由於振動會造成機器在運作時定位精度降低、零件磨耗甚至使得機器無法正常運作或損壞，因此在工程中如何抑制各種不同頻率的振動影響變成為一項重要的課題，其中可依使用的方式而分成被動式振動抑制及主動式振動抑制，由於兩種類型各有其優劣之處，因此結合兩者之長而發展出半主動式的振動抑制。半主動式振動抑制主要為透過變阻尼或變勁度來使系統達到振動抑制的效果，其中又以機械式變勁度此類型的表現最為突出，故於本論文中藉由機構的設計提出了旋轉法變勁度，並將其應用於振動系統中。
旋轉法變勁度的原理是將兩個相同的平面彈簧採左右對稱的方式裝配於上下兩剛體之間，下端點以旋轉接頭接於水平輸出桿上，利用垂直滑槽的垂直位移來調整平面彈簧的初始夾角，使得平面彈簧的上端點會以下端點為圓心旋轉，並搭配止動元件與平面彈簧的形狀，使得旋轉法變勁度機構同時具有撓性及剛性兩種特性。旋轉法變勁度機構處於撓性狀態時，變勁度範圍可達25.15 N/mm，同時當水平輸出桿位於初始位置時，調整勁度不須施加額外能量，且能以直線位移來調整平面彈簧旋轉角度，使勁度調整能更加線性。在透過探討平面彈簧與其他零件的給定參數對旋轉法變勁度機構特性之影響後，可設計出符合需求之變勁度機構，並將其應用於振動抑制，經由實驗可驗證當旋轉法變勁度機構作為吸振子系統時，能有效抑制輸入頻率為8至17 Hz之間且振幅為1 mm的振動。

This paper presents the design and experiment of a variable stiffness mechanism (VSM) for semi-active vibration systems. Compared with vibration isolators or absorbers with constant stiffness elements, the use of a variable stiffness element can adapt to the variation in disturbance frequency or load. The idea of the proposed VSM is to adjust the symmetric rotation of two parallel connected springs. The output force-to-displacement curve can exhibit zero to very large stiffness depending on the rotation amount of the springs. Infinite stiffness is further achieved by using mechanical stoppers to constrain the displacements of the springs. To further reduce the VSM size and complexity, specifically designed planar springs are proposed to replace commercially available coil springs. Force and stiffness analyses are presented to design a VSM with the largest stiffness variation. The effects of various parameters on the stiffness variation are discussed. Finally, a prototype and its associated experiments are presented to demonstrate the vibration absorption performance against various disturbance frequencies.

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