Development of morphing wing mechanism using shape memory alloy actuator

A flap morphing mechanism was proposed to improve the aerodynamic efficiency by removing discontinuous sections which cause aerodynamic losses. The proposed morphing wing changes the wing shape smoothly by using shape memory alloy (SMA) wire actuator. Flexinol wires were used for the SMA actuator and the actuation characteristics of the SMA wires were experimentally investigated. Joule heating method was used to actuate the SMA actuator for fast response. An appropriate current range to control the SMA wire actuator was measured. The generated load by the clamped SMA wire was measured when an electric current is applied to the wire. The force generated by the SMA wire increased as the electric current increased, however, the force was reduced when the current reaches a certain level. The temperature of the SMA wire increased as the applied current increased. However, the temperature of the SMA wire becomes larger than the annealing temperature of the SMA wire by over-currents, thermo-mechanical characteristics of the SMA wire changed and the actuation characteristic critically deteriorated. Appropriate stress levels for the best actuation response of the SMA wire were also experimentally investigated. The deflection ranges of the SMA wires were measured under various constant loads when an electric current is applied. The SMA wire actuator for morphing wing was designed based on the test data. A wing section was fabricated to demonstrate the morphing wing mechanism using the SMA wire actuator. The wing section was smoothly deformed when an electric current was applied. The aerodynamic characteristics of the deformed airfoils under various electric currents were also investigated through numerical analysis.