• 한국정밀공학회지
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• 제15권7호
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• pp.52-60
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• 1998

In optical disc system, 4-wire actuator has undesired tilt which degenerates the performance of RF signal. This tilt occurs from moment around the axis parallel to the tangential direction of the disk. The main reason of the moment is the coupling effect between focus driving system and tracking driving system. This paper constructed tilt mechanism and analyzed tilt quantity due to the moment based on structural analysis and magnetic field analysis. And the experiment about tilt was executed. The results were compared and discussed about the difference. Then, the design method for reducing tilt angle was suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3123-3125
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• 1999

광기록 저장매체의 기록밀도가 더욱 올라가면서 현재 콤팩트디스크나 DVD(Digital Versatile Disc)에 사용되고 있는 d=2인 코드보다는 검출성능이 좋은 d=1인 코드에 대한 관심이 점점 높아지고 있다. 광기록 저장매체에 사용할 수 있는 코드가 갖추어야할 중요한 제한조건으로는 코드열의 전력밀도가 저주파에서 충분히 억압될 수 있어야 한다는 것이다. 광자기디스크나 하드디스크에서 사용된 적이 있는 (1.7)코드는 코드자체로서 DC억압능력을 갖고있지 않다. DC를 억압시키기 위해 보통 부가비트를 일정간격으로 삽입하거나 싱크를 이용하게 되는데 이와 같은 방법으로는 충분한 DC억압이 어렵거나 기록밀도를 올리는데 불리한 원인이 된다. 본 논문에서는 코드열 자체로서 DC억압능력을 갖고 있는 코드워드의 생성방식과 변조 알고리즘을 RLL(1,8)인 경우를 예로 제시하였다. 또한 본 논문에서 제시한 코드의 성능에 대한 검증으로 기존의 RLL(1,8)코드(1)와 본 논문에서 제시한 코드에 4%이하의 부가비트를 삽입하여 DC억압을 수행한 뒤 동일한 기록밀도에서 DC억압성능을 비교하였을 때 저주파 대역에서 $1^{\sim}5dB$이상의 개선효과가 있었음을 확인하였다.

• 전자공학회논문지T
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• 제36T권2호
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• pp.32-41
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• 1999

CD(Compact Disc) 호환성을 가지는 고밀도 재생전용 및 기록재생용 DVD(Digital Video Disc) 기기의 광학픽업 2중 엑츄에이터 구조를 콤팩트하게 할 수 있는 단일 엑츄에이터 설계법을 제시한다. 설계된 엑츄에이터는 가동부에 CD용 대물렌즈와 DVD용 대물렌즈를 함께 장착하고, 사용 디스크에 따라 가동부를 축주위로 회전시켜서 대물렌즈를 전환하는 축습동형 구조를 하고, 자기 스프링에 의하여 부동된다. 감쇠방식으로서는 가동부와 축사이의 쿨롱마찰을 이용하고, 가동부는 유한요소법(FEM)을 통해, 서보대역내에서 2차 진동모드가 발생하지 않도록 한다. 본 논문의 설계법을 검증하기 위하여 시제품을 제작하고, 동특성을 측정, 평가한다.

• 대한기계학회논문집A
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• 제26권5호
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• pp.952-959
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• 2002

The natural frequencies of a flexible spinning disk misaligned with the axis of rotation are studied in an analytic manner. The effects of misalignment on the natural frequency need to be investigated, because the misalignment between the axis of symmetry and the axis of relation cannot be avoided in the removable disks such as CD-R, CD-RW or DVD disks. Assuming that the in -plane displacements are in steady state and the out-of-plane displacement is in dynamic state, the equations of motion are derived for the misaligned spinning disk. After the exact solutions are obtained fur the steady -state in-plane displacements, they are plugged into the equation for the dynamic-state out-of-plane motion. The resultant equation is a linear equation for the out -of-plane displacement, which is discretized by the Galerkin method. Based on the discretized dquations, the effects of the misalignment are analyzed on the vibration characteristics of the spinning disk, i.e., the natural frequencies and the critical speed.

• 한국멀티미디어학회논문지
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• 제8권10호
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• pp.1383-1390
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• 2005

모바일 멀티미디어 저장 서버는 동시에 다수의 개인용 이동 단말기(PDA)에서 요청하는 데이터를 실시간으로 저장 및 전송을 해야 한다. 그러나, 대역폭이 작은 모바일 인터넷 환경에서 다수의 개인용 이동 단말기가 동시에 서버로 접속하게 되면 병목(BottleNeck) 현상이 발생할 수 있다. 본 논문에서는 카메라가 장착된 개인용 이동 단말기에서 실시간으로 캡쳐(capture)한 영상을 모바일 변환 저장서버에서 저장 및 전송을 할 때 모바일 멀티미디어 저장 서버에서 발생할 수 있는 병목 현상을 효율적으로 해결할 수 있는 새로운 방법으로 가중치 기반의 동적 가변 디스크 스케줄링을 제안하고, 기존 방법들과 비교를 통해서 제안한 방법의 우수한 성능을 증명한다.

• 대한기계학회논문집A
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• 제26권9호
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• pp.1905-1913
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• 2002

Using the finite element method, this study investigates the dynamic time responses of a flexible spinning disk of which axis of rotation is misaligned with the axis of symmetry. The misalignment between the axes of symmetry and rotation is one of the major vibration sources in optical disk drives such as CD-ROM, CD-R, CD-RW and DVD drives. Based upon the Kirchhoff plate theory and the von-Karman strain theory, three coupled equations of motion for the misaligned disk are obtained: two of the equations are for the in-plane motion while the other is for the out-of-plane motion. After transforming these equations into two weak forms for the in-plane and out-of-plane motions, the weak forms are discretized by using newly defined annular sector finite elements. Applying the generalized-$\alpha$ time integration method to the discretized equations, the time responses and the displacement distributions are computed and then the effects of the misalign ment on the responses and the distributions are analyzed. The computation results show that the misalignment has an influence on the magnitudes of the in-plane displacements and it results in the amplitude modulation or the beat phenomenon in the time responses of the out-of-plane displacement.

• 한국소음진동공학회논문집
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• 제15권10호
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• pp.1148-1159
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• 2005

In this paper, the various uncertainties generated in an optical disk drive (ODD) and the robust servo designs considering the uncertainties are studied. First, the brief introduction an ODD and the servo error tolerance of it are discussed. Then, the classifications of uncertainty and the concept of relative stability are introduced. Considering the uncertainty of an ODD, two robust control approaches are applied: (i) mixed sensitivity approach in H$\infty$ control theory for unstructured uncertainty, (ii) QFT for structured uncertainty Finally, the designed controllers are realized by DSP, and these controllers are applied to a commercial DVD-ROM drive. From these experiments, we prove that the designed robust controllers have more good disturbance rejection performance and robustness when it is compared to the conventional lead-lag controller.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.817-825
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• 2001

The natural frequencies of a flexible spinning disk misaligned with the axis of rotation are studied in an analytic manner. The effects of misalignment on the natural frequency need to be investigated, because the misalignment between the axis of symmetry and the axis of rotation cannot be avoided in the removable disks such as CD-R, CD-RW or DVD disks. Assuming that the in-plane displacements are in steady state and the out-of-plane displacement is in dynamic state, the equations of motion are derived for the misaligned spinning disk. After the exact solutions are obtained for the steady-state in-plane displacements, they are plugged into the equation for the dynamic-state out-of-plane motion. The resultant equation is a linear equation for the out-of-plane displacement, which is discretized by the Galerkin method. Based on the discretized equations, the effects of the misalignment are analyzed on the vibration characteristics of the spinning disk, i.e., the natural frequencies and the critical speed

• 소음진동
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• 제9권2호
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• pp.324-330
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• 1999

With the increase of track density, high rotational speed and the compatibility for various media such as CD-ROM, CD-R/RW, DVD-ROM/RAM/RW etc. in optical disk drive, the effective anti-vibration design is so crucial for robust operaton. Especailly when the drive is self-excited by unbalanced disk, internal sled base vibration and its external transmission to the case bring about so severe problem. Generally these two consideration points the practical anti-vibration design process to control thses two conflictive properties using finite element analysis. As an example of the design process, Duro 25 and 40 visco-elastic rubber mount was selected and analyzed. The stiffness obtained from FEM rubber model was well matched with the experiments. Also it was confirmed that the internal and external vibration induced from unbalanced disk have good agreement with experimental results. The proposed design process is adopted to the slim-type optical disk drive.

• 한국소음진동공학회논문집
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• 제16권1호
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• pp.40-49
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• 2006

A novel disturbance measurement method, model based disturbance observer (MBDO) for optical disk drives (ODDs), is proposed and the disturbance analysis using the proposed method is performed under various conditions. In ODDs, the quantitative and qualitative analysis for the generated disturbance during normal operation is very important to successful servo loop design. However, the disturbance measurement is difficult, and high precision measurement is necessary. Furthermore, the conventional disturbance measurement method using a LDV (laser Doppler vibrometer) has many difficulties in eccentricity direction due to the vertical movement of an optical disk. To solve this problem, the MBDO is proposed. First, the relationship between the servo loop for ODDs and the generated disturbance are briefly reviewed. Second, the principle of the MBDO is introduced, and the disturbance measurement results, which are measured by the MBDO and a LDV, are compared. In these experiments, test DVD-ROM disks are used to generate quantitative/qualitative disturbance. Then, the disturbance analysis under various conditions is performed using waterfall technique. This technique clearly shows the disturbance trend from the inner part of an optical disk to the outer part of it. Finally, the various disturbances measurement results are summarized and some remarks for it are commented.