Six-axis Robot Manipulator Numerical Control Programming and Motion Simulation

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1 2016 Internatonal Conference on Appled Mechancs, Mechancal and Materals Engneerng (AMMME 2016) ISBN: S-as Robot Manpulator Numercal Control Programmng and Moton Smulaton Chen-hua SHE * and Che-hsuan CHANG Department of Mechancal and Computer Aded Engneerng, Natonal Formosa Unverst 64 Wen-Hua Road, Huwe, Yunln 632, TAIWAN *Correspondng author Kewords: Robot manpulator, D-H notaton, Forward knematcs, Inverse knematcs. Abstract. Ths stud, usng the KUKA KR s-as robot manpulator confguraton, adopted the Denavt-Hartenberg notaton to buld relevant knematc mathematcal model so that subsequent forward and nverse knematcs could be derved. Borland C++ Bulder was emploed to program the smulaton nterface, transformng the tool path fles generated from hpermill CAD/CAM software nto readable formats b robot manpulators. Moreover, OpenGL was used to complete the knematc smulaton of robot manpulators. Fnall, ths stud adopted the sold cuttng smulaton software VERICUT for further verfcaton and comparson. Result ndcates the effectveness of the proposed scheme. Introducton Robot s the scence and technolog n a varet of equpment consstng of mechancal, electronc, control, computers, sensors and artfcal ntellgence, and s one of the elements for the automaton of producton. Global ndustral robotc market demands manl come from the manufacturng sector, whch artculated robot s the most wdel used models and has ver etensve applcaton areas, such as weldng, dsassembl, transportaton, machner processng. Metal machner ndustr, electronc ndustr and chemcal ndustr are the manufacturng ndustr wth large-scale output value. Metal product manufacturng ndustr belongs to 3K ndustr and the producton process has the features to produce the same product repeatedl. Ths makes t sutable to use robotc manpulator for producton. If the manufacturer receves orders smoothl and faces the problem of lack of work eperence, the demand for robotc manpulator wll arse. A 6-as robot manpulator, wth ts moton functon capable of mmckng the human arms, has receved global attenton n recent ears. As tradtonal moton paths of robot manpulators are mostl nstructon-based, when a workpece has comple and uneven curved surface, such movng path could not meet the demands. To control the end effector of the robot accuratel, much research [1-3] has addressed the solutons of the nverse knematcs ssue of robot manpulators. Man manufacturers use CAD/CAM software and wth CNC machne tools for product desgn and manufacturng of part, and ther related techncal ablt has matured. The requred CNC program should be converted b the epensve commercal software whle mportng the robotc manpulator. Although commercal software such as SprutCAM [4], Robotmaster [5] could be used to arrange the movng and processng path of a robot manpulator and to generate the correspondng numercal control program, such software s costl. It wll not onl save consderable cost of nputs, but also ntegrate wth estng CAD/CAM software f the can appl the estng CAD/CAM modules and theoretcal bass for the feld of robotcs to carr out the path programmng. Therefore, how to effcentl and accuratel develop a path transformaton nterface for robot manpulators and how to use CAD/CAM software to generate correspondng paths are vtal ssues to be nvestgated. Ths stud develops a s-as robot arm NC programmng algorthms whch ntegrate the tradtonal CAD/CAM module. Based on the Denavt-Hartenberg (D-H) notaton matr [6], the s robot jont angles are obtaned from the forward/nverse knematcs. A wndow-based transformaton

and smulaton nterface wrtten b Borland C++ Bulder and OpenGL s developed whch can convert the tool path fle generated from CAD/CAM sstem nto robot NC program and smulate the robot moton.

Fgure 1 shows the confguraton and coordnate sstems of the KUKA KR 150-2 robot [7]. From a knematcs perspectve, a robot can be regarded as a sstem of n lnks.

2 and smulaton nterface wrtten b Borland C++ Bulder and OpenGL s developed whch can convert the tool path fle generated from CAD/CAM sstem nto robot NC program and smulate the robot moton. Robot Forward Knematcs In order to specf the pose of the robot end effector, the coordnate sstem should be establshed. Fgure 1 shows the confguraton and coordnate sstems of the KUKA KR robot [7]. From a knematcs perspectve, a robot can be regarded as a sstem of n lnks. To full specf the pose of each lnk, the D-H notaton s ntroduced. A set of D-H parameters s used to descrbe the spatal relatonshps between a jont as and ts two neghbor jont aes. The pose lnk wth respect to lnk -1 can be defned n terms of the lnk length a, jont dstance d, lnk twst angle α and jont angle θ as 1A = Rot (, θ) Trans( 0, 0, d ) Trans( a,0,0) R ot (, α) (1) where Rot and Trans are the rotaton and translaton matr, respectvel. The correspondng knematcs parameters of the robot are summared n Table 1. Snce the actual jont angles of KR shown n Fgure 1 are (0, -90, 90, 0, 0, 0), the jont angles of D-H parameters should be modfed as ( θ1, θ2, θ3 + 90, θ4, θ5, θ6). Fgure 1. Confguraton and coordnate sstems of the KUKA KR robot [7]. The pose matr of the lnk 6 frame wth respect to the base frame, whch s known as the robot forward knematcs and denoted b 0 A 6, can be determned b j k l j k l A6 = A1 A2 A3 A4 A5 A6 =. (2) j k l where = s ( c s + s c c ) + c [ s ( s s c c c ) c s c ] = s [ s ( s s c c c ) c s c ] + c ( c s + s c c ) = s s c + c ( s s c c c )

3 j = s ( c c s c s ) + c [ s ( s c + c c s ) + c s s ] j = s [ s ( s c + c c s ) + c s s ] + c ( c c s c s ) j = s s s + c ( s c c c s ) k = s s s c ( s c s c c ) k = s ( s c s c c ) + c s s k = s c c c s l = c ( a + a c a s + d c ) + d [ c c c s ( c c s + s s )] l = s ( a + a c a s + d c ) + d [ c c s + s ( c s s + c s )] l = a s + d s ( d + c d ) c ( a + c s d ) s = snθ, c = cosθ, s = sn( θ + θ ), c = cos( θ + θ ). j j j j Table 1. Lnk parameters of the D-H notaton for KUKA KR robot. L nk a ( mm) d ( mm) α ( ) θ ( ) Determnaton of Cutter Locaton Matr and Jont Angles Most current CAD/CAM sstems can produce the cutter locaton data ncludng cutter tp locaton p and tool as a as shown n Fgure 2. To represent the robot pose usng the cutter locaton data, two mutuall orthogonal unt vectors o and n should be determned. The followng equatons are obtaned b the defnton of orthogonal unt vector. an + an + an = 0. (3) n + n + n = (4) Snce there are onl two equatons to determne three unknowns (n, n, n ), nfnte possble solutons can be obtaned. For convenence, we can assume that n = a. Therefore, n and n can be determned as follows: aa an n =. (5) a

4 aa ± a + a a a a a a a a a n =. 2 2 a + a (6) Once two vectors a and n are obtaned, the vector o can be derved b the rght hand rule and the cutter locaton matr represented b [n o a p] s determned. Therefore, the s jont angles ( θ 1, θ, 2 θ, 3 θ, 4 θ, 5 θ ) of the robot can be obtaned b equatng the Eq. (2) and cutter locaton matr, and 6 usng the nverse knematcs. Fgure 2. Geometrc defnton of cutter locaton data. Vrtual Robot Smulaton Constructon A vrtual robot smulaton nterface was constructed b usng Borland C++ Bulder and OpenGL programmng languages n a Wndows envronment. The CAD model of the robot s created n the CAD sstem and, then, saved as the stereolthograph (STL) format. A STL parser s developed to anale the CAD model n STL format. The vrtual robot can be bult sequentall accordng to the relatonshp of structural elements of a robot confguraton. Addtonall, the robot moton s dsplaed usng the OpenGL lbrar ncludng Graphcs Lbrar (GL), OpenGL Utlt (GLU), OpenGL Aular (GLAUX) and OpenGL Utlt Toolkt (GLUT). Sstem Implementaton and Verfcaton Ths work develops a wndow-based robot smulaton nterface to demonstrate the feasblt of the proposed scheme. A cutter locaton data s generated b the hpermill software and converted to the robot NC program b the developed nterface. Fgure 3 shows a screenshot of the sstem eecuton dalogue where the robot NC program s eecuted. The user can actuate the robot b the NC program or manual data nput (MDI) functon where the jont angles can be manuall entered. The MDI functon provdes a quck and eas means of verfng that the machne component combnaton responds to NC code commands as epected. The generated NC program s further verfed on the sold cuttng smulaton software VERICUT [8], whch can construct the knematcs model of a robot and smulate the NC data. Fgure 4 shows that the KUKA KR robot s bult n the software envronment and the NC program s smulated. The results shown n Fgure 3 and Fgure 4 demonstrate the effectveness of the developed robot programmng algorthm and moton smulaton nterface.

Conclusons Ths paper presents a robot numercal control programmng algorthm and moton smulaton nterface for the KUKA KR 150-2 robot confguraton.

A wndow-based robot smulaton nterface bult b usng Borland C++ Bulder and OpenGL can smulate the robot moton b NC program or MDI functon.

5 Conclusons Ths paper presents a robot numercal control programmng algorthm and moton smulaton nterface for the KUKA KR robot confguraton. The s jont angles of the robot can be determned b the forward and nverse knematcs based on the D-H notaton. A wndow-based robot smulaton nterface bult b usng Borland C++ Bulder and OpenGL can smulate the robot moton b NC program or MDI functon. Through verfcaton b the sold cuttng smulaton software VERICUT, the valdt of the generated robot NC program can be confrmed. Fgure 3. Eecuton dalogue of the developed nterface. Fgure 4. Sold cuttng smulaton software VERICUT verfcaton. Acknowledgement The fnancal support of the Mnstr of Scence and Technolog of Tawan under grant MOST E s gratefull acknowledged. References [1] S. Kucuk and Z. Bngul, Inverse knematcs solutons for ndustral robot manpulators wth offset wrsts, Appled Mathematcal Modellng, 38 (2014) [2] L.W. Tsa and A. Morgan, Solvng the knematcs of the most general s-andfve-degree-of-freedom manpulators b contnuaton methods, Transactons of the ASME, Journal of Mechansms, Transmssons, and Automaton n Desgn, 107 (1985)

6 [3] C.W. Chang, Calbraton of knematc parameters of manpulators usng s-degree-of-freedom moton measurement devce (Master Thess, Natonal Tsng-Hua Unverst, Tawan 2009). [4] SprutCAM, [5] Robotmaster, [6] J. Denavt and R.S. Hartenberg, A knematc notaton for lower-par mechansms based on matrces, ASME Journal of Appled Mechancs, 22 (1955) [7] KUKA, [8] VERICUT, User Manual V7.3, CGTech (2013)

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