Soft Legged Wheel-Based Robot with Terrestrial Locomotion Abilities

In recent years robotics has been influenced by a new approach, soft-robotics, bringing the idea that safe interaction with user and more adaptation to the environment can be achieved by exploiting easily deformable materials and flexible components in the structure of robots. In 2016, the soft-robotics community has promoted a new robotics challenge, named RoboSoft Grand Challenge, with the aim of bringing together different opinions on the usefulness and applicability of softness and compliancy in robotics. In this paper we describe the design and implementation of a terrestrial robot based on two soft legged wheels. The tasks predefined by the challenge were set as targets in the robot design, which finally succeeded to accomplish all the tasks. The wheels of the robot can passively climb over stairs and adapt to slippery grounds using two soft legs embedded in their structure. The soft legs, fabricated by integration of soft and rigid materials and mounted on the circumference of a conventional wheel, succeed to enhance its functionality and easily adapt to unknown grounds. The robot has a semi stiff tail that helps in the stabilization and climbing of stairs. An active wheel is embedded at the extremity of the tail in order to increase the robot maneuverability in narrow environments. Moreover two parallelogram linkages let the robot to reconfigure and shrink its size allowing entering inside gates smaller than its initial dimensions

A Review of Cooperative Actuator and Sensor Systems Based on Dielectric Elastomer Transducers

This paper presents an overview of cooperative actuator and sensor systems based on dielectric elastomer (DE) transducers. A DE consists of a flexible capacitor made of a thin layer of soft dielectric material (e.g., acrylic, silicone) surrounded with a compliant electrode, which is able to work as an actuator or as a sensor. Features such as large deformation, high compliance, flexibility, energy efficiency, lightweight, self-sensing, and low cost make DE technology particularly attractive for the realization of mechatronic systems that are capable of performance not achievable with alternative technologies. If several DEs are arranged in an array-like configuration, new concepts of cooperative actuator/sensor systems can be enabled, in which novel applications and features are made possible by the synergistic operations among nearby elements. The goal of this paper is to review recent advances in the area of cooperative DE systems technology. After summarizing the basic operating principle of DE transducers, several applications of cooperative DE actuators and sensors from the recent literature are discussed, ranging from haptic interfaces and bio-inspired robots to micro-scale devices and tactile sensors. Finally, challenges and perspectives for the future development of cooperative DE systems are discussed

Actionneurs en polymère cristallins liquides poreux

Les actionneurs en matériaux souples possèdent des caractéristiques distinctives qui les rendent utiles pour de nombreuses applications. Parmi les matériaux souples à des fins d'actionnement, les élastomères cristallins liquides (LCE - abréviation en anglais) sont particulièrement prometteurs en raison de leur grande déformation réversible, de leur im-portante force mécanique lors de l’actionnement, et de leurs mouvements diversifiés dé-clenchés par des stimuli. Dans ce domaine de recherche, la plupart des efforts ont été con-sacrés à la conception de nouvelles structures moléculaires de LCE, au contrôle de l'ali-gnement LC qui est crucial pour la déformation, et à l'ingénierie des structures ou archi-tectures d'actionneurs. Toutefois, tant pour la recherche fondamentale que pour les appli-cations, il est important de développer de nouvelles approches qui, sans changer les struc-tures du LCE et de l'actionneur et en utilisant le même alignement LC, peuvent donner lieu à de nouvelles fonctions d'actionnement. C’est le but de la présente thèse qui porte sur le développant d’un nouveau type d’actionneurs, à savoir, actionneurs poreux en LCE. Afin de fabriquer des actionneurs LCE poreux, nous avons développé une méthode simple et efficace qui consiste à, successivement, disperser des nanoparticules inorganiques (celles du CaCO3 et du MOF : metal-organic framework) dans un film LCE, préparer l'ac-tionneur par étirement mécanique pour l'alignement des mésogènes et irradiation à la lu-mière UV pour la réticulation du polymère, et enlever les nanoparticules inorganiques de la matrice LCE par voie de gravure chimique. Nos études sur les actionneurs LCE poreux résultants ont non seulement révélé de nouvelles fonctions ou fonctionnalités d'actionne-ment, mais aussi démontré leur potentiel pour des applications. Premièrement, bien que le LCE utilisé soit hydrophobe, son actionneur poreux est capable d’absorber une grande quantité d'eau et gonfler comme un hydrogel. L’étude montre que ce changement de propriété est probablement causé par des ions restants dans l'actionneur gravé, ce qui améliore l'affinité entre les surfaces des pores et les molécules d'eau. Malgré la présence d'eau, l'alignement des mésogènes peut être préservé en grande partie. Par con-séquent, l'actionneur LCE poreux gonflé peut présenter une déformation réversible par changement de volume lors de l'absorption et de la désorption d'eau (comme un hydrogel) ou par une transition de phase ordre-désordre des mésogènes induite thermiquement (une caractéristique de LCE). Des comportements en actionnement particuliers peuvent être obtenus en combinant ces deux mécanismes d'actionnement différents. Cette nouvelle fonctionnalité est abordée dans les chapitres 2 et 4. Deuxièmement, le gonflement important de l’actionneur poreux dans l'eau offre un moyen efficace pour introduire dans l'actionneur un additif dissous dans l’eau, et après séchage, l’additive ainsi encapsulé par les canaux de pores peut doter l’actionneur d'une fonction au-delà de l’actionnement. Nous avons démontré une nouvelle fonctionnalité dite « recon-figurabilité des fonctions » en chargeant, lavant et rechargeant trois différents additifs fonctionnels dans un même actionneur LCE poreux : un liquide ionique (IL) pour la con-ductivité ionique, un colorant photothermique pour le mouvement piloté par la lumière et un fluorophore pour l'émission de couleur. Cette nouvelle fonctionnalité est rapportée au chapitre 2. De plus, nous avons utilisé un actionneur LCE poreux contenant un liquide ionique (PLCE-IL) pour démontrer séparément la détection et l'actionnement qui sont normalement deux fonctions obtenues avec deux classes de matériaux : matériaux défor-mables pour détection par voir électrique et matériaux souples pour actionnement déclen-ché par des stimuli. D'une part, lors de la transition de phase ordre-désordre des méso-gènes alignés, le PLCE-IL se comporte comme un actionneur typique capable de changer sa forme de manière réversible et peut être utilisé pour assembler un robot souple alimenté par la lumière. D'autre part, à des températures en-dessous de la transition de phase, le PLCE-IL est un élastomère qui peut supporter et détecter de grandes déformations de di-vers modes ainsi que des changements de conditions environnementales en signalant la variation de résistance électrique correspondante. L'utilisation collective de ces deux fonc-tions intégrées dans un dispositif a également été montrée. Ce travail est discuté au cha-pitre 3. Finalement, rapporté au chapitre 4, nous avons fait une découverte inattendue en étudiant les actionneurs LCE chargés de MOF (LCE-MOF). Après gravure chimique pour le retrait des cristaux MIL-88A, l'actionneur poreux devient magnétiquement sensible, réagissant à un aimant proche. L’analyse suggère la formation in situ de nanoparticules magnétiques de Fe3O4 due à la gravure chimique et à l'irradiation par la lumière UV. En plus des fonc-tionnalités susmentionnées, un actionneur poreux magnétique peut être dirigé par un ai-mant d’entreprendre des mouvements multidirectionnels à la surface de l'eau. En plus, la présence des nanoparticules de Fe3O4 donne un important effet photothermique qui peut être mis à profit pour obtenir un mouvement efficace de l'actionneur poreux alimenté par la lumière.Abstract: Soft materials-based actuators possess distinctive characteristics making them useful for applications in many fields. Among the soft materials for actuation, liquid crystalline elas-tomers (LCEs) stand out owing to their unique actuation features including large shape deformation, high mechanical forces, and diversiform movements driven by variety of stimuli. In terms of material research in the field of LCE actuators, understandably, most effort has been dedicated to designing new molecular structures of LCE, controlling LC alignment, and engineering actuator structures or architectures. However, it is of funda-mental interest to develop new approaches that, without changing the LCE and actuator structures and using the same LC alignment, can give rise to new actuation functions. The purpose of the present thesis is to address this important issue by developing porous LCE actuators. To fabricate porous LCE actuators, we developed a simple and efficient direct templating method that consists in dispersing inorganic nanoparticles, like CaCO3 and MIL-88A (metal-organic framework, MOF) in LCE film, preparing the actuator through mechanical stretching for alignment of mesogens and UV light irradiation for polymer chain crosslink-ing, and subsequently removing inorganic nanoparticles from the LCE matrix by means of chemical etching. Our studies of porous LCE actuators not only revealed a number of new actuation functions but also demonstrated the potential for applications. First, although the LCE used is hydrophobic, porous LCE actuators can absorb large amounts of water and swell like hydrogel, which is likely due to ions remained in the etched actuator leading to improved affinity between pore surfaces and water molecules. Despite the presence of water, the alignment of mesogens can be preserved to a great extent. Con-sequently, swollen porous LCE actuator can exhibit reversible deformation through either volume change upon water absorption and desorption (like hydrogel) or thermally induced order-disorder phase transition of the mesogens (characteristic of LCE). Unusual actuation behaviors can be obtained by combining these two different actuation mechanisms. This new feature is discussed in Chapters 2 and 4. Secondly, by dissolving a given active additive in water, the large swelling of porous LCE actuator in water provides an effective means to introduce this additive in the actuator and thus endow it with a beyond-actuation function enabled by the additive embedded in pore channels after drying. We demonstrated the new feature of function reconfigurability by loading, washing out and reloading different functional additives in a same porous LCE actuator: an ionic liquid (IL) for ionic conductivity, a photothermal dye for light-driven movement and a fluorophore for color emission. This new feature is reported in Chapter 2. Furthermore, we went on to use porous LCE actuator containing ionic liquid (PLCE-IL) for separate sensing and actuation that are normally two functions obtained with two clas-ses of materials: electrically responsive and deformable materials for sensing and soft ac-tive materials for stimuli-triggered actuation. On one hand, upon the order–disorder phase transition of aligned mesogens, PLCE-IL behaves like a typical actuator capable of reversi-ble shape change and can be used to assemble light-fueled soft robot. On the other hand, at temperatures below the phase transition, PLCE-IL is an elastomer that can sustain and sense large deformations of various modes as well as environmental condition changes by reporting the corresponding electrical resistance variation. The collective use of the two functions integrated in one device was also shown. This work, discussed in Chapter 3, shows that electrically responsive porous LCEs are a potential materials platform that of-fers possibilities for merging deformable electronic and actuation applications. Finally, reported in Chapter 4, we made an unexpected finding in studying MOF-loaded LCE actuators (LCE-MOF). After chemical etching for removal of MIL-88A crystals, the porous LCE-MOF actuator becomes magnetically responsive. The characterization results suggest the in-situ formation of magnetic Fe3O4 nanoparticles due to acid etching and UV light irradiation. In addition to the aforementioned features of porous LCE actuators, with a magnetic LCE actuator, a magnet can be used to drive its multi-directional movement on water surface, and the enhanced photothermal effect due to light absorption of Fe3O4 na-noparticles can be taken advantage to achieve efficient light-driven locomotion of the po-rous actuator

DEVELOPMENT OF A NANOCOMPOSITE SENSOR AND ELECTRONIC SYSTEM FOR MONITORING OF LOCOMOTION OF A SOFT EARTHWORM ROBOT

The ability to detect external stimuli and perceive the surrounding areas represents a key feature of modern soft robotic systems, used for exploration of harsh environments. Although people have developed various types of biomimetic soft robots, no integratedsensor system is available to provide feedback locomotion. Here, a stretchable nanocomposite strain sensor with integrated wireless electronics to provide a feedbackloop locomotion of a soft robotic earthworm is presented. The ultrathin and soft strain sensor based on a carbon nanomaterial and a low-modulus silicone elastomer allows for a seamless integration with the body of the soft robot, accommodating large strains derived from bending, stretching, and physical interactions with obstacles. A scalable, costeffective, screen-printing method manufactures an array of strain sensors that are conductive and stretchable over 100% with a gauge factor over 38. An array of stretchable nanomembrane interconnectors enables a reliable connection between soft strain sensors and wireless electronics, while tolerating the robot’s multi-modal movements. A set of computational and experimental studies of soft materials, stretchable mechanics, and hybrid packaging provides key design factors for a reliable, nanocomposite sensor system. The miniaturized wireless circuit, embedded in the robot joint, offers a real-time monitoring of strain changes on the earthworm skin. Collectively, the soft sensor system shows a great potential to be integrated with other flexible, stretchable electronics for applications in soft robotics, wearable devices, and human-machine interfaces.M.S

Design and analysis of origami-inspired structures

This work focuses on creating novel structures by combining elements of common origami patterns. Multiple different types of physical and computer models are implemented to represent and analyze the structures. These structures have a broad range of potential applications, such as architecture, soft robotics, and aerospace. A combined Miura and EggBox pattern is presented. The combined unit cell for the sheet is parameterized, the Poisson ratio is calculated, and the sheets are 3D modeled using Solid Edge. Tubes constructed from the combined pattern are computer modeled and a static analysis is performed using the MERLIN2 software package in GNU Octave. These tubes can then be woven into cellular structures, some examples of which are 3D modeled and discussed. Also presented are many different combinations of the Miura and Resch unit cells. Crease patterns were drawn in Inkscape and computer folded using Origami Simulator. Some of these tessellations were found in literature but others were not. In addition to traditional origami paper folding, other fabrication methods for folded structures are presented, such as selective laser sintering (SLS) 3D printing and laser cutting of plastic sheets. Some software tools were developed and implemented to aid design.Includes bibliographical references

Design and Control of Compliant Tensegrity Robots Through Simulation and Hardware Validation

To better understand the role of tensegrity structures in biological systems and their application to robotics, the Dynamic Tensegrity Robotics Lab at NASA Ames Research Center has developed and validated two different software environments for the analysis, simulation, and design of tensegrity robots. These tools, along with new control methodologies and the modular hardware components developed to validate them, are presented as a system for the design of actuated tensegrity structures. As evidenced from their appearance in many biological systems, tensegrity ("tensile-integrity") structures have unique physical properties which make them ideal for interaction with uncertain environments. Yet these characteristics, such as variable structural compliance, and global multi-path load distribution through the tension network, make design and control of bio-inspired tensegrity robots extremely challenging. This work presents the progress in using these two tools in tackling the design and control challenges. The results of this analysis includes multiple novel control approaches for mobility and terrain interaction of spherical tensegrity structures. The current hardware prototype of a six-bar tensegrity, code-named ReCTeR, is presented in the context of this validation

3D printed pneumatic soft actuators and sensors: their modeling, performance quantification, control and applications in soft robotic systems

Continued technological progress in robotic systems has led to more applications where robots and humans operate in close proximity and even physical contact in some cases. Soft robots, which are primarily made of highly compliant and deformable materials, provide inherently safe features, unlike conventional robots that are made of stiff and rigid components. These robots are ideal for interacting safely with humans and operating in highly dynamic environments. Soft robotics is a rapidly developing field exploiting biomimetic design principles, novel sensor and actuation concepts, and advanced manufacturing techniques. This work presents novel soft pneumatic actuators and sensors that are directly 3D printed in one manufacturing step without requiring postprocessing and support materials using low-cost and open-source fused deposition modeling (FDM) 3D printers that employ an off-the-shelf commercially available soft thermoplastic poly(urethane) (TPU). The performance of the soft actuators and sensors developed is optimized and predicted using finite element modeling (FEM) analytical models in some cases. A hyperelastic material model is developed for the TPU based on its experimental stress-strain data for use in FEM analysis. The novel soft vacuum bending (SOVA) and linear (LSOVA) actuators reported can be used in diverse robotic applications including locomotion robots, adaptive grippers, parallel manipulators, artificial muscles, modular robots, prosthetic hands, and prosthetic fingers. Also, the novel soft pneumatic sensing chambers (SPSC) developed can be used in diverse interactive human-machine interfaces including wearable gloves for virtual reality applications and controllers for soft adaptive grippers, soft push buttons for science, technology, engineering, and mathematics (STEM) education platforms, haptic feedback devices for rehabilitation, game controllers and throttle controllers for gaming and bending sensors for soft prosthetic hands. These SPSCs are directly 3D printed and embedded in a monolithic soft robotic finger as position and touch sensors for real-time position and force control. One of the aims of soft robotics is to design and fabricate robotic systems with a monolithic topology embedded with its actuators and sensors such that they can safely interact with their immediate physical environment. The results and conclusions of this thesis have significantly contributed to the realization of this aim

Continuum Mechanical Models for Design and Characterization of Soft Robots

The emergence of ``soft'' robots, whose bodies are made from stretchable materials, has fundamentally changed the way we design and construct robotic systems. Demonstrations and research show that soft robotic systems can be useful in rehabilitation, medical devices, agriculture, manufacturing and home assistance. Increasing need for collaborative, safe robotic devices have combined with technological advances to create a compelling development landscape for soft robots. However, soft robots are not yet present in medical and rehabilitative devices, agriculture, our homes, and many other human-collaborative and human-interactive applications. This gap between promise and practical implementation exists because foundational theories and techniques that exist in rigid robotics have not yet been developed for soft robots. Theories in traditional robotics rely on rigid body displacements via discrete joints and discrete actuators, while in soft robots, kinematic and actuation functions are blended, leading to nonlinear, continuous deformations rather than rigid body motion. This dissertation addresses the need for foundational techniques using continuum mechanics. Three core questions regarding the use of continuum mechanical models in soft robotics are explored: (1) whether or not continuum mechanical models can describe existing soft actuators, (2) which physical phenomena need to be incorporated into continuum mechanical models for their use in a soft robotics context, and (3) how understanding on continuum mechanical phenomena may form bases for novel soft robot architectures. Theoretical modeling, experimentation, and design prototyping tools are used to explore Fiber-Reinforced Elastomeric Enclosures (FREEs), an often-used soft actuator, and to develop novel soft robot architectures based on auxetic behavior. This dissertation develops a continuum mechanical model for end loading on FREEs. This model connects a FREE’s actuation pressure and kinematic configuration to its end loads by considering stiffness of its elastomer and fiber reinforcement. The model is validated against a large experimental data set and compared to other FREE models used by roboticists. It is shown that the model can describe the FREE’s loading in a generalizable manner, but that it is bounded in its peak performance. Such a model can provide the novel function of evaluating the performance of FREE designs under high loading without the costs of building and testing prototypes. This dissertation further explores the influence viscoelasticity, an inherent property of soft polymers, on end loading of FREEs. The viscoelastic model developed can inform soft roboticists wishing to exploit or avoid hysteresis and force reversal. The final section of the dissertations explores two contrasting styles of auxetic metamaterials for their uses in soft robotic actuation. The first metamaterial architecture is composed of beams with distributed compliance, which are placed antagonistic configurations on a variety of surfaces, giving ride to shape morphing behavior. The second metamaterial architecture studied is a ``kirigami’’ sheet with an orthogonal cut pattern, utilizing lumped compliance and strain hardening to permanently deploy from a compact shape to a functional one. This dissertation lays the foundation for design of soft robots by robust physical models, reducing the need for physical prototypes and trial-and-error approaches. The work presented provides tools for systematic exploration of FREEs under loading in a wide range of configurations. The work further develops new concepts for soft actuators based on continuum mechanical modeling of auxetic metamaterials. The work presented expands the available tools for design and development of soft robotic systems, and the available architectures for soft robot actuation.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163236/1/asedal_1.pd