JPH074667B2 - Automatic groove tracking control method using 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, it relates to a groove automatic copying control method in the case of welding 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-64-2485.
Known by No. 71.

6 (a) and 6 (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, hereinafter, the x-axis refers to the width 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
Of the welding current I _a and the arc voltage E _a for each rotation of the welding current I _a and the detected welding current I _a and the reference value I of the welding current.
_The welding torch 1 is controlled so that the integrated value of the difference (I _a −I _o ) from _o is always zero, so that the distance between the welding torch and the work (torch height) is constant. Direction (constant arc length control), and the difference (E _a −E _o ) between the detected arc voltage E _a and the reference value E _o of the arc voltage can be calculated as the forward point C in the z-axis direction. _The welding torch 1 is controlled by controlling such that the area surrounded by the same phase angle φ on the left and right with respect to _f , that is, the difference (S _L −S _R ) between the integrated values on the left side and the right side is always zero. It can be corrected in the x-axis direction so that the target position of is located 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 θ _x and θ _y formed by the z-axis and the welding line 10 are large as shown in FIGS. 7 (a) and 7 (b), welding in the z-axis direction is performed. Since the speed is constant, the welding speed at the polygonal line portions 10a and 10b becomes substantially high, and therefore an appropriate welding result cannot be obtained. Therefore, for example, when welding an object to be welded as shown in FIG. 7 with a multi-joint welding robot or the like, in addition to the welding start point P _s and the end point P _e , the points P ₁ , P _{2 at} which the welding direction changes , or teach P _3, etc., etc. it is necessary to change the welding speed at their bending point, a lot of time was also a problem that according to the teaching work.

The present invention has been made to solve the above problems, and even when the welding line is bent in the z-axis direction, by utilizing the high-speed rotating arc sensor technology, the welding torch An object of the present invention is to provide a groove automatic tracing control method by an arc sensor capable of automatically welding a polygonal line portion at the same welding speed while appropriately correcting the traveling direction.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the groove automatic tracing control method by the arc sensor according to the present invention uses a welding robot equipped with a high-speed rotating arc welding torch, and a welding line is z. When welding an object to be welded that is bent with respect to the shaft, 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 I _a , the arc voltage E _a, and the rotational position of the arc with the forward C _f point in the welding advancing direction as the reference position are detected.

(3) the difference between the reference value _{I o} of the detected welding current _{I a} and the welding current _(I a -I _o), the integrated value for each revolution of the arc and [Delta] Y, (4) Further, the detection has been the difference between the reference value _{E o} of the arc voltage _{E a} and arc voltage _(E a -E _o), wherein _{C f} point around the phase angles of the right and left same phi (where 5 ° <phi <180
The difference (S _L −S _R ) between the integrated values in the region surrounded by ∘, preferably 5 ° <φ <90 °, that is, the L side (left side) and the R side (right side) is defined as ΔX.

(5) Then, the welding advancing direction taught to the welding robot in advance is corrected in the axial direction of the welding torch by an amount determined by the value of ΔY for each one rotation of the arc or each control pitch of the welding robot, and at the same time. The amount is determined in the direction (groove width direction) perpendicular to both the welding advancing direction and the axial direction of the welding torch by an amount determined by the value of ΔX.

(6) In addition, the magnitude of the welding speed in the welding advancing direction is always kept at a predetermined value.

[Operation] As shown in Fig. 1, the trajectory control of the welding robot is PTP (P
oint to point) CP (Continuous Pass) control, in which the control points G ₁ , G ₂ , ..., G _n are set at the same pitch between the two teaching points P _s and P _e . . This control pitch is usually the arc rotation cycle, and the 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 P _s and P _e , the welding advancing direction is kept constant for each revolution of the arc or for each control pitch of the welding robot described above. The welding method vector is modified so that only the value is changed 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. Since the rotational position of the arc to the reference position welding current I _a and the arc voltage E _a and the C _f points per rotation of the arc is detected, the difference between the detected values I _a and the reference value I _o (I _a-
The value (S _I ) obtained by integrating I _o ) for each revolution of the arc is Δ.
Y, and the difference between the detected value E _a and the reference value E _o (E _a −E
_o) The same transfer angle of the left and right around the C _f point phi (5 ° <
When phi <90 °) region for one integrated value for each rotation (S L _{-S R)} the ΔX arcs, x-axis and y-axis direction of the correction amount at the control point i with reference to FIG. 3 is , X axis direction correction amount = k _x · ΔX _i · _e y axis direction correction amount = k _y · ΔY _i · _e Here, k _x and k _y are control constants (gains), and _e and _e are unit vectors in the x-axis and y-axis directions, respectively.

Therefore, the corrected welding direction vector _i at the control point i is the welding direction vector _i-1 corrected at the previous control point (i-1) and the trajectory correction vectors in the x-axis and y-axis directions perpendicular thereto. That is, the above k _x · ΔX _i ·
and _e, so that the faces of three vectors of _{k y} · _{ΔY i} · _e in synthesized direction AC. And welding method vector
The direction of _i should be the same, and the size should be the same as the size of the welding speed initially set. Therefore, the welding direction vector _i is expressed by the following equation.

Where | _o | 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, If the welding direction vector is corrected for each revolution of the arc or for each control point according to the equation (2), the magnitude of the welding speed in that direction is equal to the preset magnitude of the welding speed in the z-axis direction, and each control is performed. Since the arc sensor automatically controls the x-axis and y-axis copying at the distance between the points, even if the welding line is bent, the advancing direction of the welding torch is gradually changed at each control point. . Therefore, even if the position of the bending point of the welding line is not taught again, a constant welding direction vector in the z-axis direction and the x-axis and y-axis which are perpendicular to the welding direction vector and which are detected by the high-speed rotating arc sensor. By correcting only the welding direction with a constant size from the trajectory correction vector determined from each detected value of the direction, 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 correcting the welding direction vector at each control point. In the figure, two teaching points P _s and P _e are a welding start point and an end point, respectively, and are taught in advance by a welding robot. These two teaching points P
If welding is performed between _s and _Pe with the arc rotation speed N set to, for example, 50 Hz, the control points G ₁ , G ₂ ,
…, G _n is determined.

FIG. 2 is an explanatory view of the welding torch attached to the welding robot. The y-axis moving mechanism 15 is attached to the tip of the robot arm 21.
Attached, and the x-axis moving mechanism 11 on the y-axis moving mechanism 15.
The welding torch 1 is rotatably supported on the x-axis slide block 12 of the x-axis moving mechanism 11. The torch 1 is rotated by a motor 2 mounted on an x-axis slide block 12 via a gear mechanism 8. The rotational position detector 9 of arc, L a C _f points shown in FIG. 6 (b) to the reference, C _r, which is to detect the four points R. In the figure, 13 is an x-axis ball screw, 14 is an x-axis motor, 16 is a y-axis ball screw, and 17 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 I _a and the detector 33 detects the arc voltage E _a .

The welding method is arc welding using the high-speed rotating arc welding torch 1 configured as described above, detecting the welding current I _a and the arc voltage E _a as described above for each revolution of the arc, and detecting these values. Welding is performed while calculating the correction amount of the torch position in the x-axis 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.

Then, returning to FIG. 1 again, the welding direction vector _{i at} an arbitrary control point i can be expressed as follows by simplifying the equation (2).

Here, _o: preset welding direction vector _i: Control points i Keru CP control vector _i: CP control vector d _i perpendicular trajectory correction vector that is, the trajectory correction vector _i, the ΔX per revolution of the arc _(S L _-S R), ΔY a value determined based on (= _{S I),} there are constant _{k x, k y} (gain)
And is given in the x-axis direction and the y-axis direction perpendicular to the CP control vector _i . And the welding direction vector
_By correcting only the direction of _{i to} the direction of the sum ( _i + _i ) of the CP control vector _i and the trajectory correction vector _i , only the advancing direction of the welding torch 1 is gradually changed at the same welding speed. . With such a method, it is possible to accurately follow the groove of the welding line 10 that is actually bent.

Next, FIG. 4 and FIG. 5 are control block diagrams in the x-axis and y-axis directions, respectively.

In FIG. 4, reference numeral 41 denotes an arc rotational position detector, which is an arc rotational position C _f , R, for each 90 ° rotational angle of the welding torch 1.
Four points of C _r and L (see FIG. 6 (b)) are detected. Reference numeral 42 denotes an arc voltage E _a and 43 detected by the arc voltage detector 33 for each revolution of the arc, and reference voltages E _o set in advance are input to the differential amplifier 44. Reference numeral 45 is a switching logic circuit for determining an 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. L of logic circuit 45
It operates according to the region command, and sends the difference signal (E _a −E _o ) of the arc voltage amplified by the differential amplifier 44 to the integrator 50 as a plus. 48 with the switch when integrating the R region 36 in the view the 6 (b), the switching operates by R region command of the logic circuit 45, the difference signal (E _a -E amplified arc voltage by the differential amplifier 44 _o ) is made negative by the inverter 49 and sent to the integrator 50.

The integrator 50 operates by integration area command of the switching logic circuit 45, a signal inputted through the switches 47 and 48 each integrated and sent to the x-axis corrected calculator 51 as the integral value difference (S L _{-S R)} . 52 is an x-axis gain setter, which inputs a preset x-axis gain k _x to the calculator 51,
The correction amount k _x · ΔX in the axial direction is calculated. 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. 5, 54 is the arc 1 by the welding current detector 32.
The welding current _Ia , 55 detected for each rotation is a preset reference welding current _Io , 56 is a differential amplifier, and 57 is the welding current difference signal ( _{Ia- Io} ) for each arc revolution. An integrator 58 is a switching logic circuit, which receives a signal from the rotational position detector 41 and receives an integrator for each rotational signal.
Activate 57. Reference numeral 59 is a y-axis correction calculator, which inputs the integrated value S _I from the integrator 57 and the y-axis gain k _y preset by the y-axis gain setter 60 to the calculator 59 to adjust the correction amount k in the y-axis direction. Calculate _y · 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 and the torch is corrected to the ascending side. On the contrary, if the torch is negative, the torch position is high and the torch is corrected to the down 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. 4 and 5, the x-axis and the y-axis are obtained, 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 becomes 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. It is possible to perform welding with excellent welding quality and bead shape because it is possible to perform welding while keeping the speed at a predetermined value and gradually changing only the welding advancing direction and accurately following the groove. There is an effect that the teaching work by the robot can be greatly simplified.

[Brief description of drawings]

FIG. 1 is an explanatory view of a groove copying control method according to the present invention, and FIG.
FIG. 1 is a block diagram of a welding torch attached to an arm of a welding robot, FIG. 3 is a principle diagram showing a method of correcting a welding method vector, and FIGS. 4 and 5 are diagrams showing a groove automatic copying control method of the present invention. An x-axis copying control block diagram and a y-axis copying control block diagram to be used, and FIGS. 6 (a) and 6 (b) are explanatory views of a groove automatic copying control method using a conventional rotary arc sensor.
7 (a) and 7 (b) are explanatory views showing a bent welding line which is a target of the present invention. 1 ...... welding torch, 3 ...... welding wire 4 ...... arc, 5 ...... groove 6 ...... weld object, 10 ...... weld line P S _...... welding start point (a taught point) P e _...... welding end Point (teaching point) G ₁ , G ₂ , ..., G _n ... Control point ₁ , ₂ , ..., _i ... Welding direction vector ₁ , ₂ , ..., _i ... CP control vector ₁ , ₂ , ..., _i ...... Orbit correction vector

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenichiro Yamashita 20 Ishigane Co., Ltd., Toyama City, Toyama Prefecture (72) Inventor Hajime Hosoi 20 Ishigane Co., Ltd., Toyama City, Toyama Prefecture (56) References, 56 JP-A-64-15288 (JP, A) JP-A-62-248571 (JP, A)

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) The welding current I _a , the arc voltage E _a, and the arc rotation position with the forward _Cf point in the welding advancing direction as a reference position are detected, respectively. (3) The detected welding current I _a and welding current ΔY is a value obtained by integrating the difference (I _a −I _o ) from the reference value I _{o of} each of the arc revolutions, and (4) the detected arc voltage E _a and the reference value E _{o of the} arc voltage. And the difference (E _a −E _o ) between the area and the area surrounded by the same phase angle φ with respect to the point C _f , that is, L
Side (left side) and R side (right side) integrated value difference (S _L −
S _R ) is ΔX, and (5) the welding advancing direction taught to the welding robot in advance is the axial direction of the welding torch by an amount determined by the value of ΔY for each one revolution of the arc or for each control pitch of the welding robot. And at the same time, the amount of correction determined by the value of ΔX in a direction perpendicular to both the welding advancing direction and the axial direction of the welding torch (hereinafter referred to as groove width direction), (6), and A groove automatic tracing control method using an arc sensor, wherein welding is performed while automatically following the groove by always maintaining a magnitude of welding speed at a predetermined value.