磁头润滑面形状对气动力特性的影响

本文采用微分离散差分方法求解滑流条件下的修正Reynolds方程．对于一阶导数间断的物理量——气膜厚度采用高精度保凸性磨光法进行处理．给出了气膜压强分布立体图以及几种因加工误差造成磁头滑块润滑面变形的误差型面的飞升曲线、中心线上压强分布、压力中心和负载随加工误差大小的变化情况，指出了磁头滑块润滑面加工时宁凸勿凹的倾向性意见．     

线性定常系统电网络阻尼动态特性仿真研究

该文用李亚普诺夫定理推导出的综合阻尼系数方法研究分析了四阶线性系统电网络阻尼特性,对其电路的动态特性进行了计算机仿真。仿真结果证明,采用综合阻尼系数方法研究分析线性定常系统的阻尼特性的方法是合删、可行的,综合阻尼系数反映的是整个线性系统的综合阻尼效应,具有完善的物理意义,可以在整个系统的最佳阻尼下选择不同的参数。特别对系统特征方程次数较高时原则上可不受方程阶数限制,可以准确分析说明线性系统参数变化对阻尼的影响和对阻尼的大范围判定。文中的方法和结论对高阶线性系统的分析是可行的,可用以研究大系统动态过程振荡稳定性问题。     

基于多重网格控制体方法的皮米磁头气膜压强求解

磁头磁盘系统的发展越来越快,在磁头的开发设计阶段,就需要对磁头的飞行姿态作出快速、准确的数值预测.本文提出一种计算效率高的、基于叠加修正策略的多重网格控制体方法,解决轴承数很大和导轨形状复杂的气膜承载问题.运用这种方法求解Pico磁头(30%,1.25 mm×1.0 mm,飞高7 nm)的气膜承载压强,相比较单网格方法,多重网格方法求解性能提高显著.     

一种TPC磁头静态和动态特性的研究

本文根据ＴＰＣ磁头滔动原理，设计了一种适用于小型硬盘摇臂式寻道机构的等飞高磁头，并研究了其静态和动态浮动特性，表明，在盘面的整个寻道过程中，头盘间隙变动量不到３ｎｍ，磁头侧倾角也很小，磁头的动态特性较为理想，气膜共振频率在３０ｋＨｚ左右。     

结构参数对超磁致伸缩致动器动态特性的影响

本文从Terfenol—D棒的线性压磁方程出发,建立了超磁致伸缩致动器（GMA）轴向方向的传递函数动态仿真模型,研究了其主要结构参数,即Terfenol—D棒半径r和长度l、碟簧刚度kF、负载质量MF在对GMA阻尼系数ξ、固有频率f和动态性能指标上升时间tr、调节时间ts、超调量δ的影响。给出了具有优良动态性能的GMA应满足的两个条件,即阻尼系数ξ为0．707和系统固有频率f等于GMA交流驱动频率。最后,根据这两个条件对设计出的GMA进行了结构参数优化,当r=20mm,l=60mm,MF=0．57kg,kF=2000N／mm时,ξ=0．706,f=5680．7HZ,动态性能指标上升时间tr=0．943×10^-5s、调节时间ts=1．29×10^-4s,超调量δ=4％,明显改善了GMA的动态性能和稳态性能。     

磁头浮动块在浮动过程中的磨损

温式磁盘驱动器中的三轨式铁氧体磁头浮动块是以接触启停方式浮动的。本文分析了该磁头浮动块在其整个浮动过程——边界润滑浮动、混合润滑浮动和完全动压润滑浮动中的磨损情况,并且对嵌入磁盘内的浮动块磨损微粒进行了数量分析。结果表明,当磁盘速度大于20m/s时,完全动压浮动中的磁头浮动块的磨损大大减少并趋于零;正常设计的磁头浮动块在以接触启停浮动方式的整个浮动过程中磨损微小,对正常工作无影响。     

磁头浮动特性研究——动态分析

本文对流体润滑方程和浮动块动力学方程进行了耦合时域动态求解。结合实际磁盘机中的一种两轨式磁头浮动块,对浮动块的各项动态性能作了分析。仿真了磁头浮动块飞越各种盘片障碍物时的飞行姿态和浮动块对盘片波动的响应。通过对冲击响应进行FFT变换求取了空气支撑的频率结构。     

波纹辊轧机辊系主共振时滞反馈控制

金属复合板波纹辊轧制成形是一项变革技术,在复合板轧制成形的过程中,轧制界面的非线性阻尼以及上下波纹辊之间的非线性刚度都可能导致主共振的发生,造成辊缝的波动.考虑了波纹辊轧机波纹界面间的非线性阻尼和非线性刚度,建立了波纹辊轧机两自由度垂直非线性数学模型.利用奇异值理论和相平面法讨论了波纹辊轧机辊系自治下的稳定性,运用多尺度法求解了波纹辊轧机辊系在波纹界面激励下主共振的解析近似解和幅频特性方程.分析了非线性刚度系数、非线性阻尼系数、系统阻尼系数、轧制力的幅值等参数对主共振的影响.设计了线性和非线性复合作用的时滞反馈控制器来对波纹辊系的主共振进行控制,并且通过数值仿真验证了控制器设计的正确性和可行性.     

绳驱动柔性上肢外骨骼机器人设计与控制

为了提高上肢外骨骼机器人的拟人化程度及关节柔性,设计了一种由串联弹性驱动器和鲍登线驱动的4自由度柔性上肢外骨骼机器人.首先,设计一种六连杆双平行四边形机构,建立肩关节虚拟转动中心,满足人体肩部3自由度运动需求.然后,设计基于串联弹性驱动器和鲍登线的驱动模块,将驱动器和机器人关节分离,降低结构的复杂度,减轻关节质量,实现力矩/位置信息的反馈.最后,构建机器人运动学及动力学模型,设计关节阻抗控制器并对样机肘关节进行阻抗控制实验.由实验结果可知,刚度系数在0.5 N·m/(°)～1.5 N·m/(°)时,力矩跟踪均方根为0.33 N·m;阻尼系数在0.001 N·m·s/(°)～0.01 N·m·s/(°)时,力矩跟踪均方根为0.57 N·m.实验结果表明,调节阻抗控制器中的阻抗系数能够改变关节的刚度和阻尼特性,从而提高人机连接的柔顺性.因此该机器人可以满足康复训练需求.     

颗粒离散元法中阻尼系数、刚度系数和时步的选取方法

为解决颗粒离散元法(Distinct Element Method,DEM)中阻尼系数等参数选取困难的问题,对岩体工程中的DEM与颗粒DEM进行区分,着重讨论颗粒DEM中阻尼系数、刚度系数和时步等参数的选取方法.这些计算参数的合理选取对保证模拟的真实性具有重要意义.     

Active-head slider with piezoelectric actuator using shear-mode deformation

The active-head slider technology for hard disk drive is one of the most promising means to decrease flying height. This paper describes a piezoelectric flying height control slider which has a faster dynamic response compared with conventional active-head sliders. This slider can be also adapted to the conventional slider-fabrication process. PZT layer located near the magnetic head has shear mode deformation by applying electric voltage between the upper and lower electrodes when the flying height of magnetic head needs to be decreased or increased. We fabricated a prototype with single crystal Si substrate for feasibility study. Our evaluation of the prototype revealed that the piezoelectric constant of the shear mode deformation was 0.88 nm/V, and the dynamic response was 50 kHz. The shape of the air bearing surface was optimized by simulations using a robust design method. We found that the stroke was 8 nm for an applied voltage of 11 V if the flying height was 11 nm with no deformation in PZT.     

Active-head sliders using piezoelectric thin films for flying height control

This paper describes design and fabrication of a MEMS-based active-head slider using a PZT thin film for flying height control in hard disk drives. A piezoelectric cantilever integrated in the air bearing slider is used to adjust the flying height individually. An air bearing surface (ABS) geometry that minimizes the aerodynamic lift force generated beneath the head has been designed based on the molecular gas film lubrication (MGL) theory. The sliders with PZT actuators were fabricated monolithically by silicon micromachining process. Performance of the actuator was tested by using an optical surface profiler. Furthermore, the fabricated slider was mounted on a suspension and the flying height of the slider above a spinning disk has been measured by multiple wavelength interferometry. Change in the head-disk spacing has been successfully confirmed by applying voltage to the actuator.     

Probing and diagnosis of slider–disk interactions in nanometer clearance regime using artificial neural network

This paper addresses the issue of system identification for an active-head slider used to form a stable and reliable head–disk interface with a spacing of sub 3?nm. A new identification method is proposed to fit the highly non-stationary and highly nonlinear slider dynamics. The estimated model can be used for design of a model based nonlinear controller to control the flying height within the desired range. The effectiveness of the proposed system identification method is verified with simulation examples.     

An approach for non-stationary and nonlinear vibration identification and control of active air-bearing slider system

This paper addresses the issue of system identification and controller design for an active-head slider used to form a stable and reliable head-disk interface with a spacing of sub 3?nm. A new identification method is proposed to fit the highly non-stationary and highly nonlinear slider dynamics. The estimated model is then used for the design of a model based nonlinear controller to control the flying height within the desired range. The effectiveness of the proposed system identification method and the nonlinear controller is verified with simulation examples.     

Effect of thermal pole tip protrusion and disk roughness on slider disk contacts

Ultra-high areal density for hard disk drives requires a stable head disk interface at a flying height lower than 8 nm. At such a low flying height, small flying height variations may cause slider/disk contacts. Slider/disk contacts can also occur when a write-current is applied to the write coil since the flying height between slider and disk can be affected by the thermal expansion of the pole tip. In this paper, we investigate the vibration characteristics of sliders during thermally induced contacts using laser Doppler vibrometry. We perform a parametric study of contact events using disks with different surface roughness and lubricant thicknesses, and analyze the slider motion statistically. For a given write current, we observe that the slider vibrations increase with disk roughness and lubricant thickness.     

Experimental study of slider�Cdisk interaction process with thermal-flying-height controlled slider

Thermal flying height (TFC) controlled slider has been introduced in hard disk drive recently. Flying height at the read/write elements of the slider is controlled by thermal pole tip protrusion. Interactions between the TFC slider and disk can be very gentle because the low flying height thermal protrusion area is usually very small. It is still a big challenge to detect very gentle interactions. In this work, a very sensitive method to study very gentle slider?Cdisk interaction in frequency domain has been developed and details of the TFC slider?Cdisk interactions from gentle to strong have been revealed. It is proved that higher heating power is required to initiate the vibration in which higher stiffness part of the slider air-bearing is involved.     

Intermolecular force and surface roughness models for air bearing simulations for sub-5 nm flying height sliders

When the spacing between the slider and the disk is less than 5 nm, the intermolecular forces between the two solid surfaces can no longer be assumed to be zero. The model proposed by Wu and Bogy (ASME J Trib 124:562–567, 2002) can be view as a flat slider–disk intermolecular force model. The contact distance between the slider and disk needs to be considered in this model when the slider-disk spacing is in the contact regime. To get more accurate intermolecular force effects on the head disk interface, the slider and disk surface roughness need to be considered, when the flying height is comparable to the surface RMS roughness value or when contact occurs. With the intermolecular force model and asperity model implemented in the CML air bearing program, the effect of intermolecular adhesion stress on the slider at low flying height is analyzed in the static flying simulation. It is found that the intermolecular adhesion stress between the slider and the disk has slight effect on the slider-disk interface for a flying slider.     

Effect of reduction of slider pitch-mode vibration on magnetic-recording performance at low-clearance head–disk interface

Aiming at improvements of both stability of slider flying and magnetic-recording performance under a low-clearance condition, a “narrow-grooved slider” was constructed and demonstrated at drive level. The proposed slider has narrow grooves on its center pad of an air-bearing surface for attaining a high-damping effect on pitch-mode resonant vibration of the air bearing. The relationship between the high-damping effect and the pitch-mode resonant vibration was studied, and the magnetic-recording performance at the lube/slider interaction regime was improved. In this study, first, flying-height modulation (FHM) of the slider was analyzed in the frequency domain by using a fast Fourier transform. Compared with the narrow-grooved slider, a non-grooved slider showed a larger increase in high-frequency modulation of gap flying height when the clearance was reduced to near “zero” at which the slider is starting to interact with lube. Furthermore, by means of drive-level experiments, sector error rate (SER) as a function of flying clearance was investigated. Under a low gap flying height condition, HDDs with the non-grooved slider showed slight SER degradation during slider/lube interaction. However, the narrow-grooved slider did not show any SER degradation at the same gap flying height; the damping effect of the narrow-grooved slider suppressed high-frequency FHM, thereby preventing SER degradation in the slider/lube interaction region.     

磁记录浮动块动态参数仿真

建立了考虑浮动系统动态特性综合分析的近似模型;在磁记录浮动块动态性能方面,给出了浮动系统动力参数(刚度、阻尼、固有频率)及其变化特性的仿真测试方法与结果。     

Approaches to reduce effect of short-range interactions in head disk interface

Different approaches to reduce the effect of short-range interactions on slider’s flying stability—reduction of pad width at trailing edge and increase of air pressure on trailing pad—are compared for the flying stability and flying height modulation. The static and dynamic simulations show both approaches can reduce the effect of intermolecular force and electrostatic force on the slider’s flying stability. On the other hand, the increase of air pressure on trailing pad can also reduce the flying height modulation caused by disk waviness, but reduction of pad width at trailing edge increases the flying height modulation. Hence, the increase of air pressure on trailing pad is more suitable for the application of the ultra low flying height in hard disk drives.