• 소성∙가공
• /
• 제7권1호
• /
• pp.66-71
• /
• 1998

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the bonding conditions as well as the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding the normal pressure and the contact surface expansion are selected as process parameters governing the bonding conditions, in this study the critical normal pressure required for the local extrusion-the protrusion of virgin surfaces by the surface expansion at the interface-is obtained using a slip line method and is then used as a criteron for the bonding. A rigid plastic finite element method is used to analyze the steady state extrusion process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-cent to interface surface. The contact surface area ration and the normal pressure along the interface are calculated and compared to the critical normal pressure to check bonding. It is found that the model predictions are generally in good agreement with the experimental observations. The compar-isons of the extrusion pressure and interface profile by the finite element with those by experi-ments are also given.

• 한국정밀공학회지
• /
• 제18권7호
• /
• pp.179-185
• /
• 2001

Porthole die extrusion is profitable to manufacture long tube with hollow section. The material through portholes is gathered within chamber and welded under high pressure. This weldability which classifies the quality of tube product is affected by several variables and die shape. But, porthole die extrusion has been executed on the experience of experts due to the complicated die assembly and complexity of metal flow. Analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded. Therefore, the objective of this study is respectively to analyze the behavior of metal flow and to determine welding pressure of hot extrusion product according to the various billet temperature, bearing length and tube thickness by FE analysis and its results are compared with tube expanding tests.

• 조명전기설비학회논문지
• /
• 제18권5호
• /
• pp.169-173
• /
• 2004

본 논문은 전력계통의 전압 안정도 제약 문제를 해결하는데 고온 초전도 케이블을 적용하기 위한 기법을 제시하였다. 대전력계통의 유효 송전용량은 종종 전압 안정도 제약에 의해 결정된다. 기존의 초전도 케이블 응용 연구는 주로 도심지역의 고밀도 전력 수송 문제를 해결하는 대안으로 연구의 초점을 두어왔지만, 고온 초전도 케이블의 선로정수 개선효과를 이용하면 전압 안정도로 제약된 계통의 송전용량을 증가시킬 수 있어 그 응용 범위가 확대될 수 있다. 전압 안정도에 의한 최대 수송전력을 결정하는 데는 IPLAN에 의한 P-V곡선을 이용하였고, 대체 대상선로는 부하 증가시 무효전력 손실감도가 가장 큰 선로로 하였다. 결과의 타당성을 검증하기 위해 IEEE 14모선 계통을 사용하였으며, 적용결과 Case II는 70[%], Case III에서는 160[%]의 추가 수송 능력 증가를 가져올 수 있었다.

• 전력전자학회논문지
• /
• 제4권1호
• /
• pp.73-81
• /
• 1999

본 연구에서는 권선형 유도전동기의 회전자회로에 스위치모드 컨버터를 적용시킨 새로운 슬립전력 회수시스템을 제안하고 이를 분석한다. 제안된 시스템의 해석을 통해 적용된 컨버터의 듀티비에 의해 속도가 제어될 수 있으며, 동시에 기존 시스템의 몇가지 특성을 개선할 수 있음을 보인다. 특히 종래 시스템에서 주된 단점으로 되어 있는 저역률 및 전원전류의 고조파성분을 크게 개선할 수 있을 뿐만 아니라 선형적인 속도조절도 가능하다. 제안된 시스템의 타당성을 보이기 위해 이론 및 실험 결과를 제시하고 이를 설명한다.

• 전기학회논문지P
• /
• 제65권4호
• /
• pp.255-261
• /
• 2016

Korean Power System are operating a load shedding system to prevent voltage instability phenomenon caused by severe line contingencies. In order to apply the load shedding scheme should be selected a location, amount, delay time. Current load shedding system is load shedding amount that has been calculated in the steady-state analysis to load shed the total amount in first level, load shedding amount calculated in advance, it is possible to perform an unnecessary load shedding. In this paper, set a multi-level load shedding control strategy step-by-step selection of load shedding amount for the prevention of excessive load shedding. In addition, through a voltage resilience analysis of the power system by applying motor load ratio and sensitivity parameter to selection the multi level load shedding ratio and delay time. For this reason, to take advantage of the limit data of interchange power, by utilizing interface power flow data to set a multi-level load shedding control strategy for the stabilization of the Korean Power System.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
• /
• pp.5-8
• /
• 2008

본 연구는 지난 연구에 이어서 핸드피스 터빈 형상에 따른 유동특성 및 성능을 수치해석을 이용하여 연구하였다. 정상상태 방법 중 하나인 프로즌 로터 방식을 이용하여 노즐 중심선과 터빈 로터사이의 여러 각도에 따라 계산하였다. 평평한 모양, 오목한 형상, 갈매기 모양 등 3가지 터빈 로터 형상의 특성을 분석하였다. 추가적으로, 가장 성능이 좋은 로터 모양에 있어서 다른 반사각으로 계산을 하였다.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 1997년도 추계학술대회 학술발표 논문집
• /
• pp.143-153
• /
• 1997

At the on-line control method FLC(Fuzzy Logic Controller) is stronger to the disturbance than a classical controller and its overshoot of the initialized value is excellent. The fuzzy controller can do a proper control, though it doesn't know the mathematical model of the system or the parameter value. But to make the control rule of the fuzzy controller through an expert's experiance has a changes of the control system, the control rule is fixed, it can't adjust to the environment changes of the control system, the controller output value has a minute error and it can't convergence correctly to the desired value[1][2]. There are many ways to eliminate the minute error[3][4][5], but in this paper suggests EP-FNNIC(Fuzzy Neurla Network Intelligence Controller) intelligence controller which combines FLC with NN(Neural Network) and EP(Evolution Programming). The output characteristics of EP-FNNIC controller will be compared and analyzed with FLC. It will be showed that this EP-FN IC controller converge correctly to the desirable value without any error. The convergence speed, overshoot, rising time, error of steady state of controller of these two kinds also will be compared.

• 대한기계학회논문집A
• /
• 제23권7호
• /
• pp.1196-1204
• /
• 1999

adaption of the model predictions is highly desirable. In general, the width deviation at the head and tail ends of strip may be different from that of the steady state region. Therefore, the dynamic edger corrections can be used to compensate the width deviations which would otherwise occur. For the precise width control, the effect of edger roll gap and rolling conditions on the width deviation of head and tail ends of strip has been investigated and the effective method to decrease width deviation has been proposed. On-line application of dynamic edger control method in this study shows about 50% width compensation at the head end of the strip, and near perfect compensation at the tail end of strip.

• 대한기계학회논문집A
• /
• 제24권3호
• /
• pp.718-727
• /
• 2000

Nowadays, most passenger cars equipped with automatic transmissions use torque converter clutches to reduce fuel consumption, and recently the slip control scheme of torque converter clutches is widely studied for the expansion of the operating region of torque converter clutches and thus for the further improvement of the fuel economy of vehicles. In this study, the analysis of the torque converter clutch system including the line pressure control unit of the automatic transmission and the actuating hydraulic control unit of the torque converter clutch is performed, and a feedforward controller and a fuzzy logic controller for its slip control are proposed. Also, for the slip controller to use the grade resistance information during control, an observer-based grade resistance estimator is designed. The performance of the designed grade resistance estimator and the slip controller is verified by dynamic simulations, and the effect of the torque converter clutch slip control on the fuel economy is examined using a driving cycle simulation.

• International Journal of Control, Automation, and Systems
• /
• 제6권3호
• /
• pp.327-338
• /
• 2008

A fault tolerant control system design technique has been proposed and analyzed for managing performance degradation in the presence of multiple faults in actuators. The method is based on a control structure with a model reference reconfigurable control design in an inner loop and command input adjustment in an outer loop. The reduced dynamic performance requirements in the presence of different actuator faults are accounted for through different performance reduced (degraded) reference models. The degraded steady-state performances are governed by the reduced levels of command input. The reconfigurable controller is designed on-line automatically in an explicit model reference control framework so that the dynamics of the closed-loop system follow that of the performance reduced reference model under each fault condition. The reduced command input level is determined to prevent potential actuator saturation. The proposed method has been evaluated and analyzed using an aircraft example against actuator faults subject to constraints on the magnitude and slew-rate of actuators.