OPTIMAL TRACK SEEKING CONTROL OF DUAL-STAGE ACTUATOR FOR HIGH DENSITY HARD DISK DRIVES

Based on generalized the variation method, by introducing Hamilton function and Lagrange multiplier, this paper proposed a linear quadratic optimal control strategy for an incomplete controllable system with fixed terminal state and time. Applying the proposed optimal control to the simple two-input dual-stage actuator magnetic head positioning system with three degrees-of-freedom, the simulation results show that the system has no residual vibration at the terminal position and time, which can reduce the total access time during head positioning process. To verify the validation of the optimal control strategy of three degrees-of-freedom spring-mass models in actual magnetic head positioning of hard disk drives, a finite element model of an actual magnetic head positioning system is presented. Substituting the optimal control force from simple three degrees-of-freedom spring-mass models into the finite element model, the simulation results show that the magnetic head also has no residual vibration at the end of track-to-track travel. That is to say, the linear quadratic optimal control technique based on simple two-input dual- stage actuator system with three degrees-of-freedom proposed in this paper is of high reliability for the industrial application of an actual magnetic head positioning system.

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.

Robust Optimum Design of Thrust Hydrodynamic Bearings for Hard Disk Drives

This paper describes the robust optimum design which combines the geometrical optimization method proposed by Hashimoto and statistical method. Recently, 2.5″ hard disk drives (HDDs) are widely used for mobile devices such as laptops, video cameras and car navigation systems. In mobile applications, high durability towards external vibrations and shocks are essentials to the bearings of HDD spindle motor. In addition, the bearing characteristics are influenced by manufacturing error because of small size of the bearings of HDD. In this paper, the geometrical optimization is carried out to maximize the bearing stiffness using sequential quadratic programming to improve vibration characteristics. Additionally, the bearing stiffness is analyzed considering dimensional tolerance of the bearing using statistical method. The dimensional tolerance is assumed to distribute according to the Gaussian distribution, and then the bearing stiffness is estimated by combining the expectation and standard deviation. As a result, in the robust optimum design, new groove geometry of bearing can be obtained in which the bearing stiffness is four times higher than the stiffness of conventional spiral groove bearing. Moreover, the bearing has lower variability compared with the result of optimum design neglecting dimensional tolerance.

Optimization of passive control performance for different hard disk drives subjected to shock excitation

Laptop personal computers(LPCs) and their components are vulnerable devices in harsh mechanical environments. One of the most sensitive components of LPCs is hard disk drive(HDD) which needs to be protected against damages attributable to shock and vibration in order to have better magnetic read/write performance. In the present work, a LPC and its HDD are modeled as two degrees of freedom system and the nonlinear optimization method is employed to perform a passive control through minimizing peak of HDD absolute acceleration caused by a base shock excitation. The presented shock excitation is considered as half-sine pulse of acceleration. In addition, eleven inequality constraints are defined based on geometrical limitations and allowable intervals of lumped modal parameters. The target of the optimization is to reach optimum modal parameters of rubber mounts and rubber feet as design variables and subsequently propose new characteristics of rubber mounts and rubber feet to be manufactured for the HDD protection against shock excitation. The genetic algorithm and the modified constrained steepest descent algorithm are employed in order to solve the nonlinear optimization problem for three widely-used commercial cases of HDD. Finally, the results of both optimization methods are compared to make sure about their accuracy.

Numerical Investigation of Flow Structure Interaction Coupling Effects in Hard Disk Drives

This paper studies the flow structural interaction (FSI) within a hard disk drive (HDD) through the use of a novel coupling method. The interaction studied was the fluid induced vibration in the HDD. A two step coupling approach was used, where the fluid and structural components were solved sequentially. The result obtained was a ratio of 0.65 between the vibration amplitudes of a fixed head stack assembly (HSA) and a moving HSA. The ratio was next applied on a real 3.5 inch HDD, to allow the parameter to be further improved upon. A new benchmark index of 0.69 was developed from this. This parameter may allow future researchers to model the out of plane vibrations of a HSA easily, saving precious time. A 31% more accurate simulation of FSI within 3.5 inch HDD at 15000 rpm is achieved by the use of this new coupling method and benchmark index.

Heat Source Analysis of Hard Disk Drives with Different Wall Conditions using Infrared System

Increasing performance parameters of hard disk drive (HDD) such as higher capacity and faster data access speed with decreasing physical size make HDD more susceptible to thermal effects. Contact temperature measurement using thermocouple is not suitable for the rotating platter of HDD. Heat analysis using simulation software requires accurate initial parameter setting such as thermal (initial & boundary) conditions of certain regions. Temperature measurement using infrared (IR) system avoids these limitations;it is non-contact, responsive and does not require initial parameter setting. Thermal pattern distribution can be studied from the thermal images. However, emissivity of the target has to be known and calibration of the system is essential for accurate temperature reading. This paper showed that temperature within the HDD increases with ambient temperature and time, but the thermal distribution pattern in the HDD was not affected by different ambient temperatures. Three wall boundary conditions were conducted to study the thermal distribution pattern in the HDD. A solution was then proposed based on the results obtained from the experiments to improve the heat transfer rate and steady state temperature, and reduce the detrimental effects from high thermal generation in future prototypes. Another important finding was that the averaged temperature of the head cap was generally higher compared to that of the disk, as the spindle motor is the primary heat source within the HDD. Heat source analysis of HDD with IR system allows designers to have better visibility of the temperature generated in different components of the HDD. Proper cooling may enhance disk life as well as ensure the stability and integrity of the system.

HARD DISK DRIVES CONTROL IN MOBILE APPLICATIONS

In this paper, control design is investigated for hard disk drives in mobile applications with unknown external arbitrarily fast time-varying disturbances. The disturbances can be estimated with exponential accuracy using the proposed disturbance observer based on a series of integral filters. The position error signal will converge to zero with the proposed control technique for systems subjected to the unknown disturbances. The effectiveness of the proposed method is demonstrated by extensive simulation studies.

Dynamic characteristics of hard disk drive spindles supported by hydrodynamic bearings

Most hard disk spindles currently used are supported by grease lubricated deep-groove ball bearings.However, in the trend of increasing spindle speed and reducing size and cost, the shortcomings of ball bearing spin-dles, such as high non-repeatable run out, high acoustic noise and short life time at high running speed, make themunsuitable for high performance hard disk drives (HDD). On the contrary, the dynamic characteristics of hydrody-namic bearing spindles are superior to that of ball bearing spindles. Therefore, they are considered to be the substi-tute of ball bearing spindles in HDD. In this paper, a simulative setup of HDD is build up. The dynamic characteristicsof liquid lubricated spiral groove bearing(SGB) spindles are studied. The effects of both operating condition andbearing clearance are investigated. It is found that running speed of the spindle has significant influence on its dy-namic performance, while the load has little influence. The effect of clearance is also evident.

Design of Intersample Response in a Hard Disk Control System

The present paper discusses a design method for the head position in a Hard Disk Drive （HDD） control system. In the HDD control system, the sampling interval of the head position is constrained because of the hardware specifications, but the hold interval of the control input is not constrained. In the present study, a multirate control system is designed, in which the sampling and the hold intervals are not equal. A multirate control law, which stabilizes a closed-loop system, is extended using newly introduced parameters such that the sample response of the plant output is maintained. Furthermore, intersample ripples in the steady state are eliminated using the new design parameters, which can be selected independently of the sample response. As a result, the intersample response can be improved independently of the sample response. The proposed method is applied to a benchmark problem of an HDD system, and its effectiveness is demonstrated.

噪声激励下的硬盘频响特性研究和性能预测模型

针对服务器硬盘在高噪声环境下性能下降问题,设计了一种试验方法来分析噪声激励下硬盘性能损失的敏感度特性。通过编程模拟不同频率和强度的1/9倍频程带宽的均匀随机噪声,测试硬盘在噪声激励下产生的性能损失。通过机理分析和试验数据分析,建立回归方程,提出敏感度(K)的数学模型。建立了预测硬盘性能损失的数学模型,基于服务器机箱内散热风扇产生的真实噪声信号可计算出硬盘性能损失率。在多种场景的检验中发现预测模型的结果非常接近实际结果,证明此方法是一种非常准确的分析和预测手段,为服务器系统的声学设计提供有效的量化参考。

机械硬盘加速寿命试验及状态监测技术研究

机械硬盘的健康状态监测和诊断对于企业的安全可靠运行和节约运维成本起着至关重要的作用。首先,分析了硬盘的基本组成和不同环境应力下的故障模式和机理;其次,根据实际运行环境制定了加速寿命试验,并在试验过程中对硬盘的SMART数据进行采集和存储;最后,经过对比和分析发现了该型号硬盘的敏感SMART参数,并发现寻道出错率具有明显的退化趋势,可用于故障预警和预测。

基于SMART数据模式的HDD硬盘状态预测方法

硬盘广泛应用于各类信息系统中,其工作状态预测对信息系统的正常运行管理有着重要意义。现有基于SMART(Self Monitoring Analysis and Reporting Technology)属性的机器学习预测算法为保证其通用性,普遍选取部分典型属性作为特征,带来一定的信息丢失。在分析SMART数据特点的基础上,提出数据模式分类后再进行机器学习预测的SMART数据处理方法。实际测试结果表明,经分类处理后,采用简单的机器学习算法即可获得与强分类器接近的性能,同时,该方法可有效简化SMART数据机器学习时的特征选择过程,有效降低算法的资源消耗。

计算机硬盘用6061铝合金型材生产工艺研讨

计算机硬盘驱动臂用6061铝合金型材的质量要求严苛.应用铝熔体深度净化技术、再结晶晶粒控制技术、等温挤压技术等各类新技术和新装备对合金的成分和生产工艺进行试验研究.结果表明:应用新技术和新装备,采用合理的生产工艺以及合金优化设计,能够生产质量完全满足标准要求的产品.

硬盘抗冲击振动特性的研究进展

硬盘驱动器是计算机最重要的外存储设备。由于硬盘抗冲击振动问题的重要性和复杂性,许多研究者对此问题从各个方面进行了研究。本文从硬盘的基本结构和工作原理入手,介绍了磁头/磁盘系统的静动态特性,分析了影响磁头/磁盘系统性能的重要因素及其原理,并对国内外有关提高硬盘抗冲击振动性能的研究进行了较为系统的回顾和分析,最后阐述了硬盘冲击振动的控制研究,分析了硬盘目前所面临的关键问题及其可能的解决方案。

磁悬浮硬盘的转矩耦合研究

提出了磁悬浮系统的转矩耦合问题 ,转矩耦合对于磁悬浮硬盘系统的工作性能有较大的影响。推导出了磁悬浮主轴耦合转矩的计算公式 。

硬盘驱动器冲击激励的头盘碰撞分析

根据Winchester型硬盘驱动器在冲击载荷作用下头盘碰撞的动力学方程,利用数值模拟方法分析了在正弦半波激励条件下头盘系统的动力学响应过程。当头盘系统发生碰撞时,冲击激励峰值加速度与作用时间的倒数之间具有近似线性关系。随激励强度和作用时间的变化,硬盘驱动器具有性能退化、盘面局部损坏和头盘系统结构破坏三种失效形式。磁头浮动块与磁盘盘面发生多次碰撞,碰撞位置可能在浮动块尾端,也可能在浮动块的前端。硬盘驱动器冲击失效的理论分析结果得到了爆炸冲击环境条件下试验现象的验证。

工业大数据驱动的故障预测与健康管理

新一代人工智能技术的发展与应用装备积累了大量数据,推动着故障预测与健康管理(PHM)进入了工业大数据时代。结合装备的功能作用、结构组成和工作特点,分析装备大数据,进行价值挖掘、信息提取进而实现装备的状态监测、异常预警、故障诊断、寿命预测、智能维护等工作十分迫切。在回顾并剖析当前PHM技术内涵、发展现状与应用的同时讨论了装备工业大数据的特点、分析方法及其工作中的难点和疑点。以风力发电机组和机械硬盘两类典型复杂装备为例,从工业大数据角度对其PHM技术进行探讨,总结当前研究工作的热点与不足,思考未来研究方向,以期为相关领域的研究人员提供一定参考。

硬盘磁头快速精确定位伺服控制系统的设计

针对以音圈电机作为伺服机构的硬盘磁头定位伺服系统的性能要求,设计了一个参数化的控制器并进行仿真和实验研究。在控制设计中,采用一种复合非线性反馈(CNF)控制技术,以提高控制系统的瞬态性能,达到快速的响应和低超调;通过设计一个降阶观测器对伺服系统中的未知扰动进行估计及补偿,消除扰动可能带来的稳态跟踪误差。仿真和实验结果表明硬盘磁头可以实现对目标磁道快速准确的定位。参数化设计的伺服控制器具有通用性,可推广应用到其他伺服系统。

基于混合存储的无盘网络服务器数据优化分布方法

无盘网络服务器需处理大量I/O操作,导致其存储子系统成为系统性能提升的瓶颈。为解决该问题,提出基于固态硬盘(SSD)和硬盘驱动器(HDD)混合存储的数据分布方法,使工作站共享的操作系统和应用程序镜像数据分布于SSD,而将工作站运行过程中的镜像修改数据分布于HDD。根据无盘网络服务器I/O数据块访问特性,建立块分布模型,由此设计SSD和HDD间的数据块动态迁移方法,根据SSD和HDD中块的访问信息计算数据分布概率,并动态决定数据块的保存位置。实验结果表明,该方法可有效提高工作站启动速度及存储系统带宽,减少SSD写次数。