外文翻譯--懸臂梁壓電的微功率的優(yōu)化設計（英文）

1、 300Proceedings of e-ENGDET2006 5th International Conference on e-Engineering PZT; micro power 1 INTRODUCTION Energy problem, as the bottleneck of the integration, miniaturization and even micromation of modern produ

2、cts, has been widely researched toward a solution of micro power supply with advantages in size, weight and endurance. The micro piezoelectric cantilever generator can convert oscillation energy to electrical energy

3、with advantages in size, weight and integration. For the power conversion by means of elastic deformable structures, periodically changing forces to the generators are necessary. This can be achieved by the help of a

4、hydrodynamic instability developing after a flow disturbance as known as a von Kármán’s vortex street [1,2,3]. Hence, in the design of cantilever for micro power generator we set three constraints for desig

5、n, and optimized the geometric shape of a piezoelectric cantilever for micro power generator through the static theoretical analysis. 2 MECHANISM OF PIEZOELECTRIC CANTILEVER GENERATOR Piezoelectric ceramics, as a comm

6、on semiconductor material in the design of MEMS devices, have two characteristics: one is the direct piezoelectric effect, i.e., the materials will induce electric potential once they are subjected to mechanical defo

7、rmation, the other is the inverse piezoelectric effect such that the deformation will occur when the materials are subjected to an electric load. Therefore, piezoelectric ceramics have found wide application in engin

8、eering. Fig. 1 shows the sketch map of the energy conversion mechanical to electrical, current signal can be seen in voltmeter with external force. Fig. 1 The conversion of mechanical to electrical energy Driven by ext

9、ernal periodical force, micro cantilever moves up and down resulting bending. During bending, one side is stretched while the other one is compressed, these mechanical deformation lead to a charge separation inside th

10、e piezoelectric ceramics. Striped electrodes that are applied at the cantilever surface collect the charge, and finally the electric power output is delivered to MEMS 302change of length is more efficient than that of

11、thickness to induced more charge. The variation of width does not affect the amount of charge as we can expect from equation (3). The resonance frequency does not depend on the width. The length is more powerful para

12、meter than thickness to adjust it. Hence more charge requires longer and thinner cantilever, but we cannot extend thumb of design rule because it is constrained by limit of tip displacement, resonance frequency and st

13、rength. Fig. 4 Maximum stress at PZT top with extern force and Resonance frequency of beam 4 OPTIMIZATION OF GEOMETRY FOR MAXIMUM ENERGY In the design of cantilever for micro power generator we set three constraints f

14、or design. One is tip displacement, the second is resonance frequency and the third is yield strength. Under those constraints we optimized the geometry of cantilever to get the maximum output power. 4.1 Constraints o

15、f micro cantilever for maximum energy The first design constraint is the tip displacement of cnatiliever. That modification of geometry cause large tip displacement in PZT and silicon layer, hence the change of leng

16、th and thickness should meet tip displacement constraint, as shown in equation (7). The largest value of displacement l ffor currently reported MEMS microgenerator is 0.9 mm [5]. l f f (8) where Hz Force 50 = ωis

17、the frequency of external load. The third constraint is imposed on yield strength, and that modification of geometry cause big stress in PZT or silicon layer. Hence we should change length and thickness as long as the

18、 cantilever does not break, and the constraint are described by (9). ( ) yield PZT PZT silicon , , max σ σ σ< ω ω σ σ(13) We numerically solve this problem changing the variable in a certain range. Given the extern

19、al periodical force is at the end of beam as 10 F N μ =and width as 20 m μ , we obtained optimal thickness ( 13 A t m μ = ) and length ( 1.8 L mm = ) as shown in Fig. 5, and the optimal charge is 10 1.40 10 C ? ×

20、 , the voltage is 1.29V and the output energy is 11 9.0 10 J ? × . Given the external periodical force is at the beam as 10 / q N m μ =and width as 20 m μ , we obtained optimal thickness ( 12 A t m μ = ) and len