Dual mode predictive control for ultrafast piezoelectric nanopositioning stages

Precision control of piezoelectric motor nanopositioning stages is widely used in a variety of nano-manufacturing equipments. But due to the hysteresis nonlinearity with input saturation, it is challenging to design an ultrafast output feedback controller with large region of closed-loop stability. To address this problem, we developed a dual-mode nonlinear model predictive control (NMPC) method, in which an optimal input profile found by solving an open-loop optimal control problem drives the nonlinear system state into the terminal invariant set; afterwards a linear output-feedback controller steers the state to the origin asymptotically. In contrast to the classical output-feedback controller, the settling time is effectively decreased and the closed-loop stable region is substantially increased by the present NMPC with almost no loss of the nanopositioning accuracy. Finally, the feasibility and superiority of the proposed switching control method are examined by extensive experiments on a Physik Instrumente P-563.3CL triple-axis nanopositioning stage.