Author:
Guido Maione
Affiliation:
DEESD, Technical University of Bari, Italy
Keyword(s):
Non-integer-order operators, Fractional-order controllers, Rational approximation, Interlaced singularities.
Related
Ontology
Subjects/Areas/Topics:
Biomedical Engineering
;
Biomedical Signal Processing
;
Informatics in Control, Automation and Robotics
;
Signal Processing, Sensors, Systems Modeling and Control
;
Time and Frequency Response
;
Time-Frequency Analysis
Abstract:
Non-integer differential or integral operators can be used to realize fractional-order controllers, which provide better performance than conventional PID controllers, especially if controlled plants are of non-integer-order. In many cases, fractional-order controllers are more flexible than PID and ensure robustness for high gain variations. This paper compares three different approaches to approximate fractional-order differentiators or integrators. Each approximation realizes a rational transfer function characterized by a sequence of interlaced minimum-phase zeros and stable poles. The frequency-domain comparison shows that best approximations have nearly the same zero-pole locations, even if they are obtained starting from different points of view.