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Midwest Symposium on Circuits and Systems (MWSCAS)

作者： R.S. Sreenivas B.H. Krogh Laboratory for Automated Systems and Information Processing Department of Electrical Engineering and Computer Engineering Carnegie Mellon University Pittsburgh PA USA

The notions of fairness and conflicts in live, bounded, and strongly connected Petri nets (PNs) are formally related. The PN model of a resource-sharing concurrent system (RSCS) is conflict free when the firing of an enabled transition does not disable another transition in the net. Conflicts in the PN represent unresolved resource allocation conditions. The PN is fair when the firing of any transition more than a given number of times is a sufficient condition for all the transitions in the net to have fired. When the PN is fair, no process in the system can be starved; that is resources are allocated so that all tokens progress through the net. Although these concepts are not equivalent, it is shown that they are strongly related to each other when the PN model is live, bounded, and strongly connected. A computational method for finding conflicts is presented, and the concepts are illustrated with an example of buffer allocation in a sorting algorithm.< >

关键词： Petri nets Resource management Sufficient conditions Laboratories Information processing Concurrent computing Sorting Large-scale systems Algorithm design and analysis Logic

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An approach for coordinating mobility and manipulation

An approach for coordinating mobility and manipulation

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IEEE International Conference on Systems engineering

作者： Carriker Khosla Krogh Laboratory for Automated Systems and Information Processing Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh PA USA

The authors discuss the problem of planning a task for a robotic system that consists of a manipulator mounted on a mobile base. The task planning problem is formulated as a nonlinear optimization problem. The cost of point-to-point motion in three-dimensional Cartesian space is decomposed into two components representing the qualitative difference between motion due to the mobile base and motion due to the manipulator system. Task specifications at each end of the motion impose constraints on the endpoint configurations. The resulting regions of feasible positions and configurations are unconnected and nonconvex. Thus, standard algorithms for nonlinear optimization lead to nonextremal solutions. A heuristic method is presented for searching a tree of starting points for a standard numerical algorithm to find a global minimum for the cost function. The problem formulation is illustrated for a three-degrees-of-freedom (DOF) manipulator on a simple two-DOF mobile base, and tradeoffs between base motion and manipulator motion are evaluated with respect to cost function weighting coefficients.< >

关键词： Mobile robots Numerical analysis Optimization methods Robots Mechanical variables control

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Efficient Synthesis of Control Logic for a Class of Discrete Event Systems

Efficient Synthesis of Control Logic for a Class of Discrete...

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American Control Conference (ACC)

作者： Lawrence E. Holloway Bruce H. Krogh Laboratory for Automated Systems and Information Processing Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh PA USA

Real-world applications of the emerging theory of controlled discrete event systems (DESs) will not be realized until the obstacle of computational complexity is overcome. This paper presents a step in that direction by developing a computationally efficient solution for a class of forbidden state problems. We consider DESs which can be modeled as cyclic controlled marked graphs (CMGs), a class of controlled Petri nets (CPNs). The distributed representation of the DES state in terms of the CMG marking permits an efficient specification of the forbidden states in terms of individual place markings. More importantly, we show that the graphical representation of the state transition logic in a CMG can be used to synthesize state feedback logic which is maximally permissive while guaranteeing the forbidden states will not occur. The practical application of the theoretical results is illustrated for an example of automated guided vehicle (AGV) coordination in a flexible manufacturing facility.

关键词： Control system synthesis Logic Discrete event systems Automatic control Petri nets State feedback Laboratories Information processing Application software Computational complexity

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Parameter extraction of microwave transistors using tree annealing

Parameter extraction of microwave transistors using tree ann...

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IEEE/Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits

作者： M.B. Steer G.L. Bilbro R.J. Trew S.G. Skaggs High Frequency Electronics Laboratory and the Center for Communications and Signal Processing Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

The authors have developed an alternative formulation of simulated annealing using a tree-based Metropolis procedure called tree annealing. Tree annealing is suited to continuous optimization problems and, in particular, to transistor parameter extraction. The tree annealing optimization algorithm was used to extract the parameters of the HBT (heterojunction bipolar transistor) of U.K. Mishra et al. (IEDM Tech. Dig., p.180-3, Dec. 1988) using a physically based equivalent circuit and deembedded scattering parameter measurements from 45 MHz to 26.5 GHz. Good results were obtained from the parameter extraction technique, and the ability of MFA not to be locked in local minima enabled a physically based equivalent circuit model to be used. Tree annealing is essentially a smart random search technique and so requires many more functional evaluations than do gradient-based minimization algorithms. However, no startling guess is required, and the bounds on parameter values can be widely separated with little effect on optimization time.< >

关键词： Parameter extraction Microwave transistors Simulated annealing Equivalent circuits Combinatorial mathematics Robustness Frequency Laboratories Microwave communication Signal processing

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Simulated hearing loss as a baseline for the assessment of auditory function in cochlearly impaired listeners

Simulated hearing loss as a baseline for the assessment of a...

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Annual Northeast Bioengineering Conference

作者： S. Buus M. Florentine Center for Communication and Digital Signal Processing (416 DA) Department of Electrical and Computer Engineering Northeastern University Boston MA USA Communication Research Laboratory (226 FR) Department of Speech-Language Pathology and Audiology Northeastern University Boston MA USA

An overview is presented of results obtained in listeners with real and simulated impairments. Spectral processing is assessed by psychoacoustical tuning curves and growth-of-masking functions; temporal processing is assessed by temporal integration and gap detection thresholds. When comparisons are made to normal listeners tested in the quiet, impaired listeners generally show deficits on all these tasks. When the comparisons are made to simulated impairments, some impaired listeners show no deficits, whereas others still show deficits. These results indicate that abnormal intensity perception is responsible for some, but not all, of impaired listeners' apparent deficits in spectral and temporal processing. In many cases, however, it appears that spectral and temporal processing, per se, are altered in the impaired auditory system.< >

关键词： Deafness Psychoacoustic models Ear Frequency Auditory system Tuning Acoustic noise Noise shaping Testing Spectral shape

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INTERFERENCE-TOLERANT TIME-DIFFERENCE-OF-ARRIVAL ESTIMATION FOR MODULATED SIGNALS

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IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND SIGNAL processing 1988年第9期36卷 1385-1395页

作者： GARDNER, WA CHEN, CK Signal and Image Processing Laboratory Department of Electrical Engineering and Computer Science University of California슠Davis Davis CA USA Signal and Image Processing Laboratory Department of Electrical Engineering and Computer Science University of California Davis Davis CA USA

A method for estimation of the difference in the times of arrival of wavefronts of two separate sensors is introduced. The method, called SPECCORR, exploits the spectral correlation property, called spectral coherence, that essentially all modulated signals exhibit to obtain estimates that are highly tolerant to severely corruptive noise and interference. This tolerance is explained theoretically and demonstrated with simulations.< >

关键词： Interference Time difference of arrival Noise measurement Narrowband Autocorrelation Direction of arrival estimation Antenna measurements Design methodology Signal design

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SIGNAL INTERCEPTION - A UNIFYING THEORETICAL FRAMEWORK FOR FEATURE DETECTION

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IEEE TRANSACTIONS ON COMMUNICATIONS 1988年第8期36卷 897-906页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical Engineering and Computer Science University of California Davis CA USA

The unifying framework of the spectral-correlation theory of cyclostationary signals is used to present a broad treatment of weak, random signal detection for interception purposes. The relationships among a variety of previously proposed ad hoc detectors, optimum detectors, and newly proposed detectors are established. The spectral-correlation-plane approach to the interception problem is put forth as especially promising for detection, classification, and estimation in particularly difficult environments involving unknown and changing noise levels and interference activity. A fundamental drawback of the popular radiometric methods in such environments is explained.

关键词： Cyclostationary signal Environments Frameworks Unknown interceptions RANDOM SIGNALS feature detections correlation theory

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PHASE SENSITIVITY PROPERTIES OF CASCADED DIGITAL LATTICE ALLPASS FILTERS

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SIGNAL processing 1988年第1期15卷 1-21页

作者： REGALIA, PA MITRA, SK Signal Processing Laboratory Department of Electrical and Computer Engineering University of California Santa Barbara CA 93106 U.S.A.

The phase sensitivity with respect to coefficient errors is studied for a class of lattice digital allpass filters. It is shown that corresponding to each lattice parameter there is a set of frequencies for which the phase response remains invariant to an arbitrary perturbation of the parameter. In addition, a simple result of sensitivity “amplification” in lossless two-pair networks is derived, which is used to obtain means and bounds on the sensitivity functions for these lattice structures in term of the lattice parameters. From these results some useful coefficient sensitivity properties are inferred. A practical example is included to better understand the interaction of sensitivity mechanisms in lattice allpass filter realizations, in the context of transfer functions realized as the parallel connection of two allpass filters. Finally, it is shown that the order reduction process intrinsic to the lattice synthesis procedure minimizes the L ∞ norm of the phase sensitivity at each step. Für eine Klasse digitaler Allpaßfilter in Gitterstruktur wird die Empfindlichkeit der Phase gergenüber Koeffizientenfehlern betrachtet. Es wird gezeigt, daß es bezüglich eines jeden Filterparameters gewisse Frequenzpunkte gibt, in denen der Phasengang auch bei beliebiger Parameterverfälschung unverändert bleibt. Darüber hinaus wird in einfacher Form eine “Empfindlichkeits-Verstärkung” in verlustfreien Signalfluß-Zweitor-Netzwerken hergeleitet. Sie wird dazu benützt, Mittel- und Grenzwerte für die Empfindlichkeitsfunktionen dieser Gitterstrukturen, ausgedrückt in den Filterparametern, zu gewinnen. Aus diesen Ergebnissen wird auf einige nützliche Eigenschaften der Koeffizientenempfindlichleit geschlossen. Ein praktisches Beispiel schließt sich an; es dient zum besseren Verständnis des Zusammenwirkens von Empfindlichkeitsmechanismen in Gitterstruktur-Allpässen, wie sie zur Realisierung von Übertrangungsfunktionen durch eine parallel-Anordnung von zwei Allpaßfiltern verwendet werden.

关键词： Digital lattice filters lossless two-pair networks phase sensitivity invariant frequencies

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CORRELATION ESTIMATION AND TIME-SERIES MODELING FOR NONSTATIONARY PROCESSES

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SIGNAL processing 1988年第1期15卷 31-41页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical Engineering and Computer Science University of California Davis CA 95616 U.S.A.

Various types of statistical signal processing require the estimation of time-variant correlation functions and the fitting of time-variant models for nonstationary processes. In this paper, the situations for which nonstationary probabilistic correlation functions can be accurately estimated from a single sample path of a stochastic process are delineated. These include only (i) known form of nonstationarity, (ii) periodic or almost periodic nonstationarity, and (iii) slowly fluctuating nonstationarity. Known methods of estimation for each of these situations are reviewed within the unifying framework of orthogonal series expansions. The fact that estimators based on orthogonal series expansions for nonstationary correlation functions other than (i)–(iii) cannot be guaranteed to be accurate is established. Ramifications for time-variant autoregressive model fitting are discussed. Verschiedene Aufgabenbereiche der Signalverarbeitung erfordern die Schätzung zeitvarianter Korrelationsfunktionen und die zeitvariante Modellierung nichtstationärer Prozesse. Im folgenden werden die Situationen dargelegt, für die nicht-stationäre Korrelationsfunktionen aus einem einzigen Repräsentanten eines Prozesses geschätzt werden können. Erfaßt werden können nur Fälle mit (i) bekannter Form der Instationarität, (ii) periodischer oder fast-periodischer Instationarität und (iii) langsam veränderlicher Instationarität. Die bekannten Schätzverfahren für jede dieser Gegebenheiten werden in einem einheitlichen Rahmen, dem der Orthogonalreihen-Entwicklung, zusammengestellt. Die Grenzen der Nutzung von Reihenentwicklungen bei der Schätzung nicht-stationärer Korrelationsfunktionen werden aufgezeigt. Variationsmöglichkeiten für die zeitvariante AR-Modellierung werden diskutiert. De nombreuses operations de traitement du signal requièrent l'estimation de fonctions de corrélation dependent du temps et la construction de modèles variant avec le temps pour les processus nonstationnaires. Dans cet a

关键词： Nonstationary correlation correlation estimation time-series modeling nonstationary time-series

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Connections between three-dimensional inverse scattering and linear least-squares estimation of random fields

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Acta Applicandae Mathematicae 1988年第3期13卷 267-289页

作者： Yagle, Andrew E. Communications and Signal Processing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor United States

The three-dimensional Schrödinger equation inverse scattering problem with a nonspherically-symmetric potential is related to the filtering problem of computing the linear leastsquares estimate of the three-dimensional random field on the surface of a sphere from noisy observations inside the sphere. The relation consists of associating an estimation problem with the inverse scattering problem, and vice-versa. This association allows equations and quantities for one problem to be given interpretations in terms of the other problem. A new fast algorithm is obtained for the estimation of random fields using this association. The present work is an extension of the connections between estimation and inverse scattering already known to exist for stationary random processes and one-dimensional scattering potentials, and isotropic random fields and radial scattering protentials. © 1988 Kluwer Academic Publishers.

关键词： AMS subject classifications (1980): 35R30, 93E11, 35L20 fast algorithms Inverse scattering linear least-squares estimation random fields

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