Aerospace Science and Technology 13 (2009) 374–382 Contents lists available at ScienceDirect Aerospace Science and Technology www.elsevier.com/locate/aescte Active aeroelastic control over a four control surface wing model L. Cavagna a , S. Ricci b,∗ , A. Scotti b a Politecnico di Milano, now at FOI (Swedish Defence Research Agency) Gullfossgatan 6, 164 90 Stockholm, Sweden b Politecnico di Milano, Dipartimento di Ingegneria Aerospaziale, Via La Masa 34, 20156, Milano, Italy article info abstract Article history: Received 17 September 2007 Received in revised form 27 November 2008 Accepted 17 June 2009 Available online 25 August 2009 Keywords: Aeroelastic control Multi surface control Computational aeroelasticity This paper describes the procedure implemented to design, develop and test an aeroelastic control system installed on a forward swept wing of the aeroelastic demonstrator X-DIA. A control method directly based on Nissim aerodynamic energy concept has been chosen. Two different modeling techniques have been adopted for the calculation of generalized aerodynamic forces, such as doublet lattice method and computational fluid dynamics and the obtained results are finally compared. The latter approach, applied to better estimate the control surfaces effectiveness, requires the capability to correctly model the control surface rotation and the grid deformation, usually addressed as non-trivial problems in CFD based aeroelastic analysis. A genetic algorithm optimization technique has been adopted to state and refine all the control gains.  2009 Elsevier Masson SAS. All rights reserved. 1. Introduction The design of control systems requires accurate numerical mod- els and a set of tools that can help engineers to evaluate the dynamic of interest with sufficient accuracy in a very straightfor- ward and concise way. This paper focuses on the realization and optimization of an active control system for improving aeroelas- tic response of a forward swept wing provided of four control surfaces located on leading and trailing edges. The adopted con- trol surface architecture is similar to one already proposed by NASA with Active Flexible Wing (AFW) and Active Aeroelastic Wing (AAW) research programs in [20,21]. Modern jet liner aircraft and, of course, military aircraft, are already provided of a great num- ber of control surfaces, often depicted as redundant, and usually targeted to be useful only for a specific part of flight. The con- trol system here implemented makes no difference between each of these control surfaces, only considering the possible lift force that could be generated. In this way, realization of an aeroelastic control system capable of improving aircraft response turns out to be an overdetermined problem which can be solved by means of optimization techniques. An appropriate formulation of the opti- mization problem, in terms of objective and constraint functions, could guarantee the optimal use of control surfaces so to improve, for example, the gust response or the flutter margin. With such an approach, it is evident that the tools to be adopted in model- * Corresponding author. E-mail addresses: luca.cavagna@foi.se (L. Cavagna), sergio.ricci@polimi.it (S. Ricci), alessandro.scotti@polimi.it (A. Scotti). ing fluid–structure interaction play a leading role in getting to an optimal and efficient control system. The design of the control system is here faced using an ap- proach based on aerodynamic energy, as proposed by Nissim in [16]. Addressing aeroelastic response problem from the energy point of view, regardless of aerodynamic force location [13], pro- vides a very general approach that could be very attractive for the optimization problem to be solved. With this method each control surface contributes at its best in dissipating wing energy and, as a direct consequence, in improving aircraft response with respect to gust response or flutter. A specific test case is analyzed in this paper: the forward swept wing installed on the aeroelastic platform named X-DIA, designed and built at Politecnico di Milano. Because of its unconventional shape, planform and control surface redundancy, the X-DIA rep- resents an excellent testing bench to verify different control de- sign methodologies and logics. In this view, this paper presents the design and optimization of control system by considering and evaluating the combined usage of different tools for modeling fluid–structure interaction. Two different models of the aerody- namic field have been chosen, based on Doublet Lattice Method (DLM) and computational fluid dynamics (CFD). Then, the struc- tural properties of the wing have been reproduced using a simple finite element (FE) model featuring only beams and concentrated masses. Furthermore, an optimization procedure based on a ge- netic algorithm has been chosen to automatize the design and tuning processes of the aeroelastic control system. The following paragraphs will present the complete procedure adopted, starting from the analytical formulation till to simulation results. 1270-9638/$ – see front matter  2009 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ast.2009.06.009