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Design and analysis of a linear shape memory alloy actuator

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2009
Söylemez, Burcu
Shape memory alloys are new, functional materials used in actuator applications with their high power to weight ratio. The high strength or displacement usage of shape memory alloys makes them suitable for direct drive applications, which eliminate use of power transmission elements. The aim of this research is to develop the methodology and the necessary tools to design and produce linear shape memory alloy actuators to be used in missile systems, space applications, and test equipments. In this study, the test apparatus designed and built to characterize shape memory alloy thin wires is described, and then the characterization tests, modeling and control studies performed on a wire are explained. In the control studies, displacement control through strain, resistance and power feedback is investigated and different control strategies (proportional-integral, proportional-integral with feedforward loop, and neural network) are employed. The results of the characterization tests, simulations and experiments are all presented in graphical and tabular form. From the results it is concluded that through careful characterization, the behavior of SMA wire can be closely approximated through models which can be used effectively to test various control strategies in simulations. Also, satisfactory position control of SMA wires can be achieved through both classical and NN control strategies by using appropriate feedback variables and power is found to be a viable feedback variable. Lastly, a linear SMA wire actuator is designed as a case study. The actuator prototype is produced, suitable control strategies are applied and actuator is experimented to validate the theoretical assumptions. The actuator developed through this work is a technology demonstration and shows that shape memory alloy elements can be utilized in several defense and space applications contracted to TÜBİTAK-SAGE as well as certification test equipments. The development of shape memory alloy actuators that can be used in defense and later in aeronautical/space applications is a critical research and development project for national defense industry.