The Research Of Nonlinear Dynamic Characteristics Of Electrostatically Actuated Micro-bridges

Along with rapid development of science and technology and unceasing demand of life,MEMS has been applied in more and more fields for advantages of tiny,precise and accurate,gradually replacing macro-system to achieve equal function better.It is necessary to equip with massy theory for getting increasing development of MEMS.Researches on MEMS are mainly concentrated on the static analysis and dynamic analysis of ideal structures,ignoring the inherent defects of "sacrificial technology".However,in order to ensure the performance,it should not be ignored that process defects affect static and dynamic characteristics and nonlinearity.To resolve the problems in micro-bridges,this paper takes vacuum encapsulated ideal micro-bridges,micro-arches and micro buffered structure as objects.Some theory analysis has been done,for validate the feasibility of the "bilateral pressurized bridges".We get the governing equation of electrostatically actuated micro-bridges coupling system which is pressurizing on both sides from the transverse free vibration equation of clamped-clamped beams,considering inertia and damping term,electrostatic geometrical nonlinearity.Initial defects caused by process and buffered structure,designed for reducing the influence,is expressed as the initial shape.Analysis of the relationship between natural frequency and dc voltage,resonance frequency or amplitude-frequency response and control parameters of initial shapes of different micro-bridge has been done.Then,lean out four typical kinds of bridge structures,do some amplitude-frequency response analysis,concluded bridge structures performance "soft nonlinearity",resonance frequency drift to a smaller scale;bilateral fold structure weaken more "soft nonlinearity" than single fold structure.Then,take ideal bridge,arches,bilateral buffered structure as objects,analyze the influence on dynamic characteristics of highness of arch,clearance of plates,geometric sizes of bridges and offset voltage,concluded that: For micro-arches,its resonant frequency reduces,resonance amplitude increases,softening effect reinforces when the highness of arches increases or the clearance of plates decreases;for different geometric sizes micro-beams,resonance frequency of longer is smaller,resonance amplitude and nonlinear behavior changes not obviously,resonance amplitude of wider is bigger,resonance frequency and nonlinear behavior changes not obviously,resonant frequency of thinner is smaller,resonance amplitude of thinner one is bigger,"soften nonlinearity" of thinner is more obvious;when dc voltage increases,resonance frequency reduces,resonance amplitude increases,"soften nonlinear" is more obvious,when amplitude of ac voltage increases,resonance frequency and nonlinear behavior changes not obviously.