Physics-Based Modeling of Twisted-and-Coiled Actuators Using Cosserat Rod Theory

Twisted and coiled actuators (TCAs) have recently emerged as a promising artificial muscle for various robotic applications because they are strong, low cost, and customizable. To better facilitate the applications, it is critical to establish general and precise models for different types of TCAs (e.g., self-coiled, free-stroke, conical, etc.). Although several modeling methods have been proposed recently, existing models either fail to capture the nonlinearity during large deformations or cannot model TCAs with nonuniform geometries. In this work, we establish a general framework for modeling TCAs using Cosserat rod theory that can capture the nonlinearity of large deformations and simulate TCAs with nonuniform geometries. Furthermore, we show existing methods are special cases of our general model. Comprehensive statics and dynamics experiments are conducted to verify the proposed model, and the results demonstrate that the model is more accurate than existing ones, especially when a TCA is subject to large deformations. Given the wide applications of TCAs, our general model can help to better design, optimize, and control systems/robots/devices driven by different types of TCAs.