Research On Design Reuse System Of Soybean Seed Metering Device Based On CBR And Matter-element Model

With the development of manufacturing technology,the renewal cycle of agricultural equipment is shortened day by day.In the face of rapid and changeable market,it is a necessary way to improve the competitiveness of agricultural equipment production enterprises in China to Shorten the product design and development cycle,speed up the overall process of products,and meet the increasingly diversified and personalized needs of users.In practical production,the main work of product design is adaptive design and variant design.In the process of new product design,about 90%of the work is carried out on the basis of the existing design.Therefore,the reuse of product design knowledge plays an important role in improving the efficiency and quality of product design.As the core part of the planter,the performance of the seed metering device affects the working performance of the planter.The design process of the seed metering device contains a great deal of design information,rules and experiences.Therefore,it is of great practical significance to study the design reuse technology of seed metering device.This paper is based on the national key R&D project "Research on Intelligent Design Technology of Agricultural Machinery Equipment"(2017YFD0700100).In order to reuse the design knowledge of soybean seed metering device,shorten the design cycle and reduce the design cost,the product and design characteristics of soybean seed metering device were analyzed.The design and reuse system of soybean seed metering device is developed by using knowledge engineering principle and digital design modeling,virtual simulation and verification technology.The details of the study are as follows:(1)General framework and process of design reuse systemAccording to the design pattern and the characteristics of the design process of the soybean seed metering device,the general framework of the design reuse system of the soybean seed metering device is put forward,and the design reuse flow of the seeder is determined,It includes five parts:knowledge base,model base,case retrieval,case invocation and modification,virtual simulation and improvement,which provides a clear idea for the design and reuse system construction of soybean seed metering device.(2)Knowledge representation and knowledge base constructionBased on the analysis of the characteristics of the design knowledge of the soybean seed metering device,the classification and representation of the design knowledge of the seed metering device are studied.The design knowledge of seed metering device is divided into case class knowledge,rule class knowledge and data class knowledge.Representation of case-based knowledge by using materialized representation method and relational matrix.The knowledge representation of rule class and data class is represented by synthesis of production rule representation method,picture representation method and so on.The goal,structure and process of knowledge base of metering device design reuse system are studied.The knowledge base of soybean seed metering device is constructed,which includes materialized database and information base,it lays a foundation for the reuse of seed feeder design knowledge.(3)Research on model base and model construction methodThe model base corresponding to the knowledge base and the model building method suitable for design reuse are studied.The organizational structure of the model base,the coding rules and the construction requirements of the model base are determined.The hierarchical division of assembly driver,the method of parameter classification and naming,and the process of model construction are studied.The design method of program-driven parameterized model is proposed to realize variant design of model through interactive interface.The design rules and constraints are embedded in the case model.Through the secondary development of CATIA and the programming of parameter driver,the mutational design of interactive interface-driven model is realized.(4)Research on case retrieval strategyThe case retrieval strategy of the design reuse system for soybean seeder is studied.According to the requirement of design reuse and the characteristics of retrieval parameters,the retrieval parameters of the seed metering device are divided into basic parameters,matching parameters and evaluation parameters.The method of interface guidance and program judgment is used to realize the matching of basic parameters,so as to reduce the scope of case retrieval.The improved nearest neighbor algorithm is used to determine the matching parameters and the evaluation parameters,and the similarity calculation and the evaluation of the quality of the examples are realized.The weights of parameters are determined by AHP method and deviation maximization method,and the reusability of cases is determined by calculating weighted similarity.(5)Research on the method of case modificationThe method of combining program-driven parametric model with detailed design is used to modify the reusable seed metering device,and a matter-element expression model and a modification process based on the modified rule-related case modification are given.The rule association method is based on the comparison between the design requirements and the recommended reuse scheme parameters,using the system built-in rules to give the recommended modification parameters,combined with the modeling method of program-driven parametric model,the preliminary modification of the case model is realized.The engineering discrete element method is used to make the virtual simulation of the modified case.According to the results of the simulation analysis,suggestions for improvement are put forward,and the detailed design of the concrete structure is carried out by the designer in combination with the professional knowledge.(6)System integration and verificationThe interface of design reuse system is established.The method of establishing interface between interface and knowledge base and model base and the realization of retrieval algorithm are studied.Instance retrieval,instance model invocation and modification are implemented.The design reuse system of soybean seed metering device is built,and the system is tested.(7)Prototype testIn order to verify the usability and practicability of the design reuse system of the seeder,the prototype test of the reused and improved seed metering device was carried out.The results showed that the qualified index was 98.0%,the multiples index was 1.2%,the missed index was 0.8%,the Variation coefficient was 9.7%,and the damage rate was 0%,while working speed was 7 km/h.The working performance of the improved seed metering device has been improved.Existing similar examples to design requirements can be quickly acquired through a soybean seed metering device design reuse system.It’s beneficial to improvement metering device’s design efficiency,shorten the design cycle and reduce the design cost.At the same time,it can also provide technical reference for intelligent design of other types of mechanical equipment.