This paper presents a smallgain theorem for networks composed of a countably infinite number of finitedimensional subsystems. At this time, many of the later uses of lyapunovs work could hardly have been foreseen. A dynamical system in a state of equilibrium is said to be stable. A smooth converse lyapunov theorem for robust stability. Lyapunov stability theory provides a means of stabilizing unstable nonlinear systems using feedback control. Many famous mathematicians, physicists, and astronomers worked on axiomatizing the concepts of stability. Lecture linear quadratic lyapunov theory the lyapunov equation lyapunov stability conditions the lyapunov operator and integral evaluating quadratic integrals analysis of are discretetime results linearization theorem 1. A wikipedia page gives a general idea about the lyapunov stability. Named after the russian mathematician aleksandr mikhailovich lyapunov, lyapunov functions also called the lyapunovs second method for stability are important to stability theory of dynamical systems and control.
On 12 october 1892 by the modern calendar alexandr mikhailovich lyapunov defended his doctoral thesis the general problem of the stability of motion at moscow university. A detailed post on the lyapunov stability criteria will be uploaded soon. In other words, a system has to be in a stable state before it can be asymptotically stable which means. Pdf a lyapunovbased smallgain theorem for infinite networks. Lyapunovs stability theory100 years on 277 central limit theorem and other deep investigations in areas of mechanics and mathematical analysis. In the theory of ordinary differential equations odes, lyapunov functions are scalar functions that may be used to prove the stability of an equilibrium of an ode.
Until now, the theory of lyapunov stability is still the main theoretical basis of almost all systemcontroller design chen, 1984. Here we introduce a theorem which can be viewed as a dual to lyapunov s result. Failure of a lyapunov function candidate to satisfy the conditions for stability or asymptotic stability does not mean that the equilibrium point is not stable or asymptotically stable. It follows from the theorem that the existence of a lower semicontinuous lyapunov pair v,w with v everywhere. This and related equations are named after the russian mathematician. This does not imply lyapunov stability at the origin, however, so it cannot characterize global asymptotic controllability. And were going to throw in our equations of motion, and attitude, and rotation and everything. In this example we demonstrate the necessary steps required in applying the lyapunov. Lyapunov stability theory an overview sciencedirect topics. Lyapunov stability of equilibrium may be discussed by the lyapunov theory in which the stability can be proven without defining the initial state of system. Here we introduce a theorem which can be viewed as a dual to lyapunovs result. Anand pillay september 29, 2003 1 introduction and preliminaries the aim of this course and these notes is to present an exposition of the basics of stability theory, stable group theory, and geometric stability theory. Lyapunov functions and feedback in nonlinear control.
Lyapunov was a pioneer in successful endeavoring to develop the global approach to the analysis of the stability of nonlinear dynamical systems by. Lyapunov direct method is the most effective method for studying nonlinear and timevarying systems and is a basic method for stability analysis and control law desgin. Structured and simultaneous lyapunov functions for system. Pdf on application of lyapunov and yoshizawas theorems. R be a continuously di erentiable function such that v0 0, x 0.
Lyapunov stability lyapunovs stability theorem theorem 4. Stability is one of the properties of solutions of any differential systems. A matrix a is a stability matrix or hurwitz matrix, that is, re. A brief history of lyapunovs life and tragic death is given, and followed by a section highlighting the important ideas in his thesis of 1892. First, we can study stability of an equilibrium using linearization of 1 around this equilibrium. Assuming that each subsystem is exponentially inputtostate stable. Stability is a classical issue in dynamical system theory. The first method usually requires the analytical solution of the differential equation. Lyapunov stability theory was come out of lyapunov, a russian mathematician in 1892, and came from his doctoral dissertation. A lyapunov function for an autonomous dynamical system. When the jacobian matrix of a dynamical system at equilibrium consists of the eigenvalues with negative real parts this equilibrium is asymptotically stable. Lyapunov function theorem for local asymptotic stability with respect to closed sets. A function v satisfying the hypotheses of this theorem is called a lyapunov function for the. We take a close look at lyapunov stability for lti systems and discuss how to relate chapter 4s linearization theorem to lyapunov stability through lyapunovs indirect method.
In the classical lyapunov stability theory, we assume that the ode in consideration has a smooth at. It is p ossible to ha v e stabilit y in ly apuno without ha ving asymptotic stabilit y, in whic h case w e refer to the equilibrium p oin t as mar ginal ly stable. There are two lyapunov methods for stability analysis. Lyapunovs second theorem is a standard tool for stability analysis of ordinary differential equations. Lyapunov was a pioneer in successful endeavoring to develop the global approach to the analysis of the stability of nonlinear dynamical systems by comparison with the widely spread local method of linearizing them about points of equilibrium. Lyapunov s second theorem is a standard tool for stability analysis of ordinary differential equations. Lyapunov stability is named after aleksandr mikhailovich lyapunov, a russian mathematician who defended the thesis the general problem of stability of motion at kharkov university in 1892. Lyapunovs theory for characterizing and studying the stability of equilibrium points is presented for timeinvariant and timevarying systems modeled by ordinary differential equations. It does not, however, give a prescription for determining the lyapunov function. Pdf on application of lyapunov and yoshizawas theorems on. Yao 3 for autonomous systems, when wx in the above theorem is only positive semidefinite, asymptotic stability may still be obtained by applying the following simplified version of lasalles theorem. Suppose that for a given system there exists a lyapunov function which also satisfies the stronger third condition 0 dv v dt stability theory math 414 spring 2003. Lyapunov functions and lyapunovs stability theorem duration. In control theory, the discrete lyapunov equation is of the form.
The lyapunov equation occurs in many branches of control theory, such as stability analysis and optimal control. A problem, which attracted a great deal of early interest was the problem of stability of the solar system, generalized under the title the nbody stability problem. The proposed smallgain criterion for the stability analysis of the network the spectral radius of the gain operator is less than one can b e check ed in a computationally e. Lecture 12 basic lyapunov theory stanford university. One the major stability technique for non linear dynamic system is called lyapunov. Subsequent applications of these ideas in the control. Lyapunov stability the stability of solutions to odes was.
Lyapunov stability an overview sciencedirect topics. The study of the stability of dynamical systems has a very rich history. One of the most widely adopted stability concepts is lyapunov stability, which plays important roles in sys tem and control theory and in the analysis of engineering systems. I will assume knowledge of my autumn 2002 model theory lecture notes 1.
This and related equations are named after the russian mathematician aleksandr lyapunov. And were talking, if it is continuous this function and there exists in neighborhood, such that for any states, that we are arguing local stability here with lyapunov. Lyapunov s second or direct method provides tools for studying asymp totic stability properties of an equilibrium point of a dynamical system or systems of dif ferential equations. R2 1 we have two methods to get insight about the structure of the phase portrait. An interesting aspect of lyapunov theory for lti systems is that the existence. Then the origin is a globally asymptotically stable equilibrium of x0 fx. Some of these will be described in later sections of this paper.
D r be a continuously differentiable function, such that v0 0 and vx 0 in d. It only means that such stability property cannot be established by using this lyapunov function. The idea is that if one can select a suitable lyapunov function and force it to decrease along the trajectories of the system, the resulting system will converge to its equilibrium. Stability in the sense of lyapunov theequilibriumpoint. This theory still dominates modern notions of stability, and provides the foundation upon which alternative notions of. Pdf a lyapunovbased smallgain theorem for infinite. The following theorem is a direct application of the standard discretetime lyapunov stability theorem for general dynamical systems to the dynamical system 4. The conditions in the theorem are summarized in table 4. Global lyapunov stability and lasalles invariance principle.
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