Theoretical Study Of Noncontact Handling And Transportation System Based On Near Field Acoustic Squeeze

Near-field acoustic levitation has an extensive application prospect in the manufacture of micro-electromechanical system parts.The key challenge to this technology is the limited load-carrying capacity,which sometimes cannot satisfy the requirements of various applications.This paper introduced a simple method,i.e.,adding grooves on the reflector surface,to improve load-carrying capacity.Meantime,owing to its distinct non-contact,oil-free and noise-free characteristics,a self-running sliding stage based on near-field acoustic levitation can be used in an environment,which demands clean rooms and zero noise.In this thesis,the main contents are as follows:(1)According to gas lubrication theory,the gas lubrication Reynolds equation of the NFAL in the polar coordinate is established by the dimensionless parameter transformation;establish a piecewise function expressions of gas film thickness in to solve gas film thickness of discontinuous problems in radius direction;the dimernsionless gas lubrication Reynolds equation transformed by the eight discrete method into a first order differential equation;therefore,the linearizing Reynolds equation which processed by Newton-Raphson method,combined with resonance frequency and modal vibration mode of the experimental device which obtained by experimental measurement and finite element software ANSYS,used MATLAB software for data calculation to acquire squeeze film pressure distribution,and then derive the levitation force of pressure expression.(2)The relationships between levitation height and excitation amplitude under different groove types are measured by constructing the experimental test rig of NFAL,and are compared with theoretical calculation results.At the same time,in order to explore the influence of groove types for the squeeze film fluid lubrication,the pressure distribution of different groove types in the same conditions is studied;finally,a detailed parametric analysis on the circumferential groove number,groove depth and groove width provides theoretical reference for the optimization of groove parameters.(3)A self-running sliding stage analysis model is established by using finite element software,the sliding stage of resonant frequency and resonant vibration mode is obtained through the modal analysis;at the same time,this paper uses the finite element method to acquire the traveling wave distribution of the sliding stage by reasonably simplified the stage into beam,and then combined with the sliding stage movement model to obtain the mathematic expression of the gas film thickness under the condition of the standing wave and travelling wave.(4)According to gas lubrication theory,the nonlinear Reynolds equation derived from the Navier-Stokes equation(N-S equation),then combined with the boundary conditions of the simplified model to acquire the squeeze film pressure distribution through finite difference method(FDM)and Newton-Raphson method,thus,the expression of levitation force and thrusting force can be obtained;then,the levitation and movement characteristic of the self-running sliding stage are analyzed.Finally,parametric analyses of the effects of amplitude,frequency,and standing wave ratio on the sliding stage dynamic performance are investigated,which provide theoretical reference for the optimization of parameters.