Kinetostatic Analysis and Design Optimization of the Tricept Machine Tool Family

Abstract

Selecting a mechanism for a machine tool that will best suit the needs of a forecast set of rigidities can be a difficult and costly exercise. This problem can now be addressed using a kinetostatic modeling method. In this paper, a kinetostatic model for the Tricept machine tool family is established based on lumped flexibilities. This model can be used to analyze the effect of link flexibility on the machine tool’s global stiffness and the platform positioning precision. The Tricept machine tool is a new type of parallel mechanism with prismatic actuators whose degree of freedom is dependent on a passive constraining leg connecting the base and the platform. The geometric model and the mechanical design of the Tricept machine tool is first recalled. Then, a lumped kinetostatic model is proposed in order to account for joint and link compliances. It is shown that the link flexibility has a significant effect on the machine tool’s precision and that it is necessary to take the link flexibility into account. Additionally, the inverse kinematics and velocity equations are given for both rigid-link and flexible-link mechanisms. Finally, the optimization of the stiffness is addressed using a genetic algorithm.