Dynamic Behavior and Output Charge Analysis of a Bistable Clamped-Ends Energy Harvester

Abstract

Vibration energy harvesting systems are an excellent power source alternative to batteries or other green energy alternatives, given that many application environments feature vibration sources significant enough for power scavenging. The most important challenge faced by these types of energy harvesters is their general operating inefficiency when driven by the chaotic, low frequency vibration sources characteristic of most real-life scenarios. Prediction of power for these systems requires a detailed understanding of their performance under dynamic conditions. In this study, an analytical method is applied to dynamically analyze the output electrical charge of a piezoelectric-based bistable energy harvester under harmonic excitation. This system is made of a clamped-clamped buckled beam with attached piezo patches and a lump mass at the center. The bistability is created by a compressive load applied at the beam ends. In order to appropriately analyze the dynamic behavior of the structure, the beam is divided into two components in a way that the dynamic effect of the tip mass appears in the boundary conditions as a matching relation between two parts. First, natural frequencies and mode shapes of the system are found by theoretically solving the free undamped linear system. These obtained mode shapes are then used in a Galerkin approach to discretize the nonlinear equations of the buckled structure. By solving the nonlinear equations, Poincare’ plot and output electrical charge for a buckled case under three different exciting frequencies are investigated to analyze the performance of the bistable energy harvester.