Electrical and Electronic Engineering - Research Publications
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ItemExplicit Lyapunov functions for stability and performance characterizations of FOREs connected to an integrator(IEEE, 2006)In this paper we provide explicit Lyapunov functions that prove that a First Order Reset Element (FORE) in negative feedback interconnection with an integrator is exponentially stable for any, positive or negative, value of the pole of the FORE. The Lyapunov functions also allow to establish finite gain L2 stability from a disturbance input acting at the input of the plant to the plant output. L2 stability is established by giving a bound on the corresponding L2 gains. The framework used for the characterization of the system dynamics and for the stability and performance analysis corresponds to the ideas first proposed in (Nesic et al. IFAC 2005) and (Zaccarian et al. ACC 2005).
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ItemSet-point stabilization of SISO linear systems using First Order Reset Elements(IEEE, 2007-01-01)In this paper we further develop on a novel representation of first order reset elements (FORE) control systems for SISO plants. We study here the problem of guaranteeing asymptotic tracking of constant references for general plants, which may or may not contain an integrator (namely, an internal model of the constant reference signal). We propose a generalization of the FORE which allows to guarantee asymptotic tracking of constant references when the plant parameters are perfectly known. Robustness of the scheme follows from the L infin stability properties of the FORE control schemes. The proposed approach is successfully illustrated on a simulation example.
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ItemFurther results on robustness of linear control systems with quantized feedback(IEEE, 2007-01-01)This paper extends results from [5], where input-to-state stabilization (ISS) of linear systems with quantized feedback was considered. In this paper, we show that using the scheme proposed in [5] it is also possible to achieve (nonlinear gain) l2 stabilization for linear systems.
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ItemOn cascaded raman amplifier control(IEEE, 2006-01-01)Extremum Seeking Control is applied to the control of cascaded Raman amplifiers for long-haul wavelength division multiplexed optical communications systems. Simulation demonstrates the effectiveness of this control strategy.
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ItemPath-following in the presence of unstable zero dynamics: An averaging solution for nonlinear systems(IEEE, 2007-01-01)We consider a path-following problem in which the goal is to ensure that the error between the output and the geometric path asymptotically is less than a prespecifled constant, while guaranteeing output's forward motion along the path and boundedness of all states. For a class of nonlinear systems in which the only input into unstable zero dynamics is system's output and paths satisfying certain geometric condition a solution to this problem was given in [12]. For the same class of systems but under more stringent conditions on the path geometry here we develop a simpler solution to the above problem. We assume here that the path is periodic which allows us to exploit averaging tools to construct an open-loop timeperiodic control law for the path parameter instead of a hybrid control law developed in [12].
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ItemAn application of extremum seeking in cascaded optical amplifier control(IEEE, 2006)This paper considers the control of a particular type of optical amplifier that finds application in long-haul wavelength division multiplexed optical communications systems. The objective of this consideration is to demonstrate an application of extremum seeking to the regulation of amplifier output signal power across a range of signal wavelengths, where limited control authority is available. Although such amplifiers are nonlinear and distributed parameter devices, an extremum seeking design is demonstrated to be a promising approach for achieving the stated amplifier control objectives.
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ItemA novel Smith predictor scheme applied to a fully actuated inverted pendulum(Elsevier Science, 2006)In this paper we show the effectiveness of a novel control scheme for deadtime systems recently proposed in (Zaccarian and Nesi_c, 2006 American Control Conference). In that paper, the prediction problem is formally stated and shown to be achievable for any type of dead-time system, as long as it is possible to determine a stabilizing control law. We propose here the employment of an LMI-based contro strategy for this stabilization task and show the advantages of the novel modified Smith predictor scheme on a MIMO example. In particular, satisfactory simulation results are given both for the linearized model and for the nonlinear model of an inverted pendulum subject to disturbances.
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ItemNonlinear sampled-data observer design via approximate discrete-time models and emulation(International Federation of Automatic Control, 2005)We study observer design for sampled-data nonlinear systems using two approaches: (i) the observer is designed via an approximate discrete-time model of the plant; (ii) the observer is designed based on the continuous-time plant model and then discretized for sampled-data implementation (emulation). In each case we present Lyapunov conditions under which the observer design guarantees semiglobal practical convergence for the unknown exact discrete-time model. The semiglobal region of attraction is expanded by decreasing the sampling period. The practical convergence set is shrunk by decreasing either the sampling period, or a modelling parameter which refines the accuracy of the approximate model.
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