Virtual Environment of Design: A Hybrid CAD Tool

Transcription

1 Vrtual Envronment of Desgn: A Hybrd CAD Tool Chensheng Wang, Jors. S. M. Vergeest Faculty of Desgn, Engneerng and Producton Delft Unversty of Technology Landbergstraat 15, NL-2628 CE Delft, The Netherlands {c.wang, j.s.m.vergeest}@o.tudelft.nl Abstract A vrtual envronment of desgn can provde the ndustral desgner comprehensve power and flexbltes beyond geometrcal desgn by means of enablng modelng, analyss, and smulaton of both mechancal and electronc systems n an ntegrated envronment. The desgn of electronc applance has specfc characterstcs dstngushed by ts hybrd features. To support ths knd of desgn, ssues of both mechancal and electronc nature need to be concerned. Ths paper focuses manly on the modelng and smulaton aspects of electronc products desgn. Wth a generalzed overvew on CAD tools, n ths paper, a framework of the vrtual envronment of desgn s presented and a formal descrpton of modelng of the desgn task s formulated as a hybrd system. As an example, a hybrd CAD tool for a VCR controller desgn s dscussed n detal, ncludng hardware set-up, computaton model, event handlng, system descrpton, and reformaton of desgn process of electronc products va smulatng and valdaton facltes provded by the vrtual envronment of desgn. Index Terms Dynamc systems, Hybrd CAD, Smulaton, Vrtual desgn. I. INTRODUCTION Obvously, by means of usng CAD tools productvty of desgners has been greatly mproved durng the past twenty years. Wth the development of CAD technology, today, most of the commercal CAD systems provde not only the support for the desgner to shape geometry of ther desgn easly, but also provde means to evaluate the desgn result. Generally, a fully equpped CAD system provdes such functons or tools lke: Geometrcal modelng; Manuscrpt receved January 3, Ths work was supported n part by the project of Tranng for Creatvty and Innovaton by Product and Process Desgn: A New Learnng Factory, an Area of Strategc Development (ASD) funded by the Hong Kong Polytechnc Unversty, and also by Desgn Technology Research Center (DTRC), School of Desgn of the Hong Kong Polytechnc Unversty. C. Wang s wth the Delft Unversty of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands. (Telephone: ; fax: ; e-mal: c.wang@o.tudelft.nl). Vsual valdatng (e.g., photo-lke shadng effects); Geometry pre or post processng (e.g., pre or post processng for fnte element); Dynamc anmaton of movement and examnaton of nterference of geometrcal parts n a mechancal assembly; Or other functonal tools such as analyss of dstrbuton of temperature or plastc flow for the desgn of njecton mold, and so on. All these well-developed functons are manly concerned wth part s geometry. Therefore they are usually called mechancal CAD systems. Some example systems are CATIA, pro/engneer, I-deas, Ucld-IS, UG-II, SoldWorks, Inventor and so on. Another category of CAD system s called EDA (Electronc Desgn Automatc). Ths knds of systems can perform precse calculaton not only on layout of large scale ntegrated crcut desgn, but also on sgnal ntensty, power consumpton, etc. They can even fgure out the sgnals at a specfc measure pont by vrtual power appled on the crcuts. For example, systems lke Mentor Graphcs/Calbre, OrCAD, SPECCTRA, etc. There are other CAD systems lke Alas, 3DS Max or Maya, whch are more sutable for use n ndustral desgn. They can provde the powerful ablty to fgure the vrtual realstc scene for an object n a certan envronment, or anmate the effect of movng, collson or even specal vsual effect, such as partcles, fog and flame, etc. One of the shortcomngs of these systems s that they are weak of exact control of geometry compared wth mechancal CAD systems. Even though beng ncapable of provdng exact geometry control, they are stll wdely adopted by ndustral desgners n shapng concept of consumer products. Meanwhle, because of ther powerful ablty of flexbly controllng over shape, nowadays, the fuson of mechancal CAD systems and ndustral CAD systems becomes a new trend n the study of CAD technology. From techncal pont of vew, both CAD and CAID software are dealng wth only geometry tself. In other words, J. S. M. Vergeest s wth the Delft Unversty of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands. (e-mal: j.s.m.vergeest@o.tudelft.nl).

2 for consumer product desgn, any extenson for the valdaton of the desgn stll remans not well support. Unlke commercal CAD systems prevalng Feedback today n mechancal and/or ndustral desgn felds, the hybrd CAD system deals wth heterogeneous problems that occur durng the Input ncorporaton of CAD tools wth control theory, wth whch a vrtual envronment of desgn s establshed. A typcal example s the desgn of electronc controller. A hybrd CAD system s dstngushed by the followng features, n whch they deal wth [2] [6] [8]: Heterogeneous systems and models of computaton; Modelng herarchcal hybrd systems; Smulatng contnuous dynamcs; Event handlng, and Hybrd system executon. The hybrd CAD system s the core of the vrtual envronment n electroncs desgn. A general CAD system typcally supports the modelng of geometrc aspects, but a hybrd CAD system supports the modelng of heterogeneous synthess, such as contnuous systems wth phased operaton, contnuous systems controlled by dscrete nputs, or coordnatng processes (mult-agent systems) [3]. Combnng wth geometrcal modelng tools, the hybrd s capable of provdng both modelng of shape and valdatng of functon of the desgn. In ths paper we demonstrate a vrtual envronment of desgn, whch concentrates at a hybrd desgn tool appled to the desgn of a VCR controller. A generalzed framework of ths vrtual envronment of desgn wll be provded n secton 2. Secton 3 presents the descrpton and formalzaton to the modelng of desgn task n a vrtual envronment of desgn wth the support of a hybrd CAD tool. As an example, n Secton 4, a desgn of VCR (Vdeo Cassette Recorder) controller n the vrtual envronment and related ssues are descrbed n detal. Secton 5 gves an llustraton about the vrtual desgn process. Conclusons and consderatons about the study of vrtual envronment of desgn and ts prospect are presented n Secton 6. II. FRAMEWORK OF THE VIRTUAL ENVIRONMENT OF DESIGN The vrtual envronment of desgn s composed of dfferent modules, whch carry out defnte functons (sometmes, they are also called agents). In ths vrtual envronment of desgn, a hybrd system s ts kernel, n whch dscrete actons (command or ponter acton) wll trgger the shftng of a dynamc state. From a general pont of vew, a vrtual envronment of desgn can be depcted as fgure 1. In fgure 1, the user nterface and a hybrd system compose the vrtual envronment of desgn. A, B and C are the three User Interface A B C Trgger Acton Agent Reacton Fg. 1. A general vrtual envronment of desgn FSM Hybrd system Contnuous Dynamc Process Output prncpal components of a hybrd system. The meanng of each term n the fgure s as below: Input/Output (I/O): nteracton between hybrd system and user; Agent: a software module that carres out specfc functon; FSM: fnte state machne; Contnuous Dynamcs: state of a runnng process; Reacton: feedbacks to the user from the dynamc system; Trgger/Acton: state transton of FSM. The user nteracts wth bult-n agents through the user nterface to defne functons, control data, and anmatons of the hybrd model (A). The target can be thought as a fnte state machne, whch has countable control states and s able to produce a contnuous output (B). When a specfc functon s trggered, a contnuous system output shfts from one state to another (C). Current system state can be montored by acqurng the feedback sgnal of the runnng physcal system (e.g. usng sensors n hardware). One of the mportant facltes n a vrtual envronment of desgn s the functon of anmaton, whch wll be descrbed n ths paper later n detal. III. MODELING OF DESIGN TASK IN THE VIRTUAL ENVIRONMENT OF DESIGN The core of the vrtual envronment of desgn s a hybrd desgn tool. Therefore, modelng of desgn task remans practcally the modelng of the hybrd system. Snce there are several defntons for a hybrd system, here we adopt the defnton that an n-dmensonal hybrd system H s a 6-tuple, H = ( Q, E, D, X, G, R) (1) Where: Q { 1, K, k} = s the fnte set of (dscrete) states of H, where k 1 s an nteger; E Q Q s the collecton of edges; { D Q} D { } D = : s the collecton of domans of H, where R n, for all Q ;

3 D Fg. 2. A hybrd system = X (χ) χ G(,j) y : R (,j) (χ) X = { X : Q} s the collecton of vector felds such that X s Lpschtz on D for all Q ; G = { G() e : e E} s the collecton of guards, where for each e = (, j) E, G( e) D ; R = { Re : e E} s the collecton of resets, where for ( ) E R e D j = X j (χ) each e =, j, s a relaton between elements of G(e) and elements of Dj,.e. Re G( e ) D j. In ths defnton, the ntal state s thought as a specal case that any pont of the runnng process could be an ntal state G = G( e ), [1] [4] [8]. As descrbed n [8], ths defnton can be represented by fgure 2. Doman D les n dstnct copes of R n. So we can let D = (2) R = R ( G e )), U Q D and D s called the total doman of H. Supposng that R e s a map, we denote: VCR: Fnte State Machne States Transtons Dscrete Events Computer Controller Model E Events: Operatons on events Contnuous tme Dscrete events I Control Data Feedback Fg. 3. A computaton model of the hybrd CAD tool TV set g = G = U G( e), R = U R( e) e E { G( e) : e E}, R = { Re ( G( e)): e E} To a gven H, startng from a pont n some doman D, we flow accordng to X untl we reach some guards G(,j). At that pont t s possble for the state to swtch va the reset R (,j) and contnue flowng n D j accordng to X j and so on. To the hybrd modelng of VCR controller system a descrpton can be as followng: For a hybrd VCR system H, Q = { 1, K, k} s a fnte set of state H and D denotes the collecton of runnng domans of H (e.g., Stop, Play, FF, Rewnd, Reset, etc.), then X may be: X = f C, V ), ( where C s a command vector of VCR, V s the VCR play speed. There are three play speed levels for a VCR: 0 (when stop) V = 1 (normal). 2 (rapd) Untl a new command s receved, the valve of guard s changed to a specfc value,.e., where e denotes the event that trggers the change of G. Then a state transton of the hybrd system s trggered by ths condton, the VCR resets accordng to ts current state: e ( ( ) then the system runs wth new X = X x. Typcally, the state transton process ncludes 3 steps: 1) Stop current state D ; 2) Clear error code; 3) Swtch to a new state D j, and keep runnng accordng to a new X j. Incorporatng wth above modelng defnton, a hybrd CAD tool s mplemented to evaluate the desgn of a VCR controller by provdng support to both geometrc and functonal valdaton. Contnuous tme: Contnuous functon Contnuous tme Contnuous sgnal Sensor (3) IV. AN EXAMPLE OF THE VIRTUAL ENVIRONMENT OF DESIGN: A HYBRID CAD TOOL A combnaton system of geometrc and electronc model composes a vrtual envronment of desgn. There are several components ncluded n our example system: a CAD modelng software wth a geometrc model of the VCR controller, a physcal VCR (JVC BR-S800E) wth control a board (SA-K27EA), a televson set servng as a vdeo montor, and a set of connecton

4 cables. In ths experment, the VCR s treated as a fnte state machne that produces contnuous output, and a vrtual controller model serves as a bult n model to control the Fg. 4. The hardware set of the vrtual envronment of desgn actons of the VCR. These components establsh a hybrd system as the core of the vrtual envronment of desgn. A computaton model of ths kernel hybrd system s drawn as fgure 3. There are two mportant modules n the computaton model, namely event handlng and fnte state machne: 1) Event handlng: It s composed of a geometrc controller model and mouse ponter. It s actve on contnuous tme trajectory, generatng and manpulatng dscrete events accordng to specfc rules. It operates dscrete event to nteract wth fnte state machne. 2) Fnte state machne (FSM): It s a VCR set, and s trggered by control data, and can mplement transton from one state to another. The current state of a FSM wll be keepng steady untl next state shft sgnal occurs. When a FSM n runnng t produces a contnuous output. Wth the help of the vrtual envronment of desgn, the desgner now s able to defne the functons of the controller buttons and ther actons when trgged, to connect the remote devce (the VCR n ths example) through RS232 (seral port), and to test the functons of the whole system n a vrtual envronment. A. Hardware set up To keep the ntegralty of the ntroducton, we wll use a few words to explan the hardware set-up of the system. The demonstraton of the vrtual envronment of desgn we use s a JVC BR-S800E. A SA-K27EA control board serves as a command nterpreter to control the VCR acton properly. The control board should be nstalled nto VCR set correctly accordng to JVC servce manual of SA-K27EA. The hardware connecton ncludes computer to VCR connecton and VCR to TV connecton. Follow the nstructon of each hardware manual. A cable connects computer and VCR. Ths cable sends out control data and gathers feedback nformaton from VCR. There are two cables named Audo/Vdeo cable between VCR and a TV set, whch serves as an output of contnuous system state. Fgure 4 shows the whole hardware set of the vrtual envronment of desgn. B. Herarchcal vew of the hybrd CAD tool Consderng a herarchcal vew of the hybrd CAD tool, the top-level s a contnuous-tme system, where one or more components are composte modules. These composte modules mplement fnte state automata nternally. Each state of the automaton can be further refned by ether another layer of automaton or a contnuous-tme subsystem. Ths herarchy can also be further nested untl all subsystems are refned by a contnuous-tme subsystem, as shown n fgure 5. In the example dscussed, a controller model s refned as geometry module, functonal module and so on; agan, the functon module can be refned as event handlng, etc. Ths refnement can be down even further. And ths herarchcal representaton of hybrd system can help to get a better understand about how a hybrd system works. C. Event handlng Event handlng s the pvot ssue of the hybrd CAD tool. It s the creaton and manpulaton of events that makes t possble for the user to nteract wth the fnte state machne. An event s defned by a functon: E = ψ ( A, τ ),

5 Fg. 6. Man nterface of a hybrd CAD tool where A s an acton type, such as mouse movng, button down or key press, and so on; whle τ s a tme trajectory that decdes the order of a specfc event n the event sequence. When an event happens on a body that s attached wth prevously defned functon, then ths event wll trgger a state transton on VCR (guard G s changed at ths tme). The VCR wll take transton from one dscrete state p to another dscrete state q whenever G = G e ) ( s detected. Ths sgnal s sent by event handlng process. Controller Model Geometry Module Fg. 5. A herarchcal vew of hybrd CAD tool A C Functon Module Event Handlng VCR Set B A/D or D/A There are two types of event beng handled currently: Predctable event, unpredctable event and nondetermnstc event. We wll gve a bref ntroducton to the manpulaton of these two types of event. 1). Predctable event In the hybrd CAD tool, when an object s fully defned wth both command and anmaton, then when an acton happens on ths object (e.g., button down, button up, ponter move, etc.), an event occurs. Ths event wll act accordng to pre-defned roles, and t s called predctable event. For example, n fgure 6, the rght button s defned wth followng data: Command name: Play Command code: 0x3A Attrbute type: Translate Attrbute vector: (0.0,0.0,1.0) Attrbute value: 2.0. The attrbute type defnes the movement of the object. There are two types of attrbute: translate or rotate, as shown n fgure 9. So when a mouse button-press acton happens, the geometrc object (button) wll send out a command code, the system wll translate the object down (anmaton of press acton) whle left mouse button s down, and translate the body up when left mouse button s up, wth a dstance value of 2.0 n translaton. OUTPUT 2). Unpredctable event and nondetermnstc event Sometmes an ntegrated acton happens on a functoned object. When ths happens, t changes the event type of the object from one to another, and the event type s marked as unpredctable. Ths event wll not be recognzed at all, even f there s a predctable event pece or both of the events are predctable n ths event composte. An unpredctable event can be represented as: U = u E, E ), e ( j where ether E or E j may be predctable or unpredctable events. Another possblty s that there are some event or event combnatons left undefned,.e., they are non-determnstc events. To smplfy the control

6 Fg. 8. mechansm, both unpredctable events and non-determnstc events are montored by the system. When such an event happens, the system wll parse the queue of command, deal wth predctable events, and smply gnore the unpredctable and non-determnstc events. D. Hybrd executon Play 0x3A A dalog to set command name and data As dscussed above, the hybrd CAD tool enables the nteracton of dscrete and contnuous dynamcs and makes the correct smulaton of the hybrd system possble. From a hybrd pont of vew, the executon of hybrd CAD tool has followng features: Tme propagates to all components; The system s flattened as a CT (contnuous tme modelng) system at each ntegraton tme pont; FSM cannot make transtons durng Fg. 9. Dalogue to defne an anmaton ntegraton steps; After each ntegraton step, the FSM examnes the output from the current refnement, and evaluates the trgger condtons; FSM makes transtons accordng to trgger evaluatons (guard G ); FSM performs actons on the transton when trggered; The contnuous dynamcs of the destnaton state s ntalzed by the reset relaton on transton. The smulaton contnues from current tme pont; Fg. 10. Connect or dsconnect dalog Fg. 7. Tool menus Events occur always synchronously on both geometry and electronc model of the hybrd system. It s true that for a determnstc hybrd automaton (wth predctable event set) t wll carry on above defnte characterstcs durng executon. But to a non-determnstc hybrd automaton (wth non-determnstc event set) wll run wth uncertan behavors. E. System descrpton A gear-lke con on the toolbar stands for the functon of hybrd CAD. A gray con means that there s no functon and acton defned n the geometrc model currently opened. Fgure 6 shows the man nterface of the whole system. Menus n Tools can support hybrd-cad applcaton. They are n the Attrbutes menu, ncludng Add Command, Edt Command, Add Acton, and Edt Acton. These functons have been mplemented n the ACIS platform, currently. The Add Command/Acton menu tems on toolbar are only actvated when there s an Orgnal controller Fg. 11. Button pressed Button released (A) (B) (C) Process of anmaton of button press object (body) n the geometry model pcked, and the Edt Command/Acton menu tem actve only when the geometry model contans objects that have the command/acton defnton attached to t. Fgure 7 shows the menus related wth command and acton. Command names and correspondng command data (wthn command set C) can be set by a dalogue. Fgure 8 shows the dalog of Functon Command. There s also a faclty provded for the desgner to defne anmaton acton, whch occurs on the geometrc model when a functon s trggered. Fgure 9 shows the dalogue for an anmaton defnton. After a command s defned onto an object, the command (D ) wll be sent out to the devce to trgger a state shft from H to H +1 when the user clcks that object, and an accompanyng acton s anmated also. The desgner can defne some actons onto an object wthout commands, too. Then the body only moves but no commands are sent out when a push button event occurs. Even though you have already connected the VCR to a computer through RS 232 (COM) port physcally, t does not mean that the software module s aware of the exstence of a VCR. At ths tme, a soft connecton should be taken. The physcal VCR can be connected to software module usng the

7 Fg. 12. Geometrcal Modelng Electromechancal Valdaton Revson Product Desgn Cycle functon menu con on the toolbar (gear-lke). If the physcal devce s not connected, a dalog popup to allows the user to set up software connecton between the physcal devce and the computer through RS-232. Otherwse, the dalog allows dsconnectng the physcal devce. Fgure 10 shows the dalog of connectng or dsconnectng. Keepng connect state, the so-called ray frng s actve, f the mouse ponter stays on an object wth command attached n current model of product, then the command name wll pop up as a prompt after about 1.5 second, as shown n fgure 6. The prompt wll dsappear after 7 second or after the desgner move the mouse. As demonstrated n fgure 11, (A) s the orgnal state of a VCR controller; when the desgner pushes the left mouse button on an object attached wth command and acton, then the acton wll be effectve, and the command sent out (B). A reverse anmaton wll be performed when the mouse button s released so that the object backs to ts orgnal poston (C). An error state could be found through the detecton of the feedback process. Whenever an error occurs, the Clear button helps to clear the error-state of VCR on RS-232 port and reset t to an ntal state (e.g., Stop wth error-code=0). V. HYBRID DESIGN PROCESS: THE VALIDATION AND REVISION OF DESIGN RESULT BY THE SUPPORT OF VIRTUAL ENVIRONMENT OF DESIGN OK? The vrtual envronment of desgn takes the geometrc assembly (model) of a VCR controller as nput, and then defnes the control functons and anmatons on each functonal object n the model (the buttons n ths case). Now the desgner can valdate or examne hs desgn by actvate the functon and anmaton. Traverse over each button to check ts functon, push a button to see f the functon of a VCR connected s correctly trggered, and the desgner can even check f the movement of a key s correct. If there are some problems, he can modfy the desgn by nvokng a commercal CAD tool. Fgure 12 shows the extended desgn and revson flow of a desgn process. N Y Result Extended process of desgn and revson of electroncs wth the support of vrtual envronment of desgn VI. CONCLUSION AND CONSIDERATION Ths work demonstrated a whole pcture of a hybrd CAD tool and ts applcaton n the desgn of a VCR controller. As dscussed n ths paper, a vrtual envronment of desgn s sutable to desgn and test any knd of hybrd system composed of electronc and mechancal components. But due to ts complexty of a hybrd system, there are stll some conflcts between CAD tool and dynamc automaton left to be dealt wth [7]. Some contnuous abstractons about hybrd system are dscussed n [5]. All these ssues help ntensvely to the study and development of a hybrd CAD system, and should be taken nto consderaton n the future research work. A possble applcaton of ths vrtual envronment of desgn can be extended to the desgn of the control of ntellgent electronc home applance va Internet. Ths s easy to derve from current achevement. Another applcaton may be the remote control of NC (Numercal Control) machne n a manufacturng workshop. Even though ths research work provdes a prelmnary clue to access advanced CAD system (say vrtual desgn system) by the use of the methodology of vrtual envronment of desgn presented n ths paper, t stll shows the prospect of hybrd CAD technology, for that wth the help of hybrd CAD tool, the user can perform electromechancal valdaton durng the electronc applance desgn phase. Ths faclty provdes the desgner capablty of control upon whole applcaton set far beyond geometry. ACKNOWLEDGMENT The program of hybrd CAD tool was developed wth the support of the project of Tranng for Creatvty and Innovaton by Product and Process Desgn: A New Learnng Factory, an Area of Strategc Development (ASD) funded by the Hong Kong Polytechnc Unversty, and also by Desgn Technology Research Center (DTRC), School of Desgn of the Hong Kong Polytechnc Unversty. REFERENCES [1] Brancky, M., S., Borkar, V., S., and Mtter, S., K., (1998), A unfed framework for hybrd control, Model and optmal control theory, IEEE Transactons on Automatc Control, 43(1): pp [2] Lu, J., Lu, X., Koo T. K. J., Snopol, B., Sastry, S., and Lee, E. A., (1999), A herarchcal hybrd system model and ts smulaton, IEEE Conference on Decson and Control, Phoenx, December 1999 [3] Lygeros, J., Pappas, G., Sastry, S., (1999), Hybrd systems modelng, analyss, control, at [4] Pals Jr., J. and W. de Melo, (1982), Geometrc theory of dynamcal systems, Sprnger Verlag, New York. [5] Pappas, G., and Sastry, S., (1997), Towards contnuous abstractons of dynamcal and control systems, In Hybrd Systems IV, Lecture Notes n Computer Scence, 1997 [6] Smc, S., N., Johansson, K. H., Lygeros, J., and Sastry, S., (1996), The theory of hybrd automata, Proceedngs of the 11th Annual IEEE Symposum on Logc n Computer Scence (LICS 1996), pp

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