• The Transactions of the Korea Information Processing Society
• /
• v.7 no.3
• /
• pp.799-807
• /
• 2000

In this paper, object replication Client/server under distributed computing system is design and implementation. Today many end-users have a computer communication by using internet in the distributed system of client/server. If many users request services to a specific remote server, the server should have got a overhead for hat service processing, delayed the speed for replay, and bring a bottleneck in communication network. Therefore object replication method was proposed to solve this problems. The growth of internet works and distributed applications has increased the need for large scale replicated systems. However, existing replication protocols do not address scale and autonomy issues adequately. Further, current application protocol require consistency of different levels, and therefore should be the selection function of consistency in them, in order to have particular semantics of each level. In this paper, server overhead and bottleneck happening in remote procedure call be using server object replication. Therefore access transparency can be improved by sharing object duplicately. So it will Keep up with the consistency within the replicated objects.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.302-308
• /
• 2006

We introduce the concept of a remote distributed embedded system to integrated fieldbus based control systems in internet/Intranet. As a result fieldbus systems are opened up for remote monitoring, remote maintenance, and remote control applications using state of the art Web-technology. This paper addresses the design of a remote distributed embedded system using Internet and CAN for multi-Induction motor of Building and Industrial field. The fieldbus used the CAN based networked intelligent multi-motor control system using DSP2812 microprocessor. To build such a system, the TCP/IP-CAN Gateway which convert a CAN protocol to TCP/IP protocol and vice verse, was designed. A experimental simulation system consists of a TCP/IP-CAN Gateway in remote place and a command PC ti be connected ti Ethernet.

• International Journal of Safety
• /
• v.5 no.2
• /
• pp.6-11
• /
• 2006

The time delay in servo control on LonWorks/IP Virtual Device Network (VDN) is highly stochastic in nature. LonWorks/IP VDN induced time delay deteriorates the performance and stability of the real-time distributed control system and hinders an effective preventive and predictive maintenance. Especially in real-time distributed servo applications on the factory floor, timely response is essential for predictive and preventive maintenance. In order to guarantee the stability and performance of the system for effective preventive and predictive maintenance, LonWorks/IP VDN induced time delay needs to be predicted and compensated for. In this paper position control simulation of DC servo motor using Zero Phase Error Tracking Controller (ZPETC) as a feedforward controller, and Internal Model Controllers (IMC) based on Smith predictor with disturbance observer as a feedback controller is performed. The validity of the proposed control scheme is demonstrated by comparing the IMC based on Smith predictor with disturbance observer.

• Journal of Information Processing Systems
• /
• v.13 no.6
• /
• pp.1602-1612
• /
• 2017

Since rapidly disseminating of Internet of Things (IoT) as the new communication paradigm, a number of studies for various applications is being carried out. Especially, interest in the smart medical system is rising. In the smart medical system, a number of medical devices are distributed in popular area such as station and medical center, and this high density of medical device distribution can cause serious performance degradation of communication, referred to as the coexistence problem. When coexistence problem occurs in smart medical system, reliable transmitting of patient's biological information may not be guaranteed and patient's life can be jeopardized. Therefore, coexistence problem in smart medical system should be resolved. In this paper, we propose a distributed coexistence mitigation scheme for IoT-based smart medical system which can dynamically avoid interference in coexistence situation and can guarantee reliable communication. To evaluate the performance of the proposed scheme, we perform extensive simulations by comparing with IEEE 802.15.4 MAC protocol which is a traditional low-power communication technology.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.17 no.2
• /
• pp.115-121
• /
• 2022

This paper proposes a distributed model predictive formation control algorithm for a group of unmanned ground vehicles (UGVs) with guaranteeing collision avoidance between UGVs. Generally, the model predictive control based formation control has a disadvantage in that it takes a long time to compute control inputs when considering collision avoidance between UGVs. In this paper, in order to overcome this problem, the formation control algorithm is implemented in a distributed manner so that it could be individually controlled. Also, a collision-avoidance method considering real-time is proposed. The proposed formation control algorithm is implemented based on robot operating system (ROS), open source-based middleware. Through the various simulation tests, it is confirmed that the formation control of five UGVs is successfully performed while avoiding collisions between UGVs.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.2
• /
• pp.57-68
• /
• 2016

In this study, we present the modern hybrid system based power generation for electric vehicle applications. We describe the hybrid structure of modified current source based DC - DC converters used to extract the maximum power from Photovoltaic (PV) and Fuel Cell system. Due to reduced dc-link capacitor requirement and higher reliability, the current source inverters (CSI) better compared to the voltage source based inverter. The novel control strategy includes Distributed Maximum Power Point Tracking (DMPPT) for photovoltaic (PV) and fuel cell power generation system. The proposed DC - DC converters have been analyzed in both buck and boost mode of operation under duty cycle 0.5>d, 0.5<d<1 and 0.5<d for capable electric vehicle applications. The proposed topology benefits include one common DC-AC inverter that interposes the generated power to supply the charge for the sharing of load in a system of hybrid supply with photovoltaic panels and fuel cell PEM. An improved control of Direct Torque and Flux Control (DTFC) based induction motor fed by current source converters for electric vehicle.In order to achieve better performance in terms of speed, power and miles per gallon for the expert, to accepting high regenerative braking current as well as persistent high dynamics driving performance is required. A simulation model for the hybrid power generation system based electric vehicle has been developed by using MATLAB/Simulink. The Direct Torque and Flux Control (DTFC) is planned using Xilinx ISE software tool in addition to a Modelsim 6.3 software tool that is used for simulation purposes. The FPGA based pulse generation is used to control the induction motor for electric vehicle applications. FPGA has been implemented, in order to verify the minimal error between the simulation results of MATLAB/Simulink and experimental results.

• The Journal of the Korea Contents Association
• /
• v.10 no.3
• /
• pp.141-148
• /
• 2010

The aim of this paper is to propose a communication middleware which makes it possible to easily and efficiently develop the networking support for multi-user applications. Even though existing middleware and development tools provides lots of functionalities to realize distributed applications, they are purely low-level services passing the most development efforts to developers, or too specialized for a specific application. It brings a challenging issue of how the middleware supports general and efficient high-level mechanisms. To meet different networking and interaction requirements of multi-user applications, we propose various schemes to provide the communication architecture, the user membership management, the content transmission mechanism and the event management. Our middleware provides developers with application-level APIs and configuration files so that the different interaction requirements of a multi-user application can be easily handled in the developers' point of view.

• The KIPS Transactions:PartA
• /
• v.15A no.2
• /
• pp.111-118
• /
• 2008

With the advance in mobile communication systems, the need for distributed applications running on multiple mobile devices also grows gradually. As such applications are subject to H/W failures of the mobile device or communication disruptions, compared to the traditional applications in fixed networks, it is crucial to develop any recovery mechanism suitable for them. For this, checkpointing is widely used to restart interrupted applications. In this paper, we devise an efficient checkpointing method that adopts the software agent executed at the mobile support station. The agent, called the checkpointing agent, is aimed at supporting the concept of rollback-distance (R-distance) that bounds the maximum number of roll-backed local checkpoints. By means of the R-distance, our method can prevent undesirable domino effects and heavy checkpoint overhead, while providing high flexibility in checkpoint creation.

• Journal of KIISE:Computing Practices and Letters
• /
• v.8 no.1
• /
• pp.25-35
• /
• 2002

Many multimedia presentation applications involve retrieval of objects from more than one collaborating server. Presentations of objects from different collaborating servers might be interdependent. This implies that objects should be retrieved from remote servers and delivered continuously according to given time constraints. Such applications need an estimate of the avaliable network resources to each of the collaborating servers and local system resources in order to identify a schedule for retrieving the objects composing the presentation. A collaborating server can suggest modifications of the retrieval schedule depending on its load. these modifications can potentially affect the retrieval schedule for other collaborating applications. Hence, a sequence of negotiations has to be carried out with the collaborating servers in order to commit for a retrieval schedule of the objects composing the presentation. In this paper, we propose an application sub-layer protocol, RLCP(Resource Lock Commit Protocol), for handling the negotiation and commitment of the resources required for a collaborative multimedia presentation and apply it to distributed video presentation application.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.11
• /
• pp.2721-2731
• /
• 1997

Distributed programming can be greatly simplified by language support for distributed communication. Many web-browsers now offer some form of active objects and the number and types of them are growing daily in interesting and innovative ways. Java applets are well known as one kind of active object related to web-browser. This paper focuses in distributed active objects which is one kind of active objects that can communicate with other active objects located in different machines across the Internet. Java RMI and CORBA IDL are two major programming environments for distributed active objects which are non compatible with each other. To make discussion concrete, we introduce a single application as implemented on two environments : the HORM, adopting RMI mechanism, and the OrbixWeb2.0.1, adopting CORBA specification, respectively. Binding, inheritance, polymorphism, object passing and callbacks across the machine boundary in distributed programming environments are issued. The results show that some differences in the implementation of distributed active objects can have a significant impact on how distributed applications are structured. The comparison between two implementations on the programming environments will be the basis for building the translation system between HORB to OrbixWeb and vice versa.