• Journal of the Korean Society for Railway
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• v.8 no.3
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• pp.235-243
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• 2005

Following the rail reform in 2004, rail industry in Korea has separated into two parts: one is the infrastructure manager and the other is train operator. Amongst many aspects, track access charging system is one of the imminent aspects to be studied closely to make the rail reform successful. In this study, track access charging systems of European countries are closely investigated and compared one another and lessons learnt from their experiences are derived. Finally, policy directions regarding the track access charging system to be adopted in Korea are suggested.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.5
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• pp.402-410
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• 2004

To obtain a good tracking performance in an optical disk drive servo system, it is essential to attenuate periodic disturbances caused by eccentric rotation of the disk. As an effective control scheme for enhancing disturbance attenuation performance, disturbance observers (DOBs) have been successfully applied to the track-following servo system of optical disk drives. In disk drive systems, the improvement of data transfer rate has been achieved mainly by the increase of disk rotational speed, which leads to the increase of the disturbance frequency. Conventional DOBs are no longer effective in disk drive systems with a high-speed rotation mechanism because the performance of conventional DOBs is severely degraded as the disk rotational frequency increases. This paper proposes a new DOB structure for effective rejection of the disturbance in optical disk drives with a very high rotation speed. Asymptotic disturbance rejection is achieved by adopting a band-pass filter in the DOB structure, which is tuned based on the information on the disturbance frequency. In addition, performance sensitivity of the proposed DOB to changes in disk rotational frequency is analyzed. The effectiveness of the proposed DOB is verified through simulations and experiments using a DVD-ROM drive.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.223-228
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• 2005

In oprical disk drives, surface defects on a disk distort tracking error signal and disturb a precision tracking control.. A conventional method against disk defect is held the tracking control signal when a defective portion is detected. However, if the defective portion is getting longer, objective lens will get away from following track. In order to keep the postion of spot from following track, the servo system must predict tracking error and control the object lens in the defective portion. A tracking control system for optical disk drives was proposed recently based on both Coprime Factorization(CF) and Zero Phase Erro. Tracking(ZPET) control. The system was proposed for overcome the limit of previously tracking error. But there were no research about the method against the defective portion. This paper proposes a new and simple ZPET construct. as a new method against the defective portion. From experimental results, we have proved that proposed method improves the performance against the defective portion, decreases the uncertainty of a model, and requires less memory than the previously proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.279-286
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• 2010

In this paper, we provide a robust track-following controller design method for the stable coarse seek control. Due to the inaccurate velocity control during a coarse seek, the shake of fine actuator is generated and thus a gain-up track-following control is required to complete stably the coarse seek. To this end, a loop gain adjustment algorithm is introduced to estimate accurately the shake of fine actuator. A weighting function can be properly selected from a minimum tracking gain-up open-loop gain, calculated from the estimated shake quantity of fine actuator. A robust tracking gain-up controller is designed by considering a robust $H_{\infty}$ control problem using the weighting function. The proposed design method is applied to the coarse seek control system of an optical rewritable drive and is evaluated through the experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.87.4-87
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• 2001

In this paper, a design guideline of disturbance observer(DOB) for track-following controller is presented. In the track-following control system(TFCS) of optical disk drive(ODD), disturbance rejection is the key issue for the overall performance. DOB gives an excellent advantage of disturbance rejection within its bandwidth determined by a low-pass filter. In general, design of DOB requires a tradeoff between performance and stability, which should be based on quantitative analysis. The external disturbance is well-defined in the frequency domain, which provides the base of the analysis. In addition to a DOB, a proper feedback controller is utilized for guaranteeing overall stability. Some computer simulations and experiments are conducted and some of the results are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.93-99
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• 2011

A PRT vehicle's control method is presented in this paper. In the asynchronous vehicle control system, vehicles follow their leading vehicles. Leading vehicles are defined differently among the different types of track. The main topic of this paper is to present a method to define the leading vehicle among different types of track and the calculation algorithm of the safety length the following vehicle must maintain. Simulation program is developed using the algorithm and the results of the test run are presented. An asynchronous PRT vehicle control algorithm was presented by Szillat in the paper "A low level PRT Microsimulation, Dissertation, University of Bristol, 2001". But it is different from the algorithm in this paper. In the algorithm proposed by Markus, vehicles in the merging track are controlled synchronously, and its safety distance between the leading and the following car is evaluated after the establishment of the complicated future time-location table instead of simple equations proposed in this paper.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.491-501
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• 2021

A difference in subgrade settlement between two rails of a track manifests as lateral differential subgrade settlement. This settlement causes unsteadiness in the motion of trains passing through the corresponding area. To illustrate the effect of lateral differential subgrade settlement on the dynamic response of a vehicle-track coupling system, a three-dimensional vehicle-track-subgrade coupling model was formulated by combining the vehicle-track dynamics theory and the finite element method. The wheel/rail force, car body acceleration, and derailment factor are chosen as evaluation indices of the system dynamic response. The effects of the amplitude and wavelength of lateral differential subgrade settlement as well as the driving speed of the vehicle are analyzed. The study reveals the following: The dynamic responses of the vehicle-track system generally increase linearly with the driving speed when the train passes through a lateral subgrade settlement area. The wheel/rail force acting on a rail with a large settlement exceeds that on a rail with a small settlement. The dynamic responses of the vehicle-track system increase with the amplitude of the lateral differential subgrade settlement. For a 250-km/h train speed, the proposed maximum amplitude for a lateral differential settlement with a wavelength of 20 m is 10 mm. The dynamic responses of the vehicle-track system decrease with an increase in the wavelength of the lateral differential subgrade settlement. To achieve a good operation quality of a train at a 250-km/h driving speed, the wavelength of a lateral differential subgrade settlement with an amplitude of 20 mm should not be less than 15 m. Monitoring lateral differential settlements should be given more emphasis in routine high-speed railway maintenance and repairs.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.106-112
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• 1998

Recently, the amount of image and audio data has been increasing dramatically for high performance. According to this trend, a high-density magnetic recording system is necessitated and the tracks of magnetic tapes are getting narrower. This, in turn, requires the capstan servo system of the magnetic recording system such as DVCR to control precisely the speed and position of the capstan motor. Especially, in case of play-back, the capstan servo system should be able to position and maintain the head on the desired place of the track. To meet this requirement, digital camcorders use ATF (Automatic Track Following). In this paper, a new ATF block using discrete Fourier transform is proposed. The proposed ATF block was designed and implemented in ALTERA FPGA chips and fully tested in a real DVCR system. It is shown through experiments that the new ATF block is more cost-effective than other existing ATF blocks using digital lowpass filters. In particular, the number of logic gates can be reduced by 20% in average, compared to the existing ATF's.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1089-1094
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• 2004

Diseases in the gastro-intestinal track are on an increasing trend. In order to diagnose a patient, the various signals of the digestive organ, such as temperature, pH, and pressure, can offer the helpful information. Among the above mentioned signals, we choose the pressure variation as a monitoring signal. The variation of a pressure signal of the gastro-intestinal track can offer the information of a digestive trouble or some clues of the diseases. In this paper, a pressure monitoring system for the digestive organs of a living pig is presented. This system concept is to transmit the measured biomedical signals from a transmitter in a living pig to wireless receiver that is positioned out of body. The integrated solution includes the following parts: (1) the swallow type pressure capsule, (2) the receiving set consisting of a receiver, decoder box, and PC. The merit of the proposed system if that the monitoring system can supply the precise and repeatable pressure in the gastro-intestinal track. In addition, the design of low power consumption enables it to keep sending reliable signals while the pressure capsule is working in the digestive organ. The subject of the study for the pressure monitoring system is in-vivo experiments for a living pig. We achieved the pressure tracings in digestive organs and verified the validity of system after several in-vivo tests using pressure monitoring system. As a result, we found each organ has its own characterized pressure fluctuation.

• Journal of the Semiconductor & Display Technology
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• v.10 no.2
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• pp.25-30
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• 2011

This paper presents a tracking vibration estimation system of the track-following system using a tracking loop gain adjustment algorithm and a genetic algorithm. The algorithms are introduced to estimate accurately the tracking vibration quantity in spite of the uncertainties of the tracking actuator. An estimated actuator model can be found by applying a genetic algorithm. Accordingly, the tracking vibration quantity can be estimated from the measured tracking error, the tracking controller and the estimated actuator model. The proposed tracking vibration estimation method is applied to the track-following system of an optical recording device and is evaluated through the experimental result.