ABSTRACT
This paper develops an automatic control switching mechanism for a long-stroke precision stage. The stage consists of a Piezoelectric Transducer (PZT) stage and a stepper-motor stage to achieve a large travel of 10 cm with a precision positioning of 1.2 nm. For the PZT stage, we obtained the model by experiments and applied robust loop-shaping techniques to design two controllers: one with fast responses and the other with smooth responses. Then we derived the corresponding robust PID controllers to simplify hardware implementation. The two controllers are switched to minimize the estimation error in the future horizon based on model prediction. For the motor stage, we derived its model by experiments and designed a gain-scheduling controller that allows the stage to move at its maximum speed for long travels until within the PZT moving range. The two stages are combined with a double-loop control structure to provide satisfactory responses. Lastly, the designed control mechanisms and structures are implemented for experimental verification. Based on the results, the proposed switching control mechani is deemed effective in improving precision positioning for long travels.
