Precise Control of MIMO Motion Under the Torque Disturbances of the Gap Flow Field

The control of multiple-input–multiple-output (MIMO) motion under a mesoscale gap flow field has important applications. A wideband time-varying disturbance is caused on the control object due to the flow field; in particular, when the control object moves horizontally, the flow field is introduced relative to the centroid changes and torque disturbance. The torque disturbance and inter-axis coupling effect of MIMO control make achieving submicron level accuracy a significant challenge when using traditional control methods. This study adopts a MIMO system identification method based on closed-loop control to identify plants under the gap flow field and subsequently proposes a composite hierarchical disturbance rejection and decoupling control method. First, we combine the nominal control decoupling matrix and feedback compensation correction method to decouple the MIMO system. Second, we design a disturbance rejection control approach based on Disturbance Observer Control (DOBC) and H-infinity (H∞) control. Ultimately, the proposed method achieves submicron-level accuracy, comprising an important advance toward solving the control problem for semiconductor equipment.