【正文】 be used to model the structure and provide data to indicate what structural modifications may be made to improve the frequency response characteristics of the seat system. Modal analysis is much more plicated than resonant impact testing and is used only when structural modifications are needed, or FEA models need to be correlated.Modal analysis details the relative importance of various seat modes in the dynamic model most effectively. Impact analysis on Bucket Seat 4 revealed resonances at Hz, Hz, and Hz, but provided limited information to the importance of each resonance. The modal analysis of Bucket Seat 4 illustrated the importance of each mode. A lateral mode at Hz was % of the response, a fore/aft mode at Hz was % for the response, and lateral Hz was % of the response.While modal analysis provides detailed information about a seat’s frequency response characteristics, it generates this information by uniformly exciting the seat system with a broad band burst random signal. This is an excellent method for exciting all the modes in the seat, but is not representative of the input spectrum that a vehicle provides. It is important to have the main seat resonances at frequencies which the vehicle does not excite, so their impact can be minimized. Bucket Seat 4 had a main lateral mode at Hz and a minor lateral mode at Hz, but the simulation road load testing only excited the minor lateral resonance.Shaker table testing is tool used by the OEM’s and suppliers to subject specimens to squeak, rattle and durability testing. A seat may be subjected to thousands of simulated miles or used to input sine sweep inputs to assist in determining the source of each squeak and rattle issue. Unoccupied seat shake often causes squeak and rattle issues in the seating system. When the resonant frequency of a seat is below 16 Hz the probability of invehicle squeaks and rattles increases.The first method of testing was subjecting the seats to sinusoidal vertical, and longitudinal inputs. The inputs were similar to those used for current testing specifications. Acceleration input levels are very important when performing sine sweep tests. If the acceleration levels are too high it will not accurately represent acceleration levels similar to those seen on the road. Tables 6 through 8 detail the sine sweep testing. The vertical input to the shaker table was from 2 to 20 Hz. The data for each input was analyzed to determine correlation between vertical input and lateral output, vertical input and fore/aft output, lateral input and lateral output, fore/aft input and fore/aft output. Bucket seat 1,3 and 4 had similar resonant frequency characteristics in the fore/aft direction which was not revealed during the sine sweep testing. The resonant frequency was typically lower when analyzing the data from lateral input lateral output and fore/aft input and fore/aft output. During the sine sweep evaluation the start and stop frequency and acceleration amplitudes are recorded. These values are pared to the vehicle ASD plots.Table 6: Vertical Sine Sweep ResultsSample Lateral (Hz)Fore/Aft(Hz)Bucket seat 1Bucket seat 2Bucket seat 3Bucket seat 4Table 7: Lateral Sine Sweep ResultsSample Lateral (Hz)Fore/Aft(Hz)Bucket seat 1Bucket seat 2Bucket seat 3Bucket seat 4Table 8: Longitudinal Sine Sweep ResultsSample Lateral (Hz)Fore/Aft(Hz)Bucket seat 1Bucket seat 2Bucket seat 3Bucket seat 4The second method of testing was to subject the seats to time histories recorded at each vehicle proving grounds. The time histories were reproduced from 8 to 40 Hz using six degrees of freedom. When using the road simulation files seat dynamics can be reproduced as they would being in a vehicle. The seats can characterized to determine which areas of the seat may be an issue during squeak, rattle and durability testing. The data from road simulation testing was analyzed and pared to vertical, lateral and fore/aft inputs Bucket seats 1,2,3 and 4 had similar characteristics to the sine sweep results. Bucket seat 4 had a higher resonant frequency on the road simulation than during the sine sweep evaluation.SUMMARYAs the need for dynamic seat testing is increasing it is being increasingly necessary to municate the results of frequency testing accurately. Each of the testing methods discussed。 dynamic impact testing, modal analysis, sin sweep shaker table evaluation, and road data replication on the shaker table provide different information about the seating system being tested. It is necessary to understand the merits, as well as the limits, of each method when paring data between methods. This paper has shown that determining an accurate frequency response model requires the synthesis of data from each of the testing methods to understand and optimize the characteristics of a seating system.附 錄 Ⅱ：中文翻譯座椅系統(tǒng)共振頻率的測試方法的比較座椅系統(tǒng)的發(fā)展如果沒有精確的動力學模型，那么它發(fā)出吱吱聲，座椅靠背產(chǎn)生過多的振動，和乘坐時疲勞等特征發(fā)生的可能性很高。如果這些問題在發(fā)展測試期間沒有得到解決，那么在產(chǎn)品生產(chǎn)出以后上述現(xiàn)象就會發(fā)生。工程學上的改變是很困難的，費用也很昂貴。由于現(xiàn)在的座椅系統(tǒng)是很復雜的，所以工程師們必須用現(xiàn)代技術(shù)來確定座椅系統(tǒng)響應特性。形式分析是一種正處于發(fā)展當中的動力學結(jié)構(gòu)模型或者機械系統(tǒng)，它是用來解決那些彈射、仿真、預測和最佳化問題的方法。動力學模型是一套由自然頻率、阻尼系數(shù)、樣式形式組成的形態(tài)參數(shù)。這些參數(shù)是建立在結(jié)構(gòu)和系統(tǒng)基礎之上的。根據(jù)實驗得到的形式分析可以作為時間基礎，和頻率范圍基礎測量法來計算形式參數(shù)。這個方法提供了最徹底的使座椅系統(tǒng)隔離的動態(tài)響應特性的解說。共振分析通常被用作確定座椅系統(tǒng)動態(tài)響應的近似值。這個方法提供了描述系統(tǒng)自然頻率的頻率回應響應函數(shù)。共振分析可以快速的提供信息，但是不能象形式分析那樣完全地說明動態(tài)響應特性。振動工作臺試驗是用來測定座椅系統(tǒng)共振頻率另一種方法。振動工作臺能夠掃描輸入正弦波然后任意輸入到座椅系統(tǒng)。正弦波的振幅隨意輸入能約束加速度或者轉(zhuǎn)移抑制?；旌掀髌脚_同樣有模擬路面情況的能力，這些路面在汽車上產(chǎn)生的負荷就像座椅。實驗室允許復制復雜的實驗樣本時間記錄?；旌掀髌脚_可以從六個自由度復制路面輸入，即位移、側(cè)面、偏移、傾斜、滾動、縱向。實驗分析關(guān)于通過共振分析、形式分析獲得座椅共振頻率數(shù)據(jù)對照的論文，振動平臺測試使用六自由度模擬再制造正弦波和模擬路面數(shù)據(jù)。所有的座椅都是由計算機設計位置并安置的，而且嚴格的加裝了用來測試的工作臺或者模板。形式分析形式分析是用來表現(xiàn)座椅動力性特色的方法，這是一個收集相關(guān)頻率的測量方法，得到準確的頻率回應響應函數(shù)來描述動態(tài)特性。人們通常習慣用頻率響應函數(shù)來計算座椅系統(tǒng)。座椅被安置了兩個電動機，一個安放在座椅靠背的側(cè)面，另一個安放在座椅靠背底部的前邊或后邊。響應發(fā)生在頻率范圍為0至50赫茲的光線之間。激勵信號是一個80%的脈沖任意函數(shù)。脈沖激勵整個頻率然后響應逐漸消失，最后計算結(jié)果。脈沖信號通過傅立葉變換分析，這是一個假想信號，因為它能確保信號從水平零點開始直到計算的最后。除了激勵方