JPH05285656A - Welding robot controller - Google Patents

Abstract

PURPOSE:To maintain the satisfactory welding quality while contact between an electrode and base metals caused by overshooting is prevented by decreasing the follow-up sensitivity in the direction where the electrode and the base metals are brought close to each other and increasing the sensitivity in the opposite direction. CONSTITUTION:Two kinds of follow-up sensitivities of a robot are set. In the control sensitivity to maintain the arc length constant by following-up undulation of the base metals 6, etc., a gain is decreased when a TIG torch 2 is corrected in the direction to approach the base metals 6 (gain 1) and the gain is increased when the torch 2 is corrected in the direction to separate from the base metals 6 (gain 2). Consequently, while a state that the gain is to be decreased is suppressed to the minimum, the occurrence of a situation that the electrode comes into contact with the base metals 6 can be obviated surely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding robot provided with a sensor means for detecting a position change of a workpiece during teaching and during playback, and more particularly to a robot controller suitable for a Tig welding robot. ..

[0002]

2. Description of the Related Art One type of arc welding by a robot is Tig welding in which a tungsten electrode is used and welding is carried out in an inert gas shield, which is widely used for welding aluminum and stainless steel. By the way, when performing Tig welding using a robot, it is desirable to keep the arc length constant in order to guarantee the welding quality. Therefore, in the Tig welding robot, the processing target at the time of teaching and playback is Detects the change in the position of the object, corrects the robot path from this detection result, and determines the arc length, that is, the robot and the welding target (workpiece or base metal).
A technique for controlling the distance between the arcs to be constant is used. Further, at this time, by utilizing the correlation between the arc voltage and the arc length shown in FIG. 6, the position change is detected from the arc length, and the arc length is A technique for controlling the position of the robot so as to be constant is sometimes used, and this technique is called a robot arm AVC (Arc Voltage Controll).

The principle of this constant arc length control will be described with reference to FIG. 7. In FIG. 7, 2 is a torch for Tig welding, and 6 is a work. The robot path at the time of teaching is a broken line. It is assumed that the actual position of the work 6 at the time of playback is distorted as shown by W in the figure, while it is shown by P.

Therefore, in this case, the robot control device (not shown) takes into consideration the change in the arc voltage at this time and the work 6
Position and torch height (ΔL1, ΔL2, ΔL3)
That is, the operating position of the robot is controlled as indicated by the solid line P ′ so that P becomes constant.

By the way, as a conventional technique of this robot arm AVC, the disclosure of Japanese Patent Laid-Open No. 59-94582 can be mentioned. In this conventional technique, as shown in FIG. 8, the welding torch direction (arc length) is used. ) Position control so that the difference between the arc voltage and the reference voltage is always zero. That is, as shown in FIG. 8, first, the arc voltage Vi is detected (block 80). Next, a difference voltage ΔVi is calculated by subtracting a predetermined preset reference voltage Vb from the arc voltage Vi (block 81). Then, the difference voltage ΔVi is multiplied by a constant G having a predetermined value which is also set in advance to obtain a detection amount D (block 82),
Finally, the detected position D is used to calculate the corrected position of the robot, that is, the position of the robot shown by the solid line P'in FIG. 7 (block 83).

Here, the constant G is referred to as a gain because it is a quantity that determines the tracking sensitivity when the robot makes a correction operation.

[0007]

By the way, in the Tig welding robot, depending on the type of work and the type of power source, the welding torch electrode is taught so as to be very close to the base metal during welding.
(Teaching) may be necessary.

However, in the above-mentioned prior art, no particular consideration is given to the relationship between the tracking sensitivity of the robot and the path correction operation. Therefore, as in the case of Tig welding,
If the distance between the electrode and the base metal is taught very close, the electrode may come into contact with the base metal and weld during the welding operation. Therefore, the robot's tracking sensitivity should be sufficiently high. However, the arc length control performance was deteriorated, and there was a problem in maintaining the welding quality.

In other words, if the tracking sensitivity of the robot is increased,
When the robot path correction is in the direction of approaching the workpiece, the electrode is in contact with the base material due to the overshoot existing in the robot movement control because the distance between the electrode and the base material is small, so the tracking sensitivity is improved. I have no choice but to lower it, while
If the follow-up sensitivity is lowered in this way, the path correction will be delayed, so that the arc length cannot be kept constant and the welding quality will deteriorate.

According to the present invention, there is no risk of the electrode coming into contact with the base metal even in Tig welding, and moreover, a constant control of the arc length is sufficiently obtained and a good welding quality can always be maintained. It is intended to provide a control device.

[0011]

The above object is to use a means for automatically switching the tracking sensitivity of the robot depending on the correction direction at the time of path correction, and to approach the base material where the electrode and the base material may contact. When the correction is made in the direction, the tracking sensitivity of the robot is lowered, and when the correction is made in the direction avoiding the base material, the tracking sensitivity is increased.

In particular, according to the embodiment, two kinds of tracking sensitivities are set as the tracking sensitivities of the robot, and whether the value obtained by subtracting the reference value set in advance from the detection value by the sensor is positive or negative is set. A determination processing unit is provided so that two types of tracking sensitivities can be switched.

[0013]

In the case of correcting the position of the robot in the direction in which the electrode approaches the base material, since the tracking sensitivity of the robot is lowered, there is no risk of the electrode and the base material coming into contact with each other. To correct the robot position in the direction,
Since the follow-up sensitivity is increased, it is possible to suppress a decrease in follow-up property for keeping the arc length constant, and to prevent deterioration of welding quality.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A welding robot controller according to the present invention will be described below in detail with reference to the illustrated embodiments. Figure 2
Shows a system configuration in an embodiment in which the present invention is applied to a Tig welding robot. 1 is a robot (robot body, manipulator), 2 is a torch for Tig welding, 3 is a robot controller, 4 is a Tig welder,
5 is a filler wire feeding control device, and 6 is a work.

The robot 1 is of an articulated type and its tip is
The torch 2 for TIG welding is held on the (wrist), and thereby Tig welding is performed on the work 6. The robot controller 3 has a microcomputer, which has a control function required for teaching processing and playback processing, controls the robot 1, and sends a predetermined control signal to the welding machine 4 and the filler wire feeding controller. No. 5, and the operation required for Tig welding is performed. The Tig welding machine 4 is operated by the torch 2 under the control of the control signal from the robot controller 2.
And a work 6 supply electric power for welding, and the filler wire feeding control device 5 operates the filler wire feeder 7 to feed the filler wire 8 at a predetermined speed during welding. ..

Further, the robot controller 3 has a function necessary for constant control of the arc length for Tig welding during playback, and therefore, during Tig welding, the arc voltage is taken in from the welding machine 4 and a predetermined value is obtained. The process of is executed.

Next, the operation of this embodiment will be described. The arc length constant control is basically executed by the robot controller 3 as described with reference to FIGS. 7 and 8, and the correction amount detected by the sensor is added to the position to be interpolated. The robot position control is performed to a position where the arc length becomes constant by means of the following. First, FIG. 3 shows the processing in this embodiment. Regarding the control direction at this time, as shown in FIG. It is performed for the A vector (vertical direction vector) of the tool attachment coordinate system.

In FIG. 3, the arc voltage, that is, the analog value detected by the sensor, is detected by detecting the welding voltage by the Tig welding machine 4, filtered, and converted into an analog voltage of 0 to 10 V so as to be input. Is becoming

The analog value detected by this sensor is first calculated by A / D.
It is converted (block 30) and subjected to sensor control to calculate the correction amount h (block 31). This process is a process of obtaining the detected amount D from the arc voltage and converting this to the correction amount h, and the arithmetic expression at this time is (Equation 1).

[0020]

[Equation 1]

A in this (Equation 1) indicates the vector A direction in FIG.

Of the sensor control processing in this block 31, the processing for obtaining the detected amount D from the arc voltage is the feature of the present invention, and therefore the details will be described later.

Then, as shown in FIG. 3, in the constant control of the arc length, the correction amount h is calculated by interpolation calculation processing (block 3).
By 2), the interpolation command amount b given from the interpolation command sending process (block 33), that is, added to the robot position,
This is executed by performing a servo control process (block 34).

Next, the sensor control processing, which is a feature of the present invention, will be described.

In this embodiment, as shown in FIG.
When the torch 2 is corrected in the direction in which it approaches the work 6, the gain is lowered, and as shown in FIG. 4B, the gain is increased in the direction in which the torch 2 moves away. This makes it possible to reliably prevent the occurrence of a situation in which the electrode comes into contact with the base material while minimizing the state in which the gain must be reduced. Therefore, the processing shown in FIG. 1 is adopted as the sensor control processing. Here, as will be apparent from comparison with the case of the conventional technique shown in FIG. 8, the portion surrounded by the broken line in FIG. 1 represents the characteristic portion of the present invention.

In the process of FIG. 1, first, in block 10, the A / D converted voltage value Vi is calculated every 10 msec.
The detection process is performed every 78 msec. Next, in block 11, from the detected voltage value Vi to the reference voltage Vb.
Is subtracted to obtain the deviation ΔVi.

In block 12, it is judged whether the deviation ΔVi obtained in the process of block 2 is a positive value or a negative value. First, when the result is judged to be a positive value, the process of block 13 is executed. If yes, on the other hand, if the result is determined to be negative, then the process of block 14 is performed. Here, when the result is a positive value,
In the case of (a) and the result is a negative value, (b) of FIG.
That is the case.

First, in the processing of block 13, the deviation ΔV
i is multiplied by G1 of the two preset gains G1 and G2 to calculate the detection amount D.
On the other hand, in the process of block 14, the deviation ΔVi is multiplied by the gain G2 to calculate the detection amount D.

Here, as these gains, G1 <G
Values are set so that the relationship of 2 holds, and therefore,
In the case of (a) of FIG. 4, the detection amount D is calculated by the small gain G1, and in the case of (b) of FIG.
The detection amount D is calculated by 2.

In block 15, a process of converting the detected amount D into the correction amount h is executed. The arithmetic expression at this time is (Equation 1) as described above.

Therefore, according to this embodiment, as shown in FIG. 4, the gain is lowered when the torch 2 is corrected toward the work 6, and the gain is corrected when the torch 2 is moved away from the work 6. Automatically gains control to increase the gain, and the gain is reduced only when necessary, so that the occurrence of the situation where the torch 2 contacts the work 6 can be reliably eliminated, and the overall gain is increased. Since the deterioration of the arc length can be suppressed to a minimum, there is almost no deterioration in the arc length control performance, and the welding quality can be kept sufficiently good.

[0032]

According to the present invention, in a robot equipped with a sensor, the gain can be automatically switched depending on the correction direction at the time of path correction. Therefore, the present invention can be applied to Tig welding to bring the electrode and the base metal very close to each other. Even in the case of the teaching, it is possible to prevent the electrode and the base material from being welded to each other, and thus, stable welding can be always performed.

Further, according to the present invention, the gain of the sensor can be sufficiently increased as a whole, so that the constant control of the arc length can be accurately obtained and the welding quality can be easily maintained. be able to.

[Brief description of drawings]

FIG. 1 is a flowchart showing a sensor control process in an embodiment of a welding robot controller according to the present invention.

FIG. 2 is a system configuration diagram showing an example of a welding robot apparatus to which an embodiment of the present invention is applied.

FIG. 3 is a flowchart showing a sensor control process and an interpolation process in one embodiment of the present invention.

FIG. 4 is an explanatory diagram of an operation according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing respective control directions during constant arc length control in one embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between arc length and arc voltage.

FIG. 7 is an explanatory diagram of a constant arc length control operation.

FIG. 8 is a flowchart showing a conventional example of sensor control processing.

[Explanation of symbols]

 1 Robot (robot body, manipulator) 2 Welding torch 3 Robot controller 4 Welder 5 Filler wire feeding controller 6 Workpiece (base material, workpiece)

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[Procedure amendment]

[Submission date] September 17, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Front Page Continuation (72) Inventor Sumio Washio 7-1-1 Higashi Narashino, Narashino, Chiba Prefecture Hitachi Keiyo Engineering Co., Ltd.

Claims (1)

[Claims] 1. A welding robot apparatus of a system which comprises a sensor means for detecting a positional change of a workpiece during teaching and during playback and which corrects a robot path based on a detection result of the sensor means. A means for switching the tracking sensitivity of the robot according to the correction direction at the time of path correction is provided, and the moving speed of the robot becomes slower when the correction direction is closer to the object to be processed, and faster when it is away from the object to be processed. A welding robot controller characterized by being configured as follows.