A study of NiTi shape memory alloy springs and its application in a new robotic actuator

A new actuator for a robotic hand, composed of two NiTi shape memory alloy (SMA) springs, is studied. First, the properties of NiTi SMA springs, including load-displacement dependences at various temperatures, resistance-temperature dependence, and recovery-temperature dependence are tested and analyzed. It is found that at a shear strain of 1.5% (a value below which NiTi alloy has a long cycling life) the load at 90/spl deg/C is 8.5 times greater than at 10/spl deg/, the transformation temperature A/sub f/ (austenite-finish temperature) increases with decreasing aging temperature and/or with increasing aging time. Next, a new actuator with two NiTi SMA springs for a robotic hand is studied. It is found that with this new actuation model, the serious limitations of heating and cooling speed which depend on heat transfer processes and make SMA motions slow, are greatly improved.<
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