Modeling of Inter - Component and Inter - Domain Dynamic Interactions of an Excavator Using Bond Graphs

Abstract

In this paper the interaction of hydraulic and mechanical dynamics, the inter-actuator and inter-link interactions in an excavator are modeled using bond graphs, and then simulated on a MATLAB/SIMULINK environment. Bond graph method was chosen as the modeling method because, firstly, it is a domain-independent graphical method of representing the dynamics of physical systems. Therefore, systems from different engineering disciplines can be described in the same way. Secondly, the available literature shows that the method being relatively new has not been thoroughly applied to model the dynamics of nonlinear systems such as excavators. A complete bond graph dynamic model of the excavator was obtained by coupling the mechanical and hydraulic models using appropriate Manipulator Jacobians which were treated as Modulated Transformer Elements. The causal bond graph model of the excavator was expanded into block diagrams and simulated on MATLAB/SIMULINK to determine the transient and steady state responses of the system. From the responses obtained, the model developed was found to capture the inter-component interactions and also the interaction between the hydraulic and mechanical dynamics. Therefore, the model developed can be used to design control laws necessary for controlling the dynamics and motions of the excavating manipulator.