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).

I. Introduction

Soft robots made from soft materials have been an active and expanding area of research recently because these robots can leverage the inherent softness to accomplish tasks (e.g., locomotion or manipulation) that cannot be achieved with traditional rigid robots [1]–[4]. For instance, soft manipulators are safer than conventional rigid ones for humans to interact with and be around [2], making them beneficial for applications in medical devices, industrial environments, or in more personal settings (e.g., home). Soft manipulators can also deal with uncertain or difficult environments as their compliance allows for more adaptive motion and deformation when contacting, grasping, or avoiding objects [2]. Due to their advantages, many manipulators resembling biological structures have been developed recently (e.g., elephant trunks [5] and octopus arms [6]–[9]).