Robot assisted facial expressions with segmented shape memory alloy actuators

Abstract

This paper introduces a robotic technology-based supporting device, the robot mask, to enhance facial expressiveness and support physiotherapy for facial paralysed persons. The wearable device, which consists of shape memory alloy (SMA)-based linear actuators, functions by pulling the facial skin towards anatomically selected directions. Since facial expressions are silent, SMA was selected over electrical motors. This paper introduces a compact and fully controllable actuation unit with position feedback and a novel controlling scenario that uses the selected hybrid actuation of bidirectional multi segment SMA wires in series to pull the wires. When designing the actuators, a biomechanical analysis was conducted to find anatomical parameters of natural smiles, and the robot mask was evaluated for its suitability as a facial expression supporter.