How do you incorporate active and passive control devices into the design of morphing and adaptive wings?

1 Active Control Devices

Active control devices are those that require external power and actuation to modify the wing shape or surface. They include mechanisms such as flaps, ailerons, spoilers, slats, tabs, and trailing edge devices, which can be deployed or retracted to adjust the lift, drag, and roll of the wing. Active control devices can also be used to create variable camber, twist, or sweep of the wing, by using flexible materials, actuators, or smart structures that can deform or rotate under electrical or thermal stimuli. Active control devices can provide precise and rapid control of the wing response, but they also add weight, complexity, and maintenance costs to the system.

2 Passive Control Devices

Passive control devices are those that do not require external power or actuation, but rely on the inherent properties of the wing material or structure to adapt to the airflow. They include features such as dimples, grooves, bumps, or serrations, which can alter the boundary layer behavior and reduce drag or noise. Passive control devices can also be based on shape memory alloys, piezoelectric materials, or bio-inspired designs, which can change their stiffness, curvature, or orientation under mechanical or thermal loads. Passive control devices can reduce the power consumption and mechanical stress of the system, but they also have limited control authority and range of motion.

3 Design Considerations

When designing morphing and adaptive wings with active and passive control devices, a trade-off between performance, reliability, and feasibility must be considered. Flight envelope and mission requirements of the aircraft determine the optimal wing shape and configuration for different phases of flight, such as take-off, cruise, maneuver, and landing. Aerodynamic performance and stability of the wing depend on the lift-to-drag ratio, pressure distribution, stall characteristics, and dynamic response to gusts and perturbations. Structural integrity and durability of the wing depend on stress and strain distribution, fatigue and damage tolerance, as well as thermal and acoustic effects of wing deformation. Control system and actuation mechanism also need to be taken into account, considering type, location, number of control devices, power and weight requirements, sensor and feedback signals, control laws and algorithms.

4 Design Methods

The design of morphing and adaptive wings with active and passive control devices necessitates a multidisciplinary approach that integrates aerodynamics, structures, materials, and control disciplines. To achieve this, computational fluid dynamics (CFD) and finite element analysis (FEA) can simulate the fluid-structure interaction and the deformation of the wing under various loads and conditions. Wind tunnel and flight tests can then validate and refine the computational models and the control strategies, while optimization and machine learning techniques can find the optimal design parameters and control inputs for the wing. All of these methods can measure the actual behavior and performance of the wing in realistic scenarios, as well as learn from data and feedback to improve the wing performance and adaptability.

5 Design Examples

Researchers and engineers have proposed and developed various morphing and adaptive wings with active and passive control devices. For instance, the X-53 Active Aeroelastic Wing (AAW) program demonstrated the use of active control devices to twist the wing of an F/A-18 fighter jet, improving maneuverability and agility. Additionally, the Smart Wing project used shape memory alloy actuators to create variable camber and twist of a wing model, showing enhanced lift and drag characteristics. The Adaptive Compliant Trailing Edge (ACTE) project replaced the conventional flaps of a Gulfstream III aircraft with flexible trailing edge devices, reducing fuel consumption and noise emissions. Lastly, the BioWing project mimicked the wing shape and motion of birds and bats, using passive control devices such as compliant joints and membranes to create morphing and adaptive wings.