| Agricultural machinery equipment has been a significant part of manufacturing industry.Traditional methods are still used for agricultural machinery product design,which lead to many problems such as long design cycle,repetitive design and difficulty in design reuse.Model design reuse technology is one of the significant ways to upgrade agricultural machinery equipment.Model design reuse technology integrates information and industrialization resource,which could effectively promote rapid design through reusing design data,shorting design cycle,and reducing design costs.So far the number of 3D agricultural machinery models has been increasing dramatically.It is the key for model retrieval reuse to effectively satisfy all-round and diverse retrieval needs of agricultural designers.This paper researches on model retrieval methods designed for agricultural machinery unique features including universality,specificity and partial coupling.The goal is to improve retrieval accuracy and applicability for 3D agricultural machinery model and promote intelligent and rapid design.The following are the research contents and highlights of that work:(a)A 3D agricultural CAD model database for design reuse is established.Model database is the foundation to improve the accuracy and applicability of retrieval methods.Besides,specific database should be designed for a certain domain,which needs specific retrieval methods.Therefore,an agricultural machinery database is established through synergic companies,website,and self-modeling collection.The database is mainly composed of tractor and combine-harvester models,which also contains universal and some key component models of agricultural machinery equipment.The established database is comprehensive and systematic,which could offer sufficient models for retrieval method study.(b)A shape distribution retrieval method based on adaptively dynamic weighting is presented.This retrieval method is designed for simple and universal models retrieval which successfully uses the fast and stable advantages of traditional shape distribution method.The improvement focuses on sampling rule and multi-feature fusion aspects.The results show that the improved method not only sufficiently integrates line and surface,interior and exterior,distance and curvature features,but also effectively weaken the indistinctive features.Consequently,the resolution of shape distribution retrieval method improves.(c)A new model retrieval method based on multi-resolution 3D wavelet transform is studied,which is designed for complex and functional models in agricultural machinery database.This method transforms spatial feature extraction into frequency domain with 3D wavelet transform.Besides,the analytic hierarchy process is introduced to calculate the similarity between different frequency subspaces.The results present that two-level wavelet transform is enough to satisfy the accurate requirement of complex and functional models at present.Based on multi-resolution 3D wavelet transform,the new retrieval method effectively improves the accuracy and applicability for complex and functional models.(d)A partial retrieval method with light propagation is proposed.It is found that partial coupling features of agricultural machinery models mostly locate inside model.However,most feature extraction of traditional methods merely depends on model surface information,which extremely limits the effectiveness of partial feature extraction.Light could transmit through most substance.Therefore,the Monte-Carlo method can be used to simulate light propagation track within 3D model,and the hidden partial feature can be extracted with various propagation information.The results show that the extracted partial features could reflect model internal and surface features,which sufficiently satisfy partial feature retrieval requirementThose specific methods realize multilevel model retrieval for agricultural CAD model,covering spatial domain feature,frequency domain feature,global feature and local feature.Based on the above results,a retrieval system prototype for agricultural machinery equipment design is developed.The prototype realizes the comprehensive integration of retrieval methods and design resource,providing a reproducible and available example for agricultural machinery equipment rapid design. |
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