Electrical and Electronic Engineering - Research Publications
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ItemOn stability properties of nonlinear time-varying systems by semi-definite time-varying Lyapunov can(IFAC, 2008-12-01)Stability properties (uniform stability/uniform asymptotic stability) of nonlinear time-varying systems are explored using positive semi-definite time-varying Lyapunov candidates whose derivative along trajectories is either non-positive or negative semi-definite. Once these positive semi-definite time-varying Lyapunov candidates are available, conditional stability properties on some specific sets can be used to ensure stability properties ( unform stability and unform asymptotic stability) of nonlinear time-varying systems.
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ItemNonlinear Gain l2 Stability of Nonlinear Feedback Systems with Quantized Measurements(IEEE - Institute of Electrical and Electronic Engineers, 2008)In this paper we address the stabilization problem of the nonlinear feedback systems with quantized measurements in the presence of bounded disturbances. Building on an approach applied in [Liberzon, Neˇsi´c, 2004] to the linear time-invariant systems with quantized feedback, we extend the results of [Kameneva, Neˇsi´c, 2008] to the quantized control systems with nonlinear dynamics. Using the time-sampled scheme proposed in [Liberzon, Neˇsi´c, 2004] and later used in [Kameneva, Neˇsi´c, 2008], we show that the nonlinear gain l2 stability is achievable for the nonlinear systems with quantized feedback.
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ItemOn mismatch between initializations at coder/decoder in quantized control(Elsevier BV, 2008-12-01)This paper analyzes the stability of linear systems with quantized feedback in the presence of a mismatch between the initial conditions at the coder and decoder. We show that using the scheme proposed in Liberzon, Nesic (2007) it is possible to achieve global exponential stability of linear systems with quantized feedback when the coder and decoder are initialized at different initial conditions.
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ItemInput-to-state stabilization of nonlinear systems with quantized feedback(IFAC - International Federation of Automatic Control, 2008-12-01)This paper addresses the stabilization problem of nonlinear feedback systems with quantized measurements in the presence of bounded disturbances. This paper is an extension of Liberzon, Nesic (2007) to nonlinear systems. Using the scheme proposed in Liberzon, Nesic (2007), we show that input-to-state stability with respect to bounded disturbances is achievable for nonlinear systems with quantized feedback.
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ItemDesign of multiple actuator-link control systems with packet dropouts(IFAC - International Federation of Automatic Control, 2008-12-01)This paper presents a novel design strategy for networked control systems, where a centralized controller needs to divide its attention between various actuators. Communication is via an unreliable network affected by data-dropouts and which allows access to only one actuator node at a time. To achieve good performance, control and network protocol are co-designed and signal predictions are sent to buffered actuator nodes. By using methods from predictive control theory, we show how closed loop stability in the presence of data-dropouts can be ensured.
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ItemTrends in Nonlinear Control(IEEE, 2008-01-01)The goal of this tutorial is therefore to illustrate three research themes that have undergone substantial developments in the past few years, and to highlight related open problems and possible avenues for future research. The paper is organized as follows. Section II discusses the role of invariant manifolds in nonlinear control design, with special attention to the problem of global observer design; Section III presents recent advances in the theory of hybrid systems, finally nonlinear digitally controlled systems are discussed in Section IV.
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ItemA Lyapunov-based small-gain theorem for hybrid ISS systems(IEEE, 2008-01-01)A Lyapunov-based small-gain theorem is presented for hybrid systems modelled using a recently proposed framework [9]. Lyapunov small-gain theorems for continuoustime and discrete-time systems are special cases of our result. Several examples including networked control systems and reset systems are presented to illustrate our main result. Our results are general and they apply to a range of other situations.
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ItemOn necessary and sufficient conditions for exponential and L-2 stability of planar reset systems(IEEE, 2008-01-01)In this paper we provide necessary and sufficient conditions for exponential stability and ℒ2 stability of planar reset systems, i.e., systems involving a First Order Reset Element (FORE) and a linear plant having dimension one. The proof relies on Lyapunov tools developed in a recent novel representation of a class of reset systems incorporating this special planar case. Explicit Lyapunov functions are given to show both exponential and ℒ2 stability. Based on this Lyapunov function, an explicit estimate of the ℒ2 gain, depending on the system's parameters, is provided. Moreover, via the same tools, it is shown that the gain estimates go to zero as certain parameters (in particular, the FORE pole) become arbitrarily large, thus allowing to establish a small gain result showing stability of certain higher order SISO linear plants under the action of a FORE.
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ItemObserver design for wired linear networked control systems using matrix inequalities(PERGAMON-ELSEVIER SCIENCE LTD, 2008-11-01)We design an observer-protocol pair to asymptotically reconstruct the states of a linear time-invariant (LTI) plant under communication constraints induced by the network. We parameterize a class of observers and protocols, and for a given network transmission interval, we derive sufficient conditions in terms of matrix inequalities for the existence of an observer-protocol pair in the considered class that asymptotically reconstructs the plant states.