A knowledge-based approach for the task implementation in mechanical product designAbstract Although advances have been made to integrate the CAD system with design knowledge, there are still some barriers to apply the knowledge-based design approach to wide practice.A task implementation method is proposed for the mechanical product design process.The design task implementation model is constructed based on its organized-mode and modularity. Declarative knowledge primitives make up of the kernel composition of design task. It makes the design task more controllable and automatable. Solution of the knowledge primitives is directly used to drive the mechanical product. The proposed module has been developed for Intesolid2.0 system, a mechanical CAD system,and it has been evaluated with a design example of a two-stage gearbox.1 IntroductionIncreasing competition of the market forces enterprises to seek ways to be leading in product design and manufacturing. Design in early stages of development is advocated for application to engineering design to shorten and automate the development process. Computer-aided design systems are now being applied to up-stream design activities Integration of high-end mechanical computer-aided design (MCAD) systems with design activities and design knowledge would allow manufacturers to automate their engineering and manufacturing processes capturing the design rules, experience and expertise and leveraging it during new product development. The development of a product should take into account the issues of engineering performance, manufacturability, and cost. A pure geometric MCAD system only supports lowlevel design automation. It makes little use of design knowledge other than the designers dexterity with the MCAD tool, and cannot meet the expectation of customers for rapid design, rapid manufacturing, and high reliability. Knowledge-based engineering (KBE) provides a way of formalizing and automating product development. Design knowledge is utilized to expedite the cycle time from product design to manufacturing, at the time it assures the artifacts meet standards across design and manufacturing disciplines. A number of approaches to knowledge engineering for design task have been reported during the last two decades. These works have been concentrated on design task analysis and disjoint from MCAD system. However, design activities and knowledge should be deeply integrated into the system processes and effectively utilize the friendly interface of the existing CAD system. Though task analysis is also employed, the focus of this paper is on the knowledge representation scheme for task implementation in the MCAD system and an efficient reasoning and computation methodology for engineering knowledge.2 Related researchThis section describes related research that have been devoted to integration of the MCAD system with knowledge for the enhancement of productivity and reusability of KBE methodologies. In these research and developments, multilayered modeling approaches and the objectoriented method are commonly used to construct knowledge,design process, and product structure. Lee et al. 6 have suggested an integrated inference architecture of an intelligent CAD system for machine tools design. In this approach, the machine tools design problem is first decomposed into design modules, and design modules are decomposed further by actives. Four types of knowledge in activities, i.e., equations, if-then rules, multi-criteria descision-making rules, table and graph data, have been processed by a hybrid engine. However, the design problem is simply decomposed and the relationships between different design activities and different modules are ignored. Valasek et al. 7 presented the architecture of the COLIN system which is developed for motor vehicle design The design problem is represented by a network of basic design tasks (BDTs). Different BDTs are achieved by a special software tool ,such as AutoCAD, Matlab, Excel, Simulink, Lisp etc. A BDT is included in the task network according to whether its knowledge requirements are satisfied. The knowledge model is employed for the propose-revise control and selection of BDTs, but implementation of a specific design task is not well supported in the knowledge-based approach.Wong et al. 1 proposed four types of knowledge cells, i.e.,function cell, selection cell, graphics cell, and logic cell in the developed computer-aided logical design system. Different objects encapsulate the product form, design information, process, mail, and so on. Gorti et al. 11 also presented a knowledge representation model in their SHARED system and five objects to define design process, namely goal, plan, specification, decision, and context.The research presented in this paper provides a more natural way to integrate knowledge and design task into the MCAD system. A problem-solving method for knowledge primitives i