Automated Tuning of a Baseline Flight Control System with Maneuver Load Alleviation for an Energy-Efficient Passenger Airplane

ifasd2024 Tracking Number 191

The aeroelastic design process of modern aircraft concepts involves the airframe sizing based on sizing loads, which are identified through simulation of selected load cases, e.g., gust encounters or maneuvers. Alleviation of the sizing loads offers potential for lightweight construction and thus an improved aircraft efficiency. Load alleviation concepts are investigated in the SE²A cluster employing an aeroelastic simulation framework for an energy-efficient passenger aircraft [1]. Generally, for the inboard portion of the wing, sizing loads are defined by the gust and maneuver loads. An active Gust Load Alleviation (GLA) system has been developed in [2]. To further reduce the sizing loads, the maneuver loads need to be lowered as well. For this purpose, an active Maneuver Load Alleviation (MLA) function is applied here. It mitigates the bending moment at the wing root by shifting the lift distribution along the wingspan towards the symmetric plane. Modern passenger aircraft are typically equipped with a flight control system including a flight control law. The dynamic loads depend on said law, which is not yet considered in [1]. In order to simulate the dynamic load cases more accurately, a representative flight control law is designed and added to the loop. On this basis, the effectiveness of the MLA function is investigated. Decreased sizing loads allow for a redesign of the airframe, which alters the aircrafts flight dynamics, in turn necessitating an adjustment of the flight control law. The interdependence implies that the Multidisciplinary Optimization (MDO) loop of both the flight control law and the structure must be iterated, which is only feasible if their design is fully automated. Hence, this work presents a practical approach to the multi-objective tuning of flight control laws for the automated design of a representative C* Control Augmentation System (CAS) including an active MLA function for a flexible aircraft. A comprehensive closed-loop performance analysis based on a linear model is conducted to validate the control design approach, regarding robustness and aeroelastic stability among others. Finally, the controller is evaluated for the nonlinear aeroelastic flight dynamics model [1].