On actuator reversal motions of machine tools

When joints in a machine tool reverse the direction of their motion, non-linearities that are ignored in machine design and control are reflected noticeably in the accuracy of machined surfaces. For example, friction characteristics of a machine tool become highly non-linear at low operating speeds, demanding sophisticated compensation. We present a theoretical treatment of the kinematics of reversals and reversal free paths of machine tools. We visualize and compare reversal characteristics of active joints in serial, parallel, and hybrid mechanisms for various trajectories and sweeping patterns. Reversal characteristics have implications both in the design of machine tools and in path planning.