Parametric Design Model of Disc-scoop-type Metering Device Based on Knowledge Engineering. Yu Yang 1, a

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Parametric Design Model o Disc-scoop-type Metering Device Based on Knowledge Engineering Yu Yang 1, a 1 Department o Communication Engineering Engineering College o Armed Police Force, Xi an, China a miaoyude@163.com Keywords: Knowledge; Parametric design; Knowledge-driven; Disc-scoop-type metering device. Abstract. Traditional agricultural machinery design methods usually go through longer-design cycle and can hardly make good use o existing knowledge and experience. In view o this problem, parametric design theory and knowledge-based engineering were applied to the disc-scoop-type metering device designed to improve the design experience and reuse design knowledge. Through the knowledge-based parametric design method, the design ramework model o disc-scoop-type metering device was put orward. The knowledge library on the basis o design rules and characteristic similarity-based case library were created, and disc-scoop-type metering device parametric design system based on knowledge had been developed on the platorm o Pro/Engineering. The rapid design or knowledge-driven model o disc-scoop-type metering device was realized. The speciic design examples clearly indicated that the establishment o the system considerately improved the quality and eiciency o the design. Introduction At present agricultural machinery design has been converted rom the traditional data resource-intensive into inormation-intensive and knowledge-intensive[1]. In the design process, to avoid a large number o repeat development work, improve the eiciency o the products and save development costs, appropriate parameter design method is need to adopt or products o three dimensional modeling.the second design and the ollow-up design o the same series o products can directly realized through the use and modiy o the irst design. The traditional parametric design methods can only modiy geometry size o components, and can't modiy characteristics o components. Custom variables are independent and equation is inconvenience to be established between variable, parametric design cannot be ully embodied[2]. To solve the above problems, object-oriented technology is used to describe the characteristics o the products. Characteristic contains member variables and member unction or parametric changes, characteristic size values are as variables and make appropriate changes at any time. On this basis, characteristics and subsidiary relations between characteristics can change with certain conditions, parametric characteristics can be realized. In the design process, all the inormation o relevant design such as design standards, dimension association, dimension constraint and eature constraint are assembled together to constitute a design knowledge library and inspection knowledge library. A set o main design parameters is given, system can carry out derivation calculation according to the knowledge integrated in product model and generate product components modeling used or simulation test and drawing used to guide processing manuacturing. Designers can write good design experience and design method into the knowledge library to get the best design. In view o the design problem o disc-scoop-type metering device and using knowledge engineering thought, the device design knowledge library, case library, design reasoning module and ast modeling module are created to realize the device design knowledge as the driving orce to the design process to improve the eiciency and quality o the design. All rights reserved. No part o contents o this paper may be reproduced or transmitted in any orm or by any means without the written permission o Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/05/16,06:05:43)

2 Advanced Materials Research Vols The Design Framework Model Based on Knowledge The device design based on knowledge use basic thought o knowledge engineering and knowledge is used as the driving orce o design. Combining with the device design development characteristics, the device design rame model based on knowledge is created. The actual demand o user and market is used as original driving orce o design; machining characteristics are extracted rom demand. On the basis o knowledge library, non-geometry inormation such as structure types and materials are derived rom reasoning model based on Rule Based Reasoning(RBR), geometry inormation is got rom urther reasoning. Firstly, case are retrieved based on Case Based Reasoning(CBR), i there are similar device examples, they are modiied to produce new products and store into the base or next use. I there is no similar examples, Pro/Toolkit technology is used to design. Parameter Constraint. The disc-scoop-type metering device is made up o device shell, seed dropping wheel, metering scoop, diaphragm, hopper[3],it is shown in Fig.1. When the device is working, the seeds low rom the hole in bottom o hopper into illing seeds area o metering cavity with gravity. When the metering scoop turns driven by shat, the seeds o illing seeds area low into seed holding space combined o metering scoop and diaphragm. Seeds driven by metering scoop make circular motion and inish metering rom lower to upward o metering device. When seeds run to the top o device, with eect o gravity and thrust o scoop, seeds all into dropping wheel through the opening o diaphragm and are driven by dropping wheel rom protecting section to seed-throwing mouth. Under the action o gravity and the centriugal orce, seeds separate rom metering device to complete seed-throwing process[3]. Design parameters o disc-scoop-type metering device are usually given by equation or equations and also may be determined by the design rules. Dropping Frequency.Parameters determining dropping requency are scoop number i and rotating angular velocity ω.the relation is shown in Eq.1. ω = i π 2 (1) Diameter o Metering Scoop D.The size o structure dimension and volume o planter are decided by diameter o metering scoop. D max = v i d π max (2) v is metering linear velocity, i d is the number o spade, max is dropping requency. Angle θ z o Metering Scoop Rolling out Seeds. H is the height o seed surace, r is radius o metering scoop, µ is the natural angle o repose o seed. π r H θz = µ + arcsin 2 r 1.Device shell 2. Seed dropping wheel 3.Metering scoop 4.Diaphgram 5.Hopper Fig.1 Structure o disc-scoop-type metering device (3)

3 1434 Research in Materials and Manuacturing Technologies Seed Holding Space. Seed holding space is ormed by a column and a rectangular pyramid. The volume o seed holding space is main parameter o metering scoop design and is decided by thickness o the top metering scoop and inclination angle o cylindrical relative to the diaphragm. h s is thickness o the top o metering scoop in direction o oblique cylindrical. hs hmax< < 2hmin cosαy (4) Hp is the height o metering scoop away rom inner wall o metering device. h max < Hp< 2h min (5) θ is the central angle o intersecting part between oblique cylindrical and pyramid. 1 1 lmax lmax arcsin2 >θ > arcsin3 d y d y 2 2 (6) h max is maximum thickness size o seed, h min is minimum thickness size o seed, α y is angle o oblique cylindrical, d y is diameter o oblique cylindrical, l max is maximum length o seed. Objected-oriented Constraint Model.Expression and satisaction o constraints is the core o the model. Design calculation process o disc-scoop-type metering device is that crop species, seed varieties, agricultural production requirements, planter state index are set to determine metering scoop numbers and diameter o metering scoop. I the structural demand is met, interrelated dimensioning o seed holding space o metering scoop is calculated, whether seed holding needs meet requirements is tested, the wheel diameter is calculated and other related size calculation o device is completed. Finally dropping requency is calculated. In the whole process, parameters based on certain conditions such as expressions and sequence are selected and calculated. In the parametric design o device, document structure o components is made up o several characteristics, size, variables and geometric structure expressed by CSG and Brep. Establishment o Knowledge Library and Case Library Design knowledge must be described accurately and comprehensively in disc-scoop-type metering device design knowledge library. At the same time, appropriate methods are used to describe the knowledge and it is easy or computer storage and extraction o knowledge or design system. Knowledge is expressed mainly by expression method o rules in the design system. Knowledge extraction is carried out in the existing mature design experience theory ormula and mature product, knowledge is transormed to rules by condition express sentence o VC++ or design reasoning module. The device design knowledge o design knowledge library contains dropping requency knowledge, metering scoop structural knowledge, diameter choice o scoop, seed clearing angle choice knowledge, seed holding choice knowledge[3].design rules described in knowledge library can be described in a certain way, and a lot o design experience is diicult to extract and describe, they already exist in the mature product design. Thereore, case library is created as a complement to knowledge library and make the design knowledge more completely as a driving orce. Creation o case library mainly includes description, retrieval and management o existing mature device. Case retrieval and matching are achieved by similarity o characteristics. Similarity is calculated in main components level and the whole device level, similarity threshold is set to conirm inal retrieval and matching case. Case database is created by dierent module according to application range o the device. Fast Modeling Fast modeling module is carried out based on Pro/Toolki.Through the Pro/Engineer integrated internal procedures (Dll) or external application (exe), sel-deined application program, design

4 Advanced Materials Research Vols planning and drawing automation are provided or users. The creation o device shell is adopted Pro/Toolkit base class and creation o metering scoop and dropping wheel is adopted custom class to realize. Through the combination o Pro/Toolkit, UIStyler dialog box and menu, reasoning parameters are transormed into three dimensional solid models. Parameters such as crop species(maize),seed species(shennong31),seed spacing(136mm), sowing depth(70mm),marching speed(2000mm/s),plant spacing(272mm), vertical angle(23o),level angle(8o) are inputted in parameters setting area. Through the design reasoning, the system can automatically calculate and control key parameters o components, complete components generation and assembly, generate three-dimensional model. Components solid model are shown in Fig.3.Three-dimensional model o disc-scoop-type metering device is shown in Fig.4. (a)metering scoop (b) Diaphragm (c)dropping wheel (d) Device shell (e) Axis Fig.3 Components solid model Fig.4 Pro/E assembly option and assembly o metering device Conclusion In this paper, disc-scoop-type metering device design rame model based on knowledge was created combining with knowledge engineering and Pro/Toolkit technology in order to solve the problem o little comprehensive utilization o knowledge resources in traditional agricultural machinery design. Knowledge library, case library, reasoning module and ast modeling module were designed. Meanwhile, disc-scoop-type metering device parametric design system based on knowledge was developed as well. Knowledge engineering was applied in parametric design and knowledge o designer and engineering personnel were blended in the design cycle, which reduced errors, carried on automatic design and improved design eiciency. The design system had been veriied by application cases as ollows: it could provide lower cost, improved quality and rapidly developing product approach to designers. Acknowledgment This work was inancially supported by the National Natural Science Foundation ( ), Engineering University o Armed Police Force basic research und (WJY201307) Corresponding Author Yu Yang, miaoyude@163.com, Reerences [1] Yan Chuliang,Yang Fangei,Zhang Shuming: TRANSACTIONS OF THE CHINESE SOCIETY OF AGRICULTURAL MACHINERY.Ei. Forum Vol. 35 (2004), p. 211 [2] TAI Ligang, ZHONG Tingxiu: Journal o Donghua University.Ei. Forum Vol. 22 (2005), p. 22 [3] Li Chenghua,Xia Jianman,He Bo:TRANSACTIONS OF THE CHINESE SOCIETY FOR AGRICULTURAL MACHINERY.Ei. Forum Vol. 36 (2005), p. 48 [4] ZHOU Hao,ZHU Wen-hua,CHEN Peng: Manuacturing Automation. Forum Vol. 33 (2011), p. 71

5 Research in Materials and Manuacturing Technologies / Parametric Design Model o Disc-Scoop-Type Metering Device Based on Knowledge Engineering /