Robust Fault-Tolerant Control for aircraft systems

The need to design controllers that guarantee both stability and performance upon the occurrence of faults has been an active area of research. To address this problem, in this thesis we present different methodologies to design robust controllers that guarantee both stability and robustness for actuator faults and uncertainties. In the first part of this thesis, we introduce the classical uncertainty formulation using Linear Fractional Transformation (LFT) and describe LFT’s special cases-norm bounded and convex polytopic uncertainty descriptions. Practical methods to formulate these uncertainty structures are described. In the same spirit, formulation of faults and their modeling for robust control system design is provided. In the second part of this thesis, we demonstrate the application of a Luenberger observer for fast Fault Diagnosis and Isolation (FDI). We describe the methodology to design a robust optimal control for actuator faults and present controller reconfiguration mechanism based on switching for the design of Fault Tolerant Control (FTC). System with both norm bounded uncertainties and actuator faults is formulated and an analytic method to find a robust stabilizing and guaranteed cost reliable controllers are also mentioned. To the end, we implement designed linear controllers in Boeing 747 (B747) nonlinear system. We also define and evaluate potential problems that arise in switching based FTC and their effect on the closed loop nonlinear system. Robustness of linear controllers in nonlinear B747 was evaluated using excessive Monte Carlo simulation and results are presented.