• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1280-1283
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• 2007

본 연구는 홀로그래픽 정보저장기기에서 트래킹 서보 제어를 통해 원하는 데이터를 정확하게 기록 및 재생하기 위한 LQG 제어기를 제안하고 검증하는 것을 목적으로 한다. 서보광이라는 추가적인 광을 사용할 것을 제안하여, 서보광과 참조광 간의 간섭에 의해 기록매체에 서보 신호를 얻을 수 있게 하는 홀로그램을 형성한다. 기록 및 재생과정에서 신호광이 기록, 재생됨과 동시에 서보광에 의한 서보 신호가 재생되고, 그 신호의 경로에 설치된 포토 다이오드로부터 디스크 형태에서 발생 할 수 있는 외란을 감지하게 된다. 감지된 외란 신호인 트래킹 에러 신호를 통해 참조광이 디스크의 정확한 위치에 조사되게 하기 위해 평판유리 액츄에이터를 사용한다. 이와 같은 서보 제어를 수행했을 경우 데이터 페이지가 정확하게 재생되며 SNR 과 BER 이 개선되는 것을 확인할 수 있다.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.431-432
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.837-842
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• 2007

Information storage devices using disks have a disk vibration at the frequency which is equivalent to the disk rotational speed. They also have a track vibration due to the disk eccentricity at the same frequency. In near field recording systems, the former affects the air-gap servo and the latter affects the tracking servo. In this paper, we introduce a novel control algorithm based on the internal model principle to both servos. A controller block designed by the principle is connected to the base lead-lag type compensator in parallel in order to cancel the repeatable run-out due to the disk vibration or eccentricity. Simulation and practical application of the algorithm on a near field recording system show good servo performance.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2299-2301
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• 2001

광 디스크의 용량을 증가시기키 위해선, 레이저 다이오드의 단파장화와 렌즈의 개구수 증가가 수년 동안 시도되어왔다. 불행히도 이러한 노력들은 디스크 틸트(tilt)로 인해 야기되는 코마(coma) 수차로 인한 부작용을 유발하였다. 이런 문제를 해결하기 위해, 램(random access memory, RAM) 디스크의 경우 몇 가지 검출과 보상 방법이 제안되었다. 그러나, 롬(read only memory, ROM) 디스크의 경우 아직까지 뚜렷한 해결책이 제시되지 않고 있다. 본 논문에서는 8분할 광 검출기에 의해 생성되는 차동 위상 검출(differential phase detection, DPD) 신호를 이용한 고밀도 롬 디스크에서 래디얼(radial) 틸트를 검출하는 방법을 제안한다. 3축 렌즈 구동형 액츄에이터(actuator)를 이용하여 개발한 래디얼 틸트 서보로 검출된 래디얼 틸트를 보상한다. 액츄에이터의 회전이 트래킹(tracking) 서보(servo)에 미치는 영향을 소개한다. 끝으로 제안된 방법의 유용성을 고밀도 롬 드라이브에 대한 실험을 통해 검증한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.539-546
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• 2007

Information storage devices using disks have a disk vibration at the frequency which is equivalent to the disk rotational speed. They also have a track vibration due to the disk eccentricity at the same frequency. In near field recording systems, the former affects the air-gap servo and the latter affects the tracking servo. In this paper, we introduce a novel control algorithm based on the internal model principle to both servos. A controller block designed by the principle is connected to the base lead-lag type compensator in parallel in order to cancel the repeatable run-out due to the disk vibration or eccentricity. Simulation and practical application of the algorithm on a near field recording system show good servo performance.

• Journal of Korea Multimedia Society
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• v.5 no.2
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• pp.215-221
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• 2002

In high speed optical disc devices, the vibration caused by unbalanced displacement leads the focus and tracking servo systems to be unstable, and increases the data search time. In this paper, we propose a new scheme to solve the unbalanced displacement problem. The proposed method detects the unbalanced rate by differential amplifying optical power received at photo diode and converts it into an electrical signal. controlling the speed of spindle motor, according to the detected unbalanced rate, makes it possible to improve the performance of tracking and data searching tasks. Also, we analyze the dynamic characteristics of focus and tracking servo systems in high speed mode and provide the firmware and hardware architecture that the proposed method can be installed as an add-on- module in the existing system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.894-899
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• 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.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.137-139
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• 2007

In optical disk drives, a conventional control method in the presence of surface defect is holding the previous tracking control command. It is known that the method has a long settling time. This paper proposes a new control method which reduces the settling time. An optical head generally has coupled dynamics between focusing and tracking servo system. We present how to compensate the coupled dynamics so that reduced settling 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.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.32-41
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• 2008

In this paper, we describe the synthesis of robust and non-fragile $H^{\infty}$ state feedback controllers for linear systems with affine parameter uncertain tracking servo system of blu-ray disc drive, as well as static state feedback controller with polytopic uncertainty Similarity any other control system, the objective of the track-following system design for optical disc drives is to construct the system with better performance and robustness against modeling uncertainties and various disturbances. Also, the obtained condition can be rewritten as parameterized linear matrix inequalities(PLMIs), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. We show that the resulting controller guarantees the asymptotic stability and disturbance attenuation of the closed loop system in spite of controller gain variations within a resulted polytopic region.