JP3000162B2 - Arc welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding apparatus for performing welding while following a welding line.

[0002]

2. Description of the Related Art FIG. 2 is a schematic structural view showing an arc welding apparatus according to an embodiment of the present invention. A conventional example of the above-described arc welding apparatus will be described with reference to FIG. In the figure, reference numeral 4 denotes a welding torch, and reference numeral 3 passes through a contact tip (not shown) in the welding torch 4 and is fed toward the base materials 1a and 1b by a wire feeder (not shown). Supplied welding wire. Also, in FIG.
A welding control unit comprising a robot arm (torch moving means) for moving the welding torch 4, an encoder (welding position grasping means) for detecting the position of the welding torch 4, a welding power source, a welding wire feeding device, and the like. is there. On the other hand, a laser sensor (welding line detection sensor) 5 for detecting a welding line is shown in FIG. The laser sensor 5 includes, for example, a slit light source and a camera.
It is attached to and provided. The result of detection by the laser sensor 5 is sent to a sensor controller 6 configured using an integrated circuit including a microcomputer function, processed, and transmitted to the controller 7 via a communication line or a bus line of RS232C. You. The controller 7 is also configured using an integrated circuit including the functions of a microcomputer similarly to the sensor controller 6, and controls the welding control unit 8. In the conventional arc welding apparatus described above, an arc is generated between the welding wire 3 and the base materials 1a and 1b at the tip of the welding torch 4 by the electric power supplied from the welding power source, thereby forming the base materials 1a and 1b. Perform welding. Then, by controlling the robot arm based on the position of the welding line detected by the laser sensor 5, welding can be performed while automatically following the welding line. Therefore, the following describes this copying control.

First, a laser beam is emitted from a laser sensor 5 so as to cross a welding line toward a required target point in front of the welding line. The emitted light has, for example, a band shape, and the relative position between the laser sensor 5 and the target point, that is, the position of the target point on the sensor coordinates can be read from the bent shape of the bright line of the reflected light. Then, the laser sensor 5 receives the reflected light again and outputs an output signal based on the reflected light to the sensor controller 6. Thus, the sensor controller 6 has a function as target point grasping means.

On the other hand, the welding torch 4
The rotation angle of each arm provided in the robot arm that moves is output. From this output, the position of the tip of the welding torch 4 on the robot coordinates can be known. Here, the robot coordinates refer to a coordinate system whose origin is the base point of the robot arm. That is, the welding torch 4 is controlled on the robot coordinates. Therefore, the position of the target point grasped on the sensor coordinates is then transformed into robot coordinates. Then, the robot arm is controlled based on the position of the target point expressed on the robot coordinates, and scanning control along a welding line is performed.

[0005]

In the conventional arc welding apparatus constructed as described above, the laser sensor 5 is attached to the welding torch 4, and therefore, no special driving mechanism for the laser sensor 5 is required. Thus, the copying control of arc welding can be performed with a simple configuration. However, on the other hand, the position of the target point on the welding line must be converted from the sensor coordinates to the robot coordinates.
At this time, a conversion matrix determined from the geometric relationship between the welding torch 4 and the laser sensor 5 is required, and the operation for obtaining the conversion matrix is called calibration.

In the above-described conventional arc welding apparatus, calibration is performed by the following method. That is,
A jig capable of accurately determining the relative positional relationship between the welding torch 4 and the laser sensor 5 is formed, and a conversion matrix is obtained from the geometric relationship represented by the jig.
However, according to such calibration,
After the laser sensor 5 is attached to the welding torch 4 using the jig, if the relative positional relationship between the welding torch 4 and the laser sensor 5 changes due to, for example, a collision or the like, accurate coordinate conversion can be performed thereafter. There was a problem that it became impossible. So, as another calibration method,
After attaching the laser sensor 5 to the welding torch 4, an approximate value of the conversion matrix is obtained from the approximate dimensions, and thereafter, the conversion accuracy is gradually increased by repeating trial and error. However, according to this approach,
There is a problem that it takes time to find a conversion matrix with high accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and has as its object to easily and easily determine the relative positional relationship between the two for performing coordinate conversion from sensor coordinates to robot coordinates. An object of the present invention is to provide an arc welding apparatus that can always perform high-accuracy copying control.

[0008]

Accordingly, an arc welding apparatus according to the present invention is provided with a welding torch, torch moving means for moving the welding torch, and attached to the welding torch as shown in FIG. Welding point detection sensor, target point grasping means for grasping the position of a desired target point on the welding line on the sensor coordinates based on the output of the welding line detection sensor,
Welding position grasping means for grasping the position of the tip of the welding torch on robot coordinates; coordinate transformation means for transforming the position of the target point grasped on sensor coordinates onto robot coordinates; Control means for controlling the torch moving means to move the welding torch relative to the welding base material based on the obtained position of the target point on the robot coordinates, wherein the welding is performed while following the welding line. The device, when the tip of the welding torch is aligned with a predetermined reference point set in advance, the position information in robot coordinates of the reference point grasped by the position grasping means, and the position of the reference point When detecting with the sensor, the target point grasping means and the position grasping means respectively determine the position of the reference point on the sensor coordinates and the position of the tip of the welding torch in the robot coordinates. Based on the plurality of position information grasped multiple times, and configured to determine the transformation matrix used for the coordinate transformation, further approximate matrix the transformation matrix
The product of the welding torch and the sensor
The approximate value matrix is obtained in advance from the
It is characterized in that the above transformation matrix is obtained by obtaining a column .

Here, the sensor coordinates refer to a coordinate system having the origin as a predetermined base point of the welding line detection sensor as described above.
Further, the robot coordinates refer to a coordinate system having a base point of the robot arm as an origin.

In the arc welding apparatus of the first aspect, the position of the reference point on the sensor coordinates and the position of the tip of the welding torch on the robot coordinates when the reference point is detected by the welding line detection sensor. By comparing with the position of the reference point on the robot coordinates, the relative positional relationship between the tip of the welding torch and the origin of the sensor coordinates can be grasped. Therefore, the relative positional relationship for performing the coordinate conversion from the sensor coordinates to the robot coordinates can be obtained at any time and easily,
This makes it possible to always perform highly accurate coordinate conversion. In addition, the position of the reference point on the sensor
The position of the tip of the torch on the robot coordinates is
A plurality of times by the gauge and the position grasping means
Since it is determined based on multiple pieces of acquired location information,
Reduces reference point detection errors to achieve high accuracy in the above relative positional relationships
Can be obtained by

Furthermore, in the arc welding apparatus according to the first aspect, coordinate conversion from sensor coordinates to robot coordinates is performed.
Coordinate conversion to find relative positional relationships for
It can be performed with high precision.

In the arc welding apparatus according to the second aspect, the approximate value matrix and the minute amount value matrix are respectively expressed by the following equations (16) and (1).
Expressed in 7 it is characterized by finding the transformation matrix
You.

(Equation 16)

[Equation 17]

In the arc welding apparatus according to the second aspect, it is possible to easily and accurately perform coordinate conversion for obtaining a relative positional relationship for performing coordinate conversion from sensor coordinates to robot coordinates.

According to a third aspect of the present invention, in the arc welding apparatus, the reference point is set on a welding line. In the arc welding apparatus according to the third aspect, the relative positional relationship can be easily obtained according to the welding situation.

The arc welding apparatus according to claim 4 is characterized in that the plurality of pieces of position information are obtained while changing the detection posture of the welding line detection sensor at least three times.

In the arc welding apparatus according to the fourth aspect , it is possible to easily obtain the relative positional relationship including the rotation component.

An arc welding apparatus according to a fifth aspect is characterized in that the detection posture is changed four times.

In the arc welding apparatus according to the fifth aspect, the relative positional relationship including the rotation component can be easily obtained with high accuracy.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the arc welding apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is a schematic structural view of the arc welding apparatus. The schematic configuration of this arc welding apparatus is the same as that of the above-described conventional example, and includes a welding torch 4 moved by a robot arm,
a, welding wire 3 and welding torch 4 fed to 1b
A laser controller 5 mounted on a robot, a welding control unit 8 having a robot arm, an encoder, and the like, a sensor controller 6 for processing and outputting a detection result of the laser sensor 5, and controlling the welding control unit 8. It comprises a controller 7 and the like.

In the same manner as in the prior art, the above-mentioned arc welding apparatus also uses a welding power source supplied from a welding power source to make the welding torch 4
An arc is generated between the welding wire 3 and the base materials 1a and 1b at the distal end of the base material, thereby welding the base materials 1a and 1b. By controlling the robot arm based on the position of the target point on the welding line 2 detected by the laser sensor 5, the welding line 2 is automatically moved from left to right in the figure as shown by the arrow in FIG. Welding is performed while imitating. Therefore, the left side of the welding wire 2 in FIG. 2 is the welded portion 2a and the right side is the unwelded portion 2b. At this time, while the robot arm is controlled on the robot coordinates as described above, the laser sensor 5 grasps the position of the target point on the welding line on the sensor coordinates. Therefore, a conversion matrix determined from the geometric relationship between the welding torch 4 and the laser sensor 5 is required. Therefore, next, calibration for obtaining the conversion matrix will be described.

First, the laser sensor 5 is attached to the welding torch 4. Then, the base materials 1a and 1b are installed, an appropriate welding line 2 is selected as shown in FIG. 3, and one point on the welding line 2 is marked. The point marked in this way is the reference point P
Becomes Next, the reference point P is taught at the tip of the welding torch 4. Then, the position of the reference point P on the robot coordinates is grasped by the encoder provided in the welding control unit 8, and the grasped position is output to the controller 7.

Subsequently, the reference point P is detected by the laser sensor 5. That is, the light cutting line 5a formed by the laser light
Teaches the robot arm so as to cross the reference point P. At this time, if the emitted laser light is visible light, it can be easily determined with the naked eye whether or not the light cutting line 5a has crossed the reference point P. Since the laser beam 5a can be visually recognized, the laser beam used may be visible light or infrared light. From the sensor output, the position of the reference point P on the sensor coordinates is grasped by the sensor controller 6,
The grasped position information is transmitted to the controller 7 via a communication line or a bus line of RS232C.

The encoder provided in the welding control unit 8 always keeps track of the movement angle of the robot arm, that is, the position of the tip of the welding torch 4 on the robot coordinates. Therefore, when the above teaching is performed, the position of the tip of the welding torch 4 at that time is grasped on the robot coordinates by the encoder almost simultaneously with the detection of the reference point P by the laser sensor 5. . Therefore, this position information is also output from the welding control unit 8 to the controller 7.

The detection of the reference point P by the laser sensor 5 as described above is repeated four times (i = 1 to 4) in total while changing the detection posture as shown in FIG. Therefore, from the above operation, the position A of the reference point P expressed in robot coordinates
(A is a 4 × 4 matrix), 4 expressed in sensor coordinates
The position S _i (i = 1 to 4) of the reference point P of each type and the position R _{i of the} tip of the four types of welding torches 4 represented by robot coordinates.
(I = 1 to 4) is obtained. These A, S _i , and R _i are input to the controller 7, and a transformation matrix is obtained by the coordinate transformation means. This coordinate conversion means is constituted by software, and its calculation algorithm will be described next.

FIG. 4 is a diagram showing the relationship between A, S _i and R _i . Here, the tool coordinate system shown in the drawing is a coordinate system whose origin is the tip of the welding torch 4, and C is a conversion matrix from the tool coordinate system to the sensor coordinate system. Therefore, the determination of C from the relationship between A, S _i, and R _i is calibration. By the way, from the relationship shown in the figure, it is understood that the following relationship is established among A, S _i , R _i , and C.

(Equation 1) If you transform this,

(Equation 2) Can be obtained. Here, R _i ^-1 and S _i ^-1 represent the inverse matrices of R _i and S _i , respectively. However, in (Equation 2), only the x, y, and z components of S _i are obtained from the laser sensor 5, and the rotation components thereof are unknown. Therefore, the above (Equation 2) cannot be solved as it is. Therefore, C is defined as follows.

(Equation 3)

(Equation 4)

(Equation 5) C ₀ represents an approximate value of C, and ΔC represents a minute amount for matching C ₀ with C. Among them, c _{11 to} c ₃₃ ,
The values of x _c , y _c , and z _c are determined by the welding torch 4 and the laser sensor 5.
This is an approximate value that can be easily obtained from the geometric relationship with However, δx, δy, δz, Δx, Δy, Δz are each unknown.

On the other hand, the x, y, and z components of A are x _p , y _p , and z _p , respectively. Since these are values that can be grasped from the output of the encoder and are all known, by substituting them into (Equation 1) and extracting only the x, y, and z components,

(Equation 6) Can be obtained. Here, the x, y, and z components of S _i are x _si , y _si , and z _si , respectively. These can be grasped from the output value of the laser sensor 5, and therefore all are known. Substituting this into (Equation 6) gives

(Equation 7) Can be obtained, and when this is further transformed,

(Equation 8) Becomes

The above (Equation 8) gives δx, δy, δz, Δ
This is a 6-way simultaneous equation in which x, Δy, and Δz are unknowns, but there are 12 equations. Since the number of equations is greater than the number of unknowns, a least squares solution is obtained by the following method.
First, the value on the right side of (Equation 8) is known, and its x, y, z
Let the components be x _pi , y _pi , and z _pi . Then, the above (Equation 8) becomes

(Equation 9) Can be written. When this (Equation 9) is rewritten for i = 1 to 4,

(Equation 10) Becomes

Here, for the sake of simplicity, (Equation 10) is replaced as follows.

[Equation 11] H is a matrix of 12 rows × 6 columns in (Equation 10), and L and Z are column vectors. Here, the above (Equation 1)
The shortest left inverse method is applied to 1). Then

(Equation 12) Using,

(Equation 13) Can be written. ^t H is the transposed matrix of H. Thus, δx, δy, δz, Δx, Δy, Δz can be obtained. Then, by substituting this into (Equation 5) and calculating (Equation 3), C as a transformation matrix can be obtained.

The conversion matrix C obtained as described above represents the relative positional relationship between the tip of the welding torch 4 and the origin of the sensor coordinate system. The position of the target point on the sensor coordinates detected in step 5 can be converted to the robot coordinates. What is needed for that purpose is movement by teaching of the robot arm after the laser sensor 5 is attached to the welding torch 4 and software processing. Therefore, the above calibration can be performed at any time and easily. Therefore, even if the relative positional relationship between the welding torch 4 and the laser sensor 5 changes due to a collision or the like, the above-mentioned arc welding apparatus can perform accurate calibration again quickly by performing calibration again.

In the above description, the detection of the reference point P is repeated four times while changing the detection attitude of the laser sensor 5. Therefore, calibration including the rotation component can be performed, and thereby, a highly accurate conversion matrix C can be obtained. In addition, since the least squares solution is obtained by establishing simultaneous equations larger than the number of unknowns, the accuracy can be further improved.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention. In the above description, the detection of the reference point P by the laser sensor 5 is repeated four times while changing the detection attitude, but may be performed three times. In this case, more rapid calibration can be performed, and one of them can be appropriately selected in relation to accuracy. When calibration including a rotation component is not particularly required, the reference point P may be detected without changing the attitude of the laser sensor 5. Also in this case, by detecting the reference point P with the laser sensor 5 a plurality of times, it is possible to reduce the detection error and obtain a more accurate conversion matrix. Further, in the above description, the control of the robot arm and the coordinate conversion are performed in the same controller 7; however, the configuration shown in FIG. It is.

In the above description, the reference point P for calibration is placed on the welding line, thereby enabling highly accurate calibration according to the welding situation.
The reference point P may be set to a location other than the welding line depending on the convenience of the teaching operation. At this time, if a point whose position on the robot coordinates is known in advance is set as the reference point P, the operation of teaching the reference point P at the tip of the welding torch 4 can be omitted, and the calibration can be further simplified.

[0034]

According to the arc welding apparatus of the first aspect, the relative positional relationship for performing the coordinate conversion from the sensor coordinates to the robot coordinates can be obtained at any time and easily.
High-precision copying control can always be performed. In addition, the relative positional relationship can be obtained with high accuracy by reducing the detection error of the reference point. In addition, the robot
Calculate the relative positional relationship for performing coordinate conversion to
Conversion can be performed easily and with high accuracy.
Becomes

In the arc welding apparatus according to the second aspect , it is possible to easily and accurately perform coordinate conversion for obtaining a relative positional relationship for performing coordinate conversion from sensor coordinates to robot coordinates.

In the arc welding apparatus according to the third aspect , the relative positional relationship can be easily obtained according to the welding situation.

In the arc welding apparatus according to the fourth aspect , it is possible to easily obtain the relative positional relationship including the rotation component.

In the arc welding apparatus according to the fifth aspect , it is possible to easily and highly accurately obtain the relative positional relationship including the rotation component.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an arc welding apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of the arc welding apparatus.

FIG. 3 is a diagram showing reference points on a welding line.

FIG. 4 is a diagram illustrating a relationship between coordinate systems and a transformation matrix.

FIG. 5 is a diagram showing a detection state of a reference point by a laser sensor.

[Explanation of symbols]

1a Base material 1b Base material 2 Welding line 2a Welding line (welded part) 2b Welding line (unwelded part) 4 Welding torch 5 Laser sensor 6 Sensor controller 7 Controller 8 Welding control unit P Reference point A Reference point position (Robot coordinates) S _i Position of reference point (sensor coordinates) R _i Position of tip of welding torch (robot coordinates) C Conversion matrix

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01S 3/00 H01S 3 / 00F (56) References JP-A-8-272414 (JP, A) JP-A-6-265367 ( JP, A) JP-A-2-12504 (JP, A) JP-A-61-235909 (JP, A) JP-A-3-26482 (JP, A) JP-A-9-26808 (JP, A) JP 60-262205 (JP, A) JP-A-63-251177 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/127 B23K 9/12 B25J 9/10 G01B 11 / 00 G01B 21/00 H01S 3/00

Claims (5)

(57) [Claims] 1. A welding torch, torch moving means for moving the welding torch, a welding line detection sensor attached to the welding torch, and a required welding line on the welding line based on an output of the welding line detection sensor. Target point grasping means for grasping the position of the target point on the sensor coordinates, position grasping means for grasping the position of the tip of the welding torch on the robot coordinates, and a robot for grasping the position of the target point grasped on the sensor coordinates. Coordinate conversion means for converting the coordinates into coordinates, and controlling the torch moving means to move the welding torch relative to the welding base metal based on the position of the target point on the robot coordinates obtained by the coordinate conversion. An arc welding apparatus for performing welding while following a welding line, wherein when the tip of the welding torch is aligned with a predetermined reference point set in advance, When the position information on the robot coordinates of the reference point grasped by the robot coordinates, and the position of the reference point is detected by a sensor, as the position on the sensor coordinates of the reference point and the position on the robot coordinates of the tip of the welding torch, respectively based on the plurality of position information grasped multiple times by the above target point grasping means and the locating means, to determine the transformation matrix used for the coordinate transformation structure
And transforms the above transformation matrix into an approximate value matrix and a minute amount value matrix.
From the geometric relationship between the welding torch and the sensor.
Finding the approximate value matrix in advance and then finding the minute value matrix
An arc welding apparatus characterized in that the conversion matrix is obtained by the following. 2. The arc welding apparatus according to claim 1 , wherein the conversion matrix is obtained by expressing the approximate value matrix and the minute amount value matrix by the following Expressions 14 and 15, respectively. [Equation 14] (Equation 15) 3. The arc welding apparatus according to claim 1, wherein the reference point is set on a welding line. 4. The arc welding apparatus according to claim 1, wherein the plurality of pieces of position information are obtained while changing the detection posture of the welding line detection sensor at least three times. 5. The arc welding apparatus according to claim 4 , wherein the detection posture is changed four times.