Modeling framework for macroscopic dynamics of twisted and coiled polymer actuator driven by Joule heating focusing on energy and convective heat transfer

In this paper, a nonlinear dynamics model of the twisted and coiled polymer actuator (TCPA) driven by Joule heating is proposed. TCPA is an actuator based on the phenomenon that the twisted and coiled polymer contracts by heating. TCPA has received considerable research attention after the discovery of this phenomenon. Although several conventional models were proposed to explain TCPA behavior, they do not address several characteristics of a real TCPA, namely, the delay of the displacement to the temperature, temperature behavior to the input (Joule heating), and effect of the convective heat transfer on the relationship between the displacement and temperature. The macroscopic modeling framework presented herein explains these properties. The main ideas of the proposed model are (1) the energy relating to TCPA, and (2) the temperature and velocity dependence of the convective heat transfer coefficient. Experiments were conducted for three kinds of TCPA. It was verified that the proposed model is more viable than a conventional model. In particular, the proposed model reduced the prediction errors of the displacement by more than 50% compared with the conventional model.