Bhat Ajinkya, Jaipurkar Shobhit Sandeep, Low Li Ting, Yeow Raye Chen-Hua
Evolution Innovation Laboratory, National University of Singapore, Singapore, Singapore.
Integrated Science and Engineering Program (ISEP), National University of Singapore, Singapore, Singapore.
Soft Robot. 2023 Oct;10(5):923-936. doi: 10.1089/soro.2022.0089. Epub 2023 Apr 12.
The development of the field of soft robotics has led to the exploration of novel techniques to manufacture soft actuators, which provide distinct advantages for wearable assistive robotics. One subset of these soft pneumatic actuators is conventionally developed from silicone, fabrics, and thermoplastic polyurethane (TPU). Each of these materials in isolation possesses limitations of low-stress capacity, low-design complexity, and high-input pressure requirements, respectively. Combining these materials can overcome some limitations and maintain their desirable properties. In this article, we explore one such composite design scheme using a combination of silicone polymer-based bladder and reconfigurable fabric skin made from an anisotropic extensible fabric. The silicone polymer bladder acts as the hermetic seal, while this skin acts as the constraint. Bending and torsional actuators were designed utilizing the anisotropy of these fabrics. The torsional actuator designs can achieve over 540° of twist, significantly larger than previously reported in the literature, owing to the lower mechanical impedance of the extensible fabrics. Actuators with 360° of bending were also fabricated using this method. In addition, the lack of TPU-backed or inextensible fabrics reduces the actuator's stiffness, leading to lower actuation pressures. Skin-based designs also confer the advantage of modularity, reconfigurability, and the ability to achieve complex motions by tuning the properties of the bladder and the skin. For applications with high-force requirements, such as wearable exoskeletons, we demonstrate the utility of multilayer design schemes. A multilayer bending actuator generated 190 N of force at 100 kPa and was shown to be a candidate for wearable assistive devices. In addition, torsional designs were shown to have utility in practical scenarios such as screwing on a bottle cap and turning knobs. Thus, we present a novel fabric-skin-based design concept that is highly versatile and customizable for various application requirements.
软机器人技术领域的发展促使人们探索制造软致动器的新技术，这为可穿戴辅助机器人带来了显著优势。这些软气动致动器的一个子集传统上是由硅树脂、织物和热塑性聚氨酯（TPU）制成的。单独使用这些材料时，每种材料分别存在低应力能力、低设计复杂性和高输入压力要求等局限性。将这些材料结合起来可以克服一些局限性并保留其理想特性。在本文中，我们探索了一种这样的复合设计方案，该方案使用了基于硅聚合物的气囊和由各向异性可延展织物制成的可重构织物表皮的组合。硅聚合物气囊起到气密密封的作用，而这种表皮起到约束作用。利用这些织物的各向异性设计了弯曲和扭转致动器。由于可延展织物的机械阻抗较低，扭转致动器设计能够实现超过540°的扭转，显著大于文献中先前报道的角度。使用这种方法还制造出了具有360°弯曲的致动器。此外，缺少TPU支撑或不可延展织物降低了致动器的刚度，从而降低了驱动压力。基于表皮的设计还具有模块化、可重构性以及通过调整气囊和表皮的特性实现复杂运动的能力等优点。对于诸如可穿戴外骨骼等具有高力要求的应用，我们展示了多层设计方案的实用性。一个多层弯曲致动器在100kPa压力下产生了190N的力，被证明是可穿戴辅助设备的一个候选方案。此外，扭转设计在诸如拧瓶盖和转动旋钮等实际场景中也显示出了实用性。因此，我们提出了一种新颖的基于织物表皮的设计概念，该概念具有高度的通用性，可针对各种应用需求进行定制。
