Morphing Wing Technology Research Articles

Design of a transonic wing with an adaptive morphing trailing edge via aerostructural optimization

Novel aircraft configurations and technologies like adaptive morphing trailing edges offer the potential to improve the fuel efficiency of commercial transport aircraft. To accurately quantify the benefits of morphing wing technology for commercial transport aircraft, high-fidelity design optimization that considers both aerodynamic and structural design with a large number of design variables is required. To address this need, we use a high fidelity aerostructural model that enables the detailed optimization of wing shape and sizing using hundreds of design variables. We perform a number of multipoint aerostructural optimizations to demonstrate the performance benefits offered by morphing technology and identify how those benefits are enabled. In a comparison of optimizations considering seven flight conditions, the addition of a morphing trailing edge device along the aft 40% of the wing can reduce cruise fuel burn by more than 5%. A large portion of fuel burn reduction due to morphing trailing edges results from a significant reduction in structural weight, enabled by adaptive maneuver load alleviation. We also show that a smaller morphing device along the aft 30% of the wing produces nearly as much fuel burn reduction as the larger morphing device, and that morphing technology is particularly effective for high aspect ratio wings.

Effect of design parameters on the mass of a variable-span morphing wing based on finite element structural analysis and optimization

In the past years, the development of morphing wing technologies has received a great deal of interest from the scientific community. These technologies potentially enable an increase in aircraft efficiency by changing the wing shape, thus allowing the aircraft to fly near its optimal performance point at different flight conditions. However, these technologies often present an undesired mass increase due to their inherent complexity. Therefore, the aim of the current work is to ascertain the influence of geometrical and inertial parameters on the structural mass of a Variable-span Wing (VSW). The structural mass prediction is based on a parametric study. A minimum mass optimization problem with stiffness and strength constraints is implemented and solved, being the design variables structural thicknesses and widths, using a parametric Finite Element Model (FEM) of the wing. The study is done for a conventional fixed wing and the VSW, which are then combined to ascertain the VSW mass increment, i.e., the mass penalization of the adopted morphing concept. Polynomials are found to produce good approximations of the wing mass. The effects of the various VSW design parameters in the structural mass are discussed. On one hand, it was found that the span and chord have the highest impact in the wing mass. On the other hand, the VSW to fixed wing mass ratio proved that the influence of span variation ratio in the wing mass is not trivial. It is found that the mass increase does not grow proportionally with span variation ratio increase and that for each combination of span and chord, exists a span variation ratio that minimizes the mass penalty. In the future, the developed polynomials could be used to create a mass prediction model to aid the design of morphing wings during the conceptual design phase.

Unsteady aerodynamic characteristics of a morphing wing

Purpose The purpose of this paper is to investigate the unsteady aerodynamic characteristics in the deflection process of a morphing wing with flexible trailing edge, which is based on time-accurate solutions. The dynamic effect of deflection process on the aerodynamics of morphing wing was studied. Design/methodology/approach The computational fluid dynamic method and dynamic mesh combined with user-defined functions were used to simulate the continuous morphing of the flexible trailing edge. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection were studied first. Then, the unsteady aerodynamic characteristics of the morphing wing were investigated as the trailing edge deflects at different rates. Findings The numerical results show that the transient lift coefficient in the deflection process is higher than that of the static case one in large angle of attack. The larger the deflection frequency is, the higher the transient lift coefficient will become. However, the situations are contrary in a small angle of attack. The periodic morphing of the trailing edge with small amplitude and high frequency can increase the lift coefficient after the stall angle. Practical implications The investigation can afford accurate aerodynamic information for the design of aircraft with the morphing wing technology, which has significant advantages in aerodynamic efficiency and control performance. Originality/value The dynamic effects of the deflection process of the morphing trailing edge on aerodynamics were studied. Furthermore, time-accurate solutions can fully explore the unsteady aerodynamics and pressure distribution of the morphing wing.

Aero-Structural Evaluation of Morphing Control Surface Using Corrugated Panels

Morphing wing technology is anticipated as a way to improve efficiency over a wider range of flight conditions, but it is difficult to realize morphing because there are two conflicting demands, i.e. stiffness for aerodynamic forces and flexibility for morphing. Super-anisotropy of the corrugated panel is a solution to satisfy those demands. This paper focuses on applying camber morphing to vertical plane. Firstly, optimal deformation of airfoil for morphing control surfaces is defined by conducting airfoil analysis. For realizing optimal deformation, deformation analysis of corrugated panels is conducted and evaluated by using high flexible 2-D beam equations.

Analysis of UAS-S4 Éhecatl aerodynamic performance improvement using several configurations of a morphing wing technology

ABSTRACTThe paper presents the results of the aerodynamic optimisation of an Unmanned Aerial System's wing using a morphing approach. The shape deformation of the wing is achieved by placing actuator lines at several positions along its span. For each flight condition, the optimal displacements are found by using a combination of the new Artificial Bee Colony algorithm and a classical gradient-based search routine. The wing aerodynamic characteristics are calculated with an efficient nonlinear lifting line method coupled with a two-dimensional viscous flow solver. The optimisations are performed at angles of attack below the maximum lift angle, with the aim of improving the Hydra Technologies UAS-S4 wing lift-to-drag ratio. Several configurations of the morphing wing are proposed, each with a different number of actuation lines, and the improvements obtained by these configurations are analysed and compared.

English

As part of a morphing wing technology project, the flutter analysis of two finite element models and the experimental results of a morphing wing demonstrator equipped with aileron are presented. The finite element models are representing a wing section situated at the tip of the wing; the first model corresponds to a traditional aluminium upper surface skin of constant thickness and the second model corresponds to a composite optimized upper surface skin for morphing capabilities. The two models were analyzed for flutter occurrence and effects on the aeroelastic behaviour of the wing were studied by replacing the aluminium upper surface skin of the wing with a specially developed composite version. The morphing wing model with composite upper surface was manufactured and fitted with three accelerometers to record the amplitudes and frequencies during tests at the subsonic wind tunnel facility at the National Research Council. The results presented showed that no aeroelastic phenomenon occurred at the speeds, angles of attack and aileron deflections studied in the wind tunnel and confirmed the prediction of the flutter analysis on the frequencies and modal displacements.

Piezoelectric Microfiber Composite Actuators for Morphing Wings

Morphing wing technologies provide expanded functionality in piloted and robotic aircraft, extending particular vehicle mission parameters as well as increasing the role of aviation in both military and civilian applications. However, realizing control surfaces that do not void the benefits of morphing wings presents challenges that can be addressed with microfiber composite actuators (MFCs). We present two approaches for realizing control surfaces. In one approach, flap-like structures are formed by bonding MFCs to each side of a metal substrate. In the other approach, MFCs are bonded directly to the wing. Counter intuitively, the flap approach resulted in larger voltage actuation curvatures, with increased mass load. Actuation performance, defined as the ratio of curvature per applied voltage, was as large as 5.8±0.2×10−4 (kV·mm)−1. The direct bonding approach reveals that at zero wing pressure, up to 63±3 μm of displacement could be realized.

Multi-Objective Optimization for the Multiphase Design of Active Polymorphing Wings

Advanced studies have been undertaken using Multidisciplinary Design Optimization (MDO) on the retrofitting of an outboard morphing wing system to an existing conventionally designed commercial passenger jet. Initial studies focusing on the single objective of specific air range improvement for a number of flight phases revealed increases of approximately 4-5% over the baseline aircraft with wing fences across each case. This validated the advantage of re-optimizing the geometric schedules for off-design conditions in comparison with fixed winglets, for which negative effects were observed. Due to the high number of design sensitivities of the outboard wing geometry it has now become necessary to conduct refined studies to analyse the effects of the wing system on additional operational performance metrics, such as take-off, initial climb, approach-climb and landing performance parameters, in order to ascertain a truly holistic representation of the benefits of morphing wing technology. In addition, further effort has been expended to couple the effects of each phase within a multiobjective framework. Thus, refined studies have been performed, incorporating a number of multiobjective optimization methods into a high-end, low fidelity aero-structural-control analysis together with a full engine model and integrated operational performance algorithm. Furthermore, updated aeroelastic functionality and improved aero-structural wing sizing allows for investigation of C-wing configurations. Results reveal the potential for significant field length reductions and climb performance enhancements, while maintaining improvements in cruise performance throughout the entire flight envelope and across multiple stage lengths.

Modeling and experiment of a morphing wing integrated with a trailing edge control actuation system

Morphing wing has attracted many research attention and effort in aircraft technology development because of its advantage in lift to draft ratio and flight performance. Morphing wing technology combines the lift and control surfaces into a seamless wing and integrates the primary structure together with the internal control system. It makes use of the wing aeroelastic deformation induced by the control surface to gain direct force control through desirable redistribution of aerodynamic forces. However some unknown mechanical parameters of the control system and complexity of the integrated structure become a main challenge for dynamic modeling of morphing wing. To solve the problem, a method of test data based modal sensitivity analysis is presented to improve the morphing wing FE model by evaluating the unknown parameters and identifying the modeling boundary conditions. An innovative seamless morphing wing with the structure integrated with a flexible trailing edge control system is presented for the investigation. An experimental model of actuation system driven by a servo motor for the morphing wing is designed and established. By performing a vibration test and the proposed modal sensitivity analysis, the unknown torsional stiffness of the servo motor and the boundary condition of the actuation mechanism model is identified and evaluated. Comparing with the test data, the average error of the first four modal frequency of the improved FE model is reduced significantly to less than 4%. To further investigate the morphing wing modeling, a wing box and then a whole morphing wing model including the skin and integrated with the trailing edge actuation system are established and tested. By using the proposed method, the FE model is improved by relaxing the constraint between the skin and actuation mechanism. The results show that the average error of the first three modal frequency of the improved FE model is reduced to less than 6%. The research results demonstrate that the presented seamless morphing wing integrated with a flexible trailing edge control surface can improve aerodynamic characteristics. By using the test data based modal sensitivity analysis method, the unknown parameter and boundary condition of the actuation model can be determined to improve the FE model. The problem in dynamic modeling of high accuracy for a morphing wing can be solved in an effective manner.

Pressurized artificial muscles

Pressurized artificial muscles are reviewed. These actuators consist of stiff reinforcing fibers surrounding an elastomeric bladder and operate using a pressurized internal fluid. The pressurized artificial muscles, known as McKibben actuators or flexible matrix composite actuators, can be applied to a wide array of applications, including prosthetics/orthotics, robots, morphing wing technologies, and variable stiffness structures. Analytical models for predicting the response behavior have used both virtual work methods and continuum mechanics. Various nonlinear control algorithms have been developed, including sliding mode control (SMC), adaptive control, neural networks, etc. In addition to traditional fluid-driving methods, innovative techniques such as chemical and electrical driving techniques are reviewed. With improved manufacturing techniques, the operational life of pressurized artificial muscles has been significantly extended, thus making them suitable for a vast range of potential applications.