Modelling of a robotic leg using bond graphs

This paper studies the bond graph model of a robotic leg mechanism, and discusses methods of extracting significant features of system dynamics through simpler models. The goal is to determine a set of simpler mechanisms with similar dynamic behaviour to that of the original leg in various phases of its motion. The paper is divided in two sections. In the first section, a modular bond-graph representation of the leg mechanism is determined. In the second section, two algorithms are applied to simplify the bond graph representation. The first algorithm determines the relevant dynamic elements of the system for each phase of motion, and the second algorithm finds the simple mechanism described by the remaining dynamic elements. In addition to greatly simplifying the control system of the robotic leg, using simpler mechanisms with similar behaviour provides a greater insight into the dynamics of the system.