On the estimation of robust stability regions for nonlinear systems with saturation

• Main Author: Coutinho,Daniel F.
• Publication Date: 2004
• Other Authors: Pagano,Daniel J., Trofino,Alexandre
• Format: Article
• Language: eng
• Source: Sba: Controle & Automação Sociedade Brasileira de Automatica
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-17592004000300003
• topic: Nonlinear systems; stability region; uncertainty; convex optimization; saturation

This paper addresses the problem of determining robust stability regions for a class of nonlinear systems with time-invariant uncertainties subject to actuator saturation. The unforced nonlinear system is represented by differential-algebraic equations where the system matrices are allowed to be rational functions of the state and uncertain parameters, and the saturation nonlinearity is modelled by a sector bound condition. For this class of systems, local stability conditions in terms of linear matrix inequalities are derived based on polynomial Lyapunov functions in which the Lyapunov matrix is a quadratic function of the state and uncertain parameters. To estimate a robust stability region is considered the largest level surface of the Lyapunov function belonging to a given polytopic region of state. A numerical example is used to demonstrate the approach.