Dynamic Analysis And Experimental Study Of Adjustable Frequency Bi-stable Piezoelectric Energy Harvester

Vibration energy is widely present in all aspects of production and life,it is so large that the waves impact the waves generated by the embankment and various construction machinery during the construction process,and the vibration generated by th e bridge when the vehicle passes and the vibration generated by the vehicle itself.If the vibration energy is collected and converted,it will have a very promising future.Since the collection of vibration energy is not affected by external factors such as weather,temperature,humidity and light,it has become one of the hotspots of current energy collection research.Studies have shown that when the vibration frequency in the environment is equal to or close to the natural frequency of the energy harvester,the system produces the maximum vibration amplitude,at which point the output energy reaches its maximum.However,the natural frequency of the traditional energy harvester is fixed,and the vibration frequency in the real environment is constantly changing.If the natural frequency of the trap does not match the ambient vibration frequency,the system will not be able to reach an effective working state,and the output power will be greatly reduced.How to ensure that the energy harvester can still reach the resonance state when the vibration frequency of the external environment changes,the scholars have conducted extensive research and proposed a series of programs.At present,domestic and foreign scholars propose that the solution to solve the environmental vibration frequency matching can be roughly divided into two categories:widening the working bandwidth of the energy harvester,enabling it to work effectively in the environment of broadband excitation;adjusting the capture according to changes in the external excitation environment The natural frequency of the energy device is matched to the excitation frequency in the environment to reach the resonance state.Based on this,this paper proposes a scalable frequency bistable piezoelectric trapping method and carries out related experimental research.The main research contents are summarized as follows:(1)The structure diagram of the adjustable-frequency piezoelectric energy harvester model is given.The motion analysis of the system is carried out and the equation of motion of the system is obtained.The electrical equation of the system is obtained according to Kirchhoff's current law.According to the static bifurcation analysis of the equilibrium point,the range of magnet spacing when bistable motion occurs is obtained.The state in which the system enters sequentially with the change of the excitation frequency is analyzed.When the external environment excitation frequency changes,the process of adjusting the magnet spacing from 20mm to 12mm,the capture energy band shifts to the right,from 17-25Hz to 17-72Hz,and the capture band is effectively broadened.(2)Based on the simulation,the adjustable frequency bistable piezoelectric energy capture device was designed and fabricated,and related experimental research was carried out.The experimental results of the first chapter are analyzed experimentally.It is verified by experiments that the system enters the state sequentially as the excitation frequency increases.In addition,the system was tested for frequency modulation.The system output voltage was 0.005V before frequency modulation,and the system output voltage reached 4.7V after frequency modulation.The frequency modulation effect is obvious.(3)Analyze,compare and select the types of rectifier circuit,filter circuit and voltage regulator circuit in the capture circuit.According to the rated voltage and current of the load,the calculation and model selection of the relevant parameters of the rectifier diode and the Zener diode are carried out,and the values of the filter capacitor and the current limiting resistor are calculated.The designed capture circuit was simulated and verified by Multisim software.The results show that the AC voltage is converted by the capture circuit and the output is a relatively stable DC voltage.The voltage is within the working range of the LED.After a period of energy storage,the LED can be powered to operate normally.