Legless Locomotion: Concept and Analysis

This thesis presents a novel locomotion technique, called legless locomotion, for convex-bodied legged robots. The motivation for studying legless locomotion stems from the mobile robot recovery problem, stated simply as what should a robot do when trapped? Legless locomotion is the technique of locomotion for a legged robot which has no leg-ground contact, but can use the swinging legs to excite body rotations. Legless locomotion is a result of the interaction between reaction mass-dynamics and robot-ground contact kinematics and presents many open research questions. Legless locomotion has many parameters, such as the robot mass distribution, robot body shape, leg motions, and contact constraints. We use a simple twolegged robot Rocking and Rolling Robot (RRRobot), RHex, a hexapod robot, and simulations to understand how the phenomena simultaneously interact. We also develop approximate simplified models that give us a qualitative understanding of the system behavior (see figure below). We hope to develop more exact kinematic reductions of legless locomotion, that will help us control legless locomotion. Finally, we present a classification structure for mobile robot error due to external physical influences and propose legless locomotion as a recovery technique for the particular case when a robot gets high-centered, that is, there is no leg-ground contact.