• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.4
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• pp.27-37
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• 1996

In this paper the effects of suspension design parameters on the steady-state cornering performance of vehicles are studied. To investigate the understeer characteristics of vehicles, steady-state cornering equatons are derived from a two-track model which is expanded from a simple one track model. The effects of the suspension design parameters as well as those of lateral load transfer are taken into consideration. To verify the equation, a skid pad test was carried out with a domestic passenger car. The design parameters of the vehicle are measured using a Suspension Parameter Measuring Device(SPMD). Based on these results, parameter studies are carried out to determine the effect of design parameters on the cornering performance of a vehicle, both in low and high acceleration region.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1398-1408
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• 2018

In order to further improve the steady-state control performance of model predictive torque control (MPTC), a double-vector-based model predictive torque control without a weighting factor is proposed in this paper. The extended voltage vectors synthesized by two basic voltage vectors are used to increase the number of feasible voltage vectors. Therefore, the control precision of the torque and the stator flux along with the steady-state performance can be improved. To avoid testing all of the feasible voltage vectors, the solution of deadbeat torque control is calculated to predict the reference voltage vector. Thus, the candidate voltage vectors, which need to be evaluated by a cost function, can be reduced based on the sector position of the predicted reference voltage vector. Furthermore, a cost function, which only includes a reference voltage tracking error, is designed to eliminate the weighting factor. Moreover, two voltage vectors are applied during one control period, and their durations are calculated based on the principle of reference voltage tracking error minimization. Finally, the proposed method is tested by simulations and experiments.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.1
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• pp.46-58
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• 2011

A steady-state analysis and a simple dynamic model as simplified methods are developed, and results of energy consumption loads are compared with results obtained using computer to evaluate the analytical solution. Before obtaining simplified model a mathematical model is formulated for the effect of wall mass on the thermal performance of four different houses having various wall construction. This analytical study was motivated by the experimental work of Burch et al. An analytical solution of one-dimensional, linear, partial differential equation for wall temperature profiles and room air temperatures is obtained using the Laplace transform method. Typical Meteorological Year data are processed to yield hourly average monthly values. This study is conducted using weather data from four different locations in the United States: Albuquerque, New mexico; Miami, Florida; Santa Maria, California; and Washington D.C. for both winter and summer conditions. The steady state analysis that does not include the effect of thermal mass can provide an accurate estimate of energy consumption in most cases except for houses #2 and #4 in mild weather areas. This result shows that there is an effect of mass on the thermal performance of heavily constructed house in mild weather conditions. The simple dynamic model is applicable for high cycling rates and accurate values of inside wall temperature and ambient air temperature.

• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.191-202
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• 2003

Availability is an important measure of performance of a repairable component. In this paper, the explicit expression for the availability of a repairable component, which is subject to the policy II(Age Replacement Policy) of Barlow and Hunter (1960), is obtained and the existence of the steady state availability is shown. The steady state availabilities of the model are also obtained for the cases when the mean of the minimal repair time is increasing at a geometric rate or linearly increasing, In order to show the importance and the utility of the obtained result, we also consider an illustrative example of the repairable coherent system whose components are repairable, and the obtained results are applied to derive the steady state availability of the whole system. In this situation, we can see that the condition of the existence of the steady state availability for each component is essential. Some remarks on the optimal replacement policy that maximizes the steady state availability are also given.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.13-20
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• 2014

The steady-state, incompressible and three-dimensional numerical analysis was carried out to evaluate turbulent models on the aerodynamic performance of a small-size axial fan(SSAF). The prediction performance on the static pressure of all turbulent models is going downhill at the high static pressure and low flowrate region, but has improved at the axial flow region. In consequence, all turbulent models predict the static pressure coefficient with an error performance less than about 4% after the region of the flowrate coefficient of about 0.14. Especially, the turbulent model of SST $k-{\omega}$ shows the best prediction performance equivalent to an error performance less than about 2% on the static pressure.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.85-96
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• 2011

Steady state computations are routinely used by design engineers to evaluate and compare losses in hydraulic components. In the case of the draft tube diffuser, however, experiments have shown that while a significant number of operating conditions can adequately be evaluated using steady state computations, a few operating conditions require unsteady simulations to accurately evaluate losses. This paper presents a study that assesses the predictive capacity of a combination of steady and unsteady RANS numerical computations to predict draft tube losses over the complete range of operation of a Francis turbine. For the prediction of the draft tube performance using k-${\varepsilon}$ turbulence model, a methodology has been proposed to average global performance indicators of steady flow computations such as the pressure recovery factor over an adequate number of periods to obtain correct results. The methodology will be validated using two distinct flow solvers, CFX and OpenFOAM, and through a systematic comparison with experimental results obtained on the FLINDT model draft tube.

• Journal of Korean Institute of Industrial Engineers
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• v.11 no.2
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• pp.1-9
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• 1985

In this study, two stage transfer line with limited repair capability is modeled to formulate optimal dynamic repair priority policy. The method of Markov Chains is used to analyze the analytical model of this line. An efficient algorithm is developed, utilizing the block tridiagonal structure of the transition probability matrix, to obtain the steady state probabilities and system performance measures, such as the steady state production rate of the line and the average in-process inventory in the interstage buffer.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.309-312
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• 1997

The dynamic characteristics of a continuous MMA/MA free-radical solution copolymerization reactor were studied. A mathematical model was developed and kinetic parameters which had been estimated in the previous work were used. With this model, bifurcation diagrams were constructed with various parameters as the bifurcation parameter to predict the region of stable operating conditions and to enhance the controller performance. It was shown that the steady-state multiplicity existed over wide ranges of residence time and jacket inlet temperature. Periodic solution branches were found to emanated from Hopf bifurcation points. Under certain conditions isola was also observed, which would result in poor performance of feedback controllers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.5
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• pp.275-281
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• 2010

Car HVAC is one of main factors influencing a potential customer's first impression. It should be fault-free, which requires the most stable control performance. So, the control algorithm consists of a proportional feedback only, not with an integral action needed for elimination of steady-state errors. To reduce the errors and make the response faster, feedforward algorithm based on predicted thermal load is added. To evaluate the performance, car HVAC is dynamically modelled and its control logic is simulated. The results shows that the proportional feedback leads to about $4^{\circ}C$ of steady-state error. When the feedback is combined with the feedforward algorithm and with a set value update based on disturbances, it predicts less than $1^{\circ}C$ of control error and improved thermal comfort.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.100-109
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• 2003

A performacne simulation model of the PT6A-62 turboprop engine using the $SIMULINK^R$ was proposed to predict transient and steady state behaviors. The $SIMULINK^R$ has several advantages such as user-friendliness due to the GUI(Graphic User Interfaces) and ease in the modification of the computer program. The $SIMULINK^R$ model consists of subsystems to represent engine gas path components such as flight initial subsystem, compressor subsystem, burner subsystem, compressor turbine subsystem, power turbine, exhaust nozzle subsystem and integrator subsystem. In addition to subsystems, there are search subsystems to find an appropriate operating point by scaling from the 2-D components look-up table, Gasprop Subsystem to calculate the gas property precisely. In case of steady state validation, performance results analyzed by the proposed $SIMULINK^R$ model were agreed well with the analysis results by the commercial GASTURB program. Moreover in validation of the transient model, it was found that performance simulation results by the proposed model were reasonable agreement with analysis results by the well-proved computer program using FORTRAN.