• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.5
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• pp.582-589
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• 2003

This paper presents the robust stability analysis and design methodology of the fuzzy feedback linearization control systems. Uncertainty and disturbances with known bounds are assumed to be included Un the Takagi-Sugeno (TS) fuzzy models representing the nonlinear plants. $L_2$ robust stability of the closed system is analyzed by casting the systems into the diagonal norm bounded linear differential inclusions (DNLDI) formulation. Based on the linear matrix inequality (LMI) optimization programming, a numerical method for finding the maximum stable ranges of the fuzzy feedback linearization control gains is also proposed. To verify the effectiveness of the proposed scheme, the robust stability analysis and control design examples are given.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.369-374
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• 2010

Linear motors are easily affected by load disturbances, force ripples, friction, and parameter variations because there are no mechanical transmissions that can reduce the effects of model uncertainties and external disturbance. In this study, a nonlinear adaptive controller to achieve high-speed/high-accuracy position control of a two-axis linear motor is designed. The operation of this controller is based on a cross-coupling algorithm. Nonlinear effects such as friction and force ripples are estimated and compensated for. An enhanced cross-coupling algorithm is proposed for effectively improving the biaxial contour accuracy while achieving closed-loop stability. The proposed controller is evaluated by performing computer simulations.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.259-274
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• 2005

In this paper, we propose a methodology to estimate the number of users in e-Commerce systems. There have been a lot of previous work under the closed-LAN system environment. But the study on the number of acceptable users in real network environment is hard to find in the literature. Our research applies a Hybrid Simulation by using QoS results for end-to-end high-speed Internet service, and experiments are performed with regard to LAN and WAN, network equipments, and various network bandwidth. As result of the experiments we observed that the response time of high-speed Internet service media(Wireless LAN, ADSL, Cable, VDSL) depends heavily on the sequence and depth of transactions and on the ratio of transactional and non-transactional interactions. That is, as the network and application get more loads, the number of acceptable users decreases. By adding a cache server and an L4 switch to the simulation model, we analysed the changes in the number of users and client response time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.502-508
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• 2016

An optimized PI controller design method is presented to promote the control performance of an oil cooler system for high precision machine tools. First, a transfer function model of the oil cooler system with a variable rotating speed compressor was obtained by the perturbation method as the first order system with a negligible dead time. Then, the closed-loop control system was described as the second order system with a zero. Its dynamic behaviors are mostly governed by characteristic parameters, the damping ratio, and the natural frequency which is incorporated in PI gains. Next, an optimum integral of the time-weighted absolute error (ITAE) criterion was applied to the second order system. The characteristic parameters can be determined by the given design specifications, percent overshoots and settling times and comparisons with the ITAE criterion. Hence, the PI gains were plainly identified in a deterministic way. Finally, the PI gains were fine-tuned to obtain desirable dynamics in real systems, considering the zero effect and parameter variations. The validity of the proposed method was proven by computer simulations and real experiments for selected cases.

• Journal of Environmental Science International
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• v.21 no.3
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• pp.277-287
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• 2012

The MFFn(Mass First Flush) was analyzed for various rainy events(monitoring data from 2008 to 2009) in Transportation area(Highway, National road, Trunk road). Estimated MFFn using SWMM was evaluated by comparison with observed MFFn. MFFn was estimated by varying n-value from 10% to 90% on the rainy events. The n-value increases, MFFn is closed to '1'. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good ($R^2$=0.89). Pollutants runoff loads by volume showed Highway 26.6%, National road 44.8%, Trunk road 35.0% at the MFF20(20% by total runoff). A case of MFF30, pollutants runoff loads by volume showed Highway 40.2%, National road 54.3%, Trunk road 46.8%. According to the results, Initial precipitation basis were Highway MFF30, National road MFF20, Trunk road MFF30 when the Non-Point source control facilities set up.

• KIEAE Journal
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• v.11 no.2
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• pp.105-111
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• 2011

Aims of this study is to investigate the daylighting control strategy of venetian blind system was performed as a function of ratio of shading height to window and slat angles in the preliminary stage of the parametric study. Floor-to-ceiling window walls of living spaces are used widely in apartment buildings since the Korean government has legally allowed elimination of the balcony area. Enlarging living area by balcony elimination, the larger glass area of window is exposed to the direct sunlight. As a common sunlight controlling device, blind system can be used in all orientations and all latitudes and it may obstruct, absorb, reflect and transmit solar radiation to building by proper adjusting. However, blind system can produce discomfort in occupant and less energy efficiency, if it has not been controlled optimally. The simulation model was based on the unit module of typical living space with balcony elimination. The room dimension was $6.0m(w){\times}6.9m(d){\times}2.7m(h)$ with floor to ceiling height of 2.5m. The blind system was simulated at five slat angles (horizontal, $30^{\circ}$, $45^{\circ}$ upward and downward tilted) and the four ratio of shading height to window (fully closed, partly opened, no-blind) using the Desktop RADIANCE 2.0 program. The series of simulation results indicates that the advantages of available daylight and outside of view can be improved by proper adjusting blind system.

• Journal of the Korean Institute of Educational Facilities
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• v.5 no.1
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• pp.33-43
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• 1998

With increased social participation of married women and with the notion of importance of pre-school childhood on human development, the importance of nurseries is being emphasized. The transformation of the traditional family system into a nuclear family system and the deterioration of the traditional child education have also put nurseries as a primal social interest. But, at present, at the end of 1994, only 10% of the children have benefitted from such facilities, the supply not being able to meet demand. Also, the spatial organization and the management of such facilities has been unsatisfactory. In this perspective, this study aims to grasp the present condition of nurseries, to investigate and analyse case studies, to suggest standards and reform measures, and based on these, to produce basic information for the formation of an architectural spatial model. We've selected investigation of present conditions and case studies, interviews, and observation as investigative methods and through these we've assessed tangible spatial planning and spatial proportion by parts. 1. The most preferred grouping method is toddler/preschooler type, and the group size and staff-to-child ratios vary according to the children's age 2. The younger children's activity rooms are located in the lower level, and the activity room of the children on the similar development stages are located adjacent to one another 3. Most of the facilities do not have the public spaces(indoor playrooms, dinning rooms, napping rooms, bathrooms, sickrooms) For dinning and napping, activity rooms are being used, and for sickrooms, director's room or staff rooms 4. As for the correlations of the spaces(home bases, activity rooms and its outdoor spaces, day-care-centers and its community), closed plan type is 90% over, and modified open plan is 10% min.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.543-552
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• 2013

For the safety messages in IEEE 802.11p/WAVE vehicles network environment, strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. In crowded networks where beacon message are broadcasted at a high number of frequencies by many vehicles, which used for beacon sending, will be congested by the wireless medium due to the contention-window based IEEE 802.11p MAC. To resolve the congestion, we consider a MAC scheme based on slotted p-persistent CSMA as a simple non-cooperative Bayesian game which involves payoffs reflecting the attempt probability. Then, we derive Bayesian Nash Equilibrium (BNE) in a closed form. Using the BNE, we propose new congestion control algorithm to improve the performance of the beacon rate under saturation condition in IEEE 802.11p/WAVE vehicular networks. This algorithm explicitly computes packet delivery probability as a function of contention window (CW) size and number of vehicles. The proposed algorithm is validated against numerical simulation results to demonstrate its stability.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.224-234
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• 2008

Multi-phase machines can be used in variable speed drives. Their applications include electric ship propulsion, 'more-electric aircraft' and traction applications, electric vehicles, and hybrid electric vehicles. Multi-phase machines enable independent control of a few numbers of machines that are connected in series in a particular manner with their supply being fed from a single voltage source inverter(VSI). The idea was first implemented for a five-phase series-connected two-motor drive system, but is now applicable to any number of phases more than or equal to five-phase. The number of series-connected machines is a function of the phase number of VSI. Theoretical and simulation studies have already been reported for number of multi-phase multi-motor drive configurations of series-connection type. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information concerning the rotor speed is extracted from measured stator currents and voltages at motor terminals. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an MRAS estimator based sensorless control of a vector controlled series-connected two-motor five-phase drive system with current control in the stationary reference frame. Results, obtained with fixed-voltage, fixed-frequency supply, and hysteresis current control are presented for various operating conditions on the basis of simulation results. The purpose of this paper is to report the first ever simulation results on a sensorless control of a five-phase two-motor series-connected drive system. The operating principle is given followed by a description of the sensorless technique.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.168-180
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• 2018

In order to achieve the high quality output voltage of single-phase voltage source inverters, in this paper an Adaptive Complementary Sliding Mode Control (ACSMC) is proposed. Firstly, the dynamics model of the single-phase inverter with lumped uncertainty including parameter variations and external disturbances is derived. Then, the conventional Sliding Mode Control (SMC) and Complementary Sliding Mode Control (CSMC) are introduced separately. However, when system parameters vary or external disturbance occurs, the controlling performance such as tracking error, response speed et al. always could not satisfy the requirements based on the SMC and CSMC methods. Consequently, an ACSMC is developed. The ACSMC is composed of a CSMC term, a compensating control term and a filter parameters estimator. The compensating control term is applied to compensate for the system uncertainties, the filter parameters estimator is used for on-line LC parameter estimation by the proposed adaptive law. The adaptive law is derived using the Lyapunov theorem to guarantee the closed-loop stability. In order to decrease the control system cost, an inductor current estimator is developed. Finally, the effectiveness of the proposed controller is validated through Matlab/Simulink and experiments on a prototype single-phase inverter test bed with a TMS320LF28335 DSP. The simulation and experimental results show that compared to the conventional SMC and CSMC, the proposed ACSMC control strategy achieves more excellent performance such as fast transient response, small steady-state error, and low total harmonic distortion no matter under load step change, nonlinear load with inductor parameter variation or external disturbance.