Modeling and Analysis of a Bimorph Piezoelectric Lambda-shaped Harvester Having Robust Vibration Energy Harvesting Characteristics

Abstract

Self-powered systems that operate piezoelectric energy harvesters (PEHs, including medical devices, wearable devices and wireless sensors), have gained a lot of attention during the recent decade as Internet of Things technology has been introduced. As an alternative energy solution to batteries, PEHs can supply stable power to these devices by harvesting ambient vibrations. The principal objective of this paper is to show the superior and robust characteristics of a novel Lambda-shaped beam structure for bimorph piezoelectric energy harvesting. The equations of motion of the harvester were derived based on Kane’s method and the Euler–Bernoulli beam theory. The accuracy of the analytical model was validated with finite element analysis (FEA) and experimental results. Based on the analytical model, the optimal load resistance and maximal output power of the proposed harvester were determined. Moreover, the real damping ratio measured in the experiment and the influence of the damping ratio on the maximal output voltage are presented in this paper. The Lambda-shaped energy harvester with a load resistance generates 0.16 mW maximal power. The value is much higher than that 0.07 mW of the conventional PEH (CPEH) with the cantilever shape, which is connected to the same load resistance and has the same base excitation. Moreover, the effects of the base excitation direction of the Lambda-shaped harvester on the energy harvesting performance were investigated. The results showed that the Lambda-shaped harvester had robust energy harvesting characteristics with respect to base excitation directions. The robust characteristics related to the base excitation direction make the proposed Lambda-shaped energy harvester superior to the commonly used conventional harvester; more specifically, the former has a higher commercialization potential because of its prominent design flexibility and robust energy harvesting characteristics.