Tracking Control for Piezoelectric Actuators with Advanced Feed-forward Compensation Combined with PI Control.

Piezoelectric actuators (PEA) are devices which can support large actuation forces compared to their small size and are widely used in high precision applications where micro- and nanopositioning is required. Nonetheless, these actuators have undeniable non-linearities were the well-known are creep, vibration dynamics and hysteresis. The latter mentioned is originated due to a combination of mechanical strain and electric field action; as a consequence, these can affect the PEA tracking performance and even reach instability. The scope of this paper is to reduce the hysteresis effect using and comparing different control strategies like feedback with feed-forward (FF) structure which is often used to compensate the non-linearities and diminish the errors due to uncertainties. In this research, black-box models were analysed; subsequently, a classic feedback control like proportional-integral (PI) was combined with the FF methods proposed separately and embedded into a dSpace platform to perform real-time experiments. Results were analysed in-depth in terms of the error, the control signal and the integral of the absolute error (IAE). It was found that with the proposed methods, the hysteresis effect could be diminished to acceptable ranges for high-precision tracking with a satisfactory control signal.