Variable inductive shape memory spring based multifunctional module for high sensitivity measurements

Abstract

Shape memory elements as sensing units have promising potential; the prospect of using shape memory alloy coil as a multi-functional module using the inductive principle is assessed in this work. The self-sensing phenomenon in SMA is dominantly explored from the change in electrical resistance, however, the same can be realized from the variation in inductance in its coiled form. This article introduces a unique, variable inductive sensing system using an SMA spring for high sensitivity measurements, performance of which greatly relies on its coil geometry and permeability. The configuration enables the sensing operation at an isothermal condition for testing force, displacement, and as a proximity sensor. Experimental verification of the proof-of-concept for sensitivity enhancement reveals that adding an iron core results in a sensitivity of 0.1 μH/0.1 N and 0.16 μH/mm, for force and displacement sensing respectively which is a twofold increase over the system's sensitivity with an air core.