Overcoming Obstacles Using Tail STAR: A Novel Sprawling Robot With a Two-Joint Tail

Abstract

This paper presents Tail STAR (TSTAR), a novel reconfigurable robot with an active two-link tail. TSTAR is also fitted with a sprawling mechanism that lets it run either upright or inverted and change its height. The tail enables the robot to move its center of mass (COM) forwards or backwards and extend its length, provides it with more surface contact points, and increases its climbing capabilities. After presenting a kinematic model of the robot, a quasi-static analysis is presented that aims at optimizing the design of the robot and evaluating its motor requirements, climbing conditions and limitations. Experiments then show that the combination of the sprawling and tail mechanisms enables the TSTAR to overcome extremely challenging obstacles, climb high steps (6 times its wheel radius), bridge gaps equal to its own body length, and flip over to switch between its whegs and wheels to operate on very different terrains such as dirt, stones and grass (see attached video).