Research and application of novel planar bending embedded shape memory alloy actuator

Abstract

To overcome low-response speed and low-control precision in the existing traditional shape memory alloy (SMA) actuators, a new type of structure named planar bending embedded SMA actuator was developed. Two SMA wires were embedded in parallel with the axis of the elastic rod. The recovering wire, which was superposed along rod's axis, was set to obtain ‘U’ memory shape and the restoring wire, which was placed off-axially, got straight memory shape. The differential stain gauges were located at suitable position in corresponding to the actuator's bending direction in order to measure the signal of displacement. By making use of continuity, common origin and common limit conditions, and adjusting martensite fraction coefficients appropriately, the analytical model was deduced to adequately account for the presence of major and minor hysteresis loops. The structural parameters of 60 mm long actuator, such as rod's radius, wire's radius, wire's recoverable curvature, and offset distance, were optimized by combining analytical model with experimental results. The experimental results prove the merits in optimal prototype.