Simulations of a three degree of freedom brachiating Y-bot robot

Abstract

Brachiation is a means of locomotion for lightweight apes like gibbons. It involves the animal swinging its arms to gain moment and swing forward. A large amount of research has been done studying a simplified two-link two DOF robot, named "acrobot" by Mark Spong. While the problems of this robot have been studied extensively, it's functionality is quite limited. This paper studies a three-link three DOF brachiating robot, dubbed "Y-bot". The goal of adding the extra link is to add functionality. Simulations of a model were run in Matlab taking advantage of Russ Tedrake's toolbox Drake, which was designed to solve optimization problems of underactuated systems. The main method used in the trajectory optimization was direct collocation. The task of the robot in the simulations was to swing from a one "branch" point to another. The trajectories of two Y-bot models swinging from rest were optimized. Furthermore, the gait of one of the models was examined, and a beneficial state for the second swing of a gait was suggested. A method to optimizing the gait of a model was proposed. A linear relationship between the total trajectory time and the scale of the model was defined. The paper suggests a physical model of the Y-bot could be constructed using Saito's two DOF brachiating robot as a benchmark. The problems of gait optimization and payload transportation were mentioned as future work to be done.