1 APPLICATION OF VIRTUAL REALITY IN DESIGN OF ELECTROHYDRAULIC SERVO DRIVES AND THEIR CONTROLLERS Keyword: deign proce, virtual reality, electrohydraulic ervo drive. Abtract The article aim to get it reader familiar with virtual reality. It preent how ueful it may be while deigning electrohydraulic ervo drive control ytem. In the beginning of the article a definition of virtual reality and it brief hitory have been preented. There ha been alo hown it uefulne in variou field, among other medicine, aviation, mechanic, computer game and deigning proce. The following part of the article i a decription of choen application ued in virtual reality creation. Baic vice and virtue of VRML, Oxygen, CAD program and field in which they are mot frequently applied have been decribed. In the next part of the article it ha been hown how to combine imulation exiting in Simulink with virtual reality created with Virtual Reality Toolbox. The rule of contructing virtual world in a pecially adapted editor attached to VR Toolbox-V-Realm Builder 2.0 have alo been decribed. The whole proce of creating virtual reality i baed on a imulation of a model of electro-hydraulic ervo-mechanim ytem altogether with a proportional valve and with PID control ytem. The end of the article i a ummary of information concerning deigning of electro-hydraulic ervo drive with the ue of virtual reality. 1. INTRODUCTION Virtual reality (from latin word virtuali effective, virtu perfection) i a world created with the aid of computer technology, where a ample of natural environment i recontructed with greater or maller implification. Virtual reality i ued in the following field: computer game: from imple 3-D type, to complicated ytem where the player are equipped with helmet and tereocope pectacle, tereophonic headphone and location enor thank to which a computer know in which direction i a player looking at in a given moment, and alo pecial device: glove, joytick for communication with a computer and enor
2 fixed to a player body for telling the computer about the player move , movie production: particularly movie where the action take place in not exiting world ( Matrix i a good example here), aviation: pilot training flight imulator; navigation databae allow to do flight within optional airport and route and a ytem of cylindrical viualization, fixed to the ground, give the cabinet taff the impreion of movement , medicine: training of urgeon (operation performed on virtual patient), treatment of chizophrenia and different kind of phobia, recontructing of extinct, diappeared world and antiquitie in the Vaa Mueum in Stockholm one can ee a virtual model of boat Vaa that unk over 350 year ago, deigning product and production procee, e.g. viualization of the proce of machining (program of MTS: Topturn and Topmil for imulation of the proce of turning and milling) . A it i hown in the above example virtual reality ha quite a wide ue and i preent in almot every field of life. In thi article more preure will be put on applying virtual reality in a proce of project deigning with reference to electrohydraulic ervo drive. 2. APPLYING VIRTUAL REALITY IN DESIGNING PROCESS Several year ago deigning baically meant creating a prototype and undergoing tet on it. At preent, more and more often deigning phae conit of undergoing numerou tet for different parameter of the ytem on mathematical model and electing the bet olution. Thi i the bet olution which i launched on the market. While contructing a model, we have a poibility to examine how a mechanim work without building it which coniderably reduce the cot. During project deign virtual reality, alo called artificial reality, i ued for imulating the ene of ight and provoking the effect of 3D viion and howing the move of the object. Additionally, all thee might be combined with audio effect that boot the ene of reality. There are many application of virtual reality. Among them one can mention VRML, Oxygen, Cad decribed below and other, e.g. 3D Dream by Shell, Cult3D (Cycore Computer), Depthcharge (Vrex), Meta Stream (Inlet), Open Space (Virtu) or Quick Time VR (Apple). Work with all the application conit of imilar tage: 1. Creating of three-dimenional model in virtual reality. 2. Attributing movement to uitable element. Scientit have been intereted in development of virtual product deigning for everal year. The reult i creating the project IVIP  (Integrated Virtual Product
3 Application of virtual reality in deign of electrohydraulic ervo drive and their controller Creation in 1998 where virtual reality i ued in imulation of product behaviour. The partner of that project are BMW, BOSCH, Dimler Chryler, Porche, Siemen, and many other (51 firm altogether). Problem of virtual deign were alo dicued in cientific project EU-Mech , which aimed at working out integrated engineering environment upported by a computer for the development and deign of mechatronic product and MechaSTEP  aimed at working out digital model for imulation of mechatronic ytem. 3. REVIEW OF CHOSEN APPLICATIONS FOR CREATION OF VIRTUAL REALITY One of the program ued mot often for decribing virtual reality i VRML (Virtual Reality Modelling Language). It allow to define three-dimenional object, their location in three-dimenional area, their interaction, and alo their reaction to particular event that are the reult of human being performance in uch defined world. Thank to it, we are able to create interactive virtual world where we have a poibility to walk among defined object in a real world, to meet other participant of the world and to define any amount of interactive enor that change the look of the world according to it participant wih. With the aid of the ytem of reference and uing the mechanim imilar to that which i preent in HTML we can define connection between element of virtual reality decribed in VRML document, altogether with other document VRML, HTML or other type . Many example of virtual world created with the aid of the programming language can be found in Internet. To watch them, one mut have intalled plug-in co-operating with Internet brower, e.g. Como Player, World View, FreeWrl or Cau Preenter. Oxygen i the next program worth mentioning. It ditinguihe itelf with a perfect viualization of object preented on a monitor creen. Oxygen may be particularly ueful for uch tak a preenting product which till have no prototype, or for training intallation and maintenance of not exiting yet device. With the ue of Oxygen medical imulator for training urgery (Claru Virtual Shoulder Arthrocopy) have alo been built. Simulator of a new model of Volvo and military imulator (tank Leopard 2 for Swedih Army) have alo been created in thi program. Virtual reality created with the program Oxygen and with the ue of ening glove and virtual helmet ha been ued in BMW mainly for examining aembly matter. New conception of packing have been imulated for Tetra Pak. Digital eyehole made it poible to go inide the packing machine and oberve it work in place that can not be een in reality. Oxygen operate on Silicon Graphic computer under IRIX operating ytem which i a variety of UNIX ytem . The lat program that i going to be decribed widely in thi article i CAD ytem. The ytem, particularly 3D-CAD ytem (form deign) i ued in virtual
4 creation of a product in it early tage of preliminary deign. Except geometric repreentation of the product and it tructure 3D-CAD ytem alo contain other product data, uch a: material and the way of proceing. CAD ytem often communicate with each other with the DMU (Data Management Unit) ytem. They ue product tructure and approximate geometric repreentation data tranforming them into kinematic data. It allow to make analyi of kinematic product behaviour a well a analyze intalment and unintalment procee. Virtual prototype include phyical data of product taking into account their ue in pecific field uch a mechanic, electronic a well a logitic. The program decribed above are only exemplary application ued for virtual reality creation. They are o comprehenive that it i poible to ue them in different domain. There are alo program concentrated on creating virtual reality in trictly pecified field, e.g.: ADAMS allow to perform complicated kinematic and dynamic analyi of the object moving in real time. It conit of many package, among other Rail allowing fat and eay parametric building of rail vehicle. Medical Multimedia Sytem company have worked out the program howing how human body work: Brainiac Interactive Neuroanatomy Atla human brain work, Viible Human Atla virtual atla preenting the inide of the human body; SimBioSy Simulator imulating human body performance, Proolvia Reearch & Technology ue oftware LS-DYNA3D in combination with CAD Real-Time Link for imulating car crahe. CAE Electronic Ltd. have built oftware for imulating atoming power tation and carbon power tation. It i alo the author of profeional ytem of civil flight imulator, Flight Training Device, Viual Sytem Simulator, Computer Baed Training and Computer Aited Training Sytem. 4. DESIGNING OF ELECTROHYDRAULIC SERVO DRIVES WITH THE USE OF VIRTUAL REALITY THANKS TO SIMULINK VIRTUAL REALITY TOOLBOX Mathwork company following deigner need have alo worked out a tool for virtual reality creation Virtual Reality Toolbox. Deigning with the ue of virtual reality in Matlab Simulink i baed on mathematical model created before. In the article electrohydraulic ervo drive model (third degree) with proportional valve imulated with the help of inertiale element have been taken advantage of [11, 12]. The ytem i characteritic of tranmittance decribed with a formula 1.
5 Application of virtual reality in deign of electrohydraulic ervo drive and their controller 2 y( ) k G( ) (1) 2 2 x( ) ( 2 ) where: k reinforcement ratio, ω undamped natural frequency, ζ damping ratio. The above quantitie can be pecified on the ground of ervo-motor producer catalogue data and they depend on ervo-motor dimenion, preure and type of working liquid, friction, ytem tiffne and ma hifted. Taking thee parameter into conideration and uing a formula it i poible to deign a ervo-motor and create in Simulink a correponding model. The model already exiting i connected to virtual world thank to pecial element which are in Virtual Reality Toolbox: VR Signal Expander and VR Sink. VR Signal Expander convert imulation ignal into a ignal compatible with a VRML language. In cae of imulation decribed in the article it i a hifting of a ervo-motor piton. VR Sink, on the other hand, include graphic interface of the uer combining imulation with virtual reality. In it, it i defined what type of move mut be performed, file acce path i given, and editor and brower VR are evoked. Fig. 1. View of editor V-Realm Builder 2.0
6 Virtual world i deigned in a pecially adapted editor V-Realm Builder 2.0 (fig. 1). The editor ue VRLM environment. A model of a imulated mechanim i built of three-dimenional olid. There i alo a poibility of importing a ready model made in other editor or Cad program. The program include a 3D library of object, however there are no hydraulic element. Particular part can be given dimenion correponding to real mechanim dimenion, of coure uitably diminihed. Three-dimenional model ued during imulation ha been build according to a real ervo-motor of Walmet firm. While building a model ome implification ha been made focuing on the mot eential element of a ervo-motor. The element are preented in fig. 2. Cylinder Joint bearing Lug Piton rod Piton Piton eal Fig. 2. Component and a view of the internal tructure of a ervo-motor Poibility of viewing created object in four projection i coniderably helpful while building a three-dimenional model. The model can be optionally illuminated and particular element may be given different urface quality and colour. Then, the move of particular element i added. It may be a linear lip, rotation or object ditortion. Whole virtual world created with the aid of V-Realm Builder i tored in one file with *.wrl. expanion Virtual world made in V-Realm Builder can be acceible for other computer in the net. In that cae Matlab-Simulink package
7 Application of virtual reality in deign of electrohydraulic ervo drive and their controller mut be intalled on Window NT erver and domain erver mut be incribed into Internet brower of a computer-client and port number, where virtual reality z ha been made acceible. One of the plug-in, mentioned in point 3, or joined to Matlab plug-in Blaxxun mut be intalled on computer-client for viewing virtual reality. It i poible to oberve the move of the object in virtual world only during tarted imulation thank to a brower Virtual Reality Toolbox Viewer (fig. 3) included into a package Kp y To Workpace Step Ki 1 Integrator1 Sum -K- KQ=12 1 Integrator5 1 1 Integrator2 Integrator3 Scope Kd du/dt 40 Derivative D=0.2 VR ruchome.tranlation KQ= VR Signal Expander VR Sink w= Fig. 3. View of a Virtual Reality Toolbox Viewer brower altogether with electrohydraulic ervo drive model with PID controller build in Simulink. In the example preented the move of ervo-motor piton i done according to ervo-motor data taken from a model created in Simulink program. The ignal of piton location i converted into a format uitable for a VRML language. Additionally, PID controller i included into a ytem. Within thi imulation etting of regulator may be changed applying the method of Ziegler Nichol election, and then applying different piton location one can oberve how i a move performed and a piton rod poitioned.
8 5. CONCLUSION The example decribed in the article how that virtual reality may be uccefully applied in the proce of deigning and teting all ort of product. A number of different program and eay acce to all ort of information in thi field in Internet prove popularity of virtual reality application. There are no obtacle to apply them in deigning teering ytem of electrohydraulic drive. Of the example preented in the article one can ee that applying virtual reality in the proce of deigning teering ytem of electrohydraulic ervo drive i a imple and clear way of viualization of the whole proce. In the future they will come into effect activitie aiming at creating databae of three-dimenional model of hydraulic element (valve, ervo drive), which might be ueful for deigner in the proce of deigning or for teacher a didactic help. REFERENCES       Projekte/projekt_html?project=    Ihttp:// on/application.htm  Milecki A., Wybrane metody poprawy właściwości liniowych erwonapędów elektrohydraulicznych, Politechnika Poznańka  Pizoń A., Elektrohydrauliczne analogowe i cyfrowe układy automatyki, WNT Author: mgr Paweł BACHMAN Uniwerytet Zielonogórki, Intytut Edukacji Techniczno Informatycznej Zielona Góra, Al. Wojka Polkiego 69