JPH03114671A - Torch angle control method for groove automatic profile control by arc sensor - Google Patents

Abstract

PURPOSE:To perform welding with excellent welding quality by performing welding while maintaining the welding speed at a specified value and changing the proceeding direction and maintaining a proper torch angle by using a welding robot having a high-speed rotational arc welding torch with respect to materials to be welded with a bent weld line having a groove. CONSTITUTION:A welding arc is rotated at high speed of 10-200Hz by using the welding robot having the high-speed rotational arc welding torch and the rotational position of the arc with a Cf point ahead in the welding proceeding direction as the reference position at a welding current Ia and the welding voltage Ea is detected. A value obtained by integrating the difference (Ia-Io) between the above-mentioned current Ia and a reference value Io of the welding current for every rotation of the arc is defined as y and the difference (SL-SR) between values obtained by integrating the difference (Ea-Eo) between the voltage Ea and a reference value Eo of the arc voltage by the region surrounded by the same phase angles phi (5 deg.<phi<90 deg.) on right and left with the Cf point as a center is defined as x. The welding proceeding direction and the groove width direction are corrected by the values of y and x and size of the welding speed is maintained at the specified value and the welding torch angle is maintained constant.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to welded objects where the welding line with a groove is bent or where the actual welding line is deviated from the teaching point of the robot. In contrast, the present invention relates to a torch angle control method in automatic groove tracing control when welding is performed using a welding robot equipped with a high-speed rotating arc welding torch.

[Prior Art] The use of arc sensor technology based on the rotation of the welding arc as automatic groove tracing control in consumable electrode arc welding is disclosed in, for example, Japanese Patent Laid-Open Nos. 60-174270 and 1983.
2-24.85'7.1.

FIGS. 7(a) and 7(b) are explanatory diagrams of a conventional groove tracing control method using a rotating arc sensor, and also provide definitions of control directions. In the figure, reference numeral 1 denotes a welding torch rotated by a motor 2, which is attached to the tip of a welding robot arm (not shown).

3 is a welding wire that is automatically fed eccentrically to the nozzle of the torch 1, 4 is an arc, and 5 is a groove formed in the workpiece 6. In the illustrated case, the welding line 10 is a straight line. ing. 7 is a weld bead. In addition, below,
The y-axis refers to control in the width direction of the groove 5, and the y-axis refers to control in the axial direction (height direction) of the torch 1. The two axes represent the direction in which the welding torch 1 moves (welding direction).

If such rotating arc sensor technology is used, arc 4
The welding current I and arc voltage E are detected every rotation of the welding current Ia and the reference value I of the welding current.
The welding torch 1 can be corrected in the y-axis direction (constant arc length control) by controlling the integral value of the difference (I - I) from Difference between arc voltage E and reference value E of arc voltage (Eaa
OE ) is defined by the region surrounded by the same phase angle φ on the left and right sides centered on the front point C4 in the X-axis direction, that is, the difference (S − S
By controlling R) so that it is always zero, it is possible to correct the welding torch 1 in the X-axis direction. As a result, welding can be performed while automatically causing the torch 1 to follow the groove 5.

However, in the conventional rotating arc sensor, the torch 1 is
The position is only corrected in the axial and y-axis directions, and the torch 1 is moved at a constant speed in the two axial directions.

[Problems to be Solved by the Invention] Therefore, if the angles θ and θ formed by the two axes and the welding line 10 are large as shown in FIGS. 8(a) and 8(b), Since the welding speed is constant, the polygonal line IC
) The welding speed in a, 10b becomes substantially faster, so that a proper welding result cannot be obtained.

■Therefore, when welding a workpiece as shown in Fig. 8 using, for example, an articulated welding robot, in addition to the welding start point P and end point P, welding force S
e Points where the direction changes, p, p2. There was also the problem that the teaching work took a lot of time, such as the need to teach p3 etc. and change the welding speed at those bending points.

■Furthermore, when welding a bent fillet weld line 10 as shown in FIGS. 9(a) and (b), if the welding torch 1 is operated without changing its posture, the receding angle α when welding the bent line portion 10a occurs, and an advancing angle αb occurs when the polygonal line portion 10b is welded, and these receding angles and advancing angles change.
Sometimes welding defects occur. Here, the torch angle α,
αb is the angle between the welding torch 11 and the normal 12 to the welding line 10 in the X-z plane or the y-z plane, and when a backward tilt angle occurs with respect to the welding direction, it is called a receding angle, and conversely, when a forward tilt angle occurs, When this occurs, it is called the forward angle. In addition, the 9th
In the figure, 6a is a lower plate and 6b is a vertical plate.

(2) Furthermore, if the inclination angle θ is large, as shown in FIG. 9(c), for example, there is a possibility that the welding torch 1 and the standing plate 6b may interfere with each other.

Therefore, when welding parts such as corrugated panels for containers, the torch angle could be changed mechanically or teaching could be used with welding robots, but mechanical methods require complicated mechanisms and teaching This method had some problems, such as requiring a large amount of effort and time for teaching work.

The present invention was made to solve the above-mentioned problems, and even when the welding line is bent in two axial directions, the welding torch can be adjusted by using high-speed rotating arc sensor technology. In automatic groove tracing control using an arc sensor, it is possible to automatically weld the polygonal part at the same welding speed while appropriately correcting the direction of travel, and while always keeping the torch angle constant with respect to the standard welding direction. The present invention aims to provide a torch angle control method.

[Means for Solving the Problems] In order to achieve the above object, a torch angle control method in automatic groove tracing control using an arc sensor according to the present invention uses a welding robot equipped with a high-speed rotating arc welding torch. When welding a workpiece whose welding line is bent with respect to two axes, welding is performed using the following procedure. (7) That is, (1) Rotate the welding arc at a high speed of 10 to 200 times per second.

(2) Welding current I, arc voltage E, and welding progress a
Front C4 in direction a
The rotational position of the arc is detected using the point as the reference position.

(3) The difference (1-I) between the detected welding current I and the base heavy chain ■ of the welding current is calculated as 10
Let the value integrated every 0 rotations of a be ΔY, and (4) Furthermore, the difference (E − E ) between the detected arc voltage E and the reference value E of the arc voltage be Oa
O The area surrounded by the same phase angle φ (5°<φ<90°) on the left and right sides around the Cf point, that is, the left side (left side)
and the difference (S, -SR) between the values integrated on the R side (right side) is Δ
Let it be X.

(5) Then, the welding direction that has been previously taught 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 revolution of the arc or for each control pitch of the welding robot, and at the same time The welding direction determined by correcting the welding direction in the direction perpendicular to both the welding progress direction and the welding torch axial direction (groove width direction) by the amount determined by the value of ΔX (8) is the reference welding direction, and ( 6) And always keep the welding speed at a predetermined value, (
7) Every time, the reference welding direction is detected using the ΔX and ΔY, and the angle of the welding torch is controlled to always be kept constant with respect to the reference welding direction.

[Function] As shown in Figure 1, the trajectory control of the welding robot is performed by P T
P (Point To Point) Teaching CP
(Contin-uous Pa5s) control,
Between the two teaching points P and PS e, the control points G1 and G2 are set at the same pitch in advance.
．． ..., G is determined. This control pitch is usually the rotation period of the arc, and the rotation speed N of the welding arc is kept high in the range of 10 to 200 Hz. In addition, the magnitude of the welding speed can be adjusted by keeping the distance between each control point constant.
Can be held at a preset value.

Now, the welding line is between the two teaching points P and P.
e If the welding direction is curved, correct the welding direction vector so that only the direction of welding progress is changed little by little while keeping the welding speed constant for each revolution of the arc or for each control pitch of the welding robot described above. It is. High-speed rotating arc sensor technology is used to correct this welding direction vector.

The welding direction vector is corrected as follows.

Since the welding current ■, the arc voltage E, and the rotational position of the arc with the C4 point as the reference position are detected for each rotation of the arc, the difference between the detected value I and the base heavy chain ■ (I
-I ) for each arc rotation Oa O is the value (S,) integrated, and ΔY is the detected value E
and the reference value E (E − E ) is C4a
oa
.

Left and right equal-transfer angle φ (5°<φ<90°
) is the value (S
-SR) is ΔX, then the amount of correction in the X-axis and y-axis directions at the control point i with reference to the third diagram is the amount of correction in the X-axis direction -k ・ΔX, ・MaX le y-axis direction correction amount It is given by -k ・ΔY1 ・y8y. Here, k and k are control constants x
y (gain), ffi, 7 are the X axis and y
It is a unit vector in the axis e e direction.

Therefore, the welding direction vector v1 corrected at the control point i is the welding direction vector v1-1 corrected at the previous control point (i-1) and trajectory correction vectors in the X-axis and y-axis directions perpendicular to this, In other words, it faces in the direction AC, which is the combination of the three vectors k, .DELTA. The welding direction vector v1 must have the same direction and the same magnitude as the initially set welding speed. Therefore, the welding direction vector v1 is expressed by the following equation.

x (-, , -1+kx・Δxi−'r. 1,・Δ
Y1 ・y8)...(1) /+ +X Here, 1v1 is a preset welding speed in two axial directions.

However, equation (1) is just a basic equation, and in practice, the welding direction vector may be corrected by performing a process such as a weighted average of the previous several welding direction vectors. In this case, the practical formula is as follows.

×(vo1+kx・ΔXl−?8+,・ΔYi−78
)...(2) However, according to formula (2), the welding direction vector is corrected for each arc rotation or each control point, and the torch angle is always kept constant with respect to the standard welding direction each time t19) ( 11) Control so that This is because since the direction taught by the welding robot is constant, it is necessary to change the torch angle as appropriate depending on the type of object to be welded, such as a corrugated panel. Thus, the magnitude of the welding speed in the corrected welding direction is equal to the magnitude of the welding speed in the preset two-axis directions, and at the distance between each control point, the welding speed in the X-axis and Y-axis directions is adjusted by the arc sensor. Since the control is automatic, even if the welding line is bent, the direction of travel of the welding torch is changed little by little at each control point. Therefore, without having to reteach the position of the bending point of the weld line, it is possible to use a fixed welding direction vector in two axes and the X-axis and y-axis that are perpendicular to the welding direction vector and detected by the high-speed rotating arc sensor Based on the trajectory correction vector determined from each detected value of direction, by correcting only the welding direction while keeping the welding speed constant and the torch angle constant, the torch traveling direction is automatically changed from the position of the bending point. .

[Example] Hereinafter, the control method of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a method of correcting the welding direction vector and a method of controlling the torch angle at each control point. In the figure, two teaching points P and P are the welding start and end points, respectively, and are taught in advance by the welding robot. These two teaching points P8. P
If welding is performed with the arc rotation speed N being 50 Hz, for example, the control points G and G with a control pitch of 20 m5
2. ..., Go is determined.

■ Figure 2 is an explanatory diagram of a welding torch attached to a welding robot, in which an X-axis moving mechanism 18 is attached to the tip of the robot arm 21, and an The welding torch 1 is rotatably supported by 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 rotational position detector 9 is designed to detect 4f r points C and R based on point C shown in FIG. 7(b). In the figure, 16 is an X-axis ball screw, ] 7 is an X-axis motor, 19 is a y-axis ball screw, 2
0 is the y-axis motor. Note that the y-axis slide block is not illustrated.

Moreover, a power supply tip (
A welding circuit 30 is configured via a welding power source 31. A welding current detector 32 and an arc voltage detector 33 are incorporated. The detector 32 detects the welding current, and the detector 33 detects the arc voltage E.

The welding method is arc welding using the high-speed rotating arc welding torch 1 configured as described above, in which the welding current Ia and arc voltage E are detected as described above for each revolution of the arc, and from these detected values X Welding is performed before calculating the amount of correction of the torch position in the axis and y-axis directions. In addition, arc rotation speed N-10 to 200 Hz, arc rotation diameter D=
1-6+nm.

A suitable wire diameter is 0.8 to 1.6 mm.

Therefore, referring back to FIG. 1 again, the welding direction vector V at any control point i can be expressed as follows by modifying equation (15) (2).

Here, V: preset welding direction vector V; - welding direction vector of reference 01-1° at the previous control point i-1: reference welding direction vector V; The trajectory correction vector perpendicular to i-1, that is, the trajectory correction vector neck, has values determined based on the above ΔX (=S, -3R) and ΔY (-8,) for each rotation of the arc. It is a constant multiplied by k (gain), and y is the previous reference welding direction vector V. 1-1 in the X-axis direction and the y-axis direction. In addition, in order to keep the angle of the welding torch 1 constant, the direction of the welding direction vector V is set to the base (16) type warm welding direction vector V at the previous control point i-1. Take it in the direction of 1-1, and this 'o
For example, it is kept constant at 90° with respect to the i-1 vector.

That is, at the control point G1, the torch angle is maintained at a right angle with respect to the previous reference welding direction vector V, and only the direction of the welding direction vector v1 is determined by the sum (voo +t, ) direction. Then, at the next control point G2, the torch angle is set to V, which has the same magnitude and direction as the v1 vector. 1 vector, and only the welding direction is corrected in the direction of (voi +7°). Similarly, the torch angle is set to the reference welding direction vector V. 1-1, and only the welding direction is the reference welding direction vector V. By correcting in the direction of the sum (vo, -, +!,) of 1-1 and the trajectory correction vector , only the direction of movement of welding torch 1 is changed little by little at the same welding speed and the same torch angle. That's what I do.

By using such a method, it is possible to accurately follow the groove of the weld line 10 that is actually bent.

Further, the welding direction vector V is obtained by averaging the reference welding direction vectors of several times immediately before hunting. The torch angle is the welding direction vector v modified in this way.
However, it is not necessary to control the torch angle frequently, and it is sufficient to control the torch angle every 5 degrees, for example.

In this manner, the welding torch 1 advances from the control point G1 while gradually changing direction along the polygonal line portion 10a at each control point, and is maintained at a constant torch angle β as shown in FIG. 4. Therefore, the polygonal line portions 10a and 10b are 2
Even when the groove is inclined by 3° or more with respect to the axis, the bent line can be accurately followed at a constant torch angle β and at a constant welding speed, and good welding can be performed.

Next, FIGS. 5 and 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, and arc rotational position C,
Four points R, Cf, and L (see FIG. 7(b)) are detected. Reference numeral 42 indicates an arc voltage E detected by the arc voltage detector 33 every rotation of the arc, and reference voltage 43 indicates a preset reference voltage E, which are input to the differential amplifier 44, respectively. 45 is a switching logic circuit for determining an integral region by inputting signals from the rotational position detector 41 and the integral region setting circuit 46; 47 is a switching logic circuit shown in FIG.
) is a switch for integrating the L region 35 in the switching logic circuit 45, and operates according to the L region command of the switching logic circuit 45, and integrates the arc voltage difference signal (E
-E) Send a O to the integrator 50 as a plus. 48 is Fig. 7(b)
This switch is used when integrating the R region 36 at
-E) is made negative by the inverter 49aO and sent to the integrator 5o.

The integrator 50 operates according to the integral region command from the switching logic circuit 45, integrates the signals inputted through both switches 47 and 48, and sends the integrated value difference (S, -SR) to the X-axis correction calculator 51 (1q ) send. Reference numeral 52 denotes an X-axis gain setting device, which inputs a preset X-axis gain k 2 to the calculator 51 and calculates the correction amount k 2 ·ΔX in the X-axis direction. When this value is positive, the welding torch is corrected to the L side, and when this value is negative, the welding torch is corrected to the R side. 53 is an X-axis controller for correcting the welding torch position in the X-axis direction.

In FIG. 6, reference numeral 54 indicates a welding current detected by the welding current detector 32 for each rotation of the arc.

55 is a preset standard welding current■.

56 is a differential amplifier; 57 is an integrator that integrates the welding current difference signal (I − I) for each rotation of the arc;
O 58 is a switching logic circuit that receives a signal from the rotational position detector 41 and operates the integrator 57 for each rotation signal. Reference numeral 59 denotes a y-axis correction calculator, which includes an integral value S1 by the integrator 57 and a y-axis gain k preset by the y-axis gain setting device 60.

is input to the calculator 59, and the correction amount k in the y-axis direction is obtained.

・Calculate ΔY. 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 and the torch is corrected to the upward side. On the other hand, if the value is negative, the torch is adjusted to the downward direction because the torch position is high. 62 is an X-axis controller for correcting the welding torch position in the y-axis direction.

The circuits shown in Figures 5 and 6 above allow the X-axis and y-axis to be
The amount of correction in the axial direction is determined, the amount of correction is sent to a welding speed control circuit (not shown), and vector control is performed so that the welding speed and torch angle are constant according to equation (3).

[Effects of the Invention] As described above, according to the present invention, a welding robot equipped with a high-speed rotating arc welding torch can be used to weld even workpieces in which the welding line with a groove is bent. While keeping the speed and torch angle at predetermined values, the welding direction can be changed little by little, and the groove can be accurately followed during welding, making it possible to weld with excellent welding quality and bead shape. This also has the effect of greatly simplifying the teaching work performed by robots.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the torch angle control method according to the present invention, FIG. 2 is a configuration diagram of a welding torch attached to the arm of a welding robot, FIG. 3 is a principle diagram showing a method of correcting the welding direction vector, and FIG. The figure is an explanatory diagram showing a state in which the torch angle is kept constant with respect to a bent weld line according to the present invention, and Figures 5 and 6 are respectively the X-axis used in the automatic bevel tracing control method of the present invention. A copying control block diagram and an X-axis copying control block diagram, FIGS.
Figures (a) and (b) are explanatory diagrams showing a bent welding line that is the object of the present invention, and Figures 9 (a) to (c) are explanatory diagrams showing the relationship between the torch angle and the welding line. . 1... Welding torch 3... Welding wire 4... Arc 5... Groove 6... Welded object 10... Welding line P... Welding start point P... Welding end point G1. G2I'. 7.72. ... voo"ol' (Teaching point) (Teaching point) G ... Control point ■, ... Welding direction vector voi-1 ... Reference welding direction vector neck 1, ... 1 neck, ...・Trajectory correction vector 2

Claims (1)

[Claims] When welding a workpiece with a groove using a welding robot having a high-speed rotating arc welding torch, (1) welding while rotating the welding arc at a high speed of 10 to 200 times per second; (2) Detect the welding current I_a, the arc voltage E_a, and the rotational position of the arc with the forward point C_f in the welding direction as the reference position, and (3) Detect the detected welding current I_a and the reference value of the welding current. The value obtained by integrating the difference (I_a - I_o) with I_o for each rotation of the arc is defined as ΔY, and (4) Furthermore, the difference (E_a - E_o) between the detected arc voltage E_a and the arc voltage reference value E_o. , with the same phase angle φ (5° <
The difference (S_L-S_R) between the integrated values on the L side (left side) and the R side (right side) is defined as ΔX, and (5) Welding progress taught to the welding robot in advance. The direction is corrected in the axial direction of the welding torch by the amount determined by the value of ΔY for each revolution of the arc or the control pitch of the welding robot, and at the same time, the direction of welding is adjusted by the amount determined by the value of ΔX. The welding direction determined by correction in the direction perpendicular to both axial directions of the torch (hereinafter referred to as the groove width direction) is the reference welding direction, (6) and the welding speed is always kept at a predetermined value. Keep, (
7) Each time, the reference welding direction is detected using the ΔX and ΔY, and the angle of the welding torch is controlled to always be kept constant with respect to the reference welding direction, thereby automatically forming the groove. A torch angle control method in automatic groove tracing control using an arc sensor, characterized in that welding is performed while always maintaining an appropriate torch angle with respect to a welding line.