Low Resonant Frequency Energy Scavenging Based on Bi-Stability Structure Dynamics

University Of Louisville Research Foundation Inc, Louisville KY

Investigators

Abstract

Scavenging energy from structure vibrations is one highly promising method for potentially replacing power sources used in many applications that have traditionally used batteries. Many structures serve as natural vibration sources, such as bridges swaying due to wind loads or pipelines vibrating due to the oil flow within, which offer unique opportunities to generate energy. The primary challenge for effective implementation is developing harvesting devices that work optimally under the low frequency and somewhat random vibration conditions typical of most ambient environments. This project will explore the nonlinear response of buckled beam structures as a means to enhance power output under these chaotic, low frequency conditions. Bi-stable systems, such as buckled beams, naturally have two stable states and a nonlinear dynamic response, which has been previously shown to be ideal for irregular loading scenarios. This work seeks to improve energy harvesting efficiency under these conditions by investigating the behavior dictating switching between the stable buckled states for the unique proposed energy harvester design. Microscale versions of this device targeted for wireless sensor power applications will be probed through experiments and finite element analysis simulations. The research performed will help introduce a new class of energy harvesting devices, and will be supplemented with collaborations within the local community via the public library summer reading program and a local high school research experience outreach program. The research outcomes achieved through this work and core insights will be widely disseminated through the traditional means of publications, conferences, and workshops. Educational outreach plans will serve underrepresented groups K-12 students and the general public through a community engagement partnership the PI has created with the Louisville Free Public Library. This arrangement will help teach key engineering concepts and promote direct interaction between the PI and the larger community via several science-based activities arranged in conjunction with the library's summer reading program. In addition, the PI has solidified a relationship with a local high school science department chair to engage students on engineering topics, and recruit a diverse student group for summer research experiences working in the energy harvesting area. The objective of this research is to improve the real-world power scavenging capabilities of MEMS-scale energy harvesters through a system optimally designed for ambient vibration levels (<40 Hz) with chaotic impulse characteristics. This challenge is approached through an investigation of the system dynamics of an energy harvesting design featuring buckled beam stability state switching. Finite element modeling of structure deformations and the associated power production will be performed, with experimental testing of devices used for validation of optimized performance parameters. The focus of this project is on the nonlinear dynamic response of bi-stable buckled structures, which is leveraged to optimize strain/power generation within integrated piezoelectric over a broad spectrum of excitation frequencies. The proposed class of buckled structure MEMS work in a fundamentally different way than other bi-stable MEMS energy harvesters, creating large deformations by manipulating the constraint conditions of the structure to induce switching. The approach of using switching between buckling stability states allows for a system response that naturally is adaptive to the vibration intensity. The design used herein is unique amongst other bi-stable buckled structures, in that very low resonant frequency ranges can be targeted. Multi-node design iterations based on the same operating principle offers a potential new class of MEMS energy harvesting devices, while electro-mechanical relationships developed to describe the power generation from buckled beam stability switching will be of interest to the broader energy harvesting field. Of particular interest to the energy harvesting community will be the development of power generation models describing strains during stability state switching.