Dynamic Sensitivity Analysis of Series-Parallel Machine Tool

• Main Authors: Ting-chia Yan, 楊定家
• Other Authors: Ting-nung Shiau
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/01334057800598217353

碩士 === 國立中正大學 === 機械工程所 === 94 === A hybrid machine tool developed by the Industry Technology Research Institute (ITRI) in Taiwan is used to study the dynamic sensitivity of the 3-PRS series-parallel mechanism. In recent years, the development of machine tools trends toward high accuracy. The accuracy of machine tools is affected greatly by structure vibration. In order to improve system characteristics, it is necessary to study the dynamic sensitivity of the mechanism. The design variables of the mechanism considered in this study include the radii of the base and moving platforms; lengths, densities and radii of the links; the stiffness of revolute and spherical joints. These parameters will greatly affect the dynamic characteristics of the mechanism. The Newtonian approach is employed to formulate the system equations of motion and the Runge-Kutta method is applied to simulate the dynamic responses of tool tip with the design variables. The relation between sliders’ locations and the tool tip profile is derived by the inverse kinematics. A linearization technique is applied to deal with the complex trigonometric differential equations. The dynamic sensitivity can be analyzed by solving the linearized system equations of motion, and the sensitivity of design parameters and different sliders’ location on the natural frequencies are discussed. Based on the numerical results, it can be found that the natural frequencies associated with the rotational displacements of the moving platform are affected by the radius of the moving platform. The natural frequencies associated with the degree of freedom of links are affected by the parameters of links or the stiffness of revolute joints. The highest natural frequency is only affected by the radius of the moving platform and stiffness of spherical joints. Besides, some system natural frequencies are not sensitive to sliders’ locations when the corresponding mode shapes in the rotational displacements of the moving platform are close to zero.