Research On Harvesting Ambient Vibration And Acoustic Energy By Multi-stable Piezoelectric Configuration

With the development of wireless sensor systems and micro-electromechanical systems,lowpower microelectronic devices have applied in many areas including aerospace,military defense,industrial automation and control,remote monitoring and control.The traditional batteries are not powerful enough to satisfy these microelectronic devices.Recently it receives a significant attention to convert the ambient vibration into electricity.Piezoelectric energy harvester could convert vibration energy in the environment to electrical energy so as to power low-power microelectronic devices.A major limitation of traditional linear resonant energy harvesters is that the power generation performance of the device relies on the resonance with the excitation.But vibration energy existing in most environments is made up of many frequencies.Thus such a resonance-based piezoelectric energy harvester becomes inefficient for real-world applications.In this paper,some novel energy harvesting scenarios are presented.The application of piezoelectric pumping device in vehicle-bridge system is introduced and analyzed.Quad-stable and penta-stable energy harvesters are presented and studied.Theoretical analyese,numerical simulations and corresponding experiments are carried out to show that the presented energy harvesters are preferable in harvesting vibration energy.Finally,a bi-stable acoustic energy harvester is proposed to scavenge noise energy.The experimental results show that the proposed bi-stable acoustic energy harvester is preferable to the linear one in harvesting environmental noise energy.The main work and research results of this paper are as follows: 1.The vehicle-bridge system is modeled for analysis.The corresponding equations of vibration under vehicle traversing bridge is deduced.The vibration energy of vehicles traversing the bridge is investigated,which can be harvested by a cantilever beam type piezoelectric energy harvester from a bridge vibration.The results show that the parameters such as vehicle speed,body mass and the location of the piezoelectric energy harvester have a great influence on energy harvesting.There exist a critical traversing velocity which is beneficial to energy harvesting when the vehicle crossed the bridge.It is also beneficial to the energy harvesting such as increasing the body mass increases,the locating the piezoelectric energy harvester near the middle span.2.A novel quad-stable energy harvester is presented to harvest vibration energy.The electromechanical coupling equation of the quad-stable energy harvester are obtained using energy-based methods.The potential energies of the bi-stable and quad-stable energy harvesters are derived.The quad-stable energy harvester is superior to the bi-stable one due to lower potential barrier and wider distance between the outmost potential wells,which implies that the quad-stable energy harvester needs relatively lower excitation energy to cross potential barriers and generate large voltage output under harmonic excitation.The numerical simulations and experimental verification are carried out at different levels of excitations.Results show that the quad-stable energy harvester owns a smaller threshold and a wider range of frequencies for occurrence of snap-through than the bi-stable one.3.The response of the quad-stable system under random excitation is studied.Four stable equilibrium positions can be realized in static state of the quad-stable energy harvester within a certain ranges of separation and gap distances.A series of numerical simulation and experimental results show that the quad-stable energy harvester can create a larger deflection and generate a higher voltage than bi-stable one nearly over the whole range of excitation intensity.The quad-stable energy harvester can be optimized by controlling the gap distance and separation distance to maximize the energy harvester efficiency at a given random excitation intensity.4.We proposed a penta-stable energy harvester and demonstrate it can attain a high efficiency in harvesting vibration energy.To realize the best penta-stability,the four magnets are mounted on two inclined planes and oriented with their opposite poles facing the tip magnet such that the ensuing attraction forces create five stable equilibrium positions.Compared with bi-stable energy harvester,the potential energy of penta-stable energy harvester owns shallower potential wells and farther outermost potential wells,implying easy snap-through and large amplitude.The validate experiments are carried out and the results prove that the penta-stable energy harvester can realize snap-through between potential wells easier and generate higher output powers than the bi-stable one even at a weak random excitation.5.In this paper we proposed a bi-stable acoustic energy harvester to scavenge noise energy.The potential energy diagram shows that the depths and widths of potential wells are related to separation distance between two magnets.The experimental results proved that the bi-stable acoustic energy harvester could execute snap-through at a relatively low intensity of noise.The bi-stable acoustic energy harvester can transfer the noise energy to a low frequency response by snap-through.It is found that the separation distance between two magnets is a key factor for occurrence of snap-through.Therefore,for a given sound pressure level,the bi-stable acoustic energy harvester can be optimized by altering separation distance between two magnets and attain coherence resonance to generate the maximum output power.Based on the study of the piezoelectric vibrating system based on environmental vibration,this paper can provide theoretical guidance for improving conversion efficiency of piezoelectric energy harvester.