機械結構動態行為響應量測分析與診斷評估

Analysis and diagnosis on the dynamic behavior response of the mechanical structures

張哲綱(Che-Kang Chang)

指導教授 ： 林盛勇

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2008年)

https://doi.org/10.6827/NFU.2008.00026

摘要

本文針對產業界較常見之機械結構進行動態行為響應分析。由於馬達應用範圍相當廣泛，舉凡在加工、定位及動力傳達等場合，而車輛工業的發展也為目前國內重點發展產業之一，故本文選擇了馬達迴轉結構與車輛避震結構進行動態行為響應量測分析與診斷評估。
第一部份針對工業用伺服馬達以數值模擬分析及實驗量測分別進行結構模態求解與求得臨界轉速下所引發的動態響應頻率；實驗中使用頻譜分析儀及加速度規等儀器進行結構動態行為響應量測。動態行為響應分析的方法係利用馬達在加減速過程中所呈現之頻線瀑布圖(waterfall)。以往使用頻線瀑布圖測試方法時易受雜訊影響而降低臨界轉速對結構共振判別的準確性，本次實驗利用訊號單點接地技巧改善了雜訊所造成判別誤差的影響，同時將結構動態行為響應量測之數據搭配數值模態分析的結果進行結果比對並建立一共振頻率判讀流程，確切提高頻線瀑布圖於臨界轉速是否會造成結構共振判別之準確性。
第二部份係結合振動量測與頻譜訊號分析技術，進行車輛實際路況振動與位移量測，使用頻譜分析儀、加速度規及位移計等儀器從事車體、避震支撐架與輪軸架之振動量測，同時將擷取的資料進行動態行為響應分析。訊號分析技術針對振動量測訊號進行快速傅立葉轉換輸出，並以功率頻譜密度、反譜(cepstrum)及總量(overall)分析分別來呈現振動的特性。此舉改變以往在真實路況研究動態響應分析只探討路況對車體與避震器振動之能量效應，經由反譜確切找出車輛振動變動最大的頻率，藉以降低此頻率振動的能量及其所造成劇烈的動態響應，經改善後即可提升行車舒適性與安全性。

關鍵字

動態行為響應 ； 振動量測 ； 頻譜分析

並列摘要

The dynamic behaviors of the mechanical structures commonly utilized in industry are analyzed in this study. The application scope of a motor is widespread such as for the situations of material processing, positioning and power transmission. The development of vehicle engineering is one of the important focus industry policies in our country. Therefore, the rotary structure of the motor and the vehicle vibration absorber structure are selected as the objects for the dynamic behavior response measurement, analysis, diagnosis and assessment in this study.
The first part of this study is to determine the modal shape and to calculate the response frequency through the numerical simulation, under the excitation of critical rotational speed via the experimental measurement for a servomotor structure utilized in industry. Spectrum analyzer in conjunction with accelerometer is used to measure and analyze the response of the structure dynamic behavior in experiment. The analysis method for the response of the structure dynamic behavior is through the characteristics of the spectrum waterfall pattern which is exhibited during the acceleration/deceleration process of a motor. The test method of the spectrum waterfall pattern is easily influenced by the noise signal deduced from the environment and the judgment accuracy for structure resonance is reduced from the critical speed excitation as before. Single point grounded skill is utilized to improve the judgment accuracy in this study. A comparison between the data collected from the structure dynamic behavior response measurement and the result obtained from the modal analysis. Their combination is further utilized to establish a procedure for structure resonance judgment. As a result, the accuracy for structure resonance judgment from the spectrum waterfall pattern excited by the critical speed of a rotary structure may be increased exactly.
The second part of this study is to monitor the vibration and displacement response when a car travel on a real road condition through the combination of vibration measurement and spectrum signal analysis scheme. Spectrum analyzer, accelerometer and displacement transducer are first used to detect the vibration of a vehicle body, absorber system frame and rigid axle. The on-line signals acquired are then processed for the dynamic behavior response analysis through the Fast Fourier Transform with Power Spectrum Density and Cepstrum, and Overall analysis method exhibiting the characteristics of the vibration signals. The lack of power spectrum density analysis usually performed in vehicle body and absorber system as before is supplementary by this complete analysis. The maximum frequency of the vehicle vibration variation may exactly be determined through this cepstrum analysis. As a result, the vibration energy under this maximum frequency and its violent dynamic response may be effectively reduced. The comfortable and safe performances may be promoted when a car travel on a road based on this improvement proposed.

並列關鍵字

dynamic behavior response ； vibration measurement ； spectrum analysis

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