Sensor fault reconstruction and observability for unknown inputs, with an application to WasteWater Treatment Plants

In this paper, we propose a general methodology for identifying and re-constructing sensor faults on dynamical processes. This methodology is is-sued from the general identification theory developed in the previous papers (Busvelle and Gauthier, 2003, 2004, 2005): In fact, this identification theory provides also a general framework for the problem of “observability with un-known inputs”. Indeed, many problems of fault detection can be formulated as such observability problems, the (eventually additive) faults being just considered as unknown inputs. Our application to “sensor fault detection” for WasteWater Treatment Plants (WWTP) constitutes an ideal academic context to apply the theory: First, in this 3-5 case (3 sensors, 5 states), the theory applies generically and, second, any system is naturally under the “observability canonical form ” required to apply the basic high-gain ob-server from Gauthier and Kupka (1994). A simulation study on the Bleesbrük WWTP is proposed to show the effectiveness of this approach. Keywords