Research On PZT Energy Harvesting Based On Multiphysics Coupling

Since the 21 st century,microelectronics technology and ultra-large-scale integrated circuits have continued to break through,and the power consumption of microprocessors and wireless sensors has been continuously reduced with its volume continuously shrinking,incompatible to which,the development rate of traditional chemical batteries is obviously lagging behind.The problems of large volume,short life,low energy storage density and environmental pollution have become increasingly prominent,which has become the primary shortcomings for suppressing the development of microelectronic devices.Piezoelectric energy harvesting technology was designed to assist in the supply of outdoor wireless sensors and portable microelectronic devices,based on the piezoelectric effect,converting the vibration energy in the environment into the electric energy easy to use by transforming materials,structures and systems.In this paper,the mechanical model of piezoelectric cantilever beam and spoke type fixed beam structure were established,and the expressions related to the mechanical properties such as resonance frequency and amplitude are derived.In that case,we further established an electromechanical coupling model of piezoelectric energy harvester.Combined with the differential equation of motion and the piezoelectric coupled equation,the frequency domain response and matching impedance expression of the load voltage are solved,which provides theoretical support for improving the performance of piezoelectric energy harvesters in the future.Besides,we established the finite element model of cantilever beam and spoke structure in this paper,carrying out the piezoelectric frequency domain response analysis by using COMSOL finite element multiphysics coupling simulation software.After the parameters affecting the piezoelectric energy output,including the beam shape,the thickness of the substrate,the thickness of the piezoelectric material,and the substrate material were discussed,we investigated the effects on the operating frequency,equivalent impedance and effective working bandwidth of the piezoelectric vibration system.This led to the establishment of a piezoelectric vibration energy harvesting experimental platform,leading out the load voltage and matched impedance frequency domain response experiments of the cantilever beam and spoke type piezoelectric energy harvester.Experiments show that the piezoelectric cantilever beam has a bandwidth of 6HZ,while the effective bandwidth of the circular array system reaches 32 Hz,and the maximum power is increased from 0.05 mW to 0.25 mW,which verifies the feasibility of the array mode to widen the frequency band and increase the power.Meanwhile,the frequency domain experiment of the fixed-spoke structure in this paper also shows that,under the action of 1g acceleration,the open circuit voltage can reach 29 V,and the maximum output power can reach 1.7mW at 134.7k? load.Regarding on the experiments above,we improved the basic energy recovery circuit by voltage monitoring,energy storage medium and voltage regulator module,reducing the load voltage fluctuation caused by the vibration state and the internal resistance of the system,further achieving a regulated DC high power output.As for environmental factors,this paper includes temperature and magnetic fields into the scope of research,analyzing the working state of the piezoelectric vibration energy harvester under temperature abrupt change and temperature,which was followed by Introducing a nonlinear magnetic force.We made the magnets symmetrically repulsed,and adjust their spacing appropriately,achieving the purpose of frequency modulation of the piezoelectric vibration system.At the same time,the effective excitation frequency domain of the piezoelectric vibration system is adjusted from 109~124Hz to 120~136Hz,which expands the effective bandwidth to a certain extent.When arranging the magnets to be “attracted above and repulsed below”,there would be a synchronous increase on working pulse width and output power,demonstrating a new possibility to improve the performance of the piezoelectric vibration energy harvester.