Model validity of bond-graph elements for power assessment

The benefits of a bond-graph analysis for vibration-based harvesters are presented. The bond graph is a power-based approach for describing dynamic systems by presenting the power flow graphically, which helps in understanding the behavior of complicated systems in simple terms. Energy harvesting involves the conversion of power in a mechanical form to an electrical one, and the bond graph is an appropriate tool for analyzing the power flow. The bond-graph method can be used to calculate the dynamics of the combined mechanical and electrical systems simultaneously. The greatest advantage of the bond-graph technique is that it can be used with the systems that are subject to component swaps because the bond graph involves solving simultaneous algebraic equations instead of differential equations. Common simulation methods such as solving differential equations have difficulty in changing the number of electrical components (inserting, removing, or swapping) because the differential equations will have to be reconstructed to adjust for any changes. In this paper, we first proposed a piezoelectric model that matches the bond-graph method. We then analyze a self-powered energy harvester that has multi-bifurcated and looped flow in the mechanical-electrical coupled dynamics.