• Journal of Power Electronics
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• v.8 no.2
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• pp.141-147
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• 2008

This paper deals with a new and improved control technique for shunt active filters (AF) used for compensating unwanted harmonic currents injected in the mains due to nonlinear varying loads. This work is motivated by the need to find a permanent solution to the rigorous hit and trial method for evaluating system parameters in an indirect control of AF. A fuzzy pre-compensated PI (Proportional-Integral) controller is used to fuzzify the reference DC voltage of AF to the controller input so that the overshoots and undershoots in its DC link voltage are minimized and the settling time is improved. A three-phase diode rectifier with R-L (Resistive-Inductive) load is used as a non-linear load to study the effectiveness of the proposed controller of the AF. Robustness to filter parameter variations, insensitivity to controller parameter variations, and transient response has been taken as performance evaluation parameters. The results are shown through simulations in Matlab using power system block sets to demonstrate the capability of the proposed controller of the AF.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.219-223
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• 1995

This paper deals with the robust control system for parameter variations, fast responses and load torque variations. Frist, fuzzy-sliding adaptive control be used to. Fuzzy-sliding adaptive control is good at fast response. Second, there are many requests for selecting freely the moment of inertia, even though moment of inertia is determined with the materials, structure, shape, and size of the motors. Therefore we developed an inertia-lowering control system that uses torque observer to reduce the moment of inertia. Finally, using torque observer, torque control is done so as to compensate load torque. Consequently, the proposed system verified the superiority through the simulations using MATLAB.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1317-1324
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• 1998

In general, DI gasoline engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance and lower emissions due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, some kinds of methodologies have been adapted in various papers. In this study, a reflector was adapted around the injector nozzle to apply the concept of stratified charge combustion which leads the air-fuel mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally rich to ignite while the lean mixture is wholly introduced into the combustion chamber. The characteristics of combustion is analyzed with the variations of fuel injection pressure and load in a stratified -charge direct injection single cylinder gasoline engine. The obtained results are summarized as follows ; 1. The MBT spark timing approached to TDC with the increase of load on account of the increase of evaporation energy, but has little relation with fuel injection pressure. 2. The stratification effects are apparent with the increase of injection pressure. It is considered by the development of secondary diffusive combustion and the increase of heat release of same region, but proceed rapidly than diesel engine. Especially, in the case of high pressure injection (l70bar) and high load (3.0kgf m), the diffusive combustion parts are developed excessively and results in the decrease of peak pressure than in the case of middle load. 3. The index of engine stability, COVimep value, is drastically decreased with the increase of load. 4. To get better performance of DI gasoline engine development, staged optimizaion must be needed such as injection pressure, reflector, intake swirl, injection timing, chamber shape, ignition system and so on. In this study, the I50bar injection pressure is appeared as the optimum.

• Composites Research
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• v.36 no.2
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• pp.80-85
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• 2023

A cylindrical composite lattice structure is manufactured by filament winding. The distribution of nonuniform fiber volume fraction induced by the manufacturing process can be observed. The stiffness and buckling characteristics can be influenced by non-uniform fiber volume fraction. In this paper, the effect of non-uniform fiber volume fraction through thickness direction on the torsional buckling load of the cylindrical composite lattice structure was examined. The stiffness variation induced by the non-uniform fiber volume fraction was applied to the finite element model, and buckling analysis was performed. The variations of buckling load with variations of fiber volume fraction were compared. The non-uniform fiber volume fraction reduced the torsional buckling load of the composite lattice structure.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.69-72
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• 2003

In this paper new control strategy of series resonant converter system for control power supply is suggested. Frequency controlled series resonant converter system is robust to load variations because it is POSR(parallel output series resonant) type. And it provides stable output voltage by changing switching frequency to input voltage variations. Firstly, operation analysis about suggested series resonant converter system was carried. Then simulations using ACSL(Advanced Continuous Simulation Language) and experiments to actual system were carried to prove characteristics of suggested system.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.28-31
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• 1988

This paper proposes a new linear adaptive position controller of DC servo motor. The proposed method can improve the drive performance and rapidly reject the state error caused by both parameter variations and force disturbance. The structure of this adaptive control method is based multiloop feedback control and model reference control. Simulation results are presented to verify the improved response when parameter variations and load disturbance give relatively significant effects to the servo system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.355-362
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• 2003

The fault analysis problem of a distribution network has many difficulties comes from the unbalance of loads or networks and the lacks of load information. The unbalance of loads or networks make the fault location difficult when it use the classical sequence transformation. Moreover the amount of load in the distribution networks fluctuates with time. This paper introduces a recent fault location algorithm using iterative method which handle the unbalance of the problem. But, the fault location errors comes from the load fluctuations still left. For the real application of the new fault location algorithm in distribution networks, this paper studied the effect of the load fluctuations in the algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.54-59
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• 2006

An analytical solution for deflection-load characteristics of a conical disk spring used especially in the automotive manual transmission clutch applications is proposed in order to take into account the effects of friction and large deformation. The conical disk spring, or the diaphragm spring, has a hinge support, an application point of release load at the tip of the fingers and an application point of clamp load near but inside the outer perimeter of the conical disk spring. The friction coefficient is assumed to be a constant regardless of the speed of deflection and the magnitude of loads. Comparison with experimental shows a good agreement with the analytical prediction. Also, the sensitivity of the clamp load due to variations in the geometrical parameters of the conical disk spring is calculated and discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.26-32
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• 2010

This paper proposes a new load torque observer based on the Takagi-Sugeno fuzzy method for a permanent magnet synchronous motor(PMSM). A Linear Matrix Inequality(LMI) parameterization of the fuzzy observer gain is given, and the LMI conditions are derived for the existence of the fuzzy load torque observer guaranteeing $\alpha$-stability and linear quadratic performance. In this paper, a nonlinear speed controller is employed to validate the performance of the proposed fuzzy load torque observer, and various simulation results are presented under motor parameter and load torque variations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.731-737
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• 2005

This paper evaluates dynamic performance of a cab over type large-sized truck for estimating the effects of frame's torsional characteristics using a computer model. The computer model considers two mounting methods of frame, flange mounting and web mounting. Frame is modeled by finite elements using MSC/NASTRAN In order to consider the flexibility of frame. The torsional test of the frame is conducted In order to validate the modeled finite element model. A load cell is used to measure the load applied to the frame. An angle sensor is used to measure the torsional angle. An actuator is used to apply a load to the frame. To estimate the effects of frame's torsional characteristics on dynamic performance, simulations are performed with the flange mounting and web mounting frame. Simulation results show that the web mounting frame's variations of roll angle, lateral acceleration, and yaw rate are larger than the flange mounting frame's variations, especially in the high velocity and the second part of the double lane course.