High-performing legged robots require complex spatial leg designs and controllers to simultaneously implement propulsion, maneuvering and stabilization behaviors. Looking to nature, tails assist a variety of animals with these functionalities separate from the animals' legs. However, prior research into robotic tails primarily focuses on single-mass pendulums driven in a single plane of motion and designed to perform a specific task. In order to justify including a robotic tail on-board a legged robot, the tail should be capable of performing multiple functionalities in the robot's yaw, pitch and roll directions. The aim of this research is to study bioinspired articulated spatial robotic tails capable of implementing maneuvering and stabilization behaviors in quadrupedal and bipedal legged robots. To this end, two novel serpentine tails designs are presented and integrated into prototypes to test their maneuvering and stabilizing capabilities. Dynamic models for these two tail designs are formulated, along with the dynamic model of a previously considered continuum robot, to predict the tails' motion and the loading they will apply on their legged robots. To implement the desired behaviors, outer- and inner-loop controllers are formulated for the serpentine tails: the outer-loop controllers generate the desired tail trajectory to maneuver or stabilize the legged robot, and the inner-loop controllers calculate control inputs for the tail that implement the desired tail trajectory using feedback linearization. Maneuvering and stabilizing case studies are generated to demonstrate the tails' ability to: (1) generate yaw angle turning in both a quadruped and a biped, (2) improve the quadruped's ability to reject an externally applied roll moment disturbance that would otherwise destabilize it, and (3) counteract the biped's roll angle instability when it lifts one of its legs (for example, during its gait cycle). Tail simulations and experimental results are used to implement these case studies in conjunction with multi-body dynamic simulations of the quadrupedal and bipedal legged platforms. Results successfully demonstrate the tails' ability to maneuver and stabilize legged robots, and provide a firm foundation for future work implementing a tailed-legged robot. / Ph. D. / Looking to nature, animals utilize their tails to provide a variety of functions, including maneuvering (changing direction) and stabilization (not falling). However, research to implement tail-like structures that mimic these behaviors on-board legged robots has been limited. Furthermore, prior research into robotic tails has focused on single-link, pendulum-like structures that move in one (more common) or two (less common) directions. This research studies articulated tail structures, inspired by the way biological tails continuously bend along their length, to implement maneuvering and stabilizing behaviors in quadrupedal (four-legged) and bipedal (two-legged) robots. Two new serpentine tail designs are presented (serpentine robots are defined by numerous similar rigid links connected together), along with dynamic models that predict how the tails move and the loading that they apply to their legged robots. An additional dynamic model for a continuum robot is also presented (continuum robots are defined by their continuous, deformable structure). Controllers that plan and implement the maneuvering and stabilizing behaviors in the quadruped and biped are generated, and case studies are presented demonstrating the tails’ ability to (1) turn the quadruped and biped, (2) improve the quadruped’s ability to prevent tipping due to an external roll disturbance, and (3) prevent the biped from tipping when lifting one of its legs (for example, to step forward). Results are generated using both tail simulations and prototypes of the two tail designs under consideration. These results are used in conjunction with simulations of the quadrupedal and bipedal robots to implement the case studies.

Continuum robots are biologically inspired robots that capture the extraordinary abilities of biological structures such as elephant trunks, octopus tentacles, and mamma-lian tongues. They are given the term continuum robots due to their ability to bend conti-nuously rather than at specific joints such as with traditional rigid link robots. They are used in applications such as search and rescue operations, nuclear reactor repairs, colo-noscopies, minimal invasive surgeries, and steerable needles. In this thesis, a model that predicts the shape of a continuum robot is presented and verified. A verification system to verify the validity and accuracy of the model is presented which allows easy and accu-rate measurement of a continuum robot tip position. The model was verified against a flexible rod, the core component of a continuum robot, resulting in an accuracy of 0.61%. Finally, this thesis introduces a novel robot design, consisting of a single rod for the backbone which can be manipulated by applying external forces and torques.