TITLE:

ROBUST OUTPUT REGULATION OF NONLINEAR SYSTEMS : AN OVERVIEW (No. 132)

DATE:

Friday, January 19th, 2007

TIME:

3:30 PM

LOCATION:

GMCS 214

SPEAKER:

Sridhar Seshagiri, Department of Electrical Engineering, San Diego State University

ABSTRACT:

The output regulation problem is a central one in control theory, and deals with controlling theoutput of a system so as to achieve asymptotic tracking of prescribed trajectories and/or asymptoticrejection of undesired disturbances. A classical setup in which the problem was posed and successfullyaddressed, in the context of linear, time-invariant and finite dimensional systems, is the one in which theprescribed trajectories and undesired disturbances, referred to as the exogenous signals, are generated byan autonomous system called the exosystem. The nonlinear version of this problem has been extensivelystudied for about two decades now, and continues to be a focus of research in the controls community. Inour talk, we will attempt to give an overview of the nonlinear output regulation problem, covering keyideas such as local, regional, semi-global and global versions of the problem, structurally stable or robustregulation, the regulator equations and internal models. We will also talk briefly about the diverseapplications of the theory to automotive engineering, autonomous helicopter landing, magneticallylevitated systems, left ventricular assists devices, pursuit evasion in urban environments, and so on.
From the systems viewpoint, we will focus on the geometric approach to the solvability of theoutput regulation problem, which is based on the ideas of center manifold theory, controlled invariantattractive manifolds, and immersion. We will also cover more recent developments such as adaptive orself-tuning and nonlinear internal models. From the controls viewpoint, we will focus on issues of stateversus measurement or error-feedback, and different approaches to controller design including passivitytheory, Lyapunov redesign, and sliding mode control. Finally, we will discuss the issue of controllerperformance, and systematic designs for improving the transient performance, for the special class ofminimum-phase input-output linearizable systems. In doing so, we will show how to design PI and PID-like controllers with anti-windup compensation for this class of systems, that recover the steady-stateand transient performance of ideal sliding mode control. Both analytical as well as simulation results willbe presented, using the position control of permanent-magnet stepper motors (PMSMs) as example.

HOST:

Peter Blomgren

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