• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.675-677
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• 2004

This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, dead-zone nonlinear element is used for nonlinear controller and PID control method is used for linear controller. Although this strategy improves anti-shock performance, it has a narrow stability bound. In this paper, we propose dead-zone with saturation nonlinear element for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher gain of dead-zone than the controller with dead-zone only. In the linear controller design, we show that lead-lag control has improved stability margin over PID control. Numerical simulation results show that the proposed method can get better performance to the external shock than previously proposed method.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.738-740
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• 2004

The disturbance observer is effective in enhancing the performance of position control in high speed optical disk drive systems(ODDS). It is known that error based modified disturbance observer (EM-DOB) is more effective structure than general DOB. It has a simple structure and realization, but it loses robustness. We propose a dual modified disturbance observer(Dual mDOB). It consists of internal loop EM-DOB and external loop DOB. Those loops are designed for different objects. We see that the dual mDOB is an effective method for tracking performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.541-546
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• 2005

In this paper, the various uncertainties, which are generated in working of an optical disk drive, are discussed in details and the robust servo design considering the uncertainties are discussed. First, the classification of the uncertainties and the modeling process including that are treated. Then, the robust servo designs using QFT and $H_{\infty}$ theory are performed. Finally, the designed servo loops realized by DSP are applied to the real system. From these experiments, we proved that the robust servo design using QFT and $H_{\infty}$ have a good performance and a good robust stability when it compared with the conventional servo loop.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.7
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• pp.637-643
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• 2006

Generally, the tracking performance of optical disk drive(ODD) system can be improved using a disturbance observer(DOB). However, a DOB is not easily applied in an ODD system because an additional microprocessor, such as a digital signal processor(DSP), is needed. This paper shows how a DOB system can be replaced by the error-based modified disturbance observer(EM-DOB) when two mathematical conditions are satisfied. Due to the simplified structure of EM-DOB, the algorithm is easily implemented as an analog circuit, which is suitable for the ODD servo system. Additionally, in these algorithms, disturbances rejection performances can be tuned as Q filter parameters. Similar to a DOB system, three design guidelines of a Q filter can be applied. Experimental results of DOB and EM-DOB are evaluated under forced disturbances.

• 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 Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.173-176
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• 2004

Nowadays, mobile devices are very common equipments such as mobile phone, PDA, etc. These equipments need information storage devices. Optical storage devices have more advantages than other storage devices, but it is not free from shock situation like dropping by user's mistakes. A complete model of a Small Form Factor Optical(SFFO) disk drive subject to shock loads is developed to investigate the response of the pickup/disk interface. With this model, we can simulate the drop test and consider the matters of shock simulation using commercial software(Ansys/LS-Dyna).

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.440-445
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• 2000

Robust tracking controller of optical disk drive(ODD) is designed using quantitative feedback theory(QFT). Nominal plant model is identified from real system through modal test. Uncertainties and control performance of tracking servo are specified, and robust controller satisfying these specifications is designed in the QFT framework. To verify the performances of designed controller, experiment are performed in a digital signal processor(DSP) environment, and experimental results are compared with simulations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.381-386
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• 2002

This paper presents a piezoelectric shunt methodology to reduce unwanted vibration of optical disk drive(O.D.D.). After briefly investigating a second-order mechanical vibration absorber model, the O.D.D. structure is incorporated with the piezoelectric shunt circuit. In order to evaluate feasibility of multi-mode passive damping of the structure, admittance measurement of piezoceramic is undertaken. The parameters are optimally tuned by admittance measurement results on the basis of the circuit model and displacement transmissibility is evaluated. To verify validity of admittance measurement result, experiment is performed and vibration reduction is achieved at two different modes.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.6
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• pp.372-375
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• 2005

The tracking performance of optical disk drive(ODD) system can be improved using disturbance observer(DOB). But, DOB was not easily applied in the ODD system because the additional microprocessor was needed. In this paper, we propose an error-based modified disturbance observer(EM-DOB) for ODD system. Due to the simplified structure of EM-DOB, the system is easily implemented to the digital control algorithm or the analog circuit. In these algorithms, disturbances rejection performance of system can be tuned as Q filter parameters are selected. Based on analysis of sensitivity function, three guidelines of Q filter design are suggested. Experimental results of DOB and EM-DOB are evaluated under the forced disturbances.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.972-976
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• 2001

This paper presents a piezoelectric shunt methodology to reduce unwanted vibration of optical disk drive(O.D.D.). After briefly investigating a second-order mechanical vibration absorber model, the O.D.D. structure is incorporated with the piezoelectric shunt circuit. In order to identify modal parameter of the structure, a finite element analysis is undertaken. The parameters are optimally tuned on the basis of the circuit model. The displacement transmissibility is evaluated and compared with various resistance values.