JPH0671668B2 - Torch angle control method in groove automatic copying control by arc sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an object to be welded in which a welding line provided with a groove is bent or an actual welding line is deviated from a teaching point of a robot. On the other hand, the present invention relates to a torch angle control method in groove automatic copying control when welding is performed using a welding robot equipped with a high-speed rotating arc welding torch.

[Prior Art] Utilization of arc sensor technology based on the rotation of a welding arc as a groove automatic copying control in consumable electrode type arc welding is disclosed in, for example, JP-A-60-174270 and JP-A-62-248571.
Known by the issue.

7 (a) and 7 (b) are explanatory views of a groove tracking control method using a conventional rotary arc sensor, and at the same time, the definition of the control direction is given. In the figure, reference numeral 1 denotes a welding torch having an electrode nozzle rotated by a motor 2 and attached to the tip of a welding robot arm (not shown). 3 is torch 1
A welding wire, which is automatically fed with a given amount of eccentricity at the nozzle tip of 4, is an arc, 5 is a groove formed in the workpiece 6, and in the case shown, the welding line 10 is a straight line. Has become. 7 is a weld bead. Further, in the following, the x-axis refers to the axial direction of the groove 5, and the y-axis refers to the axial direction (height direction) of the torch 1. The z-axis represents the traveling direction of the welding torch 1 (welding traveling direction).

With such rotary arc sensor technology, the arc 4
Welding current Ia and arc voltage Ea are detected every 1 rotation of
By controlling the integrated value of the difference (Ia-Io) between the detected welding current Ia and the reference value Io of the welding current to be always zero, the welding torch 1 is separated from the welding torch by the workpiece (torch). Height) can be corrected in the y-axis direction so as to be constant (constant arc length control), and the difference between the detected arc voltage Ea and the reference value Eo of the arc voltage (Ea-Eo)
By controlling so that the area surrounded by the same phase angle φ on the left and right with respect to the front point Cf in the z-axis direction, that is, the difference (S _L -S _R ) between the values integrated on the left side and the right side is always zero,
The welding torch 1 can be corrected in the x-axis direction so that the target position of the welding torch is at the groove center. As a result, welding can be performed while the torch 1 automatically follows the groove 5.

Therefore, in the conventional rotary arc sensor, the torch 1 is x
The position of the torch 1 is only corrected in the axial and y-axis directions, and the torch 1 is moved at a constant speed in the z-axis direction.

[Problems to be Solved by the Invention] Therefore, when the angles θx and θy formed by the z-axis and the welding line 10 are large as shown in FIGS. 8 (a) and 8 (b), the welding speed in the z-axis direction is Since it is constant, the broken line portion 10a,
The welding speed at 10b is substantially higher, which results in inadequate welding results.

Therefore, for example, when welding an object to be welded as shown in FIG. 8 by an articulated welding robot or the like, in addition to the welding start point Ps and the end point Pe, points P ₁ , P ₂ , P where the welding direction changes There is also a problem that teaching work takes a lot of time, such as teaching ₃ etc. and changing the welding speed at those bending points.

Furthermore, when welding a bent fillet welding line 10 as shown in FIGS. 9 (a) and 9 (b), if the welding torch 1 is operated without changing the posture, the receding angle αa is generated when welding the polygonal line portion 10a.
Occurs, an advance angle αb occurs when welding the polygonal line portion 10b,
Moreover, since these receding angles and advancing angles change, welding defects sometimes occur. Here, the torch angles αa and αb are x-
Welding torch 11 and welding line 10 in the z plane or yz plane
The angle formed by the normal line 12 in Fig. 4 is referred to as the receding angle when a rearward tilt angle occurs with respect to the welding direction, and conversely the forward angle when a forward tilt angle occurs. In FIG. 9, 6a is a lower plate and 6b is a standing plate.

Further, as shown in FIG. 9C, when the inclination angle θ is large, the welding torch 1 and the standing plate 6b may interfere with each other.

Therefore, for example, when welding a member such as a corrugated panel of a container, mechanically changing the torch angle or teaching with a welding robot has dealt with it. The method has a problem that the teaching work requires a great deal of labor and time.

The present invention has been made in order to solve the problems as described above. Even when the welding line is bent in the z-axis direction, the welding torch of the welding torch can be formed by using the high-speed rotating arc sensor technology. The torch angle in the automatic groove chamfering control by the arc sensor that can automatically weld the polygonal line portion while properly correcting the traveling direction at the same welding speed and keeping the torch angle always constant with respect to the reference welding direction The purpose is to provide a control method.

[Means for Solving the Problems] In order to achieve the above object, the torch angle control method in the groove automatic copying control by the arc sensor according to the present invention uses a welding robot equipped with a high-speed rotating arc welding torch. When welding an object to be welded whose welding line is bent with respect to the z-axis, the welding is performed by the following procedure. That is, (1) the welding arc is rotated at a high speed of 10 to 200 times per second.

(2) The welding current Ia, the arc voltage Ea, and the rotational position of the arc with the forward Cf point in the welding advancing direction as the reference position are detected.

(3) The detected welding current Ia and the reference value Io of the welding current
The difference (Ia-Io) is integrated by ΔY for each rotation of the arc, and (4) the difference (Ea-Eo) between the detected arc voltage Ea and the reference value Eo of the arc voltage. , A region surrounded by the same phase angle φ (where 5 ° <φ <180 °, preferably 5 ° <φ <90 °) about the point Cf, that is, the L side (left side) and the R side (right side) ), The difference (S _L -S _R ) between the values integrated by
Let be X.

(5) Then, the welding advancing direction, which is taught in advance to the welding robot, is corrected in the axial direction of the welding torch by an amount determined by the value of ΔY for each one revolution of the arc or each control pitch of the welding robot, and at the same time. The welding direction defined by correcting the welding direction and the axial direction of the welding torch by an amount determined by the value of ΔX is defined as a reference welding direction, and (6) and The welding speed is always kept at a predetermined value, and (7) each time, the reference welding direction is detected by the ΔX and ΔY, and the angle of the welding torch is always kept constant with respect to the reference welding direction. To control.

[Operation] As shown in FIG. 1, the trajectory control of the welding robot is PTP (P
CP (Continuous Pass) control of oint to Pont) teaching, and control points G ₁ , G ₂ , ..., Gn are previously defined at the same pitch between two teaching points Ps and Pe. This control pitch is usually the arc rotation cycle, and the welding arc rotation speed N is kept high in the range of 10 to 200 Hz. The magnitude of the welding speed can be maintained at a preset value by keeping the distance between the control points constant.

Now, when the welding line is bent between the two teaching points Ps and Pe, only the welding advancing direction is maintained while keeping the welding speed constant for each revolution of the arc or for each control pitch of the welding robot. The welding direction vector is modified so that it changes little by little. The technology of the high speed rotating arc sensor is used to correct the welding direction vector.

The welding direction vector is corrected as follows. Welding current Ia, arc voltage Ea and Cf for each revolution of the arc
Since the rotation position of the arc with the point as the reference position is detected, the value (S _I ) obtained by integrating the difference (Ia-Io) between the detected value Ia and the reference value Io for each rotation of the arc is ΔY, Also the detected value
A value (S _{L) obtained} by integrating the difference between Ea and the reference value Eo (Ea-Eo) for each arc revolution for the same transfer angle φ (5 ° <φ <90 °) on the left and right with the Cf point as the center. -S _R ) is ΔX, referring to FIG. 3, the correction amount in the x-axis direction and the y-axis direction at the control point i is x-axis direction correction amount = kx · ΔXi · e y-axis direction correction amount = ky・ It is given by ΔYi ・ e. Where kx and ky are control constants (gain),
e and e are unit vectors in the x-axis and y-axis directions, respectively.

Accordingly, the welding direction vector i that is corrected at the control point i is the last control point (i-1) Welding direction vector fixed in _i-1 and perpendicular thereto the x-axis and y-axis direction of the course correction vector, That is, the above kx · ΔXi · e and ky
・ The direction will be AC, which is the combination of the three vectors of ΔYi ・ e. The direction of the welding direction vector i must be the same, and its magnitude must be the same as the magnitude of the welding speed initially set. Therefore, the welding direction vector i
Is expressed by the following equation.

Where | ₀ | is a preset welding speed in the z-axis direction.

However, the expression (1) is just a basic expression, and in practice, the correction of the welding direction vector may be performed by performing a process such as a weighted average on the welding direction vector of the last several times. In this case, the practical formula is as follows.

However, The welding direction vector is corrected for each revolution of the arc or for each control point according to the equation (2), and the torch angle is controlled so as to be always constant with respect to the reference welding direction every time.
This is because the teaching direction of the welding robot is constant, and the torch angle needs to be changed appropriately depending on the type of the object to be welded such as a corrugated panel. Thus, the magnitude of the corrected welding speed in the welding direction is equal to the preset magnitude of the welding speed in the z-axis direction, and at the distance between the control points, the arc sensor scans in the x-axis and y-axis directions. Since the control is automatically performed, the advancing direction of the welding torch is gradually changed at each control point even if the welding line is bent. Therefore, even if the position of the bending point of the welding line is not taught again, z
A constant welding speed vector from the constant axial welding direction vector and a trajectory correction vector that is perpendicular to the welding direction vector and is determined from the x-axis and y-axis direction detection values detected by the high-speed rotating arc sensor. In addition, by correcting only the welding direction under a constant torch angle, the torch moving direction is automatically changed from the position of the bending point.

[Example] Hereinafter, the control method of the present invention will be described more specifically with reference to the drawings.

FIG. 1 is an explanatory view showing a method of controlling the correction direction of the welding direction vector and the torch angle at each control point. In the figure, two teaching points Ps and Pe are a welding start point and an end point, respectively, which are taught in advance by a welding robot.
If the arc rotation speed N is, for example, 50 Hz and welding is performed between the two teaching points Ps and Pe, the control pitch is 20 ms.
The control points G ₁ , G ₂ , ..., Gn of are determined.

FIG. 2 is an explanatory view of the welding torch attached to the welding robot. The y-axis moving mechanism 18 is attached to the tip of the robot arm 21.
Attached, and the x-axis moving mechanism 14 on the y-axis moving mechanism 18
The welding torch 1 is rotatably supported on the x-axis slide block 15 of the x-axis moving mechanism 14. The torch 1 is rotated by a motor 2 mounted on an x-axis slide block 15 via a gear mechanism 8. The arc rotation position detector 9 is shown in FIG. 7 (b).
Four points of L, Cr, and R are detected based on the Cf point. In the figure, 16 is an x-axis ball screw, 17 is an x-axis motor, 19 is a y-axis ball screw, and 20 is a y-axis motor. The y-axis slide block is not shown.

In addition, a welding circuit 30 is configured between the welding wire 3 and the object 6 to be welded via a power supply tip (not shown), and a welding power source is provided.
31, Welding current detector 32 and arc voltage detector 33 are incorporated. The detector 32 detects the welding current Ia, and the detector 33 detects the arc voltage Ea.

The welding method is arc welding using the high-speed rotating arc welding torch 1 configured as described above, and the welding current Ia and the arc voltage Ea are detected as described above for each revolution of the arc, and x is detected from these detected values. Welding is performed while calculating the correction amount of the torch position in the axial and y-axis directions. It is suitable that the arc rotation speed N = 10 to 200 Hz, the arc rotation diameter D = 1 to 6 mm, and the wire diameter 0.8 to 1.6 mm.

Therefore, returning to FIG. 1 again, the welding direction vector i at an arbitrary control point i can be expressed as follows by modifying the equation (2).

Here, _0: preset welding direction vector _{0 i-1:} 1 previous control points i-1 norm welding direction vector of the i: norm welding direction vector _{0 i-1} to the vertical trajectory correction vector i.e., The trajectory correction vector i is obtained by multiplying a value determined based on the ΔX (= S _L -S _R ) and ΔY (= S _I ) for each rotation of the arc by a constant kx, ky (gain), respectively. And is given in the x-axis direction and the y-axis direction perpendicular to the previous reference welding direction vector ₀ i- ₁ . And, welding the angle of the torch 1 in order to always be constant, taking the direction of the welding direction vector i in the direction of the reference welding direction vector _{0 i-1} in the preceding control points i-1, the _{0 i-1} vector On the other hand, for example, it is kept constant at 90 °. That is, the control point G _1, maintaining a right angle torch angle to the previous norm welding direction vector _00, the sum of only its norm welding vector ₀₀ and the track correction vector _{unidirectional} welding direction vector _{1 (00} + ₁ ) Direction. Then, in the next control point G _2, the torch angle taken at right angles to _one vector and the size the same direction same ₀₁ vectors, modifying only the welding in the direction of ₍₀₁ + _2). Similarly, keep the torch angle constant with respect to the reference welding direction vector ₀ i- ₁ and set only the welding direction to the reference welding direction vector.
By correcting the direction of the sum of ₀ i- ₁ and the trajectory correction vector i ( ₀ i- ₁ + i), only the advancing direction of the welding torch 1 is changed little by little at the same welding speed and the same torch angle. ing. In this direction, it is possible to accurately follow the groove of the welding line 10 that is actually bent.

Further, the welding direction vector i averages the reference welding direction vector of the last several times in order to prevent hunting. The torch angle is held constant with respect to the welding direction vector i thus modified, but the torch angle does not need to be controlled frequently, for example, every 5 °.

Thus, the welding torch 1 gradually advances from the control point G ₁ to each of the control points along the polygonal line portion 10a, and is held at a constant torch angle β as shown in FIG. Therefore, the polygonal line parts 10a and 10b are 3 with respect to the z-axis.
Even if it is inclined by more than 0 °, good welding can be performed by accurately following the groove along the polygonal line portion with a constant torch angle β and a constant welding speed.

Next, FIG. 5 and FIG. 6 are control block diagrams in the x-axis and y-axis directions, respectively.

In FIG. 5, reference numeral 41 denotes an arc rotational position detector, which is an arc rotational position Cf, R, Cr, for each 90 ° rotational angle of the welding torch 1.
Four points L (see FIG. 7 (b)) are detected. Reference numeral 42 is an arc voltage Ea detected by the arc voltage detector 33 for each revolution of the arc, and reference numeral Eo is a preset reference voltage Eo, which are input to the differential amplifier 44, respectively. 45
Is a switching logic circuit for determining the integration area by inputting signals from the rotational position detector 41 and the integration area setting circuit 46, and 47 is a switch for integrating the L area 35 in FIG. It operates according to the L region command of the circuit 45 and sends the arc voltage difference signal (Ea-Eo) amplified by the differential amplifier 44 to the integrator 50 as a plus. Four
Reference numeral 8 denotes a switch for integrating the R region 36 in FIG. 7 (b), which operates according to the R region command of the switching logic circuit 45, and is the arc voltage difference signal (Ea-Eo) amplified by the differential amplifier 44. Invertor 49 to make it negative and integrator 5
Send to 0.

The integrator 50 operates according to the integration area command of the switching logic circuit 45, integrates the signals input through both switches 47 and 48, and sends the integrated value difference (S _L -S _R ) to the x-axis correction calculator 51. . Reference numeral 52 denotes an x-axis gain setter, which inputs a preset x-axis gain kx to the calculator 51 and calculates a correction amount kx · ΔX in the x-axis direction. When this value is positive, the welding torch is corrected to the L side, and when it is negative, it is corrected to the R side. Reference numeral 53 is an x-axis controller for correcting the welding torch position in the x-axis direction.

In FIG. 6, 54 is the arc 1 by the welding current detector 32.
The welding current Ia, 55 detected for each rotation is the preset reference welding current Io, 56 is the differential amplifier, 57 is the arc 1
An integrator for integrating the welding current difference signal (Ia-Io) for each rotation, 58 is a switching logic circuit, which receives a signal from the rotation position detector 41 and operates the integrator 57 for each rotation signal. 59 is a y-axis correction calculator, which is the integrated value from the integrator 57
S _I and y preset by the y-axis gain setter 60
Input the axis gain ky into the calculator 59, and adjust the correction amount in the y-axis direction ky.
-Calculate ΔY. Reference numeral 61 is a circuit for determining whether the correction amount is positive or negative. When the value is positive, the welding torch position is low, so the torch is corrected to the rising side. On the contrary, if the torch is negative, the torch position is high and the torch is corrected to the descending side. Reference numeral 62 is a y-axis controller for correcting the welding torch position in the y-axis direction.

With the circuits shown in FIGS. 5 and 6, the x-axis and the y-axis, respectively.
The correction amount in the axial direction is obtained, the correction amount is sent to a welding speed control circuit (not shown), and vector control is performed so that the welding speed and the torch angle are constant according to the equation (3).

[Effects of the Invention] As described above, according to the present invention, even with respect to an object to be welded in which a welding line having a groove is bent, welding is performed using a welding robot having a high-speed rotating arc welding torch. Welding with excellent welding quality and bead shape can be performed while walking the speed and torch angle to the prescribed values while gradually changing only the welding advancing direction and accurately following the groove. In addition to being possible, there is an effect that the teaching work by the robot can be greatly simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a torch angle control method according to the present invention, FIG. 2 is a configuration diagram of a welding torch attached to an arm of a welding robot, FIG. 3 is a principle diagram showing a method for correcting a welding direction vector, and FIG. The drawings are explanatory views showing a state in which the torch angle is kept constant with respect to the bent welding line according to the present invention, and FIGS. 5 and 6 are respectively the x-axis used in the groove automatic copying control method of the present invention. Copy control block diagram and y-axis copy control block diagram, FIGS. 7A and 7B are explanatory views of a groove automatic copying control method using a conventional rotary arc sensor, and FIG.
FIGS. 9A and 9B are explanatory views showing a bent welding line which is a target of the present invention, and FIGS. 9A to 9C are explanatory diagrams showing a relationship between a torch angle and a welding line. . 1 …… Welding torch 3 …… Welding wire 4 …… Arc 5 …… Groove 6 …… Workpiece 10 …… Welding line Ps …… Welding start point (teaching point) Pe …… Welding end point (teaching point) G ₁ , G ₂ , ..., Gn ...... Control point ₁ , ₂ , ..., i ...... Welding direction vector ₀₀ , ₀₁ , ..., ₀ i- ₁ ...... Reference welding direction vector ₁ , ₂ , ..., i ...... Orbit correction vector

Front page continuation (72) Kenichiro Yamashita, 20 Ishigane Co., Ltd., Toyama City, Toyama Prefecture.

Claims (1)

[Claims] 1. When welding an object to be welded having a groove by a welding robot having a high-speed rotating arc welding torch, (1) welding is performed while rotating the welding arc at a high speed of 10 to 200 times per second. (2) Welding current Ia, arc voltage Ea and welding direction forward C
The rotational position of the arc with the point f as the reference position is detected, respectively, and (3) the detected welding current Ia and the reference value Io of the welding current are detected.
The difference (Ia-Io) is integrated by ΔY for each rotation of the arc, and (4) the difference (Ea-Eo) between the detected arc voltage Ea and the reference value Eo of the arc voltage. , The area surrounded by the same phase angle φ around the point Cf, that is, on the L side (left side)
And the difference (S _L -S _R ) between the integrated values on the R side (right side) is ΔX, and (5) the welding progress direction taught to the welding robot in advance is set for each one revolution of the arc or the control pitch of the welding robot. Is corrected in the axial direction of the welding torch by an amount determined by the value of ΔY, and at the same time, by an amount determined by the value of ΔX, a direction perpendicular to both the welding advancing direction and the axial direction of the welding torch (hereinafter referred to as opening The welding direction determined by the correction is referred to as the front width direction) is used as the reference welding direction, and (6) and the magnitude of the welding speed is always maintained at a predetermined value. Of the welding torch, by controlling the angle of the welding torch so that it is always constant with respect to this reference welding direction, the groove is automatically tracked and at the same time is always appropriate for the welding line. toe Torch angle control method in groove automatic scanning control by arc sensor and performing welding while maintaining the angle.