This thesis presents a robust, signal-based mixed-sensitivity H-Infinity controller specifically designed for the flare phase of automatic landings. A critical literature review highlights the shortcomings of conventional gain-scheduled and nonlinear approaches, motivating a multi-objective H-Infinity formulation that treats flare as a stringent mixed-sensitivity problem. Since touchdown occurs in a rapidly changing aerodynamic environment, the controller must deliver tight regulation of vertical speed and pitch attitude while tolerating ground effect, parameter variations and wind disturbances.

A reduced three-state longitudinal model, extracted from a 16-state benchmark and trimmed at 5 m height, captures the most critical seconds before touchdown for controller synthesis. In systune, eleven hard frequency-domain objectives sculpt the principal sensitivity functions and more. Five static feedback gains and a first-order feed-forward filter are tuned simultaneously, achieving 7 dB / 43 deg robust stability margins.

Frequency-domain checks and extensive nonlinear simulations, including a large-scale Monte-Carlo campaign, confirm consistent performance: the probability of exceeding a 0.914 m/s sink-rate is just 0.0029 %, demonstrating precise vertical-speed control across wide operating envelopes. These results show the synthesized controller significantly enhances safety margins by maintaining stability, reducing touchdown dispersion, and fortifying against model and environmental uncertainties. Thus, this research contributes valuable insights toward enhancing the robustness and reliability of future automated landing systems.

This thesis is on the assessment of handling qualities for a robust controller, previously designed using H∞ techniques for a longitudinal model of the Bo-105. A piloted simulator flight test was conducted in which a set of tasks was flown. These tasks included configuration of stick sensitivity, pitch and altitude tracking tasks, flown at different flight conditions to show robustness, as well as a bob-up and acceleration-deceleration task. The resulting handling quality rating showed that the controller, designed for a theoretical rating of level 1, achieved between level 1 and level 2 handling qualities between the tasks. Non-controller factors, such as stick force, missing cueing and performance limits, were commented on by the pilots to have an effect on the rating. Anti-windup methods, clamping and back-calculation, were used to improve controller response, and reduce oscillations observed during testing.

Agile aerospace vehicles present demanding requirements for flight control systems, due to fast dynamics, large flight envelopes, and the possibility of actuator saturation. Nonlinearities caused by the saturations, especially when not accounted for during control design, can hinder vehicle performance and stability. This thesis presents a robust control design procedure with anti-windup augmentation, applied to the case of an agile aerospace vehicle. The model includes linear airframe dynamics and a second-order nonlinear actuator. A baseline controller is synthesized utilizing the signal-based closed-loop shaping design method to obtain good performance and robustness metrics in the linear domain. A co-design procedure of control gains and weighting filters is employed to optimize the synthesis procedure. Design of an anti-windup augmentation based on the rate saturation signal is then carried out to address the performance degradation of a constrained system. Three distinct anti-windup schemes are analyzed, ranging from classical to modern frameworks. A comparative analysis of the proposed compensators is provided by evaluating the L2 gain and simulating a flight scenario under a nonlinear actuator with multiple saturations. The effectiveness of all anti-windup schemes in stabilizing the vehicle under saturations and improving its performance is demonstrated.

Nonlinear Dynamic Inversion (NDI) control techniques provide a conceptually simple and modular control framework, making it an attractive technique for designing flight control laws with shorter design cycles. However, its lack of inherent robustness guarantees shifts the burden of the design from the synthesis to the analysis part. Conversely, H-infinity Loop-Shaping provides controllers with robust stability guarantees. This work proposes a novel framework leveraging the H-infinity Loop-Shaping Design Procedure to optimize a structured linear variant of Incremental Nonlinear Dynamic Inversion (INDI) control, a Hybrid IDI controller. The Hybrid IDI controller consists of a blend between classical model-based DI and sensor-based IDI. The proposed methodology is validated through the design of a pitch-rate controller for NASA's X-29 experimental aircraft. Results demonstrate that the approach achieves robustness guarantees comparable to standard full-order H-infinity controllers while maintaining the simplicity and modular architecture of NDI-like structures, thereby combining the advantages of both techniques.

As the aviation industry faces growing environmental and societal pressures, novel concepts such as the Flying-V emerge. Nevertheless, its unconventional configuration poses unique challenges in terms of stability and control, highlighting the pressing need for advanced control systems development. A gap in the literature arises concerning the lack of system robustness in the presence of uncertainties and the absence of robust controllers designed for the aircraft. Hence, the current study aims to increase the maturity of the flight control system of the Flying-V concept by implementing a C* longitudinal controller, while guaranteeing robustness stability and performance against uncertainty, adequate performance in the presence of disturbances and measurement noise, and compliance with Level 1 handling qualities. The Flying-V model is implemented in MATLAB/Simulink which served as the foundation for the controllers synthesis. Three designs are developed, which include a continuous time, a modified continuous time, and a modified continuous time multi-modeling controllers. These are conducted within the standard and signal-based H-infinity mixed sensitivity frameworks. Extensive analysis of the controllers is performed in terms of stability assessments, linear and nonlinear time domain simulations, and uncertainty sensitivity. Results demonstrate that the feedback of a combined signal demand such as the C* parameter provides, for a single input multiple-output system, a balanced disturbance rejection at the plant outputs. Conclusions are drawn in terms of the feedback controller structure, highlighting that high gain is necessary at low frequencies for disturbance rejection and roll-off at high frequencies allows control signal reduction and measurement noise attenuation. Moreover, taking into consideration the discretization effects of the flight computer in the design phase improves considerably the stability margins of the controllers. Lastly, it is verified that the proposed controller structures which are designed in the linear domain perform satisfactorily in the nonlinear simulation model and comply with the requirements defined. The multi-modeling controller proved successful in terms of robustness and performance across the flight envelope. Hence, we conclude that implementing this H-infinity optimization process for the design is a promising and viable method to guarantee robustness against uncertainties, disturbances, and measurement noise, as well as compliance with Level 1 HQ. The present work naturally paves the way for recommendations for future work. Some of these recommendations include the extension to lateral-directional control laws, gain-scheduling to guarantee the requirements across the flight envelope, maturity of the aerodynamic data, and pilot assessments of the handling qualities.

The rapid expansion of the e-grocery market has led to significant challenges in last-mile delivery, par- ticularly in managing heterogeneous fleets, accommodating multiple capacity constraints, and adhering to strict time windows. This paper introduces TOET (Tailored Optimisation for E-grocery Transport), a novel framework that addresses these issues through advanced metaheuristic techniques, dynamic hyperparameter tuning, and specialized arrival time calculations. Benchmark experiments on real-world dispatch plans demonstrate that while TOET variants substantially reduce runtime and drive time, the benchmark VROOM algorithm still excels at minimizing the number of routes, revealing a trade-off between drive time and fleet utilization. Overall, TOET shows promise for enhancing operational efficiency and sustainability in e-grocery logistics. Future work will refine arrival time strategies, improve scalability, and conduct an economic and environmental impact analysis of the trade-off between drive duration and route consolidation.

This thesis investigates the use of H-infinity Open Loop Shaping (OLS) for designing Thrust Vector Control (TVC) systems during the atmospheric ascent of flexible launch vehicles (LVs). The research has two main goals. The first goal is to assess whether H-infinity OLS can produce rigid body controllers for launch vehicles with comparable or superior robustness, stability, and performance to controllers designed with H-infinity Closed Loop Shaping (CLS), while also reducing design complexity and time. The second goal is to explore an integrated H-infinity OLS approach that tunes both the rigid body controller and the bending filter simultaneously, simplifying the traditional separate design process.
Results demonstrate that H-infinity OLS and H-infinity CLS yield controllers with identical performance, robustness, and stability when applied to design controllers with the same order and structure. However, H-infinity OLS significantly simplifies the design process by avoiding the manipulation of multiple transfer functions, offering higher reproducibility between flight points, and automatically ensuring robustness at both the plant input and output. Although these benefits come at the cost of converting requirements into open loop specifications and setting loop shaping weighting filters to meet the specifications, both challenges have been addressed and simplified in this thesis.
The thesis also extends the rigid body H-infinity OLS design process into an integrated methodology that simultaneously tunes both the rigid body controller and the bending filter, achieving identical results to the traditional separate design approach while reducing overall design time and complexity.
This research demonstrates that H-infinity OLS provides a robust framework for simplifying the design of TVC systems for launch vehicles, without compromising performance and robustness. Additionally, the integrated H-infinity OLS methodology for tuning both the rigid body controller and bending filter effectively streamlines the design process while achieving identical results to the traditional separate approach. These findings validate H-infinity OLS as a viable alternative to H-infinity CLS and introduce a more efficient methodology for designing both the rigid body controller and the bending filter for TVC control systems in launch vehicles.

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.

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.

In recent years, quadrotors have emerged as versatile aerial vehicles, serving both recreational and critical industrial purposes in fields such as surveillance, search and rescue, agriculture, and transportation. However, ensuring their reliability and safety in the presence of operational faults or disturbances remains a significant challenge. This research aims to address these concerns by developing a robust controller that integrates Incremental Nonlinear Dynamic Inversion (INDI) with H-infinity loop shaping design process (LSDP), resulting in enhanced disturbance rejection and improved robustness to model uncertainty. A nonlinear aerodynamic model, based on flight test data, is used to enhance the fidelity of the quadrotor’s motion equations. The proposed controller is tested and compared with a traditional PD controller. Simulations of attitude control were conducted under different compensators to evaluate the impact of various robust control strategies, particularly in terms of disturbance rejection when combined with the INDI implementation in a 6-DOF nonlinear quadrotor simulator. Results demonstrate the superior disturbance rejection capabilities of the robust controlled system, highlighting the effectiveness of the proposed control strategy in improving performance and reliability under uncertain conditions.

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 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.