JPH0440116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention performs arc welding while rocking the welding torch in the groove width direction according to a predetermined rocking pattern, detects a positional shift of the welding torch during this rocking, and The present invention relates to a welding line tracking method in a welding robot, which aims to dramatically improve welding line tracking performance in a welding robot that allows the welding torch to follow the welding line by correcting this positional deviation.

As a method of teaching the above-mentioned swing pattern, there is a method in which the tip of the electrode of the welding torch (welding point) is actually positioned near the groove, and the positions of both end points of a half cycle of the swing pattern are taught. As proposed in the patent application dated March 2, 1982 (name of the invention "Welding Robot"), it is equipped with a means for creating a swing pattern by inputting numerical values, and it is possible to visually observe and position within the coordinate quadrant including the bevel during teaching. There is a method in which the welding torch is positioned at an arbitrary point (referred to as a dummy point) that is easy to move, and the swing pattern is taught while the torch remains stationary.

Conventionally, when a swing pattern is taught as described above (either manually or automatically), the computer that controls the entire welding robot creates a virtual welding line (also called a pattern reference line) that connects the taught points.
The oscillation pattern is created by regarding it as a welding line, but
Welding lines are not necessarily straight lines, but are usually bent or curved along the way, or oriented in various directions. In addition, when the computer executes Arcenser, the direction in which correction is applied is limited to the direction perpendicular to the virtual welding line, and the amount of correction is limited to the swinging end point of the welding torch tip (however, when correction is applied, the position of the swinging end is It is fixed within an angle of Δγ (a certain correction range) to the left and right of the virtual welding line with respect to the virtual welding line. For example, in Fig. 7, when performing continuous horizontal fillet welding from welding start point a to welding end point (not shown) along the actual welding line WLa of workpiece Wa, the computer The line connecting the end point is defined as a virtual weld line WLa', and a swing pattern PT is created with this as the base of an isosceles triangle, and an execution command is issued. Therefore, the tip of the welding torch is a
→ b → c, and even after reaching c, there is still work Wa
Therefore, from then on, it moves in the direction perpendicular to the virtual welding line WLa' (that is, in the groove width direction) as shown by c→d until it reaches the workpiece Wa. The next pattern is d → e → f → g (however,
(f→g is due to correction). Furthermore, the next pattern is drawn as g→h→i→j with g as the starting point. In this pattern, the weld line WLa is
Since the angle Δγ with respect to the virtual welding line WLa′ is centered on
Unable to follow WLa.

In view of the above-mentioned circumstances, the present invention teaches the positions of the first teaching point and the second teaching point, performs arc welding while swinging the welding torch in the groove width direction according to a predetermined swinging pattern, The welding robot detects a positional deviation of the welding torch during the swinging and corrects this positional deviation to cause the welding torch to follow the welding line between the two teaching points. The line connecting the two points is defined as the first pattern reference line, and while the swing pattern is being executed from the first teaching point to the first pattern reference line as a reference, the swing is made by a correction amount according to the detected amount of positional deviation each time. Correcting the motion pattern in a direction perpendicular to the first pattern reference line, and connecting the execution start point and end point of the swing pattern based on the first pattern reference line when the swing pattern has completed a predetermined number of times. Set the line extension direction to the second
The rotational correction is performed on the swing pattern by changing the first pattern reference line to the second pattern reference line, and thereafter, the swing pattern is calculated using the second pattern reference line as a reference. During execution, each time the swing pattern is corrected in a direction perpendicular to the second pattern reference line by a correction amount according to the detected amount of positional deviation, and when the predetermined number of swing patterns is completed, the second pattern is corrected. The extension direction of a line connecting the execution start point and end point of the swing pattern based on the pattern reference line is determined as a third pattern reference line, and the second pattern reference line is changed to the third pattern reference line. By doing so, the rotational correction is applied to the oscillation pattern, and thereafter, the pattern reference line is sequentially changed at each of the predetermined times of the oscillation pattern, and arc welding is performed until the second teaching point is reached while applying rotational correction to the oscillation pattern. It is an object of the present invention to provide a welding line tracing method in a welding robot that is characterized in that it performs the following steps, and is capable of following even a free curved welding line.

Hereinafter, a detailed description will be given based on the embodiment shown in FIGS. 1 to 6.

1 is a vertical axis constructed at the terminal of a rectangular coordinate (X, Y, Z) robot RO (details not shown) adopted as an embodiment of the present invention.

Reference numeral 2 denotes a first arm supported at the lower end of the vertical shaft 1 so as to be able to rotate around the shaft 1 (arrow α).

A second arm 3 is supported at the tip of the arm 2 so as to be rotatable around an oblique shaft 3a (arrow β). A welding torch 4 (an MIG welding torch in this embodiment) serving as an end effector is attached to the tip of the second arm 3.

The shafts 1, 3a, and the central axes M of the torch 4 are configured to intersect at one point P.

Further, the torch 4 is set so as to coincide with the welding operating point P thereof. Thus, by controlling the rotation angles in the α and β directions, the attitude angle θ and the rotation angle φ (so-called Euler angle) of the torch 4 with respect to the vertical axis 1 can be controlled with the point P fixed.

5 is a welding power supply device. The device 5 comprises a spool 7 on which a consumable electrode 6 is wound onto the torch 4;
Although the details are not shown, the feed roller is rotated and the electrode 6 is
It is possible to pull out the electrode 6 and the workpiece W.
The structure is such that a welding power source 8 and a current sensor 9 can be connected in series between them.

Reference numeral 10 denotes a known computer as a control device for the entire embodiment. The computer 10 has
Including CPU and memory.

And on the bus line B of the computer 10,
A power source 8 and a current sensor 9 are connected.

The bus line B is further connected to the X-axis servo system SX of the robot RO, and this servo system SX includes an X-axis power MX and an encoder EX that outputs its position information. Similarly, the bus line B has a Y-axis servo system SY configured in the same way,
Z-axis servo system SZ, α-axis servo system Sα and β
The axis servo system Sβ is connected.

Reference numeral 11 denotes a remote control panel, including a manual operation snap switch group SW for manually moving the torch 4, a speed command rotary switch SV for commanding speeds other than welding, and three types of modes (manual mode M, test mode). TE, mode selector switch SM for switching to auto mode A), numeric keypad TK, condition setting selector switch SE for setting various conditions at each switching position described later by operating the numeric keypad TK, and operation in each mode. Start switch used to start teaching and import teaching contents into memory
Equipped with STA etc.

The changeover switch SE has seven changeover positions SE ₁ to SE ₇ as shown below.

(1) Switching position SE ₁ ...Equipped with three display lamps for linear interpolation "L", circular interpolation "C", and arc sensing "As", by pressing key numbers "1" to "3" on the numeric keypad TK. You can select by lighting each indicator lamp.

(2) Switching position SE ₂ ...has a display section for welding condition number WNo., and the welding voltage E, welding current I, and welding speed are stored in the memory of the computer 10 for each number in advance.
Vw is stored as a set, and can be called up by pressing the key number on the numeric keypad TK that corresponds to the desired set.

(3) Switching position SE ₃ ...Has a display section for the function number FNo. In this embodiment, by operating key number "7" of the numeric keypad TK, the current position of the welding torch 4 is set to a dummy position instead of the teaching point of the movement position. Teach that it is a point.

(4) Switching position SE ₄ ...has a display section for the correction method number AUXNo. In this embodiment, when the key numbers "01", "02", and "03" of the numeric keypad TK are pressed, the switch position shown in FIG. As shown in a, b, and c, the weld joint shapes of downward fillet, horizontal fillet, and rectangular groove can be selected. Furthermore, AUX No. "10" means that the position is corrected based on data of a swing pattern created in advance with another work.

(5) Switching position SE ₅ ...has a pattern display section, and in this embodiment, the swing pattern is set using a four-digit number. For example, the 4th to 1st digits are the amplitude m (moving distance in the opening width direction) of the swing pattern, the height h (downward fillet and rectangular bevel as shown in Figure 2 a, b, and c). (in the case of horizontal fillets, it is the length of the leg), Pitch PC (the distance traveled in the direction in which the welding line extends during a half period of the swing pattern as shown in Figure 3), Each menu number is set for the number of increments n (the number of movement divisions in a half cycle of the swing pattern, which determines the frequency). In addition, in the case of equal leg length in horizontal fillets,
If you specially set hNo. ``3'', it will automatically become equal leg length.

(6) Switching position SE ₆ ...Has a pattern number display section,
It is possible to set with a key number how many times (N _T ) of the pattern the movement direction of the swing pattern itself is corrected (referred to as "rotation correction").

(7) Switching position SE ₇ ...Equipped with a timer display section, allowing the stop time at the left and right ends of the swing to be set using a menu number.

Now, as shown in Fig. 1, the workpiece W has a curved vertical member W2 temporarily attached to the upper surface of the elongated horizontal member W1, and the right-angled corner formed by these members W1 and W2 is attached to one end. It is assumed that continuous welding is performed from a welding start point _P2 , which is the position of the first teaching point, to a welding end point _P4 , which is the position of the second teaching point at the other end.

The teaching operation by the operator and the processing executed by the computer 10 in connection therewith will be explained below.

(T1) Select manual mode M by operating switch SM. Then, by operating the switch SW, the torch 4 is positioned at an arbitrary point _P1 close to the welding start point _P2 . Next, switch
Switch SE to switching position SE ₁ , set linear interpolation "L" by operating numeric keypad TK, and switch
If you operate STA, the computer 10 will change to point P ₁
The position information (X ₁ , Y ₁ , Z ₁ , θ ₁ and φ1) and linear interpolation “L” are taken in as a first step.

(T2) Position the torch 4 at the welding starting point _P2 in a posture suitable for welding by operating the switch SW.

Then, by operating the numeric keypad TK to set the arc sensing "As" while leaving the switching position of the changeover switch SE, and operating the switch STA, the computer 10 transfers the position information of point _P2 and the arc sensing "As" to the next step. Import as.

(T3) Move the torch 4 to any point within the coordinate quadrant surrounded by members W1 and W2 by operating the switch SW.
Position at P ₃ (referred to as dummy point).

Next, the changeover switch SE is set to the switching position SE ₁ ,
In SE ₃ and SE ₄ , set "As", "7", and "02" respectively by operating the numeric keypad TK. Among these, FNo. "7" is a dummy point designation,
AUX No. "02" specifies a horizontal fillet as the weld joint shape (see Figure 2). Further, at the switching position _SE5 of the changeover switch SE, the amplitude m, height h, pitch PC, and number of increments n constituting the swing pattern described above are set using four-digit menu values using the numeric keypad TK. After that, by operating the switch STA, the computer 10 will display the position information of dummy point _P3 , arc sensing "As", and F No.
"7", AUX No. "02", and the rocking pattern information are taken in as the next step.

(T4) Position the torch 4 at the welding end point _P4 in a posture suitable for welding by operating the switch SW.
Next, the switching positions of the changeover switch SE are set to SE ₁ , SE ₂ ,
"As", "01", "10", "3", "1" are selected by operating the numeric keypad TK on SE ₄ , SE ₆ , and SE ₇ , respectively.
Set. Among these, W No. "01" is a menu number that has optimal welding conditions (welding voltage, welding current, etc.) from welding start point _P2 to welding end point _P4 . Furthermore, AUX No. "10" means that the position is corrected using swing pattern data obtained in advance from another work. Further N _T
"3" means that rotation correction is performed every third time the pattern is completed. Timer "1" specifies a menu number suitable for temporarily stopping the welding torch 4 at the left and right ends of the swing. Now, if you operate Switch STA, computer 1
0 is position information of welding end point P ₄ , arc sensing "A3", W No. "01", AUX No. "10", N _T
Work on "3" and timer "1" as the next step.

(T5) By operating the switch SW, position the torch 4 at an arbitrary retreat point _P5 that can be moved linearly from the welding end point _P4 . Then, change the changeover switch SE to the changeover position SE ₁ , set linear interpolation "L" by operating the numeric keypad TK, and turn the switch
If you operate STA, the computer 10 will change to point _P5.
The last step is the position information and linear interpolation "L".

This concludes the teaching. FIG. 4 shows the contents of the aforementioned series of user programs.

Next, the operator puts the switch SM into test mode.
If you set it to TE and operate the switch STA, each step of the above program will be executed (but welding will not be executed), and if there is an error, it will be corrected.

Next, if the switch SM is set to auto mode A and the switch STA is operated, the aforementioned program will be executed continuously. The flow of processing executed by the computer 10 at this time will be explained with reference to the flowchart of FIG.

(A1) The computer 10 determines whether there is a command "As" in a step of the user program (processing PR1).

(A2) If there is no command "As", execute the contents of this step (processing PR2).

(A3) If there is a command "As" in the process PR1, it is further determined whether pattern creation is automatic setting (process PR3).

(A4) If the FNo. is "7", it is judged as automatic setting,
Create an arc weaving swing pattern from the amplitude m, height h, and pitch PC based on the information taught to dummy point _P3 (processing PR
4).

(A5) In process PR3, if the FNo. is not "7", it is judged as manual setting, and the explanation is omitted here.
The welding torch 4 is actually positioned on the groove and a swing pattern as taught is created (processing PR5).

(A6) Once each process is completed in either process PR4 or PR5, perform arcing and weaving with the created pattern, and correct the groove width direction using the detected amount at that time (hereinafter referred to as parallel correction). (Processing PR6).

(A7) Next, it is determined whether the pattern number N is the desired number N _T (processing PR7).

(A8) If N=N _T , further perform rotation correction based on the locus of the oscillation pattern executed so far, that is, the execution start point and end point of the oscillation pattern based on the pattern reference line so far. The extension direction of the line connecting them is determined as a new reference line, and rotational correction is applied to the swing pattern to correspond to the new reference line (processing PR8), and N=0 is set (processing PR9).

(A9) If N=N _T in process PR7, then N=N+1
(Processing PR10).

(A10) When the process PR9 or PR10 is finished, it is determined whether the arc sensor has finished (process PR11).

(A11) If the step has not ended yet, the process returns to step PR6, and if it has ended, it is determined whether the step has reached the end (process PR12).

(A12) If it is the end, the series of execution in auto mode ends, but if not, the step is updated (processing PR13) and the process PR
Return to the front of 1.

However, the welding robot RO uses computer 1.
The following operations are performed based on the command output from 0. First, the torch 4 is positioned at a point _P1 , and the torch 4 is moved toward the welding start point _P2 by linear interpolation. When torch 4 reaches point _P2 , it starts arc weaving and reaches the welding end point based on welding condition No. "01".
Perform horizontal fillet welds towards P ₄ . This will be explained in detail with reference to FIG. The computer 10 creates a swing pattern PT of an isosceles triangle whose base is the first pattern reference line _L1 connecting the welding start point _P2 and the welding end point _P4 as the first swing pattern (N=1). Create and output.

Therefore, the torch 4 moves from point P ₂ → P ₂₁ → P ₂₂ and reaches the point
Direction perpendicular to pattern reference line L ₁ from P ₂₂ (i.e.
vertical member W in the direction perpendicular to the pattern progress direction)
Move to point P ₂₃ approaching 2.

The second execution swing pattern starts from point P ₂₃ and is drawn as points P ₂₃ →P ₂₄ →P ₂₅ →P ₂₆ (where P ₂₅ →P ₂₆ is the positional deviation amount). Similarly, the third execution swing pattern starts from point P ₂₆ and moves from point P ₂₆ → P ₂₇
→P ₂₈ →P ₂₉ → (However, P→ ₂₈ →P ₂₉ is the amount of positional deviation)
It is depicted as When the torch 4 finishes the third arc weaving, the computer 10
is determined to be N=3 (=N _T ) in the process PR7, and in this embodiment, the line connecting point P ₂ and point P ₂₉ is defined as the second pattern reference line L ₂ , and this and the first pattern reference line are Rotation correction is also applied to the swing pattern using the angle Δδ ₁ formed with L ₁ . This Δδn (n=1, 2,
...) is called the rotation correction angle for convenience. Therefore, the fourth, fifth, and sixth swing patterns are executed using the second pattern reference line _L2 as a reference, and parallel correction is performed in the direction perpendicular to the reference line _L2 .

And the end point of the 6th arc weaving
When P ₃₈ is reached, the computer 10 again sets the line connecting point P ₂₉ and point P ₃₈ as the third pattern reference line L ₃ ,
The angle between this and the first pattern reference line L ₁ is Δδ ₂
In order to accommodate this, rotation correction is applied to the swing pattern.
In _this way, the execution oscillation pattern is subjected to parallel correction every time, rotation correction is applied every third time, and as long as the positional deviation based on the new pattern reference line is within the correction range, the actual welding line It is possible to accurately follow WL.

The torch 4 moves along the welding line WL while repeating the above-mentioned arc weaving, and when it reaches the welding end point _P4 , it ends the welding and moves to the retreat point _P5 by linear interpolation.

In addition to the embodiments described above, the present invention can also be modified as described below.

() In the above embodiment, the frequency of rotation correction was set to N _T = 3, but it may be set to an appropriate number depending on the shape of the welding line WL and the size and shape of the swing pattern. In extreme cases, N _T = It may be 1.

() In the above embodiment, the rotation correction angle Δδ _o is
Although shown on the Y coordinate plane, it may also be a three-dimensional three-dimensional angle.

() Robots can also be implemented with mechanical configurations other than rectangular coordinate systems.

As detailed above, the present invention provides the following unique and remarkable effects.

(b) While the swing pattern is being executed, the swing pattern is corrected in the form of parallel movement each time with a correction amount according to the detected amount of positional deviation of the welding torch, and the previous correction is performed every predetermined number of times in the swing pattern. In order to correspond to the amount, the pattern reference line (i.e., the direction of movement of the swing pattern) is changed (rotation correction) to perform rotation correction on the swing pattern, so the position of the first teaching point and the position of the second teaching point are By simply teaching the position, for example, the position of the welding start point and the position of the welding end point, the pattern will follow the arm curve of the welding line, even if the welding line is freely curved between the taught points. Since the reference line is sequentially changed and the swing pattern is executed based on the pattern reference line, and because the correction range is always based on the new pattern reference line, it is possible to follow the weld line well.

(b) As is clear from the reason (a) above, the position of the welding start point is determined as the position of the first teaching point and the position of the second teaching point even for a free-curved welding line on a workpiece with a complex shape. By simply teaching the position of the welding end point and the position of the welding end point, there is no need to teach the position of many intermediate points, making the teaching work easier.
The range of workpieces to which arc sensors can be applied has expanded dramatically.

(c) The reference line for the first pattern between both teaching points is the line that connects both teaching points, but this reference line is used as a reference line for the predetermined swing pattern in order to correspond to the amount of correction up to that point, as described in (a) above. Change for each number of times (rotation correction)
and the parallel correction of the swing pattern is always performed in the direction perpendicular to the new pattern reference line.
Since this correction direction approaches the direction perpendicular to the actual weld line, followability to the weld line is improved.

(d) Since the correction range is always based on a new pattern reference line, it is substantially wider than the conventional case where it is based on a fixed reference line. is applicable.

[Brief explanation of drawings]

Figures 1 to 6 show embodiments of the present invention, of which Figure 1 is an overall view of the welding robot used in the present invention, Figure 2 is a schematic diagram showing various weld joint shapes, and Figure 3 is a diagram showing the welding robot used in the present invention. 4 is a step diagram of the program, FIG. 5 is a flowchart, FIG. 6 is an explanatory diagram of the execution of the oscillating pattern, and FIG. 7 is an explanatory diagram of the conventional oscillating pattern. . In the figure, RO is a robot, 4 is a welding torch, and 10 is a welding torch.
is a computer, 11 is a remote control panel, and W is a workpiece.

Claims (1)

[Claims] 1. The positions of the first teaching point and the second teaching point are taught, and arc welding is performed while the welding torch is oscillated in the groove width direction according to a predetermined oscillation pattern. In a welding robot that detects a positional deviation of the welding torch during swinging and corrects this positional deviation, the welding torch follows the welding line between the two teaching points. The line connecting the two lines is defined as the first pattern reference line, and while the swing pattern is being executed from the first teaching point to the first pattern reference line as a reference, the swing is performed by a correction amount corresponding to the detected amount of positional deviation each time. A line that corrects the pattern in a direction perpendicular to the first pattern reference line and connects the execution start point and end point of the swing pattern based on the first pattern reference line when the swing pattern has completed a predetermined number of times. Find the extension direction as the second pattern reference line, and
Rotation correction is applied to the swing pattern by changing the pattern reference line to the second pattern reference line, and after that, while executing the swing pattern using the second pattern reference line as a reference, the positional deviation is corrected every time. The oscillation pattern is changed to a second one with a correction amount according to the detected amount.
correction in a direction perpendicular to the pattern reference line, and an extension direction of a line connecting the execution start point and end point of the swing pattern based on the second pattern reference line at the end of the predetermined number of swing patterns. The third
The rotational correction is performed on the swing pattern by changing the second pattern reference line to the third pattern reference line. A method for following a welding line in a welding robot, characterized in that arc welding is performed until a second teaching point is reached while sequentially changing a rotational pattern to perform rotational correction.