Tilt detection and servo control method for the holographic data storage system

Recently photopolymer with disk type substrate is selected as a media of the holographic data storage system. Because shape of the media is a disk, a disk tilt must be occur when the media rotates. When disk tilt occurs the angle between the reference beam and the media is changed by the tilt, thus the data can not be recorded with a right angle or another data page is retrieved. The holographic data storage system is very weak to the tilt disturbance by the Bragg effect, therefore it is necessary to detect the disk tilt angle and compensate it. In this study, we measure the amount of the tilt error using external photo detector and compensate it by rotating the angle of galvano mirror with our own algorithm.     

Tracking servo method using reflective optical filter for holographic data storage system

Holographic data storage system is one of the next-generation data storage systems and is characterized by its high storage density and fast data transfer rate. However, holographic data storage systems are very sensitive to disturbances that affect the position of the media. Therefore, tracking servo control is needed to ensure a good performance of the system even if disturbances occur, such as eccentricity of the disk and external shock. In our previous researches on tracking servo methods, we used additional beams or recorded servo track images with data pages to record additional gratings with data pages. Therefore, the recording density may be reduced and the system may be complicated. In addition, the performance of the system may be compromised by cross-talk noise caused between the reference beams and additional beams. In this paper, we propose a tracking servo method using the residual beam, which is reflected by the reflective optical filter. This method does not require recording supplementary gratings or use additional beams, and only needs to record data pages. The residual beam is retrieved with desired retrieved beam by the reference beam and wasted during the retrieving process. We first constructed a holographic data storage system and designed a reflective optical filter to detect tracking error signals. After detecting the tracking error signals, a tracking servo controller using a lead-lag compensator was incorporated to reduce the tracking error signals. The performance of the designed controller was verified by simulated and experimental results. Finally, the performance of the tracking servo method was investigated by comparing the retrieved data images.     

Suggest a format for intelligence control and structure of holographic data storage system

Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time. Today any data storage system cannot satisfy all of these conditions, however holographic data storage system (HDSS) can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System can be constructed without mechanically actuating part therefore fast data transfer rate and high storage capacity about 1Tb/cm3 can be realized. In this research, to reduce errors of binary data stored in HDSS, a new method for bit error reduction is suggested. Firstly, find fuzzy rule using test bed system for Element of Holographic Digital Data System and make fuzzy rule table using subtractive clustering algorithm and genetic algorithm and Reduce prior error element and recording digital data. Secondly, Reduce prior error element and recording digital data using the particle filter method. Finally, Recording ratio and reconstruction ratio show good performance and we suggest intelligence control method and filter method. Our format table include intelligence control algorithm and filter method.     

New multiplexing method of holographic data storage system

Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time. Today any data storage system cannot satisfy all of these conditions, however holographic data storage system can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System can be constructed without mechanically actuating part therefore fast data transfer rate and high storage capacity about 1Tb/cm3 can be realized. In this research, to record and retrieve binary data by a new hologram multiplexing in our holographic data storage system, we propose a new multiplexing method that is cyclone multiplexing method. Also, three algorithms were integrated in our holographic data storage system.     

基于ElGamal的同态云端密文存储检索方案

云端数据存储的安全性和检索效率是网络空间安全亟待解决的问题之一. 本文提出了一个新的密文检索模型, 并在此基础上利用ElGamal同态密码算法和SM4分组密码算法, 设计了一种基于混合同态加密的云端密文存储检索方案. 首先, 该检索方案能够在数据上传、检索和下载的过程中, 保证数据的安全, 可用于个人云端U盘等应用场景. 其次, 对该方案的正确性和安全性进行分析. 最后, 通过实验的方式对方案的正确性进行了证明. 实验结果表明该方案在保证数据安全的情况下, 检索结果正确, 效率高.     

Real time servo control of the holographic data storage system with an additional servo beam

Holographic data storage is a next generation data storage device, which has high storage density, high data transfer rate and short access time. The device is very sensitive to disturbances due to its enormous storage density. In the disk type holographic data storage device deviation occurs successionally on the position of the data as the disk rotates. Therefore the spot where the probe beam is illuminated should directly be corrected in order to exactly retrieve the desired data. In this paper we suggest a method using an additional beam containing a servo pattern in order to detect the deviation of the media. We also propose a real time servo control method to compensate the affect of the unpredicted disturbance.     

多旋翼无人机磁罗盘校准方法

为提高多旋翼无人机航向角解算精度,研究磁罗盘校准和罗差补偿方法。通过详细分析罗差产生原因,并结合多旋翼应用,将磁罗盘干扰划分为机体坐标系静态干扰、机体坐标系动态干扰、导航坐标系静态干扰、导航坐标系动态干扰四大类。针对机体坐标系动态干扰,结合多旋翼应用背景,研究干扰的离线测量与在线补偿方法;针对机体坐标系静态干扰,提出一种飞行过程中实时校准方法;针对导航坐标系静态干扰,创新性采用GNSS模块的速度方向信息修正罗差;导航坐标系动态干扰为原理性误差,这里暂不讨论。结果表明：研究内容可有效补偿机体坐标系动态与静态干扰,以及导航坐标系静态干扰对磁罗盘和航向角解算精度的影响,有助于改善无人机的飞行性能。     

结合分段位图和B 树的云数据索引机制研究

位图索引因其简单有效的优势被广泛应用于海量数据的分析处理。针对位图索引数据存储空间大,检索效率低的问题,提出了一种结合分段位图和B 树的云数据索引机制(简称BBI索引)。BBI索引在索引创建时按照一定的基数对元组数据进行分段,以段为单位建立位图索引,索引数据量的决定因子由属性值的取值范围转变为分段数与基数的乘积,大大减少了索引数据量;同时,在每个数据节点上建立B 树,避免了数据检索时对非结果数据的逐个遍历,从而显著提高了数据的检索效率。实验结果表明,BBI索引是一种性能较优的云数据索引机制。     

一种多通道并行固态存储系统的设计与实现

鉴于高速数据采集系统对实时数据存储带宽和容量的要求,提出一种基于现场可编程门阵列（FPGA）的高速多通道并行固态存储系统。该系统以现场可编程门阵列器件XCV5LX110T为核心,选用大容量高速闪存芯片作为存储介质,通过采用并行总线拓宽技术和流水线缓冲技术,在FPGA片内搭建高速多通道并行存储硬件架构,从硬件角度提高系统的数据吞吐带宽。设计一种基于超级页的地址映射策略,并使用该策略对闪存转换层算法的请求处理机制进行并行加速优化,从软件角度提高系统的存储并行性。测试结果表明,该系统的最大存储速度达到73MB／s,其性能指标能满足高速实时数据存储的需求,证明多通道存储架构和FTL算法具有良好的并行性和可扩展性。     

基于多尺度投影的相似颅骨检索

在基于模板变形的颅面复原方法中,复原的开始阶段需要在数据库中选取与待复原颅骨最为相似的参考颅骨.鉴于基于三维模型的检索算法时间久且颅骨间的差异细微,从而不同于一般三维模型数据库中各模型的差异.因此,已有的三维模型检索算法不适用于颅骨检索.本文提出一种夹角信息和距离信息融合的颅骨轮廓特征提取算法,并在此基础上提出一种能够反映颅骨空域信息的剖面特征提取算法.检索时首先获取三维颅骨的正交投影和深度投影,通过正交投影获取轮廓的角度和距离特征,通过深度投影获得具有空域信息的剖面特征;然后对多个特征进行加权融合搜索到最相似颅骨;最后通过ICP+TPS对检索到的颅骨进行误差评估.实验表明,本算法在保证检索效率的同时,可以准确地应用在颅面复原前期对最相似颅骨的选择上.     

弹载地磁测量系统的抗干扰设计

为了消除弹载地磁测量系统所受的矿山、电磁、金属等干扰,本文设计了充磁电路,消除强磁场对磁阻传感器的干扰;设计了滤波电路及合理的布线,消除高频干扰信号;再提出了误差识别补偿及看门狗设置算法,补偿了软硬磁干扰、零位误差、正交误差。转台试验与数据分析表明:各组合方法的采用,减少了干扰误差使姿态角测量精度达到1°以内,具有一定的工程价值。     

仿生鳍条姿态测量及其误差分析

仿生鳍条是仿生机器鱼的核心运动机构,为提高其运动控制精度,针对其轻巧、微小的结构特点,设计了以质量轻、体积小、精度高的MEMS陀螺仪ADXRS290和ADXRS453为核心的仿生鳍条姿态测量系统,可实现仿生鳍条偏航角、俯仰角和滚转角的实时测量;针对仿生鳍条姿态测量中随机误差较大的特点,给出了一种以Allan方差为主的姿态测量误差算法,然后通过实验采集测量数据,定量分析了各运动姿态误差项;实验结果表明,角速率随机游走和零偏不稳定性是姿态测量的主要误差项,在后续误差处理中做针对性处理能提高姿态测量精度,对提高仿生鳍条运动效率有很大的意义。     

基于视觉伺服的LED芯片形状匹配算法研究

LED芯片的定位是LED芯片检测、分选等后封装过程的关键步骤,其定位速度和精度直接决定了LED芯片检测设备的生产效率。为了提高芯片定位的精度,提出了基于视觉伺服的反馈补偿技术,有效补偿了芯片定位误差;为了提高芯片定位的速度,在视觉伺服系统的基础上,针对LED芯片的特点,提出形状匹配优化算法,通过减小匹配过程中匹配的面积和搜索的角度,有效弥补了因视觉运动补偿所消耗的时间。通过以上两方面提高了LED芯片定位精度和速度,满足LED芯片高精和高速的定位需求。     

用于体全息存储系统的纠错编码及数据交错技术

体全息存储系统具有存储容量大、数据传输率高、存取时间短和可快速进行图像匹配及内容相关寻址操作等特点 .但要成为特性优良的通用型信息存储系统 ,就必须以可接受的误码率同时满足这些性能指标 (计算机外存储器的基本要求是使用户误码率低于 10 - 12 ) .如此 ,仅靠光学设计不是高性价比方法 .设计恰当的纠错编码和数据交错技术可以减轻对原始误码率的要求 ,缓解对系统设计、部件质量等方面的要求 ,在不牺牲其它系统目标的情况下 ,使 10 - 5的原始误码率达到 10 - 12的最终误码率水平 .研究了体全息存储通道中的噪声源及适用于体全息存储系统的纠错编码和数据交错技术     

西安市数字方志全文检索系统的设计与实现

通过LuceneAPI实现对PDF文档的一次全文检索,为了更精确地定位搜索关键词,设计并实现了一种新的二次索引算法,该二次索引带有关键词的页码、坐标及其上下文等信息。利用该二次索引可将检索结果定位到PDF文档的具体页,然后在页面上标示出关键字的具体位置,使对PDF文档的二次检索达到了类似GoogleBook的图书检索效果。系统测试结果说明系统具有良好检索性能,有较高的查全率和查准率,能够满足用户快速检索的需求。系统作为西安市数字方志全文检索平台投入使用已有2年,取得了较好的应用成果。     

LSB page refresh based retention error recovery scheme for MLC NAND Flash

NAND Flash memories present inevitable decline in reliability due to scaling down and multilevel cell (MLC) technology. High retention error rate in highly program/erase (P/E) cycled blocks induces stronger ECC requirement in system, causing higher spare bits cost and hardware overhead. In this paper, a least significant bit (LSB) page refresh based retention recovery scheme is proposed to improve the retention reliability of highly scaled MLC NAND Flash. As in the scheme, LSB page refresh operation induces floating gate electron re-injection to compensate charge leakage during long retention time, and realizes retention error rate reduction. Experiment result on 2x-nm MLC NAND Flash exhibits more than 78% retention error rate reduction. Comparing with reported retention error recovery scheme, the proposed scheme presents 2.5 times recovery efficiency promotion and 60% latency reduction.     

基于闪存的混合存储系统缓冲区管理算法

由于基于闪存的混合存储系统充分利用了闪存的高速随机读和磁盘的快速顺序写的特性,近年来已经成为了数据库管理系统的二级存储层的高效存储模式,但其I/O访问开销是一个继续提高存储性能的瓶颈.为了降低混合存储系统的I/O访问开销,提出了一种自适应缓冲区管理算法DLSB.该算法根据数据页的逻辑代价和物理代价进行自适应的数据域选择;并在选择的数据域中,比较闪存队列和磁盘队列容量的实际值与理想值来确定数据页的置换,达到了提高I/O访问效率的目的.实验结果表明,该算法有效且可行,显著降低了混合存储系统的I/O访问开销.     

离线应用本地数据存储设计与实现

为解决离线应用系统中本地数据数据存储问题,设计与实现一个以开源数据库SQLite为底层存储的数据存储方案.针对开源SQLite数据库只支持明文存储的不足,提供了两种可选的加密解密算法,并研究和评估了这两种不同的加密解密算法对数据存储效率的影响.在实现本地数据存储层的基础上,提出了一种实用的数据存储模型,以方便离线应用结构化数据的存取.     

云储存中利用属性基加密技术的安全数据检索方案

本文提出了一种利用属性基加密(ABE)技术的安全数据检索方案。首先,利用ABE提供丰富的索引词表达能力,从而确保数据安全性;然后,通过平衡云服务提供商运行开销和其它用户参与基于云存储的信息检索服务;最后,使用加密运算替代穷尽搜索,使得搜索过程与现存数据库管理系统机制更加兼容。分析结果表明,相比其他几种较新的方案,本文方案在访问控制和快速搜索中具有更好的性能,且能在数据检索过程中确保数据安全性和用户隐私,适合应用于具有大量数据的云存储系统。     

基于视觉定位的机器人智能拆垛系统

针对传统示教再现机器人仅能进行位置确定、轨迹固定的拆垛任务,局限于固定场景的问题,设计了一个基于视觉定位的机器人智能拆垛系统.该系统利用目标像素中心坐标转换求得对应世界坐标.针对眼在手外的安装相机方式,导致目标经图像处理算法求得的旋转角度可能由于相机自身的偏转而产生误差的问题,提出利用相机外参系数补偿目标旋转角度.最后设计拆垛策略,通信引导机器人以由近及远的抓取顺序执行拆垛任务,并无需人工干预自动完成整垛拆卸.经过实验数据表明,该系统可在未知工作场景中对未知位置目标进行抓取,位置误差可达1.1 mm,角度误差可达1.2°,堆垛一层定位时间为1.2 s左右,满足工业场景中对拆垛机器人的精度与效率需求.