KR101010775B1 - Method for automatic tracking of welding line through arc-sensor calibration - Google Patents

Abstract

The present invention relates to a welding line automatic tracking technology through the arc sensor calibration, and to determine the distance and the feeding speed between the welding member and the torch to sample the current measured through the plate welding, and the arc sensor modeling formula from the sampling current and determination information By deriving the interpolation formula between the reference current of the arc sensor modeling formula and the current measurement sensor output value measured during welding, the arc sensor calibration is performed based on the interpolation formula. According to the present invention, the performance of the arc sensor can be improved by calibrating the current measurement sensor of the automatic welding robot, thereby enabling more accurate welding line following.

Automatic welding robot, current measuring sensor, arc sensor, welding line

Description

Automatic welding of welding line through arc sensor calibration {METHOD FOR AUTOMATIC TRACKING OF WELDING LINE THROUGH ARC-SENSOR CALIBRATION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding technology of a robot, and more particularly, to an automatic welding line tracking method using an arc sensor calibration suitable for performing accurate calibration of a current measuring sensor during automatic welding of an robot using an arc sensor.

As is well known, the arc sensor is a welding torch mounted at the end of the robot in robot welding, which is used to follow the welding line, and uses a change in current value due to a change in the distance between the welding torch and the base metal.

Hereinafter, a welding process and an arc sensor will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram of a welding process welded by a general welding robot.

Referring to Figure 1, the welding robot 100 is composed of a plurality of arms 102 are combined. The torch 104 is coupled to and mounted on the end of the arm 102. In addition, a first power line 110 that is drawn out of the welding machine 108 to apply a welding current is mounted at the end of the arm 102 of the welding robot 100, and a welding rod 106 and a lower portion of the welding rod 106. The base material 114 which is welded by the arc at regular intervals is provided. This base material 114 is located on the upper part of the work bench 116 which has the conductor property which the electric current is well conducted. The work table 116 is provided with a second power supply line 112 corresponding to the first power supply line 110 to conduct current. The second power supply line 112 and the first power supply line 110 are led into the welding machine 108, and the base material 114 and the robot arm positioned on the work bench 116 by the current applied to the welding machine 108. An arc is generated between the electrodes 106 mounted on the 102. The electrode 106 melts due to the exothermic action of the arc, thereby joining the base material 114. At this time, the welding robot 100 welds the base material 114 by weaving while following the welding line 118 along the welded portion of the base material 114 to perform bead welding.

On the other hand, the welding machine 108 is connected to the robot controller 120 that performs the control of the welding robot 100, the robot controller 120 is the welding torch 106 mounted on the welding robot 100 is weld line 118 Robot driving operation unit 122 that performs arithmetic control to weave and move along the groove of the robot, and the welding machine 108 is driven to sample the current when the welding voltage and current are output, and the robot moves using the sampled current. The arc sensor unit 124 for calculating a correction value to be included.

In the case of gas metal arc welding (GMAW) using consumable electrodes, the measured current value decreases as the distance between the welding torch and the base material increases, and the welding current value increases as the distance decreases. Using this principle, the welding seam is measured by measuring the current value while the torch moves between the grooves.

In the automatic welding of the robot using the arc sensor, the arc sensor unit 124 needs a current value output by the welder. The current measuring sensor measures the current output from the welder 108 in various ways. The output range of the current measuring sensor is generally about DC 0-10V. Here, the current measuring sensor may be included in the arc sensor unit 124 or included in the robot controller 120.

After all, the actual current output from the welding machine 108 is between 0 ~ 600A and the output value of the current measuring sensor measuring this is about 0 ~ 10V, the current value required by the arc sensor unit 124 is present between 0 ~ 600A Since it is a value, it has a correlation between the output value of the current measurement sensor and the current required by the arc sensor unit 124, which is called arc sensor calibration. In order to calculate the welding torch compensation value for following the welding line during robot welding, it is necessary to obtain accurate current value, but it is difficult to accurately calibrate the current measuring sensor. 2 is a graph of the calibration accuracy of the conventional calibration method and the current measurement sensor.

2, reference numeral 200 denotes a rated calibration graph of a current measuring sensor, and reference numeral 202 denotes a rated calibration graph according to a conventional conventional calibration method. Conventional conventional calibration method 202 is a reference value of the output value of the current measuring sensor obtained by performing a plurality of plate welding under various welding conditions (welding current) and another calibrated current measuring sensor, respectively. After the representation as points, the correction is performed by interpolating a straight line that minimizes the distance between the points.

In the prior art calibration method operating as described above, a separate calibrated current measuring sensor is required, and it must go through several repetitive processes for each automatic welding robot, and after performing welding on the flat plate instead of the actual welding member There was a downside to that. In addition, the actual current measuring sensor has a problem that the slope of each straight line is different in many cases with respect to the welding current range without being calibrated linearly as shown by reference numeral 202.

Accordingly, the present invention provides a welding line automatic tracking method through the arc sensor calibration that can perform the correct calibration of the current measurement sensor that can influence the performance of the arc sensor when performing the automatic welding using the arc sensor.

In another aspect, the present invention provides a welding line automatic tracking method through the correction of the arc sensor that can be performed by the automatic correction of the arc sensor through the accurate calibration of the current measuring sensor when performing the automatic welding using the arc sensor.

According to one embodiment of the present invention, a process of sampling a current measured through plate welding by determining a distance (TWD) and a feeding speed between a welding member and a torch, and deriving an arc sensor modeling equation from the sampling current and determination information And deriving an interpolation equation between a reference current of the arc sensor modeling equation and an output value of a current measurement sensor measured during welding, and performing arc sensor calibration based on the interpolation equation.

In the present invention, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention can increase the performance of the arc sensor through the calibration of the current measuring sensor of the automatic welding robot, through which there is an effect that can enable more accurate welding line following.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

In the present invention, when performing automatic welding using an arc sensor, the arc sensor is corrected through the accurate calibration of the current measuring sensor and through this, the welding line is automatically followed.

This will be described in detail with respect to the correct calibration method of the current measuring sensor through the following examples.

3 is a flowchart illustrating an arc sensor modeling procedure according to a preferred embodiment of the present invention.

Referring to FIG. 3, plate welding is performed under a plurality of welding conditions determined in advance in a pre-sampling step, and current values in each welding condition are stored using a pre-calibrated current measuring sensor. In step 300, the feeding speed (FR), the distance between the welding member and the torch (tool-to-workpiece distance, hereinafter referred to as TWD) are determined. The condition (SO) and the number of samplings are determined. Will be set. Accordingly, when the number of feeding speed is n and the TWD condition is m, the number of sampling may be n * m times.

If the predetermined sampling number is greater than or equal to K in step 302, the plate is welded according to the K th sampling condition in step 304 to store the current value CR in each welding condition. After sampling the measured current value, adding the sampling number 1 to K, the process returns to step 302, and the operation is repeated until K becomes larger than the predetermined sampling number.

That is, if the predetermined number of sampling is less than K in step 302, the process proceeds to step 306. In step 306, the sampled current value (CR), the feeding rate (FR), and the TWD (SO) value are as follows. Calculate the coefficients (a0, a1, a2, a3) of the arc sensor modeling equation. The calculation method uses Least-Square-Method. That is, it may be SO = a0 + a1 * CR + a2 * FR * CR + a3 * FR.

As described above, the arc sensor modeling equation derived from FIG. 3 may be applied under similar welding conditions. When the reference TWD and the feeding speed FR are determined during arc sensor calibration, the corresponding current value CR may be calculated. Can be. 4 is a flowchart illustrating a calibration procedure of a current measuring sensor according to a preferred embodiment of the present invention.

Referring to FIG. 4, in operation 400, a welding line in a vertical direction or a horizontal direction is determined, and reference welding conditions (voltage and feeding speed) of the welding line are determined. In addition, TWD is determined, and K for checking the number of sampling is set to one.

In step 402, if the sampling frequency is greater than or equal to K, the welding line is welded at step 404, and the output value from the current measuring sensor is sampled. This value will have a value of 0-10V as mentioned previously. Thereafter, after adding the sampling number 1 to K, the process returns to step 402. The operation is repeated until K becomes larger than the predetermined sampling number.

In this case, if the number of sampling is greater than or equal to K in step 402, sampling is performed again in step 404. If the number of sampling in step 402 is less than K, the process proceeds to step 406. In step 406, sampling is performed. The interpolation equation is obtained by applying the least-squares method to the reference current value (CR) obtained by substituting the reference TWD (SO) and the reference feeding speed (FR) into the current measurement sensor output value (IS) and the arc sensor modeling equation. Calibration of the sensor can be performed.

As described above, the method of calibrating the current measuring device and the arc sensor through the procedures of FIGS. 3 and 4 are performed on one robot initially performing the operations described with reference to FIG. 3 when a plurality of automatic welding robots perform automatic welding. Since the current measurement sensor can be calibrated by the method described in FIG. 4 for all the robots after setting up the general arc sensor relational expression, it is not necessary to perform a number of flat plate welding for each robot like the conventional welding machine calibration method. . In practice, welding of vertical welding line and welding line of horizontal welding line are very different (for example, 250A vertical reference current and 400A horizontal reference current). The calibration can be performed more accurately than the error of calibration.

5 is a graph showing a calibration result of a current measurement sensor according to a preferred embodiment of the present invention.

Referring to FIG. 5, an interpolation equation like reference numeral 500 may be obtained in a vertical welding reference current section, and an interpolation equation like reference numeral 502 may be obtained in a horizontal welding reference current section. It can be seen that closer to actual welding conditions than snacks.

As described above, in the present invention, when performing automatic welding using the arc sensor, the arc sensor is corrected through the accurate calibration of the current measuring sensor, and the welding line is automatically followed.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

1 is a configuration diagram of a welding process welded by a general welding robot,

2 is a rated calibration graph of a conventional calibration method and a current measurement sensor,

3 is a flowchart illustrating an arc sensor modeling procedure according to a preferred embodiment of the present invention;

4 is a flowchart illustrating a calibration procedure of a current measuring sensor according to a preferred embodiment of the present invention;

5 is a graph showing a calibration result of a current measurement sensor according to a preferred embodiment of the present invention.

<Explanation of Signs of Major Parts of Drawings>

100: welding robot 104: welding rod

106: welding wire 108: welding machine

114: base material 118: welding line

120: welding robot controller 124: arc sensor unit

Claims (5)

delete Sampling the current measured through plate welding by determining the distance between the welding member and the torch (TWD) and the feeding speed; Deriving an arc sensor modeling equation from the sampling current and the determination information; Deriving an interpolation equation between the reference current of the arc sensor modeling equation and an output value of the current measurement sensor measured during actual welding; And performing an arc sensor calibration based on the interpolation formula, The arc sensor modeling equation, the welding line automatic tracking method through the arc sensor calibration, characterized in that for calculating the coefficient of the arc sensor modeling equation from the sampling current, TWD, the feeding speed by the least-squares method. Sampling the current measured through plate welding by determining the distance between the welding member and the torch (TWD) and the feeding speed; Deriving an arc sensor modeling equation from the sampling current and the determination information; Deriving an interpolation equation between the reference current of the arc sensor modeling equation and an output value of the current measurement sensor measured during actual welding; And performing an arc sensor calibration based on the interpolation formula, The process of deriving the interpolation formula, Determining the welding line, the TWD, the voltage and the feeding speed of the welding line; Sampling the measured current value from the current measuring sensor by performing the actual welding; Performing an interpolation operation between the sampled sensor output value and the reference current of the arc sensor modeling equation Welding line automatic tracking method through the arc sensor calibration, comprising a. Sampling the current measured through plate welding by determining the distance between the welding member and the torch (TWD) and the feeding speed; Deriving an arc sensor modeling equation from the sampling current and the determination information; Deriving an interpolation equation between the reference current of the arc sensor modeling equation and an output value of the current measurement sensor measured during actual welding; Performing arc sensor calibration based on the interpolation equation; Deriving the arc sensor modeling equation and applying the same to a plurality of automatic welding robots; Process of performing arc sensor calibration by deriving interpolation formula for each automatic welding robot Welding line automatic tracking method through the arc sensor calibration, comprising a. The method of claim 3, wherein The process of deriving the interpolation formula, Welding line automatic tracking method through the arc sensor calibration, characterized in that performed for each welding line.

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