• Title/Summary/Keyword: 트랙추종서보

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Design and Implementation of Periodic Disturbance Compensators for Track Following Servo Systems (트랙 추종 서보 시스템에 대한 주기적 외란 보상기의 이득 설정과 구현)

  • Jeong, Jun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.2
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    • pp.139-145
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    • 2014
  • Periodic disturbance compensators are widely used in track following servo systems. They are commonly designed and implemented by adaptive feedforward compensators or internal model based compensators. In track following servo systems, the gains of the compensators should be determined considering the change of the sensitivity transfer function and the implementation methods should be selected considering the system environment. This paper proposes a guide for determining gains of the periodic disturbance compensators. Various simulation and experimental results are presented to see the effect of gains. In addition, this paper introduces the various types of implementation methods and compares their merits and demerits.

Repeatable Run-out Reduction by Servo Track Writing in Semi-vacuum Condition for Ultra-high TPI Disk Drive (초고밀도 디스크 드라이브를 위한 반 진공 작동 환경에서 서보 트랙 기록 방법에 의한 RRO 저감에 대한 연구)

  • 한윤식;강심우
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.11
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    • pp.1176-1181
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    • 2004
  • In high-capacity disk drives with ever-growing track density, the allowable level of position error signal(PES) is becoming smaller and smaller. In order to achieve the high TPI(track per inch) disk drive, it is necessary to improve the writing accuracy during the servo track writing(STW) Process through the reduction of track mis-registration sources. Among the main contributors of the non-repeatable runout(NRRO) PES, the disk vibration and the head-stack assembly vibration is considered to be one of the most significant factors. Also the most contributors of repeatable runout(RRO) come from the contributors of NRRO which is written-in at the time of STW process. In this paper, the effect of NRRO on servo written-in RRO is Investigated by experimentally, and the experimental result shows that the written-in RRO can be effectively reduced through a STW process under low dense medium condition such as semi-vacuum.

Improvement of Tracking Servo Performance in SIL based Near-field Recording using Disturbance Observer (외란 관측기를 이용한 근접장 기록 시스템의 트랙킹 서보 성능 향상)

  • Kang, Min-Seok;Kim, Joong-Gon;Shin, Won-Ho;Jeong, Jun;Park, No-Cheol;Yang, Hyun-Seok;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.609-612
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    • 2008
  • The solid immersion lens (SIL) based near-field recording (NFR) system is considered as one of the high density optical data storage system. For the NFR servo system, tracking servo control is a difficult technology to maintain extremely small gap between SIL and media within one twentieth. This is because the track pitch is decreased for increasing the recording density. In this paper, we propose disturbance observer (DOB) and internal model principle (IMP) for disturbance rejection due to eccentricity of disk. The performance of tracking controller using DOB is increased by about 85%, 94%, 97% using Q filters that have bandwidths of 50Hz, 125Hz, 250Hz, respectively. Moreover, IMP based controller is effectively reduced the residual error.

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Repetitive Control for the Track-Following Servo System of an Optical Disk Drive (광 디스크 드라이브의 트랙 추종 서보 시스템을 위한 반복 제어)

  • 문정호;이문노;정명진
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.1
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    • pp.39-46
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    • 1999
  • Disturbances acting on the track-following servo system of an optical disk drive inherently contain significant periodic components that cause tracking errors of a periodic nature. Such disturbances can be effectively rejected by employing a repetitive controller, which must be implemented carefully in consideration of system stability. Plant uncertainty makes it difficult to design a repetitive controller that will improve tracking performance yet preserve system stability. In this paper, we examine the problem of designing a repetitive controller for an optical disk drive track-following servo system with uncertain plant coefficients. We propose a graphical design technique based on the frequency domain analysis of linear interval systems. This design method results in a repetitive controller that will maintain system stability against all admissible plant uncertainties. We show simulation and experimental results to verify the validity of the proposed design method.

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An Improved Tracking Servo System in Optical Disk Drives (광디스크 드라이브의 개선된 트래킹 서보 시스템)

  • Lee, Tae-Gyu;Jeong, Dong-Seul;Chung, Chung-Choo
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.44 no.4 s.316
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    • pp.67-73
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    • 2007
  • An optical pick up generally has coupled dynamics between focusing and tracking servos. The coupled dynamics reduces tracking performance of optical disk drives. A conventional control method is holding the previous tracking control command in the presence of surface defect. The method has a long settling time. If the defective area is getting larger, objective lens will get away from the following track. In order to overcome this problem, this paper proposed a new control method for optical disk drives based on a prediction of tracking error and focusing error. We present how to compensate the coupled dynamics so that reduced setting time is achieved. It is verified by experiments that the proposed method brings an improved performance in the presence of surface defect as well as in the normal operating condition.

Repetitive Control for Track-Following Servo of an Optical Disk Drive Using Linear Matrix Inequalities (선형 행렬 부등식을 이용한 광 디스크 드라이브의 트랙 추종 서보를 위한 반복 제어)

  • 도태용;문정호
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.2
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    • pp.117-123
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    • 2003
  • Rotational machines such as optical disk drives, hard disk drives, and so on are subject to periodic disturbances caused by their mechanical characteristics. In the meanwhile, it is well known that repetitive control rejects periodic disturbance effectively. This paper presents a practical application of repetitive control to the track-following servo of an optical disk drive. The repetitive control system is composed of two repetitive controllers which compensate for periodic disturbances generated by track geometry and eccentric rotation of disk and a feedback controller stabilizing the feedback loop. A robust stability for all plant uncertainties is proved using linear matrix inequalities (LMIs). In the controller design, a weighting function is introduced for the feedback controller to ensure a minimum loop gain and a sufficient phase margin. The repetitive controllers and the feedback controller are designed by solving an optimization problem which can consider the robust stability condition and the system performance. The developed repetitive control system is implemented in the digital control system with a 16-bit fixed-point digital signal processor (DSP). Through simulation and experiment. The feasibility of the proposed repetitive control system is verified.