Design, Modeling and Optimization of the Universal-Spatial Robotic Tail

Abstract

This paper presents a novel robotic tail design that utilizes a serial chain of universal joints to generate spatial motion. In nature, animals utilize their tails to assist in maneuvering and stabilization while moving; this research aims to provide a robotic platform capable of extending these functionalities to a mobile robot. By utilizing a tail to assist in stabilization and maneuvering, the required functionality of other locomotion mechanisms in a mobile robot, such as legs, is reduced. The tail mechanism presented is actuated by sets of three cables routed along the robotic structure; quasi-independent segments within the tail are created by tying off a set of three cables to a link along the tail. Actuation is distributed within the underactuated mechanism by compression and extension springs mounted along the tail. Kinematic and dynamic analysis of the tail is performed to model the tail trajectory and predict the actuation requirements. Three methods of optimizing spring stiffnesses are provided that weigh different performance goals, and a methodology for using these results to select spring stiffnesses is provided. Results are generated to compare the kinematic, static and dynamic models to one another to analyze the impact the different loading effects have on the tail behavior.