2015 Volume 2 Issue 4 Pages 14-00444
In this paper, we present the benefits of bond-graph analysis for mechanical-electrical systems, which are energy-harvesters based on structural vibrations and electric loads. The bond-graph is an energy-based approach to describing physical-dynamic systems. It shows power flow graphically, which helps us understand the behavior of complicated systems in simple terms. Energy-harvesting involves conversion of power in mechanical form to the electrical one and the bond-graph is a good tool to analyze this flow. The bond-graph method can be used to calculate the dynamics of the combining mechanical and electrical systems simultaneously. The biggest advantage of the bond-graph technique is that it can be used with the systems that are subject to component alternations, such as inserting, removing and swapping. The bond-graph method involves solving simultaneous algebraic equations, instead of differential equations. On the other hand, in common simulation methods, such as solving differential equations, it is difficult to change the number of components because the differential equations will have to be reconstructed. Because the bond-graph has not been used for harvesting analysis, bond-graph models for harvesting need to be created in advance of numerical analysis. In this paper, we first proposed a piezoelectric model that matches the bond-graph method. We also propose a diode-bridge model and a harvesting controller model that are suitable for bond-graph analysis. We then analyze a self-powered energy harvester that has multi-bifurcated and looped flow in the mechanical-electrical coupled dynamics.