved surface to obtain a sub-region-divided curved surface group
Wherein n is the number of the divided sub-regions;
step S300: in the divided sub-region
Is an object and a sub-area
Measuring direction vector of
Is the projection direction, perpendicular to
The camera plane is projected to obtain a view field sub-area plane group of the segmentation sub-area curved surface group on the camera plane
；
Step S400: computing
Whether the size of each sub-area is within the measuring range of the equipment or not, if so
If the sizes of the curved surface and the surface structure light measuring instrument are smaller than the size of the view field of the surface structure light measuring instrument, the coverage inspection is passed, otherwise, the curved surface segmentation is carried out again and the coverage inspection is carried out;
step S500: computing a segmented sub-surface
And the vector of the measuring direction of the curved surface
The direction is offset by a distance D to obtain a segmentation sub-curved surface
Measuring viewpoint of
And D is a standard measuring distance of the measuring equipment.
2. The method as claimed in claim 1, wherein in step S200, the projection sketch sub-area plane group is divided
In the time, the size of the sub-regions of the sketch is ensured to be smaller than the size of the view field of the surface structured light measuring instrument, and the area of the overlapped region between the sub-regions of the sketch is not less than 10% of the area of each sub-region.
3. The method of claim 1, wherein determining the curved surface is based on a planar normal projection measurement viewpoint planning method
Measuring direction vector of
The method comprises the following steps:
step S01: obtaining curved surfaces in three-dimensional modeling software
Each corner point, mark
K is the number of corner points corresponding to the curved surface, wherein;
step S02: establishing a general plane equation expression:
and through a curved surface
Each corner point of
Fitting and calculating to obtain values of A, B, C and D;
step S03: normal vector corresponding to the plane
I.e. the curved surface
Measuring direction vector of
。
4. The method as claimed in claim 1, wherein the three-dimensional modeling software is CATIA.
5. The method according to claim 1, wherein the field of view of the planar normal projection is set to be w × h, for the ith area, a rectangular drawing command is called in the sketch module to draw a rectangular projection outline sketch with length and width being a and b, and the projection outline sketch is divided into n projection sketch sub-areas with size of c × d, and the length and width of the edge of the projection outline sketch and the overlapping area of the adjacent projection sketch sub-areas are e and f; the a, b, c, d, e, f, w, h, M and N satisfy the following relations:
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