Due to their exceptional adaptability, inherent compliance, and high flexibility, soft actuators have significant advantages over traditional rigid actuators in human-machine interaction and in grasping irregular or fragile objects. Most existing soft actuators are designed using preprogramming methods, which schedule complex motions into flexible structures by correctly designing deformation constraints. These constraints restrict undesired deformation, allowing the actuator to achieve the preprogrammed motion when stimulated. Therefore, these actuators can only achieve a certain type of motion, such as extension, bending, or twisting, since it is impossible to adjust the deformation constraints once they are embedded into the structures. In this study, we propose the use of variable stiffness materials, such as shape memory polymer (SMP), in the structural design of soft actuators to achieve variable stiffness constraints. A reconfigurable soft helical actuator with a variable stiffness skeleton is developed based on this concept. The skeleton, made of SMP, is encased at the bottom of a fiber-reinforced chamber. In its high-stiffness state, the SMP constrains the deformation toward the skeleton when the actuator is pressurized. This constraint is removed once the SMP skeleton is heated, endowing the actuator with the ability to switch between bending and helical motion in real-time. A theoretical model is proposed to predict the behavior of the actuator when driven by pressure, and experiments are conducted to verify the model's accuracy. In addition, the influence of different design parameters is investigated based on experimental results, providing reference guidelines for the design of the actuator.

中文翻译：

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具有可变刚度骨架的可重构软螺旋执行器。


由于其卓越的适应性、固有的柔顺性和高灵活性，软执行器在人机交互以及抓取不规则或易碎物体方面比传统刚性执行器具有显着优势。大多数现有的软执行器都是使用预编程方法设计的，通过正确设计变形约束将复杂的运动安排到柔性结构中。这些约束限制了不需要的变形，允许执行器在受到刺激时实现预编程的运动。因此，这些执行器只能实现某种类型的运动，例如伸展、弯曲或扭转，因为一旦嵌入结构中就无法调整变形约束。在本研究中，我们建议在软执行器的结构设计中使用可变刚度材料，例如形状记忆聚合物（SMP），以实现可变刚度约束。基于这一概念，开发了一种具有可变刚度骨架的可重构软螺旋执行器。骨架由 SMP 制成，封装在纤维增强室的底部。在高刚度状态下，当执行器受压时，SMP 会限制向骨架的变形。一旦 SMP 骨架被加热，这种约束就会被消除，从而使执行器能够在弯曲运动和螺旋运动之间实时切换。提出了一个理论模型来预测执行器在压力驱动下的行为，并进行实验来验证该模型的准确性。此外，根据实验结果研究了不同设计参数的影响，为执行器的设计提供参考指导。