Optical memory and blue lasers

Optical memory and blue lasers are bringing a revolutionary change to the electronics industry. A single 5.25 inch optical disk will replace the four hundred 3.5 inch magnetic diskettes required to store a 600 Mbyte database. Optical memory brings an explosion in storage density to information recording in a form which is reliable, economical and portable. Increasing the storage density further requires shortening the wavelength of the laser light utilized. Semiconductor blue lasers will offer this enhancement and allow great strides in industries such as image processing     

The characteristics of a dual-layer optical disk with read-only anderasable functions

A dual-layer optical disk comprised of a read only layer and a phase-change layer was designed to perform the read-only and erasable dual-functionality in an optical disk. With the properly designed dual-layer disk structure, 23 mW of write power was adequate to write data marks on the erasable phase-change layer; simultaneously, equal magnitude of sufficient radiofrequency readout signals could be obtained on both its data layers. The analyzes of its recording characteristics demonstrated the feasibility of the dual-functional optical disk     

磁电阻磁头结构设计与计算机仿真

讨论了磁电阻（ＭＲ）磁头结构参数设计与计算机仿真将磁电阻磁头应用子磁盘高道密度记录技术，有利于提高磁头读出的信噪比，对于实现磁盘更高的道密度和位密度大容量小型化都具有重要意义。     

用于磁盘预光刻伺服图形音圈电机的设

为了实现磁盘高道密度记录技术，本文对磁盘伺服图形预刻装置驱动系统—音圈电机进行了优化设计，这样不但满足了预光刻磁盘的道密度达到６３５０ＴＰＩ要求，同时也提高了磁盘刻写速度，有利于进一步提高磁盘记录密度     

Cloud storage application area of HDD–SSD hybrid storage,distributed storage,and HDD storage

For a typical IaaS (infrastructure as a service) cloud usage, to strengthen a system, temporary and frequent provisioning of virtual volumes is needed. However, the performance of HDD (hard disk drive) storage is not sufficient and has become a bottleneck in IaaS cloud now. In this letter, we make a comparative study of HDD–SSD (solid‐state drive) hybrid storage, distributed storage, and normal HDD storage as the block storage of OpenStack Cinder, and evaluate the applicability of these three types storage to the IaaS cloud. Hybrid storage can achieve much higher performance compared to HDD storage and is suitable for analysis applications, but distributed storage performance degradation is lower than HDD storage when the number of concurrent processing is increased and is suitable for archiving or storing a large number of files. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Robust feedforward control system considering sudden disturbance for optical disk recording system

This paper proposes a new robust feedforward tracking servo system for optical disk recording systems in the case of a sudden disturbance for the optical disk recording system. In optical recording systems, the tracking servo system must suppress tracking error below its tolerance. This paper designs the robust feedback control system by using the coprime factorization and disturbance observer. The proposed robust feedback control system suppresses the sudden disturbance caused by walking and running. The detecting signal of optical disk recording systems is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both Zero Phase Error Tracking (ZPET) control theory and prediction of tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 60– 68, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20257     

A New Starting Method of BLDC Motors Without Position Sensor

This paper presents a novel method to detect the rotor position of the brushless dc (BLDC) motor of a hard disk drive (HDD) at a standstill and a startup method to accelerate the rotor up to a certain speed where the conventional position sensorless control methods based on the back electromotive force could work reasonably. The proposed initial rotor-position-estimation method is suitable to avoid the temporary reverse rotation or the starting failure of the HDD. The principle of the estimation is based on the variation of the current response caused by the magnetic saturation of the stator core of the BLDC motor when the current flows along the magnetic axis. This method can be implemented using only one current sensor at the dc link of the inverter, which is a prerequisite for the HDD drive. It does not depend on the model of the motor, and it is robust to motor parameter variations. Using the proposed method, it is demonstrated experimentally that a stable start-up can be achieved even with a severe mechanical disturbance     

磁记录介质的表面形貌和磁结构的观测

使用磁力显微镜和偏光显微镜观测了硬磁盘，磁光盘，录像带，录音带和磁卡的表面形貌和磁结构，揭示了磁记录介质的信息存储状态，对于不同的记录模式，介质的磁结构截然不同，并且表面平整度也有差别，记录密度越高，介质表面越平整。     

片状钡铁氧体纳米磁粉的研究及应用

介绍了高密度磁记录媒体用的片状，替代式钡铁氧体纳米磁粉制备方法及其磁特性。分析，讨论了高密度记录对记录媒体磁特性的要求，介绍了最近研制的，先进的钡铁氧体纳米粉磁带及软磁盘的高密度度灵放特性。     

磁光记录薄膜擦写疲劳特性测试系统的研制

成功研制了磁光记录薄膜擦写疲劳特性测试系统。系统中利用串联谐振法 ,获得了重复频率为 1 k Hz、峰值磁场达 4 0 k A/m的高频双向脉冲磁场 ,同时采用除法式读出消除了读出激光功率波动     

Recent progress in high-power blue-violet lasers

The property of GaInN-AlGaN heterostructures and GaInN multiple quantum well (MQW) gain GaInN laser diodes with low internal loss are described. GaInN blue-violet laser diodes have been developed as a light source for optical disk recording. However, the threshold current density of these diodes has been difficult to reduce and remains high at around 3-4 kA/cm/sup 2/. This is thought to be due to the large transparency current density Jt and the large optical internal loss /spl alpha//sub i/. Recently, the internal loss was successfully reduced to 13.6 cm/sup -1/ by optimizing the design of the near active region and achieved stable continuous operation under 50-mW continuous wave at 70/spl deg/C. Other laser characteristics such as far-field patterns and laser noise have also been improved for optical disk use.     

Long‐span seek control system for hard disk drive without mode‐switching

In hard disk drives (HDD) there are two control modes: the head positioning control mode and the other is the seek control mode. In the head positioning control mode, a feedback controller is optimally designed to suppress disturbances. In the long‐span seek mode, a velocity feedback control system is applied in order to move the heads fast. Thus, an HDD has multiple control systems, and the head is moved to the target position while changing from one control system to the other. However, changing the control system causes a discontinuous control signal, which activates the resonant mode of an actuator. Past methods can only decrease discontinuous control, and therefore a single control system that can be used for both a seek control mode and a head positioning control mode is necessary for a narrow track pitch. In the proposed method, the feedback controller is decomposed into an integrator and a phase compensator. The VCM model is updated by the output of the phase compensator, and the integrator and the output of the velocity feedback controller control the VCM. The validity of the proposed method was confirmed by numerical and experimental results using a miniature 2.5‐inch hard disk drive. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 51–60, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20935     

硬盘驱动器两级磁头伺服系统的精确定位

为了获得硬盘驱动器系统较快的寻道速度和较高的定位精确度,采用音圈电机作为第一级致动器控制磁头进行粗定位,微致动器作为第二级致动器控制磁头臂实现精定位和磁道跟踪.在建立硬盘驱动器系统模型并将复合非线性反馈控制律应用于此模型的基础上进行仿真实验.结果表明,磁头能实现快速精确的定位,其性能优于采用简单的线性反馈控制律所获得的控制效果.     

Storing magnetic data

Magnetic recording data storage innovation and product evolution is arguably higher than it has ever been. For example, the current record in high density recording is 23.8 Gbit/in², which was demonstrated by Seagate Technology. Data is stored by creating a pattern of magnetization in the media using a recording head. Basically, the head is a split ring-shaped core of easily magnetized material wrapped by a few turns of wire. When current flows in the wire, it induces a magnetic flux in the core and a field across the recording gap. Reversing the current's direction changes the direction of the magnetic field. Because the field lines spread out as they bridge the gap, they magnetize the media in a small zone near the gap. Since data is stored as binary digits, a pattern of current reversals can be coded to represent binary digits. For example, “1” might be represented by a magnetization reversal and “0” by the absence of a reversal. Data is read by sensing the fields that arise from the magnetization transition zones in the media. These fields are caused by a concentration of magnetic poles at the ends of each magnetized region. Since these fields point in the opposite direction to the media's magnetization, they are called “demagetizing fields” These fields extend beyond the media's surface. Thus, they can induce responses in a read head if it is brought close to the media     

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。     

阵列式表面肌电信号采集仪

采用阵列式电极,通过空间滤波方法可提高表面肌电信号的MUAP分辨能力。本文实现的阵列式表面肌电信号采集仪由表面肌电电极阵列、信号调理电路和数据采集部分构成。表面肌电电极阵列实现了镀金圆盘式和弹簧探针式两种类型,信号调理电路对电极上的肌电信号进行放大和滤波,数据采集部分将调理后的信号转换成数据并进行显示和存储。电极阵列和前级信号调理电路集成在一起,有效的降低了微弱信号通过导线传输所引入的干扰。通过实验,验证了这种阵列式表面肌电采集仪在研究肌肉中动作电位传播和利用空间滤波提高MUAP分辨力的可行性,并证实了镀金圆盘式电极在降低噪声方面、弹簧探针式电极在缩短MUAP时长方面的优势。     

基于磁光硅基微环波导的磁场测量研究

根据磁光效应引起的附加介电常数张量,分析了磁光波导中导波光传播特性对光场模式和磁场配置的依赖关系。采用SiO_2/Si-Ce:YIG/SiO_2硅基磁光波导设计了一种微环谐振结构用于磁场测量,仿真计算了准TE模导波光传输时微环谐振波长移动随垂直磁化强度的变化。对于半径为23.6μm的磁光微环,优化波导宽度可使磁场测量灵敏度达到0.0054nm/(k A/m),饱和磁化时微环谐振波长移动为0.52nm。     

Servo techniques for optical disk drives —high-speed and precise optical beam-positioning control—

We introduce advanced servo techniques for optical disk drives. High speed and precise optcal beam-positioning and following controls are required archival memories such as high density and high data transfer rate optical disk drives for recording many data and high quality moving pictures toward next generation systems. The zero phase error tracking-feed-forward (ZPET-FF) control method is effective for the next generation systems, which have high disk rotation speed beyond the limit of 10,000 rpm of optical disk drives such as current CDs, DVDs or Blu-ray discs. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High-density disk storage by multiplexed microholograms

We propose a concept of holographic data storage which promises storage capacities of more than 100-Gbyte on a digital versatile disk (DVD)-sized disk. The information is stored bitwise in form of microscopic reflection holograms. High storage densities can be achieved by combining multiplexing methods and multilayer storage. A theoretical model for microscopic reflection holograms generated by focused Gaussian beams is proposed. Experimental results are presented for the recording and characterization of microholograms in DuPont's HRF-800 photopolymers. The local distribution of the diffraction efficiency was investigated by applying a confocal scanning microscope setup. Single-color holograms with a radius of 1.8 and 12 μm depth have been recorded. We observe a blue shift in the spectral response of the microholograms of less than 2% due to shrinkage of the polymer. In the case of threefold wavelength multiplexing, all wavelengths are clearly resolved in the spectral response having spectral width Δλ of less than 10 nm (FWHM). Baking the holograms for 1 h at 120°C nearly doubted the diffraction efficiency while the spectral response of the microholograms broadened by a factor two. We showed that 80-ps pulses are sufficient for holographic recording in the photopolymers. An optimized pre-illumination allows a significant increase in diffraction efficiency     

基于DSP的光纤电流互感器设计研究

为满足现代电力系统高精度测量和电网信息的需求,研究了光纤电流互感器的信号获取、处理、通信及高压侧电源技术,它由ROGOWSKI线圈获取母线电流信号,经积分、数字化处理及电光转换,由光纤传输至远方,DSP数字处理的信号由大屏液晶显示。高压侧电子电路的工作电源由特制小TA获取,铁心采用饱和磁感应强度较低、励磁电流小、导磁率高的合金材料。母线电流>8 A时电源系统能正常供电,测量误差<0.2%,能满足电力系统电流测量的要求。