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.