Twisted polymer actuators (TPAs) are a promising new low-cost actuation technology that can generate torsional or linear actuation. While analytical models for TPAs have been explored to predict their thermal actuation responses, these models are either based on elastic properties of the twisted monofilament, which does not allow for design of initial twist, or ignore the internal stresses between layers. How the elastic properties of the precursor (untwisted) monofilament affects internal stresses is not well understood. Our goal is to better understand how the actuation response is affected by internal stresses. To study the internal stresses in TPAs, we simulate a straight twisted polymer actuator (STPA) using a finite element (FE) model. The linear elastic mechanical properties of the untwisted monofilament as a function of temperature are needed as inputs to the FE model, and are obtained experimentally. FE results are compared with experimental actuation responses and closed-form predictions using models which neglect internal stresses, namely the Shafer et al and the averaged Shafer et al models. The simulations and experiments use a STPA to generate torsional actuation under free torsion conditions. Under these conditions, we show that interlayer stresses are not the main driver for the torsional actuation of STPAs and FE model predicts experimental data about as well as closed-form models. Additionally, we use the internal stresses to better understand the actuation mechanism of TPAs and evaluate their effects on STPAs torsional actuation under free torsion conditions.

扭曲聚合物致动器（TPA）是一种有前途的新型低成本致动技术，可以产生扭转或线性致动。虽然已经探索了TPA的分析模型来预测其热激励响应，但这些模型要么基于扭曲的单丝的弹性特性（不允许设计初始扭曲），要么忽略层之间的内部应力。前体（未加捻）单丝的弹性如何影响内部应力的方法尚不清楚。我们的目标是更好地了解内部应力如何影响驱动响应。为了研究TPA中的内部应力，我们使用有限元（FE）模型模拟​​了直绞聚合物执行器（STPA）。需要将未加捻的单丝的线性弹性力学性能随温度的变化作为有限元模型的输入，并通过实验获得。有限元结果与忽略内应力的模型，即Shafer模型，与实验驱动响应和闭式预测进行比较等人和平均Shafer等人模型。仿真和实验使用STPA在自由扭转条件下产生扭转驱动。在这些条件下，我们表明层间应力不是STPA扭转致动的主要驱动力，而FE模型可以预测有关闭式模型的实验数据。此外，我们利用内部应力更好地了解TPA的致动机理，并评估它们在自由扭转条件下对STPA扭转致动的影响。