JPH0375271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torch control method for an articulated welding robot having a plurality of axes, each of which is rotatable.

Figure 1 shows a typical welding robot of this type. Inside the swivel base 1 is a swivel motor (not shown).
, which causes rotation in the θ ₁ direction. A speed reducer, a speed detector (tachogenerator), and a position detector (encoder or resolver) are attached to the motor to control speed and position. In addition to these positioning commands and speed commands, servo commands are also commonly executed using microcomputer software. The arm/wrist drive unit 2 has four built-in motors having the same configuration as the above-mentioned turning motor. These are used to rotate the first arm 4 by θ ₂ , the second arm 5 by θ ₃ , and the wrist mechanism by θ ₄ and θ ₅ , respectively. A parallel link is formed to the first arm 4 by first arm links 10a, 10b and a lever 4a integrated with the first arm 4, and the pivoting motion is transmitted. Similarly, 11,
The turning motion is transmitted by parallel links 12a, 12b, and 3 for the second arm. The turning motion is transmitted to the wrist mechanism section through parallel links using two sets of chains on the first arm and two sets on the second arm. The angle of the welding torch is controlled by the rotation of the wrist mechanism 6 and the torch bracket 7.

In the above-mentioned welding robot, the teaching of the welding line is performed by a method called the so-called PTP method, in which interpolation is performed between a plurality of taught points as shown in the following equation.

The first teaching point X ₁ , Y ₁ , Z ₁ , θ ₄₁ , θ ₅₁ (X, Y, Z are the torch tip coordinates, the subscript 1 is related to the first teaching point, and the first subscript of θ is the (corresponds to the turning angles θ ₄ and θ ₅ , and the second subscript indicates that it relates to the first teaching point) second teaching point X ₂ , Y ₂ , Z ₂ , θ ₄₂ , θ ₅₂ (X, Y, Z The subscript of θ is related to the second teaching point, and the second subscript of θ is related to the second teaching point.
( _Others ^{are the} same _as above ⁾ _L ⁼ {( _{X 2 -} If the length between the first teaching point and the second teaching point is L and the division pitch ΔL, then N=L/ΔL.

Torch tip coordinates between the first teaching point and the second teaching point and turning angles θ ₄ and θ 5 of the first arm 4 and second arm ₅
are X _n , Y _n , Z _n , θ _4n , θ _5n (the subscript m indicates the torch tip coordinates, etc. at the m-th division), then X _n =X ₁ +X ₂ −X ₁ /N・m0<m<N, Y _n =Y ₁ +Y ₂ −Y ₁ /N・m, Z _n =Z ₁ +Z ₂ −Z ₁ /N・m, θ _4n = θ ₄₁ +θ ₄₂ −θ ₄₁ /N・m, θ _5n =θ ₅₁ +θ ₅₂ −θ ₅₁ /N・m,

FIG. 2 shows a conventional robot control circuit, in which data necessary for teaching, such as the coordinates of a teaching point, is input from a teaching box 24 to an arithmetic unit 22.
The input data is stored in the storage device 25.

During operation, the detector 2 of each arm etc.
The inclination angles θ ₁ to _{θ 5} of each arm applied from 0 are read, converted into appropriate signals by a converter 21, and input to an arithmetic unit 22. The calculation processing method is as described above. During playback (playback), the arithmetic-processed data is output via the converter 23 to the motors _M1 to _M5 that drive the arms 4, 5, etc.

Then, in the arithmetic unit 22, a welding line is determined by linear or circular interpolation from the two first and second teaching points P ₁ and P ₂ read out from the storage device 25, and the welding torch 8 is moved to the welding line. is servo-controlled to move along.

On the other hand, factors that determine the quality of welding include welding current, voltage, welding speed, and welding torch aiming angle. In this specification, the torch aiming angle refers to the angle β of the projection axis of the welding torch 8 within a plane 31 perpendicular to the welding line 30, as shown in FIG. Furthermore, as shown in the figure, welding line 3
The angle α of the welding torch 8 with respect to 0 is called an inclination angle.

However, conventionally, the welding current, welding voltage, and welding speed are stored in a storage device as teaching information, but the above-mentioned torch aiming angle is not conventionally inputted. Therefore, the angles α and β of the welding torch were manually set.

Therefore, in conventional welding robots,
It was difficult to set an accurate torch aiming angle, which was an impediment to improving welding quality.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a welding robot that automatically controls the torch aiming angle by inputting the torch aiming angle.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, the teaching box 24 is provided with a numeric keypad for inputting the torch aiming angle β, and when the torch aiming angle β is inputted for each teaching point during welding, β
is stored in the storage device 25.

FIG. 4 shows a control program for setting the torch aiming angle β, and in step S1 the robot is driven to teach the first and second points. Then, in step S2, the actuator angle at each teaching point is stored in the storage device 25.

Next, in step S3, the torch tip coordinates (X ₁ , Y ₁ , Z ₁ ) (X ₂ , Y ₂ , Z ₂ ) at the first and second teaching points are calculated.

The first and second teaching points P 1 and P ₂ of the illustrated inclination angles θ ₁ to θ ₅ of the actuators such as the base 1, arms 4 and 5, and the welding torch 8 in the robot shown _{in FIG.}
The respective values in are shown separately with second subscripts 1 and 2, respectively (θ ₁₁ , θ ₂₁ , θ ₃₁ , θ ₄₁ , θ ₅₁ ), (θ ₂₁ , θ ₂₂ ,
θ ₃₂ ,
_{θ 42 , θ 52 ) , then , _ _ _ _ _ _ _ _} )}. r ₁ to r ₄ are shown in FIG.
X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ are also calculated in the same manner as above.

Next, in step _S4 , the first and second teaching points _P1 ,
Torch direction vector V _TT1 ---→, V _TT2 --- at P ₂
→ is calculated.

However, if V _TT1 ---→= (v ₁ , v ₂ , v ₃ ), then v ₁ = -(cosθ ₁₁・sinθ ₄₁・sinθ ₅₁ +sinθ ₁₁・cosθ ₅₁ ) v ₂ =−(sinθ ₁₁・sinθ ₄₁・sinθ ₅₁ −cosθ ₁₁・cosθ ₅₁ ) v ₃ = cosθ ₄₁・sinθ ₅₁

The torch direction vector V _TT2 ---→ at the second teaching point P ₂ is also obtained in the same manner.

Next, in step S5, the route direction vector V ₁ → is calculated.

However, V ₁ →={(X ₂ -X ₁ ), (Y ₂ -Y ₁ ), (Z ₂ -Z ₁ )}.

Next, in step S6, the taught inclination angle α ₁ at the first teaching point P ₁ is calculated.

However, α ₁ = cos ^-1 V ₁ ·V _TT2 / |V ₁ |×|V _TT2 |.

The same applies to the inclination angle α ₂ at the second teaching point P ₂ .

Next, in step S7, the torch aiming angle β is read from the storage device, and the process proceeds to step S8, where the reproducing direction vector V _TP1 --→ at the first teaching point _P1 is determined from _α1 and β.

The unit vector v ₁ → in the same direction as the vector V ₁ → is v ₁ = [X ₂ −X ₁ /(X ₂ −X ₁ ) ² + (Y
₂ −Y ₁ ) ² + (Z ₂ −Z ₁ ) ² } ^1/2 , Y ₂ −Y ₁ / {(X ₂ −X ₁ ) ² + (Y ₂ −Y
₁ ) ² + (Z ₂ −Z ₁ ) ² } ^1/2 , Z ₂ −X ₁ / {(X ₂ −X ₁ ) ² + (Y ₂ −Y
₁ ) ² + (Z ₂ − Z ₁ ) ² } ^1/2 ].

Let this be v ₁ →(v _x2 , v _y2 , v _z2 ).

Further, the unit vector in the vertical direction from the arc point is v ₃ →(0,0,1).

Furthermore, a unit vector v ₂ → horizontally from the arc point and perpendicular to the reproduction direction unit vector v ₁ →
is found as the cross product of v ₃ →, v ₁ →, which is assumed to be v ₂ → (v _x3 , v _y3 , 0).

First, the torch direction vector V _TP1 --→' of the torch aiming angle β with the inclination angle α=90° is determined as follows.

V _TP1 ---→'=-sinβ・v ₃ →-cosβ・v ₂
→ Next, the torch direction vector V _TP1 ---→ (unit vector) of the inclination angle α _A and the torch aiming angle β is determined as follows.

V _TP1 ---→=sinα ₁・V _TP1 ---→′+cosα ₁・v
₁ → Also, the reproduction torch direction vector V _TP2 ---> is similarly determined from α ₂ and β at the second teaching point P ₂ .

Then, in step S9, the vector V _TP1 ---→ and the torch tip _{coordinates (X 1 ,}
Find the angles θ ₁₁ ′ to _{θ 51} ′ so that Y ₁ , Z ₁ ) are obtained,
Control.

A specific calculation method will be described below (see FIG. 7).

Torch direction vector V _TP1 ---→ (v _p1 , v _p2 , v _p3 )
(V _TP1 ---→ is a unit vector.) Point A is (X ₁ , Y ₁ , Z ₁ ), point B is (X ₁₁ , Y ₁₁ , Z ₁₁ ) (the first subscript is related to the first teaching point). _{, the second} subscript indicates that _it relates _{to point B ) , then} X _{11 =} V _u1 ---→ (v _x1 , x _y1 , v _z1 ).

However, the vector V _u1 ---→ is a unit vector created by projecting the vector connecting point O and point B onto the horizontal plane, and v _X1 = X ₁ − r ₄ v _p1 / {(X ₁ − r ₄ v _p1 ) ² + (Y ₁ −r ₄ v _p2 ) ²
} ^1/2 , v _y1 = Y ₁ − r ₄ v _p2 / {(X ₁ − r ₄ v _p1 ) ² + (Y ₁ − r ₄ v _p2 ) ²
} ^1/2 , v _Z1 = 0.

Next, the vector BC connecting point B and point C can be expressed as r ₃ cosθ ₄₁ ′(−v _x1 , −v _y1 , −tanθ ₄₁ ′) (1).

Since BC→⊥V _TP1 ---→, BC→・V _TP1 --→=0, that is, −v _p1・v _X1 −v _p2・v _Y1 −v _p3・tanθ ₄₁ ′=0, and θ ₄₁ ′ = tan ^-1 (-v _p1・V _X1 −V _p2・v _Y1 /v _P3 ).

Then, θ ₄₁ ' can be found.

By substituting this θ ₄₁ ′ into the vector display section of (1), the vector BC→ is found.

The coordinates of point C (X ₁₂ , Y ₁₂ , Z ₁₂ ) (the second subscript indicates that it relates to point C, the rest are the same as above) are X ₁₂ = X ₁ − r ₄ · v _p1 − r ₃ · v _x1 Y ₁₂ = Y ₁ −r ₄・v _p2 −r ₃・v _y1 Z ₁₂ ＝Z ₁ −r ₄・v _p3 −r ₃・sinθ ₄₁ ′.

Below, from point C (X ₁₂ , Y ₁₂ , Z ₁₂ ) θ ₂₁ ′, θ ₃₁ ′,
Find θ ₁₁ ' (see Figure 8).

R=(X ₁₂ ² +Y ₁₂ ² +Z ₁₂ ² ) ^1/2 θ ₂₁ ″=tan ^-1 {Z ₁₂ /X ₁₂ ² +Y ₁₂ ² ) ^1/2 } θ ₂₁ = cos ^-1 (R ² + r ₁ ² −r ₂ ² /2・r ₁ R) θ ₂₁ ′=90°−θ ₂₁ ″−θ ₂₁ determines θ ₂₁ ′.

Also, θ ₃₁ ′ can be found from θ ₃₁ ′=sin ⁻¹ (Z ₁₂ −r ₁ sinθ ₂ /r ₂ ).

Furthermore, θ ₁₁ ′ is found from θ ₁₁ ′=tan ⁻¹ (Y ₁ /X ₁ ).

Point D (X ₁₃ , Y ₁₃ , Z ₁₃ ) (the second subscript indicates that it relates to point D, the rest is the same as above) is the case where θ ₅₁ ', which is subsequently sought, is 0. This is the torch tip position, and point B (X ₁₂ , Y ₁₂ ,
Z ₁₂ ), vector v _u1 -→ (v _x1 , v _y1 , 0) (9th
_{( see figure ) , X 13 = _ _ _ _ _ _} Find the vector BA→ from points A and B, and the vector BD→ from points D and B, and get |BA→×BD→|=|BA→|・|BD→|・sinθ ₅₁ ′ θ ₅₁ ′=sin ^-1 | θ ₅₁ ′ can be found from BA × BD | / | BA | · | BD |.

Similarly, in step S9, the above vector V _TP2 ---→ and the torch tip coordinates ( _{X 2 ,} Y ₂ ,
Find the angles θ ₁₂ ′ to θ ₅₂ ′ so that Z ₂ ) is obtained.

Note that instead of calculating the inclination angle α ₁ , it may be input using a numeric keypad or the like. Furthermore, when inputting with the numeric keypad, the first key used in general welding terminology is
It is easier to understand if the inclination angle α' is expressed as an angle from a line perpendicular to the direction of movement, as shown in Figure 0. The relationship with α defined so far is α′ = 90° − α Note that α′ < 0° is generally called a sweepback angle, but it is easier to understand by inputting a sweepback angle of 10° as an inclination angle of -10°. , when α>90°, (90°−α) may be adopted as the inclination angle.

As an example of the torch aiming angle β, when performing fillet welding and multi-layer welding, as shown in Figure 5, β = 45° for the first layer, β = 50° for the second layer, and β = 50° for the third layer. In terms of welding accuracy, it is preferable to change the setting gradually so that β=40°.

Furthermore, so far we have described a method of controlling θ ₁ to _{θ 5} of the angular axis from the torch tip coordinates and torch direction vector at the teaching point, but if necessary, the interpolated torch Similar arithmetic processing may also be performed using the tip coordinates and torch angle as taught data.

As detailed above, according to the first invention, in the welding robot, the welding torch at each teaching point is controlled by inputting the aiming angle of the torch in a plane perpendicular to the welding line direction to the arithmetic and control device. Since the angle is controlled taking into account the aiming angle mentioned above, it is possible to accurately and automatically set the aiming angle, which has a great effect on welding quality, and it is also possible to change the aiming angle for each welding line. If this is preferred, the aiming angle can be sequentially changed to predetermined angles. Also,
Regarding the inclination angle, which has relatively little effect on welding quality and is taught for the purpose of avoiding interference between the workpiece and the cheek, interference with the workpiece can be prevented by making use of the taught data. In other words, it is possible to perform rational torch angle control by making use of meaningful tilt angles in the teaching data, and by using separate input data for target angles that have errors in the teaching, and this has the effect of improving welding quality. .

Further, according to the second invention, after the welding line direction is calculated from the angle data of each axis taught for at least two teaching points on the welding line, the inclination angle and aim angle with respect to the welding line direction are input. This method is suitable for welding in open spaces, and is also more suitable for offline teaching than direct teaching.In both direct teaching and offline teaching, teaching utilizes data only from the torch tip, and the torch angle is By inputting numerical values for the target angle and inclination angle regarding the welding line, accurate torch angle can be obtained and welding quality can be further improved. In addition, in the case of offline teaching,
The effect is that the torch angle, which is difficult to understand from a CRT screen, can be controlled easily and accurately by numerical input.

[Brief explanation of drawings]

Fig. 1 is a front view showing an example of an articulated welding robot having a plurality of axes that can be rotated; Fig. 2 is a block diagram showing an example of a control device for the welding robot shown in Fig. 1; 3 is a perspective view explaining the torch aiming angle, FIG. 4 is a flowchart showing an embodiment of the present invention, FIG. 5 is a diagram showing an example of the torch aiming angle, and FIGS. 6 to 9 show the torch angle. Figure 1 showing the torch and coordinates to explain how to find
FIG. 0 is a diagram showing an example of movement of the torch. 8...Welding torch, 30...Welding line, 31...
A plane perpendicular to the welding line, β...Aim angle of the welding torch, α...Angle of inclination.

Claims (1)

[Claims] 1. In a torch control method for an articulated welding robot having a plurality of axes and rotating each axis, an arithmetic and control unit is provided with each teaching point on at least two teaching points on a welding line. The welding line direction is calculated from the axis angle data, and the inclination angle of the welding torch with respect to the welding line direction is calculated from the angle data of each axis regarding the teaching point and the above welding line direction. The aiming angle of the welding torch at is input to the arithmetic and control device, and the arithmetic and control device inputs the inclination angle of the welding torch to the welding line obtained by the above calculation and based on the inputted aim angle,
A torch control method for a welding robot, characterized in that the direction of a welding torch is determined, and the angle data of each axis is calculated from this direction of the welding torch and the teaching point or interpolated point data to control the angle of each axis. 2. In a torch control method for an articulated welding robot that is equipped with a plurality of axes and is configured to rotate each axis, the arithmetic and control device performs welding based on the angle data of each axis taught for at least two teaching points on the welding line. The line direction is calculated, the aiming angle of the welding torch in a plane perpendicular to the welding line, and the inclination angle of the welding torch with respect to the welding line direction are input to the calculation and control device, and the calculation and control device is caused to perform the calculation. For the welding line direction determined by A torch control method for a welding robot, characterized in that the angle of each axis is controlled by calculating the angle data of.