Extension design is a new, original and modern design methodology which applies extension theory to mechanical design to solve contradictory problems intelligently. It can establish formal modeling, transformation, reasoning, evaluating and decision making to solve competing problems with an optimal strategy.

1 Fundamental of extension design

1) Knowledge expressing and problem modeling in extension design
Extension design knowledge is applied to express contradictory problems in design process, which is able to change under some condition. The problems may be incurred by subjective expectation and objective environment, and corresponding basic element model. The model has expansion of transformable objectives as its foundation, investigates conversion of contradictory problems and constraint matching mechanism, and finds out in-deep core sub-problems in formal fashion.

2) Feature domain and transformation mechanism of extension design
Feature domain in extension design emphasizes reclassification, mapping between multidimensional basic element domains in diverse design space, active and incurring transformation. Feature transformation mechanism mainly investigates transformation rules of basic element , which can be roughly categorized into common and individual ones.

3) Reasoning and decision making in extension design
Extension design reasoning mainly investigates expansive, conjugative and transmissible reasoning process to solve ?a series of problems in complex and dynamic design systems. It creates extension design reasoning and improves reasoning means in terms of cases, rules and models to achieve the goal. Extension decision-making has dependent function and evaluating model as multiple evaluation objectives, and puts forward evaluation model in terms of enhanced scheme degrees under some circumstance.

2 Innovative features of extension design

1) It has solved the problem of time-varying design characteristic knowledge expression and participated in intelligent knowledge solving and conversion.

2) It improves information integration and mapping of different types, and achieves seamless integration between multiple design phases.

3) It helps conversion of design problems and solving of multiple objectives and schemes repeatedly until an optimal design is achieved.

3 The methodology system of extension design

1) Extension concept design. Extension theory, the fuzzy theory and optimization technique comprehensive are used in the study. Some new ideas, new principles and new methods of the concept design are put forward respectively in the aspects of extension knowledge expression, decomposition and comprehensive, optimization and solving, reasoning and evaluation.

2) Extension innovation design. Design contradictions state is to be found and translated to target state. The law of innovative design thinking is revealed. The inspired design strategy is put forward and the reasoning rule of innovative concept is produced. The four aspects above are the key problems of extension innovation design.

3) Extension design evaluation and decision method. The model of extension comprehensive evaluation is established according to the optimal program in different conditions, generated strategy set, and the structure knowledge of product design.

4) Extension optimization design. The essence of the optimization design is to optimal solving the design problems of multiple targets, nonlinear, wrong structure, and inaccuracy design.

5) Extension configuration design. The key of the design method is to establish extension design model of product adaptability with the combination method based on quality and quantity. It reveals the conducting rules of product design and customer demand. Then extension transformation of heterogeneous design space will be realized, that is extension configuration of product family adaptability design.

6) Extension green design. The purpose of this method is taking environment attributes of the product inside life cycle as design task, goal and conditions. After that, service life and quality will be ensured through the reasoning transformation of green extension.

7) Extension design in computer realization method. The design theory is applied in the actual product design system, which makes it more intelligent. It regards the openness and expansibility of extension design as the characteristic, and producing beneficial products to the life and the production practice as the goal.

4 The research prospect of extension design

Extension design is complying with the design field tendency of "pursuing new and change". It regards solving contradictory problems as a breakthrough of innovative design, takes intelligent thoughts as the wings of innovative design, and solves the problem producing in the process of innovation design intelligently. It has high academic value in formatting the combination scientific theory. It has great scientific value in design development laws and improving the design success and agility else. Meanwhile, the method provides an effective tool to create stronger functions, better performances, and competitively price.

ZhaoYanWei：Professor, doctoral supervisor, is selected to be Zhejiang province "151 talents project", young and middle-aged subject leaders of Zhejiang University, member of the Chinese artificial intelligence council, intelligence committee members, member of an intelligent CAD committee.
Discipline feats: modern integrated manufacturing technology
Research direction: (1) intelligent CAD/CAM and its integration
(2) network design and manufacturing technology
Email: zyw@zjut.edu.cn