Design, characterization, modeling, and comparison of helically wrapped super-coiled polymer artificial muscles

Abstract

Super-coiled polymer (SCP) artificial muscles demonstrate a number of desirable properties, like high power density, inherent compliance, light weight, and lowcost. However, the realization of their full potential in achieving appreciable robot motion is hindered by their limited strain or force generation capabilities. Fabricated with multi-thread nylon filament, non-mandrel-coiled SCP actuators can only generate up to 10–20% strain, and mandrel-coiled SCP actuators are often fragile and fail to produce large force consistently. This paper presents the design, characterization, and modeling of helically-wrapped SCP (HW-SCP) actuators. HW-SCP actuators exhibit the advantages of mandrel-coiled and non-mandrel-coiled SCP actuators simultaneously—they can produce 15–55% strain, and consistently lift more than 90 g of weight. The design parameters of HW-SCP actuators can be conveniently adjusted to tune the actuator's performance. Furthermore, this work presents the first comprehensive comparative study of non-mandrel-coiled, mandrel-coiled, and HW-SCP actuators based on conductive multi-thread nylon filament. The correlations between strain and constant voltage were accurately captured by Preisach hysteresis models. The correlations between force and constant voltage were modeled by three low-order polynomial models. This work contributes to the development of high-performance artificial muscles and may facilitate optimal selection of SCP actuators under scenario-specific future studies.