Sensorless displacement estimation of a shape memory alloy coil spring actuator using inductance

Abstract

To measure the displacement of a shape memory alloy (SMA) coil spring actuator for feedback control, displacement sensors larger than the actuator are normally required. In this study, a novel method for estimating the displacement of an SMA coil spring actuator without a sensor is proposed. Instead of a sensor, coil inductance is used for estimating the displacement. Coil inductance is estimated by measuring the voltage and the transient response of the current. It has a one-to-one relationship with the displacement of the coil and is not affected by load. Previous methods for estimating displacement using resistance measurements are heavily affected by load variations. The experimental results herein show that displacement is estimated with reasonable accuracy under varying loads using coil inductance. This sensorless method of estimating the displacement of an SMA coil spring actuator can be used to build a compact feedback controller because there is no need for a bulky displacement sensor.

A novel 4-DOFs origami enabled, SMA actuated, robotic end-effector for minimally invasive surgery

“…er, recent works incremented the knowledge and usability of these actuators, defining more efficient and and design methods. Literature works investigated the possibilities to obtain sensorless feedback for SMA linear actuators in helical spring shape exploiting the measurements of the inductance relative to actuators geometry [21], thus minimizing the components to integrate in the robot. Small scale robots (< cm) applicability since surface phenomena become predominant respect to volume ones improving thermal exchanges therefore incrementing actuators performance.…”

Sistema de suministro de energía eléctrica para actuadores basados en aleaciones con memoria de forma

“…A lo largo del tiempo sus campos de aplicación han sido diversos, partiendo en 1960 de la industria aeroespacial y de comunicaciones con el desarrollo de antenas satelitales que deben de expandirse o contraerse, pasando por aplicaciones domésticas en ventanas que se abren o cierran de acuerdo a la temperatura ambiente, hasta extremidades de robots humanoides o prótesis de extremidades humanas que obtienen su capacidad de movimiento gracias a los alambres musculares [2]. Recientemente se ha diversificado el campo de aplicación de actuadores desarrollados en base a este tipo de materiales gracias a su simplicidad, relación fuerza-peso, bajo costo, operación silenciosa y tiempo de vida útil relativamente amplio [2][3]. Esta última característica está directamente relacionada con el "buen manejo" del alambre muscular.…”

Design of Shape Memory Alloy Coil Spring Actuator for Improving Performance in Cyclic Actuation

“…The coil-type SMA spring actuator can generate a larger displacement, above 100% of its original length, which allows it to have wider applications compared to the wire-type SMA actuator; the wire-type SMA actuator can generate a displacement less than 6–8% of its original length. The coil type can use inductance to measure the displacement without sensors [16]. The performance of coil-type SMA spring actuators is wide-ranging, in terms of force and displacement, depending on how the coil is designed [17].…”