A large-stroke shape memory alloy spring actuator using double-coil configuration
A large-stroke shape memory alloy spring actuator using double-coil configuration
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DOI：
10.1088/0964-1726/24/9/095014
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发表时间：
2015-09-01
影响因子：
4.1
通讯作者：
Cho, Kyu-Jin
中科院分区：
文献类型：
--
作者：
Kim, Seung-Won;Lee, Jong-Gu;Cho, Kyu-Jin
增加形状记忆合金 (SMA) 执行器运动范围的一种方法是产生 SMA 位移，该位移不仅与应变引起的变形相关，而且还与平移和旋转引起的刚体运动相关。刚体运动使得SMA能够在不超过最大恢复应变的情况下产生更大的位移，从而使SMA执行器能够具有更大的形状恢复比。为了改善 SMA 线致动器的线性致动行程，提出了一种新型 SMA 弹簧致动器，该致动器采用双线圈几何形状，允许 SMA 的位移主要由刚体运动引起。双线圈 SMA 弹簧致动器是通过将 SMA 线卷绕两次来制造的，因此两次卷绕导致双线圈 SMA 弹簧致动器的初始长度减小。根据几何参数的参数化研究，通过有限元分析和实验验证了几何参数对双线圈 SMA 弹簧致动器致动特性的影响。双线圈 SMA 弹簧致动器的位移-力曲线是非线性的，当致动器将其配置从双线圈形状转变为单线圈形状时，弹簧刚度会发生变化。根据参数研究的结果，增加线径会增加初级和次级线圈的刚度，增加初级内线圈的直径会降低初级和次级线圈的刚度，而增加次级内线圈的直径只会降低次级线圈的刚度。结果表明，其中一种初始长度为8 mm的双线圈SMA弹簧致动器的恢复率为1250%，而具有相同几何参数的单线圈SMA弹簧致动器的恢复率为432%。
One way to increase the range of motion of shape memory alloy (SMA) actuators is to create displacements of the SMA associated with not only the deformation from straining but also rigid-body motion from translation and rotation. Rigid-body motion allows the SMA to create larger displacements without exceeding the maximum recovery strain so that the SMA actuators can have a larger shape recovery ratio. To improve the linear actuation stroke of SMA wire actuators, a novel SMA spring actuator is proposed that employs a double-coil geometry that allows the displacement of the SMA to be mainly induced by rigid-body motion. A double-coil SMA spring actuator is fabricated by coiling an SMA wire twice so that the double coiling results in a reduction of the initial length of the double-coil SMA spring actuator. The effects of the geometric parameters on the actuation characteristic of a double-coil SMA spring actuator are verified numerically by finite element analysis and experimentally according to a parametric study of the geometric parameters. The displacement-to-force profile of the double-coil SMA spring actuator is nonlinear, and the spring stiffness changes when the actuator transforms its configuration from a double-coil shape to a single-coil shape. According to the results of the parametric study, increasing the wire diameter increases both primary and secondary coil stiffness, and increasing the primary inner coil diameter decreases both primary and secondary coil stiffness, whereas increasing the secondary inner coil diameter decreases only the secondary coil stiffness. The result shows that one of the double-coil SMA spring actuators with an initial length of 8 mm has a recovery ratio of 1250%, while the recovery ratio of the single-coil SMA spring actuator with the same geometric parameters is 432%.