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20
Comparison of Riemann and Lebesgue sampling for first order stochastic systems
 In Proceedings of IEEE Conference on Decision and Control
, 2002
"... The normal approach to digital control is to sample periodically in time. Using an analog of integration theory we can call this Riemann sampling. Lebesgue sampling or event based sampling, is an alternative to Riemann sampling. It means that signals are sam pled only when measurements pass certain ..."
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Cited by 154 (0 self)
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The normal approach to digital control is to sample periodically in time. Using an analog of integration theory we can call this Riemann sampling. Lebesgue sampling or event based sampling, is an alternative to Riemann sampling. It means that signals are sam pled only when measurements pass certain limits. In this paper it is shown that Lebesgue sampling gives better performance for some simple systems. 1.
Comparison of periodic and event based sampling for firstorder stochastic systems
 Proceedings of the 14th IFAC World Congress
, 1999
"... Abstract: Event based sampling is an alternative to traditional equidistant sampling. This means that signals are sampled only when measurements pass certain limits. Systems with event based sampling are much harder to analyze than systems with periodic sampling because the time varying nature of th ..."
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Cited by 49 (1 self)
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Abstract: Event based sampling is an alternative to traditional equidistant sampling. This means that signals are sampled only when measurements pass certain limits. Systems with event based sampling are much harder to analyze than systems with periodic sampling because the time varying nature of the closed loop system can not be avoided. In this paper we investigate some simple first order systems with event based sampling and compare achieved closed loop variance and sampling rate with results from periodic sampling. The analysis shows thateventbasedsamplinggivesbetterperformancethanperiodicsampling. Copyright c 1999 IFAC
Fast switches in relay feedback systems
 AUTOMATICA 35 (1999) 539—552
, 1999
"... Relays are common in automatic control systems. Even linear systems with relay feedback are, however, far from fully understood. New results are given about the behavior of these systems via a statespace approach. It is proved that there exist multiple fast switches if and only if the sign of the ..."
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Cited by 29 (6 self)
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Relays are common in automatic control systems. Even linear systems with relay feedback are, however, far from fully understood. New results are given about the behavior of these systems via a statespace approach. It is proved that there exist multiple fast switches if and only if the sign of the first nonvanishing Markov parameter of the linear system is positive. Fast switches are shown to occur as part of stable limit cycles. An analysis is developed for these limit cycles that illustrates how they can be predicted.
An Introduction to Control and Scheduling
 39TH IEEE CONFERENCE ON DECISION AND CONTROL
, 1999
"... The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling o ..."
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Cited by 20 (6 self)
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The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling of imprecise calculations. The report also presents the background, motivation, and research topics in the ARTES project “Integrated
Dither for smoothing relay feedback systems
 IEEE Trans. on Circuits and SystemsI: Fundamental Theory and Applications
, 2003
"... Dither signals are commonly used for compensating nonlinearities in feedback systems in electronics and mechanics. The seminal works by Zames and Shneydor and more recently by Mossaheb present rigorous tools for systematic design of dithered systems. Their results rely however on a Lipschitz assumpt ..."
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Cited by 7 (5 self)
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Dither signals are commonly used for compensating nonlinearities in feedback systems in electronics and mechanics. The seminal works by Zames and Shneydor and more recently by Mossaheb present rigorous tools for systematic design of dithered systems. Their results rely however on a Lipschitz assumption on the nonlinearity and thus do not cover important applications with discontinuities. The aim of this thesis is to provide some ideas and tools on how to analyse and design dither in nonsmooth systems. In particular, it is shown that a dithered relay feedback system can be approximated by a smoothed system. Guidelines are given for tuning the amplitude and the period time of the dither signal, in order to stabilize the nonsmooth system. Stability results based on Popovlike and ZamesFalb criteria jointly with some Linear Matrix Inequalities are proposed. Moreover it is argued that in dithered relay feedback systems the shape of dither signals is relevant for stabilization. Some peculiar behaviours of relay feedback systems dithered with a particular class of dither signals are presented. When the dither signal is a square wave, the dithered system can exhibit an asymmetric periodic orbit, though the smoothed system is asymptotically stable. We even show an example in which, by using a trapezoidal dither signal, both systems have a stable oscillation, but the period time for the oscillation of the smoothed system is different from the one of the dithered system. Finally some engineering applications are presented in order to show the usefulness of techniques and results discussed in the thesis. Thesis Supervisor: Franco Garofalo, Professor of Automatic Control Thesis Supervisor: Francesco Vasca, Associate Professor of Automatic Control Acknowledgements Yes, ...it's fina...
Averaging of nonsmooth systems using dither
, 2006
"... It was shown by Zames and Shneydor and later by Mossaheb that a highfrequency dither signal of a quite arbitrary shape can be used to narrow the effective nonlinear sector of Lipschitz continuous feedback systems. In this paper, it is shown that also discontinuous nonlinearities of feedback systems ..."
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Cited by 6 (2 self)
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It was shown by Zames and Shneydor and later by Mossaheb that a highfrequency dither signal of a quite arbitrary shape can be used to narrow the effective nonlinear sector of Lipschitz continuous feedback systems. In this paper, it is shown that also discontinuous nonlinearities of feedback systems can be narrowed using dither, as long as the amplitude distribution function of the dither is absolutely continuous and has bounded derivative. The averaged system is proven to approximate the dithered system with an error of the order of dither period.
ON THE ROBUSTNESS OF PERIODIC SOLUTIONS IN RELAY FEEDBACK SYSTEMS
 15TH TRIENNIAL WORLD CONGRESS, BARCELONA, SPAIN
"... Structural robustness of limit cycles in relay feedback systems is studied. Motivated by a recent discovery of a novel class of bifurcations in these systems, it is illustrated through numerical simulation that small relay perturbations may change the appearance of closed orbits dramatically. It i ..."
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Cited by 5 (1 self)
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Structural robustness of limit cycles in relay feedback systems is studied. Motivated by a recent discovery of a novel class of bifurcations in these systems, it is illustrated through numerical simulation that small relay perturbations may change the appearance of closed orbits dramatically. It is shown analytically that certain stable periodic solutions in relay feedback systems are robust to relay perturbations.
Global Analysis Of ThirdOrder Relay Feedback Systems
, 1996
"... Relays are common in automatic control systems. It is wellknown that a linear dynamical system under relay feedback can give complex oscillations. In this paper it is proved that several of these phenomena can actually be captured by thirdorder systems. It is shown that there exist systems giving ..."
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Cited by 3 (1 self)
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Relays are common in automatic control systems. It is wellknown that a linear dynamical system under relay feedback can give complex oscillations. In this paper it is proved that several of these phenomena can actually be captured by thirdorder systems. It is shown that there exist systems giving arbitrarily fast relay switches similar to sliding modes. A novel method for analyzing linear dynamical systems under relay feedback is also introduced. Trajectories for a class of third order systems are shown to converge in a certain sense.
A ROBUST VARIABLE STRUCTURE CONTROLLER FOR MIXED CONTINUOUS / BANGBANG SYSTEMS
"... john.valasek @ wmich.edu A systematic controller design procedure is developed for the class of linear timeinvariant systems which use both continuous and bangbang control effectors. The sampleddata regulator and its associated weighting matrices and cost function are extended to this class of sy ..."
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Cited by 3 (3 self)
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john.valasek @ wmich.edu A systematic controller design procedure is developed for the class of linear timeinvariant systems which use both continuous and bangbang control effectors. The sampleddata regulator and its associated weighting matrices and cost function are extended to this class of system, and are used to modulate the bangbang effector to achieve desired performance levels. Stability, sensitivity, and robustness are quantified, and the controller synthesis methodology is illustrated for a generic secondorder plant with one continuous effector and one bangbang effector. Results indicate that the resulting controllers are stable, not overly sensitive to the designer selected bangbang weighting, and possesses good robustness with respect to parametric structured uncertainties. The methodology provides the designer with insight required to systematically tune closedloop performance.
Transfer function identification by using selfoscillations
 Proc. of the 15th Mediterranean Conference on Control and Applications
, 2007
"... AbstractThe work presented in this paper deals with the process of transfer function identification by using selfoscillation method (autotuning identification method). The algorithm is given in a general matrix form and some modifications are introduced. The modifications of the algorithm include ..."
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Cited by 2 (0 self)
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AbstractThe work presented in this paper deals with the process of transfer function identification by using selfoscillation method (autotuning identification method). The algorithm is given in a general matrix form and some modifications are introduced. The modifications of the algorithm include augmentation of the initial algorithm for Type k systems, systems with delays and discretetime systems. The paper also includes simulation examples which describe the introduced modifications. Apart from being rather simple, this method is applicable to real systems. Its greatest advantage is quick identification of a transfer function (depends on the system).