Modeling and Simulation of Soft Robots Driven by Embedded Artificial Muscles: an Example using Twisted-and-Coiled Actuators

Soft robots have been intensively investigated for manipulation and locomotion in recent years. However, the current state of soft robotics has significant design and development work but lags in modeling and control due to the difficulty in modeling them. In this paper, we present a physics-based analytical framework to model soft robots driven by Twisted-and-Coiled Actuators (TCAs), an artificial muscle that can be arranged in arbitrary shapes in the soft body of a soft robot to achieve programmable motions. The framework can model 1) the complicated routes of multiple TCAs in a soft body and 2) the coupling effect between the soft body and the TCAs during their actuation process. When not actuated, a TCA in the soft body is an antagonistic elastic element that restrains the magnitude of the motion and increases the stiffness of the robot. By stacking several modules together, we simulate the sequential motion of a soft robotic arm with three-dimensional bending, twisting, and grasping motion. The presented modeling and simulation approach will facilitate the design, optimization, and control of soft robots driven by TCAs or other types of artificial muscles.