設計一組機構來完成工程上的需要稱為機構合成問題，在空間連桿機構合成問題領域中，剛體導引問題已經得到廣泛的研究與應用，但直線導引的機構合成問題，尚無人進行研究與探討。本論文針對直線導引的連桿機構合成問題進行研究，討論如何設計一組連桿機構，使其帶著一條無窮長的直線通過指定的位置，這可以應用在當欲導引的物件具有直線特性的時候，例如一把雷射槍。
直線的位移是屬於不完全指定位移理論的一部份，這個理論最早由Tsai 和 Roth所提出。該理論討論如何只考慮剛體上的某個幾何元素的位移，例如一個點、或是一條線，這個理論可以和空間機構合成問題結合。雙接頭連桿為最簡單的空間機構，本論文使用由螺旋理論推導出的螺旋三角形定理，此定理可以完美的描述各種雙接頭連桿的運動情形，並且具有物理意義。
本論文提出空間中直線導引問題和平面上路徑導引問題具有對應關係，空間上的圓柱對運動對應到平面上為旋轉對運動，平面四連桿路徑導引問題的空間一般化問題為4C機構直線導引問題。此外，本論文提出一個數值方法，來解決在求取數值解時可能得到不可行之四連桿的問題。
本研究發現空間中具四個自由度的雙圓柱對連桿，能夠導引任意直線至我們所指定的位置，且不具有空間限制，是非常適合用於直線導引問題的機構。本論文以雙圓柱對連桿為基礎，搭配各種常用接頭，合成空間四桿機構應用於直線導引問題。此外，為驗證合成方法和數值解的正確性，本研究使用電腦輔助繪圖軟體SolidWorks建立動畫模型進行證明。

This thesis investigates the dimensional synthesis of spatial four-bar linkages with cylindrical joints for line guidance problems. We are concerned with designing a four-bar linkage whose coupler can guide a line to pass through specified positions. We are also interested in finding the spatial generalization of the planar path generation problem.
In order to model the synthesis problem, we use the screw triangle geometry to model the incompletely-specified displacement of a line. We found that the cylindrical-cylindrical dyad has certain special beneficial features for the line guidance problem. For instance, its maximum number of allowable design positions is infinite. Therefore, this thesis demonstrates how to design spatial four-bar mechanisms with a CC dyad for line guidance problems, several numerical examples are provided, and the numerical results are also verified by using SolidWorks.
It is well-known that, in mechanism design, many planar problems are correspondent to spatial problems. This thesis shows that the well-known planar path generation problem is the degenerated case of the spatial line guidance problem. In the analogy, the planar four-bar mechanism is the degenerated case of the spatial 4C mechanism.

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