The Basic Research On The Piezoelectric Energy Generating Used For TPMS

In this issue ,we talked about using piezoelectric materials transforming the mechanical energy of the tires'vibration into electrical energy during the moving of the car ,to power the monitoring module of the TPMS(Tire Pressure Monitoring System),substituting the traditional battery.People start to seek another energy source because of the limited lifespan of the battery, owing to the good piezoelectricity and without electromagnetic interference, people pay much attention to piezoelectric materials.In recent decades,plenty of foreign researchers or experts have been studying this materials and have made a lot of achievements.Through a great deal of studying and experiments,they have succeeded in applying this material into MEMS(Micro electromechanical Systems),for instance, the success of applying into the monitoring system of the of migratory bird and embedded in the heart pacemaker ,etc.All of this achievements have proved the feasibility of integrating piezoelectric materials and MEMS,based on this ,we expand the research of using piezoelectric materials to power the monitoring module of TPMS.The content of this essay can be divided into five parts,in the following passages,we will make a simple statement of each part:The first part consists of two aspects,one is the introduction of achievements ;another is the statement of necessity of fixing TPMS in the car and the broad potential prospect of the TPMS.The second part includes the presentation of performance parameters of piezoelectric ceramic,the piezoelectric equation together the mechanics with electrics,the support mode , vibration mode and excitation style of the piezoelectric vibrator.The performance parameters are the criteria when making a choice of piezoelectric ceramic; the piezoelectric equation is the groundwork of modeling the piezoelectric vibrator and the key to figure the power generation capability of the piezoelectric vibrator in theory; the support mode , vibration mode and excitation style make us have a clear understanding of the principle of how a piezoelectric generator works.This chapter is the basic of piezoelectric vibrator, we should make sure of having a good command in order to go on the next works.The third part is about the mathematic modeling of the piezoelectric vibrator .when the ratio of length to width is longer than 10, piezoelectric vibrator adopting the cantilever support mode can be modeled as a cantilever beam;on the contrary ,we should model it as a cantilever plate,which has a different mode shape equation and characteristic equation.Through the modeling ,we can figure out the energy generation performance when applied a static load and the relations between the natural frequency with the structure dimension.This part is the the foundation of optimaziation design.The fouth part is one of the importance and the pre-work of our piezoelectric power generator for TPMS.During this part,we dicussed three questions:the first one is to find the effection to the natural frequency if we changed the acting point of the mass block which attached to the piezoelectric vibrator through experiments;the second one is power storage device,because the piezoelectric vibrator generates a high voltage,yet a low current ,can not power the TPMS directly, we need to store the energy firstly,through comparion and experiments ,we finally dicide to take super-capacitor as our storage device;the last one is about the energy extracting circuit in order to extracting the energy effectively,through the experiments, we found that if we add a filter capacitor which capacity is 10uF into our circuit,the extracting effection would be better. The fifth part is also the key chapter of this essay .In this part ,we presented the piezoelectric energy generator device for the TPMS and proved the feasibility of our structure by experimenting on the car.adopting two devices,only in two hours ,we could make the TPMS work,which is far smaller than the discharging time when powering for the TPMS.In order to shorter the charging time further ,we may adopt more devices.