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Stability Regions (stability + regions)
Selected AbstractsMethods for estimating stability regions with applications to power systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2007H. Xin Abstract A specialized method for constructing a hyper-ellipse that resides inside the stability regions of a class of nonlinear autonomous systems such as electric power systems is provided. This method is further generalized to estimate the stability region of a fairly general class of high dimension nonlinear autonomous systems. Applications of the introduced results to power system transient stability analysis are described, together with numerical examples. Copyright © 2006 John Wiley & Sons, Ltd. [source] Stability and accuracy analysis of a discrete model reference adaptive controller without and with time delayINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2010Oreste S. Bursi Abstract Adaptive control techniques can be applied to dynamical systems whose parameters are unknown. We propose a technique based on control and numerical analysis approaches to the study of the stability and accuracy of adaptive control algorithms affected by time delay. In particular, we consider the adaptive minimal control synthesis (MCS) algorithm applied to linear time-invariant plants, due to which, the whole controlled system generated from state and control equations discretized by the zero-order-hold (ZOH) sampling is nonlinear. Hence, we propose two linearization procedures for it: the first is via what we term as physical insight and the second is via Taylor series expansion. The physical insight scheme results in useful methods for a priori selection of the controller parameters and of the discrete-time step. As there is an inherent sampling delay in the process, a fixed one-step delay in the discrete-time MCS controller is introduced. This results in a reduction of both the absolute stability regions and the controller performance. Owing to the shortcomings of ZOH sampling in coping with high-frequency disturbances, a linearly implicit L-stable integrator is also used within a two degree-of-freedom controlled system. The effectiveness of the methodology is confirmed both by simulations and by experimental tests. Copyright © 2009 John Wiley & Sons, Ltd. [source] Delay-dependent anti-windup strategy for linear systems with saturating inputs and delayed outputsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2004S. Tarbouriech Abstract This paper addresses the problem of the determination of stability regions for linear systems with delayed outputs and subject to input saturation, through anti-windup strategies. A method for synthesizing anti-windup gains aiming at maximizing a region of admissible states, for which the closed-loop asymptotic stability and the given controlled output constraints are respected, is proposed. Based on the modelling of the closed-loop system resulting from the controller plus the anti-windup loop as a linear time-delay system with a dead-zone nonlinearity, constructive delay-dependent stability conditions are formulated by using both quadratic and Lure Lyapunov,Krasovskii functionals. Numerical procedures based on the solution of some convex optimization problems with LMI constraints are proposed for computing the anti-windup gain that leads to the maximization of an associated stability region. The effectiveness of the proposed technique is illustrated by some numerical examples. Copyright © 2004 John Wiley & Sons, Ltd. [source] About one application of the general method of Lyapunov functionals constructionINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 9 2003V. Kolmanovskii Abstract Some peculiarities of the general method of Lyapunov functionals construction proposed and developed by the authors during last decade for stability investigation of stochastic hereditary systems are considered. It is shown, in particular, that using this method one can construct a sequence of extended stability regions for stochastic difference Volterra equations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Enhanced stability regions for model predictive control of nonlinear process systemsAICHE JOURNAL, Issue 6 2008Maaz Mahmood Abstract The problem of predictive control of nonlinear process systems subject to input constraints is considered. The key idea in the proposed approach is to use control-law independent characterization of the process dynamics subject to constraints via model predicative controllers to expand on the set of initial conditions for which closed,loop stability can be achieved. An application of this idea is presented to the case of linear process systems for which characterizations of the null controllable region (the set of initial conditions from where closed,loop stability can be achieved subject to input constraints) are available, but not practically implementable control laws that achieve stability from the entire null controllable region. A predictive controller is designed that achieves closed,loop stability for every initial condition in the null controllable region. For nonlinear process systems, while the characterization of the null controllable region remains an open problem, the set of initial conditions for which a (given) Lyapunov function can be made to decay is analytically computed. Constraints are formulated requiring the process to evolve within the region from where continued decay of the Lyapunov function value is achievable and incorporated in the predictive control design, thereby expanding on the set of initial conditions from where closed,loop stability can be achieved. The proposed method is illustrated using a chemical reactor example, and the robustness with respect to parametric uncertainty and disturbances demonstrated via application to a styrene polymerization process. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Fault-tolerant control of process systems using communication networksAICHE JOURNAL, Issue 6 2005Nael H. El-Farra Abstract A methodology for the design of fault-tolerant control systems for chemical plants with distributed interconnected processing units is presented. Bringing together tools from Lyapunov-based nonlinear control and hybrid systems theory, the approach is based on a hierarchical architecture that integrates lower-level feedback control of the individual units with upper-level logic-based supervisory control over communication networks. The local control system for each unit consists of a family of control configurations for each of which a stabilizing feedback controller is designed and the stability region is explicitly characterized. The actuators and sensors of each configuration are connected, via a local communication network, to a local supervisor that orchestrates switching between the constituent configurations, on the basis of the stability regions, in the event of failures. The local supervisors communicate, through a plant-wide communication network, with a plant supervisor responsible for monitoring the different units and coordinating their responses in a way that minimizes the propagation of failure effects. The communication logic is designed to ensure efficient transmission of information between units, while also respecting the inherent limitations in network resources by minimizing unnecessary network usage and accounting explicitly for the effects of possible delays due to fault-detection, control computations, network communication and actuator activation. The proposed approach provides explicit guidelines for managing the various interplays between the coupled tasks of feedback control, fault-tolerance and communication. The efficacy of the proposed approach is demonstrated through chemical process examples. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Mass peak shape improvement of a quadrupole mass filter when operating with a rectangular wave power supplyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Chan Luo Numeric experiments were performed to study the first and second stability regions and find the optimal configurations of a quadrupole mass filter constructed of circular quadrupole rods with a rectangular wave power supply. The ion transmission contours were calculated using ion trajectory simulations. For the first stability region, the optimal rod set configuration and the ratio r/r0 is 1.110,1.115; for the second stability region, it is 1.128,1.130. Low-frequency direct current (DC) modulation with the parameters of m,=,0.04,0.16 and ,,=,,/,,=,1/8,1/14 improves the mass peak shape of the circular rod quadrupole mass filter at the optimal r/r0 ratio of 1.130. The amplitude modulation does not improve mass peak shape. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||