Optimal Manoeuvres with Very Flexible Wings

The single shooting method is used identify optimal manoeuvres in the lateral dynamics of partially-supported wings of very low stiffness. The aim is to identify actuation strategies in the design of aircraft manoeuvres in which large wing deflections can substantially modify the vehicle structural and aerodynamic features. Preliminary studies are presented for a representative high-altitude long-endurance aircraft wing in hinged configuration. Nonlinear effects due to large deflections are captured coupling a geometrically exact beam model with an unsteady vortex lattice method for the aerodynamics. The optimal control problem is solved via a gradient-based algorithm. When lowering the wing stiffness, the nonlinearities connected to the system — such as the fore-shortening effect due to large bending deflections — increase the wing lateral stability but at the same time they also reduce aileron authority. The single-shooting optimisation is shown to capture these features and to provide satisfactory results, not only when refining a predetermined actuation law but also when designing it from zero.

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