本文使用實體元素建立機車整車有限元素模型，用以分析機車振動狀態。模擬中最重要的因素為模型的準確性，為了證實模型的準確性，我們將機車車架有限元素模型做模態分析與實驗數據比較，實體元素所建構的機車車架模型，前三個模態結果的誤差分別為0.8%、1.7%、-2.5%，而樑與殼元素所建構的機車車架模型，前三個模態結果的誤差分別為-7.8%、4.6%、7.9%。因此我們可以了解到實體元素的模擬效果優於樑與殼元素。更重要的是實體元素的模擬非常接近實驗結果，顯示出機車車架使用實體元素模擬可以大幅提高模型的準確性。

使用實體元素所建構的機車車架模型為基底，建構機車整車模型以提高準確度。針對駐車怠速探討時，引擎為造成機車振動的原因，其可細分為三個振動來源，分別為兩個方向的搖撼力及一個方向的搖撼力矩。早期文獻在討論引擎運轉對於機車整車振動的影響皆只考慮兩個方向的搖撼力，而忽略搖撼力矩。因此我們將討論搖撼力矩對機車整車振動的影響。

應用傅立葉轉換，將複雜的搖撼力及搖撼力矩解析成多個頻率的簡諧力及力矩，並且將機車整車模型假設為線性系統，配合簡諧分析可以得到機車整車中手把、腳踏、坐墊及擋泥板這四個位置的位移頻譜響應圖，將不同頻率的簡諧力及力矩與頻譜響應圖搭配，可以得到這四個位置的位移，以位移代表其振動的程度，探討其振動情形，更可以得知搖撼力與搖撼力矩分別對這四個位置振動的影響，由結果顯示出搖撼力矩對機車整車振動的影響平均為30%，因此搖撼力矩對於機車整車振動的影響不可以忽略。

應用簡諧分析去討論有無直進桿的情況時對於機車振動的影響，並且得到整理出三個結果。第一，共振頻率對於分析振動很重要；第二，加速度與位移並非正相關關係；第三，相位角的不同影響振動的程度。

In this paper, we analyze the vibration situation of motorcycle and build the finite element model of the motorcycle by solid element. The most important factor is the accuracy of the model. We compare the modal analysis results of the chassis with the experiment data to prove the accuracy of the finite element model. The result shows that the error ratios of the first three mode of solid element are 0.8%, 1.7% and -2.5%, and beam and shell element are -7.8%, 4.6% and 7.9%. The solid element model is much better than beam and shell element model. More importantly, the result of solid element model is truly closed to the experiment data, and the research shows that chassis constructed by solid element promotes accuracy substantially.

We use this highly accurate model of chassis to build the more accurate model of motorcycle. In the parking and idle speed situation, the vibration source caused by the engine can be subdivided into three parts, two shaking forces and one shaking moment. The research in the past almost considered only two shaking forces, ignored the shaking moment, when discussing about the influence of motorcycle vibration caused by engine. In this paper, we discuss what the influence of motorcycle vibration is that caused by the shaking moment.

Applying the Fourier transform, we resolve the complex shaking force and moment into many harmonic forces and moments with different frequencies. Assuming the motorcycle model is a linear system, we can obtain the displacement frequency responses of four positions, the handle, the pedal, the seat and the fender, with the harmonic response analysis. We use the frequency responses and the harmonic forces and moments with different frequencies to obtain the displacement of four positions, and the displacement represents the index of vibration. Most important, we can observe the influence of vibration from the individual vibration source. The research shows that the average effect of the shaking moment is 30% on the influence of motorcycle vibration, so we cannot ignore the shaking moment in the research of motorcycle vibration.

We apply the harmonic response analysis to discuss about the influence of the motorcycle vibration in the situation of the motorcycle model with the rod or not, and then we generalize three results. First, the resonance frequency is important to analysis vibration. Second, the acceleration and displacement are not the positive relationship. Third, the influence of the motorcycle vibration is changed by the difference of phase angle.

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