Design of tracking servo control system for holographic data storage

Holographic data storage is a strong candidate for the next generation archive storage device. However, disturbances such as external shock, vibration, flutter and eccentricity of the disk affects the holographic data storage device. Thus, tracking servo control is necessary in order to enhance the signal noise ratio and reduce the bit error rate and retrieve the data accurately. It is also inevitable to face track overlapping problem if there is no datum to apply servo control during the recording process. In this research, we suggest a method forming a holographic servo track to detect the tracking error signal continuously without using any additional laser diode or pre-format layer. The tracking servo controller is designed to improve the track following performance, and the validity of the proposed method is confirmed through experiments on our holographic data storage system.     

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.     

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.     

Tracking servo method for holographic data storage using discrete pre-patterns

Page-oriented holographic data storage (HDS) is very sensitive to disturbances that affect the position of the recording medium. Accordingly, a more precise tracking servo is required for the recording process, and is also crucial for achieving high storage density. A compensation method is therefore essential for HDS recording. In this paper, we suggest some discrete pre-patterns for the tracking servo used in the recording process. This method is motivated by a tracking servo technique for a hard disk drive. Firstly, in designing the pattern shape, HDS characteristics are taken into account. Secondly, track error signals are analyzed. Thirdly, the discrete pre-pattern intervals are determined according to the track tolerance. Lastly, the feasibility of the new method is analyzed via simulations and experiments.     

Generation of fuzzy rules and learning algorithm for servo control in holographic data storage system

Today many media of information storage device are formed as disks. Hence, next generation removable data storage media are shaped as disk types too. The holographic data storage system also uses a disk type photopolymer media. And then, holographic data storage system is most advanced optical memory system. Tracking servo and tilt servo control are very important research in holographic data storage system. In this paper, we propose intelligent servo control by fuzzy rules in holographic data storage system. Hence, we have found pattern of tilt servo control in holographic data storage system through fuzzy system and genetic algorithm. Fuzzy rules were generated by genetic algorithm for controlling tilt servo. Therefore, we control tilt servo using fuzzy rules in holographic data storage system. Consequently, Image input–output patterns of tilt servo control was found by intelligence algorithm in holographic data storage system.     

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.     

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.     

An intelligent distortion-detection algorithm for restoring data in a holographic data storage system

In a holographic data storage system (HDSS), misalignment of the optical components causes data distortion, including barrel, pincushion, and rotation distortion. Because holographic data storage systems are very sensitive, misalignment inevitably results in data distortion. It is important to acquire accurate distortion-free data from a HDSS system. This paper proposes an intelligent distortion-detection algorithm for restoring data in HDSSs. We used a fuzzy system and subtractive clustering algorithm to generate fuzzy rules for the detection algorithm. The proposed algorithm determines a value indicating how distorted the data image is. Using this algorithm, it is possible to compensate for data distortion. A simulation performed well using barrel, pincushion and rotation images.     

阀控电液伺服压力脉冲实验自抗扰控制方法

针对压力脉冲疲劳测试系统在测试过程中工件体积的不确定性以及脉冲疲劳测试系统的机械与液压双动态耦合问题,首先,提出通过奇异值摄动理论将压力脉冲疲劳测试系统的多动态耦合进行解耦降阶;然后,利用自抗扰控制算法实现对系统模型降阶误差以及体积参数不确定性等干扰的补偿,保证测试系统输出的压力对指令信号的准确跟踪;最后,对基于降阶模型的自抗扰算法的稳定性和误差收敛性进行理论和定量分析,并对算法的可行性和有效性进行联合仿真和实验验证.研究结果表明,基于降阶模型的自抗扰控制算法对压力脉冲疲劳测试系统中工件体积参数的变化具有良好的鲁棒性且能够有效估计和补偿系统模型降阶误差等干扰,其跟踪性能相比于传统的PID控制器最大提升35.4%.     

一类多模块网格存储系统分散式控制方法

针对多模块网格存储系统中的多分拣点货物排列问题,提出一种解耦的分散式控制方法,将问题解耦为各存储模块的独立调度和模块之间的协调调度.模块内采用循环移动方式进行独立调度,模块间通过交换需求和模块状态控制协调过程.在不同参数条件下进行仿真实验,并与集中式控制方法进行对比仿真,结果表明分散式控制方法能够在各种工况下稳定有效地...     

随动控制系统下的齿轮螺旋线拟合方法研究

设计了随动控制型齿轮测量系统齿轮误差计算模型。利用随动控制系统作为测量齿轮螺旋线偏差的控制方式,以被测齿轮的螺旋线偏差为研究对象;对被测齿轮的实际螺旋线建立分析模型,对其跟踪轨迹进行螺旋线拟合,并实现螺旋线偏差的计算。本模型能够在简化系统运动控制方式和结构情况下,有效地测量齿轮螺旋线误差,并对建立的分析模型的准确性进行了验证。     

Iterative design method for an image filter to improve the bit error rate in holographic data storage systems

An image filter design method is proposed to improve the bit error rate (BER) in holographic data storage (HDS). In previous image restoration methods for HDS, a highly precise point spread function (PSF) was used as the deconvolution filter, so performance was strongly dependent on the accuracy of the PSF. In the proposed method, in contrast, the image filter is designed without using PSF information, due to the similar spatial frequency distributions of HDS data pages. A simple iteration algorithm was developed to obtain an optimized image-filter shape, and the performance of the designed image filter was verified by both simulation and experimentation. The experimental results demonstrated that the BER improved sixfold and greater than tenfold for a Nyquist factor of 1.1 and 1.2, respectively. Additionally, an improvement of >30 % in storage density was projected using the proposed filter, compared with conventional HDS systems.     

云存储服务中支持动态数据完整性检测方法

在云存储服务中,为了让用户可以验证存储在云存储服务器上数据的完整性,提出一种支持动态更新和公开验证的云存储数据完整性检测方法.通过引入双线性对和用户随机选择待检测数据块可以无限次验证数据完整性是否完好无损;可信第三方的引入解决了云用户与云存储供应商在数据完整性问题上产生的纠纷,实现数据完整性的公开验证;然后给出该方法的正确性、安全性以及性能分析,最后通过实验验证了该方法是高效可行的.     

Angle compensation of the reference beam in a retrieving process of the holographic data storage system

Holographic data storage system is one of a strong candidate of the next generation high capacity data storage system with a high storage density and a fast data transfer rate. The holographic data storage system uses two beams in a recording process and only a reference beam is used for retrieving stored data. With the angle multiplexing when the angle of the reference beam is deviated from its correct point, the diffraction efficiency of the corresponding data page is reduced and SNR is decreased. Therefore it is necessary to compensate the angle of the reference beam to reconstruct a good data page. To compensate the angle error, the angle of the reference beam is changed precisely within a specific range and stopped at the angle with the highest diffraction efficiency. By this method, in a retrieving process if there is a difference between the real angle of the reference beam and its correct angle, the error can be compensated and the best data page can be obtained.     

实时控制系统中数据的实时分片存储

为了在不影响实时控制系统响应时间的前提下实时地保存数据,提出了一种基于分片的数据实时存储方式.通过在实时控制系统中添加存储节点,在实时控制的过程中,实时节点将数据按时间分片,传给存储节点,存储节点采用分片存储的方式保存到存储系统中.这种方式只需要占用实时控制节点很少的控制周期时间,结合新增的存储节点完成对实时数据的存储,能在控制过程中实时读取分析数据.该方式应用于东方超环(EAST)等离子体控制系统上,能够较好的实现对长脉冲放电和未来的稳态放电实验数据进行实时的存储和读取分析,也能为其他实时控制系统的数据的实时存储提供借鉴.     

自适应环境的机器人视觉伺服控制方法

机器人和机器视觉的迅速发展,使得基于视觉的智能机器人得到更加广泛的应用。机器视觉提高了机器人控制系统对环境的适应程度,但其适应程度也受到周围环境对机器视觉算法的影响。针对这一情况,本文对机器人视觉伺服控制系统中的机器视觉算法进行了改进,提出了一种基于帧间差分法的自适应环境的机器人视觉伺服控制方法,从而提高了控制系统对环境的自适应程度,提高了对机器人控制的精确度,实验和理论分析证明,该方法具有较大的应用前景和实用价值。     

BLDC伺服系统控制系统建模与仿真

在分析了永磁无刷直流电机（BLDC）基本运行原理的基础上,建立了BLDC的数学模型,并在MATLAB7.1环境下搭建了伺服系统的双闭环控制系统仿真模型,实验结果表明,该模型在BLDC伺服系统的控制中性能稳定可靠,有较高的实用价值。     

考虑LuGre 摩擦的伺服系统自适应模糊控制

针对摩擦非线性的存在会使伺服系统控制精度难以提高的问题,建立了考虑动态LuGre摩擦的伺服系统数学模型,在系统参数和负载转矩未知的情况下设计了自适应模糊控制器,用自适应模糊逻辑系统在线逼近包含LuGre摩擦在内的非线性环节,从而实现了伺服系统高精度的位置跟踪。利用Lyapunov函数证明了闭环系统的稳定性。仿真结果表明,该控制器能有效地补偿摩擦非线性的影响,并对负载转矩变化具有较强的鲁棒性。     

体全息数据存储文件系统空间分配策略研究

通过分析体全息数据存储的物理寻址方式,提出了对逻辑块地址实行二维编址的策略。以二维逻辑块地址为基础,对体全息数据存储文件系统空间分配的连续性进行了研究,提出了“顺序连续”和“随机连续”的概念。对二维区域采用了四叉树结构进行组织,并以四叉树为基础设计了成组分配空闲块算法。在体全息数据存储文件系统原型系统的基础上,对模拟的全息存储体进行“文件级”的测试,结果证明二维分配策略能有效地提高文件数据块分配的连续性。