高密磁记录系统磁头IBM3370 的动力学响应分析(英文)

硬盘系统一般采用气体润滑，以提高使用寿命和读写可靠性．本文讨论了多聚脂流体润滑的ＩＢＭ３３７０ 磁头／ 磁盘系统，以期提高磁记录密度．润滑模型中考虑了超薄流体润滑的剪薄效应，并用有限差分法对润滑方程进行求解．应用摄动理论建立了ＩＢＭ３３７０ 磁头／ 磁盘系统的动力学模型，分别对气体润滑和液体润滑的两自由度磁头的动力响应进行了仿真．仿真结果表明，在相同磁头倾角条件下，液膜润滑的磁头／ 磁盘的动力稳定性优于气体润滑的磁头／ 磁盘系统     

悬浮滑块跟随性研究

给出了悬浮滑块动态性能分析近似模型，在此基础上得到了滑块的运动微分方程．并以此为依据研究了悬浮滑块的跟随性．     

Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers

In this paper, a dynamic model is established for a two-stage rotor system connected by a gear coupling and supported on ball bearings with squeeze film dampers (SFDs). The nonlinear dynamic behavior of the rotor system is studied under misalignment fault condition. The meshing force of the gear coupling is calculated considering the deformation of the tooth caused by torque transmission and dynamic vibration. The contact force between the ball and race is computed based on the Hertzian elastic contact deformation theory and the elastohydrodynamic lubrication theory. The supported force of SFD is simulated by integrating the pressure distribution derived from Reynolds’s equation. The equations of motion are rewritten in non-dimensional differential form, and the fourth-order Runge-Kutta method is employed to solve the nonlinear dynamic equilibrium equations iteratively. To verify the validity of the dynamic model and the correctness of the numerical solution method, the experimental power spectra of the rotor system under various misalignment degrees are compared with the analytical results. The effects of several important parameters, such as the lubrication of the ball bearing, the centralizing spring stiffness, the radial clearance of SFD, and the misalignment of gear coupling, on the dynamic characteristics of the rotor system are investigated and discussed mainly focusing on the system stability. The response spectra, bifurcation diagrams, and Pointcaré maps are analyzed accordingly. These parametric analyses are very helpful in the development of a high-speed rotor system and provide a theoretical reference for the vibration control and optimal design of rotating machinery.     

磁流变液阻尼器设计与性能测试

自动化生产中,自动检测设备的使用越来越广泛,为保证检测精度,这类设备都需要控制气动和电动振动对检测的干扰和影响．为此本文设计了MRF可控阻尼器及可调振动滑台装置,总结基于MRF力学模型和磁路设计模型,设计MRF阻尼器的经验;基于NI数字化测试系统检测MRF阻尼器控制移动滑台振动的效果．实验结果证实MRF阻尼器能快捷方便地调节阻尼、高精度控制移动滑台的振动,MRF阻尼器振动控制装置具有教学实用价值．     

Research on a Rigid Rotor—Sliding Bearing System with a Squeeze Film Damper

In this paper,a dynamic model on a rigid rotor-sliding bearing system with a SFD is established.The stability and bifurcation behaviors of the system are studied,on The basis of the differential equations of fluid momentum and mass continuity,the distribution pressure function is derived by taking oil film inertia force into consideration.Damping force, clearance excitation force,interference force of different frequencies and static load are also considered in the model,Finally,the governing equations of the stability and bifurcation behaviors of the system are solved by Floquet theory,Simulation of dynamic model shows that the rigid rotor-sliding bearing system can maintain stability and exhibit a Hopt bifurcation phenomenon in a certain range.     

木材干燥过程中一个非线性模型的二阶收敛差分格式

针对描述木材干燥过程中的一个非线性微分方程模型,用降阶法对其建立了一个差分格式.此模型是由一个非线性常微分方程和一个非线性抛物方程组成的耦合微分方程组.首先引进一个新变量把原问题转化为一阶微分方程组问题,然后对此一阶微分方程组建立了一个线性化差分格式,应用能量方法证明了差分格式的可解性、稳定性和收敛性,并给出了误差估计式.差分格式关于时间步长和空间步长均为二阶.在实际计算时,将引入的新变量分离开,得到仅含原变量的差分格式,降低了计算量.数值计算结果验证了理论结果的可靠性.     

Active control of structural vibration by piezoelectric stack actuators

INTRODUCTION Passive methods have played an important role for a long time (Snowdon, 1973; Nelson, 1982; Pan et al., 1992) in vibration and noise control. However, with inrush of some novel engineering structures and machines, such as super high-speed machine tools, long-span bridges, thin shell structures, micro elec- tromechanical systems and so on, traditional passive control approaches are not efficient enough for con- trolling structure noise and vibration from these novel systems an…     

垃圾填埋气体传输过程的渗流模型及解析解

基于多孔介质渗流力学理论建立了垃圾填埋气体传输过程的动力学模型,采用Laplace变换对气体传输渗流场控制方程进行近似解析求解,得到了填埋气体非线性渗流的压力分布规律.由不同时间填埋气体压力随水平距离分布计算结果看出:随时间的增长,压力曲线变缓,压力增大.     

一种高速列车-轨道三维空间耦合动力学模型

研究目的：基于车辆-轨道耦合动力学理论分析方法,建立一种高速列车-轨道三维耦合动力学模型,并明确列车-轨道耦合模型与单节车辆-轨道耦合模型在高速列车-车九道耦合动力学性能分析中的差异。创新要点：建立一种高速列车-轨道三维耦合动力学模型,模型中考虑列车的纵向动力学行为以及车间连接装置对列车中不同车辆动态响应的影响,并基本明确完善的列车-轨道耦合模型在高速列车-轨道耦合动力学性能分析中的重要性。重要结论：单节车辆-轨道耦合模型会过高地估计高速列车在运营过程中的振动响应和动力学性能指标,而完善的列车-轨道耦合动力学模型的计算结果则更加接近实际情况。     

嵌岩桩非线性动力学特性

The nonlinear dynamic characteristics of a pile embedded in a rock were investigated. Suppose that both the materials of the pile and the soil around the pile obey nonlinear elastic and linear viscoelastic constitutive relations. The nonlinear partial differential equation governing the dynamic characteristics of the pile was first derived. The Galerkin method was used to simplify the equation and to obtain a nonlinear ordinary differential equation. The methods in nonlinear dynamics were employed to solve the simplified dynamical system, and the time-path curves, phase-trajectory diagrams, power spectrum, Poincare sections and bifurcation and chaos diagrams of the motion of the pile were obtained. The effects of parameters on the dynamic characteristics of the system were also considered in detail.     

基于自适应预测算法的APF无差拍控制方法

有源电力滤波器（active power filter, APF）补偿电流跟踪控制要求具有较高的稳态精度和较快的动态响应速度。文章将自适应预测滤波算法应用于无差拍控制,实现APF补偿电流精确控制。根据APF时域数学模型,推导滤波系统的无差拍控制离散方程;通过自适应(finite impulse response filter, FIR)预测滤波算法实现基波电流预测,消除控制系统的计算延迟,给无差拍控制提供所需的指令电流预测值。对预测算法进行MATLAB仿真,验证预测算法的稳态精度和动态跟踪快速性;实验室样机验证控制实验结果证明所提出的控制策略有效的,具有一定的实用性。     

用气轨系统与Spss测定重力加速度

使气轨处于水平方向的动态平衡状态下,通过设定系统质量,调整系统在竖直方向上所受的外力,用物理天平称量滑块质量,用智能计时系统测出滑块在水平方向的加速度。由实验原理、不确定度分析,用Spss的线性估计功能分析实验数据,得到系统质量一加速度综合量与竖直方向砝码质量的定标曲线,并验证得系统质量一加速度综合量与竖直方向的砝码质量存在线性关系,由此标定出重力加速度,并用置信概率为95％的不确定度对实验数据及其结果进行分析和评价,得到较为合理的实验结果。     

基于Hamilton原理的双跨转子系统建模和转子动态特性分析

研究目的：研究双盘双跨转子/轴承/汽封系统在非线性油膜力和非线性汽封力共同作用下的动力学特性,分析了转子转速、密封力、油膜力和联轴器刚度等因素对转子稳定性的影响。创新要点：采用Hamilton原理和有限元方法建立双盘双跨转子/轴承/汽封系统模型,使得双跨多节点的转子系统数值求解更加容易。研究分析转子转速、非线性密封力、非线性油膜力和联轴器刚度等因素对转子稳定性的影响,为大型转子系统的设计提供理论基础。研究方法：采用Hamilton原理和有限元方法建立双盘双跨转子/轴承/汽封系统模型（图1和2）。应用四阶Runge-Kutta法进行数值求解,并采用轴承处、圆盘处的分岔图、时程图、庞加莱映射图、频率图和相轨迹图等来分析转子系统的动态特性。重要结论：1.通过数值计算分析,转子的转速、非线性汽封力、非线性油膜力和联轴器的刚度对双跨转子的稳定性有重要的影响作用。2.随着转速的上升,双跨转子系统从最初的稳定运动,到三倍周期运动,到准周期运动和多倍周期运动交替出现,运动特性相比单跨转子系统要更为复杂。     

非线性双圆盘转子-密封系统的数值分析

研究目的：求斛双圆盘转了-密封系统的非线性振动特性和运动响应 创新要点：采用有限元法（FEM）和拉格朗目方程求解双圆盘转子-密封系统,进而为研究多级转了系统的非线性振动问题提供有效方法。研究方法：基于有限元法（FEM）和拉格朗目方程。同时利用四阶龙格-库塔法求解系统动特性运动响应情况,利用风岔图、时间历程图、轴心轨迹图、庞加莱映射和幅值谱等分析图研究双圆盘转子-密封系统的非线性振动特性。重要结论：随着转速的增大,双圆盘转子-密封系统呈现丰富的非线性运动形式,包括周期性运动、多周期运动,准周期运动以及混沌运动。在右端圆盘不平衡质量小于34kg、密封间隙范围为0.376mm-0.54mm、密封长度大于0.13m或者密封压差高于0.104MPa的情况下均有利于提高双圆盘转子-密封系统的稳定性。     

基于LabVIEW的动态称重系统的设计

为测量单托辊传送带在传输状态下固体散料的动态重量,采用称重传感器连续采样计量区段传输带托辊所受到的压力,用电涡流传感器测量放大后的辊轴瞬时速度,将采集的两路电压信号调理后,用测速法计算物料的瞬时重量和累积重量。动态称重系统采用虚拟仪器技术完成信号的采集和调理,上位机采用LabVIEW软件实现计算和显示,原理简单,精度高,易实现,具有较高的实用性。     

动态系统Stiff微分方程的稳定性分析

动态系统 Stiff 微分方程常在科学、工程中出现。本文利用模型方程对动态系统差分微分方程的 Lagrange 和 Hermite 插值问题的稳定性分别进行分析,给出稳定分析的方法、条件和一些重要结果,计算出稳定域的边界轨迹等。     

PWM Buck变换器的输入输出精确线性化模型和仿真

应用PWM开关模型建立了适合于大信号分析的PWM Buck变换器连续模态下的非线性数学模型,推导出对应的非线性坐标变换和非线性反馈变换,将原非线性系统变换为一个线性系统。对通过精确线性化方法得到的系统非线性控制策略进行了仿真,具有较好的响应特性。     

含无辐射过程四能级GSA／ESA上转换发光的理论分析

不同于通常的三能级GSA／ESA上转换系统,给出了一个包含无辐射弛豫过程的四能级上转换系统,利用速率方程模型,从理论上分析了其上转换动力学过程和发光特性．结果表明,体系上转换的上升过程由所包含能级的无辐射弛豫速率决定,而衰减过程主要由终态能级的弛豫速率决定．     

Dynamics and Control of Grinding Machine with Micropositioning Workpiece Table

To improve the machining precision of a surface grinding machine, a micropositioning workpiece table with high performance was used as auxiliary infeed mechanism to implement nanometer level positioning and dynamic compensation. To better understand the characteristics of the grinding machine modulated with micropositioning workpiece table, the dynamic model of the grinding system was established with modal synthesis and Lagrange's equation methods. The grinding system was divided into five subsystems. For each subsystem, the generalized kinematic and potential energies were obtained. Accordingly the dynamic model of the grinding system was given in the modal domain. The waviness of the grinding process was achieved based on the wheel and workpiece vibration. A nonlinear proportional integral derivative (PID) controller with differential trackers was developed to realize dynamic control. The simulation results show that the machining accuracy of the workpiece can be effectively improved by utilizing the micropositioning workpiece table to implement dynamic compensation. An experimental test was carried out to verify the proposed method, and the waviness of the workpiece can be reduced from 0.46 μm to 0.10 μm.     

移动式工业机器人设计的动力学分析

移动式工业机器人的操作臂是一个复杂的动力学系统，它由6个连杆和6个关节组成。具有多个输入和输出，存在着错综复杂的耦合关系和严重的非线性。论文从构造操作臂的雅可比矩阵入手。从系统功能的观点出发。建立机器人动力学方程。分析动力学正反两个方面问题。