Modeling of a four-legged robot with variable center of mass as a cooperative multirobot system

Abstract

A multibody system, such as a multiple legged robot, can be modeled and controlled as a cooperative multirobot system (CMS), since it is expected that the several parts involved in the multibody to have a common purpose, in which they must cooperate in order to achieve success. This paper introduces the modeling of a four-legged robot as a set of five robot manipulators: four legs and one additional torso robot for center of mass change. The body’s trajectory is defined and the legs must move cooperatively in order to keep the movement as defined, and the cooperation factor is used again with the torso compensation. The task of the torso robot is to keep the center of mass inside the supporting polygon composed by (at least) three legs, so that the system can remain stable at all times, and, because of that, must act cooperatively with the legs’ movement. The kinematics are computed and simulated using the presented methodology, with screw theory, Assur virtual chains, graph theory and Davies method.