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Publicações

Publicações por CRAS

1993

Blackboard approach to the mission management for autonomous underwater vehicle

Autores
Silva, EAP; Pereira, FL; Borges de Sousa, J;

Publicação
Applications of Artificial Intelligence in Engineering

Abstract
In this paper we propose a blackboard approach to the coordination stage of a practical Mission Management System which is composed of three hierarchic levels: The organization level takes place off-line and produces a coherent set of subplanes permitting to achieve the mission goals in a desirable fashion. The resulting plan will be considered as a reference basis for future actions once the mission has started. As the mission develops, a blackboard based coordinating structure (in the intermediate hierarchic level) will adopt the adequate mission achievement and safety oriented behaviors as a response to continuously monitored mission state and detected internal and external events. The lowest level of the hierarchy consists in the execution units which perform the required behaviors.

1990

Time-Varying Spectral Estimation Using the Instantaneous Power Spectrum (IPS)

Autores
Hippenstiel R.; De Oliveira P.;

Publicação
IEEE Transactions on Acoustics, Speech, and Signal Processing

Abstract
This paper examines a modified version of the instantaneous power spectrum (IPS). The short duration periodogram and the pseudo Wigner–Ville distribution (PWD) have been used extensively to display the time-varying spectral information. Disadvantages of the periodogram are its inherently poor resolution due to the requirement of matching the resolution width to the spectral dynamics of the signal. Potential problems associated with PWD are spectral cross terms and an inability to resolve spectral components at the endpoints of the analysis segment. A modified version of IPS is shown to be less sensitive to these types of problems. In addition, IPS can work with real valued signals sampled at the traditional Nyquist rate. © 1990 IEEE

1990

TIME-VARYING SPECTRAL ESTIMATION USING THE INSTANTANEOUS POWER SPECTRUM (IPS)

Autores
HIPPENSTIEL, RD; DEOLIVEIRA, PM;

Publicação
IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND SIGNAL PROCESSING

Abstract

1990

Automatic transfer function synthesis from a Bode plot

Autores
Lopes dos Santos, P; Martins de Carvalho, JL;

Publicação
Proceedings of the IEEE Conference on Decision and Control

Abstract
A novel algorithm that automatically identifies continuous-time transfer functions from Bode plots is presented. The identification is carried out in two stages. In the first one, the model order and 'good' guesses of the poles and zeros are obtained; in the second stage, estimates are refined by means of a modified Newton-Raphson algorithm. Because poles and zeros estimation only requires the magnitude curve, transport delays, if any, can be easily estimated by means of additional information supplied by the phase curve. The major and novel contribution of the proposed method resides in its first stage, where qualitative notions currently 'hidden' in the intuition of the designer are explicitly represented, yielding a simple optimization procedure that is not impaired by the presence of saddle points or local minima, and that converges very fast to the vicinity of the true solution. A detailed example is also provided to illustrate the value of the method.

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