JPS60229116A - Follow-up method of circular arc welding line of welding robot - Google Patents

Abstract

PURPOSE:To simplify a teaching job and to improve the follow-up performance by turning an oscillation pattern on the circumference of a circle by an amount equal to a center angle defining a cycle pitch as a chord in an execution mode of said pattern when an arc sensor is applied to a circular arc welding line. CONSTITUTION:A welding robot RO sets a torch 4 at a point P1 based on a command given from a computer 10, and the torch 4 is shifted to a welding start point P2 with the linear interpolation. The arc weaving is started at the point P2, and the horizontal fillet weld is carried out toward the next target point P4 based on the prescribed welding conditions. The computer 10 performs consecutively the arc sensing during execution of welding to correct the position variance by the data stored previously. Then the computer 10 produces an oscillation pattern and delivers it. In other words, the oscillation pattern is moved in parallel to the open tip width direction successively by a correction amount, i.e., in the rectangular and height directions to a pattern reference line connecting points P2 and P4. Thus the torch 4 always follow up a welding line W.

Description

[Detailed Description of the Invention] The present invention performs arc welding while swinging the welding torch in the groove width direction, detects a positional deviation of the welding torch during this swinging, and corrects this positional deviation. The present invention relates to a welding robot in which a welding torch follows a welding line, and in particular to simplifying teaching when an arc sensor is applied to an arcuate welding line.

As a method for teaching the above-mentioned swing pattern, as proposed in Japanese Patent Application No. 59-43275 by the present applicant, a swing pattern creation means is provided by inputting numerical values, and at the time of teaching, visual observation is performed within the coordinate quadrant including the bevel. and a method of positioning a welding torch at an arbitrary point that is easy to position (referred to as a dummy point) and teaching a swing pattern while keeping the torch stationary;
As proposed in the patent application dated August 26th (title of invention: "Welding line tracking method in welding robot"), the electrode tip of the welding torch (welding point) is actually positioned near the groove,
There is a method of teaching both end points of a half period of a swing pattern. In either the former automatic setting or the latter manual setting, when a swing pattern is taught, the computer that controls the entire welding robot regards the virtual welding line (also called the pattern reference line) connecting the taught points as the welding line. Create a swing pattern. In addition, when the combiator performs an arc sensor, the direction in which correction is applied is perpendicular to the pattern reference line, and the amount of correction is made at the end of the swing at the tip of the welding torch (however, when correction is applied, the correction point at the end of the swing is ) is fixed within an angular range of Δδ to the left and right of the pattern reference line.

Conventionally, when welding a circular arc weld line using an arc sensor, a large number of points a, b, . . . were taught at approximately equal intervals on the circular arc weld line WLC as shown in FIG. now,
If arc welding is to be performed on a workpiece that is exactly the same as the workpiece used during teaching, the computer first selects the teaching point a.
-b is set as the pattern reference line l, and a swing pattern PTa on the first cycle day is created and executed with this as the base of the isosceles triangle. Therefore, the tip of the welding torch is @ −
+fi'→a#, and even when a# is reached, the workpiece Wa is not reached yet, so from then on, the reference line is moved as shown by aa-1a# until the workpiece Wa is reached! move in a direction perpendicular to.

Then, the computer creates and executes the swing pattern P T aa on the second cycle day starting from the current point a'.

In this example, since point a7 is within the range of the correctable angle Δδ with respect to the pattern reference line l centered on point a,
The tip of the torch was able to follow the arcuate welding line WLC, but if the interval between the teaching points was widened (the number of teaching points was reduced), the welding line would deviate from the range of angle Δδ and would no longer be able to follow the welding line WLC. In other words.

In the case of circular arc welding line WLc, increasing the number of teaching points improves followability, but teaching is complicated and takes time; conversely, reducing the number of teaching points makes teaching easier, but followability cannot be guaranteed. . This also applies to the radius of curvature of a circular arc.

Since an arc with a small radius of curvature has a large curvature, the welding line must be kept within the correctable angle △δ (the interval between teaching points must be narrowed. This not only increases the number of teaching points and makes teaching complicated, but also This would also exceed the limit of the robot's movement accuracy.Therefore, it can be seen that the application of arc sensors to circular arc weld lines is limited to those with a relatively large radius of curvature.

In view of the above-mentioned circumstances, the present invention includes means for creating a swing pattern for one circular arc weld line during teaching.

Teach at least three points: arc start point, arc middle point, and arc end point, and when creating a swing pattern, determine the equation of a circle from the three points, and use the equation to determine the pitch of one cycle of the swing pattern as a chord. The center angle is set, and each time the swing pattern is executed, the swing pattern is rotated on the circumference by an angle corresponding to the center angle, and is suitable for teaching work when applying an arc sensor to an arc weld line. The present invention aims to provide a method for following an arcuate welding line in a welding robot, which simplifies the process and improves the following performance.

Hereinafter, a detailed description will be given based on the embodiment shown in FIGS. 1 to 8.

1 represents the rectangular coordinates (X, Y
, Z) is an abandoned axis configured at the terminal of the robot RO (details not shown).

A first arm 2 is supported at the lower end of the vertical shaft 1 so as to be pivotable around the shaft 1 (arrow α).

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

And axis 1. The shaft 3a and the central axis 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. By controlling the rotation angle in the α and β directions, the attitude angle θ and the turning angle φ (so-called Euler angle) of the torch 4 with respect to the vertical axis IIζ are set to the point plJ.
! It can be fixed and controlled.

5 is a welding power supply device. The device 5 is equipped with a spool 7 that winds up the consumable electrode 6 of the torch 4, and although details are not shown, the electrode 6 can be drawn out by rotating a feed roller.
Furthermore, the structure is such that a welding power source 8 and a current sensor 9 can be connected in series between the electrode 6 and the workpiece W.

Reference numeral 10 denotes a known computer as a control device for the entire embodiment. Computer 1o includes a CPU and memory.

A power source 8 and a current sensor 9 are connected to the path line B of the computer 1o.

The pass line B is further connected to an 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 position information thereof. Similarly, pass line B has a Y-axis servo system sY configured in the same way.

Z-axis servo system Sz%β-axis servo system Sα and β-axis servo system Sβ are connected.

11 is a remote control panel, which includes 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 standby, and three types of modes (manual mode M, test Mode changeover switch SM for switching to mode TE and auto mode A).

Numeric keypad TK, condition setting changeover switch SE for setting various conditions at each switching position described below by operating the numeric keypad TK, and a start switch used to start operation in each mode or import teaching contents into memory. It is equipped with a switch STA, etc.

The changeover switch SE has six switching positions SE shown below.
, ~SE6.

(1) Switching position SE, . . . linear interpolation "L", living "W" 1 circular interpolation rcJ l linear arc sensing [AsJ.

Equipped with five display lamps for circular arc sensing [CAsJ], each corresponding to the key number "1" to "5" on the numeric keypad TK.
By pressing ``, each display lamp can be lit to make a selection.

(2) Switching position fltsE,... Welding condition number WNII
The memory of the computer 10 stores in advance a set of welding voltage E, welding current I, and welding speed Vw for each positive setting, and the key number on the numeric keypad TK corresponding to the desired set is selected. It can be called by pressing it.

(31 switching position SEs...) 1 link number FNa
In this embodiment, by operating the key number "7" on the numeric keypad TK, it is taught that the current position of the welding torch 4 is not the teaching point of the movement position but a dummy point.

(41 switching position SE4...correction method number AUXNll
In this embodiment, the key number r01J of the numeric keypad TK is displayed.

By pushing r02J and r03J, the respective values shown in Fig. 2 (
a).

As shown in (b) and (c), each weld joint shape can be selected: downward fillet, horizontal fillet, and groove groove.

Moreover, AUXNh rl OJ means that the position is corrected based on data of a swing pattern created in advance with another work.

(5) Switching position SE, . . . 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 each indicate the amplitude m of the swing pattern (the moving distance of the groove width).

Height h (as shown in Figure 2 (a), (b), and (e), for downward fillets and tapered grooves, it is the distance from the weld line to the swinging surface, and for horizontal fillets, it is the leg length. ), Pitch PC (3rd
As shown in the figure, each menu number is set for the number n of half cycles of the swing pattern (the number of movement divisions in the half cycle of the swing pattern, which determines the frequency). In addition, in the case of equal leg length in horizontal fillets, hNa
If you set it to l'-3J, it will automatically become equal leg length.

(6) Switching position SE6: It has a timer display section, and the stop time at the left and right ends of the percentage swing can be set using a menu number.

Now, as shown in Fig. 1, the workpiece W has two vertical plates W2 and W3 placed on the upper surface of the horizontal plate W1, spaced apart from each other on the left and right.
An arc-shaped vertical plate W4 is placed between the two plates W2 and W3, and these four plates W1 to W4 are temporarily attached together. Then, continuous welding is carried out along the welding line WL at the right angle corner formed by the horizontal plate W1 and each vertical plate W2φW3 and W4, from the welding start point P at one end to the welding end point P1 at the other end with an arc sensor. That is.

The manual mode M is selected by operating the switch SM (T1) following the operator's teaching operation and the processing executed by the computer 10 accordingly. Then, by operating the switch SW, the torch 4 is positioned at an arbitrary point P close to the welding start point Pt. Next, switch the selector switch SR to the switch position SF, , and press the numeric keypad T.
Set linear interpolation rLJ by operating K, and press switch ST.
When A is operated, the computer 10 obtains the position information of point P1 (X, , Y□.

Zl, θ1. and ψ1) and linear interpolation rLJ as the first step.

(T2) By operating the switch SW, the torch 4 is positioned at the welding starting point P in a posture suitable for welding.

Next, set the linear arc sensing "As" by operating the numeric keypad TK while leaving the switching position of the changeover switch SR as it is, and by operating the switch STA, the computer 10
takes in the position information of point P and the linear arc sensing "88" as the next step.

(T3) The torch 4 is moved to the plate material W1 by operating the switch SW.
・Position at any point P (referred to as dummy point) within the coordinate quadrant surrounded by W2 and the welding line wLlz: @.

Next, the switching position of the changeover switch SE @SEa, SE
At I+SR, set rAJ, r7J, and r02J, respectively, by operating the numeric keypad TK. Of these, FNa r7J is designated as a dummy, and AUX Arashi r0
2J is a horizontal fillet designation for a welded joint (see Figure 2).

Furthermore, at the switching position MSEI of the changeover switch SH, the amplitude m, height, pitch, 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 the dummy point P, the linear arc sensing "As", the F "7J", and the AUX 隘r02J.
, and the rocking pattern information as the next step.

(T4) By operating the switch SW, move the torch 4 to the plate material W.
2. Position P4 at the confluence of W4 (referred to as arc starting point) in a posture suitable for welding.

Next, the change-over switch SE is set to the switching position SE, , SR,
.

rcAsJ, rolJ, 11'OJ, rlJ by operating the numeric keypad TK in SE S&
Set. Among these, "CAs" means the start of circular arc sensing, and WNIlro IJ means the start of welding starting point P.
! Welding condition CI @ from to arc starting point P1 is the menu number 1 with the optimum conditions for welding voltage and welding current. Further, AUXNa rlOJ means that the position is corrected using data of a swing pattern obtained in advance from another work.

Furthermore, the timer "1" is the welding torch 4 at the left and right ends of the swing.
Specifies a menu number suitable for temporarily pausing. Now, if you operate switch STA, the computer 10 will display the position information of the arc starting point P4.

Arc sensing rcAsJ, WNci ro
1J, AUX Nurl OJ, timer “1
” as the next step.

(T5) Move the torch 4 to the welding line W by operating the switch SW.
It is positioned at the midpoint P5 of the arc of L in a posture suitable for welding.

Below, as in (T4) above, the position information of the arc midpoint P is obtained by operating the changeover switch SE, numeric keypad TK, and switch STA.1 Arc arc sensing [CAsJ,
Wyo r01J, AUX Arashi flop, timer "1"
” as the next step.

(T6) By operating the switch SW, move the torch 4 to the plate material W.
4. Confluence point of W3 (referred to as the arc end point) pm is positioned in a position suitable for welding, and as in (T4) above, position the arc end point P6 by operating the selector switch SE, numeric keypad TK, and switch STA. Information 9 arc arc sensing "CA s J, WNQro IJ, AU
X tooth rl OJ, timer "1" is taken in as the next step.

(T7) The torch 4 is positioned at the welding end point P in a posture suitable for welding by operating the switch SW. Next, the switching positions SL, SEa, SEa of the changeover switch SR
.

rAs by operating the numeric keypad TK in S&
Set J, rolJ, rlOJ, rlJ.

Now, if you operate switch STA, computer 10
Position information of soldering end point P, linear arc sensing 1
AsJ, WN [lro IJ, AUX Na
rl oJ , capture timer "1" as the next step.

(T8) By operating the switch SW, the torch 4 is positioned at any retreat QPs that can be linearly moved from the welding end point P. Then move the selector switch SR to the switch position SE.
1 and perform linear interpolation rLJ by operating the numeric keypad TK.
By setting , and operating the switch STA, the computer 10 takes in the position information of the point P and the linear interpolation rLJ as the final step.

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

Next, when the operator sets switch SMt to test mode TE and operates switch STA, each step of the above program is executed (but welding is not executed), and if there is an error, it is corrected. Next, switch SM is set to auto. So-
If the mode is set to A and the switch STA is operated, the above-mentioned 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 or not there is an arc sensor command during a step of the user program (
processing PRI).

(A2) If there is neither command rA8J nor rCA8J, the contents of this step are executed (processing PR2).

(A3) If the judgment of processing PRI is "YESJ, % Judge whether the straight arc sensor [AsJ or not. (Processing PR3).

(A4) [If AsJ, it is further determined whether pattern creation is automatic setting (processing PR4).

(A5) If FNh is "7", it is judged as automatic setting,
The amplitude m is based on the information taught to the dummy point Ps.
, height, and pitch PC, and execute the arc sensor at a speed (frequency) given by the number of steps n (processing PR5).

(A6) In process PR4, F? If 'h is not "7", it is considered to be a manual setting, and the explanation is omitted here, but we actually positioned the weld and chi 4 at the groove and created the oscillation pattern as taught. Execute the arc sensor (processing PR6).

(A7) If processing PR3 is not "A8", it is determined that the 1-arc arc sensor is "cAsJ", and further it is determined whether pattern creation is automatic setting (processing PR?).

(A8) If FNIl is "7", it is determined to be automatic setting, create a pattern in the same way as the above process PR5, find the equation of the circle from the three points: arc start point, arc middle point, and arc end point, and calculate this. The arc sensor is executed while rotating the pattern by a predetermined angle each time under the equation (processing PR8).

(A9) In processing PR7, if the F storm is not "7", manual setting is determined.

Under this equation, the arc sensor is executed while rotating the pattern by a predetermined angle each time (processing PR9).

(AIO) Said processing PR2, PH1, PH1, PH1
, PH1, when each process is completed, it is determined whether that step is the end (processing PRIO).

(All) If it is the end, the series of execution in auto-sword ends, but if not, the step is updated and the process PRII), the process P! Return to the front of 21.

The welding robot RO performs the following operations based on the command output from the computer 1°. First, the torch 4 is positioned at a point P, and the torch 4 is moved toward the welding start point P2 by linear interpolation. When torch 4 reaches point P, it starts arc weaving.

Horizontal fillet welding is performed toward the next target point P4 based on welding conditions WIlhr01J. and computer 10
performs arc sensing continuously during welding.

The positional deviation is corrected using the pre-stored data AUlhrlOJ, and then a swing pattern is created and output in the process PR5. That is, the swing pattern is moved in parallel in the groove width direction (strictly speaking, in the direction perpendicular to the pattern reference line connecting points P and P4) and in the height direction by the amount of the sequential correction, and the torch 4 is always moved in parallel. It follows the welding line WL.

Next, when the torch 4 reaches the arc starting point P4' whose position has been corrected by cumulative correction, the computer 1°
, ·, arc middle (teaching) point P, and arc end (teaching)
Find the equation of the circle from the three points, including point P6.

From this equation, the center position ffQ of the circle and the radius 6
Determine the inner arc center angle θ11 between the points p41 and Ps, and from these determine the center angle θ8 whose chord is the pitch of one period of the swing pattern (twice the PC mentioned above), and use this angle θ1 as the rotation per pattern. Let it be a corner. Then, the computer 10
Fluctuation pattern PT of periodic day.

For point P,', the central angle is 0. Point P on the arc of
1. A line connecting them is created as a pattern reference line L1 and an execution command is issued. Therefore, the torch 4 draws a swinging pattern PT starting from the point P, /, and if there is a positional deviation as a result of arc sensing, correction is applied in the direction perpendicular to the reference line Ll, and the point P,1 ′ is reached. Next, the computer 10 creates and executes a swing pattern PT for the second period based on a reference line obtained by rotating the reference line L1 by an angle θ1 using the current point P41' as a starting point (
(See Figures 6 and 7).

When the torch 4 reaches the intermediate point of the arc whose position has been corrected in this manner, the computer 10 determines this point P, the '1 arc start (teaching) point P, and the arc end (teaching) point P, as shown in FIG.
Teaching) Find a new equation of a circle from the three points P and , and from this calculate the center position Qw of the circle and the central angle θ of the arc between the radius and points P and P6. % Find the rotation angle θ per pattern in the same manner as above.

Then, as explained with reference to FIG. 7, the computer 10 rotates the pattern reference line by an angle θ every time one pattern is executed, sequentially creates swing patterns, and issues an execution command.

When the torch 4 reaches the arc end point P6' (not shown) whose position has been corrected by the arc sensor, the torch 4 reaches the point P, →
Welding is performed using a linear arc sensor in the same manner as at point P,', and when the welding end point P,' (not shown) is reached, welding is terminated and the welding is moved to the retreat point P by linear interpolation.

Through these continuous welding, the posture of the torch 4 is at point P2゜P.
Gradually convert to the posture taught with +, Pg, Pg, and Py.

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

(1) In the above embodiment, position correction by arc sensing is performed using previously created data (AUl&l rlOJ)
However, sampling data may be created at the initial stage of welding execution, and position correction may be performed based on the sampling data.

(II) In the above embodiment, when welding from the arc start point to the arc midpoint, the equation of the circle was determined from three points, P4', Ps, and Pa, but the position correction amount of points P, P4' is corrected parallel to the points Ps and Pg, and the obtained points p and I
You can also write the equation of a circle using I, p, l/ and p, I.

(1) In the above embodiment, when welding from the middle point of the arc to the end point of the arc, the equation of the circle was calculated from the three points P, , P,', p-, but the actual arc starting points p, I , and the points P,', P,', and P-, or the points P,' and P-', which are obtained by correcting the position correction amount of points P5, P,' in parallel to point P6, are memorized. The equation of the circle may be determined from the three points P, Z P, /.

(IV) In the above embodiment, we described welding an arc formed by one point P4, Ps, P, but a point very close to point P (of course, it may coincide with point P) is added. If you teach this method, you will be able to weld using a circular arc sensor.

(V) In the above-mentioned embodiment, the rotation angles θ□, θ were shown on the x-y coordinate plane, but they may also be three-dimensional three-dimensional angles.

(VI) Robots can also be implemented with mechanical configurations other than rectangular coordinates.

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

(B) Regardless of the size of the radius of curvature, even for arcuate welding lines, teaching work is simple because it is only necessary to teach three points: arc start point, arc middle point, and arc end point, and there is no need to teach many intermediate points. The arc sensor can now be applied to circular arcs with a small radius of curvature, which could not previously be applied.

(b) Of the three teaching points, the arc midpoint can be any point on the arc between the arc start point and the arc end point, so it is necessary to determine whether or not it falls within the correction range as in the past. There is no need to take this into account (conventionally, there is no need to worry about teaching work).

(c) The pattern reference line for the first pattern uses the pitch of one period pattern as a chord, and the subsequent reference lines are rotated and corrected to an angle corresponding to the center angle of this chord, and parallel correction by the arc sensor is always performed using a new reference line. Since the correction is performed in a direction perpendicular to the line and the direction of correction is approximately perpendicular to the actual weld line, followability of the weld line is improved.

(d) As is clear from the reason (c) above, in the case of the present invention, if there are no individual differences in workpieces or installation errors, the correction is zero, and unlike the conventional teaching, there is no error involved in teaching itself. Therefore, the correction range is substantially wider than in the past, and accordingly, the arc sensor can be applied even to workpieces with large individual differences.

[Brief explanation of the drawing]

Figures 1 to 8 show embodiments of the present invention, of which Figure 1 is an overall view of the welding robot of the present invention, Figure 2 is a schematic diagram showing various weld joint shapes, and Figure 3 is a swing pattern. Fig. 4 is a step diagram of the program, Fig. 5 is a flowchart, Figs. 6 to 8 are explanatory diagrams of execution of the swing pattern in the arc weld line, and Fig. 9 is the swing pattern in the conventional arc weld line. It is an explanatory diagram of pattern execution. In the figure, RO is a welding robot, 4 is a welding torch 10 is a computer, 11 is a remote control panel, and W is a workpiece. Applicant ShinMaywa Industries Co., Ltd.

Claims (1)

[Claims] (1) Arc welding is performed while the welding torch is oscillated in the groove width direction, the positional deviation of the welding torch is detected during the oscillation, and the welding torch is made to follow the welding line by correcting this positional deviation. The welding robot configured as described above includes a swing pattern creating means for an arc welding line, and when teaching, at least three points, an arc start point, an arc middle point, and an arc end point, are taught, and when the swing pattern is created, the above three points are taught. Determine the equation of a circle from the point, use the equation to determine the central angle with one period of the swing pattern as the chord, and each time the swing pattern is executed, move the swing pattern along the circumference of the circle to the center angle. A method for following an arcuate welding line in a welding robot, characterized by rotating the welding line by corresponding angles.