Browsing by Subject "Soft Robotics"

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    Inverse Design of Soft Robotic Actuators using Nonlinear Finite Element Modeling
    (2019-11) Gilbertson, Mark
    The field of soft robotics has empowered robots to maneuver, traverse, and complete tasks where traditional rigid robots fall short. These robots are able to bend continuously and conform to their environments which makes their designs inherently safe. This makes soft robots a suitable candidate for use in medical devices. This thesis explores an inverse soft robot design algorithm, with possible future applications to a soft catheter robot. Soft robot techniques were used to create a large scale prototype of a hydraulically powered, serial, soft catheter robot. The locomotion section of this robot consisted of three fiber reinforced elastomeric enclosures (FREE) actuators connected by passive valves. When controlled properly, the locomotion section was able to ‘inchworm’ through a tube, thus demonstrating the feasibility of a serially controlled catheter. Although the FREE actuators were able to produce locomotion in the tube, the limitation of realizable actuator shapes severely hampered the robot's performance. This limitation motivated the need for a generalized design tool where the user could dictate the desired actuator shapes. To accomplish the additional design freedom, an inverse problem was explored. First, a mathematical description of cylindrical actuator shapes was developed. Allowing a user to create arbitrary actuator shapes that deformed from an initial state to a final state. Next, a nonlinear inverse Finite Element Modeling optimization algorithm was developed to reconstruct the material properties when the boundary conditions and internal pressure were known. The inverse algorithm was tested on three cylindrical actuator motions. The first was a ballooning actuator which expanded uniformly in every direction. The second was a bending actuator capable of rotation constrained to a single plane. The third was a twisting actuator that rotated along its axis in a nearly pure shear translation, transforming a pressure input into out of plane motion. The material properties of all three actuator motions were successfully reconstructed with the developed inverse algorithm. The reconstructed twisting actuator was then 3D printed with a multi-material polyjet 3D printer and experimentally shown to match the twist of both the ground truth design and simulated results. This provided some initial validation of the inverse algorithm.
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    Supporting data for "3D printed electrically-driven soft actuators"
    (2020-06-09) Haghiashtiani, Ghazaleh; Habtour, Ed; Park, Sung-Hyun; Gardea, Frank; McAlpine, Michael C; mcalpine@umn.edu; McAlpine, Michael C; McAlpine Research Group
    Soft robotics is an emerging field enabled by advances in the development of soft materials with properties commensurate to their biological counterparts, for the purpose of reproducing locomotion and other distinctive capabilities of active biological organisms. The development of soft actuators is fundamental to the advancement of soft robots and bio-inspired machines. Among the different material systems incorporated in the fabrication of soft devices, ionic hydrogel–elastomer hybrids have recently attracted vast attention due to their favorable characteristics, including their analogy with human skin. Here, we demonstrate that this hybrid material system can be 3D printed as a soft dielectric elastomer actuator (DEA) with a unimorph configuration that is capable of generating high bending motion in response to an applied electrical stimulus. We characterized the device actuation performance via applied (i) ramp-up electrical input, (ii) cyclic electrical loading, and (iii) payload masses. A maximum vertical tip displacement of 9.78 ± 2.52 mm at 5.44 kV was achieved from the tested 3D printed DEAs. Furthermore, the nonlinear actuation behavior of the unimorph DEA was successfully modeled using an analytical energetic formulation and a finite element method (FEM).