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Smart Structures and Systems
  Volume 14, Number 5, November 2014, pages 765-784

Performance analyses of antagonistic shape memory alloy actuators based on recovered strain
Zhenyun Shi, Tianmiao Wang and Liu Da

Abstract     [Full Text]
    In comparison with conventional shape memory actuated structures, antagonistic shape memory alloy (SMA) actuators permits a fully reversible two-way response and higher response frequency. However, excessive internal stress could adversely reduce the stroke of the actuators under repeated use. The two-way shape memory effect might further decrease the range of the recovered strain under actuation of an antagonistic SMA actuator unless additional components (e.g., spring and stopper) are added to regain the overall actuation capability. In this paper, the performance of all four possible types of SMA actuation schemes is investigated in detail with emphasis on five key properties: recovered strain, cyclic degradation, response frequency, self-sensing control accuracy, and controllable maximum output. The testing parameters are chosen based on the maximization of recovered strain. Three types of these actuators are antagonistic SMA actuators, which drive with two active SMA wires in two directions. The antagonistic SMA actuator with an additional pair of springs exhibits wider displacement range, more stable performance under reuse, and faster response, although accurate control cannot be maintained under force interference. With two additional stoppers to prevent the over stretch of the spring, the results showed that the proposed structure could achieve significant improvement on all five properties. It can be concluded that, the last type actuator scheme with additional spring and stopper provide much better applicability than the other three in most conditions. The results of the performance analysis of all four SMA actuators could provide a solid basis for the practical design of SMA actuators.
Key Words
    shape memory alloy; performance; antagonistic structure; actuator design; recovered strain
Zhenyun Shi, Tianmiao Wang and Liu Da: Robotic Laboratory, BeiHang University, HaiDian District, 37 XueYuan Road, Beijing 100191, China

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