The Development of an Incrementally Loaded Finite Element Model of the Whole Skin Locomotion Mechanism: Discovering the Relationship Between Its Shape and Motion

Abstract

The Whole Skin Locomotion (WSL) robotic platform is a novel biologically inspired robot that uses a fundamentally different locomotion strategy than other robots. Its motion is similar to the cytoplasmic streaming action seen in single celled organisms such as the amoeba. The robot is composed of a closed volume, fluid filled skin which generally takes the shape of an elongated torus. When in motion the outer skin is used as the traction surface. It is actuated by embedded smart material rings which undergo cyclical contractions and relaxations, generating an everting motion in the torroidially shaped skin. To better understand, design, and optimize this mechanism, it is necessary to have a model of the skin, fluid, and actuators and their interactions with the environment. This paper details the first steps in the development of a non-linear finite element (FE) model which will allow us to study these interactions and predict the shape and motion of the robot under various actuation strategies. A simple membrane element model is introduced from literature and is modified such that an incremental loading strategy can be employed. Finally, an underlying physical mechanism is introduced which could possibly describe the relationship between the shape of and pressure within the membrane skin and motion of the whole skin locomotion robot.