JPS635407A - Curved line interpolating system in numerical controller - Google Patents

Abstract

PURPOSE:To make divided measuring by a digitizer unnecessary and NC work a smooth curved surface in a short time by extracting continuous points successively out of measuring point group data measured by a digitizer and making curved line interpolation operating each of them. CONSTITUTION:Various data and commands are inputted to a curved line interpolating condition setting section 2 from the inputting device 1 of an NC unit, and division accuracy for obtaining division points dividing two measuring points by specified division number. Various data of a model measured by a digitizer are stored in an NC data memory 4. Continuous points of data between curved line interpolating point string extracted from the memory 4 are added to a freecurved line generating section 6. Further, division accuracy from a curved line interpolation setting data memory 3 is added to a curved line interpolation operation processing section 7, and curved line interpolation is made by processing continuous point string group from the generating section 6 according to prescribed division accuracy. Thus, divided measuring by a digitizer is made unnecessary, and NC working is executed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a curve interpolation method in a numerical control (NG) device, and in particular to a method for applying a three-dimensional free-form surface shape (hereinafter referred to as a "three-dimensional curved surface shape" to a vehicle). This invention relates to a curve interpolation method for digitized data on a curved surface of a model.

(Technical background of the invention and its problems) Conventionally, when processing using an NC device, after measuring the model shape with a digitizer, a "contour control" method is applied based on the measured point cloud data. NG processed data is created using this method. In this "contour control" method, it is possible to perform NG machining along the commanded line simply by providing measurement point data, in other words, the tool can be moved along an inclined line segment or circular arc between the measurement points. Functions such as "linear interpolation" or "circular interpolation" are used.

However, the model with the general three-dimensional curved shape is NG.
When machining, NC machining data has traditionally been created using the above-mentioned "degree linear interpolation" function, so NC machining is performed along the line segment interpolated between the measurement points, and the machined surface is This results in multiple planes divided by multiple line segments, which poses the problem of not being able to process smooth curved surfaces like model shapes.

Figure 4 (A) and (B) are diagrams showing an example of the above-mentioned "degree linear interpolation" function that has been conventionally used when NC machining a model having a general three-dimensional curved surface shape as described above. The figure (A) shows an example in which the intervals in measurement 4 are widened, that is, the digitized data is small and the measurements are rough, and the figure (B) shows an example in which the intervals between the measurement points are made finer.
In other words, an example is shown in which there is a lot of digitized data and the measurements are detailed.

As shown in FIG. 4(A), measurement points 01. D2. D3,04°D5. When creating NC machining data based on..., the above measurement point D
1. D2. D3. D4. D5. . . . are interpolated by inclined line segments (solid line portions in the figure), so when NC machining is performed based on the NC machining data, so-called "intrusion" Wl, W2, W2, . This will result in a large amount of W3 and "uncut" W4.Therefore, limit values are set in advance for areas where the above-mentioned "cutting in" Wl and W2J3 are likely to occur, to prevent machining beyond a predetermined amount. It is necessary to prevent "biting" from occurring, which poses a problem of not only the machining accuracy but also the number of man-hours required for finishing machining of the part concerned.

Therefore, as shown in FIG. 4(B), one cross-section MO of the above model shape was divided into smaller parts and measured, and the measurement point 01
1-D25. ...If the intervals are interpolated with inclined line segments, the machining accuracy will be greatly improved and it will be possible to machine curved surfaces that approximate the model shape, but in this case, the number of measurement points, that is, the digitized data, will increase, and the number of digitized data will increase. There is a problem in that the processing is laborious and takes a lot of time because the measurement is performed each time.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to divide a model having a general three-dimensional curved shape into fine pieces using a digitizer when performing NC processing. 6 (Summary of the Invention) The present invention relates to a curve interpolation method for an NC user that can reproduce a smooth curved surface that approximates a model shape based on measured measurement point cloud data without measurement (Summary of the Invention) Regarding the curve interpolation method, after measuring a model having a three-dimensional free-form surface shape using a digitizer, four consecutive points are sequentially extracted from among the four measuring points, and the first... a first free curve passing through the second and third measurement points; A second free curve that passes through the third and fourth measurement points is generated, and the first free curve and the second free curve are mixed between the second and third measurement points. , X, Y, and Z interpolation data are calculated and created between the second and third measurement points according to preset division accuracy between the measurement points.

(Embodiment of the invention) In the curve interpolation method of the present invention, a group of discrete measurement points measured by a digitizer is approximated to a smooth curve by using a mixture of free curves such as a quadratic Bezier curve. Curve interpolation is applied to the measurement points so that That is, the above-mentioned curve interpolation is realized by calculating and obtaining data for each division point divided with a predetermined division accuracy in a mixture curve of quadratic Bezier curves obtained by interpolating the measurement point group.

FIG. 1 is a block configuration diagram showing an outline of the NG device that realizes the method of the present invention. 1 is a human-powered device consisting of a keyboard etc. for manually inputting various data and commands, and 2 is a human-powered device between two measurement points to be interpolated. 3 is a curve interpolation condition setting section that defines the division accuracy for obtaining each division point obtained by dividing the two measurement points by a predetermined number of divisions in order to obtain division data; 3 is the curve interpolation condition setting section 2; This is a curve interpolation setting data memory that stores the set division accuracy and the like. Here, the division accuracy and the like set by the curve interpolation condition setting section 2 are also displayed on the CRT display screen 9 for visual confirmation. On the other hand, 4 is an NC data memory that stores various measurement data (digitized data, etc.) of the model measured by a digitizer (not shown), and 5 is among the measurement data stored in the NC data memory 4. , is a curve interpolation point sequence data memory that extracts and stores only the measurement point sequence data, and 6 is a curve interpolation point sequence data memory that extracts and stores only the measurement point sequence data. Out of the four measurement points, adjacent three points (first, second and third points, and second...
This is a free curve generation unit that generates two free curves based on the third and fourth points). 7 is the intermediate point between four consecutive points (first, second, third, and fourth points) where two free curves generated by the free curve generator 6 exist, as will be described later. At the two points (second and third points), the free curves of the two trees are mixed according to the division accuracy stored in the curve interpolation setting data memory 3, and the interpolated data of X, Y, and Z is calculated. A curve interpolation calculation processing unit 8 calculates X, Y, and Z by taking into account the X, Y, and Z interpolation data calculated by the curve interpolation calculation processing unit 7, the origin offset value, the tool offset value, etc. X, which generates each axis control command value;
This is a Y, Z function generation section. Also, 10 is the above X, Y, Z
This is an X, Y, and Z control axis drive section that drives the X, Y, and Z control axes 11 to execute predetermined NC machining according to the X, Y, and Z axis control command values generated by the function generation section 8. .

In the NG device having the above configuration, a method for calculating the X, Y, and Z interpolated data in the curve interpolation calculation IA embedding section 7 will be described below.

Figure 3 (A) shows a group of measurement points (
Pl) PI of 4 consecutive points among (i-1, N).

7+1. Pl and 2. This is a diagram showing an example of PI+3. First, among the four points P1, P1◆I+PI, 2, p, and 3, the first three points p,, p, and l*Pl*2, and the last three
Point P t+1 +P 142. A first quadratic Bazier curve Rt(u), which approximates P
Find the ier curve n+, +(v>).

Here, the first quadratic Bezier curve R1 (
u) is R, (0)・Pi, Rt(0,5)−P+++, Rt
(1) · P
゜+(0,5)-P+ or 2゜R+++(1)=h.

shall be.

Such a first quadratic Bezier curve R1(u)
and the second quadratic Bezier curve n+, +(v), the points where the same curves overlap are Pl++, P1*
2, a mixed curve C as expressed by the following formula
(t) can be obtained (solid line shown).

C(t)=(1-t) 4+ (u)+t・Rt,+
(v) +++++ (1) Here, t becomes a divided numerical value between 0 and 1 depending on the number of divisions depending on the division accuracy, and the above-mentioned mixed curve C (
t) is C(0) pass + (0,5)-Rt or +(0)-h
□C(1)-R11l)-Rt, + (o, 5)-p+
or.

becomes. Therefore, assuming that t, u, and v are linear, the following equation holds true.

On the other hand, since the first quadratic Bezier curve R+(u) and the second quadratic Bezier curve R1l (V) are each quadratic Bezier curves, they can be expressed as follows using the control point Q1. be able to.

R1(u)-(t-u)'-oA+2(t-u) ・u
-Qi+u"Q4R+++(ν)-(1-V)2・QA
”+2(1-v)-v-Qiol,v2.q4+1
, , , , , (3) Therefore, the above (
1) , (2) , (From Equation 31, it can be expressed as the following equation using the above-mentioned mixed curve C (0 is the control point q).

C(t) −(1−t) ・Ri (u)+t−Ri,
I (V)・(1-t) ((lu-u)2・QA◆
2(1-u)・u-Qi・u'・Q4 1" (
(l-v) 2・Qo”2 (1-v) ・v-Qio
l + v 2 , q li゛l ] - the above (
3) In the formula, the quadratic Bezier curve 11 of the above %l
1(u) is Ri (0)-QA-P+, Ri fl)・QA・P
l or.

R1 and +(o)-QA”・Pl.

nt. The relationship is qE-(4・P1++-PI-P++2)q!"-(4
・P1+2-P1*BiPt-*) PI◆1+3 in P1 -pt◆2" P++2-□ ......(5) is found.

Therefore, from the above equations (4) and (5), the above-mentioned mixed curve C(t) can be expressed as the following equation.

Here, the first-order differential coefficient of this (combined curve C) is continuous at its internal points. Therefore, the above (
The following equation can be found from equations 1) and (2).

C(t) −R+ (ul + ft+ −+ (v
)-J (u)) Here, for 1-0, v-0,u
Since −0,5, R, and I ((1) −Rt +
0.5)・P. 1, and at t-1 v=0.5.
Since it is u-1, mouth+-+(0,5)-11,(1)
"h42. Therefore, the above four measurement points P+, P, *1.P1+2.P1
*Point P1゜1 out of 3. It is possible to continuously perform curve interpolation up to the first-order differential coefficient between P++2. Then, such curve interpolation is performed for the following four measurement points P, 2+PL"3+Pi+4, and the point Pi*2*P
By repeating the operation of interpolating curves 1 and ,
Finish curve interpolation for all measurement points.

The above-described curve interpolation operation will be explained in detail below using the flowchart shown in FIG.

First, when the precision of curve interpolation (number of divisions, etc.) to be obtained is input by operating the human-powered device 1, the division precision set by the curve interpolation condition setting section 2 is stored in the curve interpolation setting data memory 3. (Step Sl). - On the other hand, among the measurement point group data stored in the NC data memory 4,
As shown in FIG. 3(A), first, four consecutive points P1 to be interpolated. P1*1. PH and 2. Pl. point sequence data is extracted and stored in the curve interpolation point sequence data memory 5 (step 52). Therefore, the free curve generation section 6 uses the quadratic BeZier curve as described above,
The above four points p,, p, and 1. P, the first three points of 2+Pl+3 P1. jl+1, the first free curve passing through P1+2, and the last three points p, □, PI+2. In step S3), the curve interpolation calculation processing section 7 generates a second free curve passing through PI+3.
Using a mixture of er curves, the middle 2 of the above 4 points
Point P1+1. P.L. 2, the free curves of the two trees that pass through P are combined, and the two points P are obtained according to the division precision set in the curve interpolation data memory 3. ,.

X, Y, Z interpolation data between PI+12 is calculated (step 54). Then, the X, Y, Z function generating section 8 calculates the control command values for each of the X, Y, and Z axes by adding the origin offset value, tool offset value, etc. to the X, Y, and Z interpolation data (step S5). , the above X, Y, 2 control axis drive unit l
The X, Y, and Z control axes 11 are driven via O (step 56). If the measurement points to be interpolated remain (step S7), the process returns to step S2 and the next four consecutive measurement points (in this case, point P1°1.7+2.P
I. 3. Pi+4) is extracted and subjected to interpolation processing, and the steps 52 to S7 described above are further repeated to perform curve interpolation on all measurement points measured by the digitizer, and the process ends.

FIG. 5 is a diagram showing an example of a trajectory obtained by curve interpolation of all measurement points DDI-DDIO (an example of the coordinate values are shown in the figure) measured by the digitizer in this way, and as described above. , first measurement point 001. DD2. The first free curve B1 (-80) obtained from DD3 and the measurement point DD2,
The second free curve B2 (-
C1) and measurement point D112.

Between DD3, a trajectory 80 shown by a solid line in the figure is generated. Next, the second free curve C1 (-82) and the third free curve C2 obtained from the measurement points DD3, DD4, and DD5 are mixed, and the measurement point DD3. Between DD4,
A trajectory GO shown by a solid line in the figure is generated. Then, by repeating these operations between all measurement points, it becomes possible to interpolate curves between all measurement points using the trajectory shown by the solid line in the figure, as shown in Figure 5. .

(Effects of the Invention) As described above, according to the method of the present invention, when performing NG processing on a model having a general three-dimensional curved surface shape, the digitizer
By sequentially extracting four consecutive points from the measurement point cloud data measured by the digitizer, calculating each point, and interpolating the curve, it is possible to create a model shape with the same simple operations as before, without having to divide it into smaller pieces with a digitizer and measure it. Approximately smooth curved surfaces can be reproduced in a short time by NG processing.

FIG. 2 is a block diagram showing the outline of the embodiment, FIG. 2 is a flowchart for explaining an example of the operation of the system of the present invention, and FIG.
), (B) and FIG. 5 are diagrams for explaining the method of the present invention, and FIGS. 4 (A) and (B) are diagrams for explaining an example of the conventional interpolation method.

l...input device, 2...curve interpolation condition setting section, 3.
...Curve interpolation setting data memory, 4...NC data memory, 5...Curve interpolation point sequence data memory, 6...Free curve generation section, 7.Curve interpolation calculation processing section, 8.
, Yj function generator, 9 ・<RT, 10-X, Y,
Z control axis drive unit, 11...X, Y, Z control axes.

Applicant's agent: Yuzo Angata Hanging diagram 2 Hanging diagram 3 stomach 4 N=- and 15 Figure 4

Claims (1)

[Claims] After measuring a model having a three-dimensional free-form surface shape using a digitizer, four consecutive points are sequentially extracted from among the four measurement points, and the first, second, and third measurement points are extracted from among the four measurement points. and a second free curve passing through the second, third and fourth measurement points, and generating the first free curve between the second and third measurement points. and the second free curve, and interpolated X, Y, and Z data between the second and third measurement points according to the preset division accuracy between the measurement points. A curve interpolation method for a numerical control device, characterized in that the curve is created by calculation.