The Structural Research Of Micro Piezoelectric Energy Harvester Driven By Low-Frequency Ambient Vibration

With the development of wireless sensor network, the continuous power supply has been a key problem to be solved. Considering that the vibration energy exists everywhere among our lives, the machine run, bus travel, earthquake and even weak voice can supply as vibration energy. Some kinds of energy scavengers that transfer vibration to electric to supply micro-electronic devices have been developed. Among which the micro piezoelectric energy collector is widely used with its high electromechanical coupling performance and high power density and no external power supply. On the other hand, using piezoelectric material to power sensor nodes can also reduce the environment pollution caused by waste batteries.Generally Piezoelectric energy harvester is manufactured to supply wireless sensor network and appears in tiny small size based on MEMS (Micro-Electro-Mechanical System) technology. The conventional straight microstructure piezoelectric energy harvester’s natural frequency is as high as KHz, which makes it hard to resonate with the ambient low-frequency vibration source, and the power the harvester provides is insufficient for sensor nodes’normal work. This paper aims at improving the structure of piezoelectric energy harvester to reduce its natural frequency and to improve its output voltage and power.Based on the theoretic and finite element simulation, the paper analyses the zigzag structure’s power generation capacity profoundly. Firstly, the mathematic model of the zigzag structure is built to learn the relationship between geometric parameters and the harvesters’ natural frequency and output voltage and power. Secondly the finite-element model was set up adopting finite-element analyzing software ANSYS to conduct static analysis, modal analysis and harmonic response analysis. The results show the rules of change in output voltage and power which depend on structure’s geometric parameters, and establishes the base of further optimizing design for piezoelectric vibrator. The simulation shows that the natural frequency decreases when the thickness of the beam decreases and the length and thickness of the block increases. The natural frequency also decreases when the length and width of the beam or the number composing the zigzag structure increases. The first natural frequency is142Hz when the zigzag cantilever is consisted of10beams, which is low enough to resonate with the environment vibration. The harmonic analysis shows the relationship between the output characteristic and the structure’s dimensions and so on. The zigzag energy harvester’s output voltage can reach10-20V when it is composed by10straight beams, and the optimal load is200KΩ, the output power is1.66mwah, which is hopeful to supply for the micro sensor nodes’ discontinuous work.