JP5244166B2 - Arc welding robot and its weaving method - Google Patents

Description

  The present invention relates to an arc welding robot that performs welding while weaving a welding torch and a weaving method thereof.

  For example, an arc welding robot including a multi-joint robot with 6 degrees of freedom is configured to attach a welding torch to the tip of an arm and move the welding torch to an arbitrary position in spatial coordinates in an arbitrary torch posture. When performing butt welding or fillet welding, in order to form a weld metal flat and reduce internal defects, the welding electrode protruding from the torch tip of the welding torch is perpendicular to the welding line. A swinging weaving operation is performed (see, for example, Patent Document 1). Some arc welding robots are configured so that a weaving mechanism is attached to the tip of an arm and the above-described weaving operation is performed (see, for example, Patent Documents 2 and 3).

  However, in the configuration in which the weaving operation is performed using each axis of the multi-joint robot as in the above-described conventional technique, there is a problem in that the positioning accuracy of the torch tip of the welding torch is likely to be lowered. The reason why the positioning accuracy is likely to decrease is that errors are accumulated due to the movement of each axis, and a large error occurs in the basic three axes consisting of a pivoting shaft having a low rigidity, a longitudinal swinging shaft, and a vertical swinging shaft. It was found by various tests. Further, in the configuration in which the weaving operation is performed using the weaving mechanism, there is a problem that the weaving mechanism increases the device cost.

JP 2002-239723 A JP 2000-117445 A JP-A-8-281443

  The problem to be solved is that the cost of the apparatus rises and the positioning accuracy of the tip position of the torch during the weaving operation cannot be improved.

  The most important feature of the present invention is that when the weaving operation is performed, the torch rotation angle of the welding torch is changed so that the amount of movement of the tip of the arm is minimized.

That is, the present invention provides an arm shaft comprising a pivot shaft of an arm base, a first swing shaft that swings with respect to the swing shaft, and a second swing shaft that swings with respect to the first swing shaft. , An arm rotation shaft that is a rotation shaft of the second swing shaft, a wrist swing shaft that swings with respect to the arm rotation shaft, and a wrist rotation shaft that is a rotation shaft of the wrist swing shaft a multi-joint robot having six degrees of freedom consisting of, with respect to the at the distal end of the articulated robot arm, the torch body is provided at a position deviated from the axis of the wrist rotation axis, the axis of the wrist rotation axis, A welding torch which is set so that the delivery direction of the welding wire delivered from the torch body intersects and the torch tip which is the tip of the welding wire is positioned on the axis of the wrist rotation axis Arc welding robot we A packaging method, the torch tip to the origin of the welding torch, Xm axis traveling direction along the weld line of the torch tip, Ym axis direction of the left and right with respect to the weld line, the Xm-axis and said Ym axis In the first welding line coordinate system in which the axis that is the outer product of the first welding line coordinate system is the Zm axis, the rotation angle around the Xm axis is the torch inclination angle, and the second welding is the first welding line coordinate system rotated by the torch inclination angle. In the linear coordinate system, when the axis corresponding to the Ym axis is the Ym ′ axis and the axis corresponding to the Zm axis is the Zm ′ axis, the rotation angle around the Ym ′ axis is a torch advance angle, and the second In the third weld line coordinate system in which the weld line coordinate system is rotated by the torch advance angle, the rotation angle around the Zm ″ axis when the axis corresponding to the Zm ′ axis is the Zm ″ axis is the torch. A rotation angle, and the center axis of the welding torch is Z In case that to match the'' axis, using said respective axes of the articulated robot, the torch tip of the welding torch is moved along the weld line, the welding the torch head at a predetermined frequency when performing periodic weaving action swinging to move right and left relative to the line, the welding torch as movement of the tip portions of the arm by the weaving operation is minimized, the torch rotation angle Is changed using each axis of the articulated robot.

  According to said structure, the positioning precision of the torch tip position at the time of a weaving operation | movement can be improved, without causing a raise of apparatus cost.

The present invention is also an arc welding robot, which is a swing axis of a base of an arm, a first swing axis swinging with respect to the swing axis, and a second swing swinging with respect to the first swing axis. Three of the arm shafts including the swing shaft, an arm rotation shaft that is a rotation shaft of the second swing shaft, a wrist swing shaft that swings with respect to the arm rotation shaft, and the wrist swing shaft a multi-joint robot having six degrees of freedom consisting of the wrist rotation shaft as the rotational axis, wherein at the distal end of the articulated robot arm, the torch body is provided at a position deviated from the axis of the wrist rotation axis, the wrist rotation to the axis of the shaft, feeding direction of the welding wire fed from the torch body is set so as to intersect, and set such that the tip torch head is in the welding wire is located on the axis of the wrist rotation axis a welding torch that is, the The torch tip of the contact torch is the origin, the traveling direction along the welding line at the tip of the torch is the Xm axis, the right and left direction with respect to the welding line is the Ym axis, and the axis that is the outer product of the Xm axis and the Ym axis is Zm In the first weld line coordinate system having an axis, the rotation angle around the Xm axis is a torch inclination angle, and in the second weld line coordinate system in which the first weld line coordinate system is rotated by the torch inclination angle, the Ym When the axis corresponding to the axis is the Ym ′ axis and the axis corresponding to the Zm axis is the Zm ′ axis, the rotation angle around the Ym ′ axis is the torch advance angle, and the second weld line coordinate system is the torch In the third welding line coordinate system rotated by the advance angle, the rotation angle around the Zm ″ axis when the axis corresponding to the Zm ′ axis is the Zm ″ axis is the torch rotation angle, and the welding torch So that the central axis of the line coincides with the Zm ″ axis. In case the, using said respective axes of the articulated robot, the torch tip of the welding torch is moved along the welding line, moves to the left and right with respect to the welding line the torch head at a predetermined frequency when performing a weaving operation for periodically swinging to the said torch rotation angle, movement of the tip portions of the arm by the weaving operation by changing with the axes of the articulated robot Min And a control device for controlling the articulated robot.

  According to said structure, the arc welding robot which can improve the positioning accuracy of the torch front-end | tip position at the time of a weaving operation | movement can be obtained, without causing a raise of apparatus cost.

  According to the present invention, there is an advantage that the positioning accuracy of the tip position of the torch during the weaving operation can be improved without causing an increase in apparatus cost.

It is a block diagram of an arc welding robot. It is explanatory drawing which shows the state of a weaving operation | movement. It is explanatory drawing which shows the state of a weaving operation | movement. It is explanatory drawing which shows the state of a weaving operation | movement. It is explanatory drawing which shows the state which a welding torch moves. It is explanatory drawing which shows the state which a welding torch moves. It is explanatory drawing which shows the calculation method of a torch rotation angle. It is explanatory drawing which shows the calculation method of a torch rotation angle. It is explanatory drawing which shows the calculation method of a torch rotation angle. It is a graph which shows the behavior of a basic 3 axis | shaft at the time of weaving by changing a torch rotation angle. It is a graph which shows the behavior of a basic 3 axis | shaft at the time of weaving, without changing a torch rotation angle. It is explanatory drawing which shows the state which a welding torch moves. It is explanatory drawing which shows the calculation method of a torch rotation angle. It is a graph which shows the behavior of a basic 3 axis | shaft at the time of weaving by changing a torch rotation angle. It is a graph which shows the behavior of a basic 3 axis | shaft at the time of weaving, without changing a torch rotation angle.

  The purpose of improving the positioning accuracy of the tip position of the torch during the weaving operation has been realized without incurring an increase in device cost.

An embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the arc welding robot according to the present embodiment includes a base 1 fixed on a floor surface and an arm 20 provided on the base 1. The arm 20 includes a base 2, a first arm 3, a second arm 4, and a wrist member 5. The base 2 is pivotably provided on the base 1 so as to function as the pivot axis J1. A first arm 3 is vertically provided on the upper surface of the base 2, and the first arm 3 is configured to be swingable so as to function as a front / rear swing shaft J <b> 2.

  The first arm 3 includes a main arm 3a and a sub arm 3b. The main arm 3a and the sub arm 3b pivotally support the second arm 4 on the free end side so as to function as the vertical swing axis J3. The second arm 4 is rotatable so as to function as an arm rotation axis J4, and a wrist member 5 is provided on the free end side. The wrist member 5 is swingable and rotatable so as to function as a wrist swing axis J5 and a wrist rotation axis J6. The arm 20 thus configured has a plurality of degrees of freedom by the axes J1 to J6, so that the arm tip 20a can be placed at an arbitrary position in three-dimensional spatial coordinates (X, Y, Z). It can be moved.

  The arm tip 20a is provided with a welding torch 7 via a torch bracket 8. The torch bracket 8 supports the welding torch 7 at a position deviating from the axis of the wrist rotation axis J6. The torch main body of the welding torch 7 is communicated from the delivery tip end surface to the rear end surface of the torch main body, and the welding wire 6 supplied to the rear end surface is inserted into the torch main body and delivered from the delivery front end surface. . The delivery direction of the welding torch 7 is set so as to intersect the axis of the wrist rotation axis J6, and the tip of the torch, which is the tip of the welding wire 6, is positioned on the axis of the wrist rotation axis J6. Is set. Accordingly, as shown in FIG. 2, the welding torch 7 moves so that the arm tip 20 a moves with the bottom of the rotating cone 21 having the top position (torch tip position) of the welding torch 7 as the movement locus. By operating each of the axes J1 to J6, only the torch rotation angle can be changed by the movement of the arm tip 20a and the change of the torch support posture while maintaining the torch inclination angle, the torch advance angle, and the torch tip position. It has become.

Here, the torch inclination angle, the torch advance angle, and the torch rotation angle are the attitude angles of the welding torch with respect to the welding progress direction (welding line coordinate system Σline). The origin of the welding line coordinates is the torch tip, which is the tip of the welding wire 6, and is determined by Xm axis = traveling direction, Ym axis = Xm axis × ( −gravity direction), Zm axis = Xm axis × Ym axis. . If the tip of the torch moves as seen from the base coordinate system Σbase, the welding line coordinate system Σline also moves as seen from the base coordinate system Σbase. The torch inclination angle Rx is defined as the rotation angle around the Xm axis in the weld line coordinate system Σline (the right screw direction is the + direction). As shown in FIG. 3 , the torch advance angle Ry is about Ym ′ in the coordinate system (second weld line coordinate system) obtained by rotating the weld line coordinate system Σline (first weld line coordinate system) by the torch inclination angle Rx . It is defined as the rotation angle (the right screw direction is the + direction). The torch rotation angle Rz is defined as the rotation angle around the Zm ″ axis in the coordinate system (third weld line coordinate system) obtained by rotating the second welding line coordinate system by the torch advance angle Ry (the right screw direction is the + direction). Is done. Further, the center axis of the welding torch coincides with the Zm ″ axis.

Further, the rotation order of the torch inclination angle, the torch advance angle, and the torch rotation angle is [around Xm] Rx → [around Ym ′] Ry → [around Zm ″] Rz , as shown in FIG. That is, the rotation matrix of the welding torch 7 viewed from the weld line coordinate system Σline is expressed by the following equation (1). In the above three types of angle notation, what affects the welding operation is the torch inclination angle Rx and the torch advance angle Ry, and the torch rotation angle Rz is a redundant degree of freedom that does not affect the welding operation. .

The torch support posture is a posture of the torch bracket 8 that supports the welding torch 7, as shown in FIG. For example, as shown by the solid line in the figure, when the torch rotation angle is changed while maintaining the torch inclination angle and the torch advance angle of the welding torch 7 constant, the circular shape of the rotating cone 21 with the torch tip position as the apex is used. There is a torch support posture in a form corresponding to each position moving on the bottom side of the .

  As shown in FIG. 1, the arc welding robot includes a control device 10 that controls the arm 20 and the like. The control device 10 includes an input conversion unit 11, an output conversion unit 12, an input / output unit 13, a storage unit 14, and a calculation unit 15. These units 11 to 15 are connected via a signal bus 16 so that data signals can be transmitted and received. The output converter 12 is connected to a motor that drives the axes J1 to J6 of the arm 20, and can drive the motor at a desired rotation angle and rotation speed. The input conversion unit 11 is connected to a detector that detects the displacement amount of each of the axes J1 to J6, and converts the displacement signal from the detector into a signal form suitable for the processing of the calculation unit 15. Yes. The input / output unit 13 is connected to the teaching box 17. The teaching box 17 is used when teaching welding data such as welding conditions, weaving data of a weaving operation, or the like by an operator's key operation.

  The storage unit 14 is formed with a program area and a data area. The program area stores a welding program for executing a welding operation, a weaving program for executing a weaving operation, and the like. The data area stores various data necessary for executing the program in a rewritable manner. Note that the welding program and the weaving program may be written in the ROM of the storage unit 14 in advance for reading only, or those recorded on a recording medium such as a CD are read out and written to the storage unit 14 when necessary. Alternatively, it may be transmitted via an electric communication line such as the Internet and written in the storage unit 14.

  The above weaving program includes a function of suppressing the vibration of the arm 20 during the weaving operation. The basic idea for realizing this function is to determine the torch rotation angle that reduces the amount of movement of the three basic axes (swivel axis J1, longitudinal swing axis J2, and vertical swing axis J3). That is, the movement amount of the basic three axes is substantially equivalent to the movement amount of the arm tip portion 20a (the rotation center position of the wrist swing axis J5 in the typical vertical articulated robot as shown in FIG. 4). Moreover, in welding construction, the torch inclination angle is an item that should be operated as commanded as one of the welding conditions, but the torch rotation angle is a redundant degree of freedom that does not affect welding. Therefore, by operating the torch rotation angle, the amount of movement of the arm tip 20a is reduced, thereby reducing the amount of movement of the basic three axes during the weaving operation, and as a result, reducing accuracy degradation. .

Specifically, as shown in FIGS. 1 and 4, the weaving program stores a welding start point P1 and a welding end point P2 that are given in advance to a computer including the calculation unit 15 and the storage unit 14 in the control device 10. And a first means for obtaining a welding line coordinate system Σline and a moving path equation P (t) = P1 + ΔP · t, and a torch tip of the welding torch 7 based on the moving path equation P (t) = P1 + ΔP · t Second means for obtaining the moving point P of the welding line coordinate system Σline that moves after time, third means for adding a weaving translational component to the moving point P (P = P + ΔW · sin (2πft)), and coordinates of the moving point P A fourth means for obtaining the position / orientation of the welding torch 7 as seen from the welding line coordinate system Σline as line P = (x, y, z, Rx, Ry, Rz) by conversion, and a torch included in the position / orientation Inclination angle Rx A fifth means for adding the inclination angle weaving component and adding the advance angle weaving component to the torch advance angle Ry, and obtaining the torch rotation angle Rz so as to reduce the movement of the basic three axes, and calculating the torch rotation angle Rz Sixth means for setting a torch rotation angle Rz included in the position / posture, seventh means for converting the position / posture into a base coordinate system and obtaining a moving point P ′ of the base coordinate system, and a moving point P ′ Thus, the joint angle of each axis is obtained by inverse kinematics, and the eighth means for operating the articulated robot is executed based on these joint angles. Note that, here, the moving path in the moving path equation is described as being a straight line, but the present invention is not limited to this, and the same applies even if the moving path is a curve. Therefore, in the following, the moving path equation may be referred to as a linear path equation.

Further, the weaving program, as the sixth means, a fluctuation width storage means for storing a fluctuation width dY of the rear end portion of the torch rotation shaft when the torch inclination angle is changed so as to obtain a desired weaving width; The rotational angle amplitude Rzwidth = −Sin ⁻¹ (dY / r) is calculated by substituting the fluctuation width dY and the perpendicular distance r from the arm tip to the torch rotation axis of the welding torch. And a rotation angle calculation means for calculating a torch rotation angle corresponding to the rotation angle amplitude Rzwidth.

Here, the rotation angle amplitude Rzwidth = −Sin ⁻¹ (dY / r) in the weaving program is derived as follows.

First, as shown in FIG. 5, in the arc welding robot of the present embodiment, when the torch rotation angle Rz is changed, the movement locus of the arm tip 20a becomes a circle. A rotating cone 21 is assumed with this circle as the bottom and the tip of the welding torch 7 as the apex. In this rotating cone 21, as shown in FIG. 6, the angle of intersection between the wrist rotation axis J 6 and the torch rotation axis of the welding torch 7 is the inclination angle φ. The distance from the tip of the welding torch 7 to the arm tip 20a is the slope length L. The perpendicular distance from the arm tip 20a to the torch rotation axis is the bottom surface radius r. The point where the center axis 22 of the welding torch intersects the bottom surface of the rotary cone 21 is the rear end portion of the torch rotation axis. The distance between the rear end portion of the torch rotating shaft and the front end portion of the welding torch 7 is the height H.

Next, it is assumed that the inclination angle amplitude is RxWidth (rad), the y-component weaving amplitude is ΔY (mm), and the planned torch attitude angle (before adding the weaving) is α, β, γ (rad). Consider the case where the torch inclination angle is rotated + RxWidth (rad) from the original posture Rx0 (rad) on the YmZm plane of the weld line coordinate system Σline as shown in FIG. Here, α, β, and γ (rad) are the attitude angles (roll, pitch, and yaw angles) of the welding torch 7 as viewed from the base coordinate system Σbase. Further, as shown in FIG. 7, a point (see FIG. 6) where the bottom surface of the rotating cone 21 and the center axis 22 of the welding torch intersect is the origin Oc, and a direction along the center axis 22 of the welding torch is the Zc axis. A coordinate system is defined in which the direction passing through the arm tip 20a and the origin Oc of the torch 7 is the Xc axis, and the direction perpendicular to the Xc axis and the Zc axis is the Yc axis. In this case, the rear end of the arm rotation shaft when the torch tip of the welding torch 7 is moved in the Ym direction by the weaving amplitude ΔY and the torch inclination angle is rotated from the original position Rx0 (rad) to + RxWidth (rad). The fluctuation range dY can be obtained geometrically. The optimum calculation formula of the torch rotation angle amplitude Rzwidth in the fluctuation range dY is the amount of movement of the arm tip 20a that moves along the bottom trajectory of the rotating cone 21 when the rotating cone 21 is viewed from the bottom surface side. Can be represented by −Sin ⁻¹ (dY / r) using the bottom surface radius r and the fluctuation range dY as parameters.

However, in order to make the torch rotation angle amplitude Rzwidth obtained by the equation −Sin ⁻¹ (dY / r) function effectively, (1) the weld line coordinates do not change abruptly, and (2) the torch advance angle It is necessary to satisfy the three conditions that the amplitude RyWidth is substantially 0 and (3) the original torch posture (before the weaving addition) does not change significantly.

Further, as shown in FIG. 8, when the torch inclination angle amplitude RxWidth is small and Sin (RxWidth) ≦ l ₃ / H, the torch rotation angle amplitude is calculated by the formula RzWidth = Sin ⁻¹ (dY / r). It is desirable to calculate RzWidth. Here, l ₃ is a welding torch when it is assumed that the center axis 22 of the original welding torch and the center axis 22 of the original welding torch are parallel to the Ym direction by the weaving width ΔY, as shown in FIG. Is the shortest distance from the central axis.

  In the above configuration, the operation of the arc welding robot and the weaving method will be described.

First, as shown in FIG. 1, when the control device 10 is turned on after the workpiece is set in a predetermined posture, a program such as a welding program or a weaving program stored in the storage unit 14 is stored in the calculation unit 15. It is executed by. Thereafter, for example, the teaching box 17 is operated, and the welding start point P1 and the welding end point P2, sine wave weaving conditions (amplitude ΔW, frequency fHz, etc.), torch inclination angle amplitude RxWidth (rad) (see FIG. 9) , torch advance Angular amplitude RyWidth (rad), torch rotation angular amplitude RzWidth (rad) (see FIG. 9), and the like are input.

  Next, as shown in FIG. 4, a welding line coordinate system Σline and a linear path equation P (t) = P1 + ΔP · t of P1 to P2 are obtained from the welding start point P1 and the welding end point P2. Note that ΔP is a movement amount per unit time. Also, t = 0. Thereafter, as t = t + Δt, P = P1 + ΔP · t is calculated, and the tip of the torch is moved from P1 to P2. Note that Δt is the control period of the robot.

  Next, by adding the weaving translational component, P = P + ΔW · sin (2πft). Then, P is coordinate-transformed, and the position / orientation of the welding torch 7 viewed from the welding line coordinate Σline is obtained as lineP = (x, y, z, Rx, Ry, Rz). At this time, the torch posture angle is calculated as (Rx: torch tilt angle, Ry: torch advance angle, Rz: torch rotation angle).

That is, first, ^base R _line is calculated from the direction cosine vectors Xm, Ym, Zm of the weld line coordinate system Σline (see FIG. 9) . Next, ^base R _tool is calculated from the torch attitude angle (roll, pitch, yaw angle: α, β, γ) of the welding torch 7 viewed from the base coordinate system Σbase. In addition, the rotation matrix of the welding torch 7 as seen from the welding line coordinate system Σline ^line R _tool = ^line R _base / ^base R _tool Is calculated.

After this, the tilt angle / advance angle / rotation angle (Rx, Ry, Rz) of the welding torch 7 is calculated from the calculated ^line R _tool , and the time series changes of the tilt angle / advance angle / rotation angle are added (= weaving amount) Is added). Specifically, the inclination angle Rx ′ = Rx + RxWidth (2πf · t), the forward angle Ry ′ = Ry + RyWidth (2πf · t), and the rotation angle Rz ′ = Rz + RzWidth (2πf · t) are obtained.

At the time of calculating the rotation angle Rz ′ = Rz + RzWidth (2πf · t), the optimization process of the rotation angle amplitude Rzwidth is performed. That is, it is determined whether or not the weaving operation is performed under a predetermined condition that the inclination angle amplitude RxWidth is small and Sin (RxWidth) ≦ l ₃ / H. When the weaving operation is not performed under a predetermined condition, as shown in FIG. 7, the calculation formula of Rzwidth = −Sin ⁻¹ (dY / r) is set to the fluctuation width dY and the central axis 22 of the welding torch from the arm tip. The rotation angle amplitude Rzwidth is obtained by substituting the perpendicular distance r with respect to. On the other hand, as shown in FIG. 8, in the case of the weaving operation under a predetermined condition, the rotation angle amplitude RzWidth is obtained based on the calculation formula of RzWidth = Sin ⁻¹ (dY / r) . Note that the calculation formula used for the optimization process of the rotation angle amplitude Rzwidth is selected in advance before the execution of the weaving operation.

Thereafter, ^line R _{tool ′} is calculated from the tilt angle / advance angle / rotation angle (Rx ′, Ry ′, Rz ′) and converted to a rotation matrix in the base coordinate system Σbase ( ^base R _{tool ′} = ^base R _line / ^line R _{tool '} ). Based on this ^base R _{tool ′} , the roll pitch pitch yaw angle (α, β, γ) of the welding torch 7 viewed from the base coordinate system Σbase is calculated. Thereafter, the joint angles of the axes J1 to J6 are obtained by the inverse kinematics process, and the weaving operation is performed by driving the motors of the axes J1 to J6 so as to be these joint angles.

When the weaving operation is performed as described above, as shown in FIG. 7 , the support posture of the torch bracket 8 (see FIG. 4) is changed based on the rotation angle amplitude RzWidth calculated by the above formula . When the welding torch 7 is rotated, the arm tip 20a is in a state of swinging, for example, the shortest distance between the point A and the point B in the bottom track of the rotating cone 21 (see FIG. 6) . And the joint angle of each axis | shaft J1-J6 of the arm 20 is suppressed by the slight fluctuation | variation range by rocking | fluctuation of this arm front-end | tip part 20a for a short distance. As a result, vibrations with respect to the basic three axes (J1, J2, J3), which have a relatively low rigidity, are suppressed, and as a result, it is easy to ensure the accuracy of the torch tip position, thereby performing an accurate welding operation. It becomes possible.

  Next, in order to confirm the effect of the weaving method in the present embodiment, the weaving operation is performed by performing the optimization process of the torch rotation angle Rz by the weaving method of the present embodiment, and the conventional weaving method, that is, The behavior of the basic three axes (J1, J2, J3) was investigated when the weaving operation was performed without performing the optimization process of the torch rotation angle Rz.

  As a result, when the weaving operation is performed by performing the optimization process of the torch rotation angle Rz, as shown in FIG. 10, the basic three axes (J1, J2, J3) are hardly vibrated. It was confirmed. On the other hand, when the weaving operation is performed without performing the optimization process of the torch rotation angle Rz, as shown in FIG. 11, large vibrations are generated in the basic three axes (J1, J2, J3), particularly in the J1 axis. Has been confirmed to occur. Thereby, according to the weaving method of this embodiment, it became clear that the weaving operation | movement by a higher frequency is also attained.

  That is, generally, the upper limit of the weaving frequency is determined by the natural frequency (about 10 to 20 Hz) of the basic three axes having relatively low rigidity. This is because the higher the weaving frequency and the closer to the natural frequency, the greater the vibration due to resonance and the desired accuracy cannot be maintained. Therefore, according to the weaving method of the present embodiment, since the vibration amount can be suppressed by reducing the movement amount of the basic three axes, a desired accuracy can be ensured even in a weaving operation at a higher frequency than the conventional weaving method. It was revealed.

  As described above, as shown in FIG. 1, the arc welding robot according to the present embodiment has at least six degrees of freedom including the three basic axes including the pivot axis J1, the longitudinal swing axis J2, and the vertical swing axis J3. The torch tip of the welding torch 7 is moved along the welding line using the axes J1 to J6 of the joint robot, the torch tip is swung to the left and right with respect to the welding line, and the torch inclination angle of the welding torch 7 When performing the weaving operation while changing the torch advance angle, welding is performed by a weaving method in which the torch rotation angle of the welding torch 7 is changed so as to reduce the movement of the basic three axes.

  That is, the arc welding robot includes an articulated robot having at least 6 degrees of freedom including three basic axes including a swing axis J1, a longitudinal swing axis J2, and a vertical swing axis J3, and each axis J1 to J6 of the articulated robot. The torch inclination angle, the torch advance angle, and the torch rotation angle can be changed by using the welding torch 7 that can be changed to an arbitrary position, and the torch tip of the welding torch 7 is moved along the welding line. When the weaving operation is performed while the tip of the torch is swung left and right with respect to the welding line and the torch inclination angle and the torch advance angle are changed, the movement of the basic three axes is reduced by changing the torch rotation angle. As described above, the controller 10 is configured to control the articulated robot.

  As a result, the weaving operation can be performed while reducing the amount of movement in the three basic axes including the pivot shaft J1, the longitudinal swing shaft J2, and the vertical swing shaft J3 having a small rigidity. The positioning accuracy can be improved. Further, since there is no need to provide a dedicated weaving mechanism, the apparatus cost does not increase.

  In addition, although this invention was demonstrated based on suitable embodiment, this invention can be changed in the range which does not exceed the meaning. That is, in this embodiment, the case where the optimum torch rotation angle is obtained geometrically has been described, but the present invention is not limited to this. That is, as shown in FIG. 12, an optimum torch rotation angle is obtained by a method of minimizing the distance (| ARM-ARMold |) before the movement (previous position ARMold) and after the movement (next position ARM) of the arm tip 20a. It may be required.

  That is, a welding torch 7 is provided at the tip of an arm of an articulated robot having at least 6 degrees of freedom including three basic axes including a pivot axis J1, a front and rear oscillation axis J2, and a vertical oscillation axis J3. The sixth means of the weaving program executed in the computer of the arc welding robot that performs welding while weaving the welding torch 7 using J1 to J6 is the previous position storage means for storing the previous position of the arm tip, and the weaving The next tilt angle storage means for storing the next torch tilt angle for operation, and the movable trajectory of the arm tip that can be taken by changing the torch rotation angle and the torch support posture while maintaining the next torch tilt angle And the next rotation angle acquisition means for obtaining the torch rotation angle that is closest to the position of the previous arm tip. It may be.

Specifically, inclination bevel amplitude: RxWidth (rad), the advancing angle amplitude: RyWidth (rad), weaving add vector Vw (ΔX, ΔY, ΔZ) (mm), the torch attitude before weaving addition: αβγ (rad) , Inclination / advance / rotation angle = (Rx0, Ry0, Rz0) (rad) Torch inclination angle after adding the weaving component: Rx '= Rx0 + RxWidth (2πft), Torch advance angle: Ry' = Ry0 + RyWidth (2πft), previous arm Position: ARMold.

Assuming that the bottom of the torch rotating cone viewed from the weld line coordinate system Σline is the coordinate system Σc, the rotation matrix is: ^line R _c = ^line R _tool = Rot (Rx ') / Rot (Ry') / Rot (Rz0) Thus, the parallel progression is ^line T _c = vector Vw + vector H · Zc. Then, as shown in FIG. 13, the optimal tool rotation angle Rz ′ that minimizes the absolute value of [ARM (Rz) −ARMold] is orthogonally projected from the vector V = ARMold−Oc to Σc, and Vc (Vx, Vy ) Can be calculated by Rz ′ = Tan ⁻¹ (Vy / Vx).

  Moreover, although this embodiment demonstrated the case where a weaving operation | movement was performed by changing the torch inclination angle of the welding torch 7 periodically, it is not limited to this. That is, the present invention can also be applied to a weaving operation in which the torch tip position is periodically changed while the torch inclination angle and the torch advance angle of the welding torch 7 are kept constant. And in order to confirm that there is an effect also in this weaving operation, when performing the weaving operation by performing the optimization process of the torch rotation angle Rz by the weaving method of this embodiment, the conventional weaving method, that is, The behavior of the basic three axes (J1, J2, J3) when the weaving operation was performed without performing the optimization process of the torch rotation angle Rz was investigated.

  As a result, when the weaving operation is performed by performing the optimization process of the torch rotation angle Rz, the basic three axes (J1, J2, J3) hardly vibrate as shown in FIG. It was confirmed. On the other hand, when the weaving operation is performed without performing the optimization process of the torch rotation angle Rz, as shown in FIG. 15, large vibrations are generated in the basic three axes (J1, J2, J3), particularly in the J1 axis. Has been confirmed to occur. As a result, it has been clarified that a weaving operation at a higher frequency is also possible by the above weaving method.

  Further, the weaving operation may be performed based on preset operation data. That is, the sixth means of the weaving program executed in the computer of the arc welding robot in the present embodiment uses the torch rotation angle determined in advance so as to reduce the movement of the basic three axes as the total moving point of the welding line coordinate system. A rotation angle storage unit that stores information corresponding to P and a rotation angle reading unit that reads out the rotation angle storage unit corresponding to the next movement point P from the rotation angle storage unit may be used.

  It can also be applied to applications where welding is performed while weaving the welding torch.

DESCRIPTION OF SYMBOLS 1 Base 2 Base 3 1st arm 4 2nd arm 5 Wrist member 6 Welding wire 7 Welding torch 8 Torch bracket 10 Controller 11 Input conversion unit 12 Output conversion unit 13 Input / output unit 14 Storage unit 15 Calculation unit 16 Signal Bus 17 Teaching box 18 Base 20 Arm 20a Arm tip 21 Rotating cone

Claims (2)

Base of the pivot axis of the arm, the three axes of the arm shaft of a second swing shaft swings relative to the first swing axis and the first pivot shaft to swing with respect to said pivot axis, and, Six degrees of freedom comprising an arm rotation shaft that is a rotation shaft of the second swing shaft, a wrist swing shaft that swings with respect to the arm rotation shaft, and a wrist rotation shaft that is a rotation shaft of the wrist swing shaft. a multi-joint robot having, with respect to the at the distal end of the articulated robot arm, the torch body is provided at a position deviated from the axis of the wrist rotation axis, the axis of the wrist rotation axis, fed from the torch body Weaving method for arc welding robot having welding torch set so that delivery direction of welding wire intersects and torch tip which is tip of welding wire is positioned on axis of wrist rotation axis So ,
The torch tip of the welding torch is the origin, the traveling direction along the welding line at the tip of the torch is the Xm axis, the right and left direction with respect to the welding line is the Ym axis, and the axis is the outer product of the Xm axis and the Ym axis. In the first welding line coordinate system with the Zm axis, the rotation angle around the Xm axis is the torch inclination angle,
In the second weld line coordinate system in which the first weld line coordinate system is rotated by the torch inclination angle, the axis corresponding to the Ym axis is the Ym ′ axis and the axis corresponding to the Zm axis is the Zm ′ axis. The rotation angle around the Ym ′ axis is the torch advance angle,
In the third weld line coordinate system in which the second weld line coordinate system is rotated by the torch advance angle, rotation about the Zm ″ axis when the axis corresponding to the Zm ′ axis is the Zm ″ axis When the angle is the torch rotation angle, and the center axis of the welding torch coincides with the Zm ″ axis,
Said articulated with each axis of the robot, the torch tip of the welding torch is moved along the welding line, periodically to move to the left and right with respect to the welding line the torch head at a predetermined frequency to when performing weaving operation to swing, the welding torch as movement of the tip portions of the arm by the weaving operation is minimized, the torch rotation angle, using the respective axes of the articulated robot A method of weaving an arc welding robot, characterized by changing. Base of the pivot axis of the arm, the three axes of the arm shaft of a second swing shaft swings relative to the first swing axis and the first pivot shaft to swing with respect to said pivot axis, and, Six degrees of freedom comprising an arm rotation shaft that is a rotation shaft of the second swing shaft, a wrist swing shaft that swings with respect to the arm rotation shaft, and a wrist rotation shaft that is a rotation shaft of the wrist swing shaft. An articulated robot having
Wherein at the distal end of the articulated robot arm, the torch body is provided at a position deviated from the axis of the wrist rotation axis, relative to the axis of the wrist rotation axis, the forwarding direction of the welding wire fed from the torch body A welding torch set so as to intersect and a torch tip which is a tip of the welding wire is set on the axis of the wrist rotation axis ;
The torch tip of the welding torch is the origin, the traveling direction along the welding line at the tip of the torch is the Xm axis, the right and left direction with respect to the welding line is the Ym axis, and the axis is the outer product of the Xm axis and the Ym axis. In the first welding line coordinate system with the Zm axis, the rotation angle around the Xm axis is the torch inclination angle,
In the second weld line coordinate system in which the first weld line coordinate system is rotated by the torch inclination angle, the axis corresponding to the Ym axis is the Ym ′ axis and the axis corresponding to the Zm axis is the Zm ′ axis. The rotation angle around the Ym ′ axis is the torch advance angle,
In the third weld line coordinate system in which the second weld line coordinate system is rotated by the torch advance angle, rotation about the Zm ″ axis when the axis corresponding to the Zm ′ axis is the Zm ″ axis When the angle is the torch rotation angle, and the center axis of the welding torch coincides with the Zm ″ axis,
Said articulated with each axis of the robot, the torch tip of the welding torch is moved along the welding line, periodically to move to the left and right with respect to the welding line the torch head at a predetermined frequency When performing a weaving operation that swings the arm, the torch rotation angle is changed using each axis of the articulated robot so that the amount of movement of the tip of the arm due to the weaving operation is minimized. An arc welding robot having a control device for controlling an articulated robot.