Structural identifiability of non linear systems: an overview

Structural identifiability is a fundamental prerequisite for parametric model identification. It concerns uniqueness of the parametric structure given a dynamical model and a set of input/output experimental dates. Proving structural identifiability propriety for non linear systems is considered until now a very difficult problem. Many approaches have been proposed in the literature but there isn't a generic method suitable for any non linear case. The main concern of this paper is to present an overview of different approaches used to test structural identifiability for non linear systems. Important aspects and difficulties of identifiability analysis is reviewed and illustrated by an example of an active sludge process characterized by rational polynomial non linearities and specified initial conditions.