A hybrid control approach for precise positioning of a piezo-actuated stage

Piezo-actuated stages are composed of a piezoelectric actuator (PEA) and a positioning mechanism. Hysteresis behavior of PEAs limits the position accuracy of the piezo-actuated stages. This paper presents a hybrid control approach for precise positioning of a piezo-actuated stage, where Bouc-Wen hysteresis model is used to represent the hysteresis behavior of the PEA. A Luenberger observer-based feedforward controller is designed, and then integrated with a Particle Swarm Optimization (PSO)-based Proportional-Integral-Derivative (PID) controller to form a hybrid controller. Optimal PID gains are obtained based on a fitness function proposed to reduce the displacement error and achieve fast response time. The results show that using the proposed hybrid controller reduces the hysteresis effect significantly, and thus the maximum error is minimized to 0.127 μm, which is 0.17 % of the maximum displacement of 72.1 μm.