Advantages of using aeroelastic feedback in flexible aircraft control instead of applying notch-filtering

Resumo

© Universal Technology Corporation, 2018.The advent of modern fly-by-wire systems permitted the development of dedicated control law functionalities focused on enhancing aircraft’s performance, increasing safety and reducing pilot workload. However, these control laws use digital sensors to measure aircraft parameters that can be affected by the elastic-body dynamics, such as angle-of-attack, sideslip angle, Euler angles and angular rates. The introduction of notch filtering is a strategy typically used to decouple rigid and elastic-body dynamics, allowing the implementation of control laws that will not harm aircraft’s structural integrity. In this paper, we compare a traditional stability-augmentation system based on notch filtering and feedback of rigid-body states with a more sophisticated system that allows feedback of the aeroelastic modes. For a fair comparison, the same constraints regarding aeroelastic modes attenuation are considered for both control system strategies. The comparison is made by investigating the effects of both stability-augmentation systems control strategies on the handling qualities upon the analysis of frequency domain criteria and by pilot-in-the-loop simulations considering high-gain maneuvers, such as the pitch capture maneuver. Effects of variation of airframe elasticity level are also considered under this scope.

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