Nanometer positioning of a dual-drive gantry table with precise yaw motion control

This article proposes a control strategy to position the stage of a dual-drive gantry table with nanometer precision. Furthermore, the yaw angle of the stage on which a platform is mounted is confined to an order of a micro-radian, even if the platform is rotating and/or sliding at the same time. Rather than adopting the traditional master-slave or cross-couple strategy, this research decoupled the control into translational and rotational control loops according to the system dynamics. In order to overcome the friction effect and achieve nanometer precision, a simplified pre-sliding dynamic model is included in the table's dynamic model for the fine tuning phase. Experimental results show the yaw angle of the proposed gantry stage is less than 0.6 arc-second during motion and less than 0.01 arc-second at steady state. The in-position vibration is bounded within ±4 nm when the platform is still, which is at the same level of the background noise produced by the air bearing of the platform.