Razor clam to RoboClam: burrowing drag reduction mechanisms and their robotic adaptation
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Hosoi_Razor clam.pdf
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4.65 MB
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Author(s)
Winter, Amos
Deits, Robin Lloyd Henderson
Dorsch, Daniel S.
Slocum, Alexander H.
Hosoi, Anette E.
Date Issued
April 2014
Journal
Bioinspiration & Biomimetics
Publisher
IOP Publishing
Citation
Winter, A G, R L H Deits, D S Dorsch, A H Slocum, and A E Hosoi. “Razor Clam to RoboClam: Burrowing Drag Reduction Mechanisms and Their Robotic Adaptation.” Bioinspiration & Biomimetics 9, no. 3 (April 8, 2014): 036009. © 2014 IOP Publishing Ltd
Version
Final published version
Abstract
Estimates based on the strength, size, and shape of the Atlantic razor clam (Ensis directus) indicate that the animal's burrow depth should be physically limited to a few centimeters; yet razor clams can dig as deep as 70 cm. By measuring soil deformations around burrowing E. directus, we have found the animal reduces drag by contracting its valves to initially fail, and then fluidize, the surrounding substrate. The characteristic contraction time to achieve fluidization can be calculated directly from soil properties. The geometry of the fluidized zone is dictated by two commonly-measured geotechnical parameters: coefficient of lateral earth pressure and friction angle. Calculations using full ranges for both parameters indicate that the fluidized zone is a local effect, occurring between 1–5 body radii away from the animal. The energy associated with motion through fluidized substrate—characterized by a depth-independent density and viscosity—scales linearly with depth. In contrast, moving through static soil requires energy that scales with depth squared. For E. directus, this translates to a 10X reduction in the energy required to reach observed burrow depths. For engineers, localized fluidization offers a mechanically simple and purely kinematic method to dramatically reduce energy costs associated with digging. This concept is demonstrated with RoboClam, an E. directus-inspired robot. Using a genetic algorithm to find optimal digging kinematics, RoboClam has achieved localized fluidization burrowing performance comparable to that of the animal, with a linear energy-depth relationship, in both idealized granular glass beads and E. directus' native cohesive mudflat habitat.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1088/1748-3182/9/3/036009
