Design and control of air bearing precision positioning stage driven by linear motors

In order to master the design and control techniques of the workpiece table in photoetching machine, an H-type air bearing precise positioning stage driven by dual linear motors was established. Some key techniques, including design method of air bearing slider and synchronic-motion control of dual linear motors, were studied. Three air bearing sliders were analyzed and designed by finite element method. Preload technologies were adopted to improve air bearing's static performance. The experiment results show that the air-bearing sliders have high load capability and stiffness. The static stiffness of X-slider in the vertical direction is 276.9 N/μm and that of Y-slider is 333.3 N/μm. The dual linear motors of H-type stage require high-precision synchro-control. Traditional tandem and parallel synchronous control can't fulfill the demand. An improved parallel structure synchronous controller based on velocity synchro-error was proposed, which adaptively tuned the PID parameters by fuzzy controllers. The experiment results show that the synchronous velocity precision is improved more than three times by using the improved synchronous controller, which is suitable for multi-motor synchronization control with strong mechanical coupling. H-type air bearing positioning stage driven by linear motors has high load capability (40kg) and high accuracy (<2 μm) and suits to be used in precision engineering.