## 3 Aerospace Engineering Applications
### Aplication to Wing Morphing  
One area with great potential to significantly improve aircraft performance is the structural morphing of the aircraft, especially the shape morphing wing. The classifications of the shape morphing wing are presented in Figure 5.  
[PERSON] et al. designed a reference shape based on a full-scale wing of a regional transport aircraft and proposed a flap architecture for a variable camber trailing edge [82]. The compliance rib is based on a truss structure in which some members are SMA-based active rods. The structural performance was estimated using FE analysis. [PERSON] et al. proposed a group of SMA actuators [83]. The proposed actuator includes a flexible extrados, a transmission system including the slider and the crank, a compression bias spring, and an SMA active element. The performance of the proposed actuator system was evaluated via wind tunnel test. [PERSON] and Mabe reported a review paper about SMA-based morphing aero-structures developed in the past decade [84]. The review paper reported on five large-scale SMA-based technology programs initiated by the Boeing Company: deployable rotor blade aerodynamics, variable geometry chevrons, smart inlets, reconfigurable rotor  
Figure 4: Applications of SMA in airplane. Figure 5: Classification for shape morphing wing and its geometrical parameters. blades, and variable area fan nozzles. For the morphing of the laminar wing, [PERSON] et al. numerically investigated the optimal design of an active extrados structure [85]. They identified two key design parameters. The first is the number of plies in the flexible extrados composite laminate and the second is the number of actuators. To achieve a balance for the compromise between rigidity and flexibility of the active extrados structure, aerodynamic and mechanical performance criteria were considered simultaneously. The proposed conceptual design of the morphing laminar wing is presented in Figure 6. [PERSON] et al. presented the modeling and testing of an SMA actuator-based morphing wing in open-loop control architecture [86]. The proposed flexible skin was designed to deform the shape of the airfoil through deformation of two operating points in order to create an airfoil shape optimized for the theoretical fluid flow conditions. The SMA actuator was activated by a power supply unit and controlled using the self-tuning fuzzy controller. [PERSON] et al. also presented closed-loop control configuration and the displacements of the SMA actuator were automatically determined as a function of the pressure obtained from the wing top surface [87]. [PERSON] et al. proposed two morphing wings that can be deformed to a specific target shape using an SMA actuator [88]. In the first design, the straight wing is slid and deformed into a curved shape, and, in the second design, the wing is bent in the lateral direction. The prototypes exhibited good and smooth movement under the applied loads. To evaluate the effect of the morphing wing on the lift and drag coefficients, the parametric aerodynamic analysis was carried out. One area with great potential to significantly improve aircraft performance is the structural morphing of aircraft, especially the shape morphing wing. [PERSON] et al. developed a controller by combining on-off, bi-positional, and PI controllers for an actuation control of a morphing actuation mechanism by considering two heating and cooling phases of the interconnected SMA wire actuators [89]. The proposed controller acts as a switch between the cooling and heating stages in the case of an output current of 0 A. The control inputs by the PI controller in the heating stage were optimally determined using integral and surface minimum error criteria. [PERSON] et al. also reported the numerical simulation and experimental validation results for the control system in a morphing wing application [90]. [PERSON] et al. designed a hybrid fuzzy-PID controller and demonstrated its control performance under subsonic wind tunnel conditions [91, 92].