MEMS piezoelectric energy harvester to power wireless sensor nodes for machine monitoring application

Piezoelectric vibration energy harvesters find an important application in powering the wireless sensor nodes used to monitor the condition, wear and tear of AC machines which vibrate at twice the line frequency i.e., 100 Hz. The challenge in the design is to make the resonant frequency of the energy harvester equal to 100 Hz keeping the size less and to obtain the maximum possible output voltage. In this paper various geometries of cantilever beams of a constant length 5 mm have been investigated to get significant reduction in the resonant frequency and to achieve nearly 100 Hz. A new Perforated Tapered shaped cantilever beam has been proposed. The achieved resonant frequency of the final proposed perforated Tapered structure with proof mass is 101 Hz, which is 27.5% lower than that of the commonly used rectangular structure with proof mass of same dimensions. The peak voltage output of the proposed structure is 7.5 V. The proposed structure can be used to generate voltage from the vibration of the AC machines and can provide a long-life solution to the need of powering the batteries in wireless sensor nodes.