Flexible aircraft conceptual co-design based on the RCE framework

ifasd2024 Tracking Number 99

In a traditional aircraft design process, the airframe is designed first, followed by synthesizing the control system. This sequential method does not guarantee the best possible closed-loop performance. The goal of the paper is to propose automatic control design methods for flexible aircraft. Such approach enables the inclusion of the control design algorithms into the multidisciplinary design optimization (MDO) of aircraft design. In such an extended MDO framework, called co-design, the sizing, structural dynamics, aerodynamics and the controllers of the aircraft are optimized in one single step. Co-design allows the usage of control technologies early in the conceptual preliminary design stage of aircraft design. A demonstrator aircraft T-Flex serves as a test bed for the conceptual co-design. DLR’s Remote Component Environment (RCE) framework is used as the backbone for the MDO toolchain implementation. The control design algorithms of the co-design considered in the paper are the baseline and the flutter suppression controllers, which require a control oriented aeroservoelastic model. The modeling is done via the bottom-up modelling approach and the resulting control oriented models are given in the linear parameter-varying (LPV) framework. The baseline control system features a classical cascade flight control structure with scheduled control loops to augment the lateral and longitudinal axis of the aircraft. The control loops use scheduled elements of proportional-integral-derivative (PID) controller structures. The flutter controller aims to mitigate the undamped oscillations of the wings that occur if the aircraft is flying beyond the flutter speed. Parametric and dynamic uncertainties are accounted for in the control design. The objective of the design is to minimize the sensitivity function of the closed-loop while limiting the bandwidth of the controller to prevent the excitation of high-frequency dynamics. The effect of the following parameters on the conceptual co-design is investigated: wing sweep angle between 0 and 30 degrees, flutter mass between 0 and 0.4 kg and ply angle between -45 and 45 degrees. It is examined how these parameters affect the flutter modes of the aircraft and the performances of the baseline and flutter suppression controllers and the results can be used for conceptual aircraft design.