JPH0353071B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention performs arc welding while swinging the welding torch in the groove width direction of the workpiece, and detects the positional shift of the welding torch during this swing. In a welding robot that makes the welding torch follow the welding line by correcting this positional deviation, it is determined whether the current point has reached a position that satisfies a predetermined target point arrival judgment condition while the arc sensor is running. The present invention relates to a control device.

(Prior Art) Conventionally, in the above-mentioned welding robot, the integrated value of the moving distance of the welding torch has been used exclusively as a method for determining that the welding torch has arrived at the target point. That is, the moving distance of one pattern in the welding line direction is accumulated from the starting point of the arc sensor for each pattern of arc sensor execution, and the accumulated distance S is calculated from the starting point during teaching to the target point such as the ending point or intermediate teaching point. The welding torch determines that it has arrived at the target point when it is equal to or exceeds this distance D for the first time, and if the target point is the arc sensor end point, it ends arc welding and returns to the target point. If it is an intermediate teaching point, arc welding is continued toward the next chart point after clearing the cumulative distance S.

(Problems to be Solved by the Invention) When a swing pattern is taught to the welding robot described above, the computer that controls the entire welding robot uses a virtual welding line (also called a pattern reference line) connecting the taught points as a welding line. and create a swing pattern. However, actual welding lines are not necessarily straight lines, and if you closely observe them, you will find that they are bent or curved midway through, and are oriented in various directions.In general, the flow of an actual welding line is longer than the length of an imaginary welding line. It tends to be longer. Therefore, in the case of the target arrival determination method described above, the longer the virtual welding line becomes, the more the cumulative distance of the actual welding line will be much longer than the length of the virtual welding line, and the arc sensor end point will be closer to the actual target point. The position will be shifted. Furthermore, in the case of a workpiece such as a thin plate, it is expected that the entire workpiece will curve due to thermal strain during arc welding, and this thermal strain will also have a large effect on the positional deviation between the arc sensor end point and the target point. As a result, an unwelded part remains near the target point, and a good weld finish cannot be expected.
In addition, if the target point is an intermediate point, the point with a large positional deviation becomes the arc sensor starting point for the next target point, so if this positional deviation exceeds the maximum correction amount of the arc sensor, the welding torch will no longer work. It becomes impossible to follow the weld line.

(Means for Solving the Problems) The present invention provides means for storing a plurality of arrival determination method menus in which arrival determination conditions for a target point are set, selection means for selecting one of the menus at the time of teaching, and an arc The apparatus is characterized in that it includes an arrival determination means that calls the selection menu each time the swing pattern is executed during welding and determines whether the current point of the welding torch has arrived at a position that satisfies the arrival determination condition.

(Function) During teaching, the operator can check the material of the workpiece,
By selecting and teaching the arrival judgment method menu suitable for each welding line according to the size, welding location, welding line length, and welding conditions, the welding torch will be positioned at the actual target point when welding is performed. Stop the arc sensor at a nearby point.

(Example) Hereinafter, a detailed description will be given based on the embodiments shown in the drawings.

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.

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). 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.

Further, the torch 4 is set so as to coincide with the welding operating point P thereof. Thus, by controlling the rotation angle in the α and β directions, 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 while fixing the point P.

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 the details are not shown, the electrode 6 can be drawn out by rotating a feed roller, and a welding power source 8 is connected between the electrode 6 and the work W. and current sensor 9 can be connected in series.

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 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 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, 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, and three types of modes (manual mode M, test mode). Mode selector switch SM for switching to TE and auto mode A), numeric keypad TK, condition setting selector switch SE for setting various conditions at each switching position described below 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 four display lamps for linear interpolation "L", weaving "W", circular interpolation "C", and arc sensing "As", each with key numbers "1" to " of the numeric keypad TK" By pressing ``4'', each display lamp can be lit to make a selection.

(2) Switching position SE ₂ ...Has a display section for the welding condition number W.No., and the number is stored in the memory of the computer 10 in advance.
The welding voltage E, welding current I, and welding speed Vw are stored as a set for each 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 function number F.No. display section, and in this embodiment, by operating the key number "7" of the numeric keypad TK, the current position of the welding torch 4 is set to the teaching point of the movement position. It is taught that it is a dummy point instead of a dummy point.

(4) Switching position SE ₄ ...has a display section for the correction method number AUX.No. In this embodiment, by pressing the key numbers "01", "02", and "03" of the numeric keypad TK, the respective As shown in Figure 2 a, b, c, downward fillets,
Each weld joint shape can be selected: horizontal fillet or rectangular groove. Also, AUX.No. “10” is
This means that the position is corrected based on data of a swing pattern created in advance for 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 (movement distance in the groove width direction) of the swing pattern, and the height h (downward fillet and re-shaped opening as shown in Figure 2 a, b, and c). For the first part, it is the distance from the welding line to the swinging surface, and for the horizontal fillet, it is the leg length), pitch PC (the distance traveled in the direction in which the welding line extends during a half cycle of the swinging pattern, as shown in Figure 3) , the number of increments n (the number of movement divisions in a half cycle of the swing pattern, which determines the frequency), and each menu number is set. In addition, in the case of equal leg length in horizontal fillets,
If you specially set h.No. ``3'', it will automatically become equal leg length.

(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.

(7) Switching position SE ₇ ...Arrival determination method number AJM.No.
The present point of the torch 4 is set for each number in the memory of the computer 10 as a menu storage means of the arrival determination method, as will be described later. System programs for various types of calculations necessary to determine whether or not the object is true are stored as menus, and one of these menus can be selected during teaching by operating the numeric keypad TK. This switching position SE ₇
together with the numeric keypad TK constitutes a menu selection means based on the arrival determination method.

Next, the arrival determination method based on each AJM.No. will be explained. Arrival determination methods are mainly divided into four types. For convenience, the types of arrival determination methods shown in Fig. 4 are referred to as type 1 and type 2, respectively.
They are called species, 3rd species, and 4th species. In addition, in the following explanation, from the starting point a to the target point b (end point or intermediate point)
Assuming that the arc sensor is executed toward d, the cumulative distance that the welding torch 4 has actually moved from point a to current point c (this is obtained by integrating the movement distance in the welding line direction of the pattern (=2 x PC) for each swing pattern execution ) is S.
In FIG. 4, the dotted line between points a and bh is called a virtual welding line L ₁ , and the solid line between points a and c is called an actual welding line L ₂ .

(1) Type 1 arrival determination method (Figure 4, AJM.No.=
10), when a' is a point obtained by moving the starting point a in parallel by the error amount Δδ with respect to the virtual welding line _L1 of the current point c, and d' is the straight-line distance between this point a' and the current point c, The arrival determination condition is d'>D. This determination method is applied when individual differences in workpieces and mounting errors are expected, but the target point is fixed.

(2) Type 2 arrival determination method (Figure 4, AJM.No.=
20), the arrival determination condition is d>D. This judgment method is applied when there is no risk of individual differences in workpieces or thermal distortion, but installation errors are expected.

(3) Type 3 arrival determination method (Figure 4, AJM.No.=
30) is a predetermined range K including target point b.
AJM.No. = 30 to 39 are set as a table, and the arrival determination condition is that "the current point c is within a predetermined range K." This determination method is applied when individual differences in workpieces are expected and the target point is approximately fixed. However, in Figure 4, range K
is defined as the range of a "sphere" centered on target point b.

(4) Type 4 arrival determination method (Figure 4, AJM.No.=
40) is as explained in "Prior art",
The arrival determination condition is S>D. This determination method is applied to workpieces where there are no individual differences between the workpieces and where deformation due to installation errors and thermal strain is expected.

Now, as shown in Fig. 1, the workpiece W has two vertical members W2 and W3 on the upper surface of the horizontal member W1.
The right-angled corner formed by these members W1, W2, and W3 is connected from the welding start point _P2 at one end to the midpoint _P4 where members W2 and W3 intersect, and then to the other end. Continuous welding is to be performed up to the welding end point _P5 . Further, the horizontal member W1 and the vertical member W2 are thin plates and are susceptible to thermal strain, and the vertical member W3 is a thick plate and is less affected by thermal strain.

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 ψ ₁ ) and the 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 unchanged, and by operating the switch STA, the computer 10 transfers the arc sensing "As" of the position information of point _P2 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, F.No. "7" is a dummy point designation,
AUX.No. "02" specifies a horizontal fillet as the weld joint shape (see Figure 2). Furthermore, at the switching position _SE5 of the changeover switch SE, the amplitude m, height h, pitch PC, and number of increments n constituting the above-mentioned swing pattern 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", 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 intermediate point _P4 in a posture suitable for welding by operating the switch SW.

Next, the switching position SE ₁ of the changeover switch SE,
"As", "01", "1", and "10" are displayed by operating the numeric keypad TK on SE ₂ , SE ₄ , SE ₆ , and SE _7, respectively.
Set.

Among them, W.No. "01" is the welding start point P ₂
This is a menu number with the optimal welding conditions (welding voltage, welding current, etc.) from P4 to intermediate point _P4 . AUX.No. ``10'' means that the position is corrected using swing pattern data obtained in advance from another work. Timer No. "1" specifies a menu number suitable for temporarily stopping the welding torch 4 at the left and right ends of the swing. Also
EJM.No. "10" is the designation of the above-mentioned type 1 arrival determination method. Thin plate members W1 and W2 may be deformed due to thermal strain during welding, but thick plate W1 and W2
Since the intermediate point P ₄ located at the confluence with P 3 can be considered fixed, the arrival determination of the intermediate point P ₄ requires the first
Apply the seed arrival determination method.

Now, if you operate the switch STA, the computer 10 will receive the position information of intermediate point _P4 , arc sensing "As", W.No. "01", AUX.No. "10",
Import timer No. ``1'' and AJM.No. ``10'' as the next step.

(T5) Position the torch 4 at the welding end point _P5 in a posture suitable for welding by operating the switch SW.
Next, the switching positions SE ₁ , SE ₂ ,
"As", "01", "10", "1", "20" are displayed on SE ₄ , SE ₆ , and SE ₇ by operating the numeric keypad TK, respectively.
Set. Among these, AJM.No. "20" is the designation of the aforementioned type 2 arrival determination method. Part W3
is a thick plate with no individual differences and a constant overall length, and only installation errors are expected, so the type 2 arrival determination method is applied to determine the arrival of the welding end point _P5 .

Now, by operating the switch STA, the computer 10 will receive the position information of welding end point _P5 , arc sensing "As", W.No. "01", AUX.No.
Import “10”, timer No. “1”, and AJM.No. “20” as the next step.

(T6) By operating the switch SW, the torch 4 is positioned at an arbitrary retreat point P ₆ that can be moved linearly from the welding end point P ₅ . 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 _P6
The position information and linear interpolation "L" are taken in as the final step.

This concludes the teaching. FIG. 5 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 shown in 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 F.No. is "7", it is determined to be automatic setting,
Based on the information taught to dummy point _P3 , create an arc weaving swing pattern from the amplitude m, height h, pitch PC, and the number of increments n.
The arc sensor is executed at the speed (frequency) given by (processing PR4).

(A5) In process PR4, if the F.No. is not "7", it is judged as manual judgment, and the explanation is omitted here.
The welding torch 4 is actually positioned at the groove and the arc sensor is operated in the oscillation pattern as taught (processing PR5). Note that this process PR5 is not applied in this embodiment.

(A6) When each process is completed in any of the processes PR2, PR4, and PR5, it is determined whether the step is the end or not (process PR6).

(A7) If it is the end, the series of execution in the auto mode is ended, but if not, the step is updated (processing PR7) and the process returns to the previous step PR1.

Next, the flow of processing in the arc sensor execution mode in the aforementioned processing PR4 or PR5 will be explained.

(A100) Clear the cumulative distance S as an initial state (processing PR100).

(A101) Calculate and store the distance D between the teaching starting point a and the target point b (processing PR10
1).

(A102) One pattern of arc sensor created in the process PR4 or PR5 is executed (process PR102).

(A103) One pattern of moving distance (=
2PC) (processing PR103) (A104) Determine whether the arrival determination method number AJM.No. is "10" (processing PR104).

(A105) If “YES”, the distance between point a′, which is obtained by moving the starting point a in parallel by the current error amount, and the current point c.
d' is determined (processing PR105), and then it is determined whether d'>D (processing PR106).

(A106) If the determination in process PR104 is "NO", it is determined whether AJM.No. is "20" (process PR107).

(A107) If “YES”, start point a and current point c
The distance d between the two points is determined (processing PR108), and it is then determined whether d>D (processing PR109).

(A108) If the determination in processing PR107 is "NO", it is determined whether AJM.No. is in the "30s" (processing PR110).

(A109) If “YES”, calculate the range K from the range setting conditions set for AJM.No. and the target point b (processing PR111), and then judge whether the current point c is within the range K. (Processing PR11
2).

(A110) If the judgment of process PR110 is "NO," AJM.No.=40 is assumed, and it is immediately judged whether S>D (process PR113).

(A111) Processing PR106, PR109, PR112,
If the judgment is "NO" in any of PR113, it is assumed that the current point c has not yet reached the target point b, and the processes PR101 and PR102
Go back to the period and if the decision is ``YES'' again,
It is assumed that the current point c has reached the target point b, and the process moves between the processes PR4 and PR6.

The welding robot RO performs the following operations based on the command output from the computer 10. In Fig. 7, the torch 4 is first positioned at point _P1 , and the torch 4 is moved to the welding starting point by linear interpolation.
Move towards _P2 . When the torch 4 reaches the point _P2 , it starts arc weakening according to the process PR4, and performs horizontal fillet welding toward the intermediate point _P4 based on welding condition No. "01". The computer 10 constantly performs arc sensing during welding, and uses pre-stored data.
After correcting the positional deviation using AUX.No. "10", create and output the swing pattern. That is, the swing pattern is translated in parallel in the groove width direction and height direction by the amount of correction each time, and the torch 4 always follows the welding line. When the swing pattern is executed each time and the position is corrected by the arc sensor, the current point of the torch 4 becomes the arrival determination point each time. Therefore, the computer 10 processes
In PR105, according to AJM.No.=10, whether or not the current point has arrived at the intermediate point _P4 is calculated and determined as described above. If the determination result of the process PR106 is "NO", the process moves to execution of the next swing pattern.

If the judgment result of the process PR106 becomes "YES" while arc weaving is progressing in this way, the welding torch 4 moves from the current point P ₄ ' to the intermediate point P ₄
It is assumed that the intermediate point _P4 has been reached even if it does not match. And the pattern reference line is the current point
It is changed to a line connecting P ₄ ' and welding end point P ₅ and is also changed to AJM.No. 20, and the torch 4 continues the arc sensor for horizontal fillet welding toward welding end point P ₅ .

The welding torch 4 executes the arc sensor toward the welding end point _P5 , and performs AJM.No.20 in processing PR108 and 109 every time the swing pattern is completed.
When the determination result of process 109 becomes "YES", it is assumed that the welding end point _P5 has been reached even if the current point _P5 ' does not match the welding end point _P5 , Finish welding and move to evacuation point P ₆ by linear interpolation.

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

() In the above embodiment, position correction by arc sensing is performed using previously created data (AUX.No.
10)), however, sampling data may be created at the beginning of welding execution and position correction may be performed based on it.

() In the above-mentioned embodiment, the distances and ranges used in each arrival determination method are shown in a two-dimensional plane in FIG. 4, but they may also be three-dimensional. for example,
In the type 3 arrival determination method shown in FIG. 4, the range K is a "sphere" centered on the target point b, but it may also be a cylindrical space that is perpendicular to the pattern reference line _L1 and passes through the target point b.

() As a method other than the above-mentioned types 1 to 4 arrival determination methods, a method using the central angle ω of a circle as a determination condition as shown in FIG. 8 can be considered. That is, this method has a circular or arc welding line, and the starting point a,
It is guaranteed that only the central angle ω determined by the center Q and the end point b is constant, and it can be applied to workpieces where individual differences (errors in circle size and arc shape) and installation errors are expected.

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

(Effects of the Invention) According to the present invention, a means for storing a menu of various arrival determination methods is provided, so that an operator can determine the material, size, etc. of a workpiece during teaching.
By simply teaching the arrival judgment method menu suitable for each welding line according to the welding conditions, even if the amount of correction by the arc sensor becomes large due to thermal distortion that occurs during welding, the target point can be set according to the welding location of the workpiece. It has many unique and remarkable effects, such as making it possible to determine the arrival of the weld and improving the welding finish.

[Brief explanation of drawings]

All drawings show embodiments of the present invention.
Fig. 1 is an overall view of a welding robot equipped with the control device of the present invention, Fig. 2 is a schematic diagram showing various weld joint shapes, Fig. 3 is an explanatory diagram of swing patterns, and Fig. 4 is an illustration of various arrival determination methods. Figure 5 is a step diagram of the program, Figure 6 is a flowchart, Figure 7 is an explanatory diagram.
The figure is an explanatory diagram of the operation, and FIG. 8 is an explanatory diagram showing an example of another arrival determination method. 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 includes a swing pattern creation means, performs arc welding while swinging the welding torch in the groove width direction,
In a welding robot that detects the positional deviation of the welding torch during the oscillation and corrects this positional deviation to make the welding torch follow the welding line, multiple arrival judgments are performed in which arrival judgment conditions for the target point are set. means for storing a method menu; selection means for selecting one of the menus during teaching; and calling the selection menu each time the swing pattern is executed during arc welding so that the current point of the welding torch satisfies the arrival determination condition. 1. A control device for a welding robot, comprising: arrival determining means for determining whether or not a position has been reached.