Control laws in aeronautics are designed to ensure, above all, good handling qualities. However, during extreme maneuvers, which have to be taken into account for aircraft certification, a number of critical structural load limits cannot be guaranteed by this baseline controller. To avoid some modifications of the control law, a solution consists of judiciously exploiting the redundancy of the control surfaces. The aim of this paper is first to find an optimal strategy of the control surface use, which leaves the initial flight behavior unmodified but alleviates a structural load during a selected maneuver. Model predictive control theory solves this offline control allocation problem under actuator saturation constraints. In addition, an identification procedure is proposed to synthesize a new mixing unit that can reproduce this optimal strategy. This methodology is applied to a flexible transport aircraft to alleviate the bending moment at the external wing during a sudden and strong roll maneuver. Nomenclature G = vector containing a truncated sequence of the discrete signal g; its elements are typically g k G = frequency-domain function or frequency response of G g k = value of the signal g at the sampling time t 0 kT s ; in part III: t 0 is varying; it represents the moment at which the optimization is performed; in part IV: t 0 is equal to 0 M x = bending moment about the x axis at the external wing (between the outer engine and the wing tip) n y , n z = lateral and longitudinal load factors p, r, q = roll, yaw, and pitch rates SPkR = right-wing spoiler no. k SPkL = left-wing spoiler no. k T s = sampling interval z CG = altitude of the center of gravity = angle of attack = sideslip angle = bank angle

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This contribution addresses the control design for the three-spacecraft formation flying interferometry mission Pegase. The operational mode considered is the high-precision nulling phase. The control design has as major objective the minimization of the standard deviation of the controlled outputs, e.g. the optical path difference. The payload performance demands are shown to be fulfilled in spite of sensor and actuator noise. Furthermore, a novel iterative algorithm is proposed, capable of designing decentralized H 2 -suboptimal controllers. These controllers consist of a set of individual closed loops on board the different spacecraft which only use locally available measurements, forces and torques. This approach reduces communication bandwidth and enhances robustness concerning faulty communication links. Finally, the performance loss due to decentralization is investigated.

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