Research On Knowledge-based Rapid Modeling Technology Of Whole Product Parametrics

In order to meet the change from market demand to product diversification and customization,the primary problem faced by modern manufacturing enterprises is how to realize the iterative update of product design at a faster speed.How to construct a large number of product design and simulation models quickly,conveniently and accurately is an important issue for enterprises.Rapid modeling technology is the method to achieve the requirements.At present,aiming at a certain kind of specific product object,the rapid modeling technology,which has poor generality and is short of configurable product structure mapping,can not meet the more and more popular product customization needs;Most of the existing design knowledge representation researches are oriented to conceptual design,and the knowledge mapping of functional structure is not enough to support the mechanical product model with complex structure level;The existing integrated modeling methods focus on getting through the data transfer mode between different systems,and emphasize the fixed input and output mode between systems,which limit the wide application of integrated systems.To solve the problems in the existing rapid modeling technology,such as the poor adaptability and expansibility of the system,the lack of knowledge representation of the model constructing process,and the complexity of the modeling process,the author conducts research to knowledge-based parametric rapid modeling technology and knowledge-based CAD / CAE integrated modeling method.The main contents are as follows:(1)A frame-model representation method based on description semantics of modeling rule is proposed.Through the study of a large number of complex product modeling processes,a set of modeling rule description semantics is summarized to meet the parameterization requirements of the whole machine,a framework model expression system is established,and the model is described from the aspects of logic expression,graphic expression,geometric expression and semantic expression,so that the construction process of the parameterization model can be described comprehensively and accurately.The paper studies the realization process of product model instantiation under the frame-model system.The template of product realizes the whole machine parametric model construction from top to bottom,driven by the main parameters through the level by level virtual feature and virtual component instantiation iteration.The product template is iterated by virtual feature and virtual component instantiation step by step,so that people can realize the whole machine parametric model construction by main parameters driven from top to bottom.On this basis,we developed a parameterized modeling system based on frame model description semantics,which realizes the separation of frame and rule systematically.By predefining common model templates and using 3D visual display and interactive interface,users can easily and quickly construct complex models with as few steps as possible.It shows that the semantics are simple and easy to use,flexible and efficient,and have strong description ability.(2)A knowledge-based parametric method of frame-model is proposed.The paper studies the knowledge representation method for geometric modeling process,and proposes the representation method with “parameter-function-behavior-structure” design(PFBS),that is,based on the “function-behavior-structure” representation method,the knowledge representation is introduced at the parameter level,and then,through the interface of parameter-function,parameter-behavior and parameter-structure,the reasoning process driven by design knowledge is realized,from requirement to product function decomposition,to function behavior derivation,and finally to structure representation.Combining the PFBS representation method with the frame-model description semantics,the paper proposes a knowledge-based frame-model.The design knowledge exists in the frame-model as a constraint,which can drive the virtual features,virtual components,assembly constraints and other components of the frame-model.The paper studies the instantiation process of knowledge driven framework model.According to the different knowledge driven principles,the author proposes static framework model and the dynamic framework model of knowledge driven.(3)A Knowledge-based CAD / CAE integrated modeling method is proposed.The paper researched the integrated modeling requirements of electronic equipment CAD /CAE for thermal performance simulation.According to the requirements of model simplification,the paper analyzes the feature composition of 3D model,and proposes the feature simplification method based on rules.The feature simplification of CAD model is realized by taking the feature size parameter and feature volume weight as simplification rules.According to the requirements of CAE feature construction,the paper studies the representation of analysis features.And the extraction of analysis feature data in CAD model and the automatic construction method of analysis features such as contact thermal resistance and fluid domain in thermal simulation are realized by graphic algorithm.Finally,the feasibility of the methods are verified by the example test of the airborne case.(4)A rapid modeling system of whole product parametirc is developed,and related application verification is also carried out.The organization structure,framework and the components and functions of each module of the system are introduced in detail.Taken the airborne plug-in box of MCU as an example,through the rapid modeling system,the reasoning solutions of the function,behavior,structure and parameters of the airborne plug-in box of MCU are realized under the drive of design knowledge,and the design demand is transformed into the driving parameters of the model instance after the design demand parameters are set up.Finally,the geometric model of MCU case is obtained.Based on the geometry model of MCU and combined with the CAD / CAE integrated modeling system,the CAE model of MCU case is constructed.Taken the design requirement parameters as the boundary conditions,the performance of the model cooling system is simulated and verified.The result shows that the parameterization method of the whole frame model driven by knowledge is accurate and effective.