This paper presents the addition of two models for added mass to the fluid-field spring-loaded inverted pendulum (FF-SLIP) Model for legged swimming. The relative ability of these models to capture the increased fluid forces due to virtual mass displacement is evaluated using a two-legged swimming robot, Tadpole. We show that a simple addition to our reduced-order model can predict fluid-leg interaction forces while remaining computationally efficient.

In this paper we present swimming and modeling for Trident, a three-link lamprey inspired robot that is able to climb on flat smooth walls. We explore two gaits proposed to work for linear swimming, and three gaits for turning maneuvers. We compare the experimental results obtained from these swimming experiments with two different reduced order fluid interaction models, one a previously published potential flow model, and the other a slender cylinder model we developed. We find that depending on the the parameters of swimming chosen, we are able to move forward, backward and sideways with a peak speed of 2.5 cm/s. We identify the conditions when these models apply and aspects that will require additional complexity.