• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.947-953
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• 2007

Occurrence of pressure pulsation in positive displacement hydraulic turbine is one of the principal problems which should be cleared to improve the turbine performance and to put the turbine to practical use. Therefore, present study is tried to examine the occurrence mechanism and characteristics of the pressure pulsation CFD analysis and experimental measurement are implemented in this study to clarify the phenomena of unsteady pressure pulsation. The results show that occurrence reason of the pressure pulsation is not only due to a series of opening and closing of the chamber formed between rotor and casing wall but also due to the variation of rotational speed of following rotor. The pressure pulsation causes torque variation and the curve patterns of the torque variation conforms to that of the pressure pulsation. Pressure in the chamber is equal to the averaged value of inlet and outlet pressures. Sudden pressure decrease by accelerated through-flow between lobe and casing wall results in torque loss.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.2
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• pp.97-102
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• 2003

In this paper, a recurrent artificial neural network (RNN) based self-tuning speed controller is proposed for the high-performance drives of induction motors. The RNN provides a nonlinear modeling of a motor drive system and could provide the controller with information regarding the load variation system noise, and parameter variation of the induction motor through the on-line estimated weights of the corresponding RNN. Thus, the proposed self-tuning controller can change the gains of the controller according to system conditions. The gain is composed with the weights of the RNN. For the on-line estimation of the RNN weights, an extended Kalman filter (EKF) algorithm is used. A self-tuning controller is designed that is adequate for the speed control of the induction motor The availability of the proposed controller is verified through MATLAB simulations and is compared with the conventional PI controller.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.1-8
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• 1999

This paper describes the method for detection of the misfired cylinder by analysis of the variation of pressure occurred in exhaust manifold on an MPI gasoline engine. Misfired cylinder(s) cause a loss of power, an increase of fuel consumption and exhaust emission and vibration is caused by unsteady torque. Therefore early detection and correction of misfired cylinder(s) play a very important role in the proper performance and the exhaust emission. The method is a comparison of integration pressure index during the period of a blowdown in the displacement period. Experimental results showed that the method, using the variation of pressure in the exhaust manifold is proven to be effective in the detection of single cylinder or multiple cylinders misfire on the gasoline engine regardless of the engine revolutions. In addition, this method, using the variation of pressure in the exhaust manifold is a very easy and accurate method compared with other methods.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.257-258
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• 2016

Construction of Multi-Family Housing(MFH) was rapidly spread in the 1990s, it has been mostly passed more than 20 years and it is faced to aging time. Remodeling has emerged a major issue in the construction industry as an alternative of improvement and recovery the initial performance of the deteriorated MFH. But, Many decision-makers are struggling to determine whether to conduct a remodeling because of profitability. In this context, this research was conducted as the following steps to achieve this research goal, i) remodeled MFH cases and comparative cases were collected, ii) the price information based on three time frames (i.e., before remodeling, after remodeling, and present) was collected, and iii) the relative price variation of the remodeled cases was analyzed and finally it is revealed that there are four patterns of price variation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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• pp.116-123
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• 2005

The traditional process capability indices Cp, Cpk, Cpm, $Cpm^+$ have been used to characterize process performance on the basis of univariate quality characteristics. Cp, Cpk consider the process variation, Cpm considers both the process variation and the process deviation from target and Cpm+ considers economic loss for the process deviation from target. In manufacturing industry, there is growing interest in quantitative measures of process variation under multivariate duality characteristics. The multivariate process capability index incorporates both the process variation and the process deviation from target or considers expected loss caused by the process deviation from target. This paper proposes multivariate capability index based on the expected loss derived from multivariate normal distribution.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.56-62
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• 2008

The surface and edge structure of OSB is defined by surface strand orientation and strand mat thickness variation parallel to the length of the panel using video-microscope. The bending strength of OSB was correlated with surface strand orientation and decreased with increasing the orientation angle in the direction parallel to length of the panel. Average strand mat thickness variation parallel to the length of the panel did not influence the bending strength, but the bonding characteristics among the outermost strands affects the bending strength of OSB. Hankinson formula can be used to predicts the MOE according to strand orientation in the surface of OSB, and more precise strand alignment and reducing thickness variation should be important in the structural performance of OSB panels.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.2
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• pp.233-243
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• 1994

Generally, fuzzy PI controller that regulates the gains using fuzzy algorithm shows high performance in speed response. However, it has some problems to the load inertia variation, because the change of speed error(CE) is in a fixed range. As load inertia increases, CE is decreased and the usuage of fuzzy table is limited. Therefore, the output of the fuzzy controller has a limited range. This paper proposes an improved fuzzy PI controller. To reduce the speed overshoot, we adapt a control method that selects a proper CE range with respect to the load inertia variation. The proposed controller is applied to the vector controlled system with 2.2kW induction motor. Some simulation and experimental results are exhibited. With these results, we can easily find that proposed PI controller is more robust than the conventional fuzzy PI controller against the load inertia variation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.365-373
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• 1996

This paper presents the effects of rotor time constant variation and the on-line tuning algorithm of the rotor time constant. If the value of the rotor time constant is set incorrectly, the IFOC (Indirect Field Oriented Control)scheme exhibits deteriorated performance according to the wrong slip command. These variation effects of the rotor time constant are caused by the slip calculator where it is known that the rotor time constant play an important role in the aligned rotor flux. Using the two torque angles (stationary torque angle, rotating torque angle), the variation of the rotor time constant is identified, and the rotor time constant of the controller is tuned to the proper value of the machine. As the result, with the proposed algorithm, the dynamics of the deteriorated IFOC system, where the rotor time constant is varied, is improved. For the purpose of the validity of this proposed algorithm, the computer simulations and the experiments have been performed and the explanation of the results is presented. (author). refs., figs., tab.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.611-616
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• 2000

This paper presents a design method for the robust flight controller of a hyghly maneuvering aircraft subject to C.G variation. This method is based on LMI(Linear Matrix ZInequality) pole-placement design methodology for the polytopic models. Simulation results show that the proposed LMI-based pole-placement design methodology robustly yields uniform performance with adequate Flying Qualities (FQ) over the entire CG variation range.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1124-1136
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• 2017

Direct Power Control technique has become popular in the grid connected Voltage Source Converter (VSC) applications due to its simplicity, direct voltage vector selection and improved dynamic performance. In this paper, a direct method to determine the effect of voltage vector on the instantaneous active and reactive power variations is developed. An alternative Look Up Table is proposed which minimizes the commutations in the converter and results in minimum reactive power variation. The application of suggested table is established for Shunt Active Power Filter (SAPF) application. The Predictive Direct Power Control method, which minimizes apparent power variation, is further investigated to reduce commutations in converters. Both the methods are validated using 2 kVA laboratory prototype of Shunt Active Power Filters (SAPF).