206 research outputs found

    Underwater and Surface Aquatic Locomotion of Soft Biomimetic Robot Based on Bending Rolled Dielectric Elastomer Actuators

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    All-around, real-time navigation and sensing across the water environments by miniature soft robotics are promising, for their merits of small size, high agility and good compliance to the unstructured surroundings. In this paper, we propose and demonstrate a mantas-like soft aquatic robot which propels itself by flapping-fins using rolled dielectric elastomer actuators (DEAs) with bending motions. This robot exhibits fast-moving capabilities of swimming at 57mm/s or 1.25 body length per second (BL/s), skating on water surface at 64 mm/s (1.36 BL/s) and vertical ascending at 38mm/s (0.82 BL/s) at 1300 V, 17 Hz of the power supply. These results show the feasibility of adopting rolled DEAs for mesoscale aquatic robots with high motion performance in various water-related scenarios.Comment: 6 Pages, 12 Figures, Published at IROS 202

    Biomimetic Underwater Robots Based on Dielectric Elastomer Actuators

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    Dielectric elastomer actuators (DEAs), a soft actuator technology, hold great promise for biomimetic underwater robots. The high-voltages required to drive DEAs can however make them challenging to use in water. This paper demonstrates a method to create DEA-based biomimetic swimming robots that operate reliably even in conductive liquids. We ensure the insulation of the high-voltage DEA electrodes without degrading actuation performance by laminating silicone layers. A fish and a jellyfish were fabricated and tested in water. The fish robot has a length of 120 mm and a mass of 3.8 g. The jellyfish robot has a 61 mm diameter for a mass of 2.6 g. The measured swimming speeds for a periodic 3 kV drive voltage were 8 mm/s for the fish robot, and 1.5 mm/s for the jellyfish robot

    MODELING AND SIMULATIONS FOR OPTIMIZATION OF MICROFLUIDIC MICROCAPACITOR ARRAYS OF BIOMIMETIC ARTIFICIAL MUSCLES FOR QUIET PROPULSION AND EXOSKELETAL LOCOMOTION

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    The technology that we focused on was the biomimetic actuation of microfluidic microcapacitors, which are electrostatically actuated structures that contract and function like biological muscles. Our thesis aims to find the optimal muscle-to-tendon ratio while expanding both the standard and gap design arrays and to find the respective force-density saturation values so predicted force output can be calculated for muscle fibers of a practical size. We also studied if a 3D virtual object can be a suitable model for the human operators’ examination of the artificial muscle and the optimization of its structure. Our results showed a maximum force density saturation of 8800 Pa and 6700 Pa when simulating the standard and gap array respectively with planar polarity wired artificial muscles. The optimal muscle-to-tendon ratio from the data gathered on the standard array simulations is approximately 9 to 1, meaning 90 percent of the surface area of the XY plane represents microfluidic capacitors and 10 percent is dielectric tendon material. The optimal muscle to tendon ratio from the data gathered on the gap array simulations is approximately 75 to 25, meaning 75 percent of the surface area of the XY plane are microfluidic capacitors, and 25 percent is both the dielectric material and gaps.Office of Naval Research, Arlington, VA, 22203-1995Outstanding ThesisCaptain, United States Marine CorpsCaptain, United States Marine CorpsApproved for public release. Distribution is unlimited

    Inherently Elastic Actuation for Soft Robotics

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    Soft Robots for Ocean Exploration and Offshore Operations: A Perspective

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    The ocean and human activities related to the sea are under increasing pressure due to climate change, widespread pollution, and growth of the offshore energy sector. Data, in under-sampled regions of the ocean and in the offshore patches where the industrial expansion is taking place, are fundamental to manage successfully a sustainable development and to mitigate climate change. Existing technology cannot cope with the vast and harsh environments that need monitoring and sampling the most. The limiting factors are, among others, the spatial scales of the physical domain, the high pressure, and the strong hydrodynamic perturbations, which require vehicles with a combination of persistent autonomy, augmented efficiency, extreme robustness, and advanced control. In light of the most recent developments in soft robotics technologies, we propose that the use of soft robots may aid in addressing the challenges posed by abyssal and wave-dominated environments. Nevertheless, soft robots also allow for fast and low-cost manufacturing, presenting a new potential problem: marine pollution from ubiquitous soft sampling devices. In this study, the technological and scientific gaps are widely discussed, as they represent the driving factors for the development of soft robotics. Offshore industry supports increasing energy demand and the employment of robots on marine assets is growing. Such expansion needs to be sustained by the knowledge of the oceanic environment, where large remote areas are yet to be explored and adequately sampled. We offer our perspective on the development of sustainable soft systems, indicating the characteristics of the existing soft robots that promote underwater maneuverability, locomotion, and sampling. This perspective encourages an interdisciplinary approach to the design of aquatic soft robots and invites a discussion about the industrial and oceanographic needs that call for their application

    SUAS: A Novel Soft Underwater Artificial Skin with Capacitive Transducers and Hyperelastic Membrane

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    The paper presents physical modeling, design, simulations, and experimentation on a novel Soft Underwater Artificial Skin (SUAS) used as tactile sensor. The SUAS functions as an electrostatic capacitive sensor, and it is composed of a hyperelastic membrane used as external cover and oil inside it used to compensate the marine pressure. Simulation has been performed studying and modeling the behavior of the external interface of the SUAS in contact with external concentrated loads in marine environment. Experiments on the external and internal components of the SUAS have been done using two different conductive layers in oil. A first prototype has been realized using a 3D printer. The results of the paper underline how the soft materials permit better adhesion of the conductive layer to the transducers of the SUAS obtaining higher capacitance. The results here presented confirmed the first hypotheses presented in a last work and opened new ways in the large-scale underwater tactile sensor design and development. The investigations are performed in collaboration with a national Italian project named MARIS, regarding the possible extension to the underwater field of the technologies developed within the European project ROBOSKIN

    Dynamic Modeling of Soft Robotic Dielectric Elastomer Actuator

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    Dielectric elastomers actuators (DEAs) are among the preferred materials for developing lightweight, high compliance and energy efficient driven mechanisms for soft robots. Simple DEAs consist mostly of a homogeneous elastomeric materials that transduce electrical energy into mechanical deformation by means of electrostatic attraction forces from coated electrodes. Furthermore, stacking multiple single DEAs can escalate the total mechanical displacement performed by the actuator, such is the case of multilayer DEAs. The presented research proposes a model for the dynamical characterization of multilayer DEAs in the mechanical and electrical domain. The analytical model is derived by using free body diagrams and lumped parameters that recreate an analogous system representing the multiphysics dynamics within the DEA. Hyperelasticity in most elastomeric materials is characterized by a nonlinear spring capable of undergoing large deformation; thus, defining the isostatic nonlinear relationship between stress and stretch. The transient response is added by employing the generalize Kelvin-Maxwell elements model of viscoelasticity in parallel with the hyperplastic spring. The electrostatic pressure applied by the electrodes appears as an external mechanical pressure that compress the material; thus, representing the bridge between the electrical and mechanical domain. Moreover, DEAs can be represented as compliant capacitors that change their capacitance as it keeps deforming; consequently, this feature can be used for purposes of self-sensing since there is always a capacitance value that can be mapped into the actual displacement. Therefore, an analytical model of an equivalent circuit of the actuator is also derived to analyze the changes in the capacitance while the actuator is under duty. The models presented analytically are then cross-validated by finite element methods using COMSOL MultiphysicsÂź as the software tool. The results from both models, the analytical and FEM model, were compared by virtually recreating the dynamics of a multilayer DEA with general circular cross section and material parameters from VHB4905 3M commercially available tape. Furthermore, this research takes the general dynamical framework built for DEAs and expand it to model the dynamical system for helical dielectric elastomer actuators (HDEAs) which is a novel configuration of the classical stack that increases the nonlinearity of the system. Finally, this research present a complementary study on enhancing the dielectric permittivity for DEAs, which is an electrical material property that can be optimized to improve the relationship between voltage applied and deformation of the actuator

    Additively Manufactured Dielectric Elastomer Actuators: Development and Performance Enhancement

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    The recently emerging and actively growing areas of soft robotics and morphing structures promise endless opportunities in a wide range of engineering fields, including biomedical, industrial, and aerospace. Soft actuators and sensors are essential components of any soft robot or morphing structure. Among the utilized materials, dielectric elastomers (DEs) are intrinsically compliant, high energy density polymers with fast and reversible electromechanical response. Additionally, the electrically driven work principle allows DEs to be distributed in a desired fashion and function locally with minimum interference. Thus, a great effort is being made towards utilizing additive manufacturing (AM) technologies to fully realize the potential of DE soft actuators and sensors. While soft sensors have received more attention and development due to their simpler implementation, DE actuators (DEAs) set stricter AM and electrode material requirements. DEAs’ layered structure, compliant nature, and susceptibility to various defects make their manufacturability challenging, especially for non-trivial biomimetic soft robotics geometries. This dissertation comprehensively analyzes DE materials’ transition into a soft actuator using AM to facilitate effective DEA soft actuator fabrication. Closely interrelated fabrication techniques, material properties, and DEA geometries are analyzed to establish a fundamental understanding of how to implement high-quality DEA soft actuators. Furthermore, great attention is paid to enhancing the performance of printed DEAs through developing printable elastomer and electrode materials with improved properties. Lastly, performance enhancement is approached from the design point of view by developing a novel 3D printable DEA configuration that actuates out-of-plane without stiffening elements

    Functional Soft Robotic Actuators Based on Dielectric Elastomers

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    Dielectric elastomer actuators (DEAs) are a promising soft actuator technology for robotics. Adding robotic functionalities--folding, variable stiffness, and adhesion--into their actuator design is a novel method to create functionalized robots with simplified actuator configurations. We first propose a foldable actuator that has a simple antagonistic DEA configuration allowing bidirectional actuation and passive folding. To prove the concept, a foldable elevon actuator with outline size of 70 mm × 130 mm is developed with a performance specification matched to a 400 mm wingspan micro air vehicle (MAV) of mass 130 g. The developed actuator exhibits actuation angles up to ± 26 ° and a torque of 2720 mN·mm in good agreement with a prediction model. During a flight, two of these integrated elevon actuators well controlled the MAV, as proven by a strong correlation of 0.7 between the control signal and the MAV motion. We next propose a variable stiffness actuator consisting of a pre-stretched DEA bonded on a low-melting-point alloy (LMPA) embedded silicone substrate. The phase of the LMPA changes between liquid and solid enabling variable stiffness of the structure, between soft and rigid states, while the DEA generates a bending actuation. A proof-of-concept actuator with dimension 40 mm length × 10mm width × 1mm thickness and a mass of 1 g is fabricated and characterized. Actuation is observed up to 47.5 ° angle and yielding up to 2.4 mN of force in the soft state. The stiffness in the rigid state is ~90 × larger than an actuator without LMPA. We develop a two-finger gripper in which the actuators act as the fingers. The rigid state allows picking up an object mass of 11 g (108 mN), to be picked up even though the actuated grasping force is only 2.4 mN. We finally propose an electroadhesion actuator that has a DEA design simultaneously maximizing electroadhesion and electrostatic actuation, while allowing self-sensing by employing an interdigitated electrode geometry. The concept is validated through development of a two-finger soft gripper, and experimental samples are characterized to address an optimal design. We observe that the proposed DEA design generates 10 × larger electroadhesion force compared to a conventional DEA design, equating to a gripper with a high holding force (3.5 N shear force for 1 cm^2) yet a low grasping force (1 mN). These features make the developed simple gripper to handle a wide range of challenging objects such as highly-deformable water balloons (35.6 g), flat paper (0.8 g), and a raw chicken egg (60.9 g), with its lightweight (1.5 g) and fast movement (100 ms to close fingers). The results in this thesis address the creation of the functionalized robots and expanding the use of DEAs in robotics
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