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Research on CBR-Based Rapid Design and Evaluation Method of Exhaust Muffler

Author: XiangFei
Tutor: DengZhaoXiang
School: Chongqing University
Course: Vehicle Engineering
Keywords: Exhaust muffler Comprehensive evaluation Case-based reasoning Rapid design
CLC: U464.134.4
Type: Master's thesis
Year: 2011
Downloads: 107
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Abstract

Automobile exhaust muffler is the multidisciplinary combination with indispensible evaluation indexes. Based on expert knowledge, a comprehensive performance evaluation system of exhaust muffler has been established, the comprehensive quantitative evaluation of multi-index of exhaust muffler has been implemented, and the doubtfulness of comparing the cases respectively according to different indexes has been avoided. Exhaust muffler design is a typical design process with experience overweighs theory; a mature case included large quantities of expert experience knowledge. Based on mature cases, the most similar case can be identified very quickly with case-based reasoning(CBR), which not only replaced conceptual design of the traditional method, but also retained expert experience knowledge as much as possible, it shortened the development time, and maked up for the lack of experience of Junior designer.The evaluation indexes which associate with all of the performance requirements of exhaust muffler has been described in detail in this paper, and the quantitative evaluation method of exhaust muffler also has been analysised in the aspects of transmission loss, insert loss and pressure loss, then, a quantifiable comprehensive performance evaluation system of exhaust muffler has been established.It divided the transmission loss curves by frequency band and by attenuation ability and achieved the self-evaluation of transmission loss front the points of average sound attenuation, low transmission loss, intensity transmission loss and so on. The sound attenuation target curve has been obtained through the order frequency analysis on the exhaust noise and the goal curve of the tail pipe noise in each rotating speed, the transmission loss matching evaluation was carried out by comparing the transmission loss curve with sound attenuation target curve. The insert loss evaluation has been relized from the study of insert loss value and the reaching standard ability of the tail pipe noise in each rotating speed. The aerodynamics evaluation indicators of exhaust muffler included the pressure loss of rated condition and unit mass flow.the evaluation system considered the influence of volume, quality and connecting pipe cross-sectional area and also the requirement of process cost. The weights of evaluation system obtained by AHP, finally, the operability and feasibility of evaluation system has been verified through an example, thus to provide foundation for exhaust muffler comprehensive performance evaluation and matching design.This paper demonstrated that applying CBR for muffler design is feasible by comparing and analyzing the characteristics between exhaust muffler design process and case-based reasoning (CBR) process, proposed based on CBR exhaust muffler rapid design ideas and processes according to the reasoning process of CBR, expounded the muffler experience cases’ knowledge representation method based on the framework, and established the instance database by existing cases,the optimal case search by the qualification of dimensions and performance has been carried out by the fuzzy analogy preferred ratio and the comprehensive performance evaluation system. In this paper, the concept of instance data integrity has been putted forward, and regulated that data integrity, data similarity and priorities should be taken into account when making the optimal choice. The case Revise has been implemented based on Rule-based reasoning (RBR) and Human Computer Interaction (HIC); Incremental case saving is employed to save cases and HIC to maintain the database.Finally, based on CBR rapid design system of exhaust muffler has been implemented by Visual Basic.NET and joint programming with MATLAB, completed the selection of exhaust muffler design with the assistance of the system, the maneuverability and practicability of selection system has been validated.

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