Bio-inspired soft robotic systems: Exploiting environmental interactions using embodied mechanics and sensory coordination

Despite the widespread development of highly intelligent robotic systems exhibiting great precision, reliability, and dexterity, robots remain incapable of performing basic manipulation tasks that humans take for granted. Manipulation in unstructured environments continues to be acknowledged as a significant challenge. Soft robotics, the use of less rigid materials in robots, has been proposed as one means of addressing these limitations. The technique enables more compliant interactions with the environment, allowing for increasingly adaptive behaviours better suited to more human-centric applications. Embodied intelligence is a biologically inspired concept in which intelligence is a function of the entire system, not only the controller or `brain'. This thesis focuses on the use of embodied intelligence for the development of soft robots, with a particular focus on how it can aid both perception and adaptability. Two main hypotheses are raised: first, that the mechanical design and fabrication of soft-rigid hybrid robots can enable increasingly environmentally adaptive behaviours, and second, that sensing materials and morphology can provide intelligence that assists perception through embodiment. A number of approaches and frameworks for the design and development of embodied systems are presented that address these hypotheses. It is shown how embodiment in soft sensor morphology can be used to perform localised processing and thereby distribute the intelligence over the body of a system. Specifically in soft robots, sensor morphology utilises the directional deformations created by interactions with the environment to aid in perception. Building on and formalising these ideas, a number of morphology-based frameworks are proposed for detecting different stimuli. The multifaceted role of materials in soft robots is demonstrated through the development of materials capable of both sensing and changes in material property. Such materials provide additional functionality beyond their integral scaffolding and static mechanical characteristics. In particular, an integrated material has been created exhibiting both sensing capabilities and also variable stiffness and `tack’ force, thereby enabling complex single-point grasping. To maximise the intelligence that can be gained through embodiment, a design approach to soft robots, `soft-rigid hybrid' design is introduced. This approach exploits passive behaviours and body dynamics to provide environmentally adaptive behaviours and sensing. It is leveraged by multi-material 3D printing techniques and novel approaches and frameworks for designing mechanical structures. The findings in this thesis demonstrate that an embodied approach to soft robotics provides capabilities and behaviours that are not currently otherwise achievable. Utilising the concept of `embodiment' results in softer robots with an embodied intelligence that aids perception and adaptive behaviours, and has the potential to bring the physical abilities of robots one step closer to those of animals and humans.EPSR

Origami-inspired kinematic morphing surfaces

In the past decades, an emerging technology has tried to build robots from soft materials to mimic living organisms in nature. Despite the flexibility and adaptability offered by such robots, the soft materials introduce very high or even infinite degrees of freedom (DoFs). It is thus challenging to achieve controllable shape changes on soft materials, which are essential for robots to carry out their functions. Many material-based approaches have been attempted to constrain the excessive DoFs of soft materials, so that they can bend, stretch, or twist as desired. In most applications, considering that only limited mobility is required to perform certain tasks, it would also be feasible to employ mechanical coupling to remove unwanted motions. To achieve this, engineers resort to origami techniques to design predictable and controllable robotic structures. However, most origami-inspired robots are built from existing patterns, where the material thickness is always neglected. Using zero-thickness sheets restricts the modelling accuracy, fabrication flexibility, and motion possibility. A recent study reveals that considering material thickness can further reduce the overall DoFs of origami, since its mechanical model is often overconstrained and differs significantly from that of the zero-thickness one. The novel structures with thickness, known as thick-panel origami, were originally developed for space use and are not accessible to roboticists. Hence, a thorough investigation is needed to develop thick-panel origami targeting robotic applications. This thesis is thus centred on two aspects. The first is to systematically design thick-panel origami for shape-changing, namely morphing surfaces. The second part extends selected surfaces into the design of intelligent robots, with the aim of simplified design, actuation, and control. The main achievements of this research are as follows. Firstly, a systematic design methodology is proposed to map thick-panel origami with 6R spatial overconstrained linkages. A library of morphing units whose thicknesses are uniform and not negligible is thus uncovered. Morphing surfaces, which are the tessellations or assemblies of morphing units, are then demonstrated to achieve common soft material behaviours, including bending, expanding, and twisting. Complex motions such as wrapping and curling are also presented. The mobility of these surfaces is restricted to one, while bifurcations may exist for extra motion possibilities. Secondly, a robotic gripper is designed from the wrapping surface. By exploiting the bifurcation and compliance of the surface, the proposed gripper has achieved a balance between motion dexterity and control complexity, aiming to solve the control challenges of grasping and manipulation. More specifically, the gripper can grasp objects of various shapes with one motor and conduct manipulations with only two control inputs, as opposed to many current end effectors that can only grasp or need around 20 actuators for manipulation tasks. On top of this, the gripper can be 3D-printed with ease, largely streamlining the mechanical design and fabrication process. Lastly, a reconfigurable robot is demonstrated on the curling surface to mimic a millipede's morphology. The robot can not only morph into a coil but also reconfigure into wave-like and triangular shapes. The reconfigurability is achieved by utilising the kinematic bifurcations of the surface without increasing the system's overall DoF. The design is also free from module disconnection and reconnection for new configurations, making the system more robust. The proof-of-concept robotic study has showcased the potential of maintaining reconfigurability with a relatively straightforward control strategy

A Bioinspired Bidirectional Stiffening Soft Actuator for Multimodal, Compliant, and Robust Grasping

The stiffness modulation mechanism for soft robotics has gained considerable attention to improve deformability, controllability, and stability. However, for the existing stiffness soft actuator, high lateral stiffness and a wide range of bending stiffness are hard to be provided at the same time. This paper presents a bioinspired bidirectional stiffening soft actuator (BISA) combining the air-tendon hybrid actuation (ATA) and a bone-like structure (BLS). The ATA is the main actuation of the BISA, and the bending stiffness can be modulated with a maximum stiffness of about 0.7 N/mm and a maximum magnification of 3 times when the bending angle is 45 deg. Inspired by the morphological structure of the phalanx, the lateral stiffness can be modulated by changing the pulling force of the BLS. The lateral stiffness can be modulated by changing the pulling force to it. The actuator with BLSs can improve the lateral stiffness about 3.9 times compared to the one without BLSs. The maximum lateral stiffness can reach 0.46 N/mm. And the lateral stiffness can be modulated decoupling about 1.3 times (e.g., from 0.35 N/mm to 0.46 when the bending angle is 45 deg). The test results show the influence of the rigid structures on bending is small with about 1.5 mm maximum position errors of the distal point of actuator bending in different pulling forces. The advantages brought by the proposed method enable a soft four-finger gripper to operate in three modes: normal grasping, inverse grasping, and horizontal lifting. The performance of this gripper is further characterized and versatile grasping on various objects is conducted, proving the robust performance and potential application of the proposed design method

Hybrid soft-rigid deployable structure inspired by thick-panel origami

Recently, the techniques of origami have become the subject of scientific research. Such methods of folding plates are suitable for practical engineering applications. This paper proposes a novel structure, inspired by thick-panel origami, with hybrid rigid bodies and flexible hinges. Able to be expanded, flipped, and rotated, the waterbomb origami pattern has been chosen to produce a large number of configurations. The mechanism and motion analysis of a single unit and its basic assembly are conducted theoretically and also simulated. An additive fabrication method based on 3D printing makes it a one-step process to achieve a balance between rigidity and flexibility in the structure. Different configurations are demonstrated in three assemblies that exhibit good transformability, reconfigurability, and scalability. With the expansion/packaging ratio ranging from 0.11 to 7.2 in a modular unit, a mechanical metamaterial of negative Poisson’s ratio can be obtained at any spatial size. In addition, our design’s potential for robotic applications is also validated by an adaptable gripper with tendon-driven systems

Soft manipulators and grippers: A review

Soft robotics is a growing area of research which utilizes the compliance and adaptability of soft structures to develop highly adaptive robotics for soft interactions. One area in which soft robotics has the ability to make significant impact is in the development of soft grippers and manipulators. With an increased requirement for automation, robotics systems are required to perform task in unstructured and not well defined environments; conditions which conventional rigid robotics are not best suited. This requires a paradigm shift in the methods and materials used to develop robots such that they can adapt to and work safely in human environments. One solution to this is soft robotics, which enables soft interactions with the surroundings while maintaining the ability to apply significant force. This review paper assesses the current materials and methods, actuation methods and sensors which are used in the development of soft manipulators. The achievements and shortcomings of recent technology in these key areas are evaluated, and this paper concludes with a discussion on the potential impacts of soft manipulators on industry and society

Actuation Technologies for Soft Robot Grippers and Manipulators: A Review

Purpose of Review The new paradigm of soft robotics has been widely developed in the international robotics community. These robots being soft can be used in applications where delicate yet effective interaction is necessary. Soft grippers and manipulators are important, and their actuation is a fundamental area of study. The main purpose of this work is to provide readers with fast references to actuation technologies for soft robotic grippers in relation to their intended application. Recent Findings The authors have surveyed recent findings on actuation technologies for soft grippers. They presented six major kinds of technologies which are either used independently for actuation or in combination, e.g., pneumatic actuation combined with electro-adhesion, for certain applications. Summary A review on the latest actuation technologies for soft grippers and manipulators is presented. Readers will get a guide on the various methods of technology utilization based on the application

A 3D-Printed Omni-Purpose Soft Gripper

Numerous soft grippers have been developed based on smart materials, pneumatic soft actuators, and underactuated compliant structures. In this article, we present a three-dimensional (3-D) printed omni-purpose soft gripper (OPSOG) that can grasp a wide variety of objects with different weights, sizes, shapes, textures, and stiffnesses. The soft gripper has a unique design that incorporates soft fingers and a suction cup that operate either separately or simultaneously to grasp specific objects. A bundle of 3-D-printable linear soft vacuum actuators (LSOVA) that generate a linear stroke upon activation is employed to drive the tendon-driven soft fingers. The support, fingers, suction cup, and actuation unit of the gripper were printed using a low-cost and open-source fused deposition modeling 3-D printer. A single LSOVA has a blocked force of 30.35 N, a rise time of 94 ms, a bandwidth of 2.81 Hz, and a lifetime of 26 120 cycles. The blocked force and stroke of the actuators are accurately predicted using finite element and analytical models. The OPSOG can grasp at least 20 different objects. The gripper has a maximum payload-to-weight ratio of 7.06, a grip force of 31.31 N, and a tip blocked force of 3.72 N

The KIT swiss knife gripper for disassembly tasks: a multi-functional gripper for bimanual manipulation with a single arm

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This work presents the concept of a robotic gripper designed for the disassembly of electromechanical devices that comprises several innovative ideas. Novel concepts include the ability to interchange built-in tools without the need to grasp them, the ability to reposition grasped objects in-hand, the capability of performing classic dual arm manipulation within the gripper and the utilization of classic industrial robotic arms kinematics within a robotic gripper. We analyze state of the art grippers and robotic hands designed for dexterous in-hand manipulation and extract common characteristics and weak points. The presented concept is obtained from the task requirements for disassembly of electromechanical devices and it is then evaluated for general purpose grasping, in-hand manipulation and operations with tools. We further present the CAD design for a first prototype.Peer ReviewedPostprint (author's final draft

Design of Soft Composite Finger with Adjustable Joint Stiffness

This research presents the design of a soft composite finger with tunable joint stiffness. The composite finger, made from two different types of silicone, has hybrid actuation principle combining tendon and pneumatic actuation schemes. Tendons control the finger shape in a prescribed direction to demonstrate discrete bending behavior due to different material moduli, similar to the human finger’s discrete bending. Whereas, pneumatic actuation changes the stiffness of joints using air chambers. The feasibility of adjustable stiffness joints is proven using both the parallel spring-damper model and experiments, demonstrating the stiffening effect when pressurized. A set of experiments were also conducted on fingers with four different chamber designs to see the effect of chamber shape on stiffening and the discrete bending capability of the finger. These stiffened fingers lead to firm grasp as they constrain the object better and apply higher grasping force. The gripper made up of soft composite fingers can grasp objects of various sizes, shapes and in different orientations