A Stretched Out Structure Actuated by Shape Memory Alloy Springs

The character of high energy density has made shape memory alloys (SMA) be applied in some smart structure as actuators. Compared with other actuator materials, SMA can produce larger driving force and recoverable strain. But a SMA actuator provides only limited recoverable displacement which can not cater some stretched out structure's requirement. When multiple shear elements assembled together are actuated by SMA springs, an efficient space stretched out structure can be acquired which also can be folded by SMA springs. This structure can be designed by the bar length of shear element, the initial angle, the terminal angle and so on; through mechanics analysis of the bars under the load of stretching or folding, a mechanics design can be implemented for SMA springs' unfolding force and folding force; wire diameter and intermediate diameter of SMA springs also can be designed according to the driving force of SMA springs; activation efficiency of the stretched out structure can be optimized by the position layout of SMA springs, fashion layout of SMA springs and number of them. The results of experiment also indicate that the structure has a good effect for large scale unfolding or folding in plane. The structure also realizes enlargement of the limited displacement of SMA springs in some degree.