CN101975552A - Method for measuring key point of car frame based on coding points and computer vision - Google Patents

Abstract

The invention belongs to the field of reverse engineering, in particular to a method for measuring a key point of a car frame based on coding points and computer vision. The method comprises the following steps of: sticking a digital three-dimensional coding mark point to a key position of the car frame, placing a cross target and a scale stuck with coding mark points near an object, and firstly acquiring pictures of the object to be measured in different directions by using a high-precision digital camera; calculating three-dimensional coordinates corresponding to certain pixel points of the mark point through the acquired pictures; and acquiring the coordinate information of the key point of the car frame by combining an algorithm through the acquired pictures and the three-dimensional coordinate information of the marker point so as to provide data basis for subsequent car frame matching. The method for measuring the key point of the car frame enriches the three-dimensional vision measurement basic theory, lays the foundation for the reverse engineering and the three-dimensional vision detection theory, and improves the manufacture level in China.

Description

A kind of key point measuring method of the vehicle frame based on encoded point and computer vision

Technical field

The present invention relates to a kind of measuring system of reverse-engineering, in particular, the present invention relates to a kind of key point measuring system and measuring method thereof that is used for reverse-engineering based on the vehicle frame of encoded point and computer vision.

Background technology

The execution of reverse-engineering, needing has sufficient understanding to the characteristic of product with the making flow process, and many products are made up of free form surface and (are designed as motorcycle profile in the reality, mould manufacturing etc.), finish the construction of such model, must do accurate identification to the groove on the model, perforate or other features, to finish the construction of model.Simple is not enough with the accurate processing of the data of each point with the coordinate information of measuring key point by experienced slip-stick artist, like that may be consuming time oversize or error is bigger, if mix suitable instrument, then can reach the effect of getting twice the result with half the effort.

At present, the traditional measurement instrument that is used for reverse-engineering in use has many limitations.Contact type measurement for example exists speed slowly, easily to cause problems such as the wear of work and probe operation limitation, and traditional non-contact measurement, has low precision (10-100um), measuring speed significant deficiency such as (1000-12000 point/second), error be big slowly again.Existing ripe three-dimensional measurement instrument mainly contains three coordinate measuring machine, laser scanner and grating measuring instrument, and they to a certain extent can the march planar survey, but also has the following disadvantages respectively:

Described three coordinate measuring machine is high-precision instrument with contacts, can only measure a point at every turn, and measuring speed is slow, is difficult to carry out the shape-designing of curved surface, and can't measure soft object, and it is very loaded down with trivial details to operate;

Described laser scanner belongs to the non-contact optical surveying instrument, this instrument is bulky, need guide rail (normally translate stage and rotation platform), thereby make its precision, speed limited by guide rail, be difficult to realize high precision, high-speed measurement, simultaneously because the restriction of its active platform size makes its measurement range very narrow again, because the restriction of described platform machining precision and processing dimension, laser scanner is difficult to realize the three-dimensional digitized measurement of large-sized object.In same enterprise, if the test product change in size is a lot, then need just energy measurement of multiple devices, therefore can increase financial burden.In addition, laser also has certain harm to staff's eyes;

Described grating style three-dimension measuring instrument adopts grating as light source, and this instrument can be realized the non-contact three-dimensional planar survey to the object profile, has improved measuring speed (for example De Guo ATOS) greatly.But raster pattern measuring method single measurement scope is less, for large-sized object, needs to adopt repeatedly splicing to realize, therefore can add up bigger error, and is not easy to realize the overall situation control of error.

This shows, develop a kind of measuring accuracy height, speed is fast, error is little, measurement range is big measures with the key point that adapts in the configuration design based on the method for three-dimensional measurement and the measuring system of encoded point and computer vision, become industry-by-industry geometric sense detected active demand with design.

Summary of the invention

Purpose of the present invention overcomes above the deficiencies in the prior art exactly, provides a kind of key point measuring method three-dimensional digitized measurement system based on the vehicle frame of encoded point and computer vision of reliable, practical, simple operation, to remedy the defective that prior art exists.

The composition of the key point measuring method of a kind of vehicle frame based on encoded point and computer vision of the present invention comprises:

The vehicle frame that is used for the measured hole position;

Be used to set up the cross target and the measuring scale system of high-precision coordinate benchmark;

The computing machine that is used for precision control, image acquisition and data processing;

Be used to provide the coded markings point of spatial positional information;

The high precision colour or the grayscale camera that are used for images acquired;

The encoding scheme of described coded markings point and numbering are determined in advance, make each coded markings point that unique encoding number all be arranged by gauge point design difference, the number of different coding gauge point is inequality, the coded markings dot pattern is a rectangle, if background is under the situation of black or grey, all there are the circle of white in four drift angles of rectangle and the center, coded markings point can cooperate with position, vehicle frame hole high precision, and engagement process is similar to the installation process of other workpiece on being installed in position, vehicle frame hole; The relatively independent setting of described cross target system, it is shaped as cruciform, and the coded markings point of four known coordinate information is pasted on its four summits; The coded markings point of a known coordinate information is pasted in the relatively independent setting of described measuring scale system, two summit respectively, and wherein cross target and scale are same systems, and be relatively independent with the design's gauge point;

2. the key point measuring method based on the vehicle frame of encoded point and computer vision is characterized in that, it comprises following three steps:

(1) demarcate preceding the preparation: design is processing coded markings point also; Design and machining high-precision cross target are also pasted the coded markings point of known coordinate information respectively in the center of four summits of target and cross target; Design and processing measuring scale system are also pasted the coded markings point of known coordinate information respectively on two summits of scale;

(2) determine measuring basis: cross target and scale are placed within the testee imaging scope, choose several correct positions near the scene cross target and the scale is taken pictures, guarantee all to contain in each photo cross target, scale and object to be measured as far as possible;

(3) resolve the three-dimensional coordinate of vehicle frame key point, its process is:

The first step: the coded markings point of pasting the above at testee critical size position;

Near second step: described cross target and scale are placed in the testee, the principle of putting of cross target and scale is: when utilizing described high accuracy digital camera that cross target and scale are taken pictures, can photograph the coded markings point outside the thirty word target and scale at least simultaneously;

The 3rd step: utilize described high accuracy digital camera that the testee that contains cross target and scale is taken pictures, change camera site and angle and continue to take testee, gather the testee image that 3 width of cloth contain the cross target at least;

The 4th step: utilize described high accuracy digital camera to continue testee is taken pictures, all being taken up to all coded markings points of testee finishes, and the principle of taking pictures is: two adjacent images contains at least 3 public coded markings points;

The 5th step: utilize the known cross target in taken preceding 3 width of cloth images of the 3rd step and the coded markings dot information of scale, calculate 3 camera sites of described camera in the space;

The 6th step: utilize three taking location informations of resulting described camera of the 5th step, calculate outside cross target and the scale taken vehicle frame and close each coded markings above the key point and put the three-dimensional coordinate in five centers of circle;

The 7th step: resolve the coordinate of key point according to the coordinate in five centers of circle on the resulting gauge point of the 6th step, suppose P1 (x1, y1, z1) be the upper left central coordinate of circle of gauge point pattern, P2 (x2, y2, z2) be the upper right central coordinate of circle of gauge point pattern, P3 (x3, y3, z3) central coordinate of circle of gauge point pattern lower-left, P4 (x4, y4, z4) central coordinate of circle in the middle of the gauge point pattern, the coordinate of key point to be asked be made as P5 (x5, y5, z5) to resolve process as follows:

$\stackrel{\→}{p1p2}=(x2-x1,y2-y1,z2-z1),$ $\stackrel{\→}{p1p3}=(x3-x1,y3-y1,z3-z1)---\left(1\right)$

Then the normal vector of gauge point pattern is as shown in Equation (2):

$\stackrel{\→}{n}=\left|\begin{array}{ccc}i& j& k\\ x2-x1& y2-y1& z2-z1\\ x3-x1& y3-y1& z3-z1\end{array}\right|---\left(2\right)$

Formula (2) can be expressed as formula (3):

$\stackrel{\→}{n}=[(z3-z1)(y2-y1)-(y3-y1)(z2-z1),(x3-x1)(z2-z1)-(x2-x1)(z3-z1),(x3-x1)(y2-y1)-(x2-x1)(y3-y1)]---\left(3\right)$

Order

M wherein, l, n are as shown in Equation (4).

m＝(z3-z1)(y2-y1)-(y3-y1)(z2-z1)

l＝(x3-x1)(z2-z1)-(x2-x1)(z3-z1) (4)

n＝(x3-x1)(y2-y1)-(x2-x1)(y3-y1)

Its vector of unit length is

Because of indicia patterns center center of circle p4 with vertical with the plane with the straight line at key point p5 place, and

Direction identical with the normal vector direction on above-mentioned plane, the fixed distance of pattern center center of circle p4 and key point p5 is made as D again, then can satisfy following relational expression (5):

$(x5-x4,y5-y4,z5-z4)=(\frac{D\×m}{\sqrt{m^2+l^2+n^2}},\frac{D\×l}{\sqrt{m^2+l^2+n^2}},\frac{D\×n}{\sqrt{m^2+l^2+n^2}})---\left(5\right)$

Then can obtain the coordinate that key point p5 orders is:

The 8th step: utilize resulting coded markings dot information of the 6th step, calculate the three-dimensional coordinate of the coded markings point of workshop key position in taken cross target of the 4th step and the subsequent pictures outside the scale successively.

The invention has the beneficial effects as follows: adopt camera measurements of taking pictures, solved and existingly easily caused the wear of work and probe to operate problems such as limitation with quasi-instrument; Adopt the metering system of high precision monocular camera matching coding gauge point, solved the three-dimensional measurement difficult problem of large-sized object, expanded the application of three-dimension measuring system, and can satisfy the three-dimensional demand that detects and rebuild the object dimensional pattern of special material.

Description of drawings

Fig. 1: based on the process flow diagram of the key point measuring method of the vehicle frame of encoded point and computer vision;

Fig. 2: the design's coded markings point;

Fig. 3: choose 6 patterns that have nothing in common with each other by camera angle;

Fig. 4: the gauge point pattern coordinate synoptic diagram that extracts;

Fig. 5: the figure that extracts key point.

Embodiment

A kind of embodiment of key point measuring method of the vehicle frame based on encoded point and computer vision is: design is processing coded markings point also, high precision cross target, measuring scale system; Paste the coded markings point of the above at testee critical size position; Described cross target and scale are placed near the testee, the principle of putting of cross target and scale is: when utilizing described high accuracy digital camera that cross target and scale are taken pictures, can photograph the coded markings point outside the thirty word target and scale at least simultaneously; Utilize described high accuracy digital camera that the testee that contains cross target and scale is taken pictures, change camera site and angle and continue to take testee, gather the testee image that 3 width of cloth contain the cross target at least; Utilize described high accuracy digital camera to continue testee is taken pictures, all being taken up to all coded markings points of testee finishes; Utilize the known cross target in taken preceding 3 width of cloth images and the coded markings dot information of scale, calculate 3 camera sites of described camera in the space; Utilize three taking location informations of the resulting described camera of previous step, calculate the three-dimensional coordinate of the coded markings point of taken vehicle frame key point outside cross target and the scale; Resulting gauge point coordinate of step resolves the coordinate of key point in the utilization, and the course of work of whole proposal as shown in Figure 1.

The key point measuring method job step that the present invention is based on the vehicle frame of encoded point and computer vision was divided into for three steps:

(1) demarcate preceding the preparation: design is processing coded markings point also, as shown in Figure 2; Design and machining high-precision cross target are also pasted the coded markings point of known coordinate information respectively in four summits of target and its center; Design and processing measuring scale system are also pasted the coded markings point of known coordinate information respectively on two summits of scale;

(2) determine measuring basis: cross target and scale are placed within the testee imaging scope, choose several correct positions near the scene cross target and the scale is taken pictures, guarantee all to contain in each photo cross target, scale and object to be measured as far as possible;

(3) resolve the three-dimensional coordinate of vehicle frame key point, its process is:

The first step: the coded markings point of pasting the above at testee critical size position;

Near second step: described cross target is placed in the testee, the principle of putting of cross target is: when utilizing described high accuracy digital camera that the cross target is taken pictures, can photograph the coded markings point outside the thirty word target at least simultaneously;

The 3rd step: utilize described high accuracy digital camera that the testee that contains cross target and scale is taken pictures, change camera site and angle and continue to take testee, gather the testee image that at least 3 width of cloth contain the cross target;

The 4th step: utilize described high accuracy digital camera to continue testee is taken pictures, all be taken up to all coded markings points of testee and finish, the principle of taking pictures is: two adjacent images contains at least 3 public coded markings points, as shown in Figure 3;

The 5th step: utilize the known cross target in taken preceding 3 width of cloth images of the 3rd step and the coded markings dot information of scale, calculate 3 camera sites of described camera in the space;

The 6th step: utilize three taking location informations of resulting described camera of the 5th step, calculate outside cross target and the scale taken vehicle frame and close each coded markings above the key point and put the three-dimensional coordinate in five centers of circle;

The 7th step: resolve the coordinate of key point according to the coordinate in five centers of circle on the resulting gauge point of the 6th step, suppose P1 (x1, y1, z1) be the upper left central coordinate of circle of gauge point pattern, P2 (x2, y2, z2) be the upper right central coordinate of circle of gauge point pattern, P3 (x3, y3, z3) central coordinate of circle of gauge point pattern lower-left, P4 (x4, y4, z4) central coordinate of circle in the middle of the gauge point pattern, the coordinate of key point to be asked be made as P5 (x5, y5, z5) to resolve process as follows:

$\stackrel{\→}{p1p2}=(x2-x1,y2-y1,z2-z1),$ $\stackrel{\→}{p1p3}=(x3-x1,y3-y1,z3-z1)---\left(1\right)$

Then the normal vector of gauge point pattern is as shown in Equation (2):

$\stackrel{\→}{n}=\left|\begin{array}{ccc}i& j& k\\ x2-x1& y2-y1& z2-z1\\ x3-x1& y3-y1& z3-z1\end{array}\right|---\left(2\right)$

Formula (2) can be expressed as formula (3).

$\stackrel{\→}{n}=[(z3-z1)(y2-y1)-(y3-y1)(z2-z1),(x3-x1)(z2-z1)-(x2-x1)(z3-z1),(x3-x1)(y2-y1)-(x2-x1)(y3-y1)]---\left(3\right)$

Order

M wherein, l, n are as shown in Equation (4).

m＝(z3-z1)(y2-y1)-(y3-y1)(z2-z1)

l＝(x3-x1)(z2-z1)-(x2-x1)(z3-z1) (4)

n＝(x3-x1)(y2-y1)-(x2-x1)(y3-y1)

Vector of unit length is

Because of the straight line at p4 and p5 place is vertical with the plane, and

Direction identical with the normal vector direction on above-mentioned plane, the distance of p4 and p5 is D again, then can satisfy following formula (5):

$(x5-x4,y5-y4,z5-z4)=(\frac{D\×m}{\sqrt{m^2+l^2+n^2}},\frac{D\×l}{\sqrt{m^2+l^2+n^2}},\frac{D\×n}{\sqrt{m^2+l^2+n^2}})---\left(5\right)$

Then can obtain the coordinate that key point p5 orders is:

The 8th step: utilize resulting coded markings dot information of the 6th step, calculate the three-dimensional coordinate of the coded markings point of workshop key position in taken cross target of the 4th step and the subsequent pictures outside the scale successively, as shown in Figure 5.

The maximum difference of the portable grating three-dimension measuring system of the present invention and prior art is that measuring equipment only needs single high accuracy digital camera, need not projection source information, thereby has solved the difficult problem of the three-dimensional measurement of black object and reflective object.The difference of the present invention and existing this quasi-instrument also is: need not any special hardware equipment, and do not need special light source customized; Software then is at this instrument self-written measuring programs; The cross target of demarcating is relatively independent, and main effect provides the high-precision coordinate benchmark.

In sum, the advantage of single order high precision large-sized object three-dimensional digitized measurement system of the present invention is:

(1) volume is little, and is in light weight, is convenient for carrying, and can arbitrarily remove to the measured object position and do in-site measurement;

(2) adopt no guide rail structure, the working method freedom, scalable is arbitrarily angled does comprehensive measurement, has solved the existing problems such as limitation that easily cause the wear of work and probe to operate with quasi-instrument simultaneously;

(3) solve three-dimensional digitized measurement effectively, be fit to the measurement of all size and shaped objects, measure applied widely large-sized object;

(4) measuring accuracy height can reach 0.01～0.03mm.

The present invention adopts monocular high precision camera, makes it when carrying out the large-sized object measurement, and measuring accuracy is very high, and is widely used, and the body surface (as workpiece, model, mould, sculpture, human body etc.) that is suitable for any material carries out three-dimensional digitized measurement.

Below schematically the present invention and embodiment thereof are described, this description does not have limitation, and shown in the accompanying drawing also is one of embodiments of the present invention.So; if those of ordinary skill in the art is enlightened by it; under the situation that does not break away from the invention aim; adopt the same base part of other form or each component layouts mode of other form; without creationary technical scheme similar and the embodiment of designing, all should belong to protection scope of the present invention to this technical scheme.

Claims (2)

1. the key point measuring method based on the vehicle frame of encoded point and computer vision is characterized in that it comprises the vehicle frame that is used for the measured hole position, is used to provide the coded markings point of spatial positional information, is used to set up the cross target and the scale of high-precision coordinate benchmark; The computing machine that is used for precision control, image acquisition and data processing is used for the high precision colour or the grayscale camera of images acquired;

The described design that is used to provide the coded markings point of spatial positional information, it is characterized in that, described coded markings dot pattern is a rectangle, if background is under the situation of black or grey, its coding pattern is the circular arc of white, each circular arc cuts from same annulus, and all there are the circle of white in four drift angles of the pattern of rectangle and the center, the center of circle of described center is identical with the center of circle of annulus, the encoding scheme of each coded markings point and numbering are determined in advance, make each coded markings point that unique encoding number all be arranged by gauge point design difference, the number of different coding gauge point is inequality, coded markings point can cooperate with position, vehicle frame hole high precision, and engagement process is similar to the installation process of other workpiece on being installed in position, vehicle frame hole, the fixed distance in the key point and the center of circle, center;

Describedly be used to set up the cross target system of high-precision coordinate benchmark, the design of measuring scale system, it is characterized in that, it is shaped as cruciform described cross target, its four summits and cross center are pasted the coded markings point of a known coordinate information respectively, the coded markings point of a known coordinate information is pasted on two summits of described scale respectively, wherein cross target and scale are same systems, and be relatively independent with the design's gauge point;

The design of described coded markings point, cross target system, measuring scale system, determine measuring basis, it is characterized in that, cross target and scale are placed within the testee imaging scope, choose several correct positions near the scene cross target and the scale is taken pictures, guarantee all to contain in each photo cross target, scale and object to be measured as far as possible.

2. according to the key point measuring method of the described a kind of vehicle frame based on encoded point and computer vision of claims 1, it is characterized in that it comprises the steps:

The first step: the coded markings point of pasting the above at testee critical size position;

Near second step: described cross target and scale are placed in the testee, the principle of putting of cross target and scale is: when utilizing described high accuracy digital camera that cross target and scale are taken pictures, can photograph the coded markings point outside the thirty word target and scale at least simultaneously;

The 3rd step: utilize described high accuracy digital camera that the testee that contains cross target and scale is taken pictures, change camera site and angle and continue to take testee, gather the testee image that 3 width of cloth contain described cross target and scale at least;

The 4th step: utilize described high accuracy digital camera to continue testee is taken pictures, all being taken up to all coded markings points of testee finishes, and the principle of taking pictures is: two adjacent images contains at least 3 public coded markings points;

The 5th step: utilize the known cross target in taken preceding 3 width of cloth images of the 3rd step and the coded markings dot information of scale, calculate 3 camera sites of described camera in the space;

The 6th step: utilize three taking location informations of resulting described camera of the 5th step, calculate outside cross target and the scale taken vehicle frame and close each coded markings above the key point and put the three-dimensional coordinate in five centers of circle;

The 7th step: resolve the coordinate of key point according to the coordinate in five centers of circle on the resulting gauge point of the 6th step, suppose P1 (x1, y1, z1) be the upper left central coordinate of circle of gauge point pattern, P2 (x2, y2, z2) be the upper right central coordinate of circle of gauge point pattern, P3 (x3, y3, z3) central coordinate of circle of gauge point pattern lower-left, P4 (x4, y4, z4) central coordinate of circle in the middle of the gauge point pattern, the coordinate of key point to be asked be made as P5 (x5, y5, z5) to resolve process as follows:

$\stackrel{\→}{p1p2}=(x2-x1,y2-y1,z2-z1),$ $\stackrel{\→}{p1p3}=(x3-x1,y3-y1,z3-z1)---\left(1\right)$

Then the normal vector of gauge point pattern is as shown in Equation (2):

$\stackrel{\→}{n}=\left|\begin{array}{ccc}i& j& k\\ x2-x1& y2-y1& z2-z1\\ x3-x1& y3-y1& z3-z1\end{array}\right|---\left(2\right)$

Formula (2) can be expressed as formula (3):

$\stackrel{\→}{n}=[(z3-z1)(y2-y1)-(y3-y1)(z2-z1),(x3-x1)(z2-z1)-(x2-x1)(z3-z1),(x3-x1)(y2-y1)-(x2-x1)(y3-y1)]---\left(3\right)$

Order

M wherein, l, n be as shown in Equation (4):

m＝(z3-z1)(y2-y1)-(y3-y1)(z2-z1)

l＝(x3-x1)(z2-z1)-(x2-x1)(z3-z1) (4)

n＝(x3-x1)(y2-y1)-(x2-x1)(y3-y1)

Its vector of unit length is

Because of indicia patterns center center of circle p4 with vertical with the plane with the straight line at key point p5 place, and

Direction identical with the normal vector direction on above-mentioned plane, the fixed distance of pattern center center of circle p4 and key point p5 is made as D again, then can satisfy following relational expression (5):

$(x5-x4,y5-y4,z5-z4)=(\frac{D\×m}{\sqrt{m^2+l^2+n^2}},\frac{D\×l}{\sqrt{m^2+l^2+n^2}},\frac{D\×n}{\sqrt{m^2+l^2+n^2}})---\left(5\right)$

Then can obtain the coordinate that key point p5 orders is:

$(\frac{D\×m}{\sqrt{m^2+l^2+n^2}}+x4,$ $\frac{D\×l}{\sqrt{m^2+l^2+n^2}}+y4,$ $\frac{D\×n}{\sqrt{m^2+l^2+n^2}}+z4)$

The 8th step: utilize resulting coded markings dot information of the 6th step, calculate the three-dimensional coordinate of the coded markings point of workshop key position in taken cross target of the 4th step and the subsequent pictures outside the scale successively.

Images