抗磁悬浮静电电机悬浮与驱动特性研究

微型电机随着特征尺度的降低,其表面效应凸显,摩擦问题急剧突出。抗磁悬浮技术具有无摩擦、被动自稳定、尺度效应下浮重比显著提升等特点,是解决微型电机机械摩擦问题的一种有效途径。提出了一种基于抗磁悬浮静电驱动的微型电机方案,研制了转子直径为10 mm的定子下置式微型抗磁悬浮静电电机;基于永磁体电流等效模型,推导了抗磁悬浮静电电机磁通密度表达形式,建立了抗磁悬浮力的数学模型,获得了悬浮力与悬浮高度的关系并进行了实验验证;基于电容静电能原理,建立了抗磁悬浮静电电机的驱动力矩数学模型,获得了静电驱动力与定子输入电压、悬浮高度的关系并进行了实验验证;开展了旋转实验研究,分析了输入电压、环境湿度对转速的影响规律,获得了抗磁悬浮静电电机的驱动特性。本研究将会为高性能微型抗磁悬浮静电电机的研究提供支撑。     

磁悬浮与光电反馈式静电悬浮

对磁悬浮技术作简要综述,着重介绍超导磁悬浮技术的基本原理及发展现状。提出一种新的悬浮技术——静电悬浮技术,讨论静电悬浮的原理及其光电反馈控制系统,展望静电悬浮技术的应用前景。     

磁悬浮硬盘的径向磁力轴承优化设计

提出了基于电磁场有限元分析的磁悬浮硬盘径向磁力轴承优化设计方法,建立其有限元分析模型,以最大磁力为目标函数对磁悬浮硬盘的径向磁力轴承进行了优化设计,并对优化结果进行了分析。     

用磁悬浮轴承解决光驱、硬盘高速化发展所面临的难题

本文主要探讨用磁悬浮轴承取代一般车载视听系统上光驱、硬盘之主轴轴承,来克服光驱、硬盘朝高速化发展所面临的难题。基于实用性考虑,针对最少能量损失和较低之成本去分析,设计了低成本的三极磁悬浮系统,使其可与现有系统竞争。     

基于耦合激磁的硬盘驱动器磁力轴承的设计

提出磁悬浮硬盘的概念，介绍了基于耦合激磁的5自由度主动磁力轴承的基本原理，并推导了磁力的计算公式及其主要结构参数设计公式。     

磁悬浮硬盘转子机电耦合动力学分析

为研究磁悬浮硬盘转子的动力学特性,建立了一种基于状态空间的统一的动力学模型,同时将磁力轴承为弹簧阻尼支承系统建立简化的转子动力学模型,通过两种模型的计算结果分析,机、电、磁、控制相互耦合的作用,对磁悬浮硬盘转子系统的特征值有较大的影响。     

磁悬浮转子陀螺的研究进展

悬浮转子陀螺具有精度高的潜在优点,并可同时测量二轴角速度和三轴加速度.它可分为静电悬浮转子与磁悬浮转子陀螺两种类型.本文就国内外研究的磁悬浮转子陀螺的各种结构及其工作原理、工艺和性能特点进行了阐述,特别是对磁悬浮转子微陀螺发展的最新进展作了较详细的介绍.     

磁悬浮支承技术在机床中的应用

阐述了国际国内磁悬浮支承技术的发展历史、研究现状及发展趋势，重点介绍了在机床中应用的磁悬浮轴承结构、类型及应用领域。将磁悬浮支承技术用于电主轴中，电主轴可以在5000～8000r／min的转速下运行上万小时：将磁悬浮支承技术用于机床直线电机的进给平台中，与传统的机床导轨支承相比，磁悬浮支承具有无机械摩擦、无磨损、无爬行、无润滑、可靠性提高、寿命延长等诸多特点。     

基于PID算法的低功耗微型磁悬浮控制系统设计

针对当前市面上微型磁悬浮装置调节不够快速灵敏，导致调节功耗大的问题，提出一种基于PID算法的低功耗微型磁悬浮控制系统。首先，详细介绍了微型磁悬浮控制系统的方案设计，包括磁悬浮系统结构、磁悬浮控制方案以及悬浮体失衡控制原理；然后，从关键电路设计和程序设计方面介绍了基于PID算法的磁悬浮控制系统实现；最后，对所设计的磁悬浮控制系统进行了测试，并与市面上购买的磁悬浮装置进行了功耗测试对比。测试结果表明，所设计控制系统实现了磁悬浮的低功耗调节。     

电磁悬浮静电驱动旋转微镜控制系统设计

为了实现对电磁悬浮微镜绕轴向-180°到+180°角度的旋转控制.对该系统所采用的电磁悬浮、静电驱动、转角闭环控制等进行研究。首先,设计和制造了电磁悬浮微镜的定子和转子结构。接着,对通过线圈的电流频率、电流大小与悬浮高度的关系进行仿真和实验,实验结果和仿真结果基本一致。然后,在分析变电容驱动原理的基础上,进行旋转控制实验,说明在按相序通电情况下,转子能实现旋转。最后,介绍了采用高精度的电容检测的转角闭环控制系统。实验结果表明:在激励电流峰-峰值是0.5A,激励频率为20MHz时,转子悬浮到100μm高度,能够实现指定角度的控制,基本满足电磁悬浮微镜的控制要求。     

Vibration Response Characteristics against the Radial and Axial Shocks on Small Size Hard Disk Drive Spindle Supported by Oil Film Bearings

This paper describes the experimental study on shock response of FDB （fluid dynamic bearing） spindle for HDDs （hard disk drives）. The FDBs are widely used as rotating shaft support elements for HDD spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipment such as mobile PCs （personal computers）, video cameras, car navigation systems and so on. Hence, the rotating shaft has a possibility to come in contact with the bearing by external shocks and it causes wear or seizure to the bearing surface. To avoid the problem, it is extremely important to know how the spindle moves against the large shock on HDDs experimentally. However, as far as the authors know, there are few experimental studies treating the shock response of HDD spindles. In this paper, firstly, we propose a new test rig and experimental method for shock response of FDB spindles. Then the shock tests against the radial and axial disturbance on FDB spindle for 2.5＂ HDD are conducted. Finally, the experimental results of shock response waveforms and maximum displacement of disk are shown.     

Identification Method of Dynamic Coefficients of Fluid Film Bearings for HDD Spindle Motors

Fluid film bearings are widely used as support elements of rotating shaft for HDD （hard disk drive） spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipments such as mobile PCs, car navigation systems. Hence, the rotating shaft has a possibility to come in contact with the bearing and it causes wear or seizure to the bearing surface. In order to avoid the problems, it is extremely important to enhance the dynamic characteristics of the fluid film bearings for spindles. However, verification from both theory and experiment of dynamic characteristics such as spring coefficients and damping coefficients is rare and few. In this paper, the bearing vibration characteristics when the HDD spindle is oscillated are investigated theoretically and experimentally. And then the identification method ofoil film coefficients of fluid film bearing spindles is described.     

Study of Flow Characteristics of Lubricant in Spiral-Groove Bearings by the Fluorescent Method

Abstract

The hard disk drive spindle is one of the critical mechanical components in hard disk drives (HDDs). It has great influence on overall performance, including track density, data-transfer rate, energy consumption, noise, and so forth. Nowadays, HDDs with higher density and speed, larger capacity, and smaller size are under active development. This requires that HDD spindles have fast rotating speed, excellent accuracy, and small size. However, ball-bearing spindles, which are widely used in current HDDs, cannot meet these requirements. HDD spindles supported by oil-lubricated spiral-groove bearings are considered to be a candidate to replace ball-bearing spindles. There is no oil-supply device in the bearing, and the flow characteristics of the lubricant in the bearing have a great effect on the performance of the spindle.

In this article, the fluorescent method is used to study the flow characteristics of the lubricant in a spiral-groove bearing. The establishment and recovery of the lubricant film during start/stop of the spindle are observed. The effects of working conditions on the thickness and distribution of the lubricant film are investigated. The influence of oil supply on the performance of the bearing is also studied.     

Effect of Disk Flexibility on Rocking Mode Frequencies of a Disk Drive Spindle Motor System

The lowest natural frequency of a hard disk drive related to a spindle motor is the so-called “rocking mode,” the frequency at which the rotor of the motor is whirling conically. A traditional rotordynamics theory with thick/rigid disks is not able to predict the rocking mode frequencies correctly. In this paper, the rocking mode frequencies of a single-disk rigid-rotor motor were solved analytically, including the effects of disk flexibility and ball bearing contact angle. In addition, the disk flexibility model was integrated to a finite element-based (FEM) flexible-shaft rotordynamics computer program. The closed-form solution of the analytical model provides design engineers a tool to identify critical design parameters. It was found that the rocking mode frequency, which is mainly affected by the clamped condition at the inner radius of the disk, is the flexible disk one-nodal-diameter mode frequency reduced by the compliance of ball bearings. The results obtained from both the analytical model and the FEM computer program matched the experimental results with an error less than two percent. Neglecting the effect of ball bearing contact angle increases the error three times. The effects of design parameters were also investigated.     

Modeling and Analysis of a Micromotor with an Electrostatically Levitated Rotor

The modeling and evaluation of a prototype rotary micromotor where the annular rotor is supported electrostatically in five degrees of freedom is presented in order to study the behavior of this levitated micromotor and further optimize the device geometry. The analytical torque model is obtained based on the principle of a planar variable-capacitance electrostatic motor while the viscous damping caused by air film between the stator and rotor is derived using laminar Couette flow model.Simulation results of the closed-loop drive motor, based on the developed dynamic model after eliminating mechanical friction torque via electrostatic suspension, are presented. The effects of the high-voltage drive, required for rotation of the rotor, on overload capacity and suspension stiffness of the electrostatic bearing system are also analytically evaluated in an effort to determine allowable drive voltage and attainable rotor speed in operation. The analytical results show that maximum speed of the micromotor is limited mainly by viscous drag torque and stiffness of the bearing system. Therefore, it is expected to operate the device in vacuum so as to increase the rotor speed significantly, especially for those electrostatically levitated micromotors to be used as an angular rate micro-gyroscope.     

Effect of relative humidity and disk acceleration on tribocharge build-up at a slider–disk interface

High performance disk drives require high spindle speed. The spindle speed of typical hard disk drives has increased in recent years from 5400 to 15000 rpm and even higher speeds are anticipated in the near future. The increasing disk velocity leads to increasing disk acceleration and slider–disk interaction. As the head-to-disk spacing continues to decrease to facilitate increasing recording densities in disk drives, the slider–disk interaction has become much more severe due to the direct contact of head and disk surfaces in both start/stop and flying cases. The slider–disk interaction in contact-start-stop (CSS) mode is an important source of particle generation and tribocharge. Charge build-up in the slider–disk interface can cause electrostatic discharge (ESD) damage and lubricant decomposition. In turn, ESD can cause severe melting damage to MR or GMR heads. We measured the tribocurrent/voltage build-up generated at increasing disk acceleration. In addition, we examined the effects of relative humidity on the tribocharge build-up. We found that the tribocurrent/voltage was generated during pico-slider/disk interaction and that its level was below 250 pA and 0.5 V, respectively. Tribocurrent/voltage build-up was reduced with increasing disk acceleration. Higher humidity conditions (75–80%) yielded lower levels of tribovoltage/current. Therefore, a higher tribocharge is expected at a lower disk acceleration and lower relative humidity condition.     

A mechanical light chopper based on a hard disk drive for systems of laser sounding of the atmosphere

An easily manufactured high-speed mechanical chopper based on a Maxtor D740X-6L hard disk drive with a rotation speed of 7200 rpm is described. It is shown experimentally and theoretically that the switching time of a light beam with a diameter of 0.8 mm is ∼20 μs. The described chopper can be used in systems of laser sounding of the atmosphere for protection of photodetectors against a high-power backscattered signal from a near zone of the sounding line, as well as in other problems where fast mechanical switching of a light beam is required.     

Optimal disk clamp design to minimize stress variation of disks in a hard disk drive

To avoid disk waviness and warpage in a hard disk drive, it is desirable for the stress distribution on disks fastened to a spindle motor by a clamp to be uniform in the circumferential direction while sufficient clamping force is maintained. The objective of this work is to find a clamp configuration that minimizes the circumferential stress variation on the disks while maximizing the clamping force. Topology and shape optimization methods were employed to find the optimal clamp configuration. To facilitate the optimization problem, a model for the surface contact between the clamp and the top disk was simplified to a static model where the disk clamp and spring were connected. By incorporating the surface recess, the optimized clamp has equal stiffness in the circumferential direction, except for the four tooling hole areas. Numerical simulation confirmed that the optimized clamp reduced the stress variation by about 78% without sacrificing the clamping force; in fact, it increased the clamping force.     

Effect of hard-disk drive spindle motor vibration on dynamic microwaviness and flying-height modulation

In order to achieve higher recording densities up to 1 Terabit per square inch using conventional magnetic recording technologies, the recording slider will need to be physically spaced very close to the rotating disk, possibly via the use of an air-bearing surface. However, as the recording slider is flying at such ultra-low spacing of few nanometers over a high-speed rotating disk, it is experiencing disturbances from various different sources and of a wide frequency range. These disturbances may cause the recording slider to vibrate significantly, a condition known as flying-height modulation (FHM), which may result in data loss and possibly head–disk interface failure. A significant source of slider excitation is due to low frequency surface topographical features of the rotating disk, termed dynamic microwaviness. Dynamic microwaviness is a dynamic property of the disk and differs from regular topographical microwaviness, which is a static property. Most research works on dynamic microwaviness and FHM have been focused at the component level, using somewhat idealized conditions, such as high performance air-spindle motors that exhibit very low vibration amplitudes. In this paper, actual hard-disk drive spindle motors are used to investigate the effect of spindle motor vibration on dynamic microwaviness and FHM. It is found that there is a clear connection between spindle motor vibration and dynamic microwaviness that affects FHM.     

精密装配的基准信息链模型和3D偏差计算

研究了精密零件装配的基准信息链模型与基于该模型的3D偏差累积计算方法。以微硬盘装配为实例,分析了装配过程中的多约束关系,采用基准信息链模型建立了装配空间结构和尺寸偏差关系的数字化表达,给出了齐次变换矩阵和误差矩阵关系式,实现了关键特征的3D偏差累积计算。实例表明,该计算方法可有效应用于数字产品开发的设计决策过程。