Power optimization and effective stiffness for a vibration energy harvester with displacement constraints

Abstract

This paper presents experiments on how to approach the physical limits on power from vibration energy harvesting under displacement-constrained operation. A MEMS electrostatic vibration energy harvester with voltage-control of the system stiffness is used for this purpose. The power saturation problem, when the proof-mass displacement reaches a maximum amplitude for sufficient acceleration amplitude, is shifted to higher accelerations by use of load optimization. In addition we demonstrate the effect of varying the electromechanical coupling k 2. Measurement results show that harvested power can be made to follow the optimal power of the velocity-damped generator also for a range of accelerations that implies displacement constraints. Comparing to the saturated power, the power increases 1.5 times with the optimal load for electromechanical coupling k 2 =8.7%. The improvement is 2.3 times for a higher coupling of k 2 =17.9%. The obtained system effectiveness exceeds 60%. This work shows a first demonstration of reaching optimal power in the intermediate acceleration-range between the two extremes of maximum efficiency and maximum power transfer. The experimental results follow the theoretical results for a device with both load and stiffness tuning surprisingly well despite only optimizing the load here. We compared a linearized lumped-model of the device with the same augmented by end-stop nonlinearities. The comparison shows that an effective stiffness due to end-stop impacts in the latter model closely matches the optimal stiffness for the former model and therefore can explain why the experimental output power is close to optimal despite lack of deliberate stiffness tuning.

Self-Powering Wireless Sensor Networks in the Oil and Gas Industry

“…Another challenge is widening the bandwidth of these micro harvesters [37][38][39][40][41][42]. Different MEMS designs and solutions were proposed to overcome these challenges while maximizing the output power of these micro harvesters [43][44][45][46][47][48][49][50][51][52][53][54]. There is still more to do to overcome challenges related to the optimization of power harvested through MEMS devices, and how to increase the broadband capability of the MEMS harvesters while optimizing the power generated from the device.…”

Nanogenerators and Self-Powered Systems

“…Another challenge is widening the bandwidth of these micro harvesters [37][38][39][40][41][42]. Different MEMS designs and solutions were proposed to overcome these challenges while maximizing the output power of these micro harvesters [43][44][45][46][47][48][49][50][51][52][53][54]. There is still more to do to overcome challenges related to the optimization of power harvested through MEMS devices, and how to increase the broadband capability of the MEMS harvesters while optimizing the power generated from the device.…”

Post-grazing dynamics of a vibro-impacting energy generator

“…The models of vibro-impact systems include piecewise linear stiffness [48,49] as well as rigid barriers and instantaneous impacts leading to a velocity jump for inelastic impacts. EH devices that utilize vibro-impact dynamics as a main energy absorption mechanism were developed and studied in a number of publications [50][51][52][53]. While often such systems are limited to computational results only, certain settings allow an analytical or semi-analytical treatment when the motion is composed of a sequence of trajectories described (semi-)analytically.…”