Controller tuning for a linear feed dride using the high frequency system dynamics

Abstract

Modern machine tools require positioning systems with the ability to follow, with reduced errors, trajectories with high velocities and accelerations. Therefore, the controllers must achieve an appropriate bandwidth and robustness to reject external perturbations and the effects of non-modeled dynamics. This work presents the high frequency dynamics and a reduced model of a system composed by an electric motor, a ball screw, and linear bearing guides. Furthermore, the estimated parameters for the reduced model and the Coulomb friction are presented. Following, a control strategy is presented given by a state space controller, a Zero Phase Error Tracking Controller and a compensation for the Coulomb riction. The desired closed loop dynamics was selected by studying the stability of the system using the high frequency model. Finally, experimental results with low tracking error are shown. For point to point positioning at constant velocity it shows an average error of 41?m, and 38?m for a sine type trajectory. Both values are suitable for modern machine tools.