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Mathematical Problems in Engineering
Volume 2013, Article ID 287040, 5 pages
Research Article

Fractional Describing Function Analysis of PWPF Modulator

1Department of Control Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209, China
2EXQUISITUS, Centre for E-City, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798
3DSO National Laboratories, Singapore 117510

Received 9 November 2012; Accepted 8 January 2013

Academic Editor: Clara Ionescu

Copyright © 2013 Xinsheng Wang et al. 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.


Pulse-width pulse-frequency (PWPF) modulators are widely used in spacecraft thruster control. Their dynamic characteristic is still lack of effective analysis tools. This paper presents a fractional describing function method to describe the frequency characteristics of PWPF. A frequency-dependent gain and phase shift are clearly described by fractional-order expression, and the fractional-order behaviors depict the nonlinear properties of PWPF modulators. This fractional describing function method can also be applied to other kinds of modulators.