【正文】 究?jī)?nèi)容本文的主要研究?jī)?nèi)容有：①. 總結(jié)關(guān)于消聲器設(shè)計(jì)、基于 CBR 的快速設(shè)計(jì)方法和消聲器綜合評(píng)價(jià)方法的國(guó)內(nèi)外相關(guān)理論和研究狀況；明確基于 CBR 的快速設(shè)計(jì)方法的理論實(shí)質(zhì)、適用范圍和特點(diǎn)；②. 完成排氣消聲器實(shí)例庫(kù)前期實(shí)例的實(shí)驗(yàn)、建模與性能分析；③. 獲取排氣消聲器實(shí)例產(chǎn)品各項(xiàng)相關(guān)結(jié)構(gòu)和性能相關(guān)參數(shù)，并采用 AHP 方法進(jìn)行權(quán)重影響分析研究；④. 通過對(duì)消聲器各項(xiàng)評(píng)價(jià)指標(biāo)及技術(shù)性能特征的研究，構(gòu)造一種能夠?qū)ε艢庀暺鬟M(jìn)行綜合性能評(píng)價(jià)的消聲器評(píng)價(jià)方法；⑤. 對(duì) CBR 系統(tǒng)中的實(shí)例表示、實(shí)例修改和重用等關(guān)鍵技術(shù)進(jìn)行研究，建立CBR 前期實(shí)例庫(kù)；⑥. 通過對(duì)相似實(shí)例匹配方法的研究，選取一種適合于排氣消聲器設(shè)計(jì)的最大相似度檢索方法，并應(yīng)用到 CBR 系統(tǒng)的實(shí)例檢索中；⑦. 構(gòu)建基于 CBR 的排氣消聲器快速設(shè)計(jì)系統(tǒng)，并基于該系統(tǒng)開發(fā)一款排氣消聲器。2008 年，姜鵬明等人首次將排氣消聲器綜合評(píng)價(jià)方法定量化，提出了以消聲量為出發(fā)點(diǎn)綜合考慮消聲器消聲效率和成本的汽車消聲器綜合評(píng)價(jià)指數(shù)[54]。2005 年路云等提出基于 CBR 的企業(yè)經(jīng)營(yíng)決策支持模型，通過對(duì)案例庫(kù)中記憶5的源案例企業(yè)的經(jīng)營(yíng)指標(biāo)進(jìn)行相似性搜索，在分析源企業(yè)實(shí)施的各項(xiàng)決策及實(shí)施后收到的經(jīng)營(yíng)效果的基礎(chǔ)上，對(duì)目標(biāo)企業(yè)未來經(jīng)營(yíng)策略進(jìn)行指導(dǎo)[49]；2007 年，楊方飛等研究了基于實(shí)例的設(shè)計(jì)機(jī)械領(lǐng)域變型設(shè)計(jì)中的應(yīng)用，并成功應(yīng)用于水泵的設(shè)計(jì)[50]；2008 年，童福安等開展了基于 CBR 的產(chǎn)品實(shí)例快速設(shè)計(jì)系統(tǒng)研究[29]。隨著 CBR 方法研究的逐步成熟，近年來國(guó)際上對(duì)于該技術(shù)的研究性開發(fā)項(xiàng)目和應(yīng)用系統(tǒng)達(dá)上百種，至少已出現(xiàn) 3 種使用 CBR 方法進(jìn)行機(jī)械產(chǎn)品設(shè)計(jì)的商業(yè)化工具，它們分別是 CADET[37]（機(jī)械設(shè)計(jì)輔助）、COMPOSER[38]（汽車裝配過程規(guī)劃）和 PANDA[39]（發(fā)動(dòng)機(jī)設(shè)計(jì)）。它是由目標(biāo)實(shí)例的提示而得到歷史記憶中的相似實(shí)例，并由相似實(shí)例來指導(dǎo)目標(biāo)實(shí)例求解的一種策略[30]；它不需要設(shè)計(jì)人員從案例中提取規(guī)則，從而解決了知識(shí)獲取的瓶頸，降低了知識(shí)獲取的難度，解決問題的速度快。由于一維聲波理論在工程實(shí)踐中往往難以滿足要求，常常會(huì)出現(xiàn)較大偏差，所以邊界元法與有限元法受到越來越多的重視，期間出現(xiàn)了大量運(yùn)用三維聲學(xué)、流體力學(xué)分析軟件進(jìn)行消聲器性能分析與設(shè)計(jì)的研究和論文[19][20]。隨著時(shí)間的變遷，排氣消聲器的設(shè)計(jì)由最初的單純經(jīng)驗(yàn)設(shè)計(jì)逐漸轉(zhuǎn)向?yàn)樵O(shè)計(jì)理論+經(jīng)驗(yàn)+計(jì)算機(jī)輔助工程+試驗(yàn)的多元化設(shè)計(jì)。通過對(duì)目前國(guó)內(nèi)消聲器設(shè)計(jì)特點(diǎn)的分析可以發(fā)現(xiàn)，實(shí)現(xiàn)排氣消聲器快速設(shè)計(jì)的關(guān)鍵是在提高設(shè)計(jì)系統(tǒng)智能化的前提下，有效地利用現(xiàn)有產(chǎn)品的設(shè)計(jì)信息資源和經(jīng)驗(yàn)。簡(jiǎn)而言之，目前國(guó)內(nèi)汽車產(chǎn)品制造企業(yè)之間的競(jìng)爭(zhēng)是圍繞時(shí)間、質(zhì)量、成本、服務(wù)和環(huán)境所開展的競(jìng)爭(zhēng)[4]。 a mature case included large quantities of expertexperience knowledge. Based on mature cases, the most similar case can be identifiedvery quickly with casebased reasoning(CBR), which not only replaced conceptualdesign of the traditional method, but also retained expert experience knowledge as muchas possible, it shortened the development time, and maked up for the lack of experienceof Junior designer.The evaluation indexes which associate with all of the performance requirementsof exhaust muffler has been described in detail in this paper, and the quantitativeevaluation method of exhaust muffler also has been analysised in the aspects oftransmission loss, insert loss and pressure loss, then, a quantifiable prehensiveperformance evaluation system of exhaust muffler has been divided thetransmission loss curves by frequency band and by attenuation ability and achieved theselfevaluation of transmission loss front the points of average sound attenuation, lowtransmission loss, intensity transmission loss and so on. The sound attenuation targetcurve has been obtained through the order frequency analysis on the exhaust noise andthe goal curve of the tail pipe noise in each rotating speed, the transmission lossmatching evaluation was carried out by paring the transmission loss curve withsound attenuation target curve. The insert loss evaluation has been relized from thestudy of insert loss value and the reaching standard ability of the tail pipe noise in eachrotating speed. The aerodynamics evaluation indicators of exhaust muffler included thepressure loss of rated condition and unit mass evaluation system considered theinfluence of volume, quality and connecting pipe crosssectional area and also therequirement of process cost. The weights of evaluation system obtained by AHP, finally,the operability and feasibility of evaluation system has been verified through anexample, thus to provide foundation for exhaust muffler prehensive performanceIVevaluation and matching design.This paper demonstrated that applying CBR for muffler design is feasible byparing and analyzing the characteristics between exhaust muffler design processand casebased reasoning (CBR) process, proposed based on CBR exhaust muffler rapiddesign ideas and processes according to the reasoning process of CBR, expounded themuffler experience cases39。基于CBR的排氣消聲器快速設(shè)計(jì)及評(píng)價(jià)方研究Research on CBRBased Rapid Design andEvaluation Method of Exhaust MufflerA Thesis Submitted to Chongqing Universityin Partial Fulfillment of the Requirement for theDegree of Master of EngineeringByXiang FeiSupervised by Prof. Deng ZhaoxiangMajor: Vehicle EngineeringCollege of Mechanical Engineering Chongqing University,Chongqing, ChinaMay2011I摘 要汽車排氣消聲器是多學(xué)科知識(shí)的有機(jī)結(jié)合體，各評(píng)價(jià)指標(biāo)之間并不獨(dú)立，文中建立了排氣消聲器綜合性能評(píng)價(jià)體系，并結(jié)合領(lǐng)域?qū)＜抑R(shí)，實(shí)現(xiàn)了多指標(biāo)的綜合定量評(píng)價(jià)，避免了采用單一指標(biāo)進(jìn)行逐一評(píng)價(jià)過程中產(chǎn)生的顧此失彼；排氣消聲器設(shè)計(jì)是弱理論強(qiáng)經(jīng)驗(yàn)的設(shè)計(jì)過程，一個(gè)成熟的實(shí)例融合了大量的專家經(jīng)驗(yàn)知識(shí)，基于實(shí)例的選型設(shè)計(jì)能夠快速的匹配出與設(shè)計(jì)目標(biāo)最相近的實(shí)例，不但取代了消聲器原始設(shè)計(jì)方法中的概念設(shè)計(jì)，縮短了開發(fā)時(shí)間，還最大限度保留了專家設(shè)計(jì)經(jīng)驗(yàn)知識(shí)，彌補(bǔ)了初級(jí)設(shè)計(jì)人員的經(jīng)驗(yàn)不足。 knowledge representation method based on the framework,and established the instance database by existing cases，the optimal case search by thequalification of dimensions and performance has been carried out by the fuzzy analogypreferred ratio and the prehensive performance evaluation system. In this paper, theconcept of instance data integrity has been putted forward, and regulated that dataintegrity, data similarity and priorities should be taken into account when making theoptimal choice. The case Revise has been implemented based on Rulebased reasoning(RBR) and Human Computer Interaction (HIC)。據(jù)有關(guān)統(tǒng)計(jì)顯示，在絕大多數(shù)機(jī)械產(chǎn)品開發(fā)中，40%是對(duì)過去的零部件產(chǎn)品進(jìn)行重用，40%只是根據(jù)具體目標(biāo)要求對(duì)現(xiàn)有零部件產(chǎn)品稍做修改，而全新的產(chǎn)品正向設(shè)計(jì)僅占 20%，由此可以看出以往成熟的產(chǎn)品在新產(chǎn)品開發(fā)過程中的扮演著十分重要的角色[5][6]。基于實(shí)例的推理是人工智能中新崛起的一項(xiàng)重要推理方法，其核心思想是在進(jìn)行問題求解時(shí)直接利用以往的成功經(jīng)驗(yàn)[8]。1922 年，美國(guó)專家 Stewart 率先用聲濾波器理論指導(dǎo)抗性消聲器的設(shè)計(jì)，拉開了消聲器設(shè)計(jì)理論研究的序幕[11]。在設(shè)計(jì)經(jīng)驗(yàn)總結(jié)方面，1973 年，日本的福田基一推出的排氣消聲器容積計(jì)算的統(tǒng)計(jì)關(guān)系[9]；英國(guó)的 和美國(guó)的 Dean 經(jīng)過對(duì)當(dāng)時(shí)大量數(shù)據(jù)的總結(jié)，得出了對(duì)排氣消聲器容積的經(jīng)驗(yàn)估算公式。CBR 是人類三種思維（直覺、邏輯、創(chuàng)造性思維）的一種綜合表現(xiàn)形式，適用于求解理論抽象較弱而經(jīng)驗(yàn)性因素較強(qiáng)的設(shè)計(jì)領(lǐng)域。然而就 CBR 技術(shù)的相關(guān)理論和應(yīng)用研究仍在繼續(xù)，主要以美國(guó)、德國(guó)、日本為主[40][41]。目前國(guó)內(nèi) CBR 技術(shù)在工業(yè)領(lǐng)域的應(yīng)用多集中在故障診斷專家系統(tǒng)中，而應(yīng)用到排氣消聲器設(shè)計(jì)中，目前國(guó)內(nèi)外還鮮有報(bào)道。2009 年，夏珩等人提出了一種多工況下綜合考慮排氣消聲器插入損失、被壓損失和尾管噪聲線性度的排氣消聲器綜合性能評(píng)價(jià)函數(shù)，引入了對(duì)排氣消聲器聲品質(zhì)的評(píng)價(jià)[55]。7Equation Section (Next)2 排氣消聲器性能評(píng)價(jià)標(biāo)準(zhǔn)與設(shè)計(jì)基礎(chǔ)理論 排氣消聲器性能評(píng)價(jià)指標(biāo)目前，排氣消聲器常用的性能評(píng)價(jià)指標(biāo)主要包含三個(gè)方面：聲學(xué)性能評(píng)價(jià)指標(biāo)、空氣動(dòng)力學(xué)性能指標(biāo)和結(jié)構(gòu)性能指標(biāo)。一般地，空氣中聲速隨溫度變化的近似計(jì)算公式為：8cRTcttp= =1. 4287(+)≈+()c 為聲速，溫度 t 的單位為℃。尖銳度反映了聲音的刺耳程度，體現(xiàn)了聲音信號(hào)中高頻成分的比重[59]；人耳往往對(duì)高頻噪聲較為敏感，信號(hào)尖銳度越大，聲音就越刺耳，尖銳度的單位是 acum，9定義中心頻率為 1kHz、帶寬為 160Hz 的 60dB 窄帶噪聲的尖銳度為 lacum。ex2Δ目前，對(duì)于 M1 類汽車，發(fā)動(dòng)機(jī)功率 ≥ 100kW時(shí)，要求功率損失比 ≤ 6%，排氣背壓差 ≤ 26kPa；發(fā)動(dòng)機(jī)功率 100kW時(shí)，要求功率損失比 ≤ 6%，排氣