Research On Dandelion-type Multi-directionbroadband Piezoelectric Vibration Energy Harvesting

Vibration energy exists everywhere in the nature, harvesting vibration energy to power wireless nodes or other autonomous electric devices can greatly reduces use of batteries, which is a type of energy-saving and enviroment-friend green enegy technology. It’s of great researching value. In the recent years, vibration energy harvesters has been developed greatly, however, the researches related to the adaptation to the ambient vibration frequencies and directions are put forward a little, which is requred for further steps.This paper presents a dandelion-like ambient vibration energy harvester that can harvest wide-band frequncy and multiple dirrection vibration energies. In order to systematically explore the electric generation features of the harvester, the multi-direction capability is investigated by structure design. Firstly, the therotical electric generation model of a single cantilevered beam is established using methods of vibration composition and decomposition. The influence laws of the main parameters of the cantilevered beam and the ambient vibration direction to the electric generation features are anlyzed numerically. On the basis of the above anylyses, theoretical power generation model of the dandelion-like vibration energy harvester is set up in the case of multiple directions. The influence laws of the ambient vibration direction to the electric generation features is anlyzed numerically as well. Afterwards, on the basis of the above models, the parameters the dadelion-like structures subject to a typical bridge vibration frequencies band is optimized. To verify theoretical anylyses results of the dandelion-like structure, its vibration is simulated employing ANSYS. Finally, experiment of the output energy of the energy harvester under the typical bridge vibration excitations ia carried out in order to verify the modelling and the simulation. The above researches is expected to be a reference to the related energy harvester design for direction adaptation. Considering the request for wide-band frequnce responses, structural design mathod for expanding the frequency band is researched. Firstly, the frequencies features of several typical vibration enviroments are anlyzed, and the demand of an energy harvesting structre to meet with the ambient vibtation is put forward. Then, the parameters of the dandelion-like energy harvesting structure is given for the given frequency range. Finally, the harvester prototype is fabricated and the experimental bench is setup in order to verify the frequency expanding feasibility. Results shows that the energy harvesting ability can be imporoved by structural design. The above researches is expected to be a reference to the related energy harvester design for frequency adaptaion.In addition, as an important part of vibation energy harvester, the charging control and adaptive tuning control strategies are investigated. On the basis of investigations of energy harvesting circuits for one charging source, the switching time of SECE circuit and SSHI circuit has been modeled and analyzed; Consideration of output characteristics of multi-sources with different phases, the parallel SECE circuits and parallel series-SSHI circuits have been analyzed; Moreover, an approach of automatic switch charging interface circuit adaptive for multi-directional vibration energy harvesting has been proposed, it can select the optimal charging source to obtain the maximum output power by detecting the direction of environmental vibration, thus reducing the amounts of electronic components and power consumption.According to the principle of the single piezoelectric cantilever structure obtaining the maximum output power at its resonant frequency, a semi-active frequency self-tuning method based on SSSC technique and piezoelectric self-sensing actuator technique has been proposed here. It realizes the decoupling of sensor signal and drive signal through the time-sharing multiplexing of piezoelectric element itself, thus acquiring the real-time state of motion of the piezoelectric cantilever structure and regulating the stiffness of the piezoelectric cantilever beam based on SSSC technique, thereby, realizing the goal of frequency adaptive adjustment within a certain frequency range.A sets of experiments for the dandelion like vibration energy harvester are carried out finally, the results shows that it is capable for multi-directional and wide-band ambient vibration energy harvesting. The research results of this paper is expected to be referenced by practical vibration energy harvester disign in future.