Longitudinal Load Alleviation Control and Modeling of a High-Aspect Ratio Wing Flexible Aircraft

Kurzfassung

The reduction of carbon emissions drives future aviation towards more environmentally friendly aircraft design, leading to the demand for new technologies. One crucial technology is the investigation to increase aerodynamic efficiency by reducing induced aerodynamic drag, resulting in lower fuel consumption. This is achieved by increasing the aspect ratio of the wings and using lighter materials, leading to a more flexible structure and a challenging problem due to the coupling between aeroelasticity and flight dynamics. For this reason, active load control is essential to enable high-aspect ratio wings. In this paper, we analyze the load alleviation problem for a very flexible aircraft with high aspect-ratio wings. For longitudinal load control, an autopilot including a base controller for flight dynamics and an optimal load alleviation control function are developed by modifying the performance index to directly penalize the wing root bending moment. The proposed methodology is adaptable to different feedback control laws and suitable for parametric analysis by varying the wing root bending moment weighting. Furthermore, a first order linear time-invariant actuator model with a cut-off frequency of 6 Hz and a time delay of 60 ms by means of a second order Padé approximation in the GLA feedback loop are considered. The control laws are tested in a non linear simulation environment, achieving reductions in wing root bending moment of up to 11.88 %, which is proportional to potential structural mass savings. This framework provides significant improvements for the early design phases of the next generation of more environmentally friendly aircraft.