Piezoelectric vibration energy harvester with tapered substrate thickness for uniform stress

This paper presents modification in the thickness profile of bimorph cantilever type piezoelectric vibration energy harvester (PVEH) to achieve uniform stress along the beam length. The thickness profile is obtained by varying the thickness of substrate layer and keeping the thickness of piezoelectric layers constant. Analytical expressions for the cantilever beam displacement, stress on the beam and generated voltage are derived and solved for sinusoidal input excitations. The results from the analytical expressions are validated with that of the finite element (FE) analysis of an identical PVEH. The generated power and stress distribution in the proposed PVEH are compared with that of an equivalent conventional PVEH of uniform thickness. Compared to the conventional PVEH, in the proposed PVEH the generated power is 20% higher for an input acceleration of 0.2g, and the stress on the proposed device is found to be uniformly distributed with the peak stress value reduced significantly by 46%.