JP2686839B2 - Industrial robot system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial robot system, and more particularly to an industrial robot system suitable for application to an arc welding robot that performs end-seeding welding of structures.

Conventional technology Maki welding is the 10th method to make an inverted T-shaped joint.
As shown in the figure, both sides of the lower end portion of the reinforcing member 2 standing upright on the upper surface of the base 1 are simultaneously fillet welded by the welding torches 3 and 4, and the welding bead 5 that has advanced from both sides at the end of the joint. This is a welding method for forming a weld bead 5 of the same quality metallurgically and without interruption by combining the beads 5 in a molten state.

FIG. 11 shows the arm tip of a conventional arc welding robot for performing this type of welding. In FIG. 11, 11 and 12 are welding torches, and 13 and 14 are welding torches 11 and 1, respectively.
It is a holder of 2. A head 15 supports the torch holders 13 and 14, and the torch holders 13 and 14 are structured to be movable in the torch holder direction in this portion.

The end of the work is predetermined in the feed mechanism, or the operator judges it and operates the holders 13 and 14 by the head 15 to move the two welding torches 11 and 12 by the required amount. Bring them closer together and fuse both fillets into one.

However, the conventional robot of this type is a one-head two-torch type in which two torches are mechanically fixed to one head, and arc welding is performed due to its geometric shape. The possible work is obviously limited. That is, the reinforcing member 2 shown in FIG. 10 has two torches 11,12.
Must be cured during the welding, and welding is not possible even when there is an object above the reinforcing material 2.

The present invention solves such conventional problems, and provides an industrial robot system capable of synchronizing operations at distant positions and expanding the range of applicable works. The purpose is to do.

Means for Solving the Problems In order to achieve the above object, the present invention causes a plurality of robots to hold a tool and a sensor, respectively, constantly monitors the operation of each robot, and synchronizes the operation of each robot, Each robot detects the end of the welding line of the work with a sensor, absorbs the error due to the distortion during the welding work of the work, and realizes the welding by accurately determining the end of the welding line. .

Action Since the robots are separate, there is almost no limit to the work object, and the range of applicable work is expanded. When automatically performing the sprinkling welding, the two robots are operated in synchronism, and at the end of the welding line, both fillets are fused by metallurgically by melting the molten metal before it cools. A homogeneous weld bead can be formed.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an arc welding robot system according to an embodiment of the present invention. In Fig. 1, 2
1 and 22 are arc welding robots, and 23 and 24 are auxiliary external axes (additional axes) that move the robot. The arc welding robots 21 and 22 and auxiliary external axes 23 and 24 are controlled simultaneously by the same controller. To be done. As such a simultaneous control robot system, for example, Panarobo AW-7000 is known. Two
5 and 26 are arc welding torches and arc welding robots 2
It is fixed to the tip of arm 1,22. 27 and 28 are pedestals, which are used for adjusting the working height of the work and the robot.

These two robots 21 and 22 are arranged to face each other with a certain space 29 left therebetween, and the work is carried into the space 29.

Next, the operation of the torches 25 and 26 in the fired welding using this robot system will be described with reference to FIG. FIG. 2 is a plan view of the inverted T-shaped joint shown in FIG. 10 as seen from above, and will be described using the same reference numerals. The welding lines of the two torches overlap in the sense that a homogeneous bead is formed metallurgically at the point P on the end surface of the reinforcing material 2, and the reinforcing material 2 is separated from both sides of the reinforcing material 2 from there. And fillet the boundary of base 1 with the fillet. At the end of the reinforcing material 2, the welding line changes its traveling direction and is overlapped at the point Q on the other end surface of the reinforcing material 2. The overlapping means that the arc welding start point P
Similar to the point, it means that a metallurgically seamless bead is formed, and therefore the weld lines on both sides of the reinforcing member 2 must reach the point Q while the metal is melting.

By the way, in general, a work that requires sprinkling welding is relatively large, and therefore the work is deformed by being subjected to thermal strain during arc welding.Therefore, a correct weld bead is not formed even if the robot is moved as taught. Not exclusively. Two things are needed to get the correct weld bead.
One is to follow a welding line that changes from moment to moment. This is a known welding line tracking technique called seam tracking, which is realized by a visual sensor or an arc sensor. The other is to detect the end of the work. It will be described below that the sensor for detecting the end may be the same as the sensor used for seam tracking.

FIG. 3 is an enlarged view of the arm tip portion of the arc welding robot 21 in this embodiment. The other arc welding robot
22 has a similar structure. In FIG. 3, reference numeral 31 is an arm tip. 32 is a wrist, to which the welding torch 25 is attached by a torch holder 33. At the same time, a visual sensor 34 is attached to the torch holder 33. Usually, the visual field center axis 35 of the visual sensor 34 is separated from the arc generation point 36 by several centimeters in the direction perpendicular to the paper surface. This is to prevent the arc light from directly entering the image area of the visual sensor 34 because the arc light is so intense that the surrounding shape cannot be captured by the light. Therefore, in order to secure the visual field of the visual sensor 34 with respect to an arbitrary welding advancing direction, the welding torch 25 and the visual sensor 34 need to operate independently, but the description of the mechanism is essential to the present invention. Since it is not a matter, it is omitted here.

The visual sensor 34 together with the welding torch 25 is a torch holder.
Since it is attached to the 33, it moves following the fillet formation by the welding torch 25 and performs seam tracking.
Thus, the visual sensor 34 can detect the welding line when moving on the side of the reinforcing material, but cannot detect the welding line at the position where the reinforcing material is gone. Therefore, the visual sensor 34 recognizes it as the end of the work and detects the end. Of course, there is a problem with the margin for noise, so it is necessary to combine judgments a plurality of times when detecting the end.

FIG. 4 shows a method of detecting the end of the work by using an arc sensor instead of the visual sensor 34. The arc sensor itself is known, and the positional relationship between the work and the torch is determined by the change in the arc length. FIG. 4 (A) shows a state in which fillet welding is performed, and the welding torch 25 swinging between the positions R and S has a balanced arc length because of the reinforcing material 2, that is, the balance. It has a good welding current. On the other hand, at the end of the welding line, since there is no reinforcing material 2, as shown in FIG. 4 (B), the arc length is clearly different between the swinging end positions R and S of the welding torch 25, and the arc current is extremely unbalanced. Is obtained, and the difference from FIG. 4 (A) becomes clear. Therefore, the end of the welding line can be detected. However, it is clear that the visual sensor is more preferable than the arc sensor because it can perform both the tracking of the welding line and the end detection.

FIG. 5 shows a control block diagram of the entire robot system of this embodiment. Although FIG. 5 illustrates the configuration of two robots, which is the minimum required for the fired welding, the same applies to the configuration of three or more robots. Each robot individual control device 51, 52 controls a robot arm 53, 54 and a moving axis (additional axis) 55, 56, respectively. There is a FA personal computer 57 to control the entire robot system, and communication lines 58, 5
9 is connected to each robot individual control device 51, 52.

The exchange between the FA personal computer 57 and the robot individual control devices 51, 52 will be described. First, a latch command for position data is given from the FA personal computer 57 to the robot individual control devices 51, 52. When receiving this, the robot individual control devices 51, 5
2 temporarily stores the robot's position at that time. The reason for doing this is to minimize the positional deviation caused by the time lag due to the long procedure for communication, and
This is because we want to accurately compare the positions of the robots.

Next, from the FA personal computer 57 to the robot individual control devices 51, 52
A position data transmission request is instructed to, and the individual robot control devices 51, 52 return the temporarily stored position data of the robot. If the FA PC 57 determines that there is a difference in position between the two robots as a result of processing the position data,
The individual robot controllers 51 and 52 are instructed to slightly increase or decrease the moving speed. Due to the change in the speed, the two robots can reduce the difference in position, and the welding can be similarly advanced. That is, as described in FIG. 2, in order for the two robots to reach the end almost at the same time,
This is because each welding line needs to proceed in the same manner.
"Similarly" in this case does not mean strictly the same speed. For example, considering the case where the reinforcing member 2 in FIG. 2 is bent in the horizontal plane, it is obvious that the lengths of the inner and outer welding lines are different, so that both robots start at the same time and proceed at the same speed. This is because, if they arrive at the end at different times, it is not possible to realize the spatter welding.

FIG. 6 shows the position of the torch of each robot at a certain time when the fillets on both sides of the curved reinforcing member 2 are simultaneously welded, as seen from above. Reference numeral 2 is a reinforcing member curved in a horizontal plane, and 25 and 26 are arc welding torches. p (n), q (n) represents the position by the latest latch instruction, and p (n-1), q (n-1) represents the position by the previous latch instruction. FIG. 7 shows a new one in which only the positional relationship is taken out. The FA personal computer 57 calculates two angles from the data of these positions. One is a vector from p (n-1) to p (n), and
Angle α formed by the vector from (n) to q (n)
(N), and the other is an angle β (n) formed by a vector from q (n-1) to q (n) and a vector from q (n) to p (n). The angles are compared with the ends, and the state of the ends is shown in FIG.

In FIG. 8, p (e-1) is the end point, and p (e-2) going from there to p (e) to change the direction and stack the weld beads is the point just before the end point. , P (e +
1) is a fictitious point obtained when a vector from p (e-2) to p (e-1) is added to the point of p (e-1). Similarly, q (e-1) is the end, from which it turns to q (e) to stack the weld bead. q (e-2) is the point immediately before the end, and q (e +
1) is a fictitious point obtained when a vector from q (e-2) to q (e-1) is added to the point of q (e-1). Similar to FIG. 7, the angles α (e) and β (e) are obtained. If α (n) is larger than α (e), p (n) is ahead of q (n), so
The robot controller 51 in the figure is instructed to slightly reduce the moving speed. Since the speed variable width is very small, if the speed cannot be reduced any further, the robot controller 52
Order to move to. Same thing β
The same is done for (n) and β (e). Thus, the two robots uniformly approach the end shown in FIG.

Now that it has been realized that the two robots move in the same way, the movement of the torch at the terminal end, which is at a position different from the taught position due to thermal strain during welding, will be described below. FIG. 9 shows the method. When the torch toward the robot arm 53 passes p (e-2), it moves toward a fictitious point p (e + 1) farther from the end, and at the same time, the end detection is started. It is assumed that the end is detected at p (c). If the end is detected, the movement so far is interrupted, and the vector moving from p (e-1) to p (e) is moved to the position added to p (c). The same is done for the robot arm 54, so that each robot arrives at p (c), q (c) almost at the same time and moves in a direction facing each other from there, so even if the workpiece is distorted by heat, the correct termination is achieved. It is possible to realize fired welding.

In this way, by using the FA personal computer 57 that controls the whole and the visual sensor 34 for seam tracking, and controlling the individual robot individual control devices 51 and 52, it becomes possible to perform the welding.

Effects of the Invention As is clear from the above embodiments, according to the present invention,
Since a plurality of robots each hold a tool and a sensor, and the operation of each robot is constantly monitored and controlled so that the operation of each robot is synchronized, there is almost no limit to the work target and the range of applicable work is limited. Can be expanded.

In addition, the two arc welding robots can follow the welding line of the work by the sensor and can accurately detect the end of the welding line by absorbing the error due to the distortion during the welding work of the work. Can be welded to achieve high quality fired welding.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an arc welding robot system showing an embodiment of the present invention, and FIG. 2 is a work object.
FIG. 3 is a plan view showing an example, FIG. 3 is an enlarged view of a robot arm tip portion in one embodiment of the present invention, FIG. 4 is an explanatory view showing an end detection method by an arc sensor, and FIG. (B) is an explanatory view when there is no place to be welded, FIG. 5 is a control block diagram of the entire system in one embodiment of the present invention, and FIG. Explanatory diagram showing the positional relationship during welding of the robot, FIG. 7 is a relative advance of two robots at a certain moment,
Explanatory diagram for checking the delay, Fig. 8 shows 2 at the end of the work
FIG. 9 is an explanatory view showing a position where the robot should be, FIG. 9 is an explanatory view showing a procedure of end-spot welding of a work distorted by thermal strain, and FIG. 10 is a perspective view showing an example of a work object on which the spar welding is performed. FIG. 11 and FIG. 11 are schematic perspective views of the arm tip of a robot for performing conventional welding. 1 ... Base, 2 ... Reinforcement material, 21, 22 ... Arc welding robot, 23, 24 ... Auxiliary external axis (additional axis), 25, 26 ... Welding torch, 27, 28 ... Stand, 29 ... … Work loading space, 3
1 …… Robot arm tip, 32 …… Wrist, 33 …… Torch holder, 34 …… Visual sensor, 35 …… Field center axis,
36 …… Arc point, 51,52 …… Individual robot controller, 53,54 …… Robot arm, 55,56 …… Movement axis (additional axis), 57 …… FA PC, 58,59 …… Communication line .

Claims (1)

(57) [Claims] 1. A plurality of robots capable of gripping a tool and a sensor at the tip of a robot arm and moving by one or more additional axes, a robot individual control device for individually controlling the plurality of robots, and a plurality of the plurality of robots. And a system controller connected to the robot, wherein the robot is two arc welding robots arranged facing each other for arc welding two or more welding lines of a work object at the same time. The sensor grasped by the arm of the robot detects the positional error of each welding line of the work object and the distortion of the work object that occurs during arc welding, and the shape change of the work object that is taught in advance The end points of the welding line of the work object are detected, and the robot individual control devices dynamically correct the detected errors and distortions, and the end points of the welding are detected. If so, it has an execution interruption forced jump function of interrupting the work and forcibly shifting to a predetermined procedure, and the system control device periodically reads and compares the positions of the two robots. In this way, the progress of the work of each robot is judged to be fast and slow, and the progress of the two robots in time series is managed by instructing each robot individual control device to make a minute increase or decrease of the work speed. An industrial robot system.