Tracking Control of a Galfenol-Actuated Nanopositioning Stage Using Feedforward Control with a Disturbance Observer

The main challenge of the galfenol actuator for high-precision positioning is the inherent nonsmooth hysteresis, which may lead to undesirable inaccuracies or oscillations and even instability. The primary aim of this study is to develop a tracking control method to precisely control the output displacement of a galfenol-actuated nanopositioning stage using feedforward control with a disturbance observer. In order to accurately describe the rate-dependent hysteresis, considering the dynamic behavior of the power amplifier, a novel dynamic model is put forward. Then, a developed controller is designed. In this controller, a feedforward control is developed to compensate the rate-dependent hysteresis, and a disturbance observer is employed to restrain disturbances, high-order unmodeled dynamics, and hysteresis compensation error. The comparative experimental results show that the proposed control method can significantly improve the positioning accuracy and suppress disturbances. This research can be applied in various micro and nanopositioning and vibration control fields.