A lightweight bending actuator based on shape memory alloy and application to gripper

Abstract

The shape memory alloy (SMA) material is embedded into elastic material to make the bending actuator through the shrinkage property of SMA material during being heated. This production method is with the characteristics of long production time and cumbersome making process. As the SMA material is embedded in the elastic actuator, the heat dissipation with the environment is slow, resulting in low actuating efficiency. In this article, a new lightweight bending actuator is developed based on pre-bent SMA wire. The SMA wire is used as the body and actuator, and realizes the initial shape recovery through active control mode instead of relying on heat exchange only. The manufacturing process of the bending actuator is very simple and low-price. The pre-bent angle of SMA wire can be programmed to control the actuator's output angle. By modeling the phase transformation process of SMA wire, the change in Young's modulus at different temperatures is analyzed, and the actuating current and pre-bent angle of SMA wire are calculated. Based on the changing resistance of SMA wire during being heated, the strategy to avoid overheating is designed and achieved. Imitated the form of human hand grasping, a lightweight gripper with palm function is made, and four grasping strategies are designed for the gripper and tested. Finally, the gripper is tested on the continuum arm made of pre-bent actuator. The actuator broadens the application form of SMA wire actuated actuator and provides a new method for designing lightweight and miniaturized soft gripper.