Evaluation of Control Algorithms for High-Speed Motion Control of Machine-Tool Structures Based on Stewart Platforms

Abstract

The control of high-speed motion of a machine tool structure based on the parallel link Stewart platform kinematic structure is addressed here. A model- based decoupling and linearizing algorithm is used in Cartesian space, measurements in this space being derived in real time from joint space measurements by an approximate solution of the forward kinematic relationships. A cross-coupled control formulation is then used to transform the control problem to decoupled control in task space coordinates. Control approaches are then applied to direct the control effort primarily at reduction of task space errors critical for machining tasks. The control algorithms developed thus are applied to a computer simulation of the dynamic response of a Stewart platform based machine tool structure as it executes a number of representative trajectories at feed rates of up to 12 m/min. The simulation results demonstrate the effectiveness of the proposed control algorithms and are presented here.