臺灣博碩士論文加值系統

本論文提出使用於引擎排氣系統的主動式消音器設計與控制方法。使用SYSNOISE的邊界元素法以預測各種主動式消音器的減噪性能特性。
根據這些性能預測，本論文使用傾斜45度角的單一揚聲器之主動式消音器結構並測試其主動式噪音控制(ANC)效果。迴授式ANC各自使用the filtered-x least mean square (FXLMS)與Godard modified algorithm兩種控制器調整演算法則應用於引擎排氣噪音的消除。
實驗結果顯示使用FXLMS演算法則的迴授式ANC系統能減少單頻噪音平均約23.6dB與汽機車引擎排氣噪音減噪超過6dB。實驗同時顯示使用Godard修正演算法則的迴授式ANC比使用FXLMS演算法則的迴授式ANC系統對於單頻減噪的暫態響應的收斂速度較為快速，但使用於固定轉速與加速過程的引擎排氣噪音消減時略遜於使用FXLMS演算法則的迴授式ANC系統的減噪效果(約只有5dB的減噪效果)。

This thesis presents design and control of active mufflers used in engine exhaust systems. Boundary element method in SYSNOISE is employed to investigate noise attenuation performances of various active muffler structures. Based on these performance evaluations, an active muffler having only one loudspeaker inclined at 45 degree with the muffler centerline is constructed and tested for active noise control (ANC). The feedback ANC with two controller tuning algorithms, the filtered-x least mean square (FXLMS) algorithm and Godard modified algorithm is applied independently for engine exhaust noise attenuation. Experimental investigation reveals that feedback ANC with FXLMS algorithm can attain an averaged 23.6 dB noise attenuation for pure tone excitation and over 6 dB noise reduction for motorcycle and automobile exhaust noises. It is also shown that feedback ANC with Godard modified algorithm has faster transient response compared to FXLMS algorithm for a pure tone noise, but has inferior noise attenuation capability than the FXLMS algorithm for the engine exhaust noise at fixed speeds (about 5 dB noise reduction) as well as during run-up tests.

摘 要 I
ABSTRACT II
目 錄 III
圖(表)錄 VI
符號說明 XI
第一章 緒論 1
1.1 前言 1
1.2 基本聲學簡介 2
1.2.1 聲速 4
1.2.2 聲音強度 6
1.2.3 聲壓位準與聲功率位準 6
1.2.4 響度(loudness) 7
1.3 研究動機 8
1.4 相關文獻回顧 11
1.5 研究方法 13
第二章 噪音工程與頻譜分析 15
2.1 噪音的定義 15
2.2 人類聽覺系統 16
2.3 噪音控制與防制 19
2.3.1 被動式噪音控制簡介 20
2.3.2 主動式噪音控制簡介 21
2.4 聲響頻譜分析 25
第三章 電腦輔助聲場分析 28
3.1 數值分析 28
3.1.1 有限元素法簡介 28
3.1.2 邊界元素法簡介 29
3.1.3 有限元素法與邊界元素法比較 32
3.2 I-DEAS 模型建立 34
3.3 LMS SYSNOISE分析 37
第四章 控制理論與控制器設計 41
4-1 適應性控制理論 41
4.2 主動式噪音控制系統 43
4.3 數位濾波器 45
4.4 LMS 演算法則 50
4.5 FILTERED-X 演算法則 55
4.6 修正的GODARD演算法則 57
4.7 PDC控制法則 59
第五章 實驗設備 61
5.1 實驗設備簡介 61
5.2 實驗設備 64
5.2.1控制器結構 64
5.2.2 控制器 65
5.2.3 波形產生器 65
5.2.4 伺服放大器 66
5.2.5 揚聲器 67
5.2.6 數位-類比轉換卡 67
5.2.7 噪音計 68
5.2.8 濾波器 69
5.2.9 頻譜分析儀 70
第六章 實驗結果 72
6.1 系統鑑別 72
6.2 單頻控制結果 74
6.3 汽機車噪音控制結果 82
6.4 暫態響應的改善 85
第七章 結論與展望 100
參考文獻 101

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