Abstract

With the development of micro-sensors and wireless applications, energy harvesting has become an effective method for self-powering. However, ambient energy is only limited to below 100Hz, which restricts the energy harvester designs to this range resulting in
an impractical bulky and large-scale harvester. Therefore, in this thesis, we investigated
frequency Up and Down conversion energy harvesters to benefit from the high-frequency oscillations and transferred them to the ambient vibration ranges. Toward this, the triboelectric transduction mechanism has been utilized for a frequency-up conversion for energy harvesting applications, while the piezoelectric transduction mechanism is used for frequency-down
conversion for mass sensing applications. The performance of Vibro-impact triboelectric energy harvesting from low frequency using frequency up-conversion has been investigated theoretically and experimentally validated. The structure consists of two cantilever beams, one with a low natural frequency (Low-Frequency Beam (LFB)) and the other with a high natural frequency (High-Frequency Beam
(LFB)). The two beams are coupled through repulsive magnetic force between two magnets attached as tip masses of the beams and facing each other at the same polarity. The HFB tip magnet acts as an upper electrode of a triboelectric energy harvester, while a PDMS insulator is attached to a lower electrode. When the structure is subjected to base excitation,
the triboelectric layers generate an electrical signal via contact-separation impact motion between the triboelectric’s layers. The magnetic coupling converts low-frequency vibrations to high-frequency self-oscillations, and an electrical signal is generated at the LFB resonance. By controlling the distance between the two magnets, the structure will vibrate in either
mono or bistable oscillations. A lumped parameter model of a two-degree of freedom system is proposed to simulate the dynamic behavior and the generated electrical signal. The static and dynamic behaviors are investigated at different separation distances selected to cover the monostable, transition, and bistable regions. In addition, a parametric numerical analysis
for enhancing the electrical output and optimizing the harvester functionality. This study shows the feasibility of utilizing Vibro-impact triboelectric energy harvesting for frequency up-converting applications from ambient vibrations. Since the ambient vibrations are below 100 Hz while most machines and equipment operate
relatively at high frequencies (more than 70 Hz), we also propose a theoretical study to harvest energy from high frequencies using a frequency-down bistable piezoelectric energy harvester mechanism. We investigate the energy harvesting benefit in the down-conversion of a high-frequency signal to a low-frequency signal utilizing magnetic coupling. A high-
frequency driving beam triggers a low-frequency generating beam. We use a spring-mass-damper equivalent model to understand the operation mechanism of the proposed piezoelectric vibration energy harvester. Based on the theoretical model, the static and dynamic effect of magnetic nonlinearity on the performance of the proposed piezoelectric vibration energy harvester is numerically analyzed. The targeted applications are the down-conversion and the filtering of high frequencies and mass sensing, particularly the harvester’s behavior for mass sensing applications.

Date of publication

Spring 4-28-2023

Document Type

Thesis

Language

english

Persistent identifier

http://hdl.handle.net/10950/4181

Committee members

Alwathiqbellah Ibrahim, Ph.D, Nael Barakat, Ph.D., Nelson Fumo ,Ph.D.

Degree

Master of Science in Mechanical Engineering

Additional Files
Thesis Final Approval Form-Abumarar.pdf (43 kB)
Approval from graduation department
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Available for download on Tuesday, April 22, 2025

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