State estimation for partially unknown nonlinear systems: a class of integral high gain observers

The classical problem of state estimation for a class of partially unknown nonlinear systems is considered. The proposed observer contains only an integral-type contribution of the measurement error, which provides robustness against noisy measurements and uncertainties. The estimation of the system state variables and the uncertain term is performed simultaneously. A convergent analysis of the proposed estimation methodology is performed. The estimation scheme is applied to a continuously stirred biochemical reactor; numerical experiments illustrate a good observer performance.