JPS5952304A - Preparation of teaching data for welding robot - Google Patents

Abstract

PURPOSE:To perform easily and quickly a teaching operation, by obtaining the position data on a robot from the data on the welding position as well as the function of the form of the member to be welded for a coordinate system which is set previously. CONSTITUTION:The welding gun data, tool data, form data of a member to be welded, etc. are supplied to a control part 1 consisting of graphic and display processors from a standard product file 2 and a data file 3. The form of the member to be welded is displayed to a CRT6, and the welding point data obtained by a light pen 7 is fed to the part 1. The control part 1 calculates the normal line vector of the welding point and the approach vector showing the approaching direction to the welding point of the welding gun from the data given from the file 2, the form data given from the file 3 and the welding point data. At the same time, the part 1 obtains the position data on shafts constituting the mobile parts of a welding robot in the form of a teaching data from those of above-mentioned data and then delivers this data to an output device 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for creating teaching data for a welding robot.

On car body assembly lines, we have been introducing a large number of general-purpose, quick-response welding (spot welding) robots from an early stage in order to cope with the increasing number of car models and repeated model changes due to diversifying needs.

By the way, when teaching these welding robots, it is currently necessary for the instructor to operate a teaching box and actually move the robot based on the instructor's visual judgment.

However, this teaching work has the disadvantage of being extremely man-hour-intensive and time-consuming, which has been a bottleneck in shortening lead times when changing production models or model changes.

Further, since this teaching work relies on the visual judgment of the teacher, it requires a great deal of experience and skill, and not just anyone can become a teacher.

This invention was made in view of the above-mentioned background, and its purpose is to enable teaching work to be performed in a short time and without requiring any skill, without actually moving a welding robot on site. do.

Therefore, in the teaching data creation method for a welding robot according to the present invention, a function representing the shape of the workpiece to be welded is determined in a predetermined coordinate system, and a shape model of the workpiece to be welded represented by this function is created by, for example, C
The welding point position of the workpiece is displayed on a graphic display such as an RT (cathode ray tube), and the desired position on the shape model displayed on the graphic display is specified by a conversational input means such as a light pen. After determining the welding point position, the normal vector on the workpiece to be welded at this welding point position is determined based on the function representing the shape model and the position data representing the welding point position. An approach vector indicating the approach direction of the attached welding gun to the welding point position is specified under the condition that it is orthogonal to the normal vector, and the welding is performed based on the welding point position data, normal vector, and approach vector. Teaching data for the welding robot is created by obtaining posture position data for each axis that constitutes the movable part of the robot.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a system configuration diagram of a teaching device to which the present invention is applied.

In the figure, a control section 1 is composed of a graphics processor consisting of a small computer, a graphics processor including a display processor dedicated to display processing, computers for various calculations, and the like.

In the standard product file 2, data representing various welding guns attached to the tip of a movable part of a welding robot, which will be described later, and data representing other welding robots and various jigs are written for each part.

Note that standard products are expressed in a local coordinate system (object coordinate system) unique to each part.

In the body data file 3, line and surface data representing the shape of each part of the vehicle body (panel parts, etc.) created by the vehicle body design department are written for each vehicle type and table type.

Note that these line and surface data are based on the car line coordinate system (
It is expressed in a predetermined right-handed rectangular coordinate system for cars.

In the design file 4, various calculation data such as welding point position data, normal vectors, and approach vectors determined by the control unit 1 are written.

CRT connected to control unit 1 via interface 5
Graphic display (hereinafter abbreviated as 1'-CRTJ)6. Light pen (hereinafter referred to as "LPNj") 7. Alphanumeric keyboard (hereinafter referred to as 1'-ANK J) 8. Function switch (hereinafter referred to as "FNS") 9. and variable dials (hereinafter referred to as 1'-VCDJ) 4-10 each have the following functions.

The CRT 6 is, for example, a reproducing random scanning type display, and based on commands from the control unit 1, displays a shape model of the workpiece to be welded and a shape model of the welding gun.

It displays three-dimensional shape models of various jigs and various command menus.

LPN 7 is a pen that detects light on CRT6,
Specify lines and positions in displayed figures on the screen, and specify command menus.

ANK 8 inputs numerical data and names (for example, names of coordinate axes: x, y, z, etc.).

FNS'9 inputs frequently used commands among various commands for the control unit 1.

The VCD 10 can translate or rotate the three-dimensional figure displayed on the CRT 6 for each coordinate axis (X, Y, Z axis).
Or enlarge or reduce the displayed figure.

Note that, in the following explanation, the commands to the control unit 1 are a detailed problem in the control software, and therefore the explanation will be omitted.

The teaching data output device 11 outputs the teaching data of the welding robot obtained by the control unit 1 to a paper tape,
Output to a data storage medium such as magnetic tape or magnetic disk.

The control unit 1 controls the various conversation input devices and various peripherals as described above, and mainly performs the following arithmetic processing.

(B) Interpolation calculations and various coordinate transformations (B) Calculation of welding point positions (C) Calculation of normal vectors and approach vectors)
Calculation of posture position data for each axis constituting the movable part of the welding robot The teaching device shown in FIG. 1 is configured by, for example, the "rAGs4145 Graphic System" and the "UNIvAC Series 1100" manufactured by Nippon Univac Co., Ltd.

Next, the specifications of various data to be processed in the teaching apparatus shown in FIG. 1, the contents of the calculation process, the operation of the entire apparatus, etc. will be explained in order.

First, the data representing the shape of the standard product written in the standard product file 2 is canonical data, which is a collection of data representing some basic shapes (elements).

The canonical data for each standard product is defined in a local coordinate system, but when the standard product is placed at a welding work position, it is converted to the coordinate system of the placement destination.

The panel data written in the body data file 3 is classified into curve data or curved surface data depending on the shape of the panel, and each has the following data specifications.

First, the curve data, for example in the case of curve t in FIG. 2, is as shown in Table 1.

Table 1 However, in Table 1, the total number of cells is -1 if the number of points on the curve is equal to the number of points on the curve in Figure 2, and
lTR77L11, 1TR7712+ (y7Z+
=1-n-1°m2-2~rL) is the absolute value (magnitude) of two tangent vectors at 1 point) P77Z as shown in FIG.

Note that the panel shape that can be represented by such curve data includes, for example, the curve As of the workpiece W as shown in FIG. 4, and the flange surface F represented by 12.
is listed.

Furthermore, in the case of automobile bodies, inner plate parts are particularly mentioned.

In Figure 2, the interpolation formula between each point is
It is assumed that the value is calculated using the following formula for C00NS display.

That is, when the space curve t (Fig. 2) is expressed by a cubic parameter equation based on the difference, it becomes t(, t) - A, t + B, t + C, t + D,
Also, the C00NS display type can be used, for example, at point P1 in FIG.
Taking P2 as an example, tke)=Pt + (P2-Pl)f (,t)+T
R17Ci)+'h, A(f).

As is clear from Fig. 5, the initial conditions for determining %t(f) are t(0)-Px, bow, QO)=TR t(1)=P2, μHowever-TLi From t(0)=Px, fc01= O, g(0)=
0, h (01=0A(1)=P2)
f(1)=1, ,! 7(1) = O, A(1)-
From 〇g-TR Mamoru-0, Uri = 19 P = 09 P = T
From L difference 6P-0,1T=0,1r=1dg(1)
dA(1).

Therefore, one of the arbitrary functions that satisfies each of the above conditions is f(kari(3-2i),, v(i)=i(i-1),
ACi)-'s (difference -1).

When these functions are substituted into the C00NS expression, A(i
)=(-2(P2-Pi)xTL+TR)s++3 (
P2-PI)-Tt,-2TR)i2+Th, 10P1
When this equation is compared with the coefficients of the parameter cubic equation described above and displayed in a matrix, the following is obtained.

In this matrix display formula, P+.

Since P2, Th, and TL are known numerical data written in the body data file 3, the coefficients A, B, C, and D of the parameter cubic equation are naturally determined.

Therefore, in FIG. 5, the data between points Pl and P2 can be obtained by changing the difference from O to 1 in the parameter cubic equation whose coefficients have been determined.

Note that each of the above calculations is performed by the control section 1 shown in FIG. 1 by reading data from the body data file 3.

However, as mentioned above, the data written in body data file 3 is numerical data in the car line coordinate system, so when the panel represented by the data is placed at the welding work position, the teaching work will be changed as described later. Coordinates are converted to data in an arbitrarily set coordinate system.

Further, the curved surface data is as shown in Table 2 in the case of the curved surface S shown in FIG. 6, for example.

However, in Table 2, M=3. N=3 is the 6th
The number of points in the U direction and υ direction in the figure is
Also l TaRjノ'l, l T
aLino1, ITvRino'l, IT
vLijl are respectively points Pi as shown in FIG.
is the absolute value of the four tangent vectors at .

Then, the curved surface S represented by each of these data
is written in the body data file 3 for each multiple panel name as one element of the panel shape.

Note that panel shapes that can be represented by such curved surface data include those that include as many character lines as the outer panel of a vehicle body.

In addition, four punches 81 forming the curved surface S shown in FIG.
~ Any point data in S4 is still C00NS
It can be easily determined by interpolation.

Then, the parameter equation of the curve or curved surface found based on the curve or curved surface data as described above becomes a function representing the shape of the panel member or the like which is the member to be welded.

Next, a method for determining the welding point position will be described.

First, the ANK 8 shown in FIG. 1 is operated to read out panel data for which the welding point layout is to be made from the body data file 3 and input it into the control section 1.

After converting the read numerical data into data in the coordinate system of the placement destination, the control unit 1 obtains an interpolation formula representing the shape of the panel according to the method described above, and creates a shape model of the panel represented by the interpolation formula. Display on CRT 6.

Assuming that the panel displayed on the CRT 6 is a shape model 12 as shown in FIG. 8, the layout of welding points on the flange surface 12a of this shape model 12 will be described below.

In FIG. 8, lead wires LL are formed to lay out welding points on the flange surface 12a.

Since this lead line LL must be included in the flange surface 12a formed by the contour line L1o and tzo expressed by the above-mentioned interpolation formula, for example, the offset amount r from the contour line 11o can be calculated as ANK in FIG. By inputting the offset amount r in step 8, it can be calculated from the offset amount r and the above-mentioned interpolation formula.

Next, the welding point position is specified by hitting a desired position on the lead wire tL on the CRTB using the light pen 7 shown in FIG.

When a welding point position is specified, an * mark is displayed at that position as shown in Fig. 8, and the numerical data of the welding point position p (x, y, z) is displayed in a predetermined area of the CRT 6. Ru.

Then, the specified welding point position P is evaluated based on the display position of the * mark and the numerical data, and this welding point position P
If it's good, move on to the next task; if it's bad, re-specify.

The numerical data of the welding point position p (, z, y, z) can be obtained based on the interpolation formula of the lead wire tL and the position on the CRT 5 hit by the light ben 7.

In addition, the numerical data of the welding point position P (x, y, z) is
For example, z=150.15. y=164.3. z=12.
Since the numbers often have fractions such as 50, the numbers are externally set using ANK 8 in FIG. 1 to round off the fractions of these numbers.

Note that when the above numerical values are rounded in this way, the * mark in FIG. 8 moves slightly on the lead line tL accordingly.

Next, after determining the welding point position P ('', y + z), the normal vector a at the welding point position P (x, y, z) is determined as follows.

That is, for convenience of explanation, it is assumed that the lead line AL in FIG. 8 is a curve as shown in FIG. The vector difference is determined, and the construction normal line unit vector is determined from this tangent vector difference.

The desired normal (binormal) vector α can be obtained by calculating the vector product of the tangent unit vector difference and the construction normal unit vector.

In FIG. 9, Si is a tangential plane containing vectors f and n, and SrL is a normal plane containing vectors α and n.

When the normal vector α is obtained in this way, the control unit 1 displays a line segment representing the normal vector α as shown in FIG. do.

The reason why the normal vector a at this welding point position P was determined is that in spot welding, the best position is for the tip (electrode) of the welding gun to be perpendicular to the welding surface.

Next, after determining the normal vector a, the approach vector b indicating the approach direction to the welding point position P of the welding gun attached to the tip of the movable part of the welding bot (described later) is converted into the normal vector a. Specify the condition perpendicular to .

However, this approach vector b is the normal vector α
For example, if there is only a condition perpendicular to the tangential plane S shown in FIG.
Since it is sufficient that it is included in i, there are an infinite number of possibilities, but here, for example, a rule obtained by reversing the direction of the principal normal unit vector n shown in FIG. 9 is temporarily set as the approach vector b.

Then, the data of the welding point position P, normal vector α, and approach vector 4 obtained as described above are temporarily written into the design file 4 shown in FIG.

The other welding point positions on the lead wire LL in FIG.
By inputting it in ANK 8 in the figure, the subsequent welding point position can be automatically determined by calculation.
The normal vector and approach vector at each welding point position are also determined as described above, and the determined data are also written in the design file 4 shown in FIG.

After completing the layout of welding points in this way, it is time to CR the panel, the jig to place it, and the welding gun at the same time.
T6 to examine the state of interference with other parts of the welding gun.

First, regarding the display of the welding gun, the ANK in Figure 1
8 to read the numerical data group representing the welding gun attached to the tip of the movable part of the welding robot to be taught from the standard product file 2, and read out the previously written welding point position data and method from the design file 4. Line vector data.

and one of the data consisting of approach vector data
Read the set.

Then, the shape model of the welding gun is reproduced based on the numerical data group representing the welding gun and displayed on the CRT 6. In this case, the numerical data group representing the welding gun is based on the arbitrarily set coordinate system described above. The welding point position data and normal vector data read from the design file 4 are converted into values, and the arrangement position and orientation of the welding gun in the coordinate system are the welding point position data and normal vector data read from the design file 4.

and approach vector data.

Therefore, the relationship between the welding gun displayed on the CRT 6 and the shape model 12 representing the panel is as shown in FIG. 11, for example.

In addition, in FIG. 11, the welding point ip is the welding gun 1.
The center between the tips 13a and 13b of No. 3 is located, and the normal vector a indicates the angle (posture) of the welding gun with respect to the flange surface 12a, and the approach vector b indicates the welding point position P of the welding gun 13. The approach angle of each is determined.

Next, a method for examining the interference state of the welding gun 13 based on the display mode of the welding gun 13 as described above will be described.

Now, assuming that the member for which the dot layout has been completed as described above is the rear side member 16 to be welded to the rear floor panel 15 as shown in FIG. indicate.

In addition to these welding guns, the rear floor panel 15°, and the rear side member 16, a jig 14 consisting of a pace 14a and a pole 14b for setting the rear floor panel 15, rear side member 16, etc. as shown in the figure is installed in the standard product file 2. Display based on data in.

Although only partially shown in FIG. 12, in reality, the rear floor panel 15 and the rear side member 1
The 6th mag is supported by four poles.

In addition to the illustrated jig 14, jigs such as a locate pin, a gauge post, and a clamp post are also actually displayed.

Then, looking at the screen of the CRT 6 displayed in this way, the welding gun 13 moves to the pole 14b and the rear floor panel 15.
If there is any interference, operate the VCD 10 shown in Figure 1 to rotate the welding gun 13 in the δl or δ2 direction around the welding point position to avoid interference. .

-20- Note that when the welding gun 13 is rotated in the δ1 or δ2 direction, the approach vector b also becomes (α, h)=.

Change while satisfying.

Furthermore, if the interference state of the welding gun 13 cannot be considered at the screen display angle shown in FIG. 12, it is sufficient to rotate the screen display angle. What is necessary is to take a cross section of each part and display the cross-sectional shape on the CRT 6.

After determining the approach vector b in which the welding gun 13 does not interfere with other parts in this way, each data of the approach vector b, normal vector α, and welding point position P is saved in the design file 4 of FIG. Write.

Then, after checking the interference state of the welding gun 13 at each of the remaining welding point positions, the final welding point position data and normal vector data described above are obtained.

Synthesis is performed to calculate the posture position data of each axis that constitutes the movable part of the welding robot based on the approach vector data.

First, the shaft configuration of the welding robot will be explained with reference to FIG. 13.

In the figure, the welding robot 20 includes a base 20A and a first rotating part 2 that rotates in the θ1 direction with respect to the base 20A.
0B, a first rotating section 20C that rotates in the θ2 direction with respect to this first rotating section 20B, an extendable section 20D that extends and contracts in the t3 direction with respect to this first pivot axis 20C, and this extendable shaft 20
A second rotating part 20E rotates in the θ4 direction with respect to D, a second rotating part 20F rotates in the θ5 direction with respect to this second rotating part 20E, and a second rotating part 20F rotates in the θ6 direction with respect to this second rotating part 20F. 20G, and a third rotating shaft 2
Attach the welding gun 13 to the tip of the 0G.

In the following description, the arrangement position of the base 20A of the welding robot 200 is assumed to be the origin position of the arbitrarily set coordinate system described above.

In addition, the lengths of the base portion 20A and the first rotating portion 20B are respectively C.
,, C2 (constant), the first turning part 20C and the telescopic part 20
The combined length of D is Ll (variable), and the second turning section 2
The length from 0E to the bending position (90° bending position) of the second rotating part 20F is defined as ck (constant), and the second rotating part 20
Let the combined length of the remaining portion of F and the third rotating portion 20G and the length of the welding gun 13 be CS and G2 (constants), respectively.

Furthermore, let θ1 to θ6 and t3 described above be displacement variables for each axis.

Now, the characteristic equation of the welding robot 20 under the above conditions is as follows: ))).
However, in the above formula, P is the tip 13a of the welding gun 13.
, 13b (see FIG. 11) are the welding point positions where E"', E"2. Eno", Ek"5゜E"'
are rotary tenors around the axes shown in FIG. 13, respectively.

Next, in the above formula, Ekol (in, and E′.6
(Gs) can be abbreviated as bow and G2, respectively, so P=C;+C:+E"'E""(L:)+Ek"'E
"2E'.'CC',) 10 Ekel EJ'62 E
j04 Eka5 (Ci tenai)
,,, ,,, ・++.

6 It can be expressed as

=23- Next, in formula ■, R12 = Ck + Ck (known value) 2 R34 = Ek'''E''2(L') R56 = EA
''E"2E"' (Ck)R78= Ekol E
If j′2Ej(14E k05(c L +ct )6, then the formula ■ is P=R12+R34+R56+R78...
・It becomes ■. Now, when the approach vector b is given in the formula, Rys is determined, and it is expressed as R78= (r
7g, 3178, 278).

Next, in formula ■, R34+R56 is R=(α,
β.

γ), then R is R=P-R12-R78 becomes.

By the way, the vector obtained by projecting R34 onto the 2-plane and the vector obtained by projecting R56 onto the t-plane have the same direction (condition (a)), and R? 8゜Rsa
are orthogonal to each other (condition (b)), and the absolute value of R56 is C4 (condition (c)).

Therefore, R56 is expressed as Rsa = (xss, ys6
．． 256) 24- Then, from condition (a), ysa/xss = β/α...
...■From condition (b), 11l'78 saucersa+yys"ysa+z'ys・z
56-0 ・・・・・・・・・■ From condition (1)), “56” 10y56” 10z56” = (C:)2””
""'■Next, from formula 0, 3'56 = 7! -T56
Get this ■.

α ■Substituting into the expression, becomes.

Then, by substituting this into the formula ■', we get can be expressed.

In addition, up to this point, R781R56, R□2. P
.

a, h are known.

Next, R34 is R34=RR56, which is converted into (
”34, y34.z34), then R3
Since 4=Ek0'E"2(L'), it becomes 97-, and from the [phase] formula, #1=jan'2 x 34 °°°°0゛°°°0t3
= 1R341=mΣ, 4” ・-・Song-@t,
R75=E"'E'e2E"'E"5 (Mushiboshi〇S)
When transformed, Ej (f12) Ek (el) R7, = Ejl) < Eke
5(c*,+ai) ,,,@, and since the left side of this equation 0 is known, we can write it as (xh l 3/A
If we set l z & ), then from the [phase] formula, θ4=tan () ... light ... [
phase]k θ5=jan' (shishin) ・・・・・・・・・0Also, (Z=Eko'E""E"'Ek05E"'((Z
O) [:C0: Reference normal vector (θ is all “
0'' vector, that is, a vector perpendicular to the vehicle plane)], so Ek(-05)FJノ(-θ4)Ej(-02)E
It is transformed as k(-θ”(a)=E’θ’(ao),
In this equation, the left side is known, (,T'.

y', z') and αo=(''+y+z), we obtain.

Therefore, in the characteristic equation (2), if the constant ckI C2" 4 y Cs + C"6 is given, and the welding point position P, normal vector a, and approach vector b are given, each axis of the welding robot 20 displacement (
Posture position data) θ1. θ2, t3, θ4. θ5
．． θ6 can be uniquely determined.

Therefore, for each welding point position data written in the design file 4 in FIG. 1, the above-mentioned 0 to 0. The arithmetic operation of the equation o~[phase] is performed, and the posture position data of each axis obtained thereby is outputted as teaching data via the teaching data output device 11 of FIG. 1 28-.

However, depending on the installation position of the welding robot 20, there is a risk that a part of the robot in the posture based on the above calculation result may interfere with other equipment (such as the jig 14 in FIG. 12).
It is a good idea to display the robot on the CRT 6 for each posture and examine whether there is interference, and if there is interference, redo the dot layout.

In the above embodiment, if the welding robot is dynamically simulated based on the calculated teaching data, the working time required for welding can be predicted.

As explained above, according to the present invention, teaching data can be created without actually moving the welding robot on site, so teaching work can be performed in a short time and without requiring any skill.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of a teaching device to which the present invention is applied, and FIGS. 2 and 3 are diagrams for explaining the specifications of the curve data written in the POD data file 2 of FIG. 1, respectively. , FIG. 4 is a perspective view showing an example of a panel shape represented by curve data, FIG. 5 is a diagram for explaining C00NS interpolation, and FIGS. 6 and 7 are body data of FIG. 1, respectively. A line diagram for explaining the specifications of the curved surface data written in file 2. Figure 8 is a CRT display screen diagram for explaining the welding point layout. Figure 9 is a method for determining the normal vector at the welding point position. Figure 10 is a CRT screen diagram showing an example of normal vector display; Figure 11 is a CRT screen diagram showing a welding gun display example; Figure 12 is a diagram showing the final FIG. 13 is a skeleton diagram showing the axis configuration of a welding robot. 1...Control unit 2...Standard product file 3...Body data file 4...Design file 6...CR
T-graphic display 7...Light pen 8.
...Alphanumeric keyboard 9...Function switch 10...Variable dial 11...Teaching data output device 12...Shape model 12a...Flange surface 13...Welding gun
13a, 13b...Chip 14...Jig 20...
・Welding robot Figure 1 Figure 2! Figure 3 Figure 4 Figure 12 Figure 13 Figure 0

Claims (1)

[Claims] 1. Find a function that represents the shape of the welded member in a predetermined coordinate system, display the shape model of the welded member represented by this function on a display, and locate the desired position on the shape model displayed on this display. After determining the welding point position of the workpiece by specifying with a conversational input means such as a light pen, the normal vector on the welding workpiece at this welding point position is combined with the welding point position data and the shape model. In addition, an approach vector indicating the approach direction of the welding gun attached to the tip of the movable part of the welding robot to the welding point position is specified under the condition that it is perpendicular to the normal vector. The teaching data for the welding robot is created by determining the posture position data of each axis constituting the movable part of the welding robot based on the uniform welding point position data, the normal vector, and the approach vector. How to create teaching data for welding robots.