H2 and H∞-optimal gust load alleviation for a flexible aircraft

H₂ (LQG), weighted-H₂ and H_∞ techniques are used to establish a nominal performance baseline for the vertical acceleration control of a B-52 aircraft model with flexibilities. The aircraft is assumed to be subjected to severe wind gusts causing undesirable vertical motion. The purpose of the controllers is to reduce the transient peak loads on the airplane caused by the gust. Our designs account for the flexible modes of the aircraft model. We use the Dryden gust power spectral density model to guide the performance specifications and control designs, as well as for time-domain simulations. Motivation for the use of an H_∞ performance specification is given in terms of a new interpretation of the Dryden model. Both weighted-H₂ and H _∞ optimal controllers are shown to reduce dramatically the effect of wind gust on the aircraft vertical acceleration when compared to the regular H₂ controller