• Title/Summary/Keyword: Track Following Servo

Search Result 21, Processing Time 0.032 seconds

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
    • /
    • v.24 no.2
    • /
    • pp.139-145
    • /
    • 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.

Dual-Stage Servo System using Electrostatic Microactuator for Super-High Density HDD (정전형 마이크로 액추에이터를 이용한 초고밀도 HDD용 Dual-Stage 서보 시스템)

  • Kim, Seung-Han;Seong, U-Gyeong;Lee, Hyo-Jeong;Lee, Jong-Won;Choe, Jeong-Hun;An, Yeong-Jae;Jeon, Guk-Jin;Kim, Bong-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers C
    • /
    • v.48 no.2
    • /
    • pp.153-160
    • /
    • 1999
  • Dual-stage servo system for super-high density HDD has the chances of being composed of the coarse actuator(VCM) for track-seeking control and the fine actuator(microactuator) for-following control in near future. This paper presents the concept design of dual-stage servo system and the track-following control using an electrostatic microactuator for super-high density HDD. The electrostatic microactuator is designed and fabricated by MEMS(micro-electro-mechanical system) process. Both the nonlinear plant(voltage/displacement-to-electrostatic force) and the linear plant(electrostatic force-to-displacement) of the microactuator are established. Inverse function of the nonlinear plant is employed for a feedforward nonlinear compensator design. And feedforward control effect of this compensator is shown by time-domain experiments. A track-following feedback controller is designed using the feedback nonlinear compensator which is derived from the feedforward nonlinear compensator. The track-following control experiment is done to show the control efficiency of the proposed control system. And, excellent track-following control performance(2.21kHz servo-bandwidth, 7.51dB gain margin, $50.98^{\circ}$phase margin) is achieved by the proposed control system.

  • PDF

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
    • /
    • v.5 no.1
    • /
    • pp.39-46
    • /
    • 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.

  • PDF

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
    • /
    • v.9 no.2
    • /
    • pp.117-123
    • /
    • 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.

Pull-in Behavior Analysis in an Optical Disk Drive using Phase Plane and the Evaluations of Effecting Parameters for it (위상평면을 이용한 광디스크 트랙 끌어들임의 동적 해석 및 영향인자의 평가)

  • 최진영;박태욱;양현석;박노철;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.05a
    • /
    • pp.894-899
    • /
    • 2004
  • In this paper, the track pull-in behavior analyses in an optical disk drive (ODD) using plane phase is treated and the parameters affecting it are discussed. Track pull-in is the track capture procedure to do track following control and it is key factor to increase data transfer rate. Simulation method, Runge-Kutta method to solve nonlinear equation, is used to evaluate the track pull-in conditions, and the real servo loop parameters are applied in this process to get the more real condition. Finally, the comments for the acquired results are discussed briefly.

  • PDF

Enhanced Track Jump Stability in Optical Disc Drives (광디스크 드라이브에서의 트랙 점프 안정도 향상)

  • Ryoo, Jung-Rae;Doh, Tae-Yong
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.15 no.7
    • /
    • pp.683-687
    • /
    • 2009
  • Track jump control is a random access strategy for short distance movement. The most common track jump scheme is a bang-bang control of a kick and brake manner. In a conventional track jump scheme, a track-following compensator is turned off during kick and brake periods, and restarted at a target track for track pull-in. The inevitable controller switching with non-zero initial condition results in undesirable transient response, and excessive overshoot in the transient response causes track pull-in failure. In this paper, a new track jump scheme is proposed for enhancing track jump stability. Instead of control switching, internal states of a track-following controller are artificially manipulated for kick and brake actions in a digital control environment. Experimental results are provided in comparison with conventional track jumps.

Asymptotic Disturbance Rejection using a Disturbance Observer in the Track-Following Control System of a High-Speed Optical Disk Drive (고배속 광디스크 드라이브 트랙 추종 제어 시스템에서의 외란 관측기를 이용한 점근적 외란 제거)

  • 유정래;문정호;진경복;정명진
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.10 no.5
    • /
    • pp.402-410
    • /
    • 2004
  • To obtain a good tracking performance in an optical disk drive servo system, it is essential to attenuate periodic disturbances caused by eccentric rotation of the disk. As an effective control scheme for enhancing disturbance attenuation performance, disturbance observers (DOBs) have been successfully applied to the track-following servo system of optical disk drives. In disk drive systems, the improvement of data transfer rate has been achieved mainly by the increase of disk rotational speed, which leads to the increase of the disturbance frequency. Conventional DOBs are no longer effective in disk drive systems with a high-speed rotation mechanism because the performance of conventional DOBs is severely degraded as the disk rotational frequency increases. This paper proposes a new DOB structure for effective rejection of the disturbance in optical disk drives with a very high rotation speed. Asymptotic disturbance rejection is achieved by adopting a band-pass filter in the DOB structure, which is tuned based on the information on the disturbance frequency. In addition, performance sensitivity of the proposed DOB to changes in disk rotational frequency is analyzed. The effectiveness of the proposed DOB is verified through simulations and experiments using a DVD-ROM drive.

Design of a Gain Scheduling Controller to Improve Pull-in Performance in Optical Disc Drive (광디스크 드라이버의 풀인(pull-in) 성능향상을 위한 이득 스케줄링 제어기의 설계)

  • Kim, Eun-Hee;Oh, Jun-Ho
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.14 no.5
    • /
    • pp.462-466
    • /
    • 2008
  • This paper proposes a stable gain scheduling method of linear time invariant controllers for tracking servo system. In order to read and write the data on the optical disc, the pick-up head should be moved to the exact track quickly and follow the track immediately. Two different controllers are used for each moving and track-following. In pull-in period, a transition period from moving to track-following, the head might slip and miss the target track. This brings on another searching process and increases the total time. One way to avoid slipping is to extend the bandwidth of the track-following controller. But, extending the bandwidth could degrade the following performance. More prevalent way is to use one more controller in this pull-in period and switch to the following controller. In general, however, switching or scheduling of stable controllers cannot guarantee the stability. This paper suggests an scheduling method guaranteeing the overall stability not only in a generalized form but also in special form for SISO system. The sufficient condition is derived from the fact that Q factor of a stable controller should be stay in $RH_{\infty}$ space. In the experiment, the proposed method shows better performance than the switching method such as shorter time and lower current consumption.

A New Design of an ATF Block for DVCRs (DVCR용 ATF(Automatic Track Following) 블록의 새로운 설계)

  • Cho, Seong-Il;Kim, Sung-Wook;Ha, In-Joong;Kim, Jeong-Tae;Na, Il-Ju
    • Journal of the Korean Institute of Telematics and Electronics S
    • /
    • v.35S no.8
    • /
    • pp.106-112
    • /
    • 1998
  • Recently, the amount of image and audio data has been increasing dramatically for high performance. According to this trend, a high-density magnetic recording system is necessitated and the tracks of magnetic tapes are getting narrower. This, in turn, requires the capstan servo system of the magnetic recording system such as DVCR to control precisely the speed and position of the capstan motor. Especially, in case of play-back, the capstan servo system should be able to position and maintain the head on the desired place of the track. To meet this requirement, digital camcorders use ATF (Automatic Track Following). In this paper, a new ATF block using discrete Fourier transform is proposed. The proposed ATF block was designed and implemented in ALTERA FPGA chips and fully tested in a real DVCR system. It is shown through experiments that the new ATF block is more cost-effective than other existing ATF blocks using digital lowpass filters. In particular, the number of logic gates can be reduced by 20% in average, compared to the existing ATF's.

  • PDF

VCM Design to Improve Dynamic Performance of Actuator in a Disk Drive (하드 디스크 드라이브 엑추에이터의 동적성능향상을 위한 VCM 설계)

  • 이행수;강성우;김영훈;황태연
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2003.11a
    • /
    • pp.911-914
    • /
    • 2003
  • As high-capacity disk drives pow in track density, the allowable level of PES is becoming smaller. In this paper, some design concept of actuator is introduced to suppress the Butterfly mode that imposes the fundamental limitation on servo bandwidth. The effect of dynamics of proposed actuator on PES is examined by simulation.

  • PDF