The celebrated Kalman-Yakubovic/spl caron/-Popov (KYP) lemma establishes the equivalence between a frequency domain inequality (FDI) and a linear matrix inequality, and has played one of the most fundamental roles in systems and control theory. This paper first develops a necessary and sufficient condition for an S-procedure to be lossless, and uses the result to generalize the KYP lemma in two aspects-the frequency range and the class of systems-and to unify various existing versions by a single theorem. In particular, our result covers FDIs in finite frequency intervals for both continuous/discrete-time settings as opposed to the standard infinite frequency range. The class of systems for which FDIs are considered is no longer constrained to be proper, and nonproper transfer functions including polynomials can also be treated. We study implications of this generalization, and develop a proper interface between the basic result and various engineering applications. Specifically, it is shown that our result allows us to solve a certain class of system design problems with multiple specifications on the gain/phase properties in several frequency ranges. The method is illustrated by numerical design examples of digital filters and proportional-integral-derivative controllers.

Generalized KYP lemma: unified frequency domain inequalities with design applications

This paper is concerned with the state estimation and sliding-mode control problems for continuous-time Markovian jump singular systems with unmeasured states. Firstly, a new necessary and sufficient condition is proposed in terms of strict linear matrix inequality (LMI), which guarantees the stochastic admissibility of the unforced Markovian jump singular system. Then, the sliding-mode control problem is considered by designing an integral sliding surface function. An observer is designed to estimate the system states, and a sliding-mode control scheme is synthesized for the reaching motion based on the state estimates. It is shown that the sliding mode in the estimation space can be attained in a finite time. Some conditions for the stochastic admissibility of the overall closed-loop system are derived. Finally, a numerical example is provided to illustrate the effectiveness of the proposed theory.

State Estimation and Sliding-Mode Control of Markovian Jump Singular Systems

This note provides an improved asymptotic stability condition for time-delay systems in terms of a strict linear matrix inequality. Unlike previous methods, the mathematical development avoids bounding certain cross terms which often leads to conservatism. When time-varying norm-bounded uncertainties appear in a delay system, an improved robust delay-dependent stability condition is also given. Examples are provided to demonstrate the reduced conservatism of the proposed conditions.

/pdf/improved-delay-dependent-stability-criteria-for-time-delay-460tdkaev6.pdf

Improved delay-dependent stability criteria for time-delay systems

This paper is concerned with the problem of Hinfin output tracking for network-based control systems. The physical plant and the controller are, respectively, in continuous time and discrete time. By using a sampled-data approach, a new model based on the updating instants of the holder is formulated, and a linear matrix inequality (LMI)-based procedure is proposed for designing state-feedback controllers, which guarantee that the output of the closed-loop networked control system tracks the output of a given reference model well in the Hinfin sense. Both network-induced delays and data packet dropouts have been taken into consideration in the controller design. The network-induced delays are assumed to have both an upper bound and a lower bound, which is more general than those used in the literature. The introduction of the lower bound is shown to be advantageous for reducing conservatism. Moreover, the controller design method is further extended to more general cases, where the system matrices of the physical plant contain parameter uncertainties, represented in either polytopic or norm-bounded frameworks. Finally, an illustrative example is presented to show the usefulness and effectiveness of the proposed Hinfin output tracking design.

Network-Based ${{\cal H}}_{\!\!\!\infty }$ Output Tracking Control

Recent years have witnessed a resurgence of research interests in analysing the stability of time-delay systems. Many results have been reported using a variety of approaches and techniques. However, much of the focus has been laid on the use of the Lyapunov-Krasovskii theory to derive sufficient stability conditions in the form of linear matrix inequalities. The purpose of this article is to survey the recent results developed to analyse the asymptotic stability of time-delay systems. Both delay-independent and delay-dependent results are reported in the article. Special emphases are given to the issues of conservatism of the results and computational complexity. Connections of certain delay-dependent stability results are also discussed.

A survey of linear matrix inequality techniques in stability analysis of delay systems

Considers the problems of robust stability and stabilization for uncertain continuous singular systems with state delay. The parametric uncertainty is assumed to be norm bounded. The purpose of the robust stability problem is to give conditions such that the uncertain singular system is regular, impulse free, and stable for all admissible uncertainties, while the purpose of the robust stabilization is to design a state feedback control law such that the resulting closed-loop system is robustly stable. These problems are solved via the notions of generalized quadratic stability and generalized quadratic stabilization, respectively. Necessary and sufficient conditions for generalized quadratic stability and generalized quadratic stabilization are derived. A strict linear matrix inequality (LMI) design approach is developed. An explicit expression for the desired robust state feedback control law is also given. Finally, a numerical example is provided to demonstrate the application of the proposed method.

/pdf/robust-stability-and-stabilization-for-singular-systems-with-4zvzx7fnc7.pdf

Robust stability and stabilization for singular systems with state delay and parameter uncertainty

http://perso.uclouvain.be/paul.vandooren/publications/GeninSV02.pdf

Real and complex stability radii of polynomial matrices

Positivity and Linear Matrix Inequalities

Given a stabilizable linear system Ex/spl dot/ = Ax + Bu with sE - A regular, we analyze the stability robustness of the closed-loop system (E + BK) = (A + BF)x + v, obtained by proportional and derivative (PD) state feedback u = Fx Kx/spl dot/ + v. Our goal is to maximize the stability radius of the closed-loop system matrix s(E + BK) - (A + BF) over all stabilizing PD state feedback control laws. This problem turns out to be equivalent to a particular H/sup /spl infin//control problem for a generalized state-space system and reduces to a system of matrix inequalities. Under certain conditions the problem actually reduces to an LMI system. We also show how to apply these ideas to higher order dynamical systems.

http://ieeexplore.ieee.org/iel5/7520/20472/00946380.pdf

R. Ştefan

Papers

Robust stability and stabilization for singular systems with state delay and parameter uncertainty

Real and complex stability radii of polynomial matrices

Positivity and Linear Matrix Inequalities

Maximizing the stability radius: an LMI approach

Stability radius and optimal scaling of discrete-time periodic systems