Shape memory alloy actuator with active cooling device and deflectable winglet application

Abstract

Heating and cooling time directly influence the response speed of a shape memory alloy (SMA) wire actuator. An SMA wire is heated quickly by electric current, however quickly cooling it to a given temperature is difficult. In this study, we proposed a pipeline-type active air convection cooling scheme, which uses compressed air as cooling airflow to achieve rapid active cooling of SMA wire actuators. We designed an SMA wire linear actuator consisting of SMA wires, a compressed air tank, an air valve, an Outlet Pipeline, an SMA Cooling Pipeline, and some other additional accessories. We established theoretical models of heat transfer under natural cooling and active convection cooling of an SMA wire. In addition, we carried out theoretical simulation and experiments on a NiTi alloy SMA wire with a diameter of 1 mm and compared the accuracy of simulation with test results. The SMA wire actuators are used for deflectable morphing winglets of aircraft wing. We designed three-dimensional numerical models of the morphing winglets that can be deflected within ±20° and the experimental models are machined and assembled. Final test results show that active cooling time is reduced by more than 70% compared with natural cooling and the response speed is improved significantly.