An Unusual Structure for a Feedforward Gust Load Alleviation Controller

Abstract

This paper presents an unusual feedforward controller structure that allows to take allocation constraints into account which can be expressed in the timefrequency or time-scale domains. This novel controller structure was motivated by the design of a feedforward controller for airplane gust and turbulence load alleviation based on Doppler LIDAR measurements. As shown by the application that has motivated this development, some strongly nonlinear constraints can be guaranteed by the design of the structure. The developed structure is not restricted to the considered application and could be applied successfully to many other feedforward control problems with some prior knowledge of the upcoming disturbances or references.

Performance Enhancement of Gust Load Alleviation Systems for Flexible Aircraft using H∞Optimal Control with Preview

“…This paper focuses rather on the question of the optimal exploitation of the previewed disturbance, and does not tackle the question of how to obtain this information in practice. This preview control approach proposed here can be seen as a direct extension of [17][18][19][20] in which the controllers were sub-optimally manually tuned based on the designer's understanding of flight mechanics and aeroelasticity.…”

“…Consequently, the orientation of DLR's research activities on gust alleviation moved from the design of gust alleviation systems that are based on classical sensors (such as in the OLGA or the LARS systems) to the investigation of the potential performance enhancement that would result from the use of more advanced/futuristic sensors. The previous work that had been performed in these directions, especially during the AWIATOR project, led in particular to the GCS [11] and the GLA [12][13][14] systems, and to also consider the use of Doppler LIDAR sensors for determination of wind ahead of the aircraft for load alleviation purposes [11][12][13][14][15][16][17][18][19][20].…”

Gust load alleviation for a long-range aircraft with and without anticipation

“…The Tikhonov terms can be used to smooth the reconstructed wind profile but this also leads to a deformation of the overall shape of the reconstructed wind profile. The chosen approach combines a relatively low smoothing and a wavelet-based signal shrinkage in the feedforward controller itself [8,10]. This latter process allows to focus on the large-scale variations of the wind profile, which are the ones leading to the peak loads.…”

“…Section 2.7 presents the general concept underlying the feedforward controller that exploits this reconstructed wind information. The implementation details for the feedforward controller can be found in [8].…”

“…This concept was successfully implemented using the so-called Fast Orthogonal Wavelet Transform (FOWT), which is one of many time-frequency/scale techniques that could be used in order to obtain the aforementioned behav-ior. The reader is referred to [8] for the implementation details and a detailed discussion on the structure of this feedforward controller.…”