Electrical and Electronic Engineering - Research Publications
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ItemChanging supply rates for input-output to STA testable discrete-time systems(Elsevier Science, 2002)We present results on changing supply rates for input-output to state stable (IOSS) discrete-time nonlinear systems. Our results can be used to combine two Lyapunov functions, none of which can be used to verify that the system has a certain property, into a new Lyapunov function from which the property of interest can be concluded.We present several applications of our results to discrete-time systems such as a l_a Lasalle criteria for input to state stability (ISS) and input to state stability with positive semide_nite Lyapunov functions.
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ItemLyapunov based small-gain theorem for parameterized discrete-time interconnected ISS systems(IEEE, 2002)Input-to-state stability (ISS) of a feedback interconnection of two discrete-time ISS systems satisfying an appropriate small gain condition is investigated via the Lyapunov method. In particular, an ISS Lyapunov function for the overall system is constructed from the ISS Lyapunov functions of the two subsystems. We consider parameterized families of discrete-time systems that naturally arise when an approximate discrete-time model is used to design a controller for a sampled-data system.
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ItemInput-to-state stabilization for nonlinear sampled-data systems via approximate discrete-time plant models(IEEE, 2001)We provide a framework for the design of L∞ stabilizing controllers via approximate discrete-time models for sampled-data nonlinear systems with disturbances. In particular, we present sufficient conditions that guarantee that a discrete-time controller that input-to-state stabilizes an approximate discrete-time model of a nonlinear continuous-time plant with disturbances would also input-to-state stabilize (in an appropriate sense) the exact discrete-time plant model.
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ItemA note on preservation of dissipation inequalities under sampling: the dynamic feedback case(IEEE, 2001)We present a general and unified framework for the design of nonlinear digital controllers using the emulation method for nonlinear systems with disturbances. Several results on preservation of general dissipation inequalities under sampling are presented. We consider general dynamic feedback controllers case, which generalizes results for static controllers in [8].
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ItemDiscrete-time Lyapunov-based small-gain theorem for parameterized interconnected ISS systems(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2003-10)Input-to-state stability (ISS) of a feedback interconnection of two discrete-time ISS systems satisfying an appropriate small gain condition is investigated via the Lyapunov method. In particular, an ISS Lyapunov function for the overall system is constructed from the ISS Lyapunov functions of the two subsystems. We consider parameterized families of discrete-time systems that naturally arise when an approximate discrete-time model is used in controller design for a sampled-data system.
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ItemOpen- and closed-loop dissipation inequalities under sampling and controller emulation(ELSEVIER, 2002-01-01)We present a general and unified framework for the design of nonlinear digital controllers using the emulation method for nonlinear systems with disturbances. It is shown that if a (dynamic) continuous-time controller, which is designed so that the continuous-time closed-loop system satisfles a certain dissipation inequality, is appropriately discretized and implemented using sample and zero-order-hold, then the discrete-time model of the closed-loop sampled-data system satisfies a similar dissipation inequality in a semiglobal practical sense (sampling period is the parameter that we can adjust). We consider two different forms of dissipation inequalities for the discrete-time model: the "weak" form and the "strong" form. The results are also applicable for open-loop systems.
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ItemA note on input-to-state stabilization for nonlinear sampled-data systems(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2002-07)We provide a framework for the design of L∞ stabilizing controllers via approximate discrete-time models for sampled-data nonlinear systems with disturbances. In particular, we present sufficient conditions under which a discrete-time controller that input-to-state stabilizes an approximate discrete-time model of a nonlinear plant with disturbances would also input-to-state stabilize (in an appropriate sense) the exact discrete-time plant model.
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ItemChanging supply rates for input-output to state stable discrete-time nonlinear systems with applications(PERGAMON-ELSEVIER SCIENCE LTD, 2003-05-01)We present results on changing supply rates for input-output to state stable discrete-time nonlinear systems. Our results can be used to combine two Lyapunov functions, none of which can be used to verify that the system has a certain property, into a new composite Lyapunov function from which the property of interest can be concluded. The results are stated for parameterized families of discrete-time systems that naturally arise when an approximate discrete-time model is used to design a controller for a sampled-data system. We present several applications of our results: (i) a LaSalle criterion for input to state stability (ISS) of discrete-time systems; (ii) constructing ISS Lyapunov functions for time-varying discrete-time cascaded systems; (iii) testing ISS of discrete-time systems using positive semidefinite Lyapunov functions; (iv) observer-based input to state stabilization of discrete-time systems. Our results are exploited in a case study of a two-link manipulator and some simulation results that illustrate advantages of our approach are presented.