Abstract:In order to reuse the design knowledge of mechanical soybean seed metering device, shorten the design cycle and reduce the design cost, the design reuse technology of mechanical soybean metering device was studied. It’s difficult to describe the design knowledge qualitatively and quantitatively of the traditional knowledge representation method of case-based reasoning（CBR）, such as frame representation, semantic network representation, predicate logic representation and so on. In order to realize the visualization, standardization and unification of design knowledge, the product design knowledge was described in the form of case matter element which contained case name, characteristic attribute and measure value. The method was beneficial to the effective use of design knowledge. In order to facilitate case storage and retrieval, the organization structure and case creation method of the design reuse were studied, Classification of basic hierarchy by seed-metering device category, and a case base was constructed which case model was corresponding to the case matter element, and some case relational matter elements were contained in the case base. This kind of organization structure was beneficial to the retrieval and reuse of examples, which made the restorage of cases follow the rules and provided convenience for the management and maintenance of the case library. At the same time, the components of the products were no longer isolated individuals, which fully reflected the overall characteristics of the products. In order to quickly retrieve the instance that met the design requirements from the case library, the characteristic property parameters of the instance were divided into basic parameters, matching parameters and evaluation parameters. The retrieval range can be reduced to a specific type and operation speed of seed metering device for retrieval by the selection of basic parameters. Similarity of cases was calculated by using improved nearest neighbor algorithm. The weight of the attributes of an instance can be determined by expert scoring or analytic hierarchy process（AHP）method, which can reduce the amount of computation and improve the efficiency and accuracy of retrieval. In order to meet the specific design requirements of the user, the quantitative relationship between the design requirements and the structural parameters of the instance was established by using the method of rule association, and the rapid revision of the case was realized by modifying the key parts of the case-parameterized model. An example of mechanical soybean seed metering device design reuse was given, the case library was constructed by using Access and computer aided three-dimensional interactive application （CATIA）, and the retrieval, evaluation and correction system of metering device was developed by Visual Basic. According to the current job object, the feasibility of the similar metering device was verified by using engineering discrete element method （EDEM） software and the modification suggestions were put forward. Finally, the simulation and prototype test of the revised metering device were carried out. The results showed that the improved metering device can meet the current requirements. The feasibility and effectiveness of the design reuse technology was validated. At the same time, it can also provide technical reference for intelligent design of other types of mechanical equipment.
