Design of a Low Energy, Self Contained Subsea Burrowing Robot Based on Localized Fluidization Exhibited by Atlantic Razor Clams

Abstract

The Atlantic razor clam (Ensis directus) burrows by contracting its valves, fluidizing the surrounding soil and reducing burrowing drag. Moving through a fluidized, rather than static, soil requires energy that scales linearly with depth, rather than depth squared. In addition to providing an advantage for the animal, localized fluidization may provide significant value to engineering applications such as vehicle anchoring and underwater pipe installation. This paper presents the design of a self-actuated, radially expanding burrowing mechanism that utilizes E. directus’ burrowing methods. The device is sized to be a platform for an anchoring system for autonomous underwater vehicles. Scaling relationships presented allow for design of burrowing systems of different sizes for a variety of applications. The minimum contraction time for a given device size governs how quickly the device must move. Contraction displacement necessary to achieve fluidization is presented. The maximum force for a given size mechanism is also calculated, and allows for sizing actuators for different systems. This paper presents the design of a system that will allow testing of these parameters in a laboratory setting. These relationships provide the optimal sizing and power needs for various size subsea borrowing systems.