Considering active gust load alleviation (GLA) during aircraft design offers great potential for structural weight savings. The effectiveness of a GLA control system strongly depends on the layout of available control surfaces, which is investigated in this article. For the purpose of wing load reduction, a concurrent optimization of controller gains and aileron geometry parameters is carried out. To that end, an efficient update routine for the nonlinear model of a large-scale flexible aircraft with unsteady aerodynamics is presented. Compared to a GLA system using the original aileron configuration, a 9% performance improvement is achieved. Furthermore, a trade-off study is carried out which enables a target-oriented balancing between individual load channels. The significant influence of aileron size and position on overall GLA performance is demonstrated and hence a consideration during the preliminary aircraft design process is recommended.
In order to determine a guaranteed upper bound for worst case 1-cosine gust loads of flexible aircrafts, the usage of the worst case energy-to-peak gain of linear parameter-varying (LPV) systems has been recently proposed. A limitation of this approach is that it cannot deal with nonlinearities. This paper uses integral quadratic constraints (IQCs) to circumvent this restriction and to consider the saturation of a gust loads alleviation system. Based on the dissipation inequality framework, a linear matrix inequality constraint which bounds the worst case energy-to-peak gain of saturated LPV systems is given. In order to reduce the conservatism, an iterative procedure to refine local IQCs is proposed. The conservatism of this approach is analyzed at the example of a two-dimensional thin airfoil in combination with a saturated gust loads alleviation system. Copyright Notice The author has retained copyright of the publication and releases it to the public according to the terms of the DLR elib archive.
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