Stiffness compensation for piezoelectric energy harvesting

Stiffness compensation for piezoelectric energy harvesting: Improving the efficiency at low-frequency vibrations

van de Wetering, Erik (TU Delft Mechanical, Maritime and Materials Engineering)

Blad, Thijs (mentor)
van Ostayen, R.A.J. (graduation committee)
Hunt, A. (graduation committee)
Polinder, H. (graduation committee)

Delft University of Technology

Mechanical Engineering | Mechatronic System Design (MSD)

2021-01-26

In the field of vibration energy harvesting, vibration energy is tranduced to electrical energy to power small, low powered devices. Many energy harvesters are produced in the form of a resonator, where resonant amplification enables efficient operation of the energy harvester. At low frequencies below 10 hz, input motions quickly increase for a constant input acceleration and resonant amplification results in energy harvesters that are too large to implement them. A solution is sought in creating a nonresonant energy harvester. The stiffness of a strongly coupled piezoelectric beam is compensated by adding negative stiffness to bring it to a near statically balanced state. This negative stiffness is embodied by attracting magnets. To model the dynamics and voltage output of the harvester, a modal analysis based distributed parameter model is used and further developed by including negative stiffness and force-displacement measurements of the stiffness compensated piezo. To investigate the mechanical behaviour of a compensated piezo, force-displacement measurements are carried out at different deformation speeds and load resistances. From these measurements, it has been observed that the stiffness of the compensated piezo strongly depends on the connected load resistance and the deformation speed. Furthermore, memory effects in piezoelectric hysteresis found in actuators such as curve alignment and wipeout have also been confirmed in force-displacement measurements. The performance of the harvester has been evaluated by exciting it on a linear air bearing stage. It has been found that for excitations between 2 and 6 hz, the error in RMS power between simulation and measurement remains below 10%. For its range of excitation, this harvester has been observed to be the most efficient with respect to prior art from literature. Therefore, stiffness compensation of a piezoelectric energy harvester can be considered as a successful method to improve the efficiency at low frequency excitation.

Vibration Energy Harvesting
Piezoelectricity
Stiffness compensation
Zero stiffness
Static balancing

http://resolver.tudelft.nl/uuid:de2bd90f-033f-49c1-aa58-23c55104ecc3

2022-02-01

Student theses

master thesis

© 2021 Erik van de Wetering