JP3317101B2 - Welding robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a teaching playback type welding robot.

[0002]

2. Description of the Related Art The automation of the welding process by an arc welding robot has been steadily expanding, mainly in mass production sites represented by the automobile industry, as an effective means for improving productivity and achieving uniform welding quality. Was.

[0003] In addition, a flexible production system using a robot has attracted great expectations as a very effective means for a multi-product small-lot production mode in response to diversification of consumer needs in recent years.

However, most of the currently operating welding robots are so-called teaching playback type robots. To cope with high-mix low-volume production, a large number of operation programs are required for one welding robot. While there is a need to teach, there is a tendency for skilled welding robot teaching workers themselves to be in short supply. Therefore, effective measures to reduce the number of teaching steps are desired.

In the teaching work method most commonly used at present, a teaching operator uses an operation switch of an operation box for instructing the movement of the welding robot, and observes the movement of the welding robot while observing the movement of the welding robot. Teaching is performed while moving, and in the case of a work to be welded including a curve or a change of direction, this teaching operation requires not only skill but also trials to obtain a desired movement. It is time-consuming, such as necessary.

[0006] In view of the above, various teaching methods independent of the operation box have been proposed, and are gradually being put into practical use.

One of the methods is to teach the absolute position on a coordinate system set on the work including the welding robot without actually moving the welding robot. A method of teaching by simulation, or a position teaching work device equipped with a light emitting element is moved along the welding line of the workpiece instead of a torch, and the light emitted from the work is detected by an image sensor fixed and installed on the work Teaching method.

As another method, there is a method of teaching while actually operating a welding robot. The method will be described below.

The first method is that the robot detects the movement of the welding torch fixed to the end of the robot arm or the gripping part imitating the welding torch while guiding the robot along the welding line. A method of detecting the movement is, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-85106, in which the direction in which the operator guides the grip portion and the magnitude of the guiding force. This is a method in which a force detector for detecting the torch is provided, and the position and orientation of the tip of the torch are calculated using the output signal.

This direct teaching is a teaching method that is easy for a teaching worker to handle because the worker can intuitively operate the welding robot without being conscious of the coordinate system of the welding robot.

In a second method, a welding robot automatically recognizes a welding start point and a welding line using a sensor, and the welding robot performs a teaching operation while autonomously following the welding line. Teaching work proceeds while the robot is performing the same operation as during actual operation, so not only is there no need to check interference and correct teaching points, but also the worker needs to work close to the welding robot. Since there is no teaching work, the teaching work can be performed safely, and the positioning and posture adjustment is automatically performed by the welding robot using the sensor information, so that there is an advantage that the teaching quality can be homogenized regardless of the skill of the worker. .

The means for automatically recognizing a welding start point and a welding line can be roughly classified into two types. The first means uses a distance sensor or an image sensor using a laser, an ultrasonic wave, or the like. The second means uses a welding operation itself such as a welding wire or a welding arc itself.

As disclosed in Japanese Patent Application Laid-Open No. 54-15441, a touch sensor based on a wire ground using a welding wire applies a voltage to the welding wire to form one electrode and the other electrode is applied to a work surface. The welding robot moves the welding wire to recognize the position of the workpiece from the position of the welding robot at the time when both electrodes, that is, the welding wire and the workpiece are in contact with each other to obtain electrical continuity, and this is repeated at a plurality of points. Thus, the welding line is detected.

An arc sensor using a welding arc is a method of recognizing the position of a welding line using a change in a welding signal as an information source as disclosed in Japanese Utility Model Application Laid-Open No. 54-55635. By weaving the welding torch in a plane perpendicular to the welding line within the groove of the joint, the distance between the welding tip and the base metal changes, and the position of the welding line is recognized from the change in welding current accompanying it. is there.

[0015]

In a teaching operation using a touch sensor with a welding wire which is originally required for welding, it is necessary to perform sensing at a plurality of positions for each teaching point, so that the detection operation is slow and the work becomes complicated. The greater the number of teaching points, the longer the time required for teaching, which has the problem of significantly impairing practicality.

In the teaching operation using an arc sensor, since the arc itself becomes a sensor, the teaching operation is performed while welding is performed, so it is not possible to redo the operation. In addition, it is difficult to track a welding line at a high speed, and a lap joint of a thin plate is practically used. , The tracking performance is greatly affected by welding conditions, and it is difficult to control the torch attitude.

The present invention solves the above-mentioned problems, and is applicable to a wide range of work shapes and work environments, and uses a non-contact distance sensor to detect the position of a welding line and the torch relative to the work without performing welding in advance. An object of the present invention is to provide a welding robot capable of automatically recognizing a posture and realizing a simple, safe and effective teaching man-hour reduction method.

[0018]

In order to achieve this object, a welding robot according to the present invention comprises a robot arm, a non-contact distance sensor attached to a tool portion at the tip of the robot arm, and a robot arm which moves. Position information storage means for storing position information of the welding line of the target work measured by the non-contact distance sensor when the first contact is made, a first coordinate system set in a tool portion at the tip of the robot arm, and the first coordinates from a point intersecting with the objective workpiece by extending the axis of the system
A second coordinate system having a coordinate axis in the direction of the weld line from the origin , the intersection of a perpendicular line drawn down to the weld line and the weld line, and a first coordinate system and a second coordinate system A positional relation calculating means for calculating a positional relation based on the positional information of the welding line stored by the positional information storing means; and a positional relation serving as a reference between the first coordinate system and the second coordinate system is preset. A positional relation setting storing means for storing, a positional relation between the first coordinate system and the second coordinate system calculated by the positional relation calculating means, and the first relation set and stored by the positional relation setting storing means in advance. And a robot control means for moving the robot amou so that the positional relationship between the coordinate system and the second coordinate system coincides with each other.

[0019]

With the above arrangement, the present invention measures and stores the position information of the target work by the non-contact distance sensor when the robot arm moves. Based on the position information, the positional relationship calculating means calculates the positional relationship between the first coordinate system and the second coordinate system, that is, the position and orientation of the welding line, the workpiece, and the welding torch, and calculates the calculated positional relationship. The robot control means operates the robot arm so that the robot arm coincides with the positional relationship set and stored in advance, so that the robot arm is automatically set to the desired positional relationship set and stored in advance, that is, the target position and posture of the welding torch. Can work.

[0020]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a vertical multi-joint type robot arm, to which a welding torch 2 (hereinafter simply referred to as a torch) is attached at the leading end of the arm. Reference numeral 3 denotes a laser sensor which is a non-contact distance sensor attached to the tip of the torch 2, and calculates position information with respect to a target work.
The position information calculated by the non-contact distance sensor 3 is output to the position information storage means 5 and stored. In the positional relationship calculation means 6, based on the position information stored in the position information storage means 5, a first coordinate system set in the tool portion at the tip of the robot arm and a second coordinate system set in the target work. Is calculated. Numeral 7 is a positional relationship setting storage unit for previously setting and storing a desired target position and a torch posture with respect to the work 4 as a positional relationship between the first coordinate system and the second coordinate system. The robot arm 1 is set and stored. It is driven by the robot control means 8 so that the positional relation matches the positional relation calculated by the positional relation calculating means 6.

As shown in FIG. 2, the laser sensor of this embodiment irradiates a laser slit light and captures reflected light from a target work on a two-dimensional CCD camera. The feature points are extracted from the captured shape of the target work, and the position of the target work is calculated.

First, a coordinate system as a reference of the positional relationship between the torch 2 and the work 4 will be defined with reference to FIGS.

FIG. 3 shows a first coordinate system (hereinafter referred to as a torch coordinate system) set for the torch 2. Reference numeral 3 denotes a laser sensor, and reference numeral 10 denotes a camera plane on which the shape of the target work is measured by the laser sensor 3. The camera plane is parallel to the torch. In the torch coordinate system, the point of action of the tip of the torch 2 is defined as a first coordinate origin Ot (hereinafter, referred to as a torch origin), and the center axis of the torch 2 is defined as an Xt axis. X
The positive direction of the t axis is indicated by an arrow in FIG. The perpendicular from the torch origin to the camera plane is defined as the Yt axis. The positive direction of the Yt axis is a direction from the torch origin to the camera plane. Then, a direction orthogonal to the Xt and Yt axes and forming a right-handed system is defined as a Zt axis.

The laser sensor 3 is fixedly attached to the torch 2, and the positional relationship of the camera plane with respect to the torch coordinate system is known in design or manufacture, and is stored as a camera-torch conversion matrix. Therefore, the position information of the target work measured by the laser sensor 3 can be recognized in the torch coordinate system by calculating using the camera / torch conversion matrix.

Next, FIG. 4 shows a second coordinate system (hereinafter, referred to as a work coordinate system) set on the target work 4. A lap joint is assumed as an example of the target work. Torch 2
Is positioned near the welding line on the workpiece 4,
The point at which the Xt axis of the torch coordinate system is extended to intersect with the work 4 is defined as Q, and the intersection of the perpendicular line drawn from the point Q to the welding line and the welding line is referred to as a second coordinate origin Ow (hereinafter, referred to as the workpiece origin).
And The direction of the welding line from the work origin is the Yw axis, and the direction orthogonal to the Yw axis and dividing the groove angle of the work 2 into two equal parts is the Xw axis. At this time, the positive direction of the Yw axis may be any direction, but the positive direction of Xw is the direction from the work origin to the back surface of the work 2, and the remaining Zw axis is orthogonal to the Xw and Yw axes and It shall be taken in the direction of the system.

FIG. 5 shows the positional relationship between the torch, the laser sensor, and the work, and FIG. 6 shows the joint shape recognized by the laser sensor. Based on this, the position of the welding line in the torch coordinate system is recognized using the camera-torch conversion matrix. The position of the torch coordinate system in the robot orthogonal coordinate system is known from the robot trajectory calculation. Therefore, the position of the welding line in the robot orthogonal coordinate system can be easily calculated using the camera-torch conversion matrix. The laser sensor is located at a position preceding the torch in the welding progress direction of the target work, and during execution of the operation of the present invention, the position of the welding line in the robot orthogonal coordinate system is stored in the position information storage means at regular intervals. It is memorized. Less than,
The position information of the welding line measured by the laser sensor and stored in the position information storage means is called a detected welding line. At the same time, the direction of equally dividing the groove angle of the target work on the camera plane is set as the Xc axis and stored as a vector in the robot orthogonal coordinate system. As will be described later, the vector data of the Xc axis is used to calculate the coordinate axes of the work coordinate system.

The procedure for calculating the work coordinate system will be described with reference to FIG. The point on the detected welding line closest to the torch origin Ot (known) is determined. From that point, on the detection welding line,
A point advanced in the traveling direction by the moving distance in each robot control cycle is defined as a work origin Ow. The moving distance for each robot control cycle is the moving speed of the robot. Therefore, of the six components representing the positional relationship between the torch coordinate system and the work coordinate system, Y
The direction component means that it is a variable that determines the direction and speed at which the welding line is tracked, and by changing this value according to the instruction of the robot operator, the direction and welding speed of the welding line can be arbitrarily selected, Or it can be adjusted. Also, for example, by calculating the curvature of the detected welding line and the operating speed of each axis of the robot arm, and increasing or decreasing the value of the Y-direction component accordingly, the welding speed is adjusted to the optimum value according to the situation at each time. It can be adjusted automatically.

Each coordinate axis at the workpiece origin Ow is obtained as follows. The Yw axis is a tangent to the detected welding line at the workpiece origin Ow. The Zw axis is an Xc axis vector,
This is the outer product of the Yw axis vector. The Xw axis is obtained by a direction orthogonal to the Yw and Zw axes and forming a right-handed system.

According to the above procedure, the work coordinate system in the robot orthogonal coordinate system can be calculated from the torch origin Ot and the detected welding line. The torch coordinate system is
Since the trajectory of the robot is known, the positional relationship between the torch coordinate system and the work coordinate system can be easily calculated. By operating the robot arm so that the positional relationship calculated as described above matches the desired positional relationship set and stored in advance, a workpiece whose direction and position are unknown is automatically detected to obtain a desired target position. And the torch can be positioned in the torch posture.

In this embodiment, a target work is detected by a laser sensor preceding the torch, the detected welding line is stored, and the torch is positioned based on the position information. At this time, since the position of the torch is set in advance by the positional relationship setting storage unit, the position and the position of the laser sensor with respect to the target work are uniquely determined. Therefore, depending on the complexity of the target work, the welding line may be out of the field of view of the laser sensor and cannot be recognized. The possibility of undetectability increases as the distance between the torch and the laser sensor increases, and decreases as the distance between the torch and the laser sensor decreases. Therefore, when teaching is performed by the method of the present invention, it is desirable to make the distance between the torch and the laser sensor as short as possible. Conversely, during welding, the laser sensor is affected by the arc light, so it is desirable to keep the distance between the torch and the laser sensor as large as possible.

The present embodiment further comprises means for changing the position of the laser sensor attached to the torch during welding and during non-welding in order to eliminate the dilemma. A robot for use.

Thus, when welding is not being performed, that is, at the time of teaching, the distance between the torch and the laser sensor is reduced to reduce the possibility that the target work cannot be detected. By increasing the distance, the influence of the arc light on the laser sensor can be reduced.

There are various mounting methods, such as a simple method of mechanically changing the mounting position and a method of changing the position of the laser sensor using power.

[0035]

As described above, according to the present invention, the position and orientation of the welding line and the workpiece and the welding torch can be calculated at high speed by the non-contact distance sensor, and the desired and previously set and stored can be calculated. Since the robot arm can be automatically moved to the positional relationship, that is, the target position or posture of the welding torch, the number of teaching steps can be reduced easily and safely. It has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the concept of a welding robot according to one embodiment of the present invention.

FIG. 2 is a schematic perspective view showing the concept of a laser sensor.

FIG. 3 is a conceptual diagram of a first coordinate system (a torch coordinate system).

FIG. 4 is a conceptual diagram of a second coordinate system (work coordinate system).

FIG. 5 is a conceptual diagram showing a positional relationship between a torch, a laser sensor, and a work, and a procedure for calculating a work coordinate system.

FIG. 6 is a conceptual diagram showing a relationship between a joint shape and an Xc axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Robot arm 2 Torch 3 Non-contact distance sensor (laser sensor) 4 Work 5 Position information storage means 6 Position relation calculation means 7 Position relation setting storage means 8 Robot control means 9 Robot control device

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G01B 11/00 G01B 11/00 A G01S 17/88 G01S 17/88 Z (56) References A) JP-A-5-69133 (JP, A) JP-A-62-187574 (JP, A) JP-A-5-77046 (JP, A) JP-A-58-34781 (JP, A) JP-A-6060 JP-A-37273 (JP, A) JP-A-61-270090 (JP, A) JP-A-62-39190 (JP, A) JP-A-63-175204 (JP, U) (58) Fields investigated (Int. . ^7, DB name) B23K 9/12 B23K 9/127 B25J 9/22 B25J 19/04 G01B 11/00 G01S 17/88

Claims (4)

(57) [Claims] 1. A robot arm, a non-contact distance sensor attached to a tool portion at the tip of the robot arm, and position information of a welding line of a target workpiece measured by the non-contact distance sensor when the robot arm moves. The position information storage means to be stored, the first coordinate system set in the tool portion at the tip of the robot arm, and the axis of the first coordinate system are extended and lowered to a welding line from a point intersecting the target work .
The intersection of the perpendicular and the welding line is defined as the origin , and a second coordinate system having a coordinate axis in the direction of the welding line from the origin, and the positional relationship between the first coordinate system and the second coordinate system are stored by the position information storage means. Positional relationship calculating means for calculating based on the stored positional information of the welding line, positional relationship setting storing means for presetting and storing a positional relationship that is a reference between the first coordinate system and the second coordinate system, The positional relationship between the first coordinate system and the second coordinate system calculated by the positional relationship calculating means, and the first coordinate system and the second coordinates previously set and stored by the positional relationship setting storage means. A robot control means for moving the robot amou so that the positional relationship of the systems coincides with each other. 2. The welding robot according to claim 1, wherein the non-contact distance sensor is a laser sensor that scans and irradiates the target work with a laser spot light, and measures position information of the target work based on the reflected light. . 3. The welding robot according to claim 1, wherein the non-contact distance sensor is a laser sensor that irradiates a laser slit light and measures the position information of the target work based on the reflected light. 4. The welding robot according to claim 1, further comprising means for changing a mounting position of the non-contact distance sensor to the tool portion during welding and during non-welding.