Design of highly stretchable soft actuator composed of shape memory alloy and optical strain sensor for artificial muscle

Abstract

In this thesis, we describe the development progress of a feedback controllable soft actuator that is composed of Shape Memory Alloy that has high output force and displacement and optical strain sensor that can stretch over 100 % of its initial length. We have designed a system that can achieve a fast cooling rate by applying the coolant circulation system in a SMA coil spring actuator. The optimization of cooling and heating rate with respect to the thermal properties of the coolants and flowrate of the fluid were performed by simulation of heat transfer model for the actuator and several experiments with various coolants. From the experiments, the actuator that applies cooling system with mineral oil shows fastest actuation speed of 0.5 Hz with 40 % Contraction. Also, the fabricated stretchable strain sensor can measure up to 100 % extension strain with high signal-to-noise ratio. The sensor was fabricated to tube shape for easy integration with soft actuator above, and the performances in dynamic situation were experimented. Through this research, we suggested the possibility of producing a new type of soft actuator for artificial muscle that combines a soft actuator and sensor together.