Nonlinear Three-Tank System Fault Detection and Isolation Using Differential Flatness
Rim Rammal, Tudor-Bogdan Airimitoaie, Pierre Melchior, Franck Cazaurang
TL;DR
This work presents a flatness-based fault detection and isolation (FDI) framework for a nonlinear three-tank hydraulic system, with residues derived from flat-output measurements and their derivatives. The authors introduce a residue-sensitivity-aware signature matrix to improve robustness and define detectability and isolability in the flatness context, highlighting the need for independent flat outputs to maximize isolability. Experimentally, they validate the approach on a PI-controlled closed-loop bench, showing that a single flat output yields limited isolability while two independent flat outputs enable full fault isolation via an augmented signature matrix. The study demonstrates the practical viability of differential flatness for FDI in nonlinear hydraulic networks and provides a structured method to enhance fault isolation through output selection and sensitivity analysis.
Abstract
Fault detection and isolation on hydraulic systems are very important to ensure safety and avoid disasters. In this paper, a fault detection and isolation method, based on the flatness property of nonlinear systems, is experimentally applied on the three-tank system, which is considered as a popular prototype of hydraulic systems. Specifically, fault indicators, called residues, are generated using flat output measurements, and for the purpose of fault isolation, a definition of the isolability is introduced. This definition allows the characterization of flat outputs that are useful for fault isolation. A sensitivity analysis is proposed in order to improve the robustness of the method. Multiplicative faults are considered on sensors and actuators.