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Agent-Based Cooperative NC Conceptual Design Zhi Gang Xu Design Technology & Research Center, School o f Design, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong sdzhgxupolyu. edu. hk Abstract Creativity is a core issue of product design and development, so as is the machine tool that is implemented to make them. This paper presents a NC conceptual configuration model based on agent. Modularization is the fundamental of NC conceptual layout design. It takes each module as an autonomous entity participating in design activities, and the product design process is described as the organized cooperative work of agents. The Cooperative Muti-agent NC ConBguration (CMNC) system will greatly increase the designing efficacy as well as creativity by offering a large number of design options and a rudimentary evaluation mechanism. The prototype system, which is under further development, has showed great potential of creativity. 1. Introduction Creativity is the most competitive issue in product design and development, so does the machine tool that is implemented to make them. To date, the significant progress has been made in manufacturing technology, and a large number of FMS have been implemented mound the world. How ever with the ever increasing trend of individulization of products, agile manufacturing, rapid product design and develoopment etc have attracted more and more attention. Quick and creative design of NC (Numeracal Controlling Lathe etc) system is becoming even more significant. Conceptual design which affect 70 % (or more) the whole cost, but only accounts for 10 % of the budget, is under the way of in depth investigation. Modularization is an effective way of NC system conceptual design and development, which is a simple way to express the structure of the system, also has enough flexibility in developing new structures. To incease the design efficacy, expert system is introduced to the mechanical design systems. While traditional expert systems, which a r e mostly sequential single-purpose systems definately lead to low efficiency. Agent and Ke Zheng Huang, Wei Min Liu CAD Center College o f Mechanical Engineering, Shandong University, Jinan, Shandong, P.R. China k-z-huang, taolwmsdu, multi-media techniques make it possible to cooperate several designers to do the same designing task on the basis of Computer Supported Cooperated Work (CSCW)21. This article proposed a new approach of agent oriented Creative NC Configuration Design system. The rest of this paper is organized as the followings: section 2 is a brief introuction of NC system modularization, section 3 describes the architecture and the function of agent. Section 4 proposes the agent oriented NC system design model. In section 5, 6 one design example is exploited to demonstrate the design process. 2. NC Modularization 2.1. Module Definitions Three typical modules are introduced to express the NC conceptual layout. They are: translation module, rotation module and base module (as Fig.1 (a). Their definitions are as follows: Definition 1: Base module, support the translation or rotation modules which can not move or rotate, denoted by B, where H-B denotes the horizontal module, V-B denotes vertical module. Definition 2: Translation module, supported by base module or rotation module which can move along one corrodinate direction x,y,z, denoted by H-X, H-Y and H-V accordingly. Definition 3 : Rotation module, supported by base module or translation module which can rotate around one corrodinate axis: x,y,z, denoted by R-X, R-Y, R-Z accordingly, while R-H, R-V means module rotating on the horizontal or the vertical base module. Deduction: One rotation module can not be connected with another rotation module. 354 3. Function and Structure of the Agent An agent contains five modules (Fig.2). The function and performance of the modules are as follows: Acquaintance module is the representation of other agents and of the local domain level system respectively. Cooperate module is responsible for managing the agents social activities, the need being detected by the situation assessment module. Control module is the interface to the domain level system. Situation assessment module decides which activities should be performed locally and which should be delegated to other agent, which requests for cooperation should be honored, how requests should be realized, what action should be taken as a result of freshly arriving information, etc. It issues instructions to, and receives feedback from the other modules. The remaining components provide support function. The self- module is a repository for all the data which the underlying domain level system has generated or which has been received as a result of interaction with others. The communication manager sends and receives messages to/from other agents in the community. Z Z H-Y ) 5-axis NC layout anangrmcnt 0 C shapcdring list Fig.1 Module definition and 5-Axis NC conceptual layout. 2.2. Module Constraints From the above definitions., the following Module Constraints can be deduced: R i m j = 0; BinBj=l; & n H j =l; 0 I 8. n Bj = 1; illigle :1 :ligile following design constraints can be got: According to the design specifications of lathe, the 1) if the workpiece is heavy, then the workpiece can not move vertically; 2) ifthe workpiece is in high precision, then the workpiece is fixed or has only one translation movement; 3) ifthe workpiece is heavy and in high precision, then the workpiece jig must be adjacent with the base; . . . . . . . . . . . . . . . . . . . 2.3 Module Display The NC conceptual layout model can be expressed precisely by arranging different modules in an explicit way. Fig 1.b is an example of five-axis NC layout model with x,y,z translation movement and A, B rotation. Fig1 .c is the C shape ring list mod.el. It is a close ring from cutter to workpiece. CONTROL MODULE Fig.2 Agent Architecture. Definition 4 : Agent is described as a sextuple : (Aid, Communication, Acquaintance, Cooperate, Assessment, Control). := := : := () :=l lll : := : := () : := lll := llIllegil :=lllIl := 355 4. Management of the Design Process Based on Agent The engineering design is viewed as a distributed system consisting of various autonomous entities completing the special task through cooperation 31. There are two kinds of basic elements in the system: entities and activities. The entity includes the CAD systems (dealing mainly with the graphic issues), users and various agents (information handling). Activity is the process of the entity performing the design process. In the designing process there are also two categories of information: Foreground and Background 4, Table 1 is the list of information and the corresponding activities and participants. Definition 5: The agent oriented cooperative design system DS is a quintuple A,Tr,Ev,OR, among which, A is the set of agents, Tr is the design Transaction, E is the set of events, OR is the organization (including CAD system, various users etc ) . Event is the state change of the system triggered by users, CAD system and agents taking part in the design process, cooperation between agents and the communication with the outside world. In this conceptual model, the product design processes is an activity set of a group of agents and activities undertaking by the cooperative work of agents with the interference of users. 5. Illustration of the Designing Process Definition 6. Event is a sextuple (EID, ESTATE, EPRE, EAG, EAC, EPOST), where EID is the name of events, ESTATE is the present system state, EPRE is the precondition triggering the event. EAG is the set of activated agent, EAC is the action taking by the agent, EPOST is the state caused by this event. Fig.3 give the event description. Eprb- conditio Estate participant Fig.3 Event Description. If the design of a complex NC miller is wanted, which can process turbine blade, the cutter should move simultaneiously in five axis, say x, y, z, A, B, i.e the cutter has 5 DOF (Degree Of Freedom). This is the design precondition. If the part is light, from the designing constraints in chapter 2.2 , the movement of the part has no limitations. Then the EPRO has two hues : 1. x,y,z,A,B five DOF of cutter, 2. the part property is light. Definition 7 : Transaction is a sequence of events, one transaction is an acceptable solution which can satisfy the module constrains and the designing: constraints. T:. . . . . . EID: : : : :agent state? 1: allowed; 0: forbidden : 1 : interactable; 0: uninteractable. NC milling machine has a C list structure which take the workpiece as the starting point and the cutter as the ending point 51 or vice versa. So the design activity process with workpiece, it first deal with the module which hold the workpiece. Table 1. 356 For event1 : EIDl : 0 0 the agent state EAG: EPRE: x,y,z,A,B five cutter DOF & (is light Part-ProPerty) 0 user: 0 waiting. 0 CAD system: 0 waiting. At this point all the modules can be triggered, if R-Y is triggered which can realize the: “y” translation. Then the condition will be changed. 0 So for the event2: EID2 0 0 EPOST: cutter lost one DOF (Degree of Freedom) EPRE: x,z,A,B four movement &( is light part agent state EAG: from the module constrains , R-Y can not connect with H-ES,H-V,R-V,R-Z, so the property) 0 user: 0 waiting 0 0 CAD system state: 0 waiting At this time, if the H-Z is. triggered, then: EPOST: cutter lost one DOF (Degree of Freedom) After six events , the DOF of cutter reached 0, one design transaction has been finished. The result of one transaction is viewed as one acceptable solution. Various possible solutions will be recorded and compared. Among each transaction, user will interact with CAD system, compare and talk about the existing solutions with other designers. Fig.1 (b) is one transaction, which denotes the 5 axis NC layout, though it. may not be the optimal solution. . . . . . . . . . 6. Example Fig.4 gives the tree structure multi-solution paradigm based on agent. In Fig.4, “Base-” isthe input or beginning. From this point, th.e whole system will work under the monitor of modular constraints. In the design process, lower modules derived upper modules, and it is divergent. More often than not, the result may go beyond the least conserved traditional conventions, some may seem to be ridiculous, but that. may means creativity. By introducing design constraini:s, the solutions may be converged greatly. With more constraints being introduced, the result may be more and more realistic. For example, the thickened curve followed by R-Y-T- Y-T-X-H-Base-V-Base-T-Z-R-X in Fig.4 is one feasible NC conceptual structure in Fig. 1 (c). L e _ l m ”l7q H-Base t Fig .4 Multi-Solution in NC layout design 7. Conclusion and Acknowlegement The NC structure conceptual design model based on agent described in this paper is now