On-line fault detection and isolation using analytical redundancy

In this paper fault detection and isolation schemes using an extended Luenberger observer for non-linear systems and linear fault sensitive filters are presented. The idea is to implement both approaches on the same plant, achieve on-line fault detection and show some practical issues related to on-line fault detection implementation on a real laboratory plant, where for evaluation of residuals and fault isolation an adaptive threshold together with Boolean decision logic is used. FDI methods tested in this paper were performed on a most popular case study, namely the three-tank system, which has in our case an unusual structure as the inflow to the tanks is mounted at the bottom of the tanks and contributes to additional non-linear behaviour. Online data acquisition was realized by local controller using Ethernet communication and OPC interface, and FDI schemes were performed in the Matlab/Simulink environment. The implemented fault detection schemes proved themselves well even when small abrupt changes/faults were generated in the real process.