JP2652444B2 - Robot system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a system robot for working a large workpiece in parallel with a plurality of robots, and more particularly to a system robot for arc welding requiring a continuous trajectory. It is about.

(Prior Art) An arc welding robot operates by a method called teaching playback. This is a method in which the robot is taught the position and order in which it should operate, and the robot repeatedly executes the teaching contents. This method is effective for work with high precision of the work to be processed.

However, if the accuracy of the work is not stable, it is necessary to correct the robot teaching position each time. If a sensor is used as a countermeasure, the operation by the operator can be eliminated and the operation can be automated.

There are two position correction methods using sensors. One is a direct correction method in which correction is performed while obtaining the positional shift amount by a sensor sequentially during welding, and the other is a coordinate conversion type correction method in which a positional shift is obtained prior to welding. The latter coordinate conversion type correction method uses a specific three-dimensional rotation or translation when the work is three-dimensionally rotated or translated in a Cartesian system (three-dimensional rectangular coordinate system), meaning that the work does not depend on any axis.
This is a method of checking the positions of two points and correcting all the teaching points.
One point in space, the direction of the tool if it is a machine tool,
If the direction of the torch is given if it is an arc welding robot, articulated robot arms 5a and 5b of 5 axes or 6 axes
The correction value of each axis is determined.

Such conventional coordinate transformation type correction is performed within the range of one articulated robot arm.

(Problems to be Solved by the Invention) However, in the above configuration, when welding a large work, in order to improve the work speed, in a system in which a method in which a plurality of robots work in parallel is used, Are often provided with an additional external shaft for carrying the articulated robot arm in addition to the articulated robot arm. This increases the working range per unit,
The present invention facilitates the operation procedure of the robot, prevents the number of robots in the entire system from increasing unnecessarily, and improves cost performance.

However, when using a plurality of robots having external axes as described above and correcting the positional displacement of a large work to be covered by the coordinate transformation type, the robot having the external axes naturally has dimensions larger than six axes. However, there is a problem that the Cartesian system has a maximum of six dimensions in consideration of the tool gripping direction and cannot be equivalently converted to each other. In addition, there is a problem that while a plurality of robots are each responsible for a part of a work, correction has to be performed on the entire work.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a robot system that can easily perform position correction.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes an articulated robot arm working in cooperation with the same work, and an additional external axis for moving the robot arm body, and A plurality of robots having a work tool and a sensor at the end of the robot arm body, and data of reference points detected by the sensors of the plurality of robots are aggregated, and the aggregated data is collectively referred to as an overall robot arm body. A control computer for organizing and dividing the data into a position correction data for correcting a precise position and a correction data for correcting a local position uniquely obtained for each of the articulated robot arms. The robot controller is provided between a control computer and each of the robots, and further moves an additional external axis based on the position correction data. A control device for controlling dual position correction of a position correction of a robot body and a position correction of the articulated robot arm based on the correction data, and an offline teaching of a robot connected to the control computer And a parent computer.

(Operation) For large workpieces that require simultaneous installation of multiple robots, two types of deviations are considered: a deviation that needs to be seen for the entire workpiece, such as mounting errors, and a local deviation, such as temporary attachment errors for individual parts. Must.

The above-described double correction corrects the above two types of shifts separately, and is efficient, and the conversion procedure is unified.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view of a robot system having an external shaft for transportation. In the figure, two portal structures 1a and 1b run freely on the track 2 in the X-axis direction, and the carriages 3a and 3b are connected to the ceiling beams of the portal structures 1a and 1b by Y.
It is mounted slidably in the axial direction, and furthermore,
4b is slidably mounted on the carriages 3a and 3b in the Z direction. The articulated robot arms 5a and 5b for welding are fixed downward to the respective tips of the lift tables 4a and 4b.

In the following description, the robots 8a and 8b with external axes including the portal structures 1a and 1b are simply referred to as robots. Although two robots are used in this embodiment, the number of robots may be increased depending on the size of the work to be constructed.

In such a robot system, CAD-based offline teaching is performed because the work is large. FIG. 2 is a block diagram of the CAD system. The position data of the robot created by the CAD system 6 is sent to the system control personal computer 7. Further, the system control personal computer 7 is connected to the robot controllers 9a and 9b of the two robots 8a and 8b described in FIG. The system control personal computer 7 sends data to the robot control devices 9a and 9b and instructs the operation thereof. Note that such a robot system is known.

Next, a large workpiece will be described with reference to FIGS. 3 and 4. FIG. FIG. 3 is a perspective view showing the attachment of the large-sized work 10, where the work 10 indicated by a solid line is a position originally determined, but is actually installed at a position indicated by a broken line. The equipment for improving the mounting accuracy has no technical problem, but is a heavy equipment and expensive equipment as a system.

Three points on the workpiece 10, for example, three corners 10a, 10b and 10c
If the position is determined, the position coordinates of the workpiece 10 can be corrected by a known means, that is, three-dimensional rotation / parallel correction using three reference points. This method is easy, and it is preferable that the calculation and correction are performed as a robot system because of its high flexibility. However, the robot 8b on the right in FIG.
In order to examine the corners 10a and 10b, the robot 8a on the left side must be moved further toward the end so as not to disturb, and the size of the work 10 is limited by subtracting the size of the robot 8a. is there.

As shown in FIG. 4, the workpiece 10 is provided with a plurality of parts 11 and 12 at various positions, and these parts generally have processing and mounting errors. Therefore, it is necessary to correct the shift by detecting the position with a sensor for the local shift. On the other hand, as shown in FIG. Assuming that the length of the work 10 is, for example, 10 m, a mounting error of 1 mm is shifted by 17 cm at the end. Arc welding sensors have a resolution of 0.
It requires 2mm and a detection range of 17cm is impractical for a visual sensor. Further, with a contact-type sensor, the contact start position can be moved to a position 17 cm or more from the standard work position, but much time is required for sensing.

This problem can be solved by the following two means as described in the section of the solution. One is two robots 8a and
The position data of the specific point examined by 8b is once sent to the system control personal computer 7, and the system control personal computer 7 instructs the robots 8a and 8b on necessary data, respectively. However, the robot controllers 9a and 9b are respectively articulated robot arms 5a and 5a that require six-axis control.
Controls 5b, articulated robot arms 5a and 5b
Since three-axis control is required to control the position of the robot, if position correction by the portal structures 1a and 1b is applied to one robot 8Ba and 8b, nine-axis control is required. It cannot be controlled by 9a and 9b.

In order to solve this problem, the system control personal computer 7 was used to construct the portal structures 1a and 1b based on the mounting error data of the entire work 10 obtained from three reference points of the work 10 examined by two robots. Control the X, Y and Z axes,
Rough deviation is corrected only with the additional external axis. In this case, there is practically no problem even if the rough deviation correction is not considered as having little effect on the posture of the torch.
As described above, by performing the correction for the entire workpiece 10, the mounting error of the workpiece can be absorbed. Therefore, the distance required for sensing does not become longer than necessary.

On the other hand, as described with reference to FIG. 4, the workpiece 10 is generally provided with a plurality of components 11 and 12, and the mounting accuracy thereof is generally different. Therefore, it is difficult to secure the mounting accuracy that allows the welding to be performed as it is even when the rough deviation correction is performed by the above method. However, deviation correction for mounting errors and the like of these components 11 and 12 is performed by checking three reference points in the respective working ranges and performing three-dimensional parallel rotation correction. These correction amounts are determined by the articulated robot arm 5a.
And the range that can be covered by the combination of 5b's own correction capability and the component mounting jig.

FIGS. 5 (a) and 5 (b) are flowcharts showing specific procedures to be performed in parallel with the displacement correction such as the component mounting error and the large displacement correction of the workpiece mounting error. Thereby, a robot system with no waste is configured as a whole.

(Effects of the Invention) As described above, according to the present invention, when a plurality of robots weld a large workpiece that is not uniform in partial accuracy and exceeds the operating range of one robot, the external accuracy is reduced. A robot system capable of easily, efficiently, and accurately coping with the rough deviation correction by the axis and the mounting error correction of parts for each robot can be obtained.

[Brief description of the drawings]

1 is a perspective view of a welding robot system, FIG. 2 is a configuration diagram of the robot system, FIG. 3 is a perspective view for explaining a mounting error of a large work, and FIG. 4 is a large work with parts mounted thereon. FIGS. 5A and 5B are flowcharts of the double correction process. 1a, 1b: gate structure, 2: track, 3a, 3b: carriage,
4a, 4b… elevating platform, 5a, 5b… articulated robot arm, 6
…… CAD system, 7 …… System control PC, 8a, 8b
…… Robot with external axis, 9a, 9b …… Robot controller, 1
0 ... Work, 10a, 10b, 10c ... Square, 11,12 ... Parts.

Claims (1)

(57) [Claims] 1. A multi-joint robot arm working in cooperation with the same work, an additional external axis for moving the robot arm body, and a plurality of sensors having a work tool and a sensor at a tip of the robot arm body. Robots, data of reference points detected by the sensors of the plurality of robots are collected, and the collected data is used as position correction data for correcting the overall position of each robot arm body, and A control computer that sorts and divides the data into correction data for correcting a local position independently determined for the articulated robot arm; and a control computer provided between the control computer and each of the robots.
Further, control of dual position correction of position correction of the robot arm body by moving an additional external axis based on the position correction data and position correction of the articulated robot arm based on the correction data. And a master computer for off-line teaching of a robot connected to the control computer.