CN1609548A - Automatic working out system for laser scanning head stroke used for three-dimensional measurement machine tool - Google Patents

Abstract

The present invention relates to the automatic stroke establishing system for laser measurement head for measuring machine tools. After positioning reference point, rack, planar stripe projector and CCD camera are installed, the system is first initialized and the workpiece is then measured. The present invention may be used in the measurement of workpiece needing repeated measurement in high speed and high work efficiency.

Description

The laser scanning head stroke that is used for the three-dimensional measurement lathe is formulated system automatically

Technical field:

The present invention relates to a kind of laser scanning head stroke that is used for the three-dimensional measurement lathe and formulate system automatically, particularly relate to a kind of simple three-dimensional information that the laser scan type three-coordinate measuring machine-tool can obtain the two-dimensional signal and the workpiece shape of measured workpiece putting position automatically that is used for, automatically formulate the swash width of laser scanning head according to above-mentioned information, and be converted to digital control system discernible to be the motion of code control laser scanning head, to belong to technical field of image processing.

Background technology:

In the large-scale three dimensional workpiece calibration machine tool of using the realization of laser scanning head technology, the stroke that must formulate laser scanning head makes it to scan fully the surface of measured workpiece to obtain the complete shape information of measured workpiece.Because the gait of march of laser scanning head is slower, therefore when specifying the laser scanning head swash width, to formulate the best stroke of laser scanning head according to the shape of the putting position of measured workpiece and measured workpiece, shorten the time of single sweep operation as far as possible.When some was needed the workpiece of repeated measurement, operating personnel must carry out the stroke programing work of workpiece location and laser scanning head repeatedly, and the workload that this has increased the operator is unfavorable for improving the efficient of surveying work.

Summary of the invention:

The purpose of this invention is to provide a kind of laser scanning head stroke that is used for the three-dimensional measurement lathe and formulate system automatically, the laser scanning head stroke be can formulate automatically and the putting position of measured workpiece and the simple three-dimensional information of workpiece shape obtained automatically, and by the artificial best stroke of formulating laser scanning head automatically of these information replacements, being converted to digital control system afterwards discernible is the motion of code control laser scanning head.Adopt this system can reduce operator's working strength, improve the work efficiency that laser scan type is measured lathe.Because native system combines CCD imaging technique and image processing techniques in design, so this system works speed is fast, can finish the formulation work of laser scanning head swash width at short notice.

Technical solution of the present invention is achieved in that the laser scanning head stroke that is used to measure lathe formulates system automatically, by location reference point, and system initialization sample, support, the noodles line projector, the CCD camera, image pick-up card, industrial PC and post-processed program are formed.Its workflow is as follows:

One, work as location reference point, support after the noodles line projector and CCD camera install, at first carries out the initial work of native system, and initial work comprises following each step:

1, accurate measurement and positioning reference point is at work top coordinate system o _px _py _pz _pUnder fixed position coordinate (x _r, y _r);

2, the system initialization sample is placed on the work top, and accurately measures it at work top coordinate system o _px _py _pz _pUnder putting position coordinate (x _s, y _s);

3, open the noodles line projector, the noodles line is projected on the system initialization sample;

4, start the noodles line projection image that the CCD camera obtains the system initialization sample;

5, by image pick-up card the image that the CCD camera obtains is read in computing machine;

7, with (x _r, y _r), (x _s, y _s), CCD camera optical axis becomes angle α with work top _c, noodles line projector optical axis becomes angle α with work top _pThe input computing machine;

8, start-up system initialize routine, and according to above-mentioned input quantity calculating sensor structural parameters matrix A _s, system deviation compensation matrix A _b, transformation matrix of coordinates A _tThe main flow process of system initialization routine is as follows:

(1) becomes angle α with work top according to CCD camera optical axis _c, noodles line projector optical axis becomes angle α with work top _pCalculating sensor structural parameters matrix A _s

(2) ccd image is handled, obtained on the striations frame of each point and deposit body coordinate (x _d, y _d);

(3) with sensor construction parameter matrix A _sDeposit body coordinate (x with the frame of each point on the striations _d, y _d) substitution noodles line structural light measurement formula, obtain on the striations each point at measurement coordinate system o _sx _sy _sz _sUnder three-dimensional coordinate (x _s, y _s, z _s);

(4) three-dimensional coordinate according to each point on the striations carries out match to the surface of system initialization sample, obtains fitting surface S ' _s(u, v);

(5) deposit the surface fitting curved surface S of system for computer initialization sample more in advance in _s(u is v) with S ' _s(u v), calculates system deviation compensation matrix A _b

(6) according to reference location point (x _r, y _r) and α _cCalculating is by CCD camera coordinate system o _cx _cy _cz _cTo work top coordinate system o _px _py _pz _pTransformation matrix of coordinates A ' _t, and according to the actual putting position (x of system initialization sample _s, y _s) to A ' _tRevise, obtain revised transformation matrix of coordinates A _t

(7) with A _b, A _s, A _tDeposit computing machine in; Sensor construction parameter matrix A _s, system deviation compensation matrix A _b, transformation matrix of coordinates A _tIn case after determining, do not change as each parts relative position of native system, then A _b, A _s, A _tDo not change.

Two, finish after the system initialization, can use native system that workpiece is carried out formal measurement.The formal surveying work of native system comprises following each step:

1, measured workpiece is placed on the work top, opens the noodles line projector, the noodles line is projected on the measured workpiece;

2, start the noodles line projection image that the CCD camera obtains measured workpiece;

3, by image pick-up card the image that the CCD camera obtains is read in computing machine;

4, start the laser scanning head swash width and formulate program, formulate the optimum scanning stroke of laser scanning head automatically, and the control laser scanning head moves.It is as follows that the laser scanning head swash width is formulated the main flow process of program:

(1) ccd image is handled, obtained on the striations frame of each point and deposit body coordinate (x _d, y _d);

(2) with sensor construction parameter matrix A _sDeposit body coordinate (x with the frame of each point on the striations _d, y _d) substitution noodles line structural light measurement formula, obtain on the striations each point at measurement coordinate system o _sx _sy _sz _sUnder three-dimensional coordinate (x _s, y _s, z _s);

(3) three-dimensional coordinate according to each point on the striations carries out match to the surface of system initialization sample, obtains fitting surface S _t ^{S '}(u, v);

(4) application system deviation compensation matrix A _bTo fitting surface S _t ^{S '}(u v) carries out deviation compensation, obtains S _t ^s(u, v);

(5) use transformation matrix of coordinates A _tWith S _t ^s(u is v) by CCD camera coordinate system o _cx _cy _cz _cBe transformed into work top coordinate system o _px _py _pz _p, get S _t ^p(u, v);

(6) ask o _px _py _pz _pFitting surface S under the coordinate system _t ^p(u v) to the projection of work top, gets the C of drop shadow curve _tAnd C (u), _t(u) carry out interpolation operation, determine the optimum level face two-dimensional scan stroke of laser scanning head;

(7) according to the two-dimentional stroke of laser scanning head to fitting surface S _t ^p(u v) carries out vertical section and handles, and obtains the vertical height value in the laser scanning head stroke;

(8) stroke with laser scanning head is converted to the discernible both codes of numerical control system system, and carries out communication with the digital control system of measuring lathe, will be that code send digital control system;

Support is positioned at the top of cantilevered rail, and is parallel with work top.The CCD camera and the noodles line projector are separately fixed on the support, and wherein effective projection scope of the field range of CCD camera and the noodles line projector can cover effective workpiece placement area of work top.Location reference point is fixed on the work top.

The noodles line projector projects a plurality of optical planes in the space, these a plurality of optical planes intercept many plane curves mutually with the testee surface, and the point on the curve is measurand.Each optical plane forms the perspective corresponding relation with the picture plane respectively.Its how much imaging relations as shown in Figure 2.

Get k optical plane for object is discussed, on k optical plane with 1 o _L ^(k)For initial point is set up plane coordinate system o _L ^(k)x _L ^(k)y _L ^(k), symbol (k) is represented k optical plane.This optical plane with as the perspective corresponding relation on plane be:

$\mathrm{\&rho;}\left[\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="X\; Y"\; filenames="A20031010993300172.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 1\end{array}\right]=\left[\begin{array}{ccc}{{\mathrm{fr}}_1}^{\left(k\right)}& {{\mathrm{fr}}_2}^{\left(k\right)}& {{\mathrm{ft}}_x}^{\left(k\right)}\\ {{\mathrm{fr}}_4}^{\left(k\right)}& {{\mathrm{fr}}_5}^{\left(k\right)}& {{\mathrm{ft}}_y}^{\left(k\right)}\\ {{\mathrm{fr}}_7}^{\left(k\right)}& {{\mathrm{fr}}_8}^{\left(k\right)}& {{\mathrm{ft}}_z}^{\left(k\right)}\end{array}\right]$

In the formula:

(r ₁ ^(k)r ₄ ^(k)r ₇ ^(k)) and (r ₂ ^(k)r ₅ ^(k)r ₈ ^(k))---be respectively x _L ^(k)Axle and y _L ^(k)Axle is at CCD

The camera coordinate system

o _cx _cy _cz _cUnder unit side

To vector.

(t _x ^(k)t _y ^(k)t _z ^(k))---translation vector, i.e. o _L ^(k)Point is at CCD camera coordinate system o _cx _cy _cz _cCoordinate figure under the coordinate system.

K optical plane of definable is at CCD camera coordinate system o thus _cx _cy _cz _cPlane equation under the coordinate system is:

a _kx _c+b _ky _c+c _kz _c＝d _k

A in the formula _k, b _k, c _kAnd d _kDetermine by expression:

(a _kb _kc _k)＝(r ₁ ^(k)r ₄ ^(k)r ₇ ^(k))×(r ₂ ^(k)r ₅ ^(k)r ₈ ^(k))

d＝(a _kb _kc _k)·(t _x ^(k)t _y ^(k)t _z ^(k)) ^T

Promptly

a _k＝r ₄ ^(k)r ₈ ^(k)-r ₅ ^(k)r ₇ ^(k)

b _k＝r ₂ ^(k)r ₇ ^(k)-r ₁ ^(k)r ₈ ^(k)

c _k＝r ₁ ^(k)r ₅ ^(k)-r ₂ ^(k)r ₄ ^(k)

d _k＝a _kt _x ^(k)+b _kt _y ^(k)+c _kt _z ^(k)

When considering the lens distortion of CCD camera, the perspective transform formula of CCD camera can be expressed as:

X _d＝s _xd _x(u-u ₀)

Y _d＝d _y(v-v ₀)

$f=\frac{r_1{x}_w+r_2{y}_w+r_3{z}_w+t_x}{r_{7}x+r_8{y}_w+r_9{z}_w+t_z}=X_d(1+k_1{r}^2)$

$f\frac{r_4{x}_w+r_5{y}_w+r_6{z}_w+t_x}{r_{7}x+r_8{y}_w+r_9{z}_w+t_z}=Y_d(1+k_1{r}^2)$

Wherein (u, v) coordinate under the body coordinate system is a bit deposited at frame in the space; (u ₀, v ₀) deposit true origin coordinate under the body coordinate system for frame; d _xBe the horizontal direction centre distance of CCD camera as adjacent photosensitive unit in the plane; d _yBe the vertical direction centre distance of CCD camera as adjacent photosensitive unit in the plane; The parameter that needs to determine is R, T, f, k ₁And s _x, these parameters are divided into two classes: a class is external parameter R and T, it determines the relation between object space three-dimensional system of coordinate and the CCD camera three-dimensional system of coordinate.The 2nd, inner parameter f, k ₁And s _x, it determine object point in CCD camera three-dimensional system of coordinate three-dimensional coordinate and the relation between the computer picture two-dimensional coordinate system.These parameters need be determined through the demarcation of CCD camera.

If measurement coordinate system o _sx _sy _sz _sWith CCD camera coordinate system o _cx _cy _cz _cUnanimity, with the k optical plane at o _cx _cy _cz _cPlane equation under the coordinate system and CCD camera perspective transform formula combine, and can draw noodles line structural light measurement formula:

$x_s=\frac{d_k{X}_u}{a_k{X}_u+b_k{Y}_u+{\mathrm{fc}}_k}$

$y_s=\frac{d_k{Y}_u}{a_k{X}_u+b_k{Y}_u+{\mathrm{fc}}_k}$

$z_s=\frac{{\mathrm{fd}}_k}{a_k{X}_u+b_k{Y}_u+{\mathrm{fc}}_k}$

X _u＝X _d(1+k ₁r ²)

Y _u＝Y _d(1+k ₁r ²)

X _d＝s _xd _x(u-u ₀)

Y _d＝d _y(v-v ₀)

A in the formula _k, b _k, c _k, d _kBe the structural parameters of sensor, k=1,2,3, Λ, n.

From above-mentioned discussion as can be known, need only the perspective corresponding relation between prior known each optical plane and the picture plane, can determine the parameter (a of each optical plane _k, b _k, c _k, d _k), thereby can try to achieve on each optical plane each point at measurement coordinate system o by noodles line structural light measurement formula _sx _sy _sz _sUnder three-dimensional coordinate (x _s, y _s, z _s).And then simulate the surface of measured workpiece.

Finish after the match on measured workpiece surface, become angle α with work top by measurement and positioning reference point and CCD camera optical axis _cFinish fitting surface from measurement coordinate system o _sx _sy _sz _sTo work top coordinate system o _px _py _pz _pCoordinate transform.And according to o _px _py _pz _pFitting surface under the coordinate system is formulated the swash width of laser scanning head.

Good effect of the present invention is: can formulate the swash width of laser scan type three-dimensional measurement lathe laser scanning head in measuring process automatically, the swash width of manually formulating laser scanning head by the operator according to the putting position and the resemblance of workpiece before need not at every turn measuring.Can finish the surveying work of the workpiece that needs repeated measurement easily, its operating rate is fast, has reduced operator's working strength and has improved work efficiency.

Description of drawings:

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the workpiece putting position coordinate figure in the embodiments of the invention;

Fig. 3 needs the regional coordinate figure that covers in the laser scanning head scanning process of the present invention;

Fig. 4 is the swash width coordinate figure of formulation of the present invention

Fig. 5 is an initialize routine process flow diagram of the present invention;

Fig. 6 is that laser scanning head stroke of the present invention is formulated program flow diagram.

Embodiment:

The present invention will be further described below in conjunction with embodiment:

Embodiment 1:

One, after the selected reference point, with support, the noodles line projector and CCD camera install, and at first carry out the initial work of system, and it may further comprise the steps:

Location reference point is fixed on work top coordinate system o _px _py _pz _pInitial point, i.e. the center of work top, it is at work top coordinate system o _px _py _pz _pCoordinate be (0,0);

The system initialization sample is placed on the work top, and measures it at work top coordinate system o _px _py _pz _pUnder putting position, the centre coordinate of system initialization sample is (0,0);

Open the noodles line projector, the noodles line is projected on the system initialization sample, start the noodles line projection image that the CCD camera obtains the system initialization sample, the image that the CCD camera obtains is read in computing machine by image pick-up card.

With position reference point coordinate (0,0), the centre coordinate (0,0) of system initialization sample putting position, CCD stylus optical axis becomes angle α with work top _c=45 °, noodles line projector optical axis becomes angle α with work top _p=45 ° of input computing machines.

The start-up system initialize routine is h=2m at support height, and horizontal range is l=1.3m between the CCD stylus and the noodles line projector, and CCD stylus effective focal length is f=7.8mm, and CCD photosensitive unit level interval is d _x=15.33 * 10 ^-3Mm, CCD photosensitive unit vertical interval is d _x=15.33 * 10 ^-3Mm, CCD photosensitive unit level interval scale factor is s _x=1.215, the effective imaging scope of CCD stylus is ± 45 °, and effectively projection scope of the noodles line projector is ± 30 °, and optical plane projection number is under 150 the situation, sensor construction parameter matrix A _sFor:

K=1 wherein, 2,3......150;

Transformation matrix of coordinates A _tFor:

$A_t=\left[\begin{array}{ccc}0.707& 0& -0.955\\ 0.707& 1& 0\\ 0& 0& 1.874\end{array}\right]$

System deviation compensation matrix A _bFor:

$\left[x^{\&prime;}\right]=\left[\begin{array}{cccccc}1& x& y& x^2& \mathrm{xy}& y^2\end{array}\right]\&CenterDot;\left[\begin{array}{c}0.067\\ 1.037\\ 0.016\\ -0.013\\ -0.007\\ 0.021\end{array}\right]$

$\left[y^{\&prime;}\right]=\left[\begin{array}{cccccc}1& x& y& x^2& \mathrm{xy}& y^2\end{array}\right]\&CenterDot;\left[\begin{array}{c}0.049\\ 0.978\\ 0.021\\ 0.015\\ 0.009\\ -0.017\end{array}\right]$

Two, finish after the system initialization, workpiece is carried out formal measurement; Step is as follows:

(1), the workpiece of shape tested 700mm * 350mm * 120mm as shown in Figure 2 is placed on the work top, open the noodles line projector, the noodles line is projected on the measured workpiece, start the noodles line projection image that the CCD camera obtains measured workpiece;

(2), by image pick-up card the image that the CCD camera obtains is read in computing machine; As shown in Figure 3: start the laser scanning head swash width and formulate program, according to the sensor construction parameter matrix A that in initialization procedure, obtains _sSimulate the curved surface that obtains measured workpiece, and application system deviation compensation matrix A _bFitting surface is carried out deviation compensation, use transformation matrix of coordinates A again _tWith the match song by CCD camera coordinate system o _cx _cy _cz _cBe transformed into work top coordinate system o _px _py _pz _pObtain measured workpiece at o _px _py _pz _pTo the projection of work top, promptly need the zone that covers in the laser scanning head scanning process under the coordinate system,

(3) according to measured workpiece interpolation operation is carried out in the projection of work top, determine the optimum level face two-dimensional scan stroke of laser scanning head, and according to the swash width of appointment the fitting surface of measured workpiece is carried out vertical section and handle, obtain the vertical height value of laser scanning head in stroke.Adopting the single sweep operation live width is that the swash width of being formulated as shown in Figure 5 under the situation of laser scanning head of 300mm

(4), converting both codes to according to the requirement of digital control system send digital control system to finish scanning to measured workpiece.

Claims (3)

1, a kind of laser scanning head stroke that is used for the three-dimensional measurement lathe is formulated system automatically, by location reference point, and system initialization sample, support, the noodles line projector, the CCD camera, image pick-up card, industrial PC and post-processed program are formed; It is characterized in that: workflow is as follows:

One, work as location reference point, support after the noodles line projector and CCD camera install, at first carries out the initial work of system, and initialization may further comprise the steps:

(1), accurate measurement and positioning reference point is at work top coordinate system o _px _py _pz _pUnder fixed position coordinate (x _r, y _r);

(2), the system initialization sample is placed on the work top, and accurately measure it at work top coordinate system o _px _py _pz _pUnder putting position coordinate (x _s, y _s);

(3), open the noodles line projector, the noodles line is projected on the system initialization sample;

(4), start the noodles line projection image that the CCD camera obtains the system initialization sample;

(5), by image pick-up card the image that the CCD camera obtains is read in computing machine;

(6), with (x _r, y _r), (x _s, y _s), CCD camera optical axis becomes angle α with work top _c, noodles line projector optical axis becomes angle α with work top _pThe input computing machine;

(7), the start-up system initialize routine, and according to above-mentioned input quantity calculating sensor structural parameters matrix A _s, system deviation compensation matrix A _b, transformation matrix of coordinates A _t

Two, finish after the system initialization, workpiece is carried out formal measurement; Step is as follows:

(1), measured workpiece is placed on the work top, open the noodles line projector, the noodles line is projected on the measured workpiece;

(2), start the noodles line projection image that the CCD camera obtains measured workpiece;

(3), by image pick-up card the image that the CCD camera obtains is read in computing machine;

(4), start the laser scanning head swash width and formulate program, formulate the optimum scanning stroke of laser scanning head automatically, and the control laser scanning head moves.

2, a kind of laser scanning head stroke that is used to measure lathe according to claim 1 is formulated system automatically, it is characterized in that the main flow process of described system initialization routine is as follows:

(1) becomes angle α with work top according to CCD camera optical axis _c, noodles line projector optical axis becomes angle α with work top _pCalculating sensor structural parameters matrix A _s

(2) ccd image is handled, obtained on the striations frame of each point and deposit body coordinate (x _d, y _d);

(3) with sensor construction parameter matrix A _sDeposit body coordinate (x with the frame of each point on the striations _d, y _d) substitution noodles line structural light measurement formula, obtain on the striations each point at measurement coordinate system o _sx _sy _sz _sUnder three-dimensional coordinate (x _s, y _s, z _s);

(4) three-dimensional coordinate according to each point on the striations carries out match to the surface of system initialization sample, obtains fitting surface S _s' (u, v);

(5) deposit the surface fitting curved surface S of system for computer initialization sample more in advance in _s(u is v) with S _s' (u v), calculates system deviation compensation matrix A _b

(6) according to reference location point (x _r, y _r) and α _cCalculating is by CCD camera coordinate system o _cx _cy _cz _cTo work top coordinate system o _px _py _pz _pTransformation matrix of coordinates A _t', and according to the actual putting position (x of system initialization sample _s, y _s) to A _t' revise, obtain revised transformation matrix of coordinates A _t

(7) with A _b, A _s, A _tDeposit computing machine in; Sensor construction parameter matrix A _s, system deviation compensation matrix A _b, transformation matrix of coordinates A _tIn case after determining, do not change as each parts relative position of native system, then A _b, A _s, A _tDo not change.

3, a kind of laser scanning head stroke that is used to measure lathe according to claim 1 is formulated system automatically, and it is as follows to it is characterized in that described laser scanning head swash width is formulated the main flow process of program:

(1) ccd image is handled, obtained on the striations frame of each point and deposit body coordinate (x _d, y _d);

(2) with sensor construction parameter matrix A _sDeposit body coordinate (x with the frame of each point on the striations _d, y _d) substitution noodles line structural light measurement formula, obtain on the striations each point at measurement coordinate system o _sx _sy _sz _sUnder three-dimensional coordinate (x _s, y _s, z _s);

(3) three-dimensional coordinate according to each point on the striations carries out match to the surface of system initialization sample, obtains fitting surface S _t ^{S '}(u, v);

(4) application system deviation compensation matrix A _bTo fitting surface S _t ^{S '}(u v) carries out deviation compensation, obtains S _t ^s(u, v);

(5) use transformation matrix of coordinates A _tWith S _t ^s(u is v) by CCD camera coordinate system o _cx _cy _cz _cBe transformed into work top coordinate system o _px _py _pz _p, get S _t ^p(u, v);

(6) ask o _px _py _pz _pFitting surface S under the coordinate system _t ^p(u v) to the projection of work top, gets the C of drop shadow curve _tAnd C (u), _t(u) carry out interpolation operation, determine the optimum level face two-dimensional scan stroke of laser scanning head;

(7) to fitting surface S _t ^p(u v) carries out vertical section and handles, and obtains the vertical height value in the laser scanning head stroke;

(8) stroke with laser scanning head is converted to the discernible both codes of numerical control system system, and carries out communication with the digital control system of measuring lathe, will be that code send digital control system;

Images