Pitch Rate CAS for PH-LAB via H∞ Loop Shaping
Simulation-Based Development for Future Flight Testing
A. Sabeeayoun (TU Delft - Aerospace Engineering)
Spilios Theodoulis – Mentor (TU Delft - Control & Simulation)
M.M. van Paassen – Graduation committee member (TU Delft - Control & Simulation)
Olaf Stroosma – Graduation committee member (TU Delft - International Research Institute for Simulation, Motion and Navigation)
Alessandro Bombelli – Graduation committee member (TU Delft - Operations & Environment)
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Abstract
Modern flight control systems must not only achieve high performance but also ensure robustness against uncertainties and actuator limitations, particularly in experimental aircraft, where flight validation is a key objective. The PH-LAB, a modified Cessna Citation II operated by TU Delft as a flying laboratory, provides a unique opportunity to validate control design methodologies on a full-size business jet platform. While prior work by Marques et al. 2025 introduced a structured H∞ pitch rate controller for the aircraft using a first-order actuator model, no robust controller has yet been designed and assessed using a realistic actuator model representative of the fly-by-wire system used in the actual aircraft, alongside digital implementation to enable future flight testing. This thesis presents a significant intermediate step toward flight validation by developing and validating three versions of a structured H∞ pitch rate controller: a baseline fully continuous-time design, a modified continuous-time version retuned to account for discretization effects, and a fully discrete-time implementation. All controllers were synthesized within the Loop Shaping Design Procedure framework, using a MATLAB/Simulink model of the aircraft. The proposed design meets all robustness and performance objectives, achieving Level 1 handling qualities while maintaining stability under uncertainties and digital effects. Performance is demonstrated through linear and nonlinear time-domain simulations, gap metric analysis, and evaluation against time-domain criteria, including tracking accuracy. These results confirm that implementing a discretized pitch rate controller using H∞ LSDP with a second-order actuator model guarantees robustness against uncertainties and satisfies the Level 1 handling qualities. Hence, the control architecture is mature enough to proceed to flight testing. Beyond verifying the controller itself, this work contributes toward validating the design methodology in the ultimate setting, flight testing on a full-scale experimental aircraft. Future work will include piloted evaluations, lateral-directional controller extensions, and flight envelope expansion via gain scheduling.
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File under embargo until 25-09-2027