JPH0673752B2 - Control method for welding robot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling a welding robot, and particularly to weaving while making the welding torch follow a welding line by detecting and correcting a positional deviation of the welding torch by arc sensing. The present invention relates to a method of controlling a welding robot when performing welding.

(Prior Art and Its Problems) One example of a conventional control method for such a welding robot is described below.
Shown in the figure. FIG. 7 shows a cross section of a welded joint perpendicular to the welding line of the downward fillet.
A change in welding current is detected when the vibration is generated with a pre-teached amplitude, and a welding line is detected (so-called arc sensing) to perform copy welding. However, in this method, the consumable electrode 4 becomes the longest in the root portion 3, so that the welding current becomes the minimum, and therefore the root portion 3
As a result of the shallow penetration in the vicinity, the reliability of the welded joint was poor, and there was the problem that it was difficult to apply it to the first layer of important structural members. Also, unlike FIG. 7,
In the case of a weld in an upward position, the direction of power flow is different from the direction of penetration, and the penetration becomes even shallower, and it is practically impossible to apply arc sensing to such a weld.

(Object of the Invention) Therefore, an object of the present invention is to solve the problems of the above-described conventional technology, improve the penetration at the root portion, improve the reliability of the welded joint, and increase the posture to the upright, sideways, or upward position. It is to provide a control method for a welding robot that can apply the arc sensing of.

(Means for Achieving the Object) In order to achieve the above object, according to the present invention, when weaving welding is performed while the welding torch is made to follow the welding line by detecting and correcting the positional deviation of the welding torch by arc sensing. A portion where the welding line is sensed and a portion where the welding line is not sensed are provided in one cycle of the weaving pattern, and in the portion where the sensing is not performed, a space surrounded by the base material surface and a virtual surface formed by the sensing portion. The welding torch is weaved in accordance with a preset pattern.

That is, in the present invention, the welding torch is oscillated in the predetermined plane in the sensing area as in the conventional case, and the welding torch is brought closer to the base metal surface in accordance with the predetermined weaving pattern in the non-sensing area to perform arc welding. By doing so, a deep penetration is secured.

(Example) FIG. 1 is an overall schematic view of a (X, Y, Z) rectangular coordinate system welding robot RO adopted as a welding robot which is the background of the present invention.

A first arm 12 is supported on a vertical shaft 11 formed at the terminal of this welding robot RO (not shown in detail) so as to be rotatable around the outer shaft 11 (direction of arrow α). A second arm 13 is provided at the tip of the first arm 12 so as to be pivotable around the oblique shaft 13a (arrow β direction). A welding torch 14 (MIG welding torch in this embodiment) as an end effector is attached to the tip of the second arm 13.

The central axes M of the shaft 11, the shaft 13a, and the torch 14 intersect at a point P. Further torch
14 is set so that its welding operating point may coincide with the point P. In such a structure, the attitude angle θ and the turning angle ψ (so-called Euler angle) of the torch 14 with respect to the vertical axis 11 are controlled by controlling the rotation angles in the directions of the arrows α and β.
The point P is fixed and controllable.

The device 15 is a welding power supply device. This device 15 has a torch 14
It is equipped with a spool 17 on which the consumable electrode 16 of is wound up, and although not shown in detail, the feed roller can be rotated to feed out the electrode 16, and the welding power source 18 and the arc sensing between the electrode 16 and the work WK. The current sensor 19 for is connected in series.

A well-known computer as a control device for the entire embodiment
Reference numeral 20 includes a CPU and a memory, and a power supply 18 and a current sensor 19 are connected to a bus line B of the computer 20.

In addition to the bus line B, the robot RO X-axis servo system
SX is connected, 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 the same Y
Axis servo system SY, Z axis servo system SZ, α axis servo system S
The α and β axis servo systems Sβ are connected.

On the other hand, the remote control panel 21 includes a manually operated snap switch group SW for moving the torch 14 manually, a speed command rotary switch SV for commanding a speed other than during welding,
3 modes (manual mode M, test mode TE,
And the mode changeover switch SM for changing over to the automatic mode A), the numeric keypad TK, and the condition setting changeover switch SE for setting various conditions at each switching position described later by operating the numeric keypad TK, and the operation starts in each mode. It is equipped with a start switch STA, etc., which is used when the teaching contents are taken into the memory.

The changeover switch SE has the following six changeover positions SE ₁
~ Has SE ₆ .

(1) Switching position SE ₁ ... Four indicator lamps for linear interpolation “L”, weaving “W”, circle interpolation “C”, and arc sensing “As” are provided, and key numbers “1” to “4” of the numeric keypad TK, respectively. Each display lamp can be turned on and selected by pressing "".

(2) Switching position SE ₂ ... Has a display of welding condition number W No., and the welding voltage E, welding current I, and welding speed Vw are stored in advance in the memory of the computer 20 as a set for each No. By pressing the key number of the numeric keypad TK corresponding to the desired set, it can be called.

(3) Switching position SE ₃ ... The display section for the function number FNo. Is provided, and in the present embodiment, the current position of the welding torch 4 is not the teaching point of the moving position by operating the key number "7" of the ten key TK. Teaching that it is a dummy point.

(4) Switching position SE ₄ ... A correction method number AUX. No. is displayed, and in this embodiment, the key numbers “01” and “0” of the numeric keypad TK.
2 ”,“ 03 ”, and so on, as shown in FIG. 2 (a),
As shown in (b) and (c), each welded joint shape such as a downward fillet, a horizontal fillet, and a square groove is selected. AUX No. "99" means that deep-melting type arc sensing is executed.

(5) Switching position SE ₅ : A pattern display portion is provided, and in the present embodiment, the swing pattern is set by a 4-digit number. For example, at the 4th to 1st digits, the amplitude m of the swing pattern (movement distance in the groove width direction) and the height h (as shown in FIGS. 2 (a), (b), and (c)), respectively. It is the distance from the welding line to the oscillating surface in fillet and chamfer, and the leg length in horizontal fillet), pitch PC (the welding line extends in a half cycle of the oscillating pattern as shown in FIG. 3). The menu numbers are set for the number of movements in the direction) and the number of steps n (the frequency is determined by the number of movement divisions in a half cycle of the swing pattern). In the case of the equal leg length in the horizontal fillet, it is automatically set to be the equal leg length by specially setting hNo.

(6) Switching position SE ₆ ... A timer display is provided, and the stop time at the left and right ends of the swing can be set by the menu number.

On the other hand, in the work WK in this embodiment, as shown in FIG. 1, a vertical member W2 is temporarily attached to the upper surface of a horizontal member W1 in an L-shaped combination, and a horizontal member formed by these members W1 and W2. The fillet portion is a continuous welding wire from the welding start point P ₂ at one end to the welding end point P ₄ at the other end.

Next, the processing in the embodiment of the present invention will be described focusing on the part related to the features of the present invention. The first of these is teaching, which will be described with reference to FIG. 1 and FIG. 4 showing the steps of the program.

(1) First, the operator of this apparatus selects the manual mode M by operating the switch SM.
Then operate the switch SW to move the torch 14 to the welding start point.
Position at any point P ₁ near P ₂ (see Fig. 1).
Next, change the selector switch SE to the selector position SE ₁ and press the numeric keypad T
Set the linear supplementary opening "L" by operating K. When the switch STA is operated, the computer 20 obtains the position information of the point P _{1 and} the information of the linear interpolation “L” at step N in FIG.
Import as data related to o.1.

(2) Next, by operating the switch SW, the torch 14 is positioned at the welding start point P ₂ in a posture suitable for welding. Next, the arc switch "As" is set by operating the numeric keypad TK with the switching position of the selector switch SE unchanged, and the switch STA is set.
By operating, the computer 20 takes in the position information of the point P ₂ and the arc sensing “As” as the data related to step No. 2 in FIG.

(3) Operate the switch SW to move the torch 14 to the members W1, W
To position any point P ₃ in the coordinate quadrant surrounded by 2 (dummy point and referred). Next, changeover position of changeover switch SE
SE _1, SE _3, SE ₄ respectively by operating the ten key TK in "As", "7", and sets "02". Of these, F No.
"7" is the designation of the dummy point, and AUX No. "02" is the designation of the horizontal fillet as the weld joint shape (see Fig. 2). Further, at the switching position SE ₅ of the changeover switch SE, the numeric keypad TK is used to form the swing pattern described above with the amplitude m, height h, and pitch.
Set the PC and step number n with a 4-digit menu value. After that, if the switch STA is operated, the computer 20 causes the position information of the dummy point P ₃ , arc sensing “As”, FNo.
The information of "7", AUX No. "02", and the swing pattern are taken in as data for step No. 3 in FIG.

(4) End point of welding the torch 14 by operating the switch SW
Positioning in a posture suitable for welding to P _4. Next, at the switching positions SE ₁ , SE ₂ , SE ₄ , SE ₆ of the selector switch SE, the numeric keypad T
By operating K, "As", "01", "99",
Set "1". Among them, WNo. “01” is a menu number having optimum conditions as welding conditions (welding voltage, welding current, moving speed, etc.) from the welding start point P ₂ to the welding end point P ₄ . AUX No. “99” means that deep-melting type arc sensing is executed as described above. Further, the timer "1" designates a menu number suitable for temporarily stopping the welding torch 14 at the left and right ends of the swing. Now, if the switch STA is operated, the computer 20 will detect the position information of the point P ₄ , arc sensing “As”, WNo.
"01", AUXNO. "99", and timer "1" are taken in as data for step No. 4 in FIG.

(5) By operating the switch SW, the torch 14 is positioned at any retreat point P ₅ that can linearly move from the welding end point P ₄ . Then, the changeover switch SE is changed over to the changeover position SE ₁ , the linear interpolation “L” is set by the operation of the ten-key TK, and the switch STA is operated, so that the computer 20 becomes the point P ₅
Position information and linear interpolation “L” are set to the final step N in FIG.
Import as data on o.5. This is the end of teaching.

Next, the operation of this welding robot RO during reproduction will be described. First, set the mode changeover switch SM to the test mode TE and operate the switch STA.
Performs the same operation as that described later at the time of welding without welding. The operator monitors the operation and corrects any error in the data during teaching. Next, the torch 14 is newly positioned, the mode changeover switch SM is set to the auto mode A, and the switch STA is set.
To operate. The operation for the actual weaving welding starts from this point, but the subsequent processing is the fifth step.
This will be described with reference to the flowchart in the figure.

First, in process 101, it is determined whether or not the step (corresponding step in FIG. 4) is arc sensing “As”. Then, if it is not the arc sensing “As”, for example, if it is the linear interpolation “L” or the weaving “W”, the process moves to the process 102 and the content of the step is executed. On the other hand, in the case of arc sensing “As”, processing 103
In, it is determined whether or not it is deep-melting type arc sensing, that is, whether or not AUX No. = "99" is specified. When the AUX No. = “99” is not designated, the conventional arc sensing, that is, for example, as shown in FIG. 7 is executed in step 104. On the other hand, AUXN
When o. = “99” is specified, deep-melting-type arc sensing is executed in the process 104 and thereafter as follows.

That is, first, in process 105, the soft flag SF = 1 is set, and then in process 106, it is determined whether or not the soft flag SF = 0. Soft flag SF = 1 now
Therefore, the process moves to the process 107, and the welding current is taken in by the current sensor 19. Then, when the welding torch 14 swings for a predetermined distance (for example, a distance corresponding to "m" in FIG. 2), a stop signal is obtained, the judgment of the process 108 becomes "Yes", and the current acquisition ends. Subsequently, in step 109, a correction amount for following the welding line is calculated by the conventional arc sensing method based on the captured current value, and in the next step 110, the welding torch according to the correction amount is calculated. 14 position correction. Then the next processing 111
At step 112, the soft flag SF is set to 0. At step 112, it is determined whether the welding end point is reached or not. If it is not the welding end point, step 106 is returned to.

In the process 106, since the soft flag SF = 0 this time, the process moves to the process 113, and the weaving welding is performed according to the patterns preset by "m", "h", and "p" in FIGS. 2 and 3. At this time, the welding current is not taken in, that is, arc sensing is not performed. When the weaving of the predetermined portion of the preset weaving 1-cycle pattern is completed, the soft flag SF = 1 is set in the process 114, and then the process 112 is performed. As described above, while performing arc sensing only in a part of the one cycle pattern of weaving, deep-penetration type arc sensing is executed until it is determined in step 112 that the welding end point is reached.

When the above processes 102 and 104 are completed, or when the welding end point is determined in process 112, it is determined in process 115 whether or not it is the final step, and if it is the final step, a series of processes is completed, but not the final step. In this case, the step is updated in process 116, the process returns to process 101, and the above processes are repeated.

The locus of the torch 14 when the step data of FIG. 4 is applied to such a processing flow is shown in FIGS.
It is shown in the figure. In this case, the tip of the torch 14 first moves by linear interpolation from the point P ₁ to the point P ₂ according to the data of step No. 1 in FIG. When the torch 14 reaches the point P ₂ , the computer 20 outputs a command instructing the weaving pattern from the point P ₂ to the point P ₄ ,
As a result, the torch 14 starts the weaving welding according to the welding condition “01” and the timer “1”, and proceeds from the point P ₂ to the point P ₄ along the locus shown in the drawing. At this time, since arc sensing "As" and AUX No. "99" are specified, deep-melting type arc sensing is performed, and as described above, arc sensing is performed only in a part of the one-cycle weaving pattern. Arc welding is performed while following the welding line.

FIG. 6 is an enlarged view of the state, and FIG. 6 (b) is a view on arrow A of FIG. 6 (a). In the torch locus, the solid line means a part where arc sensing is performed, and the dotted line means a part where arc sensing is not performed. Dash-dotted line surface 22 is a virtual surface formed by a portion that performs arc sensing, and by performing arc sensing by swinging the torch 14 on this surface 22 to detect a welding line, copy welding similar to the conventional case is performed. be able to. On the other hand, in the space surrounded by the surface 22 and the base material surface (the members W1 and W2 in this case), the torch 14 is formed along the base material surface without performing arc sensing according to a preset pattern indicated by a dotted line. By weaving, it is possible to secure deep penetration even in the vicinity of the root part and also in the welded parts in the upright, sideways, and upward positions.

When the welding is completed up to the point P ₄ while performing deep-penetration type arc sensing in this way, the process moves to the point P ₅ by linear interpolation, and the series of welding processes is completed.

In the above embodiment, the weaving pattern for each cycle has a portion for performing arc sensing and a portion for not performing arc sensing. However, the portion for performing arc sensing may be provided once in a plurality of cycles.

(Effects of the Invention) As described above, according to the present invention, the penetration at the root portion is improved, the reliability of the welded joint is improved, and the arc sensing is applied to the vertical position, the horizontal position, the upward position, and the like. It is possible to realize a control method for a welding robot that can easily perform the above.

[Brief description of drawings]

FIG. 1 is an overall view of a welding robot which is the background of the present invention,
FIG. 2 is a schematic view showing various weld joint shapes, FIG. 3 is an explanatory view of a swing pattern, FIG. 4 is a step diagram of a program used in an embodiment of the present invention, and FIG. 5 is an implementation of the present invention. 6 is a flowchart showing the operation of the example, FIG. 6 is an explanatory diagram showing a torch locus, and FIG. 7 is an explanatory diagram of conventional arc sensing. RO: welding robot, 14: torch, 20: computer, 21: remote control panel, WK: work

Claims (1)

[Claims] 1. A method of controlling a welding robot in which weaving welding is performed while the welding torch is caused to follow a welding line by detecting and correcting a positional deviation of the welding torch by arc sensing. A portion for performing the sensing of the welding line and a portion for not performing the sensing are provided on the welding torch. A welding robot control method characterized by weaving according to a set pattern.