SMA-based bionic integration design of self-sensor–actuator-structure for artificial skeletal muscle

This paper presents a novel shape memory alloy (SMA)-based artificial skeletal muscle (AM) with functions of actuating, energy-storing and self-sensing. The design is based on the comparison of skeletal muscle and SMA wire mechanical properties that are described by force–velocity and force–length relationships. Experimental results have shown that SMA wires can initially imitate force–velocity properties of skeletal muscles, but cannot imitate their force–length properties, which is improved by adding an anti-overstretching flexible body. Besides, a simple but effective artificial tendon is utilized to achieve energy storage like human tendon. In order to realize the self-sensing function of the AM, self-sensing properties of SMA wires are explored and modeled based on the experimental study of resistivity variations. The AM self-sensing capability is further demonstrated by its application to a 1 degree of freedom (DOF) robotic ankle-foot.