二维运动平台气浮静压导轨承载性能计算与研究

为了进一步探索和研究气浮静压润滑支承机理及气浮静压导轨承载性能,提出并研制了一种具有气浮静压润滑支承的精密二维运动平台。结合气浮静压导轨的物理模型建立了其笛卡儿坐标系下的控制方程,采用有限差分方法和流量平衡原理对其控制方程进行了离散差分推导,运用超松弛迭代以及二分快速寻找收敛区间法对其承载性能进行数值计算并开展了实验研究。结果表明：气浮静压导轨承载性能受节流器类型的影响比较显著,多节流孔节流器的承载性能明显优于单节流孔节流器;供气压力对气浮静压导轨承载性能影响显著,供气压力越高其承载性能越强;同等条件下气浮静压导轨组合形式承载性能均优于单独形式承载性能;气浮静压导轨的承载性能实验测试结果和数值计算结果具有较好的一致性,验证了数值计算的有效性。相关研究对推动和促进气浮静压轴承和导轨在精密运动机构和测量设备的研究和工程应用具有较好的借鉴和指导意义。     

整体闭式与开式气浮导轨静态性能对比分析

静压气浮导轨是精密气浮工作台的重要组成部件,其承载能力和刚度直接影响了工作台的平稳性以及所加工零件的精度.针对所设计的精密高刚度二维气浮工作台,提出采用有限差分的数值计算方法,在双边间隙总和与供气压力相同的条件下,对整体闭式及开式气浮导轨的气浮面进行整体求解计算,对比分析其压力分布、承载能力、刚度等静态性能参数.结果 ...     

狭缝节流静压干气密封稳态性能数值模拟

为进一步优化提升静压干气密封的气膜开启能力,将狭缝节流器与静压干气密封相结合,设计狭缝节流静压干气密封,采用Fluent软件探究狭缝节流器结构参数和布列方式对干气密封性能的影响。结果表明：与经典小孔节流静压干气密封相比,相同节流面积下狭缝节流静压干气密封具有更高的气膜开启力;狭缝、均压槽周径比对静压干气密封气膜开启力的影响相互独立,存在最佳的周径比使得气膜开启力最大;在径向宽度一定的前提下,均压槽的平面空间越充裕,密封间隙内的气膜高压区范围越广、压力均布效果越好;狭缝沿径向、周向的列数增加均能提升气膜开启力;与周向连续狭缝布列相比,非连续性狭缝布列会导致更高的开启力。     

Diagnosis of gas fluctuations of aerostatic guideway

In order to diagnosis the gas fluctuations of aerostatic guideways, the calculation equation of stiffness of aerostatic guideway with double row orifice has been derived by gas lubrication theory. For the stiffness coupling structure of guideway and unloading guideway, the frequency of whole slides in machining direction with gas thickness has been derived by dynamic model. Wavelet transform as a means to process the measured signal of workpeice surface, the frequency characteristics of gas fluctuation of aerostatic guideways has been extracted out from measured signal, the errors of guideway system have been diagnosed according to power spectral density (PSD), this provide a basis for the diagnosis of machine tool error.     

Estimation method for errors of an aerostatic planar XY stage based on measured profiles errors

This paper describes a method for estimating the geometric errors of an aerostatic planar XY stage. The method calculates two-dimensional (2D) position errors and flatness based on measured guideway profiles. Profile measurements, estimates of motion error, and geometric error models are considered to estimate the 2D position and flatness errors along the X- and Y-axes. A three-probe system is used to measure the guideway profiles for the X- and Y-axes. The motion errors, which are used as input data for geometric error models, are calculated from the force equilibrium of aerostatic bearings along the measured guideway profiles and compared with laser interferometer measurements. Geometric error models were derived to calculate the 2D position and flatness errors of the stage. The measured results and estimates for the 2D position error and flatness differed by 0.5 and 0.6 μm, respectively. Therefore, the proposed estimation method for 2D position and flatness errors of an aerostatic planar XY stage will be a useful tool during the machining and assembly of guideways.     

开式静压导轨在球面车床上的典型应用

阐述了静压导轨在球面车床刀架床鞍上应用的必要性。通过对静压导轨的设计,静压导轨的工作原理和特点,油膜形式及尺寸的设计,油腔的初始托举力计算等方面的研究,证明在球面车床回转工作台低速、重负载的条件下,采用静压技术,把摩擦副的两个接触面隔开,使摩擦副的静摩擦为纯液体摩擦,从而保证了机床的回转精度和加工精度,有效的延长了工作台上摩擦副的使用寿命。     

基于ANSYS的空气静压轴承有限元分析

采用ANSYS对空气静压轴承的气膜压力分布进行研究,同时推算出轴承的承载能力和静刚度,为空气轴承式板形仪的结构设计和性能分析提供一定的理论依据。     

应用Marc分析气体静压轴承静态性能

依据气体润滑理论,建立了环面节流气体静压轴承数学模型。利用通用有限元软件Marc中的滑动轴承模块,结合气体静压润滑问题的有限元理论分析方法,对该模块进行二次开发,求得气体静压轴承的静态特性,并通过实验加以验证。     

空气静压轴承承载能力计算的数学模型及其解法

本文根据气体在喷管与缝隙中等温流动的假说,推导出空气静压轴承气膜压力的数学模型。应用计算机可以快速计算出气膜压力的大小,从而求出轴承的承载量。试验表明,这一数学模型是合理的。试验结果还表明,气流的周向流动对气膜压力的影响较大。最后对Powell和Shires的空气静压轴承承载能力的计算方法进行了讨论。     

力载荷下液体静压导轨的主动振动分析

以力载荷下的液体静压导轨为对象,建立了闭式导轨、开式导轨的主动振动模型,推导了系统的油膜刚度、阻尼系数的计算公式,计算了简谐、非简谐周期载荷下导轨系统的固有频率、幅值及相角,从理论上分析了设计参数对导轨系统的固有频率、幅值的影响。以闭式液体静压导轨为例,对导轨系统的固有频率、幅值放大系数进行了分析,结果表明：调整油腔压力、油膜厚度均可改变导轨系统的固有频率;力载荷作用下导轨的幅值放大系数基本上不受油腔压力的影响,而随油膜厚度的增大、油液温度的升高、载荷频率的降低而增大。详细地分析了力载荷下液体静压导轨的主动振动,为工程实际中减少导轨振动、提高加工精度提供了参考依据。     

Static tilt characteristics of aerostatic rectangular double-pad thrust bearings with double row admissions

Aerostatic thrust bearings have been used in linear guideway systems of various precision measuring apparatus by reasons of low friction, non-hysteresis and high accuracy of motion. In such a case that the measuring systems do not satisfy the Abbé principle, the accuracy of linear guideway systems is greatly influenced by the tilt characteristics in pitch, roll and yaw directions of aerostatic thrust bearings. This paper proposes the application of aerostatic rectangular double-pad thrust bearings with double row admissions of compound restrictors to the linear guideway systems subjected to tilt moments in both pitch and roll directions, and investigates, theoretically and experimentally, the static tilt characteristics of these aerostatic thrust bearings.     

Dynamic tilt characteristics of aerostatic rectangular double-pad thrust bearings with compound restrictors

Aerostatic rectangular double-pad thrust bearings with compound restrictors have often been used in linear guideway systems of ultra-precision machine tools and precision measuring equipments, because high bearing stiffness is easily achieved in these bearings. However, in actual devices, various dynamic loads as well as static loads are imposed on these aerostatic bearings. Therefore, in this paper, the dynamic stiffness and damping coefficient of this type of bearing for tilt motion of a shaft are investigated, both theoretically and experimentally. It was consequently found that the dynamic tilt characteristics of the aerostatic thrust bearings considered in this paper are greatly influenced not only by design parameters such as the groove position and the groove depth but also by the squeeze effect.     

局部多孔质气体静压圆盘止推轴承压力分布的有限元计算

直接在Cartesian Coordinates中对气体静压圆盘止推轴承的Reynolds气体润滑方程进行有限元计算,针对局部多孔质直径大小的不同,采用两种不同的网格划分方法,并通过Matlab编程实现了网格的自动细分,在此基础上,通过利用Galerkin加权残差原理对气膜内压力分布进行了求解.分析表明,网格的自动细分减少了网格划分的时间,便于获得合适的网格数量,使轴承压力分布的计算得到进一步简化.     

基于Workbench的高压圆盘气体轴承三维流场分析

为了取得高压圆盘气体轴承的完整三维流场,基于Workbench仿真软件对高压圆盘气体轴承进行三维建模仿真,得到整个流道及圆盘缝隙射流区的流场参数分布;将三维模型的气膜对称面与轴承圆盘、稳流管的轴对称面相交,截得气膜对称线;分析气膜对称线上的流场参数分布,并将其与二维简化模型流场计算结果进行对比,同时验证2种建模分析方法的有效性。结果表明：2种建模分析方法得到的气膜内马赫数和静压分布的变化规律一致,即在绝大部分气膜区域能保持高压,仅在气膜出口处很窄的范围内压力快速下降,同时在气膜出口附近形成超音速圆盘缝隙射流,使上游气膜内高压不受下游环境低压的影响;不同湍流强度对高压圆盘气体轴承内流场的静压无明显影响,但对缝隙射流区及气流远场区域的马赫数有着小幅影响。     

Design of the aerostatic linear guideway with a passive disk-spring compensator for PCB drilling machine

Problems with the conventional linear aerostatic guideway for a PCB drilling machine include deviation from straightness or parallelism tolerance between the granite guideways, and thermal expansion caused by the heat generated from ball screw and the driving system. These factors will result in vibration and affect the positioning accuracy during machine drilling.This paper describes the development of the resistance network method (RNM) for analyzing the static behaviors of aerostatic grooved thrust bearing designed with a disk-spring compensator to hold the table in a suitable position. Comparison is demonstrated between the RNM results and experimental data. Finally, a realizable application of these types of bearing to the linear guideway system for a PCB drilling machine is presented.     

滑流边界条件下MEMS微圆盘的气体压膜阻尼分析

在考虑滑流边界条件的基础上,分析了微缝隙间气体流动的特性,提出了一种粘度修正的分析方法。基于微缝隙气流的粘度修正模型,分析了气体对微圆盘的压膜阻尼效应,得到微圆盘表面的压强分布、压膜阻尼力和压膜阻尼系数的解析解。通过与有限元数值解进行对比,两者结果吻合非常好,误差小于0．0468%,证实了解析解的正确。指出MEMS微圆盘的气体压膜阻尼不但与结构尺寸有关,而且与固体壁面的材质、粗糙度和光洁度等有关。     

纳米级精度的竖直液体静压滑台设计

为了满足航天关键件的加工精度要求,需要设计并制造满足设计要求的纳米级精度的竖直液体静压滑台。本文针对滑台结构、关键部件及公差设计方法展开了研究。首先,根据高精度竖直滑台的设计要求,采用不等流量的滑块结构及控制方法整体设计滑台结构。设计时,将所有液压油管路均设置在滑块中,以减小油压损耗,且使得滑台结构紧凑。接着,为使圆孔加工时圆度误差不受导轨刚度的影响,采用等导轨刚度的设计方法,同时给出了该方法下油膜厚度、刚度、压力的计算方法。文中还证明了上下油腔不等承载面积法能够降低竖直滑台由于倾覆力矩产生的倾角误差,提高导轨运动精度。在此基础上,提出了基于不等流量结构的几何精度设计方法,计算并证明了不等流量的结构和控制方法可以降低导轨和滑块极高的制造等级要求和制造成本。最后,根据上述设计方法设计并制造了数控纳米曲面磨床竖直滑台,并测试了该磨床竖直Z滑台的运动精度。结果显示采用不等流量结构的滑台制造公差要求由IT1降低到IT3。Z滑台精度测试结果为:定位误差为±80nm,重复定位误差为48nm。     

空气静压轴系支承的数值分析

采用有限差分技术,对精密轴系中的径向和轴向空气静压轴承进行了数值分析。主要针对有多个供气孔的径向轴承的复杂流场,沿周向展开承载曲面以雷诺方程为气体润滑的控制方程。同时根据质量守恒原理,制定出每个供气孔出口压力边界条件逐轮修正的迭代路线,计算出不同偏心率和供气压力下的压力分布、承载能力及流量。该技术成功地用于轴系支承精确设计并制造出精密模块化主轴轴系。     

环形多孔节流空气静压轴承气膜流场分析

为提高空气静压轴承工作的稳定性,设计一种环形多孔节流空气静压轴承,建立其物理模型,并采用大涡模拟方法对轴承节流孔出口处附近计算区域的气膜流场进行分析。结果表明：空气静压轴承气膜压力在节流孔的出口附近气膜间隙上出现分离,但在远离节流孔的出口气膜压力曲线是重合的;节流孔数为9时轴承节流孔出口处的最大压降幅度为节流孔数为1时的26%左右,最大速度突升幅度为节流孔数为1时的43%左右,表明增加节流孔的孔数可以显著减小节流孔的出口附近压力的突降、速度的突升,提高轴承工作稳定性;在空气静压轴承工作过程中,节流孔出口处附近压力和速度的突变会产生微振动现象,而采用环形多孔节流可显著降低微振动现象。     

Static behavior and dynamic stability analysis of grooved rectangular aerostatic thrust bearings by modified resistance network method

This paper begins with the development of the resistance network method (RNM) for designing an aerostatic rectangular bearing with X-shaped grooves. The Newmark integration method and the modified RNM, which takes into account the equilibrium of the mass flow rate and the squeeze film effect, are used to analyze the time-dependent dynamic behaviors at each time step.Finally, the stability properties as well as impulse responses of this type of bearing, which simulates variation in film gap caused by imperfect guideway geometry, are demonstrated in the current paper.