Design Of Resonant Frequency Self-Tunable Piezoelectric Energy Harvester For TPMS Application

TPMS can monitor tire pressure,temperature and other factors in real time,so as to greatly reduce traffic accidents caused by abnormal tire pressure.It has been widely concerned by automobile users.At present,most of power supplies for TPMS are button batteries,which have some shortcomings such as having short lifetime,needing high maintenance costs,causing much pollution to the environment and so on.The micro energy harvesting technology that harvests and converts the vibration mechanical energy and strain energy generated by the rotating tire into electrical energy has the advantages of long lifetime,maintenance-free,environment-friendly and so on,becoming one of the effective technical solutions to replace button batteries to power TPMS.In this paper,aiming at the technical problem that the traditional piezoelectric energy harvester has a narrow working band and is difficult to provide stable electric energy for TPMS in a wide speed range,the structural design and optimization research of the resonant frequency self-tunable piezoelectric energy harvester is carried out in order to realize the power supply for TPMS in the speed of 60-120km/h.Based on the characteristics of the rotary vibration,a self-matching method of resonant frequency is proposed.The natural frequency of the vibration energy harvester can be adjusted by changing the center position of the mass with its centrifugal force,so as to match the rotary frequency.Based on this method,a new structure of resonant frequency self-tunable piezoelectric energy harvester is proposed,and the feasibility of the structure is theoretically qualitatively analyzed.Then,based on Ansys,the structure optimization design model of the piezoelectric energy harvester is established,including a simulation model of the main beam-mass structure and a simulation model of the mass-auxiliary beam structure.Based on the established model,the influence of centrifugal force on the resonant frequency of the device is analyzed.The influence of structure parameters such as cantilever beam,mass block,auxiliary beam,and piezoelectric layer on the speed working range,output voltage,and output power of the energy harvester are studied.Finally,according to the power supply requirement and device reliability requirement of TPMS,the optimal design of the device structure is completed.The simulation results show that the optimal structure size is: cantilever beam: 42 mm long,11 mm wide,76μm thick;piezoelectric layer: 42 mm long,11 mm wide,10μm thick;mass: 12 mm long,16 mm wide,4mm thick;auxiliary beam: 3.86 mm long,7.18 mm wide,80μm thick.Under this size,the resonant frequency self-tunable piezoelectric energy harvester has good output characteristics in the speed range of 60-120km/h.The average output voltage and average output power of the device is 21.07 V and 89.38μW,respectively.