Showing papers by "Hyunseok Yang published in 2005"

Repetitive controller design for minimum track misregistration in hard disk drives

Abstract: Repetitive control is a widely used technique for the compensation of repeatable error in systems that contain rotating mechanisms or repeat a trajectory. Generally, it includes delay chains and a low-pass filter in the positive feedback loop, which generate a periodic signal. The controller has typically been implemented in a plug-in fashion and designed heuristically with the simplest form of the filter. However, this design approach is somewhat ambiguous in the selection of controller parameters because of its influence over nonharmonic frequencies. Also, it leaves the possibility for further improvement. This paper presents an improved design method for the repetitive controller that provides minimum track misregistration (TMR) in a hard disk drive (HDD). For TMR prediction, the method identifies disturbances acting on an HDD and estimates servo performance, using the identification result. We have confirmed the identification and estimation procedure through experiments. In our method, first the basic tracking controller is designed and later the repetitive controller is designed in conjunction with a Q filter. A cost function based on Parseval's theorem, reflecting the servo performance as TMR, is defined. Then the servo performance is estimated from the identified disturbance, and the plant and designed controller's frequency response are modified as necessary by changing the parameters of the controller, whose optimization is carried out with a commercial nonlinear optimization tool. The design strategy facilitates the controller design by providing an accurate estimation for the attainable servo performance and design criteria under the optimization framework.

Coupled-Field-Analysis and Dynamic Improvement of Ultraslim Optical Pickup Actuator

Abstract: We propose coupled-field analysis that enables the precise analysis of the dynamic characteristics of optical pickup actuators. The effectiveness of the proposed method is confirmed by applying it to improve the performance of an ultraslim pickup actuator by some optimization methods. The redesigned actuator is evaluated in dynamic experiments.

Improvement of loading/unloading performance using control input position and considering disk vibration characteristics

Abstract: Loading/unloading (L/UL) dynamic characteristics are affected by various operating parameters, such as L/UL speed, disk speed, disk vibration, and so on. The effects of these parameters on L/UL performance are investigated experimentally using an acoustic emission (AE) sensor, an in-plane laser Doppler vibrometer (LDV), and a vertical LDV. The experimental data shows that during the loading of the slider, the contact probability is lower for low L/UL speeds. The frequencies of slider-disk contact are lower for low disk rpm during the loading process, whereas in the unloading process the contact probability is lower for high disk rpm. The effects of disk vibration on the L/UL process are also studied, and we have found that the relative gap and slider-disk velocity between the disk and ramp affect the contact events in the L/UL process. During 1000 unloading cycles, most noncontact events occurred near the region of the maximum ramp gap during the loading process. During unloading, most of the contacts between the slider and disk occurred at the minimum relative speed. Slider-disk contact rarely occurred at the maximum relative unloading speed. The noncontact region tends to expand with higher disk speeds during the unloading process. This paper proposes a method to control the unloading input position to improve L/UL performance. By controlling the unloading instant based on the disk vibration characteristics, we can significantly reduce the number of slider-disk contacts.

Design of swing arm type actuator and suspension for micro optical disk drive

Abstract: One of the trends on information storage device is focused on the development of micro-optical devices with optical flying head (OFH). Many different types of sliders for OFH and optical component systems have been introduced in the literature. However, the important issues on the mechanical system, which consists of suspension, swing arm and voice coil motor (VCM) part has not been discussed up to date. In this research, a swing arm type actuator with suspension for micro optical disk drive is designed and developed, basically focused on the mechanical issues, which should be solved for real application.

Design error corrector of binary data in holographic data storage system using fuzzy rules

Abstract: Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time. Today any data storage system cannot satisfy these conditions, however holographic data storage system can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System can be constructed without mechanical actuating part therefore fast data transfer rate and high storage capacity about 1Tb/cm 3 can be realized. In this paper, to reduce errors of binary data stored in holographic data storage system, a new method for bit error reduction is suggested. First, find cluster centers using subtractive clustering algorithm then reduce intensities of pixels around cluster centers and fuzzy rules. Therefore, By using this error reduction method following results are obtained; the effect of Inter Pixel Interference noise is decreased and the intensity profile of data page becomes uniform therefore the better data storage system can be constructed.

X - Y Galvano Mirror System for Fractal - Angle Multiplexing Hologram and Random Access Concept for It

Abstract: Fractal-angle multiplexing using x-y Galvano mirror and 1000 pages recording in a photorefractive crystal was performed. Then, a random seek concept using page count for a HDSS to improve the random seek performance is proposed.

Generation of fuzzy rules and learning algorithms for cooperative behavior of autonomouse mobile Robots(AMRs)

Abstract: Complex “lifelike” behaviors are composed of local interactions of individuals under fundamental rules of artificial life In this paper, fundamental rules for cooperative group behaviors, “flocking” and “arrangement” of multiple autonomouse mobile robots are represented by a small number of fuzzy rules Fuzzy rules in Sugeno type and their related parameters are automatically generated from clustering input-output data obtained from the algorithms for the group behaviors Simulations demonstrate the fuzzy rules successfully realize group intelligence of mobile robots

Generation of fuzzy rules and DNA coding method for cooperative behavior of autonomous mobile robots (AMRs)

Abstract: Complex "lifelike" behaviors are composed of local interactions of individuals under fundamental rules of artificial life. In this paper, fundamental rules for cooperative group behaviors, "flocking" and "arrangement" of multiple autonomouse mobile robots were represented by a small number of fuzzy rules by Subtractive clustering algorithm and DNA coding method. Fuzzy rules in Sugeno type and their related parameters were automatically generated from clustering inputoutput data obtained from the algorithms for the group behaviors. Simulations demonstrate the fuzzy rules successfully realize group intelligence of mobile robots.

Design and Comparison of Error Correctors Using Clustering in Holographic Data Storage System

Abstract: Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time in. Today any data storage system can not satisfy these conditions, but holographic data storage system can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System architecture without mechanical actuating part is possible, so fast data transfer rate and high storage capacity about 1Tb/cm3 can be realized. In this paper, to correct errors of binary data stored in holographic digital data storage system, find cluster centers using clustering algorithm and reduce intensities of pixels around centers. We archive the procedure by two algorithms of C-mean and subtractive clustering, and compare the results of the two algorithms. By using proper clustering algorithm, the intensity profile of data page will be uniform and the better data storage system can be realized.

Design of slider and suspension for 4 × 1 probe array type near-field scanning optical microscope

Abstract: Many information storage devices have been introduced and developed in recent years. The trend for these devices is toward high capacity, compact size, low power consumption, reliability, and removability for data interchange with other devices. In addressing these trends, the near-field scanning microscope (NSOM) technique is in the spotlight as the next generation device. In order for a near-field device to be successfully implemented in a system, a slider and suspension must be introduced as actuating mechanisms. Consequently, a suitable slider and suspension needed to be designed. The optical slider should be designed considering near-field optics with the probe structure. The suspension should function generally to support slider performance and track servo capacity in hard disk drives (HDDs). Moreover, the suspension for an optical slider must meet optical requirements, and is also required to satisfy criteria for shock performance in the mobility of the actuator. In this study, the optical slider and the suspension for a near-field probe array are designed and analyzed.

Dynamic Characteristic Analysis and Position Control for High Density Optical Head Using Bimorph PZT

Abstract: This paper proposed a dual actuator using Bimorph PZT for information storage device based on prove array NSOM(near-field scanning optical microscopy). The gap between the media and the optical head should be maintained within the optical tolerance. Therefore, a new actuator having high sensitivity is required. Bimorph PZT, which has fast access time and high sensitivity characteristic, is suitable for this precise actuating system. This paper is focused on derivation of mathematical model of dual Bimorph PZT actuator and control algorithm. Hamilton`s principle was used for mathematical model. The model is verified by FEA(finite element analysis), and compared with experimental results. Different control algorithms were used for two Bimorph PZT actuating same direction and opposite direction. The gap between recording media and optical head was controlled within 20nm in experiment.

Numerical Simulation and Experimental Study on the Effect of Ramp Profile, Friction and Flex-Cable Force on the L/UL Process for Small Form Factor HDD

Abstract: So in developing a system with high areal density and that resist external shock and disturbances, the essential mechanism is L/UL system. L/UL system has many benefits when applied to a small form factor (SFF) HDD. It allows for higher areal density increase since it is possible to reduce the flying height of slider and eliminate the texture zone that is used for parking for contact-start-stop systems. In addition, it allows for lower power consumption and prevents the head-slap between slider and disk during non-operating conditions.Copyright © 2005 by ASME

Robust Servo Design and Application for Optical Disk Drive Using Robust Control Theory : H ∞ vs. QFT

Abstract: 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 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.

Holographic Data Storage System using prearranged plan table by fuzzy rule and Genetic algorithm

Abstract: Holographic Data Storage System[1], one of the next generation data storage principle, is a 2-dimensional page oriented memory using volume hologram in writing and retrieving process. In the HDS system, data management procedure is performed in parallel so fast data transfer rate can be realized. And the system store data in binary form (0 or 1), so that computers can use the digital data directly. In writing procedure, Laser of specific wavelength passes through a Spatial Light Modulator (SLM) to make 2-dimensional data page. A digital data 0 makes image of a black pixel (off-pixel) by blocking the light on SLM and digital data 1 is imaged as a white pixel (on-pixel) on CCD camera. Diffraction, the nature of light, makes the laser which passes through an on-pixel surrounded by off-pixels on SLM to affect surrounding pixels by 2-dimensional Fourier Transform of a plane wave and when retrieving process the effects to surrounding pixels of an on-pixel are photographed by CCD camera and cause errors to binary data. In this paper, we generate fuzzy rules by substractive clustering and genetic algorithm. The recording and reconstruction system used fuzzy rules. The fuzzy rule parameter variable be find most suitable parameter by substractive clustering and genetic algorithm. Figure.1 is the HDDS system experiment test bed. Fig.1 HDDS system experiment Test bed

Focus pull-in behavior analysis in a blu-ray disk and various control approaches to enhance the performance of it

Abstract: The focus pull-in behavior analysis in a Blu-Ray disk (BD) and various control approach to improve the performance of it are discussed. The focus pull-in work, which locks the beam spot of an optical pick-up to the information layer in an optical disk, is an essential work in an optical disk drive (ODD), and the error tolerance of it depends on the kind of an ODD. In a BD system, the focus pull-in work should be done within a very narrow beam height region (/ N A =0.4765 µm ) and a very short period. Therefore, the moment of the focus pull-in is a transient phenomenon, and more careful analysis of it is necessary. In this paper, the focus full-in work is analyzed in depth, and various control approaches to improve the focus pull-in performance are discussed. First, various detected servo signal during the focus pull-in work are summarized briefly. Then, a novel swing arm type actuator which is developed by our center for a small form factor BD is introduced. Finally, three control approaches to perform the focus pull-in are designed and applied to the system: (i) conventional lead-lag, (ii) fuzzy control, (iii) sliding mode control. From the experiments results, we find that two control approaches, fuzzy control and sliding mode and, have more good focus pull-in performances than the conventional lead-lag approach. Keyword list : Focus pull-in, Blu-ray disk (BD), sliding mode, fuzzy, servo design

Pull-in Behavior Analysis in Optical Disk Drive Using Phase Plane and Evaluations for Effecting Parameters of it

Abstract: The track pull-in behavior analysis in an optical disk drive (ODD) using plane phase and the evaluations for effecting parameters of it are discussed. Track pull-in, track capture procedure to do track following control, is a key factor to increase data transfer rate. First, the relative velocity between the beam spot of an optical pick-up and the target track of an optical disk is analyzed during the track pull-in procedure. In this process, it is showed that the track error signal has nonlinear characteristics which are depending on the time. Second, Runge-Kutta method to solve the nonlinear equation is applied to find the track pull-in behavior, and some optimal parameters to get stable and fast pull-in condition are obtained. Then, the phase plane analysis for track pull-in procedure is presented. Finally, some comments for the simulated results are discussed briefly.

Interaction Analysis of Dual-stage System during Seek Motion and Control for Track Pull-in Enhancement

Abstract: In this paper, the dual stage interaction between the coarse actuator and the fine actuator of an optical disk drive is studied, and the new control method to enhance the track pull-in performance using fine actuator control is proposed. First, the dynamic analysis for the dual stage and the experiments to find the each actuator dynamics are performed. From the experiments, some physical parameters of the actuators were derived, then, some simulations are performed to find the interaction effect of the fine actuator during seek motion. Second, the center servo which suppresses the vibration of fine actuator during seek motion is designed and evaluated. And the fine actuator control to reduce the relative velocity between the target track and beam spot is proposed. From simulations, we show that fine actuator control which has same frequency and same phase of the disturbance is effective to reduce the relative velocity, and this result leads to track pull-in enhancement. Hence, the proposed control method is good approach to improve the track pull-in performance. Finally, the realization of the proposed method and some comments of it are briefly discussed.

Load/unload Dynamics of Slider on Ramp for Various Ramp Shapes

Abstract: L/UL(Load/unload) mechanism has been widely used in SFF(Small form factor) HDD because L/UL technology has many advantages such as an increase of areal density, reduction of power consumption and improvement of shock resistance. In this system, the most important design goal is no slider-disk contact and fast air-hearing breaking during L/UL process. To do so, we should consider many design parameters related to L/UL system. The ramp shape is the most dominant component among parameters which dramatically affect the L/UL performance. This paper makes an advanced ramp model using ANSYS/LS-DYNA. Through this FE model, this paper investigates the effect of initial ramp slope and location of air-bearing breaking. From the experiment for three different ramps, we also verify that experimental results agree with simulation results. We conclude that the ramp design should have small ramp slope at the moment which a suspension tap contacts with ramp and large ramp slope after air-bearing breaking in order to improve L/UL Performance.