Dynamic Simulation System Using DOF Picking Robot

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1 Send Orders for Reprnts to 746 The Open Automaton and Control Systems Journal, 2, 7, Dynamc Smulaton System Usng DOF Pckng Robot Open Access Xaojun Lu * Department of Logstcs and Informaton Management, Zhuha College of Jln Unversty, Zhuha 94, Guangdong, Chna Abstract: A vsualzed dynamc smulaton platform of pckng robot based on OpenGL and Matlab s establshed n order to verfy the valdty of knematcs analyss and vsually reflect the moton process. The robot knematc model s establshed wth D-H method and the forward knematc soluton for the robot s obtaned. The nverse knematc soluton s solved by usng the smplfed nverse transformaton method accordng to the operaton features of the robot. Soldworks s adopted to set up 3D robot model, whch s transformed through Deep Exploraton nto cpp formatted fles that can be recognzed by OpenGL. Vsualzed smulaton verfcaton s conducted on the forward and the nverse knematc soluton and the grabbng moton of the manpulator are conducted on the smulaton platform based on Vsual C++6. and OpenGL. Track plannng s carred out for each of the manpulator jonts by means of Matlab Robotcs Toolbox. It s llustrated by the smulaton results that the knematc model establshed by D-H approach reflects the real moton condtons of the robot, and both the forward and nverse knematc solutons are correct. Keywords: DOF, Dynamc Smulaton, OpenGL, Knematc model, Matlab.. INTRODUCTION As the largest vegetable producng and consumng country, Chna wtnesses a contnuous and stable development of vegetable producton n recent years, wth the cultvated area ncreasng from 9 mllon mu n 99 to 29 mllon mu n 2 and the yeld from 9 mllon ton to 679 mllon ton. Meanwhle, however, t faces some challenges and problems demandng prompt soluton, among whch the most mportant ssue s that the agrcultural producton technque s relatvely backward and the level of mechanzaton and automaton has a large gap wth the developed countres. Agrcultural producers endure hgh labor ntensty; moreover, mproper manual work methods damage the garden stuff vegetaton and affect the qualty and quantty of garden stuff producton (X.Y. Tang, 2) []. Harvestng or pckng s the most effort-requrng and tme-consumng task n vegetable producton operaton. Moreover, t requres pckng n due tme to guarantee the product qualty, whch s the most laborous n the whole operaton. Wth the agng of populaton and the decrease of farmng labor force, t s more and more sgnfcant to research and develop frut and vegetable pckng robot [2-]. There appeared many pckng robots at the end of last century at abroad. In partcular, Japan s n the lead n ths feld n the world. The tomato pckng robot developed by KONDO-N, et al. n Japan, s based on SCORBOT-ER ndustral robot. (K.K. Guptal 26) Wth 7 degree of *Address correspondence to ths author at the Department of Logstcs and Informaton Management, Zhuha College of Jln Unversty, Zhuha 94, Guangdong, Chna; Tel: ; E-mal: lxj2482@63.com freedom and equpped wth 4 wheels, t can walk about n the feld and conduct target locaton for pckng through bnocular vson. The eggplant pckng robot, jontly developed by Japan Natonal Insttute of Vegetable and Tea and Gfu Unversty, consst of ccd machne vson system, DOF ndustral manpulator, end effector and runnng gear, wth a pckng success rate of 62. and an operatng speed of 64.s/each. In recent years, scholars n Chna also started the research and development of pckng robot. Jan Song, etc., utlzed optmzaton desgn method for the desgn of the robot body structure parameters n accordance wth the eggplant growth and dstrbuton space, and developed the basc machne of pckng robot of 4 degrees of freedom. The overall testng system operates n stable and relable way wth a grabbng success rate of 89% and average elapsed tme of 37.4s (N. Kondo et al., 996) [6, 7]. In the ntellgent tomato pckng robot end effector based on mult-sensor nformaton fuson and open control system desgned by Jzhan Lu, etc., ts vacuum chuck devce of the executon system can separate the frut from the frut bunch, ts fnger grpper mechansm can grasp the tomato frmly, and the frut stem dsconnectng devce can cut off the frut stem wth laser (J.Z. lu et al. 28) [8]. Vegetable pckng robot works through the movement of each and every jont (Shgehko et al. 22). As an mportant consttuent part of robotcs, Robot knematcs manly studes the relatonshps of the dsplacement, speed and acceleraton of the connectng rods of the robot moton arm, whose purpose s to establsh the relatonshps among spatal postons of the robot movng components and end effectors so as to / 2 Bentham Open

2 Dynamc Smulaton System Usng DOF Pckng Robot The Open Automaton and Control Systems Journal, 2, Volume provde theoretcal bass and techncal parameters for robot control (P. Cu 2, Yang, Chfu 2) [9]. In ths paper, the author begns wth establshng the robot mathematc model wth Denavt-Hartenberg method, and apples OpenGL and Matlab to conduct knematcs analyss and smulaton study on DOF pckng robot, whch solves the problem of knematcs analyss such as tedous analyss procedure, large calculaton amount and beng Error-prone n tradtonal mult-rgd-body system. Meanwhle the knematc performance of the robot movement mechansm s vsually dsplayed n the form of smulaton anmaton and dagram, provdng a strong guarantee for the follow-up robot moton tral plannng and the ratonalty verfcaton of structure parameters []. 2. KINEMATICS ANALYSIS OF PICKING MANIPU- LATOR 2.. Establshment of Robot Coordnate System The degree of freedom needed for the manpulator s analyzed and determned n accordance wth the requrement of the eggplant pckng process. The desgn requres for moderate amount of the degree of freedom wthout too many redundant ones so as to avod the ncrease of control dffculty and structure complexty. Ths paper adopts fve degree of freedom, namely, wast rotaton, shoulder luffng, elbow luffng, wrst luffng and wrst turnng, to match the grabbng process on the bass of actual demand. The structure s as shown n Fg.. Fg. (). Fve degree of freedom pckng manpulator schematc dagram. The pckng manpulator can be regarded as a connectng rod that s consttuted wth a seres of jonts. Each connectng rod establsh a coordnate system. It adopts 4 4 homogeneous transformaton matrx to descrbe the spatal poston relatonshp of the adjacent robot rod peces, thus translates the complcated knematc queston nto equvalence transformaton matrx of the reference coordnate system of the end effectors and reference coordnate system. Model of the connectng rod and jonts s establshed accordng to Denavt-Hartenberg as shown n Fg. 2 []. Fg. (2). Pckng robot jont coordnate system. From Fg., accordng to D-H method defne each connectng rod wth 4 parameters: torson angle α, rod pece length a, jont angle θ, horzontal dstance d, all shown n Table Knematcal Equaton When the spatal relatonshp between the two adjacent connectng rods -and changes n accordance wth the followng motons, the coordnate transformaton can be accomplshed. ) Revolve θ around axes Z - untl t reaches the poston where axes X - s parallel to axes X ; 2) Translate dstance d along axes Z- to cause X- to be collnear wth X; 3) Translate dstance a along X to cause the coordnate system orgns of the connectng rods to be concded; 4) Revolve angle α along X to cause axes Z- to be collnear wth axes Z. Repeat the above steps, and we can realze the transformaton of coordnates from the robot base to the frst jont, then to the second jont untl the end effector. The 4 tmes of homogeneous transformaton s presented n transformaton matrx A : A = Rot ( z, * ) & cos* = sn* % ( Trans(,, d ) ( Trans( a,,) ( Rot( x, ) ) ' sn* cos) cos* cos) sn) sn* sn) ' cos* sn) cos) a cos* # a sn * d " Eq. () For the rotary jont, when the coordnate system of each robot connectng rod s specfed, the parameters α, α and d are constant. In ths case, matrx A becomes functon of varable θ. For the robot wth n rotatonal jonts, the general transformaton of coordnates between the base and the end effectors s: 2 T = T T T A n 2 n 3 Tn = A A2 A3 n Eq. (2)

3 748 The Open Automaton and Control Systems Journal, 2, Volume 7 Xaojun Lu Table. Pckng robot jont parameter table. θ α α d Varable Range Lnk (mm) θ -9 ±8 L =34mm θ 2 ±9 L 2=3mm θ 3 L 3 ± L 3=3mm θ 4-9 L 4 d ±2 L 4= θ ±9 L =8mm Accordng to equaton () and equaton (2), the pckng robot wth DOF, and the end effector pose relatve to the base coordnates can be expressed as (Xong youpng, 996): T = A A A A A 2 & cc 234c + ss sc234c ' cs = ' s234c % & nx ox ax = ny oy ay nz oz az % 3 4 ' c c ' s c px # p y p z " s s + s c 234 s s ' c c ' c s 234 ' s s 234 ' c 234 ' d s + a c c 4 d c + a s c 4 ' a s a s c ' a s + a c c # " Eq. (3) The rght-hand end of the equaton s the end effector pose. The end effector pose matrx can be solved f the manpulator jont varables are known, and vce versa (M. Lu 2, Lara-Molna 2). The problem of the forward knematc soluton of the pckng robot s to solve the pose of the end effector relatve to the gven coordnate system wth the known jont varables and geometrc parameters of the connectng rod. From formula 2 and formula 3, the pose of the end effector of the DOF pckng robot s attaned. The ssue of nverse robot knematc soluton s to determne the jont varable values wth the gven poston and posture of the end effector relatve to the spatal coordnate system wth the gven geometrc parameters of the connectng rod of the robot. In ths paper, a smplfed nverse transformaton method s adopted to solve the nverse knematc soluton of the robot. In ths method, one or several nverse transformaton matrxes are multpled before the matrx transformaton, and then the correspondng elements on both sde of the equaton are compared to acheve the goal of solvng the nverse knematc soluton (W.Lu 2). 3. OPENGL SIMULATION SYSTEM OpenGL API provdes some basc geometry shape drawng, for nstance, dot, lne, surface, cube, sphere, cylnder, crcular cone, etc. Nevertheless, t wll be a dffcult and tedous process to only use the bult-n API for modelng when constructng complcated robot geometry shapes. In ths artcle sold works s selected for modelng, whch then transforms the component format through Deep Exploraton nto cpp formatted fles that can be recognzed by OpenGL, dsplays and assembles the model at approprate poston n MFC through callng glcalllst(), and mports the model nto OpenGL, as shown n the flow chart (Fg. 3). Fg. (3). The flow chart of model mport OpenGL. 3.. Implementaton of Dynamc Smulaton OpenGL software package adopted n ths artcle s ndependent of hardware and can operate n several operatng systems, so t does not have nterface problems. The steps of combng OpenGL and wndowsgdi are as follows. ) Call functon setpxelfomart and set pxel format; 2) Establsh drawng descrpton lst; 3) Acqure equpment lst and correlate t to descrpton lst; 4) Call OpenGL command to conduct drawng job; ) Call swapbuffer to refresh contents on the screen; 6) Release DC and RC when fnshng; As the postve drecton of Z axs of 3-D coordnate system n OpenGL faces the screen and the observer, t s not

Dynamc Smulaton System Usng DOF Pckng Robot The Open Automaton and Control Systems Journal, 2, Volume 7 749 correspondng to the coordnate system used by the manpulator.

4 Dynamc Smulaton System Usng DOF Pckng Robot The Open Automaton and Control Systems Journal, 2, Volume correspondng to the coordnate system used by the manpulator. Use translaton and rotaton functon to transform anew the coordnate, as shown n Fg. 4. nverse soluton algorthm. Fg. () shows the anmaton smulaton of the manpulator fetchng process. It can be seen from the OpenGL vsualzed smulaton result that the nverse soluton method proposed n ths artcle s smple and effectve wth accurate result. Fg. (4). Wast coordnate system transformaton. For the sake of the troubles for drawng that every tme call the rotaton and translaton functons, they wll be accumulated to the model vew matrx n OpenGL. OpenGL supples a unt matrx to reset the orgn,.e., resettng the coordnate system orgn by multplyng wth the unt matrx. Load unt matrx code s as follows: glmatrxmode(); glloadidentty(); In order to convenently load unt matrx nto the matrx stack, glpushmatrx () s employed to press the present matrx nto the matrx stack. Call glpushmatrx () s used to revert the matrx to the orgnal state when you want to recover the present matrx. For dsplayng anmaton effect, OpenGL provdes double buffers---when t dsplays foreground bufferng one mage, the background buffer s drawng the next mage, --- whch enables the anmaton to be consstent. Defne a tmer and call SwapBuffer() 3.2. Smulaton Result and Analyss Acqure the robot end effector poston and pose relatve to reference coordnate system,.e., the pose matrx, wth gven varables of the jonts lnkng the connectng rods n the smulaton system. Meanwhle, n accordance wth the fve gven jont angles, each robot jont rotates correspondngly n the smulaton platform so as to get a new poston and pose Knematcs Inverse Soluton and Grabbng Moton Verfcaton Accordng to the requrements of pckng object dentfcaton and locaton result, seek the robot knematcs nverse soluton usng the knematcs nverse soluton method proposed n ths artcle. Transfer respectvely nverse soluton result to the pckng robot. Defne the coordnates of the target grabbng pont n procedure. The computer acqures the nverse soluton and track plannng, conducts dynamc smulaton, completes the target grabbng and verfes knematcs Fg. (). Anmaton smulaton manpulator fetchng process. 4. MANIPULATOR KINEMATICS PARAMETER VERIFICATION AND SIMULATION The robot knematcs forward and nverse solutons are verfed through OpenGL-based robot dynamc smulaton. However, t does not obtan the relaton curve of the pckng robot dsplacement, speed and accelerated speed. Matlab Robotcs Toolbox developed and mantaned by Australan scentst Peter Corke s a seres of Matlab-based robotcs toolbox, whch s convenent for robot modelng and gettng knematc parameter curves of each jont (Corke et al. 99). 4.. Robotcs Toolbox Modelng When usng Robotcs Toolbox to structure a robot object, t frstly needs to buld each jont and then mplements the whole robot object by means of jont combnaton. To completely structure a robot object, t needs D-H parameters, jont types (translaton or revoluton jont), jont qualty and gear rato [2]. Robotcs Toolbox modelng s proceeded accordng to D-H parameter lst. Set command as follows: L =LINK([alpha A theta D sgma], CONVENTION); Among whch, alpha A theta D sgma represent respectvely torson angle, rod pece length, jont angle, horzontal dstance, jont type; CONVENTION represents D-H type. The Matlab-based pckng robot model establshed as shown n Fg. 6 s composed of the most basc elements of jont-type robot- jonts and connectng rods. It s n orgnal state,.e. all jont moves and angles are zero Track Plannng and Smulaton Pckng robot moton tracks fall nto two types --- space jont track and Cartesan space track. Robot track plannng s to work out the poston, speed and accelerated speed needed by the jonts n moton n order to complete the operaton. Jont space track plannng s chosen because t s too complex for plannng n Cartesan space and lable to have cases of no soluton.

The tracks of Jont 3 n samplng tme from the ntal poston qr to the fnal poston qz are as shown n Fgs. 7-9.

5 7 The Open Automaton and Control Systems Journal, 2, Volume 7 Xaojun Lu Fg. (6). Manpulator mod. Fg. (9). Jon speed t curve of 3. Q matrx row represents the rotaton angle of each jont of the actual samplng pont, and the latter two represent respectvely speed vector and accelerated speed vector. The tracks of Jont 3 n samplng tme from the ntal poston qr to the fnal poston qz are as shown n Fgs It s observed that the end effector does not produce strenuous vbraton durng the entre moton procedure meetng the job requrement. It s verfed that the theoretcal calculaton results obtaned from (4), () n D-H coordnate system s dentcal wth the smulaton result. Dsplacement and speed curve chart can reflect the real moton condtons and be appled to pckng robot control. Fg. (7). Jont dsplacement curve of 3. Fg. (8). Jont speed cure curve of 3. The toolbox provdes functon jtraj for nterpolaton to the jont, whose call format s [q,qd,qdd]=jtraj(qr,qz,t); CONCLUSION Pckng robot of DOF s developed n order to mprove the economy and adaptablty of the pckng robot. It adopts -DOF open moton chan whch connects the wast, the bg arm, the small arm and the wrst n seres through the rotatonal jonts. The robot completes the pckng operaton through movements of each jont. The objectve of studyng robot knematcs s to establsh the relatonshp of the spatal poston between the robot moton components and the end effector, to buld mathematc model of the robot arm movements, and provde theoretcal bass and techncal parameters for robotc control. It apples dynamc smulaton technology based on OpenGL and Matlab to the desgn and develop pckng robot, dsplays dynamcally the whole mechansm moton process, verfes the valdty of the control algorthmc, and obtans the robot knematc parameter curve. It s llustrated by the smulaton results that the knematc model establshed by D-H approach reflects the real moton condtons of the robot, and both the forward and nverse knematc solutons are correct. The research apples computer dynamc smulaton technology to agrcultural robot desgn. Compared wth the tradtonal method of manufacturng tral product, t not only saves the nput of manpower and materal resources, but

6 Dynamc Smulaton System Usng DOF Pckng Robot The Open Automaton and Control Systems Journal, 2, Volume 7 7 also greatly shortens the mechansm desgn and development cycle. As a modernzed desgn means, vrtual desgn technology wll certanly have an mportant nfluence on the development of agrcultural equpment. CONFLICT OF INTEREST The author confrms that ths artcle content has no conflct of nterest. ACKNOWLEDGEMENTS Ths work s supported by Shandong provnce scence and technology development project (No.2YD348) and Shandong Provncal Natural Scence Foundaton, chna (No.Y28G32) and Shandong Provncal unverstes Scentfc Research Project (No.J9LG3). REFERENCES [] P. Corke, A computer tool for smulaton and analyss: the Robotcs Toolbox for MATLAB, In: Proceedngs of the Natonal Conference on Australan Robot Assocaton, 99. [2] J. Z. Lu, P. P. L, and Z. G. L, Hardware desgn of the endeffector for tomato-harvestng robot, Transactons of the Chnese Socety for Agrcultural Machnery, vol. 39, no. 3, pp. 9-2, 28. [3] K. K. Gupta, and R. Gupta, Wavelet based speckle flterng of the SAR mages, Internatonal Revew on Computers and Software, vol., no. 3, pp , 26. [4] F. A. Lara-Molna, J. M. Rosáro, and D. Dumur, "Archtecture of predctve control for a Stewart platform manpulator," 8 th World Congress on IEEE Intellgent Control and Automaton (WCICA), 2, 2. [] M. Lu, and H.J. Zhao, Modfed self-adaptable wavelet transform arthmetc n mage edge detecton, Applcaton Research of Computers, vol. 28, no., pp , 2. [6] N. Kondo, M. Monta, T. Fujura, Frut harvestng robot n Japan, Advances n Space Research, vol. 8, no. 2, pp. 8-84, 996. [7] P. Cu, Z. Chen, and X.C. Zhang, Statcs analyss of apple-pckng robot humanod manpulator, Transactons of the Chnese Socety for Agrcultural Machnery, vol. 42, no. 2, pp. 49-3, 2. [8] S. Hayash, K. Ganno, and Y. Ish, Robotc harvestng system for eggplants, JARQ, vol. 36, no. 6, pp , 22. [9] X.Y. Tang, and T.Z. Zhang, Robotcs for frut and vegetable harvestng: a revew, Robot, vol. 27, no., pp. 9-96, 2. [] Y. Xong, "Robocs" Chan Mach Press, Chna, pp. 4-. [] Y. Chfu, Y. Zhengmae, O.O. Peter, and H. Junwe, "Modelng and smulaton of spatal 6-DOF parallel robots usng Smulnk and Smmechancs, In: 3 rd IEEE Internatonal Conference on Computer Scence and Informaton Technology (ICCSIT), vol. 4, pp , 2. [2] W. Lu, A.G. Song, and J.R. Ca, Structural desgn and knematcs algorthm research for orange harvestng robot, Journal Of Southeast Unversty, vol. 4, no., pp. 9-, 2. Receved: June 6, 2 Revsed: August 23, 2 Accepted: September, 2 Xaojun Lu; Lcensee Bentham Open. Ths s an open access artcle lcensed under the terms of the ( whch permts unrestrcted, non-commercal use, dstrbuton and reproducton n any medum, provded the work s properly cted.

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