Damage-tolerant Control System Design for Propulsion-controlled Aircraft

This thesis presents a damage-tolerant flight control system design for propulsion-controlled aircraft (PCA). PCA refers to an emergency piloting strategy that flight crews use throttle modulation only to achieve the attitude control of aircraft in case of conventional flight control system failures. PCA also refers to a conceptual or experimental aircraft that is installed with such automated thrust-only control system. When an aircraft undergoes structural damage to its airframe, lifting or control surfaces which cause conventional control system failures, PCA is adopted as an alternative control approach to stabilize the aircraft. However, the control of the damaged aircraft poses complications in stability recovering as unmodeled uncertainties and perturbed dynamics have significant impact on flight dynamics. Therefore, the PCA flight control system should have a high level of robustness against such model uncertainties, aerodynamics parameter deviations, and model perturbations. This thesis presents the study of robust PCA control system design using H infinity-based robust control method. The developed controllers are tested through both linear and nonlinear simulations. A comprehensive evaluation is performed for several different emergency scenarios. The results demonstrate the advantages of the newly-designed robust flight control architecture over the existing optimal controller in dealing with model deviations due to structural damage.MAS