Abstract

This thesis presents a new approach to actuating soft robots using internal fluid flow, aiming to understand both its feasibility and the principles that govern its behavior. While previous research in this area is limited, this work introduces a theoretical model of a soft, slender cylindrical robot driven by incompressible fluid flow through embedded channels. The robot’s static deflection is described using a geometrically-exact equation derived from Euler-Bernoulli beam theory, with flow dynamics incorporated through control volume analysis. The study also includes fluid-structure interaction simulations based on a hyperelastic material model. The Yeoh third-order model, fitted to tensile test data from the silicone material, was employed to replicate the robot’s deformation during the loading phase with high accuracy. To validate the model, prototypes were fabricated using silicone additive manufacturing. A custom test setup was designed to measure planar deflections in response to varying liquid water flow rates. Image processing techniques were used to track the robot’s mid-axis shape and quantify tip deflection, which showed strong alignment with theoretical predictions. On average, the experiments resulted in a tip deflection of approximately 58% of the robot’s initial length, with average tip position error of 9% comparing to the analytical model. Experimental results revealed a different behavior of the soft robot during flow velocity decrease, marked by reduced deflection of the tip, that was not captured by the theoretical or simulation models. Overall, the findings support the potential of flow-driven actuation in soft robotics and emphasize the need to account for material nonlinearities in future modeling efforts.