Abstract:
Alongside the ever-progressing technological advancement, the size of devices shrinks
down and therefore, warrants a wireless power source which may also be the only option
for certain devices like micro-aerial drones and health monitoring wrist bands. Researchers
have published various studies on vibrational energy harvesters that are able to provide
such untethered power while being meso- or microscale. However, the harvesters face
many obstacles two of which are the total output power and limited operational bandwidth.
Most of the harvesters show a virtual limit in providing an electrical output over few
microwatts while maintaining micro- or mesoscale dimensions. This thesis presents a novel
design for a multi-resonant piezoelectric vibrational energy harvester (PVEH) based on
low frequency ambient vibration environments. The harvester follows the design of multifolded type and is made of aluminum body with steel masses and Lead-Zirconate Titanate
(PZT-5A) piezoelectric element. The multi-resonant PVEH comprises of one main beam
and 3 branched beams which are designed to resonate at different frequencies. This in turn,
increases the operational bandwidth and generates more electrical output power.
At first, we highlighted the problem analytically. The mass-spring-damper system equation
shows what aspects can be modified in order to achieve the desired goal. The next step is
the design of the harvester in SolidWorks followed by analysis in COMSOL Multiphysics.
Once the design was set and declared efficient by analysis of mode shapes and system’s
frequencies, the fabrication was carried out. Experimental setup included mechanical
shaker connected to an amplifier and a signal generator. The harvester was fixed to the
shaker in both setups, namely, Test 1 with digital oscilloscope and Test 2 with Dynamic
Signal Analyzer. Experimental results agree with the theoretical values in the range under
50 Hz with multiple peaks giving the peak output power to 42.3 μW. This output is based
on low harmonic acceleration (0.2 ms-2).
