Design and development of electro mechanical bistable functions using shape memory alloy

摘要

An attempt has been made to realize electro mechanical bistable logic functions using shape memory alloy (SMA) which can exhibit functionalities similar to that of electronic logic devices. Titanium-nickel (TiNi) based SMAs are widely used because of its large work output per unit of actuator mass thereby enabling miniaturization; moreover, it can be used in harsh working environments. The paper presents implementation of bistable logic states in terms of NOT, OR, and NOR logics and its combinatorial application, the digital to analog converter (DAC) using suitable configurations / structures with SMA wire actuators. The basic and common structural configuration comprises of a nitinol wire, a bias spring, a slotted disc and a shaft. The SMA wire is wound as a loop through the peripheral slots of the disc and its ends are connected to a supporting member. The rod passes via the central slot of the disc and is engaged with the bias spring around it, which helps in restraining the SMA wire during the cooling cycle. The actuation of SMA moves the rod; the displacement of the rod is marked as the output. These designs are not based on linkage mechanisms; are implemented in MESO scales and could later be translated into the micro domain.