Actuator and sensor fault detection and isolation for nonlinear systems subject to uncertainty

• Published in: International journal of robust and nonlinear control Vol. 28; no. 6; pp. 1996 - 2013
• Main Authors: Shahnazari, Hadi, Mhaskar, Prashant
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.04.2018
• Subjects: actuator faults; detectability analysis; Fault detection; fault diagnosis; high‐gain observers; Noise measurement; Nonlinear control; Nonlinear systems; sensor faults; Uncertainty
• ISSN: 1049-8923; 1099-1239
• DOI: 10.1002/rnc.3996

Summary This work addresses the problem of simultaneous actuator and sensor fault detection and isolation (FDI) for control affine nonlinear uncertain systems in the absence of measurement noise. The FDI is achieved by using a bank of filters, which utilize a subset of the measurements along with prescribed values of the control actuators to estimate states and compute expected process behavior. Residuals are next defined as the difference between the observed and expected behavior. Detectability conditions are developed, which, upon satisfaction, ensure that each residual remains sensitive to a subset of fault scenarios in the presence of uncertainty. To this end, first the ability of observers in providing bounded estimation error for a generalized class of nonlinear uncertain systems is rigorously established. These bounds allow determining thresholds that account for the impact of uncertainty on each residual. Finally, the ability of the proposed framework to achieve FDI by ensuring a unique residual breaching pattern for each fault scenario is established. The efficacy of the FDI framework subject to uncertainty and measurement noise is illustrated using a chemical reactor example.