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Math. Comput. Appl. 2018, 23(2), 23; https://doi.org/10.3390/mca23020023

A Simple Spectral Observer

1
Cátedras CONACYT, Instituto de Ingeniería, Universidad Nacional Autónoma de México, 04510 Ciudad de México, México
2
Departamento de Ciencias de la Informática y Electrónica, Universidad de la Costa, Barranquilla, Colombia
3
Cátedras CONACYT, Centro Nacional de Investigación y Desarrollo Tecnológico, Tecnológico Nacional de México, 62490 Cuernavaca, México
4
Facultad de Ingeniería, Universidad Nacional Autónoma de México, 04510 Ciudad de México, México
*
Author to whom correspondence should be addressed.
Received: 3 March 2018 / Revised: 9 April 2018 / Accepted: 10 April 2018 / Published: 1 May 2018
(This article belongs to the Special Issue Optimization in Control Applications)
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Abstract

The principal aim of a spectral observer is twofold: the reconstruction of a signal of time via state estimation and the decomposition of such a signal into the frequencies that make it up. A spectral observer can be catalogued as an online algorithm for time-frequency analysis because is a method that can compute on the fly the Fourier Transform (FT) of a signal, without having the entire signal available from the start. In this regard, this paper presents a novel spectral observer with an adjustable constant gain for reconstructing a given signal by means of the recursive identification of the coefficients of a Fourier series. The reconstruction or estimation of a signal in the context of this work means to find the coefficients of a linear combination of sines a cosines that fits a signal such that it can be reproduced. The design procedure of the spectral observer is presented along with the following applications: (1) the reconstruction of a simple periodical signal, (2) the approximation of both a square and a triangular signal, (3) the edge detection in signals by using the Fourier coefficients, (4) the fitting of the historical Bitcoin market data from 1 December 2014 to 8 January 2018 and (5) the estimation of a input force acting upon a Duffing oscillator. To round out this paper, we present a detailed discussion about the results of the applications as well as a comparative analysis of the proposed spectral observer vis-à-vis the Short Time Fourier Transform (STFT), which is a well-known method for time-frequency analysis. View Full-Text
Keywords: signal processing; Fourier series; state observer; Short Time Fourier Transform; time-frequency analysis signal processing; Fourier series; state observer; Short Time Fourier Transform; time-frequency analysis
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Torres, L.; Jiménez-Cabas, J.; Gómez-Aguilar, J.F.; Pérez-Alcazar, P. A Simple Spectral Observer. Math. Comput. Appl. 2018, 23, 23.

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