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1. Hybrid vine robot with internal Steering-Reeling Mechanism enhances system-level capabilities

   https://doi.org/10.1109/LRA.2021.3072858  

   Haggerty, David Arthur ; Naclerio, Nicholas ; Hawkes, Elliot Wright ( January 2021 , IEEE Robotics and Automation Letters)

   null (Ed.)

   Continuum robots have high degrees of freedom and the ability to safely move in constrained environments. One class of soft continuum robot is the “vine” robot. This type of robot extends from its tip by everting or unfurling new material, driven by internal body pressure. Most vine robot examples store new body material in a reel at their base, passing it through the core of the robot to the tip, and like many continuum robots, steer by selectively lengthening or shortening one side of the body. While this approach to steering and material storage lends itself to a fully soft device, it has three key limitations: (i) internal friction of material passing through the core of the robot limits its length in tortuous paths, (ii) body buckling as the robot's body material is re-spooled at the base can prevent retraction, and (iii) constant curvature steering limits the robot's poses and object approach angles in a given workspace. This letter presents a hybrid soft-rigid robotic system comprising a soft vine robot body and a rigid, mobile, internal steering-reeling mechanism (SRM); this SRM is equipped with a reel for material storage, a bending actuator for steering, and is capable of actuating the robot at any point along its length. This hybrid configuration increases reach along tortuous paths, allows retraction, and increases the workspace. We describe the motivation for the device, generate its mathematical models, present its methods of operation, and verify experimentally the models we developed and the performance improvements over previous vine robots. 

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2. Soft Retraction Device and Internal Camera Mount for Everting Vine Robots

   William E. Heap, Nicholas D. ( January 2021 , Proceedings of the IEEERSJ International Conference on Intelligent Robots and Systems)

   null (Ed.)

   Soft, tip-extending, pneumatic “vine robots” that grow via eversion are well suited for navigating cluttered environments. Two key mechanisms that add to the robot’s functionality are a tip-mounted retraction device that allows the growth process to be reversed, and a tip-mounted camera that enables vision. However, previous designs used rigid, relatively heavy electromechanical retraction devices and external camera mounts, which reduce some advantages of these robots. These designs prevent the robot from squeezing through tight gaps, make it challenging to lift the robot tip against gravity, and require the robot to drag components against the environment. To address these limitations, we present a soft, pneumatically driven retraction device and an internal camera mount that are both lightweight and smaller than the diameter of the robot. The retraction device is composed of a soft, extending pneumatic actuator and a pair of soft clamping actuators that work together in an inch-worming motion. The camera mount sits inside the robot body and is kept at the tip of the robot by two low-friction interlocking components. We present characterizations of our retraction device and demonstrations that the robot can grow and retract through turns, tight gaps, and sticky environments while transmitting live video from the tip. Our designs advance the ability of everting vine robots to navigate difficult terrain while collecting data. 

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3. Passive Shape Locking for Multi-Bend Growing Inflated Beam Robots

   https://doi.org/10.1109/RoboSoft55895.2023.10122027  

   Jitosho, Rianna ; Simón-Trench, Sofia ; Okamura, Allison M. ; Do, Brian H. ( January 2023 , IEEE International Conference on Soft Robotics (RoboSoft))

   Shape change enables new capabilities for robots. One class of robots capable of dramatic shape change is soft growing “vine” robots. These robots usually feature global actuation methods for bending that limit them to simple, constant-curvature shapes. Achieving more complex “multi-bend” configurations has also been explored but requires choosing the desired configuration ahead of time, exploiting contact with the environment to maintain previous bends, or using pneumatic actuation for shape locking. In this paper, we present a novel design that enables passive, on-demand shape locking. Our design leverages a passive tip mount to apply hook-and-loop fasteners that hold bends without any pneumatic or electrical input. We characterize the robot's kinematics and ability to hold locked bends. We also experimentally evaluate the effect of hook-and-loop fasteners on beam and joint stiffness. Finally, we demonstrate our proof-of-concept prototype in 2D. Our passive shape locking design is a step towards easily reconfigurable robots that are lightweight, low-cost, and low-power. 

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4. An obstacle-interaction planning method for navigation of actuated vine robots

   https://doi.org/10.1109/ICRA40945.2020.9196587  

   Selvaggio, M. ; Ramirez, L. A. ; Naclerio, N. D. ; Siciliano, B. ; Hawkes, E. W. ( May 2020 , IEEE International Conference on Robotics and Automation (ICRA))

   null (Ed.)

   The field of soft robotics is grounded on the idea that, due to their inherent compliance, soft robots can safely interact with the environment. Thus, the development of effective planning and control pipelines for soft robots should incorporate reliable robot-environment interaction models. This strategy enables soft robots to effectively exploit contacts to autonomously navigate and accomplish tasks in the environment. However, for a class of soft robots, namely vine-inspired, tip-extending or "vine" robots, such interaction models and the resulting planning and control strategies do not exist. In this paper, we analyze the behavior of vine robots interacting with their environment and propose an obstacle-interaction model that characterizes the bending and wrinkling deformation induced by the environment. Starting from this, we devise a novel obstacle-interaction planning method for these robots. We show how obstacle interactions can be effectively leveraged to enlarge the set of reachable workspace for the robot tip, and verify our findings with both simulated and real experiments. Our work improves the capabilities of this new class of soft robot, helping to advance the field of soft robotics. 

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5. Characterizing Environmental Interactions for Soft Growing Robots

   https://doi.org/10.1109/IROS40897.2019.8968137  

   Haggerty, David A. ; Naclerio, Nicholas D. ; Hawkes, Elliot W. ( November 2019 , IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS))

   null (Ed.)

   Soft, tip-extending devices, or “vine robots,” are a promising new paradigm for navigating cluttered and confined environments. Because they lengthen from their tips, there is little relative movement of the body with the environment, and the compressible nature of the device allows it to pass through orifices smaller than its diameter. However, the interaction between these devices and the environment is not well characterized. Here we present a comprehensive mathematical model that describes vine robot behavior during environmental interaction that provides a basis from which informed designs can be generated in future works. The model incorporates transverse and axial buckling modes that result from growing into obstacles with varying surface normals, as well as internal path-dependent and independent resistances to growth. Accordingly, the model is able to predict the pressure required to grow through a given environment due to the interaction forces it experiences. We experimentally validate both the individual components and the full model. Finally, we present three design insights from the model and demonstrate how they each improve performance in confined space navigation. Our work helps advance the understanding of tip-extending, vine robots through quantifying their interactions with the environment, opening the door for new designs and impactful applications in the realms of healthcare, research, search and rescue, and space exploration. 

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