Chen Zhengming

A New Approach for Naming and Identifying Topological Entities

One of the fundamental issues based on history parametric feature modeling is how to name and identify topological entities. And the essence of this issue is to maintain the implied design intent. Firstly, we define the directed isoparametric lines (DIL) on faces, and propose a new approach taking face as the core to name the referenced topological entities. Based on the DIL-based face-face relationship (FFR), the approach is implemented by using the local topological information as well as geometrical characteristics. Secondly, in order to identify a referenced topological entity, The adjacent faces of the entity are divided into active face set and inactive face set, and the implied design intent is captured based on subset relationship criterion. The proposed approach has been tested by a number of examples, which shows the approach can deal with the case of topology variation more effectively.

A representation of freeform features based on characteristic curves

Owing to the diversity and complexity of freeform surface shapes, it is difficult to parameterize surface features and express their shapes effectively. A parametric approach for layering freeform surface features is proposed based on characteristic curves. A characteristic curve is a key element and is regarded as the basic unit for building surface shapes. A characteristic curve can be divided into four levels, comprising, from the lowest to the highest level, geometry, constraints, grammar, and semantics. The information is used to layer the parameters of a freeform surface feature so that the global and local shapes of the surface feature can easily be manipulated by the layered parameters. The global shape is controlled by the high parameters between multi characteristic curves, while the local shape is manipulated by these parameters with a single curve. According to the degrees of the surface and its parametric representation, freeform surface features can be divided into two types: semi-freeform and fully freeform. Then, the freeform surface feature is combined in the representation. Using various examples we show that the proposed method can fully express complex surfaces and is effective in defining freeform surface features, making it convenient for designers to edit freeform features from higher-level semantic parameters. Moreover, it provides an efficient way of representing freeform surface features.

The Case-Based Rapid Design System for Telescopic Boom

The rapid design system for the telescopic boom of truck-mounted crane is introduced. The architecture, implementation method and key technologies of the system are described. By applying the CBR (Case-Based Reasoning) technology as a new branch of AI to the design of the telescopic boom of truck-mounted crane, the design process of the boom is studied based on CBR. The three-dimensional parametric design system of the boom is implemented by the secondary development on Pro/Engineer based on its development module Pro/Toolkit. The integration system of the CBR technology and the CAD/CAE of the boom is developed with the help of Visual C++ and ANSYS Parametric Design Language (APDL) as tools.

Design System of the Second Order Cylindrical Gear Reducer on CBR

For the sake of improving design efficiency and intelligence, a design method of the second order cylindrical gear reducer based on CBR is presented in the paper. Firstly, the paper describes the principle of CBR. Secondly, three key technologies of CBR are studied and the corresponding methods are proposed, which are the object-oriented knowledge representation method, a retrieval method combining the nearest neighbor with the induction indexing, and case adaptation algorithm combining the revision based on rule with artificial revision. Meanwhile, for the sake of improving credibility of case retrieval, the paper presents a kind of new method determining the weights of characteristics and a similarity formula, which is a combinatorial weighting method with the analytic hierarchy process (AHP) and roughness set theory. Lastly, according to the above results, a design system of the second order cylindrical gear reducer based on CBR is developed by VC++¿UG and Access.