Reactive trajectory splitting function for machine tools with hierarchical drive structures

Abstract

One of the most important features of machine tools is its dynamics. Fast machines mean less time for the working process and lower running costs. However, a machine tool for working on large workpieces, has to be big, too. Because of the Newton's 2nd axiom ($\vec{F}=m\cdot \vec{a}$), heavy structures imply low accelerations to keep the driving force constant. This article refers to an approach using more drives than the applied degrees of freedom, which means redundancy. In this way, it is possible to build up hierarchical drive structures with different dynamics and specialized tasks. For example, small, lightweight 5DOF structures can be supported by additional large, heavy machine structures. Long travels are done by the large machine structure and high acceleration and jerk are provided by the small unit. A reactive algorithm has been developed to split a trajectory for a machine tool with hierarchical drive structures.