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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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Phase stabilization of reference signals in analog fiber-optic links

Phase stabilization of reference signals in analog fiber-opt...

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International Topical Meeting on Microwave Photonics (MWP)

作者： M. Shadaram V. Gonzalez J. Ceniceros N. Shah J. Mayers S. Pappert D. Lafaw Electrical and Computer Engineering Department University of Texas El Paso El Paso TX USA Control and Ocean Survedhce Center Research Development Test & Evaluation Division Naval Command San Diego CA USA Laboratory of Physical Science College Park MD USA

A feedback technique that utilizes a special optical modulator is used to reduce the phase noise of RF signals in microwave fiber-optic links. Experimental results indicate a reduction in the phase noise of a 150 MHz ... 详细信息

关键词： Phase noise Frequency Optical receivers Optical feedback Optical modulation Optical noise Phase modulation Optical transmitters Phase detection Optical sensors

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GLOBAL INTERNAL STABILIZABILITY DOES NOT IMPLY GLOBAL EXTERNAL STABILIZABILITY FOR SMALL SENSOR DISTURBANCES

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IEEE TRANSACTIONS ON AUTOMATIC control 1995年第12期40卷 2119-2122页

作者： FREEMAN, R Center for Control Engineering and Computation Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

It was shown in [1] that for control-affine nonlinear systems, global asymptotic stabilizability via continuous state feedback implies global input-to-state stabilizability with respect to actuator disturbances. We show that the analogous result for sensor disturbances does not hold: we construct a second-order system which admits a continuous memoryless globally asymptotically stabilizing state feedback controller but for which no such controller can prevent finite escape times from every initial condition in the presence of small sensor disturbances.

关键词： Asymptotic stability Actuators Sensor systems control systems Nonlinear systems Nonlinear control systems State feedback Robust stability control theory Working environment noise

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PARALLEL IMPLEMENTATION OF THE FUZZY ARTMAP NEURAL-NETWORK PARADIGM ON A HYPERCUBE

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EXPERT SYSTEMS 1995年第1期12卷 39-53页

作者： MALKANI, A VASSILIADIS, CA Department of Electrical and Computer Engineering College of Engineering and Technology Ohio University Main Campus Athens OH 45701 USA [?]*Currently with Recom Technologies Inc. AI Research Branch NASA Ames Research Center Moffett Field CA 94035 USA

The recent surge of interest in connectionist models arose through the availability of high speed parallel supercomputers and the advent of new leaning algorithms. The computations performed on concurrent architectures are less costly than similar ones performed on sequential machines. In this paper, the design and implementation of a parallel version of fuzzy ARTMAP (Carpenter et al. 1992), which encompasses both neural and fuzzy logic, is discussed. Fuzzy ARTMAP is a supervised leaning algorithm utilising two fuzzy ART modules and an associated mapping network. A simplified version of fuzzy ARTMAP (SFAM) was designed by incorporating a simplification of the match tracking concept on unsupervised fuzzy ART paradigms. The proposed simplified version consists of only one fuzzy ART module and an associated mapping network. A parallel fuzzy ARTMAP (PFAM) algorithm is then designed and implemented on a hypercube simulator (iPSC). The algorithm is parallelised for any architecture and, with the exception of issues related to communications, the implementation remains the same on any type of parallel machine. PFAM enjoys the advantage of reduced training time that makes the algorithm a successful candidate for applications that require both online testing and training. Such applications can range from underwater sonar detection and chemical plant processing control to nuclear reactor process control, flexible manufacturing and systems analysis.

关键词： Neural networks

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A dual-mode algorithm for blind equalization of qam signals: cadama 29

A dual-mode algorithm for blind equalization of qam signals:...

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29th Asilomar Conference on Signals, Systems and computers, ACSSC 1995

作者： Axford, R.A. Milstein, L.B. Zeidler, J.R. Communications Department Control and Ocean Surveillance Center RDTE Division Naval Command San DiegoCA921 52-5001 United States Department of Electrical and Computer Engineering University of Califomia at San DiegoCA92093 United States

ISBN: (纸本)0818673702

The misadjustment exhibited by the constant modulus algorithm (CMA) can be excessive when it is used for blind equalization of QAM signals, thus degrading the performance of decision-directed carrier recovery algorithms. This paper introduces a hybrid blind equalization algorithm, the CMA-assisted decision adjusted modulus algorithm (CADAMA), that exhibits reductions in misadjustment on the order of 18 to 25 dB for higher order QAM constellations. CADAMA employs CMA to perform initial adjustment of the equalizer, and switches to decision adjusted modulus algorithm (DAMA) mode when the amplitude equalization has been sufficiently accomplished. DAMA is based on a phase-blind cost function that goes to zero at each ring of the QAM constellation. © 1995 IEEE.

关键词： Blind equalization

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First passage risk-sensitive criterion for stochastic evolutions

First passage risk-sensitive criterion for stochastic evolut...

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American control Conference (ACC)

作者： C.D. Charalambous J.L. Hibey Measurement and Control Engineering Research Center College of Engineering Idaho State University Pocatello ID USA Department of Electrical and Computer Engineering Old Dominion University Norfolk VA USA

The purpose of this paper is to investigate in an infinite dimensional space, the first passage problem with a risk-sensitive performance criterion, and to illustrate the asymptotic behavior of the associated value function, as related to differential games arising in robust control theory. The model of interest is described by a controlled stochastic evolution with small Wiener noise intensity. The Wiener and state processes take values in infinite dimensional Hilbert spaces. The objective is to control the evolution of the state process, so as to keep it in some compact set G. By using a logarithmic transformation, it is shown that in the limit as the small noise parameter, /spl epsiv//spl rarr/0, the risk-sensitive value function converges to the value of a deterministic differential game. In the limit as the risk parameter, /spl theta//spl rarr/0, the risk-sensitive value function converges to the value function corresponding to the mean escape time problem. In addition, a lower bound on the first escape time is derived which is slightly different from the known bound for finite dimensional systems. The magnitude of the lower bound derived here, increases as /spl theta/ increases, thus robustness is achieved.

关键词： Stochastic processes Hilbert space Equations Electric variables measurement control engineering Educational institutions Game theory Robust control Stochastic resonance Robustness

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Wide temperature operation of a PWM DC-DC convertor

Wide temperature operation of a PWM DC-DC convertor

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Conference Record of the IEEE Industry Applications Society Annual Meeting (IAS)

作者： B. Ray R.L. Patterson Department of Electrical and Computer Engineering University of Puerto Rico Mayaguez Puerto Rico NASA Lewis Research Center Cleveland OH USA

Wide temperature electronics is of great interest for space exploration programs. In this study, the wide temperature (-185/spl deg/C to 200/spl deg/C) operation of a 150 W, 50 kHz, 24/48 V pulse-width modulated (PWM) boost DC-DC power converter is reported. The power MOSFET, the power rectifier and the input inductor were placed inside a temperature chamber, whereas the rest of the power and control circuitry as well as all measuring instruments were at room temperature. The power converter efficiency varied between 92.2% and 89.4% in the entire temperature range. The power MOSFET loss decreased with decreasing temperatures. For the diode rectifier, loss increased with decreasing as well as increasing temperatures compared to room temperature operation. The inductor loss also increased due to increasing as well as decreasing temperatures compared to room temperature operation. Overall, the power converter operated successfully in a wide temperature range designed with commercially available components. Wide temperature operation of power capacitors and control circuitry, and the relevant reliability issues for passive and active components are to be addressed for design and operation of wide temperature electronic systems.

关键词： Pulse width modulation Pulse width modulation converters MOSFET circuits Power MOSFET Rectifiers Inductors Temperature control Temperature distribution Power system reliability Space exploration

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Hybrid control in air traffic management systems

Hybrid control in air traffic management systems

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IEEE Conference on Decision and control

作者： S. Sastry G. Meyer C. Tomlin J. Lygeros D. Godbole G. Pappas Department of Electrical Engineering & Computer Sciences University of California Berkeley CA USA MS 210-3 NASA Ames Research Center Moffett Field CA USA

In a new collaborative project involving the University of California, Berkeley, nasa Ames Research center, and Honeywell Systems Research center, the authors have begun the study of hierarchical, hybrid control systems in the framework of air traffic management systems (ATMS). The need for a new ATMS arises from the overcrowding of large urban airports and the need to more efficiently land and take off larger numbers of aircraft without building new runways. Technological advances that make a more advanced air traffic control system a reality include the availability of relatively inexpensive and fast real time computers (both on board the aircraft and in the control tower) and global positioning systems. The usefulness of these technological advances is currently limited by today's air traffic control system, which involves the use of "freeways" in the Terminal Radar Approach control (TRACON) region around urban airports. These freeways are set approach patterns to runways which do not allow for the possibility of so-called "free flight" by an aircraft to its destination. Limiting the aircraft trajectories in this manner results in the addition of both planned and unplanned delays to air travel.

关键词： control systems Air traffic control Airports Aircraft manufacture Collaboration nasa Project management Real time systems Aerospace control Poles and towers

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Preisach modeling of piezoceramic and shape memory alloy hysteresis

Preisach modeling of piezoceramic and shape memory alloy hys...

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IEEE Conference on control Technology and Applications (CCTA)

作者： D. Hughes 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

Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test data for a multi-sheet piezoceramic actuator (made of lead zirconate titanate) attached to a flexible beam are presented and are seen to be very consistent with the two Preisach model properties. The commanded parameter is the sheet transverse electric field while the measured parameter is an approximately colocated strain induced in the beam. Equivalent data for a Nitinol SMA wire muscle, attached to the same beam, are also presented. The input and output parameters are the SMA current and a beam strain respectfully. The minor loop and wiping out evidence is less strong than that of the piezoceramic case, but encouraging. In all experiments the quasi-steady state responses were generated in order to avoid exciting beam flexible modes which would complicate the analysis.

关键词： Piezoelectric materials Shape memory alloys Hysteresis Strain measurement Shape control Open loop systems Testing Actuators Titanium compounds Electric variables measurement

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Synthesized passive feedback control of sensor-rich smart structures-experimental results

Synthesized passive feedback control of sensor-rich smart st...

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IEEE Conference on control Technology and Applications (CCTA)

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

Passivity based controllers are used in structural control due to their inherent robustness properties. These controllers require sensor/actuator collocation. In this paper, we consider the design of a "squaring down" matrix which renders a system passive by using a linear combination of all collocated and non-collocated sensor/actuator pairs. The design uses experimental transfer functions and does not require the knowledge of the system model. The problem of finding the squaring down matrix is cast as a solution to a set of linear matrix inequalities (LMIs) subject to some additional performance considerations. The design procedure of the squaring down matrix assumes that velocity information is available from the sensors which is not generally the case. We show that the squaring down matrix can be implemented without the use of such velocity information. We provide experimental results gathered from the single link flexible beam setup in the C/sub La/MS laboratory at RPI to show that implementation of passive loops without velocity measurements provides very good results.

关键词： Feedback control Linear matrix inequalities Intelligent sensors control system synthesis Robust control Sensor systems Hydraulic actuators Transfer functions Laboratories Economic indicators

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