Controller Optimization in Real Time for a Morphing Wing in a Wind Tunnel A. V. Popov, L. T. Grigorie, R. M. Botez École de Technologie Supérieure, LARCASE, www.larcase.etsmtl.ca , Montréal, Québec, H3C 1K3 Canada ruxandra@gpa.etsmtl.ca Abstract— Wind Tunnel Test results of a real time optimization of a morphing wing in wind tunnel for delaying the transition towards the trailing edge are presented. A morphing rectangular finite aspect ratio wing, having a reference airfoil cross-section, was considered with its upper surface made of a flexible composite material and instrumented with Kulite pressure sensors, and two smart memory alloys actuators. Several wind tunnel tests runs for various Mach numbers, angles of attack and Reynolds numbers were performed in the 6’×9’ wind tunnel at the Institute for Aerospace Research at the National Research Council Canada (IAR/NRC). Unsteady pressure signals were recorded and used as feed back in real time control while the morphing wing was requested to reproduce various optimized airfoils by changing automatically the two actuators strokes. The new optimization method was implemented into the control software code that allowed the morphing wing to adjust its shape to an optimum configuration under the wind tunnel airflow conditions. INTRODUCTION Drag reduction on a wing could be achieved by modifications of the airfoil shape which had an effect in the laminar flow to turbulent flow transition point position, which should move toward the trailing edge of the airfoil wing. The main objective of this concept was to obtain large laminar regions on the wing surface, thus reducing drag over an operating range of flow conditions characterized by Mach numbers, airspeeds and angles of attack [1]. The airborne modification of an aircraft wing airfoil shape could be realized continuously to maintain laminar flow over the wing surface as flight conditions changed. To achieve such a full operating concept, a closed loop control system concept was developed by us to control the flow fluctuations over the wing surface with the Smart Material Actuators [2]. M. Mamou, Y.Mebarki Institute for Aerospace Research, NRC Ottawa, Ontario, K1A 0R6, Canada The wing model had a rectangular plan-form of aspect ratio of 2 and was equipped with a flexible upper surface skin on which shape memory alloys actuators were installed. Two shape memory alloys actuators (SMA) created the displacement of the two control points on the flexible skin in order to optimize the airfoil shapes. As reference airfoil, a laminar airfoil was used; its aerodynamic performance was investigated at IAR-NRC in refs. [3,4], and the optimized airfoils were previously calculated by modifying the reference airfoil for each airflow condition as combinations of angles of attack and Mach numbers such that the transition point position was found to be the nearest as possible to the airfoil trailing edge. Several optimized airfoils were found for different combinations of Mach numbers and angles of attack. The optimized airfoils configurations were stored in the computer memory by means of a database and are selected as needed by the operator or computer in order to be realized by the morphing wing. But this strategy relied on the previously calculated aerodynamical characteristics of the airfoils which usually are determined by use of CFD codes and optimization algorithms. The idea presented in this paper is to implement the same optimization algorithm into the computer controller that will search the optimal configuration with the real system, in real time and in real aerodynamical airflow conditions. EXPERIMENTAL SET-UP A. Mechanical and Electrical Control System The concept of this morphing wing consisted in a rectangular wing model (chord c = 0.5 m and span b = 2.1 m) incorporating two parts. One fixed part was built in aluminum by the IAR-NRC team and sustained the resistance forces acting during wind tunnel tests. The other part was flexible consisted in its flexible skin installed on the wing upper surface and was designed and manufactured at ETS. The flexible skin was required to change its shape through two