| In the past two decades,with the continuous development of microfabrication technology and microelectronics technology,the miniaturization of wireless sensors,data transmission and medical implants and the development of low energy consumption devices have been promoted.Traditionally,chemical battery-based power supply not only increases the size and quality of the system,but also has limited energy supply life and is difficult to replace.Therefore,in order to overcome the shortcomings of traditional chemical battery power supply,it is necessary to find a long-term and effective power supply energy harvesting technology.Vibration energy harvesting technology provides a new power supply mode for the self-supply of low-consumption devices.Because the nonlinear cantilever beam structure can exhibit good vibration response performance in a wide spectrum range,the vibration energy harvesting method based on the nonlinear cantilever beam has attracted wide attention in recent years.In this paper,the vibration energy harvesting system of a nonlinear bi-stable piezoelectric cantilever beam is taken as the research object.Aiming at a kind of narrow-band random vibration with center frequency and certain bandwidth,the influence of narrow-band random excitation on system response and energy harvesting is discussed.The response mechanism and energy harvesting characteristics of the system under narrow-band random excitation are studied.The main results of the research are as follows:1.The lumped parameter model of bi-stable piezoelectric cantilever beam is established,and the influence of structural parameters on the potential energy function of the system is analyzed.The characteristics of the linear stiffness and the non-linear stiffness of the system are given.The positive and negative dividing point of the linear stiffness is the dividing point of the monostable and bi-stable of the system,and the nonlinear stiffness monotonously increases with the decrease of the magnet spacing.2.By equivalent linearization of the nonlinear system,it is proved that the system has equivalent linear natural frequencies under different magnet spacings.The magnet spacing of minimum equivalent linear natural frequencies correspond to the positive and negative dividing point of the linear stiffness,i.e.the dividing point corresponding to the system's monostable and bi-stable state.3.The influence of center frequency of narrow-band random excitation on system response is revealed.Theoretical analysis and numerical simulation show that when excited by the narrow-band random excitation with a certain bandwidth and intensity,there is always a constant interval between magnets making the system produce a peak output,which is like that the bi-stable system produces the peak output at optimal spacing under broad-band excitation.On the other hand,there are also more one or two different magnet spacings making the system produce peak outputs while excitation' center frequency changes within a certain range,and the peak outputs are formed by bi-stable or single-stable "resonance" the system induced at the equivalent linear natural frequency.4.The influences of different intensity and bandwidth of narrowband excitation on system output are as follows: the output voltage at the peak spacing increases with the increase of intensity,but the value of each peak spacing shifts;although the change of bandwidth does not change the value of peak spacing,with the decrease of bandwidth,the output voltage at the fixed peak spacing decreases gradually until it reaches zero,while the output voltage at the bi-stable or monostable "resonance" spacing increases gradually.5.The vibration energy harvesting system of bi-stable piezoelectric cantilever beam is built.The experiment verifies that the variation rule of output voltage with the narrow-band random excitation and the magnet spacing.The experimental results are in good agreement with the simulation results. |
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