• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.369-375
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• 2020

Distribution energy resources have been increasing in recent years. However, output power is limited for distribution network stability. This study proposes an active distribution network that can reconfigure distribution lines by using an active phase controller. A conventional distribution network has a fixed structure, whereas an active distribution network has a variable structure. Therefore, the latter can increase the output power of distribution energy resources and decrease the overload of distribution line facilities. An active phase controller has two operation modes for minimizing circulating current during dynamic reconfiguration. In this study, voltage and current control algorithms are proposed for active phase controllers. The simulation of the proposed methods for active phase controllers is performed using PSIM software.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.1
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• pp.6-12
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• 2020

In recent years, the demand for the distribution of energy resource has been increasing. However, the output power is limited by the stability of the distribution network. This study proposes an active distribution network that can reconfigure the distribution line using an active phase controller. The conventional distribution network has a fixed structure, whereas the proposed active distribution network has a variable structure. Therefore, the active distribution network can increase the output power of the distribution energy resource and reduce the overload of distribution line facilities. The active phase controller has two operation modes to minimize the circulating current during dynamic reconfiguration. In this study, the voltage and current control algorithms are proposed for the active phase controller. The proposed method for the active phase controller is simulated via PSIM simulation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1123-1126
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• 2005

This paper introduces the key features of NCS (Network based Control System), which is quite a new concept in the industrial automation market. Two control systems "DCS" and "PLC" have been recognized as control systems used for process and factory automation during the past decades. However, the market requires more complex functionality, such as monitoring and operation, alarm handling and notification from remote locations using the Web or e-mail. Besides enhancing functionality, interoperability between each device and system is highly required since network and engineering tools provided by many vendors do not cooperate with each others, so that lots of conversion, reconfiguration and reprogramming are required when expanding systems. NCS can meet this requirement, installing leading-edged IT technology using international standards for network and engineering environment. NCS, which is a harmony of web functionality, networkability and a reliable control function, enables information integration and responding to the market's requirements with agility and high reliability.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.85-94
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• 1999

Reconfiguration, expansion, or new establishment of FMS requires the availability of a shop floor control (SFC) system relevant to the FMS since it is closely related with the hardware component of FMS. Due to the expensive cost of its development, significant research efforts have been made to develop an SFC system that is reusable. This paper presents Abstract Machine Tool (AMT) approach applied to develop an SFC sytem that is reusable without additional programming. The AMT model enables us to design the SFC system independently of the hardware-dependent attributes of euqipment; an AMT models a workstation by abstraction and presents an equipment-independent interface to machining cell controller. Specifically, we describe how we formalize the interfaces among equipment in order to build an AMT and how we design the machining cell control software based on AMT models. We also present MACHINIST the machining cell control system for IAE-FMS plant as an implementation example.

• International Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.1-8
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• 2016

The improvements in high performance and agility of modern fighter aircraft have led to improvements in survivability as well. Related to these performance increases are rapid response and adequate deflection of the control surfaces. Most control surface failures result from the failure of the actuator. Therefore, the failure and behavior of the actuators are essential to both combat aircraft survivability and maneuverability. In this study, we investigate the effects of flaperon actuator failure on flight maneuvers of a supersonic aircraft. The flight maneuvers were analyzed using six degrees of freedom (6DOF) simulations. This research will contribute to improvements in the reconfiguration of control surfaces and control allocation in flight control algorithms. This paper compares the results of these 6DOF simulations with the horizontal tail actuator failures analyzed previously.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.51-60
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• 2020

This study designs and analyzes satellite formation flying concepts for the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE) mission, that will observe the near-Earth space environment using four nanosats. To meet the requirements to achieve the scientific objectives of the SNIPE mission, three formation flying concepts are analyzed: a cross-shape formation, a square-shape formation, and a cross-track formation. Of the three formation flying scenarios, the cross-track formation scenario is selected as the final scenario for the SNIPE mission. The result of this study suggests a relative orbit control scenario for formation maintenance and reconfiguration, and the initial relative orbits of the four nanosats meeting the formation requirements and thrust limitations of the SNIPE mission. The formation flying scenario is validated by calculating the accumulated total thrust required for the four nanosats. If the cross-track formation scenario presented in this study is applied to the SNIPE mission, it is expected that the mission will be successfully accomplished.

• Journal of KIISE:Information Networking
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• v.33 no.2
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• pp.156-164
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• 2006

The SCTP (Stream Control Transmission Protocol) implementation with the DAR (Dynamic Address Reconfiguration) extension is called the mSCTP (Mobile SCTP) that is proposed recently for mobility support in transport layer. The mSCTP does not satisfy short handover latency for real-time applications and it has no specific handover decision mechanisms. In this paper, we propose fast handover schemes for mobile nodes that are moving into different subnet using pre-acquisition RA (Router Advertisement) and L3 trigger for improving handover performance. Furthermore, we introduce three specific methods which are RA cache, FMIPv6 (Fast Handovers for Mobile IPv6) and dual interface and how proposed scheme can be interoperated with handover process respectively. Finally, we show two experimental results which are the mSCTP and the mSCTP using FMIPv6 on Linux platforms. Experimental results show that handover performance is improved with reducing the time of receiving RA which takes most of total handover latency.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.12
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• pp.637-644
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• 2004

This paper proposes an expert system with the knowledge learning capability which can enhance the safety and effectiveness of substation operation in the automated substation as well as existing substation by inferring multiple events such as main transformer fault, busbar fault and main transformer work schedule under multiple inference mode and multiple objective mode and by considering totally the switch status and the main transformer operating constraints. Especially inference mode includes the local minimum tree search method and pattern recognition method to enhance the performance of real-time bus reconfiguration strategy. The inference engine of the expert system consists of intuitive inferencing part and logical inferencing part. The intuitive inferencing part offers the control strategy corresponding to the event which is most similar to the real event by searching based on a minimum distance classification method of pattern recognition methods. On the other hand, logical inferencing part makes real-time control strategy using real-time mode(best-first search method) when the intuitive inferencing is failed. Also, it builds up a knowledge base or appends a new knowledge to the knowledge base using pattern learning function. The expert system has main transformer fault, main transformer maintenance work and bus fault processing function. It is implemented as computer language, Visual C++ which has a dynamic programming function for implementing of inference engine and a MFC function for implementing of MMI. Finally, it's accuracy and effectiveness is proved by several event simulation works for a typical substation.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.41-41
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• 2003

Satellite formation flying is currently an active area of research in the aerospace engineering. There are many categories for this research such as the determination of initial conditions, formation keeping, configuration and reconfiguration. In this study, a tracking controller using sliding mode techniques is designed to control a satellite for the satellite formation flying. In general, Hill's equations are used to describe the relative motion of the follower satellite with respect to the leader satellite. But, the modified Hill's equations considering J2 perturbation were used for the design of sliding mode controller. Sliding mode control law causes the chattering phenomenon because it is a discontinuous control. Dead-zone was used to avoid the chattering. The Extended Kalman filter was applied to estimate the state vector based on the measurements of relative distance and velocity between two satellites.

• Journal of Astronomy and Space Sciences
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• v.25 no.3
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• pp.255-266
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• 2008

The current paper presents application of a new analytic solution in general relative motion to spacecraft formation flying in an elliptic orbit. The calculus of variations is used to analytically find optimal trajectories and controls for the given problem. The inverse of the fundamental matrix associated with the dynamic equations is not required for the solution in the current study. It is verified that the optimal thrust vector is a function of the fundamental matrix of the given state equations. The cost function and the state vector during the reconfiguration can be analytically obtained as well. The results predict the form of optimal solutions in advance without having to solve the problem. Numerical simulation shows the brevity and the accuracy of the general analytic solutions developed in the current paper.