A compact rotary motor actuated by shape memory alloy mini springs

Abstract

Shape memory alloys have recently gained attention for applications in motor driving components. The most expressive advantage of shape memory alloy components in that type of application is the high torque to motor weight ratio. Considering the importance of these studies, this article presents the design, manufacture, and theoretical and experimental analyses of a rotary motor driven by Ni–Ti shape memory alloy mini springs. The adopted motion mechanism allows the motor to run in continuous and bidirectional rotation mode, where speed and torque are determined by a drive sequence. A simplified analytical model was implemented, considering the thermomechanical characteristics of the shape memory alloy springs. Experimental tests with and without electrical drives were performed using properly designed electronic measurement instrumentation. The principal scientific contribution of this work is the demonstration of the motor’s functionality and torque generation. An energy density index of 1.41 × 10−3 Nmm/mm3 was attained, which is higher to those of other similarly constructed motors in the literature.