• Journal of Power Electronics
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• v.9 no.3
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• pp.499-506
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• 2009

In this paper, the initial pole-position estimation of a surface (non-salient) permanent magnet synchronous motor is mathematically analyzed and surveyed on the basis of simulation analysis, and developed for accurate servo motor drive. This algorithm is well carried out under the full closed-loop position control without any pole sensors and is completely insensitive to any motor parameters. This estimation is based on the principle that the initial pole-position is simply calculated by the reverse trigonometric function using the two feedback currents in the full closed-loop position control. The proposed algorithm consists of the predefined reference position profile, the information of feedback currents, speed, and relative position, and the reverse trigonometric function for the initial-pole position estimation. Comparing with the existing researches, the mathematical analysis is introduced to get a more accurate initial pole-position of the surface permanent magnet motor under the closed-loop position control. It is found that the proposed algorithm can be easily applied in servo drive applications because it satisfies the following user's specifications; accuracy and moving distance.

• Proceedings of the KIEE Conference
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• 1982.07a
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• pp.48-51
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• 1982

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.36-39
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• 2006

To evaluate the effect of groundwater flow on the outlet temperature of a geothermal heat pump, 3 dimensional numerical simulations are performed considering both groundwater flow and pipe flow in the U-tube using TOUGHS, The present study involved the following 4 simulation cases (1) no groundwater flow, (2) slow groundwater flow (hydraulic conductivity: $1.0{\times}10^{-9}m/s)$, (3) fast groundwater flow (hydraulic conductivity, $1.0{\times}10^{-7}m/s$), and (4) groundwater flow varying with the depth (hydraulic conductivity: $1.0{\times}10^{-7}-1.0{\times}10^{-10}m/s$). The effect of groundwater flow on the outlet temperature is significant where hydraulic conductivity of aquifer is $1.0{\times}10^{-7}m/s$. Where hydraulic conductivity of aquifer is $1.0{\times}10^{-10}m/s$, however, that effect is negligible.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.186-194
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• 2001

To meet the challenge of testing increasingly complex automotive control systems, the real-time hardware-in-the-loop(HIL) simulation technology has been developed. In this paper, a strategy for evaluation of semiactive suspension systems using real-time HIL simulation is presented. A multibody vehicle model is adopted to simulate vehicle dynamic motions accurately. Accuracy of the vehicle simulation results is compared to that of the real vehicle field test and proven to be very accurate. The controller and stepping motor to adjust semi-active damper stage are equipped as external hardwares and connected to the real-time computer which has vehicle dynamic model. Open and closed loop test methods are used to evaluate a controlled suspension system and the system's operations are verified it is found that the proposed evaluation methods can be used well for the verification of semi-active suspension systems.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1465-1469
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• 2003

In general satellite verification process, the AOCS (Attitude & Orbit Control Subsystem) should be verified through several kinds of verification test which can be divided into two major category like FBT (Fixed Bed Test) and polarity test. And each test performed in different levels such as ETB (Electrical Test Bed) and satellite level. The test method of FBT is to simulate satellite dynamics with sensors and actuators supported by necessary environmental models in ETB level. The VDS (Vehicle Dynamic Simulator) try to make the real situation as possible as the on-board processor will undergo after launch. The purpose of FBT test is to verify that attitude control logic function and hardware interface is designed as expected with closed loop simulation. The VDS is one of major equipments for performing FBT and consists of software and hardware parts. The VDS operates in VME environments with target board, several commercial boards and custom boards based on the VxWorks real time operating system. In order to make time synchronization between VDS and satellite on-board processor, high reliable semaphore was implemented to make synchronization with the interrupt signal from on-board processor. In this paper, the real-time operating environment used on VDS equipment is introduced, and the hardware and software configurations of VDS summarized in the systematic point of view. Also, we try to figure out the operational concept of VDS and AOCS verification test method with close-loop simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.13-19
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• 2008

In this paper, we propose a new CL-OSTBC (Closed Loop Orthogonal Space-Time Block Code) scheme for four transmit antennas and compare the scheme with existing closed loop schemes on the performance of BER (Bit Error Rate). In the proposed scheme, a transmitter receives channel feedback information and combines modulated symbols by the symbol combiner, and transmits the symbols encoded by the space-time block encoder. As a result, the proposed scheme achieves full-rate and maximal channel gains by more efficient utilization of the channel feedback information. Moreover, the scheme can reduce computation complexity by using a linear detector. Simulation results on the BER performance show that the proposed CL-OSTBC scheme outperforms existing CL-OSTBC schemes.

• Proceedings of the Korea Society for Simulation Conference
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• 2000.11a
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• pp.49-55
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• 2000

고객들의 주문에 대하여 오더픽킹을 수행하여 출하하는 물류센터에서는 매일 여러 공급사로부터의 다양한 입고물량이 창고 내에서 신속, 정확하게 주문에 따라 고객별로 픽킹되어 출하트럭에 상차되어야 한다. 이때 인테리어 가구류를 취급하는 물류센터의 경우에는 출하팔렛에 적재시 특정한 품목순서에 따라 적재해야 하는 제약조건 때문에 이를 위한 팔렛 재처리 작업이 필요하게 된다. 본 논문은 Closed Loop형 궤도상을 움직이는 대차시스템을 이용해 픽킹을 수행하는 크로스도킹 물류센터에서 이러한 팔렛 재처리작업과 픽킹작업을 포함한 운영정책들의 성과를 컴퓨터 시뮬레이션으로 평가, 분석한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1170-1178
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• 2007

Repeated hardware tests and tuning, investing cost and time, are usually required to assure a satisfactory performance of the suspension seat. In this study, an EILS(ECU-in-the-loop) method was proposed to develop a controller for a semi-active suspension seat with a MR(magneto-rheological) damper. EILS system was developed using a real-time seat dynamics model communicating with ECU hardwares under a closed loop environment utilizing Matlab/Simulink and xPC $TargetBox^{TM}$. A sky-hook based control algorithm with optimized damping coefficients was verified to reduce the energy consumption and to improve the vibration response performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.1
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• pp.38-43
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• 2011

This paper presents the improvement of start-up characteristic of sensorless controlled IPMSM(Interior Permanent Magnet Synchronous Motor) with SMO(Sliding Mode Observer). It is difficult to utilize the rotor position information at starting point for the back EMF estimation based sensorless control. For this reason, open loop control is normally used during start-up period. However, changing from open loop to closed loop control might bring a problem on the transient characteristics for difference load conditions. To solve this problem, we add another rotor angle controller. Simulation results and experimental results are presented to verify proposed method.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1638-1646
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• 2008

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 2-D finite element analysis, ANSYS, was employed to evaluate the temperature distribution on the borehole cross section involving HDPE pipe/grout/soil formation to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system which is equipped with a thermally insulating latice in order to reduce thermal interference between the inflow and outflow pipes. In addition, a 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of grout's thermal properties, rate of circulation pump, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.