Soft robots are utilized in various operations such as rehabilitation, manipulation, and locomotion. These robots are sometimes excited by means of rubber based bending actuators, which are highly nonlinear and hyperelastic. In addition, in contrast to robots with rigid links and common actuators, continuous deformation of soft bending actuators in the presence of external forces makes the modeling more complicated. Thus, introducing a proper mathematical framework that accurately describes mechanical behavior of these actuators is still a challenge. In this research study, an analytical static model based on the Neo-Hookean material model is proposed. By resorting to the proposed model, a nonlinear relation between the actuator shape and inlet actuation pressure is extracted. Next, by means of the Euler–Bernoulli beam theory, the effect of external forces on the actuator configuration is investigated. Finally, experimental results are presented to validate the proposed theoretical model. In this regard, first, the actuator nonlinear behavior in a free motion is appropriately verified. Then, the actuator configuration, in the presence of two conventional external forces, called following and fixed direction, is analyzed.

中文翻译：

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考虑外力约束的软加强弯曲执行器的静态建模

软机器人用于各种操作，例如康复、操纵和运动。这些机器人有时通过高度非线性和超弹性的橡胶弯曲致动器来激发。此外，与具有刚性连杆和普通执行器的机器人相比，软弯曲执行器在外力存在下的连续变形使建模更加复杂。因此，引入一个合适的数学框架来准确描述这些执行器的机械行为仍然是一个挑战。在这项研究中，提出了一种基于 Neo-Hookean 材料模型的解析静态模型。通过采用所提出的模型，提取了执行器形状和入口执行压力之间的非线性关系。接下来，通过欧拉-伯努利梁理论，研究了外力对执行器配置的影响。最后，给出了实验结果来验证所提出的理论模型。在这方面，首先，适当地验证了自由运动中的致动器非线性行为。然后，分析了存在两个常规外力（称为跟随和固定方向）的执行器配置。