Off-Line Programming Design of Robots Based on DXF Files Zhaoxin Chen 1,a, Jiming Yi 1,b*, Jun Liu 1,c, Yanfeng Lin 2,3,d

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1 Advanced Materials Research Submitted: ISSN: , Vol. 1039, pp Accepted: doi: / Online: Trans Tech Publications, Switzerland Off-Line Programming Design of Robots Based on DXF Files Zhaoxin Chen 1,a, Jiming Yi 1,b*, Jun Liu 1,c, Yanfeng Lin 2,3,d 1 School of Mechanical and Automotive Engineering, Xiamen University of Technology, Xiamen, China 2 Key Laboratory of Precision Actuation and Transmission, Fujian Province University 3 Xiamen Siert Robot Systems Ltd, Xiamen, China a zxchen_xmut@163.com, b jmyi@xmut.edu.cn, c liujunsgf@hotmail.com Keywords: DXF file; primitive optimization sequencing; Coordinate calibration; Offline programming Abstract. To solve the problems of low efficiency and inaccurate positions of artificial trial teaching with industrial robots, a path method is developed to precisely control the robots. Based on a study of general and specific DXF file formats and developed in C # programming language, this method proposes a file format converting algorithm to extract the primitive information and optimize the primitives. The set of points optimized will then be transmitted to the robots through Ethernet and conduct the space coordinates calibration to finally generate robot path codes. Simulations and welding experiments prove that the method will greatly reduce the artificial trial teaching time, improve the working efficiency of robots, and it is adapted to the robots welding, cutting, coating and other trajectory path problems,etc.. Introduction Robots have been widely used nowadays since it plays an increasingly important role as more precise and flexible working labors with higher efficiency under the bad environment than human beings. At present, robots are mainly used for welding, assembling, carrying,coating and cutting,etc. Most of the times, The programming method used for the industrialized robots is that of the online programming: the robotic end effector(tcp), by the help of the teaching box, moves to a set of positions needed for operation, and stores the information in proper order. Then by edition, the movements taught by trial can be re-presented.this online programming method is simple and easy to implement, and is applied under the circumstances of simple operation trajectory and mass production. But by this method, reprogramming is constantly needed as long as the task changes. And as the tasks of operation is getting more and more complicated and the range of application wider and wider, this method no longer fits in with the needs of the current multi-type and low-volume flexible manufacturing. The off-line programming technology is thereby developed [1,2]. For online programming no longer fits in with the contemporary needs of multi-type low-volume flexible manufacturing, off-line programming technology are developed and becomes more preferable. Scientific research institutions at home have made great efforts on exploring robots off-line programming technology since 20c80s and made some achievements, such as the RobotStudio offline programming software developed by ABB,roboguide by FANUC, Sim by KUKA and MOTOCOM by MOTOMAN, etc. All relying on robot-making companies abroad [3]. This method is designed to take the place of artificial trail training and makes it less time-consuming. The graphic software AutoCAD is widely used in the mechanical design and manufacture and it can save the DXF format for open source data structure file.all the information about graphics in the DXF files is redacted into ASCII files in accordance with the prescribed form, which can be called by applications redacted in the high-level language and is one of the industry standard in the field of CAD [4,5]. The information extracted from the DXF files can be used in the numerical control programming, but rarely seem in programming of industrialized robots. Based on the careful study of the DXF files, each primitive is read out by the C # Programming software and the optimization of their arrangement is also carried out, so as to produce the orderly and the optimal operation trajectory of the robots. In the actual robot operations, it only needs a simple All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-18/09/16,16:25:19)

2 314 Advanced Manufacturing and Automation calibration of coordinates, the robots can move precisely in the optimized paths. The ABB robot lap experiment shows that this routine can effectively reduce the time of artificial trial teaching and improve the working efficiency and the quality of robots.suitable for other robot path, such as welding, cutting, handling and so on. DXF Files DXF File Format. DXF files are of an open-source CAD (computer aided design) data file format (a vector image file). They are composed of several segments in the following order: HEADER (containing the general information of graphics), CLASS (containing the information defined by the applications), TABLES (containing the definitions of project), BLOCKS (containing the descriptions of the entities), ENTITIES (containing the graphic entities), OBJECT (containing the non-graphic objects of data) and a segment containing the preview of images. Each segment consists of GROUP CODE (indicating the types of subsequent values) and GROUP VALUE. To extract entity information of the graphics, many items of the DXF files can be omitted; and as long as the entity segment is obtained, the descriptions of point coordinates of the relative geometric graphics can be achieved. In the DXF files, GROUP CODE and VALUE are set in two rows respectively; the first row is GROUP CODE and the second GROUP VALUE, the data type of which is determined by the former. Each segment begins with the GROUP CODE 0 of a character string SECTION, followed later by the GROUP CODE 2 and the character string indicating the segment name, and ends with the GROUP CODE 0 of a character string ENDSEC. Read DXF files.the reading process as shown in figure 1 Fig. 1 Read Algorithm of DXF File Process

3 Advanced Materials Research Vol The GROUP CODE and VALUE exist in pairs.defines a two dimensional array of strings(private string[]str = new string[2]) to store the group code and values that have been read.use the methods Readtwoline() read two rows,a line is group code, the other is value,and return a two dimensional array of strings store in str[],if (str[1] == "ENTITIES") ReadEntities();/read if entity/ The main codes: void ReadEntities() /*the method of read entities section*/ { while (str[1]!= "ENDSEC") / *judge if the end of entities section* / { switch (str[1]) /* entities section* / { case "LINE": /*if the lines*/ ReadLine() /*read and store lines*/ break; case "CIRCLE": /* if the clrcle */ ReadCircle(); /* read and store clrcle */ break; case "ARC": /* if the arc */ ReadArc();/*read and store arc */ break; case "ELLIPSE":/* if the ellipse */ ReadEllipse();/*read and store ellipse */ break; case "LWPOLYLINE": /* if the lwpoline */ ReadLwpolyline();/*read and store lwpoline */ break; case"spline":/* if the spline */ ReadSpline();/*read and spline lings */break; default: str =Readtwoline();/*continue*/ break; } } } Store the information read in the prescribed dynamic array. Primitive Optimization In DXF files, the arrangement of graphic elements is based on the sequence of the primitive drawn, and store by a primitive control points of the condition of the default sort order, making the information of each primitive extracted from the parsing of DXF arranged in disorder. If the reading and conversion of the primitive information are carried out in accordance with this sequence by default, it may result in the randomness and chaos of the trajectories in the manufacturing process, the mass increase of the invalid stroke and the chaos of processing. The primitive optimization thereby must be conducted [6]. Supposing that the primitives recorded in the DXF files are Q-sets, take one primitive Q i at random. Divide Q i into two classes based on whether the graphic elements thus drawn are closed or not. One class includes LINE, LWPOLYLINE, SPLINE, ARC of DXF and some other non-blocking primitives with the initial and end points disconnected. Quantity is signified by M; The other one are the closed primitives with the initial and end points connected,including RECTANGLE, CIRCLE, ELLIPS, POLGON, LWPOLYLINE and so on. The quantity of it is signified by N. Then Q=M N The explanations of the algorithm on the arrangement of non-blocking primitives: Step 1: Specify one point of a primitive as Pi, i = { 0, 1,, M-1}. Put the other points of the primitive information behind this point.(as shown in Figure 2,suppose that P1 is the first control point. Then P1 is the first point. Find another point of the same primitive as P1; set this point as P2.

4 316 Advanced Manufacturing and Automation Then P2 is the second point. If during the drawing, P1 and P6 are of the same primitive, set P6 as the second point. In Figure 2, during the drawing, P1 P2 are supposed to be of the same primitive. ) Step 2: After saving the information of one primitive, set the end point of the process direction or the drawing based on this primitive as the new reference. Conduct traversal from Pk, k = { 0, 1,, M -W}(W signifies the primitive found), sequence point to the nearest point of primitives,repeat step 1. just as shown in Figure 2, the closest point to P 2 is P 2, the point where the storage of the arc information begins. Record the type of primitive as arc. If a primitive is an arc or elliptic arc, and not linked with the previous one, the initial and end points of this primitive can be calculated by using the data information got from the DXF about the primitive, such as its center, radius, starting and end angles, and so on. If the primitive elements are equal in distance, or the two endpoints of the same element are equal in distance, sequencing and storage will be conducted based on the principle that who comes first shall be handled first. Fig.2 CAD Drawing Examples The multipoint control primitives of the polyline and polygon are arranged in accordance with the storage sequence of DXF files. Then, the last storage point of the already arranged primitives shall be used as a new reference point to make out the primitive closed to this point. Take the center of circles or ellipses for the control point to calculate the distance if encountering these. Find out all the closed primitives N. Save all the primitives. And record the arrangement of each primitive, that is, the sequence of the processing of the workpiece, with a dynamic array, as the storage process runs. Coordinates Calibration The work coordinate system is the reference coordinate system for the robot motion. As shown in Figure 3, set O as the Origin and establish the coordinate system XYZ as the work coordinate system. The calculation is based on this coordinate system in relation to the spatial values given to the robots. That of the point coordinates of the primitive information read out by the DXF files is based on the Origin during the drawing. So set a Object coordinate system as X 1 Y 1 Z 1, use as the Origin the coordinate values of the first control point read out by the DXF files, Z 1 perpendicular to the workpiece, X 1,Y 1 designated to be overlapping the axis X, Y. Designate P 1 as the first control point just as shown in Figure 3, and establish a work coordinate system X 1 Y 1 Z 1, using this first control point as the Origin. Then P 1 P 2 P 3 P 4 shall be the motion path for the robot, that is, the process trajectory for the workpiece. Supposing that in the work coordinate system, the spatial values of the workpiece coordinate system are [Rx,Ry,Rz], those of the first control point during the drawing is [x 1,y 1,z 1 ]. Then [x,y,z]=[ R x - x 1,R y - y 1,R z -z 1 ], that is, the actual spatial coordinates when the robot moves to the first working point, so do the other control points in their principle. When the workpiece changes its position, it only needs the redefinition of the workpiece coordinate system (the first control point) before the robot can do is to operate precisely following the optimized primitive.

5 Advanced Materials Research Vol Examples of Application Fig. 3 Coordinates Calibration Figgure 4 shows the main interface of the software. After clicking on the controller scan, it will link all the actual and virtual robot controllers connected to this network. The IP address of this robot is , and is a virtual controller. Open the contour line of this processed workpiece drawn by AutoCAD in the DXF format and read the files. Figure 5 is the window for setting process and robot parameters, including the setting process of welding. Take the first control point to conduct the optimization of files, and store them in a dynamic array. Select the start control point by click on the small circle. The other control points should be optimized in Sequencing in accordance with the process shown above. Figure 6 is the simulated space point coordinates of the robot s trajectory [7]. Figure 7 shows the welding experiment set up by the use of ABB robots and Fronius welder. On the basis of the pcsdk provided by the robot language RAPID codes, the programming software in the PC can help design a software that can link the virtual and actual robot controller, developed in the C # programming language. The routine completed by the real controller gets its correspondence through the robot to PC, usually in the ways of Ethernet, RS23, CAN trunk, DeviceNet. The experiment here communicates through Ethernet. Figure 8 shows the result of robot doing the weld experiment according to the instruction of the robot trajectory developed by figure 5 primitives. Fig. 4 Main Interface of the Software

6 318 Advanced Manufacturing and Automation Fig. 5 Window of Parameters Setting Fig. 6 Results of Space Simulation Fig. 7 Experiment Equipment

7 Advanced Materials Research Vol Conclusions Fig. 8 Results of Experimental (1) Propose a method to read the open-source DXF files. This method conduct the traversal of the primitives needed of the ENTITIES, through the processing of the GROUP CODES and VALUES. (2) Optimize the arrangement of the chaotic primitive information that have already been read. And propose a priority principle and method for the storage sequence of the primitive, by the help of software. And conduct the calibration of the actual space coordinates of the robot. (3) Relative simulations and experiments show that this method can greatly reduce the trial time of the robot, and the implementation effect of the irregular processing path is much more noticeable. Acknowledgements The work was supported by the Major production project of Fujian province under No. 2012H6025, the Science and technology plan projects of Xiamen Grant No. JA13232 These financial supports are gratefully acknowledged. The authors also sincerely appreciate the comments and modification suggestions made by the editors and anonymous referees. References [1] Chengyi X, Lijiao X, Off- Line Programming Technology of Industrial Robot[J]. Journal of Nantong vocational college.2008, 22(3) [2] Huanming C, Zhenyu X, Pin L, Design and Implementation of the Off-line Programming System for Arc Welding Robot [J]. Journal of Shanghai jiaotong university.2008, (42) [3] Christine Connolly, The ABB Robot Studio technology and application Industrial Robot [M], [4] Zhenhui S, AutoCAD advanced tutorial [M].beijing: Tsinghua University Press,2002. [5] Chao T, Qunhui Z, Research on Read and Write Method of DXF Format File Based on AutoCAD [J]. 2009,( 21) [6] Qinghong Z,Zhiyong C, Rong M etc.,optim ization sequencing of graphic elements based on DXF file[j]. Computer Applications, 2006,26(1) [7] T. Erlemeier, B. Howard, Interface Design for Offline Robot Programming with the use of Virtual Simulation [D]. Iowa State University.