Ali Saberi

Bio: Ali Saberi is an academic researcher from Washington State University. The author has contributed to research in topics: Linear system & Synchronization. The author has an hindex of 51, co-authored 448 publications receiving 10959 citations. Previous affiliations of Ali Saberi include Northeastern University & University College of Engineering.

Control of linear systems with saturating actuators

Abstract: This paper deals with the design of linear systems with saturating actuators where the actuator limitations have to be incorporated a priori into control design. The authors take a semiglobal approach to solve some of the central control problems for such systems. These problems include stabilization, input-additive disturbance rejection, and robust stabilization in the presence of matched nonlinear uncertainties. The authors develop further the semiglobal design technology which was initiated in their earlier work (Lin and Saberi, 1995) and utilize it to deal with these control problems.

Special coordinate basis for multivariable linear systems—finite and infinite zero structure, squaring down and decoupling

Abstract: A special coordinate basis for multivariable linear systems is introduced here. Several fundamental properties of linear systems regarding controllability (stabiliza-bility), observability (detectability), invariant zeros, decoupling zeros, infinite zero structure, effect of feedback on zero structure, squaring down, diagonal and triangular decoupling etc. can be directly displayed in terms of the special coordinate basis. Moreover, connections between the special coordinate basis and the important invariant subspaces of the geometric theory of linear systems are established.

Control of Linear Systems with Regulation and Input Constraints

Abstract: From the Publisher: The issue of tracking a desired reference signal in the presence of external disturbances is a classical control problem that resides at the core of control engineering. This is referred to as the output regulation problem. In this book the output regulation problem is examined in depth. New, highly significant dimensions are added to the problem and all pertinent topics associated with it are discussed. These topics include: Analysis and design of controllers for the output regulation problem subject to physical constraints on actuators such as amplitude and rate saturation. Incorporating transient performance requirements into output regulation problem formulation, thus creating an optimal framework for the output regulation problem. Uniting the output regulation problem formulation with other performance requirements of modern control theory such as H2 and Hinfinity optimal and suboptimal performance criteria. Opening up a novel framework of output regulation problem formulation in order to enlarge the class of signals dealt with whilst at the same time adding new possibilities. This book is designed to meet the needs of a variety of readers including practising control engineers, graduate students, and researchers in control engineering.

Global stabilization of partially linear composite systems

Abstract: A linear stabilizable, nonlinear asymptotically stable, cascade system is globally stabilizable by smooth dynamic state feedback if (a) the linear subsystem is right invertible and weakly minimum phase, and, (b) the only linear variables entering the nonlinear subsystem are the output and the zero dynamics corresponding to this output. Both of these conditions are coordinate-free and there is freedom of choice for the linear output variable. This result generalizes several earlier sufficient conditions for stabilizability. Moreover, the weak minimum-phase condition for the linear subsystem cannot be relaxed unless a growth restriction is imposed on the nonlinear subsystem.

A linear matrix inequality approach to H∞ control

Abstract: The continuous- and discrete-time H∞ control problems are solved via elementary manipulations on linear matrix inequalities (LMI). Two interesting new features emerge through this approach: solvability conditions valid for both regular and singular problems, and an LMI-based parametrization of all H∞-suboptimal controllers, including reduced-order controllers. The solvability conditions involve Riccati inequalities rather than the usual indefinite Riccati equations. Alternatively, these conditions can be expressed as a system of three LMIs. Efficient convex optimization techniques are available to solve this system. Moreover, its solutions parametrize the set of H∞ controllers and bear important connections with the controller order and the closed-loop Lyapunov functions. Thanks to such connections, the LMI-based characterization of H∞ controllers opens new perspectives for the refinement of H∞ design. Applications to cancellation-free design and controller order reduction are discussed and illustrated by examples.

Information consensus in multivehicle cooperative control

Abstract: The purpose of this article is to provide a tutorial overview of information consensus in multivehicle cooperative control. Theoretical results regarding consensus-seeking under both time invariant and dynamically changing communication topologies are summarized. Several specific applications of consensus algorithms to multivehicle coordination are described

Stochastic Differential Equations

Abstract: We explore in this chapter questions of existence and uniqueness for solutions to stochastic differential equations and offer a study of their properties. This endeavor is really a study of diffusion processes. Loosely speaking, the term diffusion is attributed to a Markov process which has continuous sample paths and can be characterized in terms of its infinitesimal generator.