JPS6213269A - Detecting method for welding start point - Google Patents

Abstract

PURPOSE:To reduce the motion steps of a robot and to increase the operability by providing a distance detector on the periphery centering around the shaft of a welding torch and the driving mechanism to locate it with its rotation and by detecting the symmetrical position independently of the robot motion. CONSTITUTION:A welding torch 3 is located on a welding start point P5 because of the welding start point P5 and the same completion P6 being taught in advance. Now when a distance sensor 5 is rotated once by a driving device 6, the detection value for the scanning line 7 of the distance sensor 6 becomes points A13-A15. The points A16-A18 are found with one rotation of the distance sensor 5 once again by moving the welding torch 3 along the weld line to a position P7 then. The equation of space straight lines l1, l2, l3 is found by using the points A13-A18. Consequently the cross point of the space straight lines l1, l2 corresponds to a welding start point WS and the l3 becomes corresponding to the weld line direction and found by a formula and these operations are performed by using a control device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a welding start point detection method, and particularly to a welding start point detection method applied to a welding robot.

[Conventional technology]

Generally, the welding start point detection method applied to this type of welding robot is to bring a welding wire to which ground potential or high voltage has been applied to the workpiece by the robot itself, and to obtain a signal from this contact. The target welding starting point position can now be recognized from this point. Means using a so-called touch sensor is widely adopted.

A conventional method of detecting a welding start point using a touch sensor is shown in FIGS. 5 and 6.

That is, in each of these figures, reference numeral 1 indicates a workpiece to be welded, 2 a welding line or welding groove, 3 a welding torch of a welding robot, and 4 a welding wire.

However, in the case of this conventional example, the welding robot is provided with a teaching and reproducing function to teach the position of the object to be welded l with respect to the welding line or welding groove 2.

That is, point P P or p3. In this case, the welding start point ws1.p4 is taught using the touch sensor. In order to detect ws2, the following means are adopted.

First, in the case of horizontal fillet welding shown in FIG.
Next, the position of each horizontal plane is detected using the contact point A2, and the direction of the welding line 2 is corrected using the contact point A3, and then the welding wire 4 is moved to the detected welding line 2
The end of the workpiece 1 as the object to be welded is detected by the contact point A4, and the welding start point S1 on the welding line 2 is calculated by each of these steps.

In addition, in the case of V-groove butt welding shown in FIG. Find the center position of the groove in the same part by ○ to the point, and in the same part by contact point A7 and contact point A8, find the direction of weld line 2 from these two groove center positions, and calculate this. Move along the direction,
The end of the workpiece 1 as the object to be welded is detected by the contact point A9, and each contact point A10. A11 and A12 are detected respectively, and the welding start point l1lIS2 on the welding line 2 is calculated.

[Problem that the invention seeks to solve]

However, in the conventional method described above, many movement steps are required to detect the welding start point, and since a touch sensor is also used, the robot must operate at low speed to detect each contact point. First, there is a problem in that it takes a very long time to detect the welding start point.

Therefore, it is an object of the present invention to provide a welding start point detection method applied to a welding robot, which allows the welding start point to be detected quickly and with high precision.

[Means for solving problems]

In order to achieve the above object, the welding start point detection method according to the present invention includes disposing a distance detector that is freely rotationally positionable on the circumference around the welding torch, and The target position can be detected independently of the robot operation by the operation of the welding robot, thereby replacing the operation steps of the welding robot necessary for detecting the welding start point with the simple operation of the distance detector. This is what I did.

[For production]

In other words, in the method of the present invention, the welding start point is detected by the operation of the distance detector, so the number of robot operation steps conventionally required to search for the welding start point can be significantly reduced. , short takt time can be realized, and therefore welding productivity using this type of welding robot can be improved.

〔Example〕

Hereinafter, one embodiment of the welding start point detection method according to the present invention will be described in detail with reference to FIGS. 1 to 4.

First, FIG. 1 is a configuration explanatory diagram showing the relative positional relationship between the welding torch of the welding robot and the welding line of the workpiece at the time of starting welding to which this embodiment method is applied. In the method of the embodiment shown in FIG. 1, the same reference numerals as in the conventional method shown in FIG. 6 is a drive mechanism such as a pulse motor that rotationally positions the distance sensor 5; 7 is the rotation of the distance sensor 5 when the welding torch 3 is positioned at a pre-taught starting point P5; Scanning trajectory, 8 is taught welding line p
5. A rotation scanning locus of the distance sensor 5 when the welding torch 3 is positioned at a point P7 on the extension of p6, 8 is a signal information processing processor from the distance sensor 5, and 10 is a robot control device.

In this case, the distance sensor 5 may be a non-contact sensor using triangulation such as laser distance t↑, and as described above, in combination with the drive mechanism 6, it can be rotated around the welding torch 3. By doing this, the tool system of the welding robot, as shown, the coordinate system of the welding torch 3 xt-vt-
It is possible to detect the three-dimensional position of the object to be welded, that is, the weld, as seen from zt.

FIG. 2 shows the principle of detecting the position of the object to be welded. That is, if the Z axis of the tool coordinates is parallel to the axis of the welding torch 3 and the origin is equal to the welding point, then the detection point Pi in the tool coordinate system Xt-Yt-Zt
The position of is Xt=Rcosθ −−−−−−
(1) ρ Yt=Rsinθ , −0, −(
2') is = Lo-L...
...It is obtained by (3). Here, θ is the rotation angle of the distance sensor 5 detected by the drive device 6, L is the detected value of the distance sensor 5, and R is the welding torch 3. This is the distance between the distance sensors 5.

In addition, in the control system of the welding robot, since the transformation matrix T in the absolute coordinate system of the welding torch 3 is known, if the expression Pi in the absolute coordinate system at the detection point Pi is
= (X, Y, Z) can be easily determined by calculating the following formula, and using such a distance detection mechanism, the welding starting point WS can be found.
is detected as follows.

That is, first, in the teaching process of the welding robot, the welding start point position P5. Since the end point P6 is taught in advance, the welding torch 3 is controlled by the robot controller 10 to
Taught welding start position p5 (this point is the object to be welded,
In other words, due to installation errors of the work 1, etc., the work 1 is positioned at a position that is shifted from the actual starting point. Then, the drive mechanism 8 causes the distance sensor 5 to rotate around the welding torch once, and the distance detection value is sampled at every fixed time ΔT.
The distance data L and the senna rotation angle θ are simultaneously stored on the RAM of the signal information processing processor S.

In this case, the detection value for the scanning line 7 of the distance sensor 5 in FIG. 1 is as shown at fold 1111 on the graph in FIG.
3"14"15 correspond to the break points of the broken line 11 on the same graph. Therefore, each corner position (0□
3"13)' (θ14.L14).

(015, A15) can be obtained, and as mentioned earlier, the position of each point in the absolute coordinate system can be calculated.

Next, move the welding torch 3 along the taught welding line (to 77).
Move the teaching point P to a position P7 (see Fig. 1) that is R/2 away from the teaching point P6 in the opposite direction, and then move this position again.
By rotating the distance sensor 5 once around the welding torch 3, the absolute positions of the points A1B''l□ and A18 are determined by the same procedure as described above.

Furthermore, each feature point AI3 obtained in this way.
AI4. A15. A1B, AI? , A18, the spatial straight line 1. shown in FIG. ,! ;L2. Find the equation of Q.

This means that the coordinate values at each point are A13"13''
13・2L3)・”!4”14・’+4・214)・A
15"15・ゞ15・215), and also AIG
"18'! 18,216" AI? "17"+7'z17
"A18"18"18,218), then each of these spatial lines IJafL1. Sentence 2. Sleeves can be obtained as follows.

Therefore, in this case, the spatial straight line 1. , fL2 corresponds to the welding start point WS, and is also a spatial straight line. corresponds to the actual welding line direction, and the welding start point WS can be determined by the following equation.

x − [LtL2(y15-713) (LIM2!
15-L2M1!13)]/(L2M1-L1M2)
Scream...(9)y=-[MM C! −
x ) − (M, L2y15 − N2Lly13)]/+
2 15 13 (L2M, -L, N2) ・・・・・・
(10)z = [N, N2(x15-x, 3)-(N
, L2z15-N2L1z, 3)]/(N2L1
- Nt L 2) ・Old PE11)
Here, Ll"!113-!13"1=yI8-'+3"1"
216-213L2=”18-!15°’2=’1
8-'15'N2:218-215.

Each of these calculations can be effectively executed using the robot control device IO, and as described above, in the case of this embodiment, each coordinate value of the teaching start point P5 is calculated from the detection start point -S. This allows for good and appropriate correction.

〔Effect of the invention〕

As detailed above, according to the method of the present invention, the distance detector is rotatably arranged on the circumference centered on the axis of the welding torch, and the rotation angle position of the distance detector can be freely positioned. A drive mechanism is provided to move the welding torch,
The teaching start point position corresponding to the welding start point given in advance and the position separated by a predetermined distance along the teaching welding line from this teaching start point are respectively moved and positioned, and each of these moving positions is By rotating the distance detector, the characteristic points of the change in distance between the object to be welded and the object to be welded are extracted. In other words, the points where the distance changes sharply are detected, and each of these points is detected. Since the welding start point is corrected and determined based on the welding point, the target position can be detected easily, quickly, and with high precision using a simple rotating motion of the distance detector, which is separated from the motion of the welding robot. This makes it possible to reduce the number of operational steps required by the welding robot to search for the welding start point, and has practical benefits such as improving the workability of welding equipment using this type of robot. It has excellent features.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an outline of the welding mode by a welding robot to which an embodiment of the welding start point detection method according to the present invention is applied, and FIGS. 2(a) and (b) are the absolute A plane showing the principle of position detection. 3 is a graph showing the distance detection data as above, FIG. 4 is a perspective view illustrating means for determining the welding start point as above, and FIGS. 5 and 6 are different conventional examples as above. FIG. 6 is a perspective view illustrating means for determining a welding start point according to the method. l... Work (object to be welded), 2... Welding line of work, 3... Welding torch, 5... Distance sensor (distance detector), 6... Drive Mechanism, 7.8...
・Rotation scanning trajectory, 8...signal information processing processor,
10... Robot control device. Agent Masuo Oiwa Figure 1 Figure 2 (a) (b) Figure 3 Figure 4

Claims (1)

[Claims] A welding device that can perform welding operations by moving a welding torch along a welding line to an object to be welded,
A distance detector is disposed rotatably on a circumference centered on the axis of the welding torch, and a drive mechanism is provided to freely position the rotational angle position of the distance detector, and the welding torch a teaching start point position corresponding to the welding start point, and a position separated by a predetermined distance along the teaching welding line from this teaching start point, and rotate the distance detector at each of these moving positions. A method for detecting a welding start point, characterized in that a welding start point is determined from each of these detection points by detecting a location where the distance between the welding object and the object to be welded is steep.