纺织基软体机器人结构设计与驱动性能研究

Study on the structural design and actuation performance of textile-based soft robotics

针对现有软体气动机器人制备成本高、设计灵活性差、功率密度低、控制技术复杂等问题,文章以鞘芯结构的涤纶∕氨纶弹性纱为基材编织针织罗纹组织,以涤纶纱为纬向衬垫纱间隔织入,形成力学各向异性的针织衬纬组织,并将该衬纬组织作为包覆层与气囊内胆装配,实现具有高致动应变、低能量耗散的高性能纺织基气动机器人开发。文章通过力学性能和驱动变形测试,表征分析了衬纬组织织物层的各向异性力学特征和针脚排列方式等因素对软体机器人驱动性能、变形特征、输出力和运动状态的影响规律。结果表明:纺织基软体机器人展现了优良的弯曲应变(弯曲曲率可达0.27 cm^(-1)),高的驱动力输出(13 N∕kg)。此外,开发的纺织基气动机器人具有低成本、设计灵活快捷、操控简单等优势,可通过编织结构设计和针脚方向的配置实现多模式的复杂变形,在可穿戴医疗康复训练设备和软体抓取器件等领域具有可观的应用前景。

Robots contribute a significant part of smart living and production in modern society.Compared to rigid robots composed of hard materials,soft pneumatic robotics constructed with flexible materials are more lightweight and flexible,offering greater compliance,environmental adaptability,and safety when interacting with humans and fragile objects.Therefore,they hold considerable promise in areas such as medical rehabilitation,human-robot interaction,and operations in unstructured complex environments.However,existing soft pneumatic robots constructed from multi-directional and highly deformable membrane materials often suffer from issues such as low power-to-weight ratio,complex control and fabrication processes,and poor skin-friendliness.Textile materials,as a category of typical fiber-based soft materials,offer opportunities for multi-scale controllable structural design.They possess characteristics like a solid phase with the ability to smoothly deform with multiple curvatures and high strength combined with flexibility.Consequently,they have the potential to enhance the power output,controllability,and applications of soft robots in the field of intelligent wearables.On this basis,the multi-scale design strategy of textile structure was proposed in this study,and textile-based soft actuators with excellent performance were developed,so as to promote the practical applications of pneumatic actuators.In this study,the mechanical properties of the knitted fabric layer of the textile-based actuators were characterized,and the knitted layer with laying-in yarns and anisotropic mechanical behavior was designed to improve the actuating efficiency of the actuators.Furthermore,a comparison was made between the bending curvatures of soft robotics made by conventional knitting-based actuators and modified knitting-based actuators with laying-in stitches.A modified knitted architecture with laying-in yarns was pioneered to fabricate textile-based actuators.The loop yarn of the modified knitted fabric possessed core-sheath structure by wrapping spandex filaments with polyester fibers,so that high elasticity was achieved.The laying-in yarns were made of polyester fibers to endow the yarns with relatively low elasticity.The modified knitted fabric shows superanisotropic mechanical performance.Specifically,the Young’s modulus in the direction of laying-in yarns is up to 145 kPa,while the Young’s modulus in the orthogonal direction is only 1.1 kPa.Such an isotropic mechanical property of the designed fabric enhances the deformation of the actuator along fabric’s elastic direction but restricts the deformation in inelastic direction,endowing the fabricated actuator with high energy efficiency and blocking forces.A large bending curvature of 0.27 cm^(-1)is achieved under a low applied pressure(60 kPa).This bending actuation strain is much larger than that of actuators fabricated by conventional knitted fabrics.The multimode movements are achieved by programming the Young’s modulus of the fabrics to form bending,curling and coiling deformations.For the given size of the actuators,the bending curvature of the actuators ranges from 0.25 cm^(-1)to about 0.13 cm^(-1)when the Young’s modulus varies from 0.05 MPa to 5.6 MPa.Also,the bending curvature can be tuned by the dimension of the actuators,and a conical actuator can possess variable bending curvatures along its generatrix.The actuators can be used to assist arm motion,displaying high specific work,as indicated by the high actuation strain(over 90°)and high weight ratio between the arm weight(0.225 kg)and actuator weight(0.019 kg).Moreover,the actuators can also be assembled to produce soft grippers to grip and then lift objects by a sequence deformation of the actuators driven by a monotonous air pressure source,and the gripping force can be easily tuned by controlling the supplied pressures.Unlike the conventional strategy to integrate different components into actuators,a modified knitted architecture is used to fabricate actuators with superior actuation performance based on the hierarchical structure design of textiles.The proposed textile-based soft robotics fabricated based on the modified knitted fabric show a good bending actuation strain at low applied pressure,a large blocking force and high specific work.Also,the deformation of the actuators can be easily programmed by tuning the Young’s modulus and dimensional size based on the hierarchical textile manufacturing process,and thus the actuators possess low-cost and easy-fabrication features.The developed textile-based actuators are promising for diverse applications in soft robotics,medical rehabilitation training,soft gripper and other areas that are not possible with conventional linkage rigid actuators.This approach can be a paradigm to put forward structure innovation of textile-based actuators.