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Journal of Control Science and Engineering
Volume 2013, Article ID 947428, 10 pages
Research Article

Fractional-Order Control of a Micrometric Linear Axis

DIME, Department of Mechanical, Energetic, Management and Transport Engineering, University of Genova, via Opera Pia 15A, 16145 Genova, Italy

Received 13 December 2012; Accepted 18 February 2013

Academic Editor: Mohamed Zribi

Copyright © 2013 Luca Bruzzone and Pietro Fanghella. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper discusses the application of a particular fractional-order control scheme, the PDD1/2, to the position control of a micrometric linear axis. The PDD1/2 scheme derives from the classical PD scheme with the introduction of the half-derivative term. The PD and PDD1/2 schemes are compared by adopting a nondimensional approach for the sake of generality. The linear model of the closed-loop system is discussed by analysing the pole location in the σ-plane. Then, different combinations of the derivative and half-derivative terms, characterized by the same settling energy in the step response, are experimentally compared in the real mechatronic application, with nonnegligible friction effects and a position set point with trapezoidal speed law. The experimental results are coherent with the nonlinear model of the controlled system and confirm that the introduction of the half-derivative term is an interesting option for reducing the tracking error in the transient state.