




已閱讀5頁,還剩1頁未讀, 繼續(xù)免費(fèi)閱讀
版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請(qǐng)進(jìn)行舉報(bào)或認(rèn)領(lǐng)
文檔簡介
Proceedings ofthe2006 IEEE/RSJInternational Conference on Intelligent Robots and SystemsOctober9- 15, 2006, Beijing, ChinaANovelModularFixtureDesignandAssemblySystemBasedonVRPengGaoliang, LiuWenjianSchoolofMechatronicsEngineeringHarbinInstituteofTechnologyHarbin, 150001, Chinapgl7782a Abstract - Modular fixtures are one oftheimportant aspectsofmanufacturing. This paper presents a desktop VR system formodular fixture design. The virtual environmentis designed andthe design procedure is proposed. It assists the designer to makethe feasible design decisions effectively and efficiently. Ahierarchical data model is proposed to represent the modularfixture assembly. Based on this structure, the user canmanipulate the virtual models precisely in VE during the designand assembly processes. Moreover, the machining simulation formanufacturing interaction checking is discussed andimplemented. Finally, the case study has demonstrated thefunctionality of the proposed system. Compared with theimmersive VR system, the proposed system has offered anaffordable andportable solutionformodularfixtures design.Index Terms - Modularfixture, desktop VR, assembly design,machiningsimlulation.I. INTRODUCTIONModular fixtures are one of the important aspects ofmanufacturing. Proper fixture design is crucial to productquality in terms of precision, accuracy, and finish of themachined part. Modular fixture is a system of interchange-eable and highly standardized components designed tosecurely and accurately position, hold, and support theworkpiece throughout the machining process 1. Tradition-ally, fixture designers rely on experience or use trial-and-error methods to determine an appropriate fixturing scheme.With the advent of computer technology, computer aideddesign has been prevalent in the area of modular fixturedesign.In general, the associated fixture design activities, namelysetup planning, fixture element design, and fixture layoutdesign are often dealt with at the downstream end of themachine tool development life-cycle. These practices do notlend themselves well to the bridging of design andmanufacturing activities. Forexample, very few systems haveincorporated the functionality of detecting machininginterference. This leads to a gap between the fixture designandmanufacturing operationswheretheaspectofcutterpathsis not considered during the design stage 2. As a result, re-designcannotbeavoidedwhenthecutterisfoundtointerferewith the fixture components in the manufactu- ring set-up.Therefore, in orderto bring machining fixture design into thearenaofflexiblemanufacturing, amoresystematicandnaturaldesignenvironmentisrequired.As a synthetic, 3D, interactive environment typicallygenerated by a computer, VR has been recognized as a verypowerful human-computer interface for decades 4. VRholds great potential in manufacturing applications to solveproblems before being employed in practical manufacturingthereby preventing costly mistakes. The advances in VRtechnology in the last decade have provided the impetus forapplying VR to different engineering applications such asproduct design 5, assembly 6, machining simulation 7,andtraining 8. The goal ofthis paper is to develop a VR-basedmodular fixtures design system (VMJFDS). This is thefirststepto develop anintegratedandimmersiveenvironmentfor modular fixture design. This application has theadvantages of making the fixture design in a natural andinstructive manner, providing better match to the workingconditions, reducing lead-time, and generally providing asignificantenhancementoffixtureproductivityandeconomy.II. OVERVIEWOFTHEPROPOSEDSYSTEMThe system architecture of the proposed desktop VRsystemismodularisedbasedonthefunctionalrequirements ofthesystem,whichisshowninFig.1. Atthesystemlevel,threemodules of proposed system, namely, Graphic interface(GUI), Virtual environment (VE) and Database modules aredesigned. For each ofthe modules, a set ofobjects has beenidentified to realize its functional requirements. The detailedobjectdesignandimplementation are omittedfromthispaper.Instead, the briefdescription ofthese three modules is givenbelow.1) Graphic Interface (GUI): The GUI is basically a friendlygraphic interface that is used to integrate the virtualenvironmentandmodularfixturedesignactions.2) Virtual environment (VE): TheVEprovidestheusers witha 3D display for navigating and manipulating the models ofmodular fixture system and its components in the virtualenvironment. As shown in Fig. 1, the virtual environmentmodule comprises two parts, namely assembly designenvironment andmachiningsimulationenvironment. Theuserselects appropriate elements andputs downthese elements onthe desk in the assembly design area. Then he assembles theselected elements one by one to build up the final fixturesystemwiththeguidanceofthesystem.1-4244-0259-X/06/$20.00 C)2006IEEE 2650Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. Fig.1.OverviewofthedesktopVRbasedmodularfixturedesignsystem.3) Database: The database deposit all of the models ofenvironment and modular fixture elements, as well as thedomain knowledge and useful cases. There are 5 databasesshown in Fig.1. Among them, knowledge & rule basegoverning all fixture planning principles forms the brains ofthesystem.III. PROCEDUREOFMODULARFIXTUREDESIGNIn this section, an instructive modular fixture designprocedure within VE is presented. Besides the 3D depth thatthe users feel and the real-world like operation process, thisprocedure features intelligence and introduction. During thedesign process, some useful cases and suggestion will bepresented to the user for reference based on intelligentinference method such as Case based reasoning (CBR) andRule based reasoning (RBR). Further more, relativeknowledge andrules arepresented ashelppages thattheusercaneasilybrowsedduringthedesignprocess.Overview of modular fixture design process issummarized in Fig. 2. After the VE environment is initialedandthe workpiece is loaded, the first step is fixtureplanning.Inthis step, theuserfirstdecides thefixturing scheme, thatisspecifies the fixturing faces of the workpiece interactively.Forhelptheusersdecision-making, someusefulcasesaswellas their fixturing scheme will be presented via the automaticCBR retrieval method. Once the fixturing faces are selected,theusermaybepromptto specifythefixturingpoints. Inthistask, somesuggestions andrulesaregiven.After the fixturing planning, the next step is fixture FUsdesign stage. In this stage, the user may be to select suitablefixture elements andassembletheseindividualparts into FUs.According to the spatial information ofthe fixturingpoints inrelation to the fixture base and the workpiece, some typicalFUs and suggestions may be presented automatically. Thesewillbehelpfulfortheuser. AftertheplanningandFUs designstage, the next stage is interactively assembling the designedfixtureFUstoconnecttheworkpiecetothebaseplate.When the fixture configuration is completed, the resultwill be checked and evaluated within the machiningenvironment. The tasks executed in this environmentincluding assembly planning, machining simulation, andfixture evaluation. Assemblyplanning isusedto gain optimalassembly sequence and assembly path of each component.Machining simulation is responsible for manufacturinginteraction detection. Fixture evaluation will check andevaluate the design result. In conclusion, the whole designprocess isinanaturemannerforthebenefitofVE. Moreover,the presented information of suggestion and knowledge canadvise the user on how to make decisions ofthe best designselection.IV. ASSEMBLYMODELINGOFMODULARFIXTUREA. ModularfixturestructureanalysisA functionalunit(FU) is acombination offixture elementsto provide connectionbetweenthebaseplate and aworkpiece11. Generally, modularfixture structuremaybe dividedintothree functional units according to its basic structurecharacteristics, namely locating unit, clamping unit, andsupporting unit. The number offixture elements in aFU mayconsist ofone or more elements, in which only one elementserves as a locator, support or clamp. The major task ofthemodularfixture assembly is to selectthe supporting, locating,clamping and accessory elements to generate the fixture FUstoconnecttheworkpiecetothebaseplate.By analyzing the practical application ofmodular fixtures,it is found that the assembly ofmodular fixtures begins byselecting the suitable fixture elements to construct FUs, thensubsequentlymountingtheseFUs onthebaseplate. Therefore,the FUs can be regarded as subassemblies ofmodular fixturesystem.Further,thestructureofmodularfixturesystemcanberepresentedasahierarchalstructureasshowninFig.3.2651Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. UsefTa6*T- siikg&Suggelr,lFixtuieElemenetsrUetrieval i0ToolsrKetrieval 4Fig.2ModularfixturedesignprocedureinproposedsystemB. Hierarchically structured data modelfor modularfixturerepresentation in VEIt is common that the corresponding virtual environmentmay contain millions ofgeometric polygon primitives. Overthepastyears, anumberofmodel sub-division schemes, suchasBSP-tree 10 andOctrees,havebeenproposedto organizelargepolygonalmodels.However, formodularBa 1I_ 1 Hsreplalte Bansepla1nte Elements*Locatng ElementsL,cating UnitsAccessoryEllementsClamnpingElemnents!ClampingUnitsSupportingElemntsSupporting UfnitsAccessory ElementsFig. 3Hierarchical structureofmodularfixture systemdesign applications, the scene is also dynamically changing,due to interactions. For example, in design process, the partobject may change its spatial position, orientation andassembly relations. This indicates that a static representation,such as BSP-tree, is not sufficient. Further more, the abovemodels can only represent the topology structure of fixturesystem in the component level. However, to the assemblyrelationship among fixture components, which refers to themating relationship between assembly features that is notconcerned. In this section, we present a hierarchicallystructuredandconstraint-baseddatamodelformodularfixturesystem representation, real-time visualization and precise 3DmanipulationinVE.As shown in Fig.4, the high-level component based modelis used for interactive operations involving assemblies ordisassembles. It provides both topological structure and linkrelationsbetweencomponents. Theinformationrepresent- edin the high-level model can be divided into two types, ponent objects and assembly relationships. Componentobjects can be a subassembly or a part. A subassemblyconsists of individual parts and assembly relationshipsbetweentheparts.Component Level(Pt PartS SubassemblyAssemblyrelationshipFeature LevelFt3 FeatureFeature matingrelationshipt- -tPolygon LevelFZ-ll. PolygonFig.4ThehierarchicalstructuredatamodelinVEThemiddle-levelfeaturebasedmodelisbuiltuponfeaturesand feature constraints. In general, the assembly relationshipoften treated as the mating relationships between assemblyfeatures. Thus the featurebasedmodel isusedto describetheassembly relationship andprovides necessary information forspatial relationship calculating during assembly operation. Inthis model, only the feature relationships between twodifferent components are considered. The relationshipbetween features ofone element will be discussed in featurebasedmodularfixtureelementmodelingbelow.The low-level polygon based model corresponds to theabove two level models for real-time visualization andinteraction. It describes the entire surface as an inter-connected triangular surface mesh. More about how thepolygons organized of a single element will be discussed isthenextsection.C. ModularfixtureelementsmodelingAs we know, in VE, the part is only represented as anumber ofpolygon primitives. This result in the topological2652Authorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. relations- hips and parametric information are lost during thetranslation process of models from CAD systems to VRsystems. However, this important information is necessary indesign and assembly process. In order to fulfill therequirements, we present a modeling scheme for fixtureelementsrepresentationinthissection.The modular fixture elements are pre-manufactured partswithstandarddimensions. Afterthefixturingschemedesigned,the left job is to select suitable standard elements andassemblethese elements to formafixture systeminafeasibleandeffectivemanner. Therefore, intheproposed system, onlythe assembly features of the fixture elements need to beconsidered.Inthispaperanassemblyfeature isdefinedas apropertyofafixture element, whichprovidesrelatedinformationrelevantto modular fixture design and assembly/disassembly. Thefollowing eight function faces are defined as assemblyfeaturesoffixtureelements: supportingfaces, supportedfaces,locating holes, counterbore holes, screw holes, fixing slots,andscrewbolts. Besidestheinformation aboutthefeatureliketypeanddimension, otherparameters, i.e. therelativepositionandorientationofthe featureintheelements localcoordinatesystem are recorded with the geometric model in the fixtureelement database. When one element assembles with another,the information aboutthematedfeatures isretrieved andusedto decide the spatial relationship ofthe two elements. Moreinformation about the assembly features and their matingrelationship arediscusseddetailedinRef 1.D. Constraintbasedfixtureassemblyin VE1)AssemblyrelationshipbetweenfixtureelementsMating relationships have been used to define assemblyrelationships between part components in the field ofassembly. According to the assembly features summarized inthe above section, there are fivetypes ofmating relationshipsbetween fixture elements. Namely against, fit, screw fit,across, andT-slotfit,which are illustrated inFig. 5. Based onthese mating relationships, we can reason the possibleassemblyrelationshipofanytwoassembledfixtureelements.2)AssemblyrelationshipreasoningIngeneral, the assemblyrelationship oftwo assembledpartisrepresented as thematedassembly featurepairs ofthem. Inthe above section, we defined five basic mating relationshipsbetween fixture elements. Therefore, it is enabled to decidethe possible assembly relationships through finding thepossible mating assembly feature pairs. These possibleassembly relationships are saved in assembly relationshipsdatabase(ARDB)forfixtureassemblyinnextstage.However, when the fixture is complicated and thenumbers ofcomposite fixture elements is large, the possibleassembly relationships are too much to take much time forreasoning andtreating. To avoidthis situation, wefirstdecidethe possible assembled elements pairs. That is to avoidreasoning the assembly relationship between a clamp andthebaseplate, for they never were assembled together. In thisstage, some rules are utilized to find the possible assembledelementspairs.The algorithm of assembly relationships reasoning issimilar to what discussed in Ref 12. Thus the detaileddescriptionofthealgorithmisomittedfromthispaper.(a) AIlai.ns.2l.I.FLIi I7F d) Asicmie 1f-isxkt ElmnFig. 5Fivebasicmatingrelationshipsbetweenfixtureelements3)Constraint-basedfixtureassemblyAftercarrying outthe assemblyrelationships reasoning, allpossible assembly relationships ofthe selected elements areestablishedandsavedinARDB. Basedontheserelationships,the trainee can assemble these individual parts to a fixturesystem. This section is about the discussion of interactiveassembly operation in VE. The process ofa single assemblyoperation is presented in Fig.5 and illustrated by two simplepartsassemblyasshowninFig.6.In general, the assembly operation process is divided intothree steps, namely assembly relationship recognizing,constraint analysis and applying, constraint-based motion.Firstly, the trainee selects an element and moves it to theassembled component. Once an inference between theassembling and assembled component is detected during themoving,the inferredfeatures is checked. Ifthetwo features isone of the assembly relationships in ARDB, they will behighlighted and will await the users confirmation. Once it isconfirmed, the recognized assembly relationship will beappliedby constraint analyzing and solving, that is adjustthetranslationandorientationoftheassemblingelementtosatisfythe position relationship ofthese two components, as well asapplythenew constrainttotheassemblingelement.Whenthenew constraint is applied, the motion of the assemblingelement will be mapped into a constraint space. This is donebytransferring 3Dmotiondatafromtheinputdevicesintotheallowable motions ofthe object. The constraint-based motionnotonlyensuresthattheprecisepositionsofacomponentcanbe obtained, but also guarantee that the existing constraintswill not be violated during the future operations. Theassembling element will reach to the final position throughsuccession assembly relationship recognizing and constraintapplying.2653Ii1-114-(b) F.tAuthorized licensed use limited to: Nanchang University. Downloaded on December 20, 2009 at 22:44 from IEEE Xplore. Restrictions apply. NOAssembly relationship Iis possiblechecking elatioohship?Fig. 6ProcessofassemblyconstraintestablishmentNoV. MACHINING SIMULATIONA. ManufacturinginteractionsDuring the machining process, there are many types ofmanufacturing interactions associated with the fixture mayoccur. These interactions can be divided into two broadcategories illustrated below, namely static interactions anddynamicinteractions.1) Static interactions refer to the interference betweenfixture components, the interference between fixturecomponents and machine tool, and the interference betweenfixture components andmaching feature ofworkpiece duringtheworkpiecesetup.2)Dynamicinteractionsrefertothetool-fixtureinteractions,whic
溫馨提示
- 1. 本站所有資源如無特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請(qǐng)下載最新的WinRAR軟件解壓。
- 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請(qǐng)聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
- 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁內(nèi)容里面會(huì)有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
- 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
- 5. 人人文庫網(wǎng)僅提供信息存儲(chǔ)空間,僅對(duì)用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對(duì)用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對(duì)任何下載內(nèi)容負(fù)責(zé)。
- 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請(qǐng)與我們聯(lián)系,我們立即糾正。
- 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對(duì)自己和他人造成任何形式的傷害或損失。
最新文檔
- 基于人工智能的2025年智慧交通流量預(yù)測(cè)技術(shù)發(fā)展動(dòng)態(tài)報(bào)告
- 建筑施工安全監(jiān)測(cè)方法試題及答案
- 城市交通擁堵治理2025年公交優(yōu)先戰(zhàn)略的實(shí)施效果分析報(bào)告
- 匯和銀行筆試題庫及答案
- 黃巖區(qū)面試真題及答案
- 黃河委面試真題及答案
- 安全工程師考試常識(shí)題目試題及答案
- 工業(yè)互聯(lián)網(wǎng)背景下量子通信技術(shù)2025年應(yīng)用前景分析報(bào)告
- 物理學(xué)中的混沌現(xiàn)象研究試題及答案
- 智能建筑系統(tǒng)集成與節(jié)能降耗在體育場館中的應(yīng)用效果研究報(bào)告
- 廣東省珠海市2024-2025學(xué)年高二下學(xué)期期中教學(xué)質(zhì)量檢測(cè)英語試題(原卷版+解析版)
- 北京2025年中國環(huán)境監(jiān)測(cè)總站招聘(第二批)筆試歷年參考題庫附帶答案詳解
- 美國加征關(guān)稅從多個(gè)角度全方位解讀關(guān)稅課件
- “皖南八?!?024-2025學(xué)年高一第二學(xué)期期中考試-英語(譯林版)及答案
- 2025-2030中國安宮牛黃丸行業(yè)市場現(xiàn)狀分析及競爭格局與投資發(fā)展研究報(bào)告
- 防洪防汛安全教育知識(shí)培訓(xùn)
- 安寧療護(hù)人文關(guān)懷護(hù)理課件
- 2025年廣東廣州中物儲(chǔ)國際貨運(yùn)代理有限公司招聘筆試參考題庫附帶答案詳解
- 商場物業(yè)人員缺失的補(bǔ)充措施
- 黑龍江省齊齊哈爾市龍江縣部分學(xué)校聯(lián)考2023-2024學(xué)年八年級(jí)下學(xué)期期中考試物理試題【含答案、解析】
- 《尋常型銀屑病中西醫(yī)結(jié)合診療指南》
評(píng)論
0/150
提交評(píng)論