The Analysis and Synthesis of Spatial Mechanisms Using CAD System Based on Screw Geometry

• Main Authors: Fong-Zhi Chen, 陳峰志
• Other Authors: Prof. Ming-June Tsai
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/32218789658401406297

博士 === 國立成功大學 === 機械工程學系 === 88 === This study investigates the application of computer-aided design and drawing (CAD) system to the kinematic analysis and synthesis of spatial mechanisms. The geometrical analysis and synthesis implemented in a three-dimensional CAD system is studied based upon the geometric characteristics of screws. The advantages of the geometric method are straightforward, comprehensive, clearly represented, and easy to relate to a real mechanism. This study shows that similar to the graphical approach was used for the planar mechanisms, the geometrical approach in a CAD system used for the analysis and synthesis of spatial mechanisms is also an efficient method. The study first investigates the geometric operations depend on the geometric characteristics of the equivalent screw triangle. If the joint axes and auxiliary lines are regarded as individual parts, they can be assembled in the CAD system by giving the geometric constraints to meet the screw theory. Hence, the geometrical analysis and synthesis of spatial mechanisms is possible in 3-D CAD systems. The geometric approaches were applied to the synthesis of spatial function generation linkages in the study. In addition to the joint freedoms, the structure geometry, i.e. the constraint wrench, of mechanisms is also investigated. From the geometric characteristics of the screw system, the design criteria of the structural geometry of maglev system is developed. A new design is obtained using the geometry of screw system. Further, the Plucker coordinate, representation of lines, is used to formulate the ruled surface and to predict the molecular path for pumping speed performance evaluation of a molecular vacuum pump. A criterion is developed to analyze the flow rate of a new developed vacuum pump in transition regimes by using the DSMC(Direct Simulation Monte Carlo) method.