University of Twente Student Theses


SMA wire actuator in a morphing wing

Driesen, J.B. (2017) SMA wire actuator in a morphing wing.

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Abstract:The design of an air foil is usually a compromise between the requirements of different flight conditions. Commercial airliners usually spend most of their time cruising, and therefore the air foil is optimized for that condition. UAV drones however have a different mission profile, spending time on cruising, loitering, ascending and descending. A morphing wing that can change its air foil to optimize the efficiency during the entire mission profile will be highly beneficial. Another possibility is to use the morphing capabilities of the wing as actuation. Twisting of the wing can act as an aileron and a wing bend over its profile can act as a flap. This will eliminate the need for separate control surfaces on the wing. A morphing wing will change its surface smoothly, instead of the disruptive change of current actuators. This will make the wing smoother, quieter and more efficient. The research described in this report will expand upon earlier research done at ITA by Campos de Almeida, and tries to see if it is possible to create a functioning morphing wing that can bend both upwards and downwards, using shape memory alloy (SMA) wire. SMA is a material that is able to elongate up to 8% and recover its original shape when heated (Lagoudas, 2008). The wire will be attached inside the wing in elongated form. When heated it will shrink to its normal length, bending the wing. A morphing wing was designed and constructed, using 7 3d-printed PLA ribs with a NACA0012 profile. These ribs were connected with rods to create a wing frame. 12 SMA wires were attached to the frame. The SMA wires were attached to electrical wires and the frame was covered with model wood sheets to create a smooth surface. A 12 mm diameter rod was attached to the wing in order to clamp it in the wind tunnel. The wing was placed inside a subsonic wind tunnel at Professor Feng Laboratory that belongs to Aeronautic Engineering Division from Instituto Tecnolgico de Aeronutica (ITA). The wind tunnel has a 457 mm by 457 mm cross-section and is 1200 mm in length. The wind tunnel is outfitted with a force moment balance and a pressure sensor. The wing was tested multiple times in three configurations: unactuated, actuated upwards and downwards. The lift coefficient was plotted against the angle of attack. The symbols show the error margin caused by the noise in the signal. It can be seen that the morphing states of the wing shift the Cl graph, acting like a flap. This research set out to prove that SMA wire can be used as an actuator and in that it succeeded. The tests in the wind tunnel show that even with the 2-mm deflection caused by the SMA wire, the characteristics of the wing change considerably. This proves that SMA is a feasible actuator in a morphing wing. This opens the way for new research into extending the range of motion of the wing and optimizing the morphed air foil shape. Other forms of morphing, like twisting and sweeping can be implemented too. When a control system is made for the actuation of the wires, a prototype wing could be fabricated and tested on a RC plane.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Programme:Mechanical Engineering MSc (60439)
Keywords:air foil, UAV drones, morphing wing, SMA wires
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