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1. 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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2. A Dexterous Tip-extending Robot with Variable-length Shape-locking

   https://doi.org/10.1109/ICRA40945.2020.9197311  

   Wang, Sicheng; Zhang, Ruotong; Haggerty, David A.; Naclerio, Nicholas D.; Hawkes, Elliot W. (May 2020, IEEE International Conference on Robotics and Automation (ICRA))

   null (Ed.)

   Soft, tip-extending "vine" robots offer a unique mode of inspection and manipulation in highly constrained environments. For practicality, it is desirable that the distal end of the robot can be manipulated freely, while the body remains stationary. However, in previous vine robots, either the shape of the body was fixed after growth with no ability to manipulate the distal end, or the whole body moved together with the tip. Here, we present a concept for shape-locking that enables a vine robot to move only its distal tip, while the body is locked in place. This is achieved using two inextensible, pressurized, tip-extending, chambers that "grow" along the sides of the robot body, preserving curvature in the section where they have been deployed. The length of the locked and free sections can be varied by controlling the extension and retraction of these chambers. We present models describing this shape-locking mechanism and workspace of the robot in both free and constrained environments. We experimentally validate these models, showing an increased dexterous workspace compared to previous vine robots. Our shape-locking concept allows improved performance for vine robots, advancing the field of soft robotics for inspection and manipulation in highly constrained environments. 

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3. 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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4. 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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5. Distributed Sensor Networks Deployed Using Soft Growing Robots

   https://doi.org/10.1109/RoboSoft51838.2021.9479345  

   Gruebele, Alexander M.; Zerbe, Andrew C.; Coad, Margaret M.; Okamura, Allison M.; Cutkosky, Mark R. (January 2021, International Conference on Soft Robotics (RoboSoft))

   null (Ed.)

   Due to their ability to move without sliding relative to their environment, soft growing robots are attractive for deploying distributed sensor networks in confined spaces. Sensing of the state of such robots would add to their capabilities as human-safe, adaptable manipulators. However, incorporation of distributed sensors onto soft growing robots is challenging because it requires an interface between stiff and soft materials, and the sensor network needs to undergo significant strain. In this work, we present a method for adding sensors to soft growing robots that uses flexible printed circuit boards with self-contained units of microcontrollers and sensors encased in a laminate armor that protects them from unsafe curvatures. We demonstrate the ability of this system to relay directional temperature and humidity information in hard-to-access spaces. We also demonstrate and characterize a method for sensing the growing robot shape using inertial measurement units deployed along its length, and develop a mathematical model to predict its accuracy. This work advances the capabilities of soft growing robots, as well as the field of soft robot sensing. 

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