UC San Diego

Many platforms have been developed for moving remotely underwater; however, many of these systems are limited to traversing open water and must expend large amounts of energy to maintain a position in flow for long periods of time. Legged animals are common in nature, but often have fixed body morphologies restricting them to constant hydrodynamic profiles. This work presents an underwater legged robot with soft legs and a soft morphing body for manipulating the hydrodynamic forces in flow. Computational fluid dynamics (CFD) simulations of the morphing body in flow allow 1) prediction of the effect of morphing on lift and drag forces, and thus 2) determination of which body configuration is most favorable for specific tasks. Flow over the morphing body separates behind the trailing edge which determines where turbulence begins to form, causing additional drag. When the legged robot needs to remain stationary in flow, a flat structure offers reduced hydrodynamic forces for resisting sliding. When the legged robot needs to walk with flow, a larger inflated body is pushed along by the flow, causing that robot to walk faster than it would otherwise. A commercial force sensor can detect flow so that the robot can respond by morphing into a more advantageous shape. Experiments with the prototype robot are used to test these capabilities.