Quantifying the performance enhancement facilitated by fractional-order implementation of classical control strategies for nanopositioning

For most nanopositioning systems, maximizing positioning bandwidth to accurately track periodic and aperiodic reference signals is the primary performance goal. Closed -loop control schemes are employed to overcome the inherent performance limitations such as mechanical resonance, hysteresis and creep. Most reported control schemes are integer -order and combine both damping and tracking actions. In this work, fractional -order controllers from the positive position feedback family namely: the Fractional -Order Integral Resonant Control (FOIRC), the Fractional -Order Positive Position Feedback (FOPPF) controller, the Fractional -Order Positive Velocity and Position Feedback (FOPVPF) controller and the Fractional -Order Positive, Acceleration, Velocity and Position Feedback (FOPAVPF) controller are designed and analysed. Compared with their classical integerorder implementation, the fractional -order damping and tracking controllers furnish additional design (tuning) parameters, facilitating superior closed -loop bandwidth and tracking accuracy. Detailed simulated experiments are performed on recorded frequency -response data to validate the efficacy, stability and robustness of the proposed control schemes. The results show that the fractional -order versions deliver the best overall performance.