Stability Analysis Of Time-varying Systems Research Articles

Finite-time and fixed-time stability analysis for time-varying systems: A dual approach

In this paper we present a new dual approach to investigating the stability of the system of two nonautonomous ODE with the right-hand side being only Lebesgue measurable with respect to time t. We define a new dual Lapunov function S which depends on three variables, and we give sufficient conditions for finite and fixed-time stability for the system using a dual Hamilton-Jacobi inequality and taking advantage of a class of functions M and MB. This method allows simultaneous investigation of the finite and fixed-time stability of the primary and the dual equation. We give some examples to illustrate the results obtained. As an application of this dual approach, we define the region of attraction and illustrate with an example.

Stability Analysis for Time-Varying Systems With Asynchronous Sampling Using Contractivity Approach

We provide new sufficient conditions for a generalized exponential input-to-state stability condition to hold. Our proofs use innovative trajectory based contractivity and cooperative systems arguments. Another key ingredient is a new variant of Halanay's inequality, which differs from prior Halanay inequalities because of its use of sampling. Our sufficient conditions allow arbitrarily long intervals between some consecutive sampling times, provided the intervals between consecutive sampling times are frequently small enough. This removes a significant limitation of prior results that relied on versions of Halanay's inequality that did not contain sampling. Unlike standard stability conditions, the upper bounds for the norm of the current state in our less restrictive exponential input-to-state stability conclusions have suprema of disturbances over intervals that include earlier times than the initial times. We apply this letter to a broad class of time-varying continuous time systems with sampling.

Stability Analysis for Time-Varying Systems With Delay Using Linear Lyapunov Functionals and a Positive Systems Approach

We prove stability of time-varying systems with delays, using linear Lyapunov functionals and positive systems, and we provide robustness of the stability with respect to multiplicative uncertainty in the vector fields. We allow cases where the delay may be unknown, and where the vector fields defining the systems are not necessarily bounded. We illustrate our work using a chain of integrators and other examples.

Homogeneity Based Uniform Stability Analysis for Time-Varying Systems

The uniform stability notion for a class of nonlinear time-varying systems is studied using the homogeneity framework. It is assumed that the system is weighted homogeneous considering the time variable as a constant parameter, then several conditions of uniform stability for such a class of systems are formulated. The results are applied to the problem of adaptive estimation for a linear system.

Stability analysis for time-varying systems via quadratic constraints

In this paper, we introduce the concept of “quadratic constraint” (QC) to deal with various stability problems for infinite dimensional linear discrete time-varying (LTV) systems. First, we derive a necessary and sufficient condition for the close-loop stability based on quadratic constraints (QCs). An equivalent condition of this stability criterion presents the relationship between the stabilization of each finite dimensional truncation system and that of the whole system. Moreover, applying this stability criterion and the complete finiteness of the nest algebra, we show that the plant is stabilizable if and only if it has a single strong representation. Finally, we use QCs to give a necessary and sufficient condition for the robust stabilization of connected uncertainty set defined by gap metric.

An approximate stability analysis of nonlinear systems described by Universal Learning Networks

Stability is one of the most important subjects in control systems. As for the stability of nonlinear dynamical systems, Lyapunov's direct method and linearized stability analysis method have been widely used. But, it is generally recognized that finding an appropriate Lyapunov function is fairly difficult especially for the nonlinear dynamical systems, and also it is not so easy for the linearized stability analysis to find the locally asymptotically stable region. Therefore, it is crucial and highly motivated to develop a new stability analysis method, which is easy to use and can easily study the locally asymptotically stable region at least approximately, if not exactly. On the other hand, as for the calculation of the higher order derivative, Universal Learning Networks (ULNs) are equipped with a systematic mechanism that calculates their first and second order derivatives exactly. So, in this paper, an approximate stability analysis method based on @h approximation is proposed in order to overcome the above problems and its application to a nonlinear dynamical control system is discussed. The proposed method studies the stability of the original trajectory by investigating whether the perturbed trajectory can approach the original trajectory or not. The above investigation is carried out approximately by using the higher order derivatives of ULNs. In summarizing the proposed method, firstly, the absolute values of the first order derivatives of any nodes of the trajectory with respect to any initial disturbances are calculated by using ULNs. If they approach zero at time infinity, then the trajectory is locally asymptotically stable. This is an alternative linearized stability analysis method for nonlinear trajectories without calculating Jacobians directly. In the method, the stability analysis of time-varying systems with multi-branches having any sample delays is possible, because the systems are modeled by ULNs. Secondly, the locally asymptotically stable region, where asymptotical stability is secured approximately, is obtained by finding the area where the first order terms of Taylor expansion are dominant compared to the second order terms with @h approximation assuming that the higher order terms more than the third order are negligibly small in the area. Simulations of an inverted pendulum balancing system are carried out. From the results of the simulations, it is clarified that the stability of the inverted pendulum control system is easily analyzed by the proposed method in terms of studying the locally asymptotically stable region.

Integral Characterizations of Set UGAS of Differential Inclusions and Applications

We present an integral characterization of uniform asymptotic stability for differential equations and inclusions. This characterization is used to establish new results on concluding uniform global asymptotic stability when uniform global stability is already known and uniform convergence must be established by additional arguments. We show the utility of our result by generalizing Matrosov's Theorem on the use of a differentiable auxiliary function. Also, we present an application to the stability analysis of time-varying systems.

Robust stability analysis of time-varying systems using time-varying quadratic forms

We consider the robust stability of time-varying linear systems subject to structured time-varying uncertainty. We provide an alternate proof of the result that robust stability holds if and only if a scaled small-gain condition holds asymptotically. The new proof employs an extension of the so-called S-procedure losslessness theorem to time-varying quadratic forms which is of independent interest.