• Journal of Institute of Control, Robotics and Systems
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• v.9 no.4
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• pp.284-295
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• 2003

The servo tracks of disk drives are constructed at the time of manufacture with the equipment of servo track writer. Because of the imperfection of servo track writer, disk vibrations and head fluctuations during servo track writing process, the constructed servo tracks might deviate from perfect circles and take eccentric shapes. The servo track writing error should be corrected because it might cause interference with adjacent tracks and irrecoverable operation error of disk drives. The servo track writing error is repeated every disk rotation and so is periodic time function. In this paper, we propose a new correction algorithm of servo track writing error based on iterative teaming approach. Our correction algorithm can learn iteratively the servo track writing error as accurately as is desired. Furthermore, our algorithm is robust to system model errors, is computationally simple, and has fast convergence rate. In order to demonstrate the generality and practical use of our work, we present the convergence analysis of our correction algorithm and some simulation results.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.129-130
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• 2007

Self servo track writing(SSTW)은 servo track writer(STW)를 이용하지 않고 hard disk drive의 내부 VCM을 이용하여 servo track을 기록하는 방식이다. SSTW는 이전 servo track을 상대적인 reference로 하여 기록하게 되므로 초기에 발생된 error와 외부의 disturbance의 영향으로 error는 급속하게 증가된다. 이것을 radial error propagation 이라 한다. 본 논문에서는 radial error propagation을 억제하기 위한 correction signal을 설계하고 servo writing 과정에서 발생하는 disturbance의 영향을 제거하기 위하여 disturbance observer(DOB)를 add-on type으로 구성하여 tracking 제어기를 설계하였다. 또한 DOB를 적용한 경우와 유사한 gain margin, phase margin과 sensitivity function을 갖는 제어기를 설계하여 그 성능을 비교하였다. 제안된 방식은 radial error propagation을 억제 하였을 뿐만 아니라 disturbance의 최소화하여 쓰여진 track의 DC track spacing과 AC track Squeeze가 개선된 것을 모의실험을 통하여 검증하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.736-741
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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 disk drive, it is necessary to improve the writing accuracy during the STW(servo track writing) process through the reduction of TMR sources. Among the main contributors of the NRRO(Non-Repeatable Run-out) PES, the disk vibration and the HSA(head-stack assembly) vibration is considered to be one of the most significant factors. Also the most contributors of RRO(Repeatable Run- out) come from the contributors of NRRO which is written-in at the time of STW(servo track writing) process. In this paper, the experimental test result shows that the effect of NRRO on servo written-in RRO effectively can be reduced through a STW process under low dense medium condition such as semi-vacuum.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.699-701
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• 2004

This paper proposes the algorithm of servo- writing based on feedback error learning neural networks. The controller consists of feedback controller using PID and feedforward controller using gaussian radial basis function network. Because the RBFNs are trained by on-line rule, the controller has adaptation capability. The performance of the proposed controller is compared to that of conventional PID controller. Proposed algorithm shows better performance than PID controller.

• 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.