• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.715-722
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• 1998

A large electric system of a vacuum circuit breaker(VCB) has been studied for the electro-thermal analysis by finite element methods. Since the heat generation in VCB causes not only energy loss but deterioration of the VCB system with oxidization of parts, the overheating of the system must be prevented. For the analysis, a finite element formulation is derived for both electric analysis and thermal analysis that are coupled together. Two sets of formulations are uncoupled after finite dimensional approximation. First, the electric potential is obtained for the entire field and scaled to the given electric current. The electric field obtained is then used to calculate the heat generation in the VCB system including contacts and connections for the calculation of the temperature distribution in the entire domain. The finite element analysis is carried out to study the effect of shapes and locations of contacts and connections. From the results, the existing VCB has been modified to enhance its capacity with reduction of heat generation and temperature elevation.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.863-868
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• 2011

This paper presents a method to achieve a synchronous positioning objective for a dual-cylinder electro-hydraulic system with friction characteristics. The control system consists of a VSC (Variable Structure Controller) for each of the hydraulic cylinders and a PID (Proportional-Integral-Derivative) feedback controller. The PID controller is used for controlling the non-synchronous error generated by both cylinders when motion synchronization is carried out. To enhance the position-tracking performance of the individual cylinders friction characteristics is modeled in model, based on the estimated friction force. The simulation and experimental results show that the proposed method can effectively achieve the objective of position synchronization in the dualcylinder electro-hydraulic system, with maximum synchronization error with ${\pm}2\;mm$.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.974-978
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• 1991

Electro-pneumatic valve is an electro-mechanical device which converts electric signal into pneumatic flow mu or pressure. A measurement of dynamic response time is very important to evaluate valve performance. Dynamic response time of electro-pneumatic valve has a variation accordance with valve types, operating way and test standard. In this study, automatic measurement system of dynamic response time is composed based on test condition of dynamic response time test standard(CETOP, JIS). Also, in this study test pressure variation characteristics accordance with variation of solenoid excitation power, and we developed dynamic response measurement system enable to compare of and analyze these two characteristics.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1873-1874
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• 2008

본 연구는 근접상황의 선박 간 충돌회피시스템을 개발하기 위한 연구로서 근거리 조우상황에서 발생하는 선박충돌사고를 감소시키기 위한 선박충돌회피 설계방법을 제시한다. 이 설계모델은 레이다(Radar), 선박자동식별장치(AIS : Automatic Identification System)와 자동조타장치(Autopilot)를 충돌회피시스템에 연계하여 선박 간 충돌 사고를 사전에 예측하고 자동회피 방법을 제안한 것이다.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.60-67
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• 2001

As a method of variable valve train(VVT), Electro-Mechanical Valve(EMV) has been studied. Compared with conventional VVT system, the EMV system has a relatively simple structure. The system has two electromagnets, springs and an armature. The system can be operated by reciprocal action between armature and two electromagnets. And, the operating event can be controlled by electrical signal from controller. Therefore, reduction of emission and fuel consumption can be achieved through valve event control at each engine operating condition. In this study, characteristics of EMV system were investigated by simulations and experiments. The results of simulation and experiment show that the core shape and material characteristics are dominant parameters on magnetic force and delay time. In order to apply the system to commercial engine, it has a compact size and high stiffness springs(50N/mm) to increase the valve speed. Because of high valve seating velocity, loud noise and high impact force generated, which can lead to reduction of actuator durability. Therefore, further research is required to reduce valve seating velocity.

• Journal of Drive and Control
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• v.19 no.1
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• pp.51-61
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• 2022

This paper presents a model-free system based on a framework of a backstepping sliding mode control (BSMC) with a radial basis function neural network (RBFNN) and adaptive mechanism for electro-hydraulic systems (EHSs). First, an EHS mathematical model was dedicatedly derived to understand the system behavior. Based on the system structure, BSMC was employed to satisfy the output performance. Due to the highly nonlinear characteristics and the presence of parametric uncertainties, a model-free approximator based on an RBFNN was developed to compensate for the EHS dynamics, thus addressing the difficulty in the requirement of system information. Adaptive laws based on the actor-critic neural network (ACNN) were implemented to suppress the existing error in the approximation and satisfy system qualification. The stability of the closed-loop system was theoretically proven by the Lyapunov function. To evaluate the effectiveness of the proposed algorithm, proportional-integrated-derivative (PID) and improved PID with ACNN (ACPID), which are considered two complete model-free methods, and adaptive backstepping sliding mode control, considered an ideal model-based method with the same adaptive laws, were used as two benchmark control strategies in a comparative simulation. The simulated results validated the superiority of the proposed algorithm in achieving nearly the same performance as the ideal adaptive BSMC.

• Journal of Drive and Control
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• v.16 no.2
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• pp.15-21
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• 2019

In this study, the maximum system efficiency of the electro-hydrostatic actuators was experimentally investigated, where small size external gear pumps with volumetric displacement under 1.3 cc/rev were combined with a 400W servomotor as the prime mover. Since the efficiency data of the servomotor, gear pumps and hydraulic cylinder were not provided by the suppliers, experimental apparatuses for their efficiency measurement were extra built up. When a gear pump with a volumetric displacement of 1.27cc/rev was used on an electro-hydrostatic actuator system, the maximum system efficiency was not higher than 70%. This was because the most effective operation ranges of the motor and pump did not coincide each other. In order to match their operation ranges as one of the most crucial design factors, a speed reduction mechanism can be used, such as a timing belt. It was shown in the study that the maximum system efficiency could be increased from 70% to 76% in that way.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.346-352
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• 2007

In this paper, we present an analysis of dynamic characteristics of an electromagnetic actuator for circuit breakers. It is indispensable to simultaneously analyze magnetic, electric, and mechanical phenomena to obtain the dynamic characteristics of the electromagnetic actuator because these phenomena are closely related to each other in an electromagnetic actuator system. The magnetic equations are computed by using the finite element method (FEM). The electric equations and the mechanical equations, which include the time derivative terms, are calculated by using the time difference method (TDM). The calculated results, which have been obtained by means of the FEM and the TDM, are presented with experimental data.

• Polymer(Korea)
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• v.32 no.4
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• pp.334-339
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• 2008

Recently electro spinning is a widely used simple technique to prepared micro- to nanometer-sized fiber of various polymers. In general, a normal multiple-nozzle electro spinning system has been difficult to achieve high production-rate fabricating micro/nanofibers due to the interference of electric field between individual nozzles in the process. To reduce the interference effect of electric field between nozzles, we developed a multi-nozzle electrospinning system supplemented with auxiliary electrodes. Poly($\varepsilon$-carprolactone)(PCL), which has good mechanical property and biocompatibility, was electrospun by the multi-nozzle electro spinning system. Electrospinnability, product rate, and size uniformity of spun fibers for the system with and without auxiliary electrodes were characterized. As a result, the multi-nozzle electrospinning system supplemented with auxiliary electrodes provides excellently stable processability and showed high mass productivity of PCL-nanofibers relative to a normal multi-nozzle electro spinning system.

• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.58-67
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• 2020

In this study, finite element fatigue analysis combined with a fatigue correlation factor is proposed to predict the bending fatigue life of a gear in an electro-mechanical aircraft actuator. First, stress-life curves are obtained for the gear material via a round bar fatigue test. Subsequently, stochastic stress-life (P-S-N) curves are derived for 50% and 1% failure probabilities, separately. The curves are applied to the fatigue analysis model of a single gear tooth, and the effect of the fatigue correction factor is analyzed. The analytical P-S-N curves reflecting the fatigue correction factor matched the experimental data. This shows that the analytical fatigue life is reliable and that the analysis technique is effective.