Precision positioning control of a long-stroke stage employing multiple switching control

This paper proposes a multiple switching control method for a long-stroke precision stage to improve its performance. The stage consists of a motor stage with a travel of 10 cm and a piezoelectric transducer (PZT) stage with a resolution of 1 nm, which allows a simultaneously large travel length and precision positioning. The developed switching algorithms can select the optimal control sequence that minimizes the system cost by predicting of the future responses. We obtain the stage models through experiments. For the PZT stage, we design two robust loop-shaping controllers: the fast controller provides rapid transient responses and the smooth controller give smooth responses. We then derive corresponding robust proportional–integral-derivative controllers and develop a control switching mechanism that can simultaneously accomplish fast and smooth responses. The switching mechanism predicts future system responses by all possible control sequences and selects the optimal one to minimize specified costs. For the motor stage, we apply gain scheduling control, where the gain adjustment is larger than previously because the PZT stage can quickly compensate for the position errors of the combined stage. The designed control structures are then implemented for simulation and experimental verification. The results indicate that the proposed control is effective in improving system responses.