KR19980057552A - Method and apparatus for controlling the angle of welding torch of arc welding robot - Google Patents

Abstract

The present invention relates to a control method and apparatus for angle correction of a welding torch when welding arcs in an arc welding robot. The method of the present invention is an arc welding robot that requires arc welding by arc interpolation. Determining a movement path of the torch according to the x and y coordinates of the arc in order to maintain the welding torch angle at. A second step of detecting an error α between the current welding angle and the predetermined optimum welding angle which proceeds along the movement path determined in the first step; Comprising a third step to maintain the optimum welding angle by compensating the error α detected in the second step, the apparatus to which the method is applied comprises the teaching box 40, the ROM 42, the RAM 43, It comprises a microprocessor 44, a servo system 45, a motor 46, a robot 47, a welding torch 48, the present invention uses a welding position (x, y) correction angle By calculating the position of the robot and the position of the welding torch can be automatically adjusted. In addition, since the compensation loop is performed only when the welding angle is out of the desired range (40 ° to 50 °), unnecessary correction operation is removed, so that the welding speed is also increased.

Description

A method and an apparatus for controlling angle of weling torch in Arc welding robot

The present invention relates to the angle correction of a welding torch when welding a circle in an arc welding robot. In particular, the value of the welding torch close to the optimum angle (45 °). The present invention relates to a welding torch angle control method and apparatus of an arc welding robot, which automatically corrects a position of a correction angle by obtaining a correction angle using a trigonometric function of the x and y coordinates of each point of an arc.

In general, the control unit of an industrial robot stores work content received from a human, reproduces it, sends control commands to an arm or a hand, and executes a work. Teaching work to robots is equivalent to a computer program, but in addition to these programs, teaching methods unique to industrial robots are used. The teaching method of controlling the robot can be roughly divided into a playback control method and a sequence control method. The sequence control method is a simple on-off type control device, in which a sequence of tasks is programmed on a pin board and the like is read in sequence to move a robot's hand. In the playback control method, the operator sets the robot to teach mode, creates a work program, and operates a switch of the teach box before moving the robot to move the hand to a predetermined position. . Here, when the memory button is pressed, the positional information of each movable part is stored, and various information such as the value of each axis of movement of the representative point of the path of the robot's hand is stored in the memory in turn. Now, in the play mode in which the work is performed, the robot reads the position information from the memory in order according to the start signal of the operator and operates the control system to perform the work. In addition, the hand path of the robot includes a point to point (PTP) control that prints only a point of changing direction and a continuous path (CP) control that follows a continuous path. The CP control is used for robots such as arc welding or painting. In this case, the points are closely controlled along the target path to control them to be connected continuously. In this control method, when the arc welding robot actually performs the work, the angle between the welder torch and the welding surface is an important parameter. As shown in FIG. 1, the angle θ of the welding torch should be kept constant at 45 ° at all times to achieve a desirable welding. You will get a result.

For example, when welding a straight line, the angle of the welding torch can be set in advance before the operation and the fixed angle can be maintained.However, when the curve such as an arc needs to be welded, the angle between the welding torch and the reference plane changes frequently. A feedback task is needed to detect and correct the problem. Conventional angle correction, which solves such a necessity, has a problem in that a troublesome and skilled adjuster needs to monitor the work of the robot because the adjuster teaches and corrects through a teach pendant.

Accordingly, the present invention has been made to solve the above problems, the present invention provides a control method and apparatus for automatically maintaining the welding angle θ to approximate the optimum value by detecting the angle of the welding torch every sample. Its purpose is to.

In order to achieve the above object, the method of the present invention, in order to maintain a constant welding torch angle in the arc welding robot to weld the arc by the circular interpolation method, the movement path of the torch according to the x and y coordinates of the arc The first step of determining

Compensating the error α detected in the second step, the second step of detecting the error α of the current welding angle and the predetermined optimal welding angle proceeds along the movement path determined in the first step to determine the optimum welding angle It is characterized by consisting of a third step to maintain.

The apparatus of the present invention for achieving the above object, the teaching box for transmitting the arc welding command in the arc welding robot to weld the arc by the circular interpolation method, a memory for storing the x and y coordinates of the arc, The movement path of the welding torch is determined according to the x and y coordinates, and a compensation value to be compensated at a predetermined optimum welding angle is calculated as the inverse tangent of the x and y coordinates, and corresponds to the compensation value. A microprocessor for calculating a mechanical setpoint, a servo system for converting the setpoint to a current, and a welding torch for maintaining the torch angle at an optimum welding angle by a motor driven according to the current.

1 is a view showing the angle between the welding surface and the welding torch when welding,

2 is a view showing a welding torch angle of a robot welding a circle;

3 is a view for explaining a method for obtaining a welding angle to be corrected in x, y coordinates in FIG. 2 according to the present invention;

4 is an overall system configuration of the arc welding robot to which the present invention is applied,

5 is a view for explaining the direction of the welding torch located in each quadrant of the arc according to the present invention;

6 is a flowchart for controlling arc welding according to the present invention.

Explanation of symbols on the main parts of the drawings

40: teaching box 41: terminal 42: ROM

43 RAM 44 Microprocessor (CPU)

45 servo system 46 motor 47 robot

48: welding torch

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a method of detecting a welding torch angle when drawing an arc will be described. FIG. 2 is a view showing a welding torch angle of a robot welding a circle. The first quadrant is circular interpolation, and the first, quadrant A, B, C, D, and E arcs are welded using the point A as the starting point. In this case, the welding angle is set to maintain 45 ° at point A, but it is out of 45 ° at points B, C, D and E. For example, the welding angle θ for welding the point D is an angle between the tangent at the point D and the welding torch, which corresponds to the welding angle θ = 45 ° + α. Here, the angle α is an angle corresponding to the correction angle to be corrected.

Now, it will be described with reference to FIG. 3 that the correction angle α can be obtained by the x coordinate and the y coordinate of the point D. FIG.

Point D in FIG. 3 is the same position as point D in FIG. 2, and the welding torch position in FIG. 2 is shown in FIG. 3 as the actual position 45 ° away from the reference line passing through point D, and 45 ° away from the tangent passing through point D. The point is represented by the ideal position as the optimal welding position. If point D is the angle β between the baseline and the normal, the angle between the baseline and the tangent line is (90 ° –β). That is, the compensation angle α is just (90 ° -β). Therefore, the compensation angle α can be obtained using the x, y coordinates of the point D as shown in Equation 1 below.

As in Equation 1, if the x, y coordinates of the melting point is known, the angle to be compensated can be obtained as an inverse tangent function. When applied to the system, the coordinates of (x, y) are stored in the lookup table, and this value is read from the lookup table and calculated as shown in Equation 1 to obtain the compensation angle α, and the control unit corresponds to the compensation angle α. It is commanded to correct by a value, and the attitude | position may be changed so that the torch position of a robot may be 45 degrees.

4 is an overall system configuration diagram of the arc welding robot to which the present invention is applied. The present invention relates to a teaching box 40 for transmitting a command of an operator, a terminal 41 serving as an interface between the teaching box and a main board, and a main board. The microprocessor 44 which is in charge of the operations required to control the ROM 42, the RAM 43, the ROM 42, the RAM 43, and perform various commands, which store basic programs and control data mounted in the board. And a servo system 45, a motor 46, a robot 47, and a welding torch 48.

When the operator issues an arc welding command by the circular interpolation method through the teaching box 40, the command is transmitted to the main board through the terminal 41, and in the main board, various commands related to the arc welding stored in the ROM 42 are provided. Data (including the x coordinate and y coordinate of the welding point) is downloaded to the ram 43, and the microprocessor 44 determines the movement path of the welding torch according to the x coordinate and the y coordinate, The compensation value to be compensated at the set optimum welding angle is calculated by the inverse tangent values of the x coordinate and the y coordinate, and a mechanical command value corresponding to the compensation value is calculated. The servo system 45 converts the compensation command value of the microprocessor into a current, and the robot is driven by a motor started with the current so that the welding torch angle maintains an optimum welding angle.

Here, it is said that the microprocessor determines the movement path of the welding torch according to the coordinates, and the reason thereof will be described with reference to FIG. 5. Figure 5 is a view for explaining the direction of the welding torch located in each quadrant of the arc according to the present invention, Figure 1 shows a first quadrant and a second quadrant, Figure 5b shows a third and fourth quadrant It was. The position of the robot is different from the quadrants of the arc, which is why the shape of the torch shown in FIGS. 5A and 5B is different. Considering the constraints of the attitude of the robot itself, the movement path and the compensation angle should be determined.

That is, in the present embodiment, the melting point starts from four division points of each quadrant that is divided into four arcs, and when welding one quadrant, the starting point is point A and clockwise in the order of points B, C, D, and E. When welding is performed, the second quadrant is welded clockwise with the starting point as the point G. When the third quadrant is welded, the starting point is welded counterclockwise with the point G, and when the fourth quadrant is welded, the starting point is the point F and the counterclockwise welding is performed. Also, when the welding angle is as shown in FIG. 5, the compensation angle α is obtained by using the coordinates of each point as shown in Equation 1, and is made as small as the angle corresponding to the compensation angle.

6 shows an algorithm of a circular arc welding controller in which welding is performed by maintaining an error range of 45 ° to 5 ° at an optimum angle of the welding angle to maintain only an approximate value (40 ° to 50 °). As shown in FIG. 6, it is determined whether the arc interpolation welding is performed by receiving the operator's control signal (S1), and if the arc welding, the data including the welding position (x, y) coordinates of the arc from the ROM 42 of the main board. (data) is moved to the RAM 43, and the variable i is initialized to 0. (S2) The variable i represents the number of times the quadrant of one arc is welded by welding the arc into four equal parts.

Now, we need to determine what quadrant the welding point is in and determine the starting point. If it is the first quadrant, the welding torch is moved to point A, and the moving direction of the robot is set clockwise. (S6 to S8) If it is the third quadrant, move the welding torch to point G, and set the traveling direction of the robot counterclockwise. (S9 to S10) If it is the fourth quadrant, The welding torch is moved to the point F, and the moving direction of the robot is set in the counterclockwise direction. θ is detected (S15) and the robot is moved to the next position point (x ', y') to be welded. (S16) The correction angle α is calculated using the position coordinates in the fifteenth step (S15). Is calculated by the microprocessor 44 (S17), and it is determined whether the correction angle α is a value between -5 ° and 5 °. (S18) As a result of the determination of the eighteenth step, -5 ° and 5 ° If not, the attitude of the robot is varied so that the welding torch angle is 45 °, and the next welding position is corrected by repeating from step 16 above. On the other hand, as a result of the determination of the 19th step, if it is a value between -5 ° and 5 °, it is determined whether it corresponds to the end point of an arbitrary quadrant, and if it is not the end point, it moves back to the next welding position repeatedly from the 16th step again. do. If it is an end point, the variable i is increased by 1, and if the variable i is 4, it is determined that the variable i is not 4, and if the value is not 4, the process returns to the third step and then repeats the process of selecting a quadrant. When the variable i reaches 4, the complete arc is completed while maintaining the welding angle of 40 ° to 50 °.

As described above, the present invention has an effect of automatically adjusting the position of the robot and the position of the welding torch by calculating the correction angle using the melting point position (x, y). In addition, since the compensation loop is performed only when the welding angle is out of a desired range, unnecessary correction operation is removed, thereby increasing the welding speed.

Claims (7)

In the control method for automatically maintaining the welding angle θ to approximate the optimum value by detecting the angle of the welding torch every sample, A first step of determining the movement path of the torch according to the x and y coordinates of the arc in order to maintain a constant welding torch angle in the arc welding robot that should weld the arc by the circular interpolation method; A second step of detecting an error α between the current welding angle and the predetermined optimum welding angle which proceeds along the movement path determined in the first step; And a third step of compensating for the error α detected in the second step to maintain an optimal welding angle. The method of claim 1, wherein determining the movement path of the torch according to the x and y coordinates of the arc in the first step includes determining a starting point by determining which quadrant the welding point is in, and setting a moving direction of the robot. Welding torch angle control method of the arc welding robot, characterized in that configured to. The method according to claim 2, further comprising: if the position of the welding point is the first quadrant, moving the starting point to point A and setting the moving direction of the robot clockwise (S3 to S5); If it is the second quadrant, moving the starting point to point G and setting the traveling direction of the robot clockwise (S6 to S8); If it is the third quadrant, moving the starting point to point G and setting the traveling direction of the robot counterclockwise (S9 to S10); If the fourth quadrant, the start to move the starting point to the point F, and the step of setting the direction of movement of the robot in the counterclockwise direction (S12 ~ S14) comprising a welding torch angle control method of the arc welding robot. The method of claim 1, wherein the second step is to detect the current welding angle θ, and the error α of the welding angle (= compensation angle) Welding torch angle control method of the arc welding robot, characterized in that calculated by. 5. The method of claim 4, wherein the current welding angle is taken as an angle between the welding torches based on a tangent to the welding point (x, y). According to claim 1, wherein the third step is to change the welding angle to 45 °, if the error α detected in the second step is out of a predetermined approximation range, and if not, the welding angle is maintained as it is A welding torch angle control method of an arc welding robot, characterized by moving to a welding position. In the control device for automatically holding the welding angle θ to approximate the optimum value by detecting the angle of the welding torch every sample, Teaching box 40 for transmitting the arc welding command in the arc welding robot that should weld the arc by the circular interpolation method; Memories 42 and 43 which store the x and y coordinates of the arc; The movement path of the welding torch is determined according to the x and y coordinates, and a compensation value to be compensated at a predetermined optimum welding angle is calculated as the inverse tangent of the x and y coordinates, and corresponds to the compensation value. A microprocessor 44 for calculating a mechanical setpoint; A servo system 45 for converting the setpoint into a current; Welding torch angle control device of the arc welding robot, characterized in that it comprises a robot system 47 including a welding torch 48 to maintain the torch angle at the optimum welding angle by the motor 46 driven according to the current. .