State Observer Design and Application for Lipschitz Nonlinear Systems

This paper discusses the state observer design and application for a class of nonlinear systems. The nonlinearity item of this class of systems is Lipschitz globally. A sufficient condition on the stability matrix that ensures asymptotic stability of the observer is presented, creatively using Lyapunov method and solution of the Lyapunov equation. It is shown that the eigenvalues have to be located sufficiently far out into the left half-plane, and the eigenvectors also have to be sufficiently well-conditioned for ensuring asymptotic stability. For the purpose of observer design, a systematic computational algorithm gradient-based is presented to obtain the observer gain matrix so as to achieve the objective of asymptotic stability. The developed theory is used successfully in the design of an observer for a flexible joint robotic system, which verifies the validity of the theory.