CN101561250B - Method for intelligent position finding and online measurement of large-dimension cam non-circular grinding - Google Patents

Abstract

The invention relates to a method for intelligent position finding and online measurement of non-circular cam grinding large-dimension. The method utilizes visual sensing technology to acquire an image of a laser ray on the cam within each sampling period through a computer-controlled image acquisition system, calculates coordinates of points on a corresponding cam profile after pretreatment, can obtain the coordinates of a plurality of points on the cam profile on the current assembly position after the cam is rotated for a circle, and obtain an actual cam profile curve. The method can obtainoptimum cam processing zero position and accurate cam profile error through treatment by 'a sensitive point method' according to the principle of 'minimum condition'. The method avoids high requireme nt of a radial displacement sensor on the range, ensures that a measuring device has a simple structure, is convenient for the intelligent position finding and online measurement of cam non-circular grinding, and improves the processing efficiency and the processing precision of cam non-circular grinding.

Description

Large-dimension cam non-circular grinding intelligent locating and On-line Measuring Method

Technical field

The present invention relates to a kind of intelligent locating and On-line Measuring Method of cam non-circular grinding.

Background technology

So-called non-circular grinding is the synchronous grinding technique of C-X, is developed country's a kind of tracking grinding technique newly developed in recent years, and it adopts the grinding machine headstock is that the C axle drives Workpiece Rotating, and the grinder wheel frame is X-axis a kind of technology that instruction is carried out grinding with motion tracking according to the headstock.The cam non-circular grinding process as shown in Figure 1.Its motion model is an initial angle with design zero point of cam, yet the reference position of clamping is at random arbitrarily during grinding, but also there are problems such as blank allowance is inhomogeneous, be not the theoretical zero point of design the actual zero point when these can cause grinding, thereby cause the dimensional accuracy of cam workpiece overproof, even scrap.In traditional cam ground processing, particularly in single-piece, small batch production process, the small change of cam point is manual carrying out, and the precision of small change point and efficient depend on operator's technical merit fully.Therefore, the process of finding cam zero point accurately has consumed the plenty of time, and the error at processing zero point of at every turn finding and design zero point can't guarantee, greatly reduces the overall efficiency of cam non-circular grinding.On the other hand, adopt the dedicated cam measuring instrument substantially for the detection of THE CAM PROFILE ERROR at present.This special measurement instrument detects as the machining error of final products usually, and its range is very little, and the semi-manufacture in being in process, its error and surfaceness may be bigger, are not suitable for using this special high-accuracy measuring instrument to detect.And off-line measurement makes cam design benchmark, machining benchmark, measuring basis irrelevant mutually, and this crudy for final assurance cam is unfavorable.The applicant once proposed in early-stage Study by auxiliary bodies such as displacement transducer and rotary cylinders according to cam non-circular grinding motion model control survey process, measuring head is contacted with workpiece all the time, the method of carrying out online cam contour location and measuring, but experiment shows: this method location and accuracy of detection can not reach requirement in advance, and there is measuring head shortcoming easy to wear in the contact type measurement scheme.Therefore, how to realize that quick small change and profile in the cam non-circular grinding are detected as to limiting the bottleneck problem of cam non-circular grinding efficient and crudy.

Summary of the invention

The objective of the invention is to defective, a kind of cam non-circular grinding intelligent locating and On-line Measuring Method are provided, realize intelligent locating and on-line measurement, reduce human intervention degree and working strength, improve its working (machining) efficiency and machining precision at the prior art existence.

For achieving the above object, design of the present invention is: mainly be made up of CCD camera, laser line light source and data handling machine based on automatic location of machine vision large-dimension cam sheet non-circular grinding and on-line detecting system.Digital control system control cam blank obtains two straight lines according to the end face of the speed rotation of appointment, optical plane that laser line light source sends and plane cam and working surface are crossing, article two, the intersection point of straight line is the point on the plane cam profile, and this puts the radius vector of the distance of the centre of gyration for this point.Carry out the intelligent locating and the online detection of large-dimension cam sheet non-circular grinding by such method.Human intervention degree when this method has not only reduced small change, working strength, and overcome traditional measurement method need guarantee the gauge head geomery must be consistent with cam follower wheel and range less can't measure large scale change cam, there are drawbacks such as measuring head is easy to wear in the contact type measurement scheme; Have that physical construction is simple, volume is little, applicability is strong, need not change the characteristics of gauge head when measuring.

The computer control image capturing system is gathered the image of laser rays on the cam in each sampling period, through after the pre-service, calculate the coordinate of putting on the corresponding cam contour.After cam revolves and turns around, just can obtain the coordinate of some points on cam contour under the current installation site, and then obtain actual cam profile curve.For the automatic location of cam, need to go out the angle that the cam blank need turn over according to the algorithm computation of positioning principle.Online detection for cam contour, the workpiece profile that grinding is finished carries out on-line measurement, the initial phase of cam is known, only need the evaluation model of the data of the design cam contour of preserving in actual cam profile curve that records and the computing machine by the minimal condition criterion compared, just can obtain the error of actual cam contour.

According to the foregoing invention design, the present invention adopts following technical proposals:

A kind of cam non-circular grinding is location and On-line Measuring Method automatically, it is characterized in that operation steps is:

1) according to detection principle of computer vision design detection system hardware platform scheme, determines concrete hardware composition and mount scheme.

2) the computer control image capturing system is gathered the image of laser rays on the cam in each sampling period.

3) carrying out image segmentation under the different threshold values and carry out image smoothing under different convolution mask, comparing result is selected best design sketch.

4) coordinate figure of putting on the profile is found the solution.The cam edge point is corresponding to the intersection point of image upper surface and side striation.Need only the striation straight line that fits out cam face and side with the pixel after the extraction of striation center respectively, obtain the intersection point of two straight lines again, be the corresponding point of cam face point on image.

5) cam centre of gyration coordinate is demarcated.The installation site of fixed cameras, guarantee that the optical plane that laser instrument sends passes through under the prerequisite of the cam centre of gyration, adjust the irradiating angle of laser instrument, corresponding each irradiating angle, use the camera acquisition piece image, can obtain one group of images acquired like this, the crossing striation that forms of laser plane and cam face all passes through a common point in this group images acquired, and this common point is exactly the cam centre of gyration.

6) radius vector of point is found the solution.Vision system, just can be obtained the point and the centre of gyration coordinate at workpiece coordinate system, and then be obtained the radius vector of point with the coordinate conversion in the image coordinate system to workpiece coordinate system by the vision system of having demarcated through demarcating.

7) obtain actual cam profile curve by curve fitting,, determine the processing zero-bit of cam, realize the on-line automatic location of cam according to the positioning principle of cam in conjunction with the cam pitch curve curve.

8) according to the on-line automatic location process of cam, the workpiece that grinding is finished carries out online measurement, adopts sensitivity points method, follows the minimal condition principle data that measure are handled, and can realize online detection to cam contour.

Wherein, above-mentioned steps 4) coordinate of point is found the solution in, adopts least square method to find the solution coordinate figure.Coordinate sequence (the x of the pixel that obtains after the striation center extracted _i, y _i) (i=0,1. ..., m) can get with straight line y=kx+b match:

Xc＝Y (1)

$X=\left[\begin{array}{cc}{x}_0& 1\\ x_1& 1\\ \·\·\·& \·\·\·\\ x_m& 1\end{array}\right]$ $c=\left[\begin{array}{c}k\\ b\end{array}\right]$ $Y=\left[\begin{array}{c}{y}_0\\ y_1\\ \·\·\·\\ y_m\end{array}\right]---\left(2\right)$

Can solve:

c＝(X ^TX) ^-1X ^TY (3)

Wherein, each pixel horizontal ordinate structural matrix X, ordinate structural matrix Y, X ^TIt is the transposition of X.

Thereby determine the slope k of match striation straight line and cut the b that crouches.Simulate two straight lines by cam diagram as upper surface and side striation respectively, the intersection point of two straight lines is the coordinate figure of point.

Above-mentioned steps 5) cam centre of gyration coordinate is demarcated and can be finished as follows:

A) utilize least square method to extract one group of striation straight line of the different irradiating angles of corresponding laser instrument, obtain one group of straight-line equation:

$\left.\begin{array}{c}{y}_1=k_1{x}_1+b_1\\ y_2=k_2{x}_2+b_2\\ \·\·\·\·\·\·\\ y_n=k_n{x}_n+b_n\end{array}\right\}---\left(4\right)$

Formula (4) cathetus equation is represented laser instrument the 1st, 2,3 respectively ... the striation straight-line equation of n irradiating angle, y _n=k _nx _x+ b _nBe the striation straight-line equation that obtains corresponding to n irradiating angle of laser instrument.Wherein, k _nAnd b _nThe slope that is the striation straight-line equation of n irradiating angle is crouched with cutting.

B) utilize n the striation straight-line equation of obtaining in the formula (4), ask friendship in twos, can obtain n (n-1)/2 intersection point, the coordinate (x of these intersection points _Ij, y _Ij) can be expressed as:

$\left.\begin{array}{c}{x}_{\mathrm{ij}}=-\frac{b_i-b_j}{k_i-k_j}\\ y_{\mathrm{ij}}=\frac{b_i{k}_i-b_j{k}_j}{k_i-k_j}\end{array}\right\}i,j=\mathrm{1,2},...,n(n-1)/2---\left(5\right)$

In the formula, x _Ij, y _IjBe respectively the horizontal ordinate and the ordinate of i bar striation straight line and j bar striation straight-line intersection; k _i, b _iBe respectively the slope and the intercept of i bar striation straight line; k _j, b _jBe respectively the slope and the intercept of j bar striation straight line.

C) calculate horizontal ordinate x respectively _IjArithmetic mean x ₀With ordinate y _IjArithmetic mean y ₀, promptly obtain the coordinate of the cam centre of gyration:

$\left.\begin{array}{c}\stackrel{\‾}{x_0}=\frac{\underset{\mathrm{ij}=0}{\overset{n(n-1)/2}{\mathrm{\Σ}}}{x}_{\mathrm{ij}}}{n(n-1)/2}\\ \stackrel{\‾}{y_0}=\frac{\underset{\mathrm{ij}=0}{\overset{n(n-1)/2}{\mathrm{\Σ}}}{y}_{\mathrm{ij}}}{n(n-1)/2}\end{array}\right\}---\left(6\right)$

By the coordinate of the known cam contour point of the step of front and the centre of gyration, above-mentioned steps 6) radius vector of cam point finds the solution and can calculate the profile each point by formula (7) and obtain to the distance of the centre of gyration.

$d_i=\sqrt{{(x_{\mathrm{di}}-\stackrel{\‾}{x_0})}^2+{(y_{\mathrm{di}}-\stackrel{\‾}{y_0})}^2}---\left(7\right)$

Wherein, d _iBe the radius vector at place, i sampling angle on the cam, (x _Di, y _Di) coordinate of i sampled point on the cam contour, (x ₀, y ₀) coordinate of the cam centre of gyration.

The used measurement mechanism of the present invention as shown in Figure 2, comprises CCD camera, semiconductor laser, image pick-up card and a computing machine.It is characterized in that:

Video camera and laser instrument from the cam front around y _pAngle θ of axle rotation, three's relative position as shown in Figure 2.Laser is radiated on the end face and side of cam simultaneously, and optical plane forms striation, the image of camera acquisition cam face and side by the centre of gyration of cam on the intersection of optical plane and cam face and side.

The present invention compared with prior art, have following conspicuous outstanding substantive distinguishing features and remarkable advantage: the present invention has remedied the shortcoming of radial displacement transducer range deficiency with the vision sensor technology, in each sampling period, gather the image of laser rays on the cam by the computer control image capturing system, obtain the point radius vector through handling to calculate, following " minimal condition " principle according to " sensitivity points method " handles, promptly obtain optimum cam processing zero-bit and THE CAM PROFILE ERROR accurately, help realizing the automatic location and the online detection of cam non-circular grinding.Human intervention degree when the inventive method has not only reduced small change, working strength, and overcome traditional measurement method need guarantee the gauge head geomery must be consistent with cam follower wheel and the less large scale of can't measuring of range change cam, contact type measurement scheme and have drawbacks such as measuring head is easy to wear.

Description of drawings

Fig. 1 cam non-circular grinding synoptic diagram.

Fig. 2 is the synoptic diagram of measuring process described in the present invention.

The operational flowchart of Fig. 3 measuring method of the present invention.

Embodiment

A preferred embodiment of the present invention accompanying drawings is as follows: referring to Fig. 1, cam non-circular grinding as shown in the figure, 1 is cam, 2 is roller, 3 is emery wheel.Referring to Fig. 2, automatic location of this cam non-circular grinding and on-line measurement device comprise a ccd video camera 4, laser instrument 8, image pick-up card and computing machine, video camera 4 and laser instrument 8 from the cam front around y _pAngle θ of axle rotation, three's relative position as shown in Figure 2.Laser is radiated on the end face 6 and side 5 of cam simultaneously, and optical plane 8 forms striation by the centre of gyration of cam on the intersection of optical plane and cam face and side, and video camera 4 is gathered the image of cam face 6 and side 5.

Referring to Fig. 1 and Fig. 3, the intelligent locating and the On-line Measuring Method of this cam non-circular grinding are:

1. according to detection principle of computer vision design detection system hardware platform scheme, determine measurement mechanism mount scheme as shown in Figure 2.

2. the computer control image capturing system is gathered the image of laser rays on the cam in each sampling period.

3. carrying out image segmentation under the different threshold values and carry out image smoothing under different convolution mask, comparing result is selected best design sketch.

4. the coordinate of point is found the solution, and adopts least square method to find the solution coordinate figure.Coordinate sequence (the x of the pixel that obtains after the striation center extracted _i, y _i) (i=0,1. ..., m) can get with straight line y=kx+b match:

Xc＝Y (1)

$X=\left[\begin{array}{cc}{x}_0& 1\\ x_1& 1\\ \·\·\·& \·\·\·\\ x_m& 1\end{array}\right]$ $c=\left[\begin{array}{c}k\\ b\end{array}\right]$ $Y=\left[\begin{array}{c}{y}_0\\ y_1\\ \·\·\·\\ y_m\end{array}\right]---\left(2\right)$

Can solve:

c＝(X ^TX) ^-1X ^TY (3)

Wherein, each pixel horizontal ordinate structural matrix X, ordinate structural matrix Y, X ^TIt is the transposition of X.

Thereby determine the slope k of match striation straight line and cut the b that crouches.Simulate two straight lines by cam diagram as upper surface and side striation respectively, the intersection point of two straight lines is the coordinate figure of point.

5. cam centre of gyration coordinate is demarcated and can be finished as follows:

A) utilize least square method to extract one group of striation straight line of the different irradiating angles of corresponding laser instrument, obtain one group of straight-line equation:

$\left.\begin{array}{c}{y}_1=k_1{x}_1+b_1\\ y_2=k_2{x}_2+b_2\\ \·\·\·\·\·\·\\ y_n=k_n{x}_n+b_n\end{array}\right\}---\left(4\right)$

Formula (4) cathetus equation is represented laser instrument the 1st, 2,3 respectively ... the striation straight-line equation of n irradiating angle, y _n=k _nx _x+ b _nBe the striation straight-line equation that obtains corresponding to n irradiating angle of laser instrument.Wherein, k _nAnd b _nThe slope that is the striation straight-line equation of n irradiating angle is crouched with cutting.

B) utilize n the striation straight-line equation of obtaining in the formula (4), ask friendship in twos, can obtain n (n-1)/2 intersection point, the coordinate (x of these intersection points _Ij, y _Ij) can be expressed as:

$\left.\begin{array}{c}{x}_{\mathrm{ij}}=-\frac{b_i-b_j}{k_i-k_j}\\ y_{\mathrm{ij}}=\frac{b_i{k}_i-b_j{k}_j}{k_i-k_j}\end{array}\right\}i,j=\mathrm{1,2},...,n(n-1)/2---\left(5\right)$

In the formula, x _Ij, y _IjBe respectively the horizontal ordinate and the ordinate of i bar striation straight line and j bar striation straight-line intersection; k _i, b _iBe respectively the slope and the intercept of i bar striation straight line; k _j, b _jBe respectively the slope and the intercept of j bar striation straight line.

C) calculate horizontal ordinate x respectively _IjArithmetic mean x ₀With ordinate y _IjArithmetic mean y ₀, promptly obtain the coordinate of the cam centre of gyration:

$\left.\begin{array}{c}\stackrel{\‾}{x_0}=\frac{\underset{\mathrm{ij}=0}{\overset{n(n-1)/2}{\mathrm{\Σ}}}{x}_{\mathrm{ij}}}{n(n-1)/2}\\ \stackrel{\‾}{y_0}=\frac{\underset{\mathrm{ij}=0}{\overset{n(n-1)/2}{\mathrm{\Σ}}}{y}_{\mathrm{ij}}}{n(n-1)/2}\end{array}\right\}---\left(6\right)$

6. by the coordinate of the known cam contour point of the step of front and the centre of gyration, the radius vector of cam contour point is found the solution and can be calculated the profile each point by following formula and obtain to the distance of the centre of gyration:

$d_i=\sqrt{{(x_{\mathrm{di}}-\stackrel{\‾}{x_0})}^2+{(y_{\mathrm{di}}-\stackrel{\‾}{y_0})}^2}---\left(7\right)$

Wherein, d _iBe the radius vector at place, i sampling angle on the cam, (x _Di, y _Di) coordinate of i sampled point on the cam contour, (x ₀, y ₀) coordinate of the cam centre of gyration.

7. obtain actual cam profile curve by curve fitting,, determine the processing zero-bit of cam, realize the on-line automatic location of cam according to the positioning principle of cam in conjunction with the cam pitch curve curve.

8. according to the on-line automatic location process of cam, the workpiece that grinding is finished carries out online measurement, adopts sensitivity points method, follows the minimal condition principle data that measure are handled, and can obtain cam contour mismachining tolerance accurately.

Claims (4)

1. cam non-circular grinding intelligent locating and On-line Measuring Method is characterized in that operation steps is:

1) according to detection principle of computer vision design detection system hardware platform scheme, determines concrete hardware composition and mount scheme;

2) the computer control image capturing system is gathered the image of laser rays on the cam in each sampling period;

3) carrying out image segmentation under the different threshold values and carry out image smoothing under different convolution mask, comparing result is selected best design sketch;

4) coordinate figure of putting on the profile is found the solution: the cam edge point is corresponding to the intersection point of image upper surface and side striation, as long as fit out the striation straight line of cam face and side respectively with the pixel after the extraction of striation center, obtain the intersection point of two straight lines again, be the corresponding point of cam face point on image;

5) cam centre of gyration coordinate is demarcated: the installation site of fixed cameras, guarantee that the optical plane that laser instrument sends passes through under the prerequisite of the cam centre of gyration, adjust the irradiating angle of laser instrument, corresponding each irradiating angle, use the camera acquisition piece image, can obtain one group of images acquired like this, the crossing striation that forms of laser plane and cam face all passes through a common point in this group images acquired, and this common point is exactly the cam centre of gyration;

6) radius vector of point is found the solution: vision system is through demarcating, by the vision system of having demarcated, just can obtain the point and the centre of gyration coordinate, and then obtain the radius vector of point with the coordinate conversion in the image coordinate system to workpiece coordinate system at workpiece coordinate system;

7) obtain actual cam profile curve by curve fitting,, determine the processing zero-bit of cam, realize the on-line automatic location of cam according to the positioning principle of cam in conjunction with the cam pitch curve curve;

8) according to the on-line automatic location process of cam, the workpiece that grinding is finished carries out online measurement, adopts sensitivity points method, follows the minimal condition principle data that measure are handled, and can realize online detection to cam contour.

2. cam non-circular grinding intelligent locating according to claim 1 and On-line Measuring Method, the coordinate of its feature point in described step 4) is found the solution, and adopts least square method to find the solution coordinate figure, the coordinate sequence (x of the pixel that obtains after the striation center is extracted _i, y _i), i=0,1. ..., m can get with straight line y=kx+b match:

Xc＝Y (1)

Can solve:

c＝(X ^TX) ^-1X ^TY (3)

Wherein, each pixel horizontal ordinate structural matrix X, ordinate structural matrix Y, X ^TIt is the transposition of X;

Thereby determine the slope k and the intercept b of match striation straight line, simulate two straight lines by cam diagram as upper surface and side striation respectively, the intersection point of two straight lines is the coordinate figure of point.

3. cam non-circular grinding intelligence location according to claim 1 and On-line Measuring Method is characterized in that it is to finish as follows that described step 5) cam centre of gyration coordinate is demarcated:

A) utilize least square method to extract one group of striation straight line of the different irradiating angles of corresponding laser instrument, obtain one group of straight-line equation:

Formula (4) cathetus equation is represented laser instrument the 1st, 2,3 respectively ... the striation straight-line equation of n irradiating angle, y _n=k _nx _x+ b _nBe the striation straight-line equation that obtains corresponding to n irradiating angle of laser instrument, wherein, k _nAnd b _nBe the slope and the intercept of the striation straight-line equation of n irradiating angle;

B) utilize n the striation straight-line equation of obtaining in the formula (4), ask friendship in twos, can obtain n (n-1)/2 intersection point, the coordinate (x of these intersection points _Ij, y _Ij) can be expressed as:

In the formula, x _Ij, y _IjBe respectively the horizontal ordinate and the ordinate of i bar striation straight line and j bar striation straight-line intersection; k _i, b _iBe respectively the slope and the intercept of i bar striation straight line; k _j, b _jBe respectively the slope and the intercept of j bar striation straight line;

C) calculate horizontal ordinate x respectively _IjArithmetic mean

With ordinate y _IjArithmetic mean

Promptly obtain the coordinate of the cam centre of gyration:

。

4. it is to calculate the profile each point by following formula to obtain to the distance of the centre of gyration that cam non-circular grinding intelligent locating according to claim 3 and On-line Measuring Method, the radius vector that it is characterized in that described step 6) cam point are found the solution:

Wherein, d _iBe the radius vector at place, i sampling angle on the cam, (x _Di, y _Di) coordinate of i sampled point on the cam contour,

The coordinate of the cam centre of gyration.

Images