To gain more insight into the performance of state-of-the-art Static Output Feedback (SOF) controller synthesis methods for H∞-control, quantitative comparisons are made between Lyapunov methods and well-known established non-smooth optimization methods, i.e. Hinfstruct and HIFOO. Three methods were deemed to be the most promising to compete and were bundled into one toolbox named SOFHi. The algorithms were extended to incorporate structured SOF and a variant of SOFHi was proposed to significantly improve upon the computational efficiency of the original implementation. Extensive comparisons show that SOFHi was able to compete with the established non-smooth methods and even able to significantly outperform one of them. Lastly, an elaborate flight control benchmark example is given to showcase the effectiveness of the algorithms, which involves the design of a gain-scheduled normal acceleration Control Augmentation System (CAS) for a highly maneuverable fighter aircraft.

This research evaluates various linear quadratic control techniques, with a particular focus on loop transfer recovery methods, to enhance the safety and robustness of flight control systems. It aims to address the limitations of classical control strategies in managing complex, multivariable systems by implementing advanced recovery mechanisms. The study utilizes a simulation model of the Cessna Citation PH-LAB aircraft to explore the effectiveness of linear quadratic regulator (LQR), linear quadratic Gaussian (LQG), and loop transfer recovery (LTR) control methods. It examines their time and frequency-domain characteristics, robustness against uncertainties, and performance in tracking normal acceleration commands. The research identifies the strengths and weaknesses of each method, contributing to the development of more reliable and efficient control systems for aviation.

This study demonstrates an effective systematic control design procedure by applying H∞ Loop-Shaping with a structured controller on an agile aerospace vehicle with a focus on automation. The gain-scheduled implementation is additionally described and tested with non-linear simulations, including a realistic moving point-hit scenario with guidance. The imposed robustness and performance requirements are met for most linear design points and for the non-linear simulations. The resulting autopilot design procedure is deemed effective in both the design procedure and implementation. It is subject to certain recommendations for improvement and extension.

This research develops a robust control approach for hypersonic vehicles (HV) using modern H-infinity techniques. Focusing initially on subsonic conditions, a non-linear GHAME HV model was created in MATLAB and Simulink, incorporating parametric uncertainty in aerodynamic coefficients. Linear short-period longitudinal dynamics were extracted at multiple operating points. A fixed-structure controller was synthesized using multi-objective H-infinity mixed-sensitivity techniques, addressing pitch moment coefficient uncertainty. The design was extended to account for variations in Mach number, altitude, and fuel mass. The control system was checked for robustness requirements and tested on the non-linear model.

This thesis presents the development process of an aircraft control law. The control law is designed using a two-degree-of-freedom (2DoF) structured H∞ loop-shaping approach. This method allows the reuse of controller structures required by certification procedures while directly including handling qualities and robust stability requirements in the optimization process. This strategy is employed to develop a Rate Command and Attitude Hold (RCAH) demand system aimed at satisfying longitudinal handling qualities. First, the stability of the open-loop model and its compliance with the handling qualities guidelines are evaluated. Then, the control law is designed. In this step, a detailed description of the design specifications and how to specify them in the context of H∞ control is given. Subsequently, the controller parameters are optimized to satisfy the design specifications and a closed-loop analysis is performed. Finally, a simulator flight testing campaign is conducted to experimentally validate the designed control law. It is shown that the aircraft equipped with the RCAH system achieves better handling quality ratings (HQRs) and more favorable pilot feedback, providing a substantial improvement over the bare airframe.