In order to ensure better availability of water resource to different users, we undertook a dependability study of system for drinking water supply. A real case study was done on the water supply network in the city of El Hadjarin Algeria. We started from the site modelling, which provided a calculation of a Hydraulic Criticality Index (HCI) in order to prioritize the importance of pipes in the network. Once the indices were calculated, a modelling procedure of reliability block diagram was applied. The objective was to study and analyse the existing network to measure the water availability problems and try to provide viable solutions. An action on the structural aspect and hardware may be required in order to ensure better availability of water and make the system more reliable. Spatial modelling is also proposed to be able to monitor different parts of the network where problems may occur.

A new approach to build an interval observer for nonlinear uncertain systems is presented in this paper. Nonlinear systems modeled in the Takagi-Sugeno (T-S) form are studied. A T-S proportional observer is first issued by pole-placement and LMI tools. Secondly, time-varying change of coordinates for each dynamic state estimation error is used to design an interval observer. The system state bounds are then directly deduced.

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This paper presents a model-based technique for fault detection and isolation (FDI) of actuators of a benchmark which schematizes a hydraulic process made up of three tanks. Takagi Sugeno's model approach is used for describing the dynamic of the system. In the same way, the fuzzy membership functions used for constructing Takagi and Sugeno's model are combined with local unknown input observers to form robust fuzzy observer. Sufficient conditions for the existence of this fuzzy observer are derived. The stability as well as eigen-value constraints conditions are presented and solved in the LMI framework. For the observer gives a good estimation without amplifying noise and with a convergence faster than the dynamic of the system a eigen-value assignment is necessary. Robust residual signals, generated by these fuzzy observers robust to unknown inputs are dedicated to supervise actuators. These residuals are sensitive to faults acting on one actuator and are also insensitive to faults on the others by considering faults such unknown disturbances. This permits to carry out directly the isolation of the faulty actuator.

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