Redistributing Controller Orders to Increase Positioning Bandwidth in Nanopositioners

Integer-order damping and tracking controllers are typically used in tandem to overcome resonance and hysteresis induced positioning errors in piezo-actuated nanopositioners. This paper takes a novel approach of strategically redistributing the controller orders to achieve significant positioning bandwidth improvement, without any significant increase in the design complexity. The Positive Position Feedback (PPF) controller combined with a suitably gained Integral tracking controller is used as a candidate to demonstrate the efficacy of the proposed technique. The resulting fractional-order PPF damping and Integral tracking controllers result in increasing the overall positioning bandwidth of the closed-loop system by 37%; and subsequent improvement in positioning accuracy while tracking high-frequency triangular trajectories.