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Agent-Based Cooperative NC Conceptual Design Zhi Gang Xu Design Technology BinBj=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 := ll:=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: : : : : 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 under intense development. The future work will focuse on the solution qualification mechanism, now it depends mainly on the designers to compare the various conceptual structures, only after the computer tell which is feasible and which is better, can we realize some real form of creativity. This project is supported by the Shandong Provincial Excellent Young Scientist Award. 8. Reference l HU Weigang Development and Practice of Machine Tool Modularization and the Intelligent Supporting System, Doctoral