Design and Verification of a Smart Wing for an Extremely-Agile Micro-Air-Vehicle

A special class of fixed-wing Micro-Air-Vehicles (MAV) is currently being designed with the capability to hover vertically like a rotary-wing vehicle through a flight manoeuvre known as prop-hanging. This MAV design provides the range superiority of a fixed-wing aircraft with the hover capabilities of a rotary-wing aircraft to accomplish a variety of missions. The hover manoeuvre requires roll control of the fixed-wing aircraft through differential aileron deflection to maintain its orientation. A conventional aileron control system typically consists of a number of discrete components that contribute significantly to the gross weight and power consumption of the aircraft especially in the case of a MAV. Therefore, it is advantageous to use smart structure approaches with active materials to design a lightweight, robust wing for the MAV with less power requirements. The proposed smart wing structure consists of a composite spar and ailerons that have bimorph active ribs consisting of piezoceramic fiber actuators with interdigitated electrodes. Actuation is enhanced by preloading the piezoceramic fiber actuators with a compressive axial load. The preload is exerted on the actuators through a passive latex or electro active polymer (EAP) skin that wraps around the airfoil. An EAP skin would further enhance the actuation by providing a electrostatic effect of the dielectric polymer. Analytical modeling as well as finite element analysis show that the proposed smart wing concept could achieve the target deflection of 30° in both the wind-off and wind-on flight conditions. Several bimorph actuators have been manufactured and an experimental setup has been designed to measure the static and dynamic deflections. results validated the analytical finite further to the performance of the smart 75 mm and 100 respectively, for an overall chord of 240 mm. The center spar section of the wing is fabricated from carbon fiber pre-preg and designed to connect the active trailing edge and the leading edge of the wing. The leading edge is fabricated out of an inner foam core covered by woven carbon fiber pre-preg in order to provide the required smoothness and rigidity. Both the leading edge and the active aileron are designed for ease of detachment from the composite spar. The upper and lower skin of the wing is an EAP film pre-strained in tension to increase the actuation deflection of the aileron. The skin is interconnected to two tension rollers to adjust the tensional load during the initial experimental investigation. This active trailing edge wing makes use of an active skin concept where the skin provides a pre-compressive load on the MFC actuators and enhances the deformation of the active structure. The EAP skin material would be covered by a very compliant electrode layer for actuation of the active skin. Both analytical as well as finite element analyses have been conducted to predict the deflection performance of the smart wing model for EA-MAV application.