| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 96 === This thesis deals with the structural analysis and optimal dimensional synthesis of bicycle frame folding mechanisms. By searching the corresponding United States and domestic patent databases, eighty-three such mechanisms are identified and classified according to the normal direction of the folding plane and the number of folds. Among them, the kinematic structure of eleven designs which possessed similar motion characteristics are analyzed for further understanding the type of the mechanism used and the corresponding folding method. The pros and cons of each selected mechanisms are also investigated and discussed. Accordingly, the Watt’s type Ⅱ six-bar linkage is found to be superior to other types of linkages and therefore it is chosen for the study of dimensional synthesis. A sequential design process for computing the values of the dependent design variables of this type of linkage is developed based on the methods of two-point motion and path generation and the corresponding vector loop closure constraints. In addition, genetic algorithm based optimization technique is employed for synthesizing the optimal dimensions of the mechanism such that it would not only give the minimum storage space but would also have the maximum mechanical advantage at the initial folding state. Based on the synthesized results, an acrylic prototype of the mechanism is produced to verify the proposed methods.
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