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.