Towards Biomimetic Actuation in Prostheses Using Shape Memory Alloy

Abstract

Shape Memory Alloy (SMA) has been identified as an ideal candidate to actuate the finger joints of hand prosthesis due to its silent operation, small size, high force to weight ratio and operational similarity with human muscles. When current is applied to a SMA wire, the material is heated up. A phase transformation from Martensite to Austenite takes place and the wire contracts. This work evaluates the displacement and force produced from the contraction of a type of SMA wire, i.e. Nitinol (Ni-Ti). The displacement is determined by a linear potentiometer while the force is determined by a load cell. Furthermore the impacts of varying the bias force exerted on the SMA wire and the input current passed through the wire are investigated. Such insight into the characteristics of SMA can be used to realize biomimetic actuation in order to improve the dexterity of hand prosthesis.