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American control Conference (ACC)

作者： P. Akella J.T. Wen Control Laboratory for Mechanical Structures (CLaMS) Center for Advanced Technology in Automation Robotics & Manufacturing Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY USA

The passivity property of dissipative mechanical structures has long been exploited in designing passive controllers that provide robust stability even in the presence of unmodeled dynamics of the system. For an input/output map of a flexible structure to be passive, collocation of the actuators and sensors is required and also the sensors should measure the velocity of the system. The so-called smart structures frequently have more sensors than actuators. Therefore, the passive controller can at best utilize only a subset of the sensors. In this paper we consider the design of a squaring down matrix which would render a system passive subject to some additional performance considerations. The problem of obtaining the synthesized passive output is cast as a set of linear matrix inequalities (LMIs) which can be efficiently solved by the LMI Toolbox in Matlab. We apply this procedure with the assumption that the sensors provide both displacement and velocity information which is generally not true. We show that the passive controllers can be implemented without the use of velocity information. By using synthesized passive outputs in addition to naturally occurring passive outputs, we obtain better system performance. We present experimental results involving a single flexible beam with torque input and hub angular position and strain gage outputs.

关键词： Feedback control Intelligent sensors control system synthesis Mechanical sensors Sensor systems Linear matrix inequalities Mechanical factors control systems Robust stability Flexible structures

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Non-Wiener effects in LMS-implemented adaptive equalizers

Non-Wiener effects in LMS-implemented adaptive equalizers

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： M. Reuter J. Zeidler Department of Electrical and Computer Engineering University of California San Diego CA USA Control and Ocean Surveillance Center RDT&E Division Naval Command San Diego CA USA

An adaptive transversal equalizer based upon the least-mean-square (LMS) algorithm, operating in an environment with temporally correlated interference can exhibit better steady-state mean-square-error (MSE) performance than the corresponding Wiener filter. This phenomenon is a result of the nonlinear nature of the LMS algorithm and is obscured by traditional analysis approaches that utilize the independence assumption. We use a transfer function approach to quantify the MSE performance of the LMS algorithm and demonstrate that the degree to which LMS may outperform the corresponding Wiener filter is dependent on system parameters such as signal-to-noise ratio and the step-size parameter.

关键词： Adaptive equalizers Least squares approximation Wiener filter Adaptive filters Interference Steady-state Transfer functions Noise cancellation Oceans Surveillance

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Global asymptotic stabilization of the ball-and-beam system

Global asymptotic stabilization of the ball-and-beam system

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IEEE Conference on Decision and control

作者： C. Barbu R. Sepulchre Wei Lin P.V. Kokotovic Department of Electrical and Computer Engineering University of California Santa Barbara CA USA Center for Systems Engineering and Applied Mechanics Universite Catholique de Louvain Louvain-la-Neuve Belgium Department of Systems Control and Industrial Engineering Case Western Reserve University Cleveland OH USA

For the well known ball-and-beam system, we design a new saturation control law, which employs state-dependent saturation levels and guarantees global asymptotic stability, not achieved with previous designs.

关键词： control systems Stability Force control Force feedback Friction Nonlinear control systems control nonlinearities Angular velocity Nonlinear equations Acceleration

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Probability of error evaluation for multichannel reception of coherent MPSK over Ricean fading channels

Probability of error evaluation for multichannel reception o...

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IEEE International Conference on Communications (ICC)

作者： T.L. Staley R.C. North W.H. Ku J.R. Zeidler Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA RDT&E Division (NRaD) Naval Command Control and Ocean Surveillance Center San Diego CA USA

This paper presents a recursive method for evaluating the error rate performance of multichannel reception of coherent MPSK systems operating over slowly Ricean fading channels. Each of the multiple channels is assumed to be a bandlimited two-sided discrete path model with complex Gaussian taps. The main path is assumed to be non-zero mean, corresponding to Ricean fading. Maximal ratio combining in the receiver is assumed, and an expression for the received phase density function is developed. A recursive method for solving the resulting error probability expression is then presented. This method is similar to those used for recursive computation of the Marcum Q function, and is both efficient and accurate. The method can be applied for both the flat and frequency selective Ricean fading cases. Examples based on a ship to ship high-data-rate line-of-sight channel model are provided to demonstrate the method.

关键词： Fading Statistics Bandwidth Band pass filters Receiving antennas Diversity reception Probability Error correction Gaussian channels Random variables

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Tracking controllers for systems linear in the unmeasured states

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AUTOMATICA 1996年第5期32卷 735-746页

作者： Freeman, RA Kokotovic, PV [a] Center for Control Engineering and Computation Department of Electrical and Computer Engineering University of California Santa Barbara CA 93106 U.S.A.

We introduce a class of extended strict feedback nonlinear systems in which unmeasured states enter the system equations in a linear (affine) fashion. For such systems, we present a procedure for constructing dynamic partial state feedback controllers that achieve the global asymptotic tracking of given reference trajectories while maintaining internal boundedness. The controller dynamic order is equal to the number of unmeasured states. To illustrate our design procedure, we construct such a tracking controller for a nonlinear electromechanical rotor/platform system. Copyright (C) 1996 Elsevier Science Ltd.

关键词： nonlinear systems global stability tracking disturbance rejection dynamic output feedback Lyapunov methods

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Design and implementation of fuzzy controllers for complex systems - case study: a water desalination plant

Design and implementation of fuzzy controllers for complex s...

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Proceedings of ISAI/IFIS Mexico-USA Collaboration in Intelligent Systems Technologies

作者： M. Jamshidi M.-R. Akbarzadeh K. Kumbla NASA Center for Autonomous Control Engineering (ACE) Electrical and Computer Engineering Building University of New Mexico Albuquerque NM USA

Two soft computing paradigms for automated learning control of complex systems are briefly de scribed. To illustrate the utility of the paradigms, they are applied to a desalination process and sim ulations are performed. The first paradigm in corporates Genetic Algorithms (GA) in a learn ing scheme to adapt parameters of the fuzzy controller to changing environmental conditions. The second paradigm concentrates on a methodology which uses a Neural Network (NN) to adapt a fuzzy logic controller. Simulation results of fuzzy controllers learned with the aid of these soft computing paradigms are presented.

关键词： Fuzzy control Fuzzy systems control systems computer aided software engineering Desalination Fuzzy logic Automatic control Neural networks Robust control Genetic algorithms

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On Genetic Programming of Fuzzy Rule-Based Systems for Intelligent control

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Intelligent Automation and Soft Computing 1996年第3期2卷 271-284页

作者： Tunstel, Edward Jamshidi, Mo NASA Center for Autonomous Control Engineering Department of Electrical and Computer Engineering University of New Mexico Albuquerque NM 87131 United States NASA/Jet Propulsion Laboratory Pasadena CA United States

Fuzzy logic and evolutionary computation have proven to be convenient tools for handling real-world uncertainty and designing control systems, respectively. An approach is presented that combines attributes of these paradigms for the purpose of developing intelligent control systems. The potential of the genetic programming paradigm (GP) for learning rules for use in fuzzy logic controllers (FLCs) is evaluated by focussing on the problem of discovering a controller for mobile robot path tracking. Performance results of incomplete rule-bases compare favorably to those of a complete FLC designed by the usual trial-and-error approach. A constrained syntactic representation supported by structure-preserving genetic operators is also introduced. © 1996 Taylor & Francis Group, LLC.

关键词： Fuzzy control Genetic programming Mobile robots Rule-base discovery Syntactic constraints

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Performance of coherent MPSK on frequency selective slowly fading channels

Performance of coherent MPSK on frequency selective slowly f...

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IEEE Conference on Vehicular Technology (VTC)

作者： T.L. Staley R.C. North W.H. Ku J.R. Zeidler Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA RDT&E Division Naval Command Control and Ocean Surveillance Center San Diego CA USA

This paper presents a framework for analyzing the error rate performance of multichannel coherent reception of MPSK systems operating over frequency selective, slowly fading channels. Each of the baseband channels is assumed to be a bandlimited two-sided discrete path model with correlated complex Gaussian taps, which is assumed to have resulted from an underlying Gaussian wide-sense-stationary uncorrelated-scattering (WSSUS) physical channel followed by a lowpass filter. By working with this "resolved channel", the resulting performance evaluation incorporates whatever resolution is inherent in the bandwidth of interest. An expression for the received phase density function is developed. The probability of symbol error, conditioned on the interfering symbols, is then determined, and the cases for which a closed form or efficient numerical evaluation is possible are specified. The symbol error rate is then obtained by summing over the interfering symbols. A progressive ISI bound is then discussed for cases when faster computation is required. Examples are then provided to demonstrate the versatility of the method.

关键词： Frequency Fading Error analysis Phase shift keying Bandwidth Pulse shaping methods Performance analysis Density functional theory Signal resolution Oceans

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Channel estimate-based performance prediction for coherent linear modulation on slowly fading channels

Channel estimate-based performance prediction for coherent l...

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MILCOM, Military Communications Conference

作者： T.L. Staley R.C. North R.A. Axford W.H. Ku J.R. Zeidler Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA RDT&E Division NRaD Naval Command Control and Ocean Surveillance Center San Diego CA USA

This paper describes a framework for predicting the error rate performance of linearly modulated coherent systems operating over frequency selective, slowly fading channels, when the statistics of the bandlimited two-sided discrete FIR model for the channel are available from a channel estimator. This work supports an upcoming experiment in which channel estimates obtained with one modulation scheme will be used to predict the performance of higher order modulation schemes. The focus of this paper is the mathematical framework for the theoretical performance prediction. Linear memoryless modulation is assumed, providing a a very general signal model that includes M-PSK and M-QAM. The channel model is slowly fading, with correlated complex Gaussian taps, incorporating both the flat and frequency selective cases. Expressions for the error probability are presented, and the cases for which closed form or acceptable numerical solutions exist are delineated. A new recursive method for solving the Rician-fading main path case is presented. The high-data-rate maritime line-of-sight channel is used to demonstrate the use fullness of the method.

关键词： Fading Chirp modulation Error analysis Rayleigh channels Frequency estimation Pulse shaping methods Higher order statistics Amplitude modulation Quadrature amplitude modulation Pulse modulation

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Phase correction for coherent noise reduction in short-range radar measurements

Phase correction for coherent noise reduction in short-range...

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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： S.G. Beaven S.P. Gogineni P. Kanagaratnam Development Test & Evaluation Division Naval Command Control and Ocean Surveillance Center San Diego CA USA Radar Systems and Remote Sensing Laboratory Department of Electrical and Computer Engineering University of Kansas Lawrence KS USA

Short-range scatterometer systems are used to obtain radar backscatter signatures for understanding the interaction between electromagnetic energy and geophysical media in a number of remote sensing applications. Unlike long-range and intermediate-range radar systems, the sensitivity of short-range radars is not limited by thermal noise, but rather by reflections and leakage signals from the antenna and RF section. These leakage signals and their sidelobes are the primary sources of unwanted signals (coherent noise) in short-range FM radar systems. The authors have employed coherent noise reduction techniques to reduce the effects of these unwanted signal sources. Reduction of these coherent noise sources is critical to obtaining accurate backscatter measurements from geophysical targets. Recent advances include the use of phase correction to overcome limitations due to drift of local oscillators and effects of temperature changes on the system. The authors present results from the standard and phase-corrected coherent noise reduction techniques. These techniques increased the dynamic range of field and laboratory measurements of radar backscatter from sea ice and allows the authors to use data from past experiments that had previously been discarded due to low signal-to-noise ratio.

关键词： Noise reduction Radar antennas Radar remote sensing Backscatter Radar measurements Geophysical measurements Sea measurements Radar applications Radar scattering Electromagnetic scattering

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