Self-Sufficient Swimming and Digging Worm-Inspired Robot (S2 SanD-Worm): Fluidization and Eversion for Enhanced Underwater Digging and Object Detection
Abstract
Autonomous robots capable of burial and locomotion beneath the sea-floor have myriad applications of Naval relevance such as structural inspection, surveillance, environmental monitoring, and biological observation. However, current aquatic robots are either capable of swimming movement through water, or have limited capabilities of moving through the granular or muddy seafloor medium. Granular environments such as sandy seabeds, are one of the most prevalent substrates on Earth, and yet one of the most difficult environments for robots to move within. Locomotion within granular media requires robots to overcome large depth-dependent forces, contend with non-zero yield stress that may cause unpredictable fluid/solid resistance forces, and perform with extremely limited sensing capabilities.Many animals, on the other hand, are able to skillfully transition between swimming and burial locomotion within the seafloor. For example, small polychaetes (bristle worms) are capable of swimming near the sea-floor surface and transitioning to digging locomotion within the sea-bed through undulatory motion of their soft bodies. Polychaetes use a variety of behaviors to control the drag and resistive forces acting on them during digging, including:1)local fluidization and hydraulic fracture, 2) crack propagationthrough body eversion at the head, and 3) modulation of internal pressure to anchor and propagate cracks. In this proposal we will study how a soft robot can utilize these three principles to control the resistive granular forces during digging locomotion.The work in this proposal will leverage a previously funded ONR developed robot, which we call a Swimming and Digging Worm-inspired robot #SanD-Worm#. Prior work on the SanD-Worm project studied how combinations of body undulation and appendage actuation enabled digging locomotion, and obstacle sensing. In the proposed work, we will build off of the knowledge gained from SanD-Worm and we will integrate this into a nextgeneration robot, Self-Sufficient Swimming and Digging Worm-inspired robot (S2 SanD-Worm). This project will benefit from over five years of research on soft robots for subterranean locomotion by PIs Gravish and Tolley.The mechanical design of SanD-Worm will use soft exterior materials such as silicone and other elastomers to achieve a soft, expandable exterior body. A fundamental area of research is determining how body movements weaken or strengthen submerged granular material; weakening is required for reducing drag force on the body, and strengthening is required to generate forward thrust forces. The design and testing of this system leverages PI#s Gravish and Tolley#s combined expertise in the physics of granular flow (Gravish), and the design and control of soft-robots (Tolley). The project will be performed in three phases (assicated with the tasks of fluidization, low-boiling point fluid actuation, and eversion enabled locomotion), culminating in a robot demonstration of locomotion capabilities in year three.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 12, 2023
- Source ID
- N000142312358
Entities
People
- Michael T Tolley
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego