A median peak detecting analog signal processor for hard disk driveservo

An analog signal processor for hard disk drive servo is described. It performs servo demodulation by means of median peak defection which provides immunity against additive as well as multiplicative noise from the medium, unlike conventional methods. A novel circuit configuration has been employed to implement the median peak detector in an area and power efficient manner. The entire servo processor that includes the demodulator and 10 b A/D and D/A converters has been integrated into a single CMOS integrated circuit     

某导弹随动系统改进设计

介绍了一种导弹随动系统,分析了该随动系统精度调试中驱动信号的生成和离轴信号的解调问题,以及由该困难导致的随动精度不足。随后提出了一种改进方法,通过在随动控制回路中增加一级反馈控制,实现随动误差的动态调整,即增大了随动精度又简化了调试过程。     

利用锁相环跟踪马达转速在微硬盘伺服写入中的应用

在众多与硬盘相关的技术中,硬盘伺服信息写入技术非常重要。在硬盘伺服信息写入的过程中要求磁碟转速要非常稳定。通过对硬盘主轴马达的反电动势与马达转速之间关系的分析,提出一种利用马达的反电动势信号跟踪马达转动速度变化,产生系统伺服写入时钟信号的方法。在此基础上建立适合的锁相环模型,根据实际情况选择参数并进行计算仿真。     

Direct demodulation of a 10.6µm FM signal with an NH2D stark cell

A new technique for direct demodulation of a 10.6-μm FM signal using a Stark absorption cell is described. A Stark tunable absorption line in NH2D is used to track the time-varying frequency of the incoming FM laser signal using a closed servo loop. The demodulated FM signal is proportional to the feedback voltage applied to the Stark cell. Demodulation at frequencies up to 5 kHz has been demonstrated, the rate being limited only by the bandwidth of the available servo electronics.     

Robust tracking servo system considering force disturbance for the optical disk recording system

This paper proposes a new robust tracking servo system for the optical disk recording system with feedforward controller based on the prediction of the tracking error. In optical recording systems, the feedback servo system must suppress the influence of force disturbance and parameter variation. To overcome this problem, this paper designs the robust feedback control system by using coprime factorization and disturbance observer. The detecting signal of the optical disk recording system is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both the "zero-phase-error tracking" control theory and the prediction of the 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.     

High-bandwidth high-accuracy rotary microactuators for magnetichard disk drive tracking servos

Reports on the design, fabrication, and testing of an electrostatic microactuator for a magnetic hard disk drive (HDD) tracking servo. The design requirements for a microactuator are investigated. These include high Z-directional stiffness, low in-plane stiffness, high structural aspect ratio, large output force, high area efficiency, low cost, and mass batch production. An area-efficient rotary microactuator design was devised, and microactuators were successfully fabricated using innovative processing technologies. The microactuator has a structural thickness of 40 μm with a minimum gap/structure width of approximately 2 μm. Its frequency response was measured and it was determined that it can be modeled as a second-order linear system, up to the 26-kHz frequency range. Moreover, the microactuator will enable the design of a servo system that exceeds a 5-kHz servo bandwidth, which is adequate to achieve a track density of more than 25 kilotrack per inch (kTPI). The microactuator/slider assembly was also tested on a spinning disk, with its position controlled by a PID controller using the magnetic position error signal written on the disk. An accuracy of about 0.05 μm was observed when the servo controller was turned on. Continuous-time dual-stage servos were designed and simulated using the μ-synthesis technique. A sequentially designed SISO and a MIMO control design method have been shown to be capable of meeting prescribed uncertainty and performance specifications     

小型光盘调焦系统

介绍了一套用于光盘存储的小型调焦伺服系统,调焦误差校正比优于70 dB。     

Optimal demodulation of digital signal under additive influence of similar powerful interference

Analysis of achievements in the sphere of digital signal processing in application to the conditions when useful digital signal, white noise and interfering digital signal similar to the useful one, which significantly exceeds the latter in simultaneous power, are present in the communications channel is performed. It is shown that under such conditions highly effective processing of useful signal is possible and the potential interference immunity of the useful signal demodulation is equal to the interference immunity in the channel with the white noise only, i.e. in the absence of the interfering signal.     

Controller optimization for minimum position error signals of harddisk drives

In order to reduce the position error signal (PES) and track misregistration (TMR) of disk drives, it is generally believed that the bandwidth of a disk drive servo system has to be increased. However, increase of the bandwidth is limited by available sampling frequency and mechanical resonances of a head-disk assembly. Hence, for a given servo-mechanical system, optimization of a servo controller is a crucial and economical way to get the best TMR performance. In this paper, optimization of a servo controller that yields minimum PES is presented. The equivalent position-mode disturbance is estimated by the error transfer function inversion method. The estimated disturbance is injected into the servo system to evaluate PES. The optimization process will select the best controller that minimizes PES under the specified constraints. It has been demonstrated that the minimization has been achieved by shaping the error transfer function rather than increase of the servo bandwidth, PES reduction has been confirmed by simulation and experiments     

采样伺服格式光盘中摆结构的最佳选择

本文简要分析了采样伺服光盘的特点,讨论了不同摆结构对径向误差信号的影响,从而提出了能获得最大跟踪伺服信号增益的摆结构。     

Two-degree-of-freedom control with robust feedback control for harddisk servo systems

A two-degree-of freedom (2 DOF) control structure is proposed for read/write head servo systems of hard disk drives (HDDs). This structure is applied to both track seeking and track following, and makes mode switches found in conventional HDD servo systems unnecessary. Two innovative features introduced in the paper are: 1) a new method for generating the reference signal for track seeking and 2) two robust feedback control schemes for rejection of disturbances; one scheme uses a disturbance observer (DOB), and the other uses adaptive robust control (ARC). Simulation results show that the 2 DOF structure with ARC provides better performance than either the conventional servo system with mode switches or the 2 DOF structure with DOB. Experimental results show the advantage of the new reference generation method and the use of the DOB-based robust controller     

Design and analysis of a high bandwidth disk drive servo systemusing an instrumented suspension

Resonance modes in the suspension of hard disk drives limit the closed-loop bandwidth. The bandwidth of the servo can be increased by active vibration control of the resonance modes. This paper considers the optimal placement of strain gauge sensors on a suspension to observe the vibration states of the suspension. Using a finite-element simulation of an actual suspension, a state-space model is identified for the two normal strains and the shear strain at each finite element. The state-space model includes the dynamics of the three primary resonance modes. A numerical search algorithm is used to determine the sensor location and orientation which maximizes the minimum singular value of the observability grammian. With the strain gauge output signal, a multirate inner loop controller is designed to be used with the existing head-positioning system. Simulations and analysis results suggest that use of an instrumented suspension is a viable candidate method for improved disk drive servo performance     

光刻伺服盘磁头读出信噪比分析

本文叙述了光刻伺服盘采用分离磁道刻写方法对信噪比的影响，该方法在磁盘记录区采用导磁材料，非记录区采用非导磁材料。这样一种非连续的记录磁介质，有利于道密度的提高，增大了磁盘信息存储容量，减少了道间串扰，提高了磁头读出的信噪比［以Ｓ／Ｎ表示］。     

模拟调制信号正交解调的抗载频失配性能分析

文章通过对模拟调制信号中两种典型的调制信号AM信号和FM信号进行数字正交解调的研究,探讨分析了该方法相较于相干解调所具有的较强抗载频失配能力,推导了AM、FM正交解调方法所允许的最大载频偏差△fmax,为实际应用提供了理论依据。     

Head-positioning control using resonant modes in hard disk drives

The best way to enhance the input/output (I/O) performance of a hard disk drive is by increasing the spindle speed. Therefore, the effect of windage vibrations caused by the airflow increases as the spindle speed increases. The servo bandwidth is limited by the primary resonant frequency of the mechanical system. However, the frequencies of the windage vibrations are higher than the primary resonant frequency. Accordingly, these frequencies are also above the servo bandwidth and are too high to be controlled by a conventional control system. In response to this problem, we have developed two methods for designing a servo control system that can suppress the windage vibrations. One method uses a stable mechanical resonant mode, and the other uses a stable resonant mode created by a digital filter. By using these methods, the head-positioning system can control the vibrations above the frequency of the primary resonant mode and the servo bandwidth. Application of these methods to actual hard disk drives showed that they can greatly decrease the windage vibrations, in which the peak frequency is about six times the open-loop gain 0-dB crossover frequency.     

A comparative study of the use of the generalized hold function for HDDs

This work is concerned with the application of H/sub /spl infin// control with the generalized hold function (GHF) to track-following control of hard disk drives (HDDs). In HDDs, the sampling frequency is limited primarily by the fact that a high sampling frequency tends to decrease the available data storage capacity of the devices, since the position error signal (PES) must be stored on the disk. Under such conditions, GHF provides a possible way to enhance servo performance without requiring more PES data. We investigate its possibility, comparing the results with other conventional H/sub /spl infin// control design results, including continuous/discrete-time and single/multirate control. Our results show that this controller has better performance due to the nature of the control input of the GHF.     

一种基于ASE光源的边缘滤波解调技术的研究

研究了一种利用放大自发辐射(ASE)光源线性段做边缘滤波器进行光纤Bragg光栅(FBG)解调的新方法,可实现在传感波长变化3 nm范围内的波长解调。系统采用了全光纤结构,无需机械部件调谐,提高了光纤传感系统的解调速度及稳定性,具有反应迅速快、性能价格比高等优点,应变测量范围可达2 500με。     

一种基于数字测频的PCM/DPSK解调方法

本文提出了一种新颖的PCM／DPSK数字信号解调方法。通过数字测频算法,获取PCM／DPSK信号频率突变点,根据DPSK调制原理,实现PCM／DPSK信号的解调。文中详细介绍了此种解调方法的基本原理及实现过程,分析了解调过程中多普勒频率对解调结果的影响。计算机仿真结果表明,此方法比相干解调性能优越,抗干扰能力强,便于软件编程及DSP器件实现,具有一定的应用价值。     

用SDFT实现FSK调制信号的数字解调方法

提出了一种新的FSK调制信号数字化解调的方法,该方法以移位离散傅立叶变换SDFT(Shifted Discrete Fourier Transforms)为基础。文中给出了一个8FSK信号进行数字化解调的仿真结果,计算机仿真结果表明,该方法能在较低信噪比(SNR)和较大多普勒频移条件下解调FSK信号,并具有较好的解调性能。     

RoFSO系统中4FSK仿真及其误比特率性能分析

将射频技术应用到自由空间光通信具有独到的优势。为了研究自由空间光载射频技术,在四进制频移键控调制解调理论基础上,以自由空间光通信为应用背景,采用仿真,从时域角度对四进制频移键控系统进行了编码及解码研究,并推导了经过高斯噪声和瑞利信道后系统误比特率及信道容量。两种解调法的系统误比特率仿真结果表明,当信噪比为12dB时,过零检测法的系统误比特率达到10-15,明显优于相干解调法。