Flight Control Law Design for Gust Load Alleviation of Flexible Aircraft using Extended Gust Modeling

Abstract

In the field of aircraft design, enhancing aircraft efficiency can be achieved by reducing its weight. Gust load alleviation is considered as an important tool to accomplish this goal. This study aims to design a control law for gust load alleviation of a flexible aircraft, based on a generic commercial aircraft model provided by the German Aerospace Center. A linear full-order state-space controller is designed based on H∞ optimal control. The control law design uses an accelerometer on the wing tip and control the outboard ailerons to alleviate wing root bending moments, while considering actuator capabilities and limitations. The controller’s load reduction performance is evaluated by simulating aircraft response to different vertical discrete gusts from the European Certification pecification CS-25, and the closed-loop robustness is assessed by considering the worst-case combination of system uncertainties. This study also investigates the relationship between load reduction performance and actuator deflection rate limits. It has been demonstrated that the deflection rate limit is a crucial factor in load reduction performance.