Robust Nonpeaking Algebraic Observers

In this paper we propose a new robust scheme of nonpeaking nonlinear observers. The observation strategy is issued from differential algebra where the unmeasured states are given as outputs of a time-varying linear differentiator that guarantees robustness against measurement errors. We show that for a certain initial condition, the n-dimensional differentiator does not exhibit the peaking phenomenon, generally encountered in high-gain observer design. A discrete-time version is included to deal with sampled signals. The developed nonlinear observer reproduces the unmeasured states whatever the form of the nonlinear system that meets the algebraic observability conditions. Key-Words: Nonlinear observers; Differentiation; Lyapunov theory; Time-varying systems; Discrete-time systems.