Aircraft efficiency has over the last decades increasingly improved by a large-scale usage of lightweight composite materials in high aspect ratio airframes. A tedious property of this advancement is that the increased structural flexibility produces unfavourable interactions between aerodynamics and structural dynamics. Existing literature has already shown the advantages of active feedback control to alleviate these adverse coupling effects. However, limited attention has been paid to the practical implementation of these flight control systems. This thesis, therefore, presents a robust control synthesis method for obtaining a real-time implementable flight control system for a high aspect ratio and flexible aircraft.

The presented controller synthesis method combines techniques from Incremental Nonlinear Dynamic Inversion (INDI) with linear H∞-norm minimization to achieve simultaneous reference tracking performance and structural motion alleviation. With focusing on acquiring a real-time implementable flight controller, this work emphasizes the importance of taking hardware events such as sensor noise and time delays into account. The goal of this thesis is, therefore, threefold. Firstly, the limitation of INDI control regarding its applicability to flexible aircraft is addressed. Secondly, the INDI-H∞ synthesis formulation is derived and verified using simulations performed on a full-scale SB-10 glider model. Thirdly, the INDI controller is implemented on a real 1:3 scaled Diana-2 demonstrator to compare it against a similarly tuned PID controller in flight. Tracking accuracy and structural motion alleviation are tested on a doublet reference signal for pitch angle. The simulations show that the INDI-H∞ controller outperforms the conventional INDI both in responsiveness and robustness performance. While not affecting tracking accuracy, the INDI-H∞ controller can reduce the oscillations in pitch angle by 6.4% and the elevator control input by 5,9%. Furthermore, the INDI controller’s real-time capability is verified in a developed hardware-in-the-loop simulation and validated through conducted ground tests.

In this report the latest and final preliminary design for the Ultimate Personal Airplane is presented. After having chosen the initial configuration during the mid-term phase of the project, a more detailed design has been made, based upon four aircraft aspects: aerodynamics, structure, stability & control and performance. Also, the design as it is now was prepared for further modifications.