Comparative study of three nonlinear observers

Abstract

This report presents a comparison study of performances and characteristics of three advanced state observers, including the high-gain observers, the sliding-mode observers and the extended state observers. These observers were originally proposed to address the dependence of the classical observers, such as the Kalman Filter and the Luenberger Observer, on the accurate mathematical representation of the plant. The results show that, over all, the nonlinear extended state observer is much superior in dealing with dynamic uncertainties, disturbances and sensor noise. Several novel nonlinear gain functions are proposed to address the difficulty in dealing with unknown initial conditions. Simulation results are provided. Keywords: High Gain Observer, Sliding Mode Observer, Nonlinear Extended State Observer.