Multi-fault Diagnosis in Three Coupled Tank System using Unknown Input Observer

This paper addresses fault detection and isolation technique for a three coupled tank system using unknown input observers (UIOs). The objective of this paper is to improve isolation properties of the above nonlinear MIMO dynamical system. For the diagnosis of different (actuator and sensor) faults a bank of UIO are designed. Each UIO generates residuals that are insensitive to only one fault, and sensitive to rest of the other faults. For the diagnosis of actuator and sensor faults, assuming that both the actuator faults and the sensor faults do not occur simultaneously. The major advantage of using UIOs is that it makes possible to isolate more than one faulty component at a time. Simulation results are given to verify the effectiveness of proposed work. Results show the proposed scheme is working satisfactorily.