Motion Control Of An H-drive Precision Stage Driven By Linear Motors

Motion control of precision stage is one of the crucial technologies for manufacturing equipment of integrated circuit, and it is characterized by high velocity, high acceleration and high performance. This dissertation addresses the motion control of an H-drive precision stage driven by three linear motors. A dynamic model is built up to study the system's input/output characteristics as well as the model variation while the slider's location on x axis changes. Decoupling control is realized by parameter-varying decoupling method for Y direction. Finally, a robust and optimized controller for both X&Y direction and also synchronous compensator forθdirection are proposed and designed considering following aspects: feedback control, feed-forward control, concurrent optimization of the both control.Dynamic model of the H-drive precision stage driven by linear motors is built up based on the hypothesis that the air-bearings are thought to be spring-damper systems. Characteristics of the input/output and quantitative analysis are given about stage's center of the mass (COG), payload ratio of the two linear motors in Y direction, and stage's rotational inertia as a function of x-slide position in long travel movement.Parameter-varying decoupling control strategy is applied to decouple the motion of the two parallel motors which aligns Y axis into simple Y axis motion and rotate motionθaround COG. In this way, H-drive's COG driving is achieved with X axis slider's random displacement. The means called relative gain array(RGA) is introduced to evaluate the decoupling validity and robustness with parameter errors is analyzed in simulating process.To handle two axis's long travel tracking control, single-input single-output (SISO) combined controllers are designed with feedback control, feed-forward control plus concurrent optimization of the above two. Hence, comprehensive analysis is presented about the relationship between time domain as well as frequency domain requirement and controller's design. Finally, the controller structure which comprises of phase lead-lag feedback control plus acceleration feed-forward control plus low-pass filter are proposed for the motion control of the H-drive precision stage.With actual experiments in single axis and comparison experiments between parameter-varying decoupling control and master-slave & position-force cross coupled control in Y direction, the integrated motion control experiments of the H-drive precision stage driven by three linear motors was realized by the parameter-varying decoupling control. The experimental results demonstrate that the combined motion controllers as well as parameter-varying decoupling control strategy can achieve high velocity, high acceleration and high performance motion for this kind of H-drive precision stage driven by three linear motors.