Title: Computation of frequency responses for uncertain fractional-order systems

Authors: Paluri S.V. Nataraj, Rambabu Kalla

Addresses: Systems and Control Engineering Group, IIT Bombay, India. ' Systems and Control Engineering Group, IIT Bombay, India

Abstract: This paper proposes an algorithm for computation of Bode magnitude and phase responses for a large class of linear uncertain fractional-order systems using interval constraint propagation technique. It is first shown that the problem of finding the magnitude and phase of the uncertain fractional-order system over a frequency range can be formulated as a interval constraint satisfaction problem and then solved using branch and prune algorithm. The algorithm guarantees that the magnitude and phase responses are computed to prescribed accuracy. The other advantage of the method is that the magnitude and phase can be computed without any kind of integer-order approximation of the given fractional-order system. The proposed algorithm is demonstrated on three examples including a practical application of a gas turbine plant.

Keywords: constraint satisfaction problems; control system analysis; fractional-order systems; interval analysis; parameter uncertainty; reliable computation; robust control; frequency responses; Bode magnitude responses; phase responses; interval constraint propagation; gas turbines.

DOI: 10.1504/IJAAC.2010.030811

International Journal of Automation and Control, 2010 Vol.4 No.2, pp.201 - 217

Received: 04 Dec 2008
Accepted: 02 Apr 2009
Published online: 06 Jan 2010 *

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