N24A-T017 TITLE: Soft Robot for Locomotion in Granular Seabed Media

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials; Biotechnology

OBJECTIVE: Develop a soft robot capable of untethered, autonomous locomotion within granular media in shallow sea-floor environments.

DESCRIPTION: Expeditionary forces often work within the littoral environment, to include manipulation of soft, murky, and complex seabed. It is common for these seabed environments to prove difficult for sensors to penetrate for a full understanding of the bathymetry and shallow water regime. The ability to utilize a system which, when deployed by a diver, or from an autonomous vehicle, can work within and on the seabed, penetrating the sediment to help expeditionary users better understand the bottom habitat. This STTR topic seeks to develop a soft robot capable of untethered, autonomous locomotion within granular media in shallow sea-floor environments. The robot should be able to operate with an onboard power source and control system that can permit up to 2 hours of movement and 72 hours of stationary sensing. The robot should be capable of movement within submerged sand up to a depth within 1 meters of the sand surface, and horizontal movement up to 10 meters, on a single battery charge.

A proposed operational task for such robots would be surveying underwater soil regions by following movement trajectories that are pre-defined (e.g., a grid trajectory), or sensory feedback determined (e.g., follow path of low soil resistance). This task requires the ability to move in multiple directions and to incorporate sensor feedback into basic control algorithms for robot movement. The specific military impact will be to enable the detection, characterization and possibly neutralization of buried mines on the seafloor, and locate attached buried wires, although these would not be the specific tasks within this STTR topic. There would also be future opportunities for seabed sensing, communication, and ISR roles.

PHASE I: Conduct a study on the feasibility of a biologically inspired power-autonomous vehicle design, with a focus on mobility mechanism and power source. This should draw on prior biological research on subterranean locomotion kinematics, dynamics, and granular-body interactions. Identify the most promising actuation mechanism, including power requirements and expected lifetime. Conduct a design study of the feasibility of different sustainable power sources (e.g., solar, mechanical energy scavenging, microbial fuel cells) and specify the expected mission duration. Identify materials with surfaces that resist fouling. Develop a Phase II plan.

PHASE II: Fully develop and fabricate a prototype, according to the requirements stated in the Description. Evaluate the design via in-water tests conducted in a realistic submerged soil environment, targeting the listed performance objectives, including vertical and horizontal digging range and stiffness gradient sensing, via untethered operations. At a minimum, the prototype testing shall consist of (1) basic operability testing, (2) grid survey, (3) range/endurance trials, and (4) object detection. The awardee may propose other tests needed to demonstrate the benefits of their design perform analyses to establish reliability, identify areas needing further improvement, if necessary, and analyze manufacturing scalability in order to transition the design into a useful product for the Navy.

PHASE III DUAL USE APPLICATIONS: Apply the knowledge gained in Phase II to build a prototype ready for field testing. Test the prototype according to the Phase II test goals.

This technology would have dual use for seabed geotechnical measurements, geology, oceanography, and fisheries.

REFERENCES:

1. Ortiz, D.; Gravish, N. and Tolley M. T. "Soft Robot Actuation Strategies for Locomotion in Granular Substrates." IEEE Robotics and Automation Letters, 4:3, pp. 2630-2636.
2. Dorgan, K.M. "The biomechanics of burrowing and boring." J. Exp. Biol., vol. 218, no. Pt 2, January 2015, pp. 176-183.
3. Naclerio, N.D.; Karsai, A.; Murray-Cooper, M.; Ozkan-Aydin, Y.; Aydin, E.; Goldman, E.I. and Hawkes, E.W. "Controlling subterranean forces enables a fast, steerable burrowing soft robot." Science Robotics, vol. 6, no. 55, 2021, p. eabe2922.
4. Ge, J. Z.; Calderón, A. A.; Chang, L. and Pérez-Arancibia, N. O. "An earthworm-inspired friction-controlled soft robot capable of bidirectional locomotion." Bioinspiration & Biomimetics, 14(3), 036004, 2019.
5. Martinez, A et al. "Bio-inspired geotechnical engineering: principles, current work, opportunities and challenges." Géotechnique, Volume 72 Issue 8, August, 2022, pp. 687-705.

KEYWORDS: soft robotics; seabed; granular media; underwater soil; autonomous; locomotion, burrowing

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