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基于CBR的排气消声器快速设计及评价方研究ResearchonCBR-BasedRapidDesignandEvaluationMethodofExhaustMufflerAThesisSubmittedtoChongqingUniversityinPartialFulfillmentoftheRequirementfortheDegreeofMasterofEngineeringByXiangFeiSupervisedbyProf.DengZhaoxiangMajor:VehicleEngineeringCollegeofMechanicalEngineeringChongqingUniversity,Chongqing,ChinaMay2011I摘要汽车排气消声器是多学科知识的有机结合体，各评价指标之间并不独立，文中建立了排气消声器综合性能评价体系，并结合领域专家知识，实现了多指标的综合定量评价，避免了采用单一指标进行逐一评价过程中产生的顾此失彼；排气消声器设计是弱理论强经验的设计过程，一个成熟的实例融合了大量的专家经验知识，基于实例的选型设计能够快速的匹配出与设计目标最相近的实例，不但取代了消声器原始设计方法中的概念设计，缩短了开发时间，还最大限度保留了专家设计经验知识，弥补了初级设计人员的经验不足。对排气消声器的各项性能要求所涉及的评价指标进行了详细阐述，从排气消声器的传递损失自身性能、匹配性能、插入损失性能和压力损失性能几个方面对排气消声器的性能定量化评价方法进行了详细的分析，建立了一种可量化的排气消声器综合性能评价体系。对传递损失曲线进行频段划分和消声量强弱等级划分，从平均消声量大小、消声低谷和强消声频段等级的角度实现了传递损失的自身性能评价；通过对目标发动机排气噪声和各转速下尾管噪声目标曲线的基倍频阶次分析，得到了所需设计的排气消声器具有频谱特性的消声量目标曲线，将传递损失曲线与消声量目标曲线进行比较，实现了传递损失的匹配性能评价；从插入损失值和各转速下尾管噪声达标情况两个方面对排气消声器的插入损失性能进行了评价；根据额定工况下的压力损失值和单位流量下的压力损失值对不同结构、不同系统的排气消声器空气动力学性能进行了评价；在传递损失曲线平均消声量和额定工况下插入损失值的评价过程中，综合考虑了容积、质量和连接管截面积的影响，引入了对排气消声器的工艺成本要求。采用定量与定性相结合的AHP决策方法获取了排气消声器综合性能评价指标体系的各项权重，完善了综合评价体系，并通过实例验证了评价体系的可操作性和可行性，为排气消声器的综合性能评价和匹配设计提供了依据。对排气消声器设计过程及基于实例的推理（CBR）过程的特点进行了对比分析，发现CBR推理过程与人类处理新问题的思维方式十分相近，论证了将CBR应用于排气消声器设计的可行性；根据CBR的推理过程提出了基于CBR的排气消声器快速设计思路和流程；详细阐述了基于框架的排气消声器实例知识表达方法，在现有的排气消声器实例的基础上建立了实例数据库；结合排气消声器综合性能评价体系，采用基于模糊相似优先比的最大相似度实例检索方法，从外形尺寸和性能要求方面实现了排气消声器的最优实例的检索，提出了匹配过程中实例数据的完整度概念，规定最优实例的选择应综合考虑数据完整度、数据相似度和II优先顺序；采用基于规则推理和人机交互相结合的方法实现了对实例的修改；采用增量式实例保存策略实现了对实例的保存；采用人机交互的方法来实现实例数据库的维护。最后通过VisualBasic.NET和MATLAB语言的联合编程实现了基于CBR的排气消声器快速选型设计系统，利用所开发的系统完成了一款排气消声器的选型设计，初步验证了系统的可操作性和实用性。关键词：排气消声器，综合评价，实例推理，快速设计IIIABSTRACTAutomobileexhaustmuffleristhemultidisciplinarycombinationwithindispensibleevaluationindexes.Basedonexpertknowledge,acomprehensiveperformanceevaluationsystemofexhaustmufflerhasbeenestablished,thecomprehensivequantitativeevaluationofmulti-indexofexhaustmufflerhasbeenimplemented,andthedoubtfulnessofcomparingthecasesrespectivelyaccordingtodifferentindexeshasbeenavoided.Exhaustmufflerdesignisatypicaldesignprocesswithexperienceoverweighstheory;amaturecaseincludedlargequantitiesofexpertexperienceknowledge.Basedonmaturecases,themostsimilarcasecanbeidentifiedveryquicklywithcase-basedreasoning(CBR),whichnotonlyreplacedconceptualdesignofthetraditionalmethod,butalsoretainedexpertexperienceknowledgeasmuchaspossible,itshortenedthedevelopmenttime,andmakedupforthelackofexperienceofJuniordesigner.Theevaluationindexeswhichassociatewithalloftheperformancerequirementsofexhaustmufflerhasbeendescribedindetailinthispaper,andthequantitativeevaluationmethodofexhaustmuffleralsohasbeenanalysisedintheaspectsoftransmissionloss,insertlossandpressureloss,then,aquantifiablecomprehensiveperformanceevaluationsystemofexhaustmufflerhasbeenestablished.Itdividedthetransmissionlosscurvesbyfrequencybandandbyattenuationabilityandachievedtheself-evaluationoftransmissionlossfrontthepointsofaveragesoundattenuation,lowtransmissionloss,intensitytransmissionlossandsoon.Thesoundattenuationtargetcurvehasbeenobtainedthroughtheorderfrequencyanalysisontheexhaustnoiseandthegoalcurveofthetailpipenoiseineachrotatingspeed,thetransmissionlossmatchingevaluationwascarriedoutbycomparingthetransmissionlosscurvewithsoundattenuationtargetcurve.Theinsertlossevaluationhasbeenrelizedfromthestudyofinsertlossvalueandthereachingstandardabilityofthetailpipenoiseineachrotatingspeed.Theaerodynamicsevaluationindicatorsofexhaustmufflerincludedthepressurelossofratedconditionandunitmassflow.theevaluationsystemconsideredtheinfluenceofvolume,qualityandconnectingpipecross-sectionalareaandalsotherequirementofprocesscost.TheweightsofevaluationsystemobtainedbyAHP,finally,theoperabilityandfeasibilityofevaluationsystemhasbeenverifiedthroughanexample,thustoprovidefoundationforexhaustmufflercomprehensiveperformanceIVevaluationandmatchingdesign.ThispaperdemonstratedthatapplyingCBRformufflerdesignisfeasiblebycomparingandanalyzingthecharacteristicsbetweenexhaustmufflerdesignprocessandcase-basedreasoning(CBR)process,proposedbasedonCBRexhaustmufflerrapiddesignideasandprocessesaccordingtothereasoningprocessofCBR,expoundedthemufflerexperiencecases'knowledgerepresentationmethodbasedontheframework,andestablishedtheinstancedatabasebyexistingcases，theoptimalcasesearchbythequalificationofdimensionsandperformancehasbeencarriedoutbythefuzzyanalogypreferredratioandthecomprehensiveperformanceevaluationsystem.Inthispaper,theconceptofinstancedataintegrityhasbeenputtedforward,andregulatedthatdataintegrity,datasimilarityandprioritiesshouldbetakenintoaccountwhenmakingtheoptimalchoice.ThecaseRevisehasbeenimplementedbasedonRule-basedreasoning(RBR)andHumanComputerInteraction(HIC);IncrementalcasesavingisemployedtosavecasesandHICtomaintainthedatabase.Finally,basedonCBRrapiddesignsystemofexhaustmufflerhasbeenimplementedbyVisualBasic.NETandjointprogrammingwithMATLAB,completedtheselectionofexhaustmufflerdesignwiththeassistanceofthesystem,themaneuverabilityandpracticabilityofselectionsystemhasbeenvalidated.Keywords：Exhaustmuffler,Comprehensiveevaluation,Case-bas