• 한국공작기계학회논문집
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• 제16권4호
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• pp.101-107
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• 2007

The objective of this research work is to investigate into effects of an auto tracking of the focal distance on the quality of the cut part in the cutting of a low carbon sheet using a high-power CW Nd:YAG laser. An auto-tracking system with a capacitance based distance control loop has been employed to perform a real control of the focal distance. In order to examine the influence of the auto-tracking of a focal distance on the optimum focal distance, the kerfwidth, surface roughness and the formation of the cut section, several linear cutting tests have been carried out using the auto-tracking system. The results of experiments have been shown that the optimum focal distance is 0.9mm. In addition, it has been shown that the variation of kerfwidth and the surface roughness of the cut part with control of the focal distance are reduced 40-80% and 30-55% in comparison with those of the cut part without tracking of the focal distance. From the results of the experiments, it has been found that the real time tracking of the focal distance can improve the part quality.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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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.

• 한국군사과학기술학회지
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• 제20권1호
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• pp.108-118
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• 2017

In this paper, the path tracking controller for a surface vessel based on the sliding mode control (SMC) with the switching law is proposed. In order to have no restriction on movement and improved tracking performance, the proposed control system is developed as follows: First, the kinematic and dynamic models in Cartesian coordinates are considered to solve the singularity problem at the origin. Second, the new multiple sliding surfaces are designed with the SMC and approach angle concept to solve the under-actuated property. Third, the switching control system is designed to improve tracking performance. To prove the stability of the proposed switching system under the arbitrary switching, the Lyapunov stability analysis method with the common Lyapunov function is used. Finally, the computer simulations are performed to demonstrate the performance, effectiveness and stability of the proposed tracking controller of a surface vessel.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1673-1675
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• 1996

We have studied the effect of surface tension and flow rate of contaminants, wettability, frequency of applied voltage dependence of tracking breakdown. As the flow rate of contaminant is increasd, the surface resistivity is decreased, and the leakage current is increased, the time to tracking breakdown is decreased. It is found that time to tracking breakdown depends on the frequency of contaminant, that is difference of wettability. And as the frequency of applied voltage is increased, time to tracking breakdown decreased.

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.56-64
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• 2006

This paper proposes a new and simple input prediction method for robust servo system. A robust tracking control system for optical disk drives to reject disk runout was recently proposed based on both Coprime Factorization(CF) and Zero Phase Error Tracking(ZPET) control. The CF control system can be designed simply and systematically. Moreover, this system has not only stability but also robustness to parameter uncertainties and disturbance rejection capability. Since optical disk tracking servo systems can detect only racking error, it was proposed that the reference input signal for ZPET could be estimated from tracking errors. In this paper, we propose a new control structure for the ZPET controller. It requires less memory than the previously proposed method for the reference signal generation. Therefore, it is very effective in runout control. Furthermore, this method can be applied to defective optical disk like surface defects on disk. Numerical simulation and experimental result show the proposed method effective.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• 제어로봇시스템학회논문지
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• 제20권8호
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• pp.789-794
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• 2014

This paper presents some real performance of two typical bilateral teleoperation benchmark tasks: peg-in-hole and surface tracking tasks. The tasks are performed by an energy-bounding algorithm in the master control and position-based impedance algorithm in the slave control. Performance is analyzed for the position-force tracking capabilities from free space motion to surface contacting motion. In addition, preliminary user performance is evaluated by measuring the completion time and maximum/average contact forces. The quality of the measured performance is also compared with that of other existing approaches.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.154-155
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• 2006

This paper describes a tracking test results for the organic polymers with PE(polyethylene) series by a declining method. After processing the 4 PE series insulations with different density, the tracking duration for each was measured and compared with that for ABS(acrylonitrile butadiene styrene). The surface condition of each specimen was carefully observed after the tracking test. As a result, HDPE showed excellent performance in tracking test.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.1045-1050
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• 1992

A new sliding surface for a viaraible structure control(VSC) law is emplyed to achieve fast and robust path tracking in a class of second-order nonlinear unceratin dynamical systems. The surface onitialy passes arbitrarily given initial conditions and subsequently moves towards a predetermined surface via rotaiting or/and shifting. We call it as a moving sliding surface(MSS). The surface is then incorporated with the VSC law which is constructed by imposing the sliding conditions in a special way. We primarily enforce the conditions which assume that once the system state is on a sliding surface that it is driven towards the zero state. Using the VSC law associatied with the MSS, it is shown that the tracking behavoirs are remarkably improved in the sene of the fastness and the robustness.

• Bulletin of the Korean Chemical Society
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• 제22권5호
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• pp.455-462
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• 2001

The time-dependent tracking inversion method is studied to extract the potential energy surface of the electronic excited state in the photodissociation of triatomic molecules. Based on the relay of the regularized inversion procedure and time-dependent wave packet propagation, the algorithm extracts the underlying potential energy surface piece by piece by tracking the time-dependent data, which can be synthesized from Raman excitation profiles. We have demonstrated the algorithm to extract the potential energy surface of electronic excited state for NO2 molecule where the wave packet split on a saddle-shaped surface. Finally, we describe the merits of the time-dependent tracking inversion method compared with the time-independent inversion method and discussed several extensions of the algorithm.