Modeling of Soft Robots Actuated by Twisted-and-Coiled Actuators

Soft robots made from soft materials outperform traditional rigid robots in safety, maneuverability, and adaptability. Various methods have been proposed to actuate soft robots such as cables, pneumatic, or smart materials (e.g., shape memory alloys, dielectric elastomer, or ionic polymer-metal composites, etc.). In this paper, we propose to leverage a recently discovered artificial muscle-twisted-and-coiled actuators (TCAs)-to actuate soft robots. Compared with existing actuation methods, TCAs can be actuated electronically, can be embedded inside soft materials to enable distributed actuation, and are easy and low-cost to manufacture. We establish a general modeling framework for TCAs and TCA-actuated soft robots, including a physics-based model for TCAs as well as both the forward and inverse kinetostatics for TCA-actuated soft robots, where a coupling between TCA actuation and deformation of soft robots exists. Extensive experiments are conducted to verify the proposed models. The presented work will not only lay a theoretical foundation for using TCAs to actuate soft robots but also enable wider application for TCA-actuated soft robots (e.g., manipulation or locomotion).