Nonlinear implicit on-line observer : application to the estimation in binary distillation columns

The current demand for more complex models has initiated a shift away from statespace models towards models described by both dynamic and algebraic equations, so-called implicit systems. These models arise as the natural product of real processes. In this paper, we consider design of observers for a class of implicit systems. The proposed observer combines the dynamic Newton-Raphson algorithm as well as a high gain method. It is described by differential equations and it can be initialized outside the algebraic constraints. The main results of the paper include conditions that ensure the exponential convergence of the observer error. Design methodology is presented and the performance of the proposed observer illustrated using an application to a binary distillation column model.