This paper presents a novel flexible shape memory alloy (SMA) actuator, which is mainly composed of an SMA wire and a multilayer tubular structure. The multilayer tubular structure, which consists of a polytetrafluoroethylene tube, a metallic hose and a rubber tube, possesses the properties of good flexibility and high axial stiffness. The flexibility makes the SMA actuator easy to integrate into a compact or thin, narrow space with dimension constraints. The high axial stiffness helps in handling serious bending and prevents buckling of the SMA actuator. To verify the performance of the proposed actuator, a prototype was fabricated and a corresponding experimental setup was established. The effects of critical parameters, including heating current, winding angle, and applied load were experimentally investigated. The result demonstrates the feasibility of the proposed actuator and its easy integration into confined spaces. This work creates expanded opportunities for developing SMA actuators into broader application fields.
This paper reports an empirical formula that predicts the electrohydrodynamic (EHD) thrust for the point-to-grid configuration with small electrode gap distances. This is accomplished by modifying the classical thrust formula with a loss factor to account for the nonuniform electric field and the drag force on the collector. Experiments are conducted to measure the dependence of the corona current and EHD thrust on the applied voltage for various electrode gap distances. From the experiment results, the proposed formula is empirically derived with electrode gap distance and applied voltage as the independent variables. The proposed formula predicts well the EHD thrust with an accuracy of 40 μN.
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