A novel multi-wire SMA-based actuator with high-frequency displacement

摘要

Shape Memory Alloys (SMA) are a group of metallic alloys that can return to their original shape when subjected to a temperature transformation between two phases. SMAs have been used as an alternative solution to conventional actuators in different applications of the robotics, biomedical, aerospace and automation domains because of their characteristics; being one of the leading solutions in different fields such as soft robotics and bio-inspired mechanisms. However, these actuators are still limited due to their operating frequency, their electrical efficiency, and their control performance due to their non-linearities. This paper presents a new multi-wire actuator structure based on SMA, with two different activation strategies. By combining the use of a multi-wire SMA in an alternative way, the overall recovery time is reduced. Thus, higher frequencies can be achieved in the reference signal. In this study, the effect of the diameter, geometry and activation temperature of the wires is evaluated in two different configurations. Firstly, when the actuator produces a linear displacement and, secondly, in an antagonistic configuration where the final displacement is a rotating movement. The results prove that the operating frequency of the multi-wire actuator increases considerably, when compared to the configuration where only one SMA wire is used. Moreover, it can be stated that the performance of the actuator improves when using wires with a thinner diameter and a higher activation temperature, with weights closer to the maximum force supported and a geometrical disposition of the wires that brings them as close as possible.