Control system design for a morphing unmanned air vehicle wing using shape memory alloy actuators

Abdullah, E 2011, Control system design for a morphing unmanned air vehicle wing using shape memory alloy actuators, Doctor of Philosophy (PhD), Aerospace, Mechanical and Manufacturing Engineering, RMIT University.


Document type: Thesis
Collection: Theses

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Title Control system design for a morphing unmanned air vehicle wing using shape memory alloy actuators
Author(s) Abdullah, E
Year 2011
Abstract  Morphing wing technology allows modification of aerodynamic behavior of the wing by changing its shape during flight. This can be used to achieve optimum flight performance during cruise and reduction in fuel consumption. For UAVs in particular, the biggest constraint is the limited space available which makes it difficult for a morphing wing to be implemented using conventional mechanical actuators. Shape memory materials are a suitable candidate for actuators in a morphing wing design as they are easy to install and electrically activated. Shape memory alloys (SMA) are lightweight, can produce a large force and consequently large deflections. However, its nonlinear behavior proves to be a major challenge in the development of the controller. This research project investigated the potential of SMA actuator application in a morphing UAV wing design and develops a suitable control system. In order to reduce power consumption and minimise cost, wire bundle SMA actuators were incorporated in the design. Due to the nonlinear behavior of the SMA actuator, it was critical to incorporate a feedback control system that was able to accurately morph the wing shape. The proportional-integral-derivative (PID) controller was used as the baseline for the control system design. It was combined with a compensator in order to improve the controller’s accuracy. Experiments were conducted under wind tunnel conditions at different Reynolds numbers and angles of attack. The wind tunnel experiments verified the robustness of the control system for morphing UAV wing and the effect on aerodynamic performance. The results showed that the use of SMA actuators for wing morphing is feasible and a significant improvement in lift-to-drag ratio was measured when the wing shape was morphed. The penalty associated with morphing a wing is increased weight due to the actuation mechanism and an increase in power required. A trade-off study was conducted and it showed that it was possible to reduce the power required and increase loiter time for medium and large UAVs. The contribution of this research in developing a control system of morphing UAV wing with minimum weight and power penalty by utilizing SMA wire bundle actuator is a stepping stone towards further development of morphing wing technology capable of maintaining high aerodynamic efficiency throughout a UAV cruise and loiter segment. This thesis highlights the issues related to thermal sensitivity and mechanical performance that need to be addressed when integrating SMA actuators in a morphing wing design.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Aerospace, Mechanical and Manufacturing Engineering
Keyword(s) Morphing wing
shape memory alloys
UAV
control system
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