Stability Analysis of Interconnected Systems

We address the stability analysis of composite hybrid dynamical feedback systems of the type depicted in Fig. 1, consisting of a block (usually the plant) which is described by an operator L and of a finite-dimensional block described by a system of ordinary differential equations (usually the controller). We establish results for the well-posedness, attractivity, asymptotic stability, uniform boundedness, asymptotic stability in the large, and exponential stability in the large for such systems. The hypotheses of these results are phrased in terms of the I/O properties of L and in terms of the Lyapunov stability properties of the subsystem described by the indicated ordinary differential equations. The applicability of our results is demonstrated by means of general specific examples (involving C 0 -semigroups, partial differential equations, or integral equations which determine L ).

This paper is concerned with the stability analysis of interconnected systems composed of locally and globally exponentially stable subsystems. Sufficient conditions for not necessarily asymptotic and exponentially asymptotic stability are derived. The problem of estimating the stability region of the composite system is also considered.

Optimal Control of Stochastic Systems

Some sufficient conditions for exponential stability of linear neutral functional differential equations

On the stability of certain systems under resonance conditions

In two recent papers, Brayton and Tong developed some significant results which are the basis of a constructive approach in the stability analysis of dynamical systems. Although their algorithm is powerful, it taxes the capabilities of most modern computers when the dimension of a system is high or even when the dimension is moderate in size. In this paper we remove these difficulties to a certain extent by generalizing the work of Brayton and Tong to interconnected dynamical systems. In our approach, the analysis of complex dynamical systems (which may be of high dimension) is accomplished in terms of the qualitative properties of the free subsystems and the interconnections of such systems.

Introduction to the Series. Preface. Overview. Progress in Stability Theory by the First Approximation. Invariant Foliations for Caratheodory Type Differential Equations. On Exponential Asymptotic Stability for Functional Differential Equations with Causal Operators. Lyapunov Problems on Stability. Contemporary Development of Lyapunov's Ideas of Direct Method. Vector Lyapunov Function: Nonlinear, Time-Varying, Ordinary and Functional Differential Equations. Some Results on Total Stability Properties for Singular Systems. Stability Theory of Voltera Difference Equations. Consistent Lyapunov Methodology for Exponential Stability: PCUP Approach. Advances in Stability Theory of Lyapunov: Old and New. Matrix Lyapunov Functions and Stability Analysis of Dynamical Systems. Stability Theorems in Impulsive Functional Differential Equations with Infinite Delay. The Asymptotic Behavior of Solutions of Stochastic Functional Differential Equations with Finite Delays by Lyapunov-Razumikhin Method. A Non-standard Approach to the Study of the Dynamic System Stability. Stability of Solutions. A Survey of Starzhinskii's Works on Stability of Periodic Motions and Nonlinear Oscillations. Implications of the Stability of an Orbit for Its Omega Limit Set. Some Concepts of Periodic Motions and Stability Originated by Analysis of Homogenous Systems. Stability Criteria for Periodic Solutions of Autonomous Hamiltonian Systems. Selected Applications. Stability in Models of Agriculture-Industry-Environment. Bifurcations of Periodic Solutions of the Three Body Problem. Complex Mechanical Systems: Steady State Motions, Oscillations, Stability. Progress in Stability of Impulsive Systems with Applications to Population Growth Models. Contemporary Development of Lyapunov's Ideas of Direct Method. Stability of Solutions to Periodic Differential Systems. Selected Applications.

Operator-valued stochastic differential equations in the context of Kurzweil-like equations

In this paper we consider periodic functional differential and integral equations. Massera proved that the existence of a bounded solution implies the existence of a periodic solution for linear (inhomogeneous) ordinary differential equations. Chow proved a similar result for linear functional differential equations with finite delay. We give a new proof for Chow's result that works for linear functional differential equations with infinite delay and also for integral equations. We also give examples that do not satisfy uniform boundedness or uniform ultimate boundedness, the conditions frequently used to prove that there is a periodic solution.

Time delay is a common phenomenon in robotic systems due to computational requirements and communication properties between or within high-level and low-level controllers as well as the physical constraints of the actuator and sensor. It is widely believed that delays are harmful for robotic systems in terms of stability and performance; however, we propose a different view that the time delay of the system may in some cases benefit system stability and performance. Therefore, in this paper, we discuss the influences of the displacement-feedback delay (single delay) and both displacement and velocity feedback delays (double delays) on robotic actuator systems by using the cluster treatment of characteristic roots (CTCR) methodology. Hence, we can ascertain the exact stability interval for single-delay systems and the rigorous stability region for double-delay systems. The influences of controller gains and the filtering frequency on the stability of the system are discussed. Based on the stability information coupled with the dominant root distribution, we propose one nonconventional rule which suggests increasing time delay to certain time windows to obtain the optimal system performance. The computation results are also verified on an actuator testbed.

In Chap. 17, n-th-order functional differential equations are considered. In order to create a concept of nonoscillation for functional differential equations which will be an analogue of nonoscillation theory for ordinary differential equations, we define a nonoscillation interval for the n-th-order homogeneous functional differential equation as interval, where each nontrivial solution can have at most n−1 zeros, counting every zero with its multiplicity. The study of many classical questions of the qualitative theory of n-th-order equations such as existence and uniqueness of solutions of the interpolation boundary value problems, positivity or corresponding regular behavior of their Green’s functions, maximum principles and stability, was considered in the general framework based on the notion of nonoscillation intervals of corresponding linear functional differential equations. It is demonstrated that if the Wronskian of the fundamental system is not equal to zero at the initial point of the interval, then the nonoscillation interval exists for functional differential equations; this is true for a particular case of the n-th-order functional differential equations with Volterra operators (delay equations). For second-order functional differential equations, nonvanishing Wronskian is equivalent to the Sturm theorem on separation of zeros (between two adjacent zeros of any nontrivial solution there is a zero of every other solution). The analogue of the classical Mammana theorem, establishing necessary and sufficient nonoscillation conditions through nonvanishing normal chains of the Wronskians, is proven for n-th-order functional differential equations.

In this note, we deal with the stability and stabilization problems for nonlinear quadratic discrete-time periodic systems. By using the quadratic Lyapunov function, and a so called periodic invariant set, delay-independent sufficient conditions for local stability and local stabilization for nonlinear quadratic discrete-time periodic systems are derived in terms of linear matrix inequalities (LMIs). Based on these sufficient conditions, iterative linear matrix inequality algorithms are proposed for maximizing the stability regions of the systems. Finally, two examples are given to illustrate the effectiveness of the methods presented in this paper.

Semigroups of translations and functional differential equations

Stochastic differential delay equations and their asymptotic behavior have received much attention in recent years (see [1, 2, 5, 7–10, 12, 13] and the references therein), since these retarded problems often appear in physics, biology, engineering, etc. The delays can enter into the formulations in very different ways, e.g., as a constant or variable delay or as a distributed one; some of them can even appear in the model at the same time. However, it is possible to consider all of them under a unified formulation by using appropriate differential functional equations. In this sense, we will carry out our analysis in a functional framework that will cover a wide variety of situations containing finite delays. There exists a vast literature concerning pathwise exponential stability of parabolic stochastic evolution equations (with and without delays). We mention here, among many others, [4, 11–13] and the references therein. In the case without hereditary characteristics, the problem of the asymptotic stability of delay stochastic partial differential equations of second order in time has been considered by Curtain in [6], where one can find sufficient conditions for the exponential stability of the expected energy of the system, as well as for the exponential decay of the sample paths, when the main operator generates a strongly continuous contraction semigroup. In this paper, we shall develop the theory in a variational framework for nonlinear operators in general. We are going to consider the following model:

Stability analysis of interconnected systems by means of aggregatre subsystem models