Adaptive thrust allocation based synchronization control of a dual drive gantry stage

Abstract

In order to take full advantage of the hardware benefits by using redundant drive mechanisms, both synchronizing motions of the two actuators and avoiding excessive internal forces are vital to the smooth operations of dual drive gantry systems. However, almost all existing control schemes focus on pure motion synchronization only and the latter has been essentially ignored. Thus, even if the synchronization errors are kept within a small enough range, “pull and drag” phenomena could still exhibit due to the near-rigid physical coupling crossbeam and the consequent large internal forces. In this paper, a three-level synchronization control scheme based on adaptive thrust allocation is proposed to achieve not only better synchronized motion performance but also simultaneous regulation of internal forces. The overall control algorithm is composed of the motion tracking (Level I), the adjustable thrust allocation (Level II) and the on-line recursive least squares estimation (Level III), which is capable of achieving excellent internal force regulation and synchronization performance even when the distribution of system load cannot be priori known exactly in implementation or suffers from variations. Simulation and experimental results verify the effectiveness of the proposed synchronization control scheme based on adaptive thrust allocation in practical applications.