• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1317-1326
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• 2008

This paper presents a self.levelling system for a mass, which undergoes a severe acceleration, with integrated displacement feedback control. After a general description of such a system, theoretical analysis is investigated to design an active control device. The self-levelling system can be used to reduce the "quasi-static" deflection while isolating the "dynamic" vibration. A computer simulation model of 45 kg with two air spring mounts is considered to predict the performance of the control system. Important control parameters were acquired to meet the requirement of the system. The results showed the controller can reduce the displacement of the mass to the level of about 1/5 after control. Thus the self-levelling system can be applied usefully to reduce the displacement of a mass which experiences a high g dynamics.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.504-507
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• 2005

This paper presents a self-levelling system for a mass, which undergoes a severe acceleration, with integrated displacement feedback control. After a general description of such a system, theoretical analysis is investigated to design an active control device. That is, the self levelling system is used to reduce the 'static' deflections while isolating the 'dynamic' vibration. A computer simulation model of 45 kg with two air spring mounts is considered to predict the performance of the control system. The results showed the controller can reduce the mass's displacement to the level of 1/3-1/5. Thus the self-levelling system can be applied usefully to reduce the dispalcement of a mass which experiences a high g dynamics.

• 한국측량학회지
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• 제29권1호
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• pp.81-89
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• 2011

기존의 우리나라의 지상중력 자료는 지역적으로 편향된 분포를 나타내며, 특히 산악지역에서는 그 분포가 현저히 떨어진다는 문제점이 존재하였다. 이러한 문제점은 GPS/Levelling 자료에서도 나타나며 이로 인하여 지오이드 정확도 향상에 한계가 있었다. 그러나 2008년부터 국토지리정보원에서 수행하고 있는 통합기준점 및 수준점 중력측량사업에서 새로운 중력 자료 및 GPS/Levelling 자료를 획득하였으며, 특히 이러한 자료들은 기존의 중력 및 GPS/Levelling 자료에 비해 월등한 분포와 정밀도를 나타내기 때문에 우리나라 지오이드 모델의 정밀도를 개선하는 기본 자료로 활용될 수 있다. 본 연구에서는 품질이 검증된 기존 자료와 새롭게 획득된 중력 자료를 포함하여 지오이드 모델을 구축하였다. 구축된 지오이드 모델의 정밀도는 새롭게 획득된 927점의 GPS/Levelling 자료와 비교한 결과 약 5.29cm로 나타났으며, 합성지오이드의 적합도 및 정밀도는 각각 약 2.99cm와 3.67cm로 산출되었다. 본 연구를 통하여 산출된 최신 지오이드 모델은 새로운 중력 자료를 포함하기 전에 구축된 모델에 비하여 우리나라 전역에서 약 27% 정도 정밀도가 향상되었으며, 특히 현저히 낮은 분포를 보이던 강원 및 경상지역에서는 중력자료의 업데이트에 의하여 약 42%의 정밀도 향상이 이루어 졌다. 2010년에 통합기준점 사업 및 수준점 측량사업을 통하여 약 4,000여점의 중력 자료와 300여점의 GPS/Levelling 자료가 획득되었기 때문에 향후 본 자료들을 함께 활용한다면 지오이드 모델 정밀도의 향상과 더불어 객관적으로 정밀도 검증이 가능할 것으로 판단된다.

• Journal of Biosystems Engineering
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• 제27권2호
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• pp.79-88
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• 2002

This study was conducted to develop system for high speed rice transplanting machines. The control system includes a sensor detecting the tilt angle of the seedling bed, a micro-controller and a hydraulic system consisting of a double acting cylinder, a four-way three-position solenoid valve, a relief valve and a hydraulic pump. The levelling system shared the pump with the existing steering control, resulting in a tandem center circuit for the steering and levelling control systems. Using the input signal from the sensor, the micro-controller determined and generated the output signal to control the cylinder through the solenoid valve to keep the seedling bed always parallel to the water surface regardless of soil unevenness during the transplanting operations. Both an ON/OFF and a PWM control schemes were tested. When the flow rate was more than 1 ι/min in the ON/OFF control, the system showed unstable rolling. However, in the PWM control, the system worked stably although the flow rate was more than 1 ι/min. The PWM control showed a better performance when a large difference between the angle and the dead band of the control system occurred. The characteristics of tile system response to given tilt angles were predicted by a computer simulation. Both the ON/OFF and the PWM control systems worked well providing that the operating and waiting times were properly adjusted.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.42-48
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• 2000

This paper is concerned with a simulation-based process design for the tension levelling of metallic strips based on the elasto-plastic finite element analysis with reduced integration and hourglass control. The tension levelling process is performed to elongate the strip plastically in combination of tensile and bending strain by a controlled manner so that all longitudinal fibers in the strip have an approximately equal amount of length and undesirable strip shapes are corrected to the flat shape. The analysis deals with a method for calculating the quantitative level of the curl to investigate the roll arrangements and intermesh suitable to elimination of the curl. The analysis provides the information about the intermesh effect on the amount, the tension effect and distribution of the strain as well as the stress in order to determine the amount of elongation for correction of the irregular shape. The desired elongation is referred to determine the number of work rolls and the value of tension. Especially, the analysis investigates tile effect of the mesh size in the non-steady state finite element analysis on the amount and distribution of the strain.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.651-656
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• 2000

This paper describes the optimal sizing of each component using computer simulation and presents the efficient operating scheme of series HEV using hardware simulator the equivalent system. As the sizing method of components have been experimental and empirical it is needed to spend much time and development cost. however the results of computer simulation will set the optimal sizing of components in short time. There are two type of driving control power-tracking mode and load-levelling mode in series HEV. This paper presents that series HEV be operated in the load-levelling mode which is more efficient that power-tracking mode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1059-1062
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• 1998

This paper which can simulate FRIENDS(Flexible Reliable Intelligent Electrical eNergy Delivery System) model of distribution electrical system presents a new algorithm. In the operation of FRIENDS model, dispersed energy storage(DES) systems have an important role. We can use the active and reactive power of DES to control customer's voltage. In this, the former means load levelling operation and the later means voltage control operation of DES. We focus our research on load levelling operation of DES. We develope an algorithm to get an optimal capacity and operation schedule of DES and then apply it to the FRIENDS model. The results show the effectiveness of the proposed method.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.101-106
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• 2006

The geoidal undulations are needed for determining the orthometric heights from the Global Positioning System GPS-derived ellipsoidal heights. There are several methods for geoidal undulation determination. The paper presents a method employing a simple architecture Two Layer Multiquadric-Biharmonic Artificial Neural Network (TLMB-ANN) to approximate an area of 4200 square kilometres quasigeoid surface with GPS-levelling data. Hardy’s Multiquadric-Biharmonic functions is used as the hidden layer neurons’ activation function and Levenberg-Marquardt algorithm is used to train the artificial neural network. In numerical examples five surfaces were compared: the gravimetric geometry hybrid quasigeoid, Support Vector Machine (SVM) model, Hybrid Fuzzy Neural Network (HFNN) model, Traditional Three Layer Artificial Neural Network (ANN) with tanh activation function and TLMB-ANN surface approximation. The effectiveness of TLMB-ANN surface approximation depends on the number of control points. If the number of well-distributed control points is sufficiently large, the results are similar with those obtained by gravity and geometry hybrid method. Importantly, TLMB-ANN surface approximation model possesses good extrapolation performance with high precision.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.251-253
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• 1989

The Battery Storage System (BSS) has been used in foreign country for Load Levelling, Flicker Compensation, Load Frequency Control, etc. because it has easy application characteristics compared to the other storage system such as the Pumped Hydro System, Compressed Air System, etc.. In this paper, the application field and available capacity of BSS is outlined in Korea.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.100-107
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• 2001

The main goals of the automotive suspension systems are to isolate roadway unevenness from the tire and to improve vehicle stability. To overcome the performance limitation of the passive systems the active systems which completely replace the passive spring and damper elements with a force generating actuator has been studied. However, application of the system has been limited because it has required a significant amount of power. Recently, alternative systems which retain passive elements but include active elements have been developed to reduce the power required. Those systems are mostly focused on the control system which compresses the spring-damper directly. In this study, a new type of power efficient control system which makes the spring-damper unit slide in side way is studied. After constructing the control system including dynamic modeling and motion control, two types of alternative control systems are compared in view of power consumption and dynamic attitudes such as roll responses as well as heave responses. Also, a half car bond graph model is developed to show clearly the significant differences in performances between two control systems.