an algorithm for the welding torch weaving control of arc welding robot.
by：kingtool aluminium machinery2020-05-08
I. The development of robot welding technology has made remarkable achievements and is one of the main application fields of industrial robots. S. Hong et al.  Many advantages and disadvantages of different robot welding techniques are discussed. Arc welding is considered to be one of the most promising applications of intelligent robots. This situation first stems from the low labor productivity under harsh environmental conditions caused by high temperature and smoke generated by the welding process. Second, arc welding is the third largest working category after assembly and processing in the metal manufacturing industry . Robot weaving welding technology is a typical application in the arc welding industry, which encourages in-depth research and development of complex control algorithms and applications. Specific software packages. J. Wang et al.  A new swing arc system has been developed to achieve high quality narrow gap welding at low cost. The system uses the motor of the hollow shaft to directly rotate the Micro Bend the conductive rod and then loop around the axis of the torch to weave the arc. The method of robot trajectory planning can also be used for robot welding control, but there are few studies on this method at present. This paper presents an algorithm to realize the welding head knitting control of electric welding robot by using this method. In the application of arc welding, task planning is the concrete embodiment of geometry and process parameters. The task planning scheme for arc welding robots must use the following sections. I. Definition of welding scheme; 2. Welding process specifications for each Weld; Third, sports planning. Motion Planner is used to generate motion schemes that can be executed by the robot controller 4]. Sports programs are generally implemented by means of teaching programming. However, for complex weaving welding, especially the formulaLayers and layers Pass Welding, has been in 【5]-. One drawback to using this method is that a large number of teaching control points are required in the programming process. Based on the method of robot trajectory planning, this paper uses an algorithm for welding torch weaving control to solve this problem. The algorithm includes a new formula for calculating the position of the trajectory, and can produce accurate and continuous weaving paths along various welds, including complex combinations of straight lines and arcs. Instructional programming can easily identify these welds that contain very few teaching points. Therefore, the algorithm can reduce the programming time of robot welding application. For weaving welding robots, the programming of the weaving path is usually divided into two steps. First, the aweld line is decided by the teaching plan. This weld is both the center of the weaving path and the offset reference for multiple weldsLayers and layersPass welding. The weld line is discrete into a set of 3D (three-dimensional)positions. Second, the algorithm is used to calculate the set of 3D positions, and the inverse motion model of the welding robot is used to lift it from the Descartes space to the joint space. 3]. The robot controller updates the mobile reference coordinate system in each cycle to achieve the desired motion path. The rest of this article is organized as follows. The first part is true. Determine the time of the weaving path to move the reference coordinate system and from the actual TCP ( Tool Center Point)-orientation. Section 3 provides a formal description of the weaving control algorithm. In section 4, a large number of experiments are carried out to verify the algorithm. The fifth part summarizes the main contributions of this article. II. Coordinate transformation problem. The reference coordinate system uses Descartes coordinates to describe the position of the robot path is an important step in simplifying programming. The next step is to use the Descartes reference system. A reference system consisting of position and direction offsets is often referred to as a frame or transformation in robotics. As shown in the figure. Usually six degrees of freedom ( Freedom) The robot has four reference systems such as World frame W, Foundation frame B, target frame o and tool frame. In the application of a single robot, the common root of all reference systems is called the World frame W, which is usually selected on the basis of the robot. e. Bottom frame B. In many welding tasks, the robot\'s tooltip must be moved to several different positions on the same welding object. When defining the position of the robot weaving path relative to the World frame W, by modifying the position of the reference system, all positions on the welded object can be translated together. As shown in the figure. 2. The weaving path and the weld are relative to the W frame. The point [p. sub. 1]and [P. SUB. 2] Can be K. Zhang interpolation algorithm [:7]. Because a straight line can be determined by two teaching control points, the weld can be easily realized through teaching. However, weaving paths cannot be achieved using the same method. The position of the weld corresponds to the position of the welding path one by one, just like the vector [sup. w][q. sub. 1]and [sup. w][q. sub. 1]. All positions of the weaving path can be achieved by modifying the positions of some reference coordinate systems, such as frame 1, frame 2, frame 3. . . , Without changing the position of the target command, This coordinate transformation can be described in the following equation :[ Mathematical expressions that cannot be reproduced in ASCII], (1)[sup. w][q. sub. 1]= [sup. w][q. sub. 1]+ [sup. w][q. sup. 1. sub. 1], (2)[sup. w][q. sub. 1]= [sup. 1][q. sub. 1], (3)where [sup. w][q. sub. 1] the position vector of the weaving path relative to the world coordinate system. [sup. w][q. sup. 1. sub. 1] Called tracking vector. [ Non-reproducible mathematical expressions] Called tracking position, I. e. The origin of the Roboticactivated reference coordinate system. No offset rotation]sup. w][q. sup. 1. sub. 1]= [ Non-reproducible mathematical expressions] For offsets and rotations, their relational expressions will be described in section 3. The left superscript \"W\" is the reference coordinate system pointing to the quantity, and the right superscript represents the starting point of the vector ( The space shows that the starting point is the origin of the reference coordinate system) The right subscript represents the end point of the vector. When the active reference coordinate system of the robot keeps moving from framel to frame2, to frame ,. . . , Continuous weaving path based on Weld can be obtained. B. Definition of tool framework. P. Pashkevin describes in detail the definition of welding frames for [linear and circular welded joints]8]. In order to adapt to various welding joints, a similar method was used in this study to determine the tool frame. For linear welded joints, with specific TCP- As shown in the figure, the direction is defined. 3. For round welded joints, from the ever-changing TCP- Ensure the direction of the welding path to the tangent [X. sub. T]- As shown in the figure, the axis of each point4: --the [X. sub. T]- Orientation of the shaft along the Weld; --the [Z. sub. T]- The shaft specifies the close direction of the welding pipe ( Welding joints are normal); --the [Y. sub. T]- Axis complete right- The hand-oriented frame thus shows the direction of \"weaving. Three coordinate axis unit vectors can be calculated with rotation matrix [sup. w. sub. T] R from actual TCPorientation [ Mathematical expressions that cannot be reproduced in ASCII], (4)where [sup. w. sub. T]n is the Xx- Axis unit vector]sup. w. sub. T]O isthe [Y. sub. T]- Axis unit vector [? ? ][sup. w. sub. a]is the [Z. sub. T]-Axisunit vector. [sup. w. sub. T] R is a tool frame rotation matrix relative to the World frame. The variables a, B, and c are the three Orah angles of tcp-orientation. The symbols in the matrix are described as follows :[ Mathematical expressions that cannot be reproduced in ASCII]. (5)III. Algorithm of weaving control. Weaving without offset and rotation ,【sup. w][q. sup. 1. sub. 1]= [ Mathematical expressions that cannot be reproduced in ASCII]. As long as the tracking vector 【sup. w][q. sup. 1. sub. 1] , Calculation, by activating the reference coordinate system of the arc welding robot whose origin is tracking position [can realize the welding path Mathematical expressions that cannot be reproduced in ASCII]. During the welding process, the direction of the vibration is along the two-direction vector [p. sub. bi] Determined by the path speed unit vector [v. sub. path]and the[Z. sub. T]- Axis unit vector [sup. w. sub. T]a. The equation is as follows [p. sub. bi]= [v. sub. path]x [sup. w. sub. T]a (6)where [v. sub. path] Defined [v. sub. path]= [[v. sub. x]/[ Absolute value]v. sub. x]][v. sub. y]/[ Absolute value of Y][v. sub. z]/[ Absolute value]v. sub. z]]](7)where [sup. w. sub. T] A has the same meaning as in (4). Binormalvector [p. sub. bi] the uniform unit vector perpendicular to the path speed vector and [Z. sub. T]-vector. So, tracking vector [sup. w][q. sup. 1. sub. 1] You can go through the following equation 【sup. w][q. sup. 1. sub. 1]= [delta]x A x [p. sub. bi], (8) The parameter A indicates the actual oscillation amplitude. Theparameter [delta] Refers to the actual amplitude of the oscillation function. The range of [delta]is [-1,1]. There are three types of weaving including sine oscillation function, triangular oscillation function and ladder oscillation function. Sine oscillation]delta]is defined as[delta]= sin[[phi]], where [phi]is phase angle. Triangular oscillation]delta] The definition is as follows :【 Mathematical expressions that cannot be reproduced in ASCII](9) For ladder oscillation, the definition of 5 is as follows :[ Mathematical expressions that cannot be reproduced in ASCII](10)B. The offset of the weld welding operation plan can be divided into four types according to the number of welds and the number of layers, such as table 1 . When the weld edge [moves]Y. sub. T]- Axis of tool frame, many Layer and single Realized by welding. When the weld moves along the [line]Z. sub. T]- Shaft of tool frame, this welding operation is defined as singleLayers and layersPass weld. If both [Y. sub. T]-axis and[Z. sub. T]- There is an offset to the shaft. This welding operation is called multipleLayerand Multi-Pass welding . The offset vector can be obtained by the following equation [sup. w][q. sub. os ]= [v. sub. path][P. sub. bi][sup. w. sub. T]a]x[sup. T][q. sub. os]](11) Where are the three unit vectors [v. sub. path], [p. sub. bi],[sup. w. sub. T] Definition of A and in (6). The vector[sup. w][q. sub. os] Representing the actual yoffset and z- Offset of multipleLayerand Multi- Compared to the World frame, by welding. The vector[sup. T][q. sub. os] Representing the actual yoffset and z- Offset of multipleLayerand Multi- Relative to the tool frame, defined as [by welding [sup. T][q. sub. os]= [[[x. sub. t][y. sub. t][z. sub. t]]. sup. T]. (12)Generally, x- Offset printing is not put into practice because x- Offset astarting- Point offset, not welding path offset. As shown in the figure. 5. The tracking position of the weld line offset can be obtained through followedding 【 Mathematical expressions that cannot be reproduced in ASCII]. (13)C. The rotation of the weaving path as shown in the figure 6. In addition to the weld offset, it is also necessary to rotate around the coordinate axis of the tool frame to ensure that it is adapted to various welding joints. In this article, the weaving path revolves around X-axis and Z- Axis of tool frame, around Y-rotation Axisis\'s unimplemented proposal. For X- Rotation, that is, rotation around the path speed vector with Weld offset and X- Rotation can be obtained by the following expression [ Mathematical expressions that cannot be reproduced in ASCII]. (14)For Z- Tracking position of rotation, Weld offset and z- Description of rotation as follows [ Mathematical expressions that cannot be reproduced in ASCII], (15)where [sup. w][q. sub. os] Indicates weld offset. [R. sub. x] Represents the 3 × 3 rotation matrix around the path speed unit vector [v. sub. path]. [R. sub. z] Represents the 3 × 3 rotation matrix around [Z. sub. T]- Axis unit vector [sup. w. sub. T] A of tool framework. Transition matrix [R. sub. x], [R. sub. z] The definition is as follows :【 Mathematical expressions that cannot be reproduced in ASCII], (16)[ Mathematical expressions that cannot be reproduced in ASCII], (17) Where are the parameters:beta] the rotation angle around the speed unit vector of the path. The parameter [gamma] The rotation angle around is- Axis unit vector of tool frame. [v. sub. x], [v. sub. y], [v. sub. z],[sup. w. sub. T]a, [sup. w. sub. T][a. sub. y], [sup. w. sub. T][a. sub. z] The element of the vector is [v. sub. path]and [sup. w. sub. T]a. The symbolsc[beta], s[beta], c[gamma], s[gamma] Defined :[ Mathematical expressions that cannot be reproduced in ASCII], (18)IV. Experimental verification. In order to verify the effectiveness of the algorithm, a software package was developed on the six degrees of freedom robot control system developed by Jiangsu Automation Research Institute. The experimental environment is shown in the figure. 7. The parameters of the experiment are described as follows: weaving amplitude (10 milimeters); Weaving frequency (0. 5 Hz); The types of weaving are set to sine, triangle and trapezoid respectively; The parameters for offset and rotation are set to zero. Get the weld line by teaching two points (i. e. Starting point and end point of weld line). Figure 3 shows the experimental data of three weavings. 8-Fig. 10, including the time history of the tracking location, 2D (two-dimensional) TCP location diagram. As can be seen from the figure8(a), Fig. 9(a)and Fig. 10(a) When A = 10, the maximum weaving amplitude of the first element X of the tracking position is 10. The result of weaving can be seen from the figure. 8(b), Fig. 9(b)and Fig. 9(b). The X-coordinate of the weld line is 1049, and the oscillation function of the algorithm can accurately generate curves, triangular curves and ladder curves, respectively. B. Weaving experiments were performed with Weld offset due to page limitations, and only records of sine weave data were provided. The parameters of the experiment are described as follows: weaving amplitude (10 millimeters); Weaving frequency (0. 5Hz); The weaving method is set to sine; the Y-offset (-80 millimeters); theZ-offset (30 millimeters); Set the rotation parameter to zero. The weld is obtained by the same experimental method, with no setup and rotation. As shown in the figure. 12Fig. 13, including the time history of the tracking vector and the tracking position, the 2D map of the TCP position. As can be seen from the figure11(a), Fig. 11(b), Fig. 12(a)and Fig. 12(b) When there is a weld offset in weaving, the tracking position produces an offset element, such as Y- The offset in the figure is 80. 11(b), Z- The offset in the figure is 30. 12(b). The result of weaving can be seen from the figure. 11(c)and Fig. 12(c). Y coordinate of weld from-440 to -520. The Zcoordinate of the weld varies from 778 to 808. The oscillation function of the algorithm can produce two sine curves accurately. Photos of the results of the weaving experiment are shown in the figure. 13. C. Experiment with X-weavingrotation or Z- The parameters of this experiment are described as follows: weaving amplitude (10 millimeters); Weaving frequency (0. 5 Hz); The weaving method is set to sine; the X-rotation (30 degrees); theZ-rotation (30 degrees); The parameter of the offset is set to zero. The weld line was obtained by the same experimental method with no offset and rotation. A record of sine weaving data is provided. As shown in the figure. 14-Fig. 15, including the time history of the tracking position and the 2d map of the TCP position. As shown in the figure. 14(a)and Fig. 15(a) , Tracking position (12)and (13). The result of weaving with X- Rotation can be seen from the figure. 14(b) , The woven plane rotates 30 degrees around x- Axis with Y coordinate-440. The result of weaving with Z- Rotation can be seen from the figure. 15(b) , The weaving path rotates 30 degrees around Z-axis. V. Conclusion The experimental results show that the welding nozzle weaving control algorithm based on complex weld meets the control of 3 weaving paths and realizes complex spatial offset and rotation. It is possible to achieve multiple Layer and single By setting the weaving parameters in the robot program, the linear and circular joints pass through the welding path. By using the developed software package, it is also possible to reduce the programming time of the welding application. The special contribution of this paper is to describe the motion reference coordinate system based on coordinate transformation theory, which is a key problem in motion control of welding robot control system. When the robot starts the corresponding reference coordinate system, the expected weaving path can be realized by executing the robot motion command. The algorithm has been applied in the software module of JARI robot control system. This application greatly reduces the teaching time of welding robot programming. The future research work will focus on the analysis of saving teaching programming time and improving efficiency. Received the manuscript on March 15, 2014; Accepted October 10, 2014REFERENCES T. S. Hong, M. Ghobakhloo, W. \"Robot Welding Technology\", integrated material processing, roll. 6, pp. 77-99,2014. [Online]. Available: P. Sicard, M. D. IEEE Trans, \"a method of expert robot welding system \". The first volume of the system, man and control theory. 18,1988, pp. 204-222. [Online]. Available: J. Y. Wang et al. , \"Swing arc system for narrow gap GMAwelding\", ISIJ International, Volume 152, no. 1, pp. 110-114, 2012. [Online]. Available: G. Bolmsjo, G. Nikoleris in Conf, \"task planning for welding applications \". Proc. IEEE Int. Conf. Page 1993, systems, humans and control theory, systems engineering for Human Service515-519. [Online]. Available: S. B. Pan, B. H. Jia, X. W. 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Dornfeld, \"the robot coordinates the trajectory planning of the motion with the positioning station. I. \", IEEE Trans. Path specification, robotics and automation, Volume 16, pp. 735-745, 1990. [Online]. Available: text-liang Zhu (1), Fu-sheng Ni (2), Cao-gen Hong (3)(1) College of port coast and offshore engineering, Hehai University, Nanjing 210098, China (2) Dredging technology engineering research center, He Hai University, Changzhou 213022, China (3) Jiangsu Institute of Automation, Lianyungang, 222006, China. If you are looking for convenient, affordable , kingtool aluminium machinery brings plethora of options to suit your requirements and budget both. Check Kingtool Aluminium Machinery for more details. Kingtool Aluminum Doors and Windows Machinery Co., Ltd. would like to provide our customers with as near perfect protection, as near perfect service as is humanly possible and to do so at the lowest possible cost.' 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