JPH0451266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for controlling a welding robot, and particularly to a method for controlling a welding robot to perform weaving welding.

(Description of Prior Art) One of the important functions of welding robots is weaving welding. As is well known, weaving welding is a welding method in which a welding torch is moved along the weld line while swinging in a direction substantially perpendicular to the weld line. In the conventional control method for making a welding robot perform such weaving welding, the welding robot's torch is generally set in advance by setting the swing width in the orthogonal direction, that is, the weaving amplitude, as a constant value in the computer. Welding was performed while the tip was oscillated at the constant weaving amplitude.

However, the workpieces to be welded (referred to as "objects to be welded" in this specification) are two workpieces to be welded together.
The two objects to be welded are respectively expressed as "first" and "second." ) are due to variations in cutting accuracy, bending accuracy, assembly accuracy due to bending and distortion of the material, and their accumulated errors, such as the butt interval and groove width between the first and second workpieces (in this specification). Let's collectively refer to these as the "mutual spacing" of the objects to be welded.
It is called. ) is often non-uniform in the weld line direction. Even if conventional control methods are applied to such objects to be welded by a welding robot, welding will be performed with a constant weaving amplitude that ignores the above-mentioned non-uniformity, and the welding may vary depending on the location. Welding quality deteriorates significantly due to excess or deficiency.

For this reason, conventionally, weaving welding of welded objects having uneven mutual spacing has had to rely on manual welding.

(Objective of the Invention) An object of the present invention is to solve the problems of the prior art described above, and to provide weaving that is accurate even when the mutual spacing between objects to be welded is uneven along the welding line direction. It is an object of the present invention to provide a control method for a welding robot capable of performing welding and thereby ensuring high quality welding accuracy.

(Means for Achieving the Object) In order to achieve the above object, in the welding robot control method according to the present invention, the contours defining the mutual spacing between the first and second objects to be welded along the welding line are arbitrarily set. The welding robot performs weaving while changing the weaving amplitude between the arc trajectories determined based on the data. I try to make it possible.

In other words, even if the mutual spacing between the objects to be welded is non-uniform, this non-uniformity is taken into account as a change in the locus of the multiple circular arc elements, and the weaving amplitude changes accordingly, resulting in welding with no excess or deficiency. As a result, high quality welding accuracy can be ensured.

(Example) FIG. 1 is an overall schematic diagram of an (X, Y, Z) rectangular coordinate system welding robot RO employed as a welding robot that forms the background of the present invention.

A vertical shaft 1 formed at the end of this welding robot RO (details not shown) supports a first arm 2 so as to be pivotable around the shaft 1 (in the direction of arrow α). Further, a second arm 3 is provided at the tip of the first arm 2 and is supported so as to be pivotable around an oblique shaft 3a (in the direction of arrow β). A welding torch 4 (an MIG welding torch in this embodiment) 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. Furthermore, the torch 4 is set so that its welding operating point can coincide with the point P. In such a configuration, by controlling the rotation angle in the directions of the arrows α and β, the attitude angle θ and the turning angle ψ (so-called Euler angle) of the torch 4 with respect to the vertical axis 1 can be controlled by fixing the point P. It's summery.

Device 5 is a welding power supply device. This device 5 is
Spool 6 that winds up the consumable electrode 4a of the torch 4
Although details are not shown, the electrode 4a can be drawn out by rotating a feed roller, and furthermore, a welding power source 5a can be connected between the electrode 4a and the workpiece WK. The device 5 also includes a detection power source 5b. The detection power source 5b is limited to a voltage of approximately 100 to 2000 V and a current limited to a small current, for example. An energization state detector 5c is connected in series to the detection power source 5b, and these and the power source 5a can be switched by a switching means 5d.

A known computer 7 as a control device for this entire embodiment includes a CPU and a memory,
A power supply 5 is connected to the bus line B of this computer 7.
A, a current sensor 5c and a switching means 5d are connected.

The bus line B is further connected to the robot RO's X-axis servo system SX.
includes an X-axis power MX and an encoder EX that outputs its position information. Similarly, bus line B is connected to a similarly configured Y-axis servo system.
SY, Z-axis servo system SZ, α-axis servo system Sα, and β-axis servo system S are connected.

On the other hand, the remote control panel 8 includes a group of manually operated snap switches for manually moving the torch 4.
SW, speed command rotary switch SV for commanding speeds other than welding, mode changeover switch SM for switching to three types of modes (manual mode M, test mode TE, and auto mode A), numeric keypad TK, numeric keypad TK Condition setting changeover switch SE, correction switch RE, to set various conditions at each switching position described later by operation of
It is also equipped with a start switch STA, which is used to start operations in each mode and to load teaching contents into memory.

The changeover switch SE has six changeover positions SE ₁ to SE ₆ shown below.

(1) Switching position SE ₁ ...Equipped with five display lamps: linear interpolation "L", circular interpolation "C", weaving "W", circular element weaving "CW", and sensing "S", each with a key number on the numeric keypad TK By pressing "1" to "5", each display lamp can be turned on to make a selection.

(2) Switching position SE ₂ ...has a display section for the welding condition number WNo., and the welding voltage E, welding current I, and welding speed are stored in the memory of the computer 7 for each number in advance.
VW is stored as a set, and the set 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 sensor menu number SEMNo., and the memory of the computer 7 stores each
Work WK with electrode 4a of torch 4 itself for each No.
The subroutines necessary to sense the welding line are stored as a set, and the numeric keypad
It can be called at any time by operating TK.

(4) Switching position SE ₄ ...has a display section for the correction method number AUXNo. In this embodiment, the weaving amplitude can be made variable by pressing key number "99" of the numeric keypad TK.

(5) Switching position SE ₅ ...has a 1-pitch information display section,
The distance to travel in the circumferential direction with one swing can be set using a menu number.

(6) Switching position SE ₆ ...Equipped with a timer display section so that the stopping time at the left and right ends of the swing can be set using a menu number.

On the other hand, the workpiece WK in this embodiment, as shown in FIG. 1, consists of a plate 9 as a first object to be welded and a shaft 10 as a second object to be welded. A groove 11 is formed in the plate 9, and a shaft 10 is formed in the boss portion 9a.
The annular downward groove is weaved and welded. However, as shown in an exaggerated manner in FIG. 2, the groove width is non-uniform for some reason, and the outer and inner circles, which are the contours of the groove width, are not concentric circles.

Next, the processing in the embodiment of the present invention will be explained, focusing on the parts related to the features of the present invention. The first process is teaching, which will be explained with reference to FIG. 1, FIG. 2 showing the positional relationship of teaching points, etc., and FIG. 3 showing the steps of the program.

(1) First, the operator of this device must operate the switch.
Select manual mode M by operating SM. Then, operate the switch SW to move the torch 4 to the welding starting point P ₂ (see Figure 2).
Position at an arbitrary point P ₁ close to . Next, change the changeover switch SE to the changeover position SE ₁ , and set the linear interpolation "L" by operating the numeric keypad TK. Then, by operating the switch STA, the computer 7 will receive the position information of point _P1 and the linear interpolation "L".
This information is taken in as data related to step No. 1 in FIG.

(2) Next, by operating the switch SW, position the torch 4 at the welding start point _P2 on the outer circle in a posture suitable for welding. Then, by operating the changeover switch SE and numeric keypad TK, select arc weaving "CW", welding condition "01", correction method "99",
Select 1 pitch information "1" and timer "1". Among these, arc weaving "CW"
The setting means the start of weaving along an arc by circular interpolation, and "01" indicates the welding condition.
is a menu number set corresponding to the optimal welding conditions (welding voltage, welding current, welding speed) for the weaving. Further, by setting the correction method "99", it means that it has been taught that the subsequent weaving welding will be performed in the amplitude variable mode. Furthermore, 1-pitch information "1" is a menu number that sets the optimal value of the distance p that the welding torch 4 should travel in the circumferential direction with one swing of the weaving, and the timer "1" is a menu number that sets the optimal value of the distance p that the welding torch 4 should travel in the circumferential direction with one swing of the weaving. The menu number of the time suitable for temporarily stopping the welding torch 4 is specified. And if you operate Switch STA,
The computer 7 takes in the position information of the welding start point _P2 and the above information as data regarding step No. 2 in FIG.

(3) Select point _P3 as the position on the inner circle corresponding to the welding start point _P2 on the outer circle, and position the torch 4 here by operating the switch SW. Then operate the selector switch SE and numeric keypad TK,
Select arc weaving "CW" and correction method "99". Next, when the switch STA is operated, the computer 7 takes in the position information of point _P3 as data regarding step No. 3. At this time, the computer 7 transfers the position information of point P ₃ regarding this step No. 3 to the step No. 2.
It is taken in as a pair with the position information of point P ₂ regarding the point P2. That is, in this embodiment, "CW", which specifies circular arc weaving with variable amplitude,
Whenever "99" is set, the continuously set points on the outer circle and the points on the inner circle are taken into the computer 7 as a pair of position information.

(4) Position the torch 4 at a point P ₄ on the original outer circle in a posture suitable for welding by operating the switch SW. And selector switch SE and numeric keypad
Operate TK to select arc weaving "CW" and correction method "99", then turn the switch.
Operate STA to import the position information of point _P4 , arc weaving "CW", and correction method "99" as data regarding step No. 4. At this time, if you want to change the welding conditions, weaving pitch, or timer after point _P4 due to circumstances such as a change in the thickness of the workpiece after point _P4 , set these menu numbers at the same time. do. If there are no new settings, the same conditions (i.e. welding conditions set in step No. 2 "01", 1 pitch information "1", timer "1")
treated as a continuation of

(5) Select point _P5 as the position on the inner circle corresponding to point _P4 on the outer circle, and position the torch 4 here by operating the switch SW. Then, select the arc weaving "CW" and the correction method "99" by operating the changeover switch SE and numeric keypad TK, and then operate the switch STA to import the position information of point P5 as data regarding step No. ₅ . Now, the settings for "CW" and "99" that specify variable amplitude circular arc weaving have been made, so as above, point P ₅ regarding step No. 5 has been made.
The location information is point P ₄ related to step No. 4 above.
The information is taken into the computer 7 as a pair with the position information.

(6) For data input for steps No. 6 to No. 9 shown in Figure 3, set arc weaving "CW" and correction method "99" in the same way as data input for steps No. 2 to No. 5 above. Then, perform the outer circle and inner circle alternately in the order of P ₆ → P ₇ → P ₈ → P ₉ . At this time, if it is desired to change the welding conditions, weaving pitch, or timer midway, these menu settings should be made at the same time as teaching point _P6 or point _P8 .

(7) Point P ₁₀ corresponding to step No. 10 and No. 11 and
P ₁₁ is the end point of welding. In this case, since we want to weave the entire circle, the end points P ₁₀ and P ₁₁ need to be approximately aligned with the start points P ₂ and P ₃ . That is, first, operate the switch SW to move the torch 4 to the starting point on the outer circle.
Position at the same end point P ₁₀ as P ₂ . Then operate switch SE and numeric keypad TK to select arc weaving "CW" and correction method "99", then operate switch STA to select position information of point _P10 , arc weave "CW",
and correction method "99" are taken in as data regarding step No. 10. Next, operate the switch SW to position the torch 4 at the same end point _P11 as the starting point _P3 on the inner circle. Then, select the arc weaving "CW" and the correction method "99" by operating the changeover switch SW and the numeric keypad TK, and then operate the switch STA to import the position information of point _P11 as data regarding step No. 11. In this case, "CW" and "99" are set to specify variable amplitude circular arc weaving, so the end points P ₁₀ and P ₁₁ on the outer circle and inner circle in step Nos. 10 and 11 above are set. The location information is 1
The data is taken into the computer 7 as a pair.

(8) By scanning the switch SW, position the torch 4 at an arbitrary retreat point _P12 that can be moved linearly from the welding end point _P10 . Then, change the changeover switch SE to the changeover position SE ₁ , set the linear interpolation "L" by operating the numeric keypad TK, and then operate the switch STA.
The position information of _P12 and the linear interpolation "L" are taken in as data regarding the last step No.12.

The basic teaching operation is completed above, but if you want to perform so-called sensing as well, before inputting the data for the points P ₁ to _{P 12} above, set a number of appropriate points on the boss 9 and axis 10. Select them and use them as sensing points.
The location information and sensing mode of that point are taught. In this case, as will be described later, the actual welding is started after correcting the position data of the points P ₂ to _{P 11} based on the data obtained by the sensing for each object to be welded.

Next, the operation of this welding robot RO during regeneration will be explained. First, mode selector switch SM
When set to test mode TE and operating switch STA, welding robot RO performs the same operation as that during welding, which will be described later, without welding. The operator monitors the operation and corrects any errors in the data during teaching. Next, the torch 4 is newly positioned, the mode changeover switch SM is set to auto mode A, and the switch STA is operated. At this point, the actual weaving welding operation begins, and the subsequent processing will be explained with reference to the flowchart of FIG. 4.

First, in process 101, the step (third
(corresponding step in the figure) is arc weaving “CW”
It is determined whether Then, if the arc weaving is not "CW", the process moves to process 102,
It is determined whether the sensing is "S".
Although sensing "S" is not included in each step in FIG. 3, sensing data may be included as described above, and in that case, the process moves to process 103 in the sensing step. Sensin is performed, and then in processing 104,
The position data of points P ₂ to _{P 11} at the time of teaching is corrected based on the data obtained by the sensing. This sensing is done with torch 4 and work
By switching the switching means 5d so that the detection power source 5b and the current sensor 5c are connected between the detection power source 5b and the current sensor 5c, sensing can be performed using the electrode 4a. This sensing correction is effective for correcting individual differences in objects to be welded, individual installation errors, and the like. If the determination in process 102 is something other than sensing "S", such as linear interpolation "L" or circular interpolation "C", then in process 105 the contents of the relevant step are executed.

On the other hand, if the determination in process 101 is arc weaving "CW", it is determined in the next process 106 whether or not the arc weaving is amplitude variable. This judgment is based on the correction method (AUX, No.)
This can be done depending on whether "99" is given as data in the step. If the amplitude is not variable, in the next process 107, weaving welding of the circular arc portion is performed using a preset constant weaving amplitude. On the other hand, when the amplitude is variable, the process moves from process 106 to process 108, and the mutual spacing along the welding line of the first and second objects to be welded (in this example, by the outer circle and inner circle in FIG. 2) is determined. Weaving welding of the circular arc portion is performed while changing the weaving amplitude according to changes in the specified groove width. And the above processing
When 104, 105, 107 or 108 is completed, process 109
It is determined whether or not it is the final step at
If it is the final step, the series of processing will be completed, but
If it is not the final step, the step is updated in process 110, and the process returns to process 101 to repeat the above process.

The trajectory F of the tip of the torch 4 when the step data of FIG. 3 is applied to such a processing flow is shown by a dotted line in FIG. In this case, the tip of the torch 4 should first be placed at step No. 3 in Fig. 3.
It moves from point P ₁ to point P ₂ according to the data of point P 1 by linear interpolation. When the torch 4 reaches _P2 , the computer 7 outputs a command instructing the weaving pattern from point _P2 to point _P4 , and as a result, the torch 4 sets the welding condition to "01" and the timer to "1". Weaving welding is started according to the procedure, and progresses from point _P2 to point _P4 along the dotted line shown in the figure.

The weaving pattern starting from point P ₂ and ending at point P ₄ is based on the position information of points P ₂ to P ₇ and 1
It is created as follows based on pitch information "1". In other words, the arc portion along the outer circle of the circle uniquely determined by the three points P ₂ , P ₄ , and P ₆
Find the locus of P ₂ P ₄ and find the arc part along the inner circle by the circle uniquely determined by the other three points P ₃ , P ₅ , P ₇
Find the trajectory of P ₃ P ₅ . Next, divide the arc P ₂ P ₄ by pitch p represented by 1 pitch information “1”,
If it is not divisible, select a pitch as close as possible to the pitch p and divide the arc P ₂ P ₄ into equal parts. and an arc corresponding to approximately the midpoint of each of these dividing points
If you find each point on P ₃ P ₅ and connect each of those points to the above dividing points in order, you will get something like the dotted line in Figure 2.
A weaving pattern starting from point _P2 and ending at point _P4 is obtained.

Next, when the torch 4 reaches point P ₄ , the computer 7 outputs a command instructing the weaving pattern from point P ₄ to point P ₆ , and as a result, the torch 4 continues to operate under the welding condition "01" and the timer. According to "1", weaving welding is proceeded from point P ₄ to point P ₆ along the dotted line shown in the figure. The weaving pattern from point P ₄ to point P ₆ is created based on the position information of points P ₂ to P ₇ and the 1-pitch information “1” in the same way as described above.

When the torch 4 reaches point P ₆ , the computer 7 outputs the next weaving pattern, that is, the weaving pattern from point P ₆ to point P ₈ .
Position information and 1 pitch information for points P ₄ to P ₉ “1”
based on the same method as described above. That is, in this embodiment, except for the starting points P ₂ and P ₃ , the trajectory of the arc is determined by referring to the points before and after the starting points P 2 and P 3. In this case, the trajectory of the arc is obtained by referring to the points before and after the starting points P ₆ and the points P ₄ and P ₈ before and after the starting points. Find the locus of arc P ₆ P ₈ with reference to
The locus of the arc P ₇ P ₉ is also determined by referring to the point P ₇ and the points P ₅ and P ₉ before and after it. Then, the torch 4 advances weaving welding from point P ₆ to point P ₈ according to the welding condition "01" and the timer "1" along the weaving pattern indicated by the dotted line in the figure created in this way. The same applies to the range from point _P8 to point _P10 .

In this way, the tip of the torch 4 performs weaving pattern welding on each arc portion while sequentially changing the amplitude in _{FIG .} Move and complete a series of welding processes.

In addition to the embodiments described above, the present invention can also be modified in various ways, such as those described below.

() In the above embodiment, welding was performed by teaching a full circle as the contour defining the mutual spacing along the welding line of the welded object, but in the present invention, any circular arc shape can be taught and welded. For example, if the contour defining the mutual spacing along the weld line of the object to be welded is a circular arc portion as shown in FIG. 5, a pair of welding start points P ₂ , P ₃ and a pair of welding end points P ₆ , _P7
In addition, by teaching at least one pair of intermediate points P ₄ and P ₅ , the locus of the arcs P ₂ P ₄ and P 4 P ₆ can be determined from the position information of P ₂ , P ₄ , and _{P 6 ,} and the points
Circular arc P ₃ P ₅ , P ₅ P ₇ based on the position information of P ₃ , P ₅ , P ₇
Since the trajectory can be determined, the present invention can be applied to perform variable amplitude arc weaving welding.

() By expanding the idea in () above, the present invention can be applied even when the contours defining the mutual spacing along the welding line of the objects to be welded have an arbitrary shape. For example, in the case of a contour shape as shown in Fig. 6, this contour is divided into an appropriate number (6 in Fig. 6).
A pair of welding start points P ₂ , P ₃ and a pair of welding end points P ₈ , P are the minimum positional information required to determine the trajectory of these arc elements. In addition to ₉ , the two pairs of midpoints P ₄ and P ₅
Also, teach P ₆ and P ₇ . The trajectories of arcs P ₂ P ₄ , P ₄ P ₆ are determined from the position information of points P ₂ , P ₄ , P ₆ , and the trajectories of arcs P ₃ P ₅ , P ₅ P ₇ are determined from points P ₃ , P ₅ , Determine from the location information of P ₇ . Furthermore, the locus of the arc P ₆ P ₈ is determined from the position information of the points P ₄ , P ₆ , P ₈ , and the locus of the arcs P ₇ and P ₉ is determined from the position information of the points P ₅ , P ₇ , P ₉
Determined from location information. In Figure 6, it is divided into three arc parts (the number of arc elements is six), but if you divide this into more arc parts and teach, you can perform more precise amplitude variable arc weaving welding. Of course, it is possible to do so.

Furthermore, for example, even if the contour that defines the mutual spacing along the weld line of the welded object has a shape as shown in FIG. 7, this contour is regarded as two arc elements (one arc portion). , a pair of welding start points P ₂ , P ₃ and a pair of welding end points P ₆ ,
If you teach a pair of intermediate points P ₄ and P ₅ in addition to P ₇ , the trajectories of arcs P ₂ P ₄ and P ₄ P ₆ will be the points P ₂ ,
Determined from the position information of P ₄ , P ₆ , arc P ₃ P ₅ ,
Since the locus of P ₅ P ₇ can be determined from the positional information of points P ₃ , P ₅ , and P ₇ , the present invention can be applied to perform amplitude variable arc weaving welding.

() In the above embodiment, the downward groove is welded by variable amplitude arc weaving, but the present invention can be applied to other weld joint shapes. For example, in the case of a horizontal fillet as shown in FIG. 8, the inner circle may be taught at a higher position than the outer circle.

() The information for determining the trajectory of the arc element is
It is not necessarily necessary to provide settings based on specific positioning of the torch 4. For example, several patterns of circular arc loci or patterns of circular arc portions consisting of a pair of circular arcs may be prepared in advance and selected and input using a menu method. In this case, for example, when inputting teaching data regarding welding start points P ₂ and P ₃ and welding end points P ₁₀ and P ₁₁ , such data may also be input. In short, it is sufficient that information on the welding start and end points and information on the locus of the arc element between them are provided by some means. Further, even in the case where the information on the circular locus is provided by specific positioning of the torch 4 as in the above embodiment, it is not necessarily necessary to provide the position information for each point one pair at a time. The way it is given depends on the arc trajectory recognition algorithm and the weaving pattern formation algorithm; for example, if information is added to distinguish between points on the inner circle and points on the outer circle. , it is no longer necessary to teach points on the inner circle and points on the outer circle alternately as in the above embodiment.

(Effects of the Invention) As explained above, according to the welding robot control method according to the present invention, even when the mutual spacing between a pair of objects to be welded is uneven along the welding line direction, , the contour forming the mutual spacing is analyzed into a trajectory of arbitrary plural arc elements, a weaving pattern is formed by this, and welding is performed while changing the weaving amplitude according to this pattern, so that the welding body can be It has become possible to perform weaving welding with just the right spacing, and it has become possible to achieve extremely high quality welding accuracy through automation.

[Brief explanation of the drawing]

Fig. 1 is an overall view of a welding robot which is the background of an embodiment of the present invention, Fig. 2 is a diagram showing how to take a teaching point and the trajectory of a torch in an embodiment of this invention, and Fig. 3 is a diagram showing the trajectory of a torch in an embodiment of this invention. FIG. 4 is a flowchart showing the operation of the embodiment of the present invention, and FIGS. 5 to 8 are diagrams showing data input modes related to modified examples of the present invention. . RO...Welding robot, 4...Torch, 7...Computer, 8...Remote control panel, WK...Work.

Claims (1)

[Claims] 1 A method for controlling a welding robot for weaving welding a first and a second object to be welded along a welding line, the method comprising controlling the mutual spacing between the first and second objects to be welded along the welding line. The defined contour is divided into a plurality of arbitrary arc elements, data for determining the trajectory of the arc elements is given in advance before welding, and the weaving amplitude is changed between the arc trajectories determined based on the data. A method for controlling a welding robot, characterized in that the welding robot is caused to perform weaving welding while the welding robot is weaving.