Augmented flexibility for design, actuation and control of soft robots

Abstract

Soft robotics has become a crucial research topic as it utilizes unconventional soft mate-rials and their according morphologies in a robotic system. Such hyperelastic material with underlying properties, including stiffness, elasticity and geometrical parameters, enables the robotic system to perform much more remarkable functions compared with traditional rigid robots. Plenty of methods have been proposed by the researchers vary-ing from design of soft actuators, creation of smart soft materials, entirely soft mecha-nisms, and hybrid soft-rigid mechanisms, etc. However, speculations and explorations are still to be conducted for this field as challenges exist, in terms of more functional soft actuators, systematic investigation on the structure of a soft mechanism as well as the interactions with environments by soft matter’s flexibility on different soft robotic actuation. To this end, this thesis aims to address some of the limitations based on certain applications by proposing a novel Augmented Flexibility (AF) concept. AF concept mainly contains three aspects, which are design of soft mechanism and its structural layout, actuation and control framework, and interactions of the soft mecha-nism with its surroundings, by utilizing the promising properties brought by the flex-ibility of hyperelastic materials. For the fundamental unit of a soft robotic system, which is the soft actuator, in total three types of pressure-driven soft actuators have been designed, and the fabrication process is exploited in detail, including bellows shape soft actuators with V-shape-structure constraints, and soft actuators with sepa-rated/embedded fiber reinforcement. All the three types of actuator can be fabricated as an independent unit for convenient usage and assembling. Besides, the structures of a soft mechanism from linear, planar to spatial layout have been explored formed by mentioned actuators. In addition, novel soft components have been designed, that are flexible segmented fin, compensating soft bladders and flow regulative soft duct, allowing for modifying the actuation and control process and novel interactions with the surroundings to achieve multiple purposes of the soft robotic system. Finally, the designed AF systems have been validated with specific application sce-narios, which are exoskeleton wearable device and underwater robots. The exoskele-ton wearable device utilizes the planar structure with bellows shape soft actuators to achieve complex planar trajectory tracking, enabling the device to imitate the real hu-man’s jaw movement, paving the way for TMD rehabilitation. The underwater applica-tion includes three types, thereinto two types are biomimetic ones. Ostraciidae-inspired linear 2-segment fin with a soft flexible link increases the resonance frequency by 178%and the thrust force by 12%, widening the control range. The soft-bladder-based hy-draulic framework improves the dynamic response allowing for dexterous, powerful and fast manipulation. And the Cephalopods-inspired soft robotic siphon enables flow rate regulation from 100% to 0, flow vectoring and a burst effect of exceeding constant flow rate by 50%, paving the way for underwater jetting propulsion. The validations have proved that the AF concept brings novel insight into the design of a soft robotic system and achieves augmentation on various functions and purposes.