• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3361-3377
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• 2014

Synchronous computing models provided by real-time synchrony protocols, such as TTA [1] and PALS [2], greatly simplify the design, implementation, and verification of real-time distributed systems. However, their application to real systems has been limited since their assumptions on underlying systems are hard to satisfy. In particular, most previous real-time synchrony protocols hypothesize the existence of underlying fault tolerant real-time networks. This, however, might not be true in most soft real-time applications. In this paper, we propose a practical approach to a synchrony protocol, called Quality-Aware PALS (qPALS), which provides the benefits of a synchronous computing model in environments where no fault-tolerant real-time network is available. qPALS supports two flexible global synchronization protocols: one tailored for the performance and the other for the correctness of synchronization. Hence, applications can make a negotiation flexibly between performance and correctness. In qPALS, the Quality-of-Service (QoS) on synchronization and consistency is specified in a probabilistic manner, and the specified QoS is supported under dynamic and unpredictable network environments via a control-theoretic approach. Our simulation results show that qPALS supports highly reliable synchronization for critical events while still supporting the efficiency and performance even when the underlying network is not stable.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.2
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• pp.149-156
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• 2005

The HLA is the simulation architecture standard that the civilian and military simulation communities are deeply interested in. We can find various successful practices applying HLA to constructive simulations such as war games in domestics and overseas. However, any case of real-time distributed simulations has not been reported. The reason is that a message transmission period via RTI in a network layer varies according to computing power, simulation nodes, transmission types, and packet size; further a message processing time in an application layer depends on its processing methods, thus too difficult to set up real-time constraints for the enhancement of a real-time resolution. Hence, in this paper we have studied the real-time constraints of RTI for the development of the M-SAM simulator. Thus we have developed a HLA based pilot simulator using 6 PC's in LAN and then measured and analysed the performance of the RTI. As the results of our work, we could obtain the quantitative values for message delay, RTI overhead and RTI packet transmission ratio by a real operation scenario and loads, which are not shown in the previous works. We also expect that the results can be used as a guideline to set up the number of targets, transmission frequency and message processing method in the development of the M-SAM simulator and similar applications.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.5
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• pp.434-437
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• 2002

A small size and light-weight DSP board is newly designed for a real time multi-distributed control system that overcomes constraints on time and space. There are a variety of protocols for a real-time distributed control system. In this research, we selected CAN for the multi distributed control, which was developed by the BOSCH in the early 1980's. If CAN and Internet are connected together, the system attains the characteristics of a distributed control system and a remote control system simultaneously. To build such a system. The TCP/IP-CAN Gateway which converts a CAN protocol to TCP/IP protocol and vice verse, was designed. Moreover, the system is required to be small and light-weighted for the high mobility and cost effectiveness. The equipment in remote place has a TCP/IP-CAN Gateway on itself to be able to communicate with another systems. The received commands in the remote site are converted from TCP/IP protocol to CAN protocol by the TCP/IP-CAN Gateway in real time. A simulation system consists of a TCP/IP-CAN Gateway in remote place and a command PC to be connected to Ethernet.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.4
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• pp.603-610
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• 2004

Time delays are included in most of actual systems, and some of which are shown as time varying. To analyze the time varying time delay system in the time domain. a useful delay module to express the function as a tool is much helpful to get corresponding outputs under given conditions. A method is proposed here to design the algorithm of time delay module for simulation or control purposes, including the problems of initializing and reallocating data in buffer. After classifying the time varying time delay into the distributed mode and lumped mode, an object to describe delay module is configured and tested under the defined input signal and given time delay variation. The simulation results show that the output of module matches reasonably with the case of real system.

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

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.65-68
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• 1996

Robotic manipulators have become increasingly important in the field of flexible automation. High speed and high-precision trajectory tracking are indispensable capabilities for their versatile application. The need to meet demanding control requirement in increasingly complex dynamical control systems under significant uncertainties, leads toward design of intelligent manipulation robots. This paper presents a new approach to the design of neural control system using digital signal processors in order to improve the precision and robustness. The TMS32OC31 is used in implementing real time neural control to provide an enhanced motion control for robotic manipulators. In this control scheme, the networks introduced are neural nets with dynamic neurons, whose dynamics are distributed over all the, network nodes. The nets are trained by the distributed dynamic back propagation algorithm. The proposed neural network control scheme is simple in structure, fast in computation, and suitable for implementation of real-time, control. Performance of the neural controller is illustrated by simulation and experimental results for a SCARA robot.

• The Transactions of the Korea Information Processing Society
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• v.6 no.1
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• pp.57-65
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• 1999

The simulation which is larger scale, complex and interactive with clients treat a lot of messages. It can be thinking more efficient distributed simulation than sequential one. The training simulation with multi-users is geographically distributed, and required high cost to operate and maintain system as increasing user requirements. The adaptation of web technology to the simulation can be a way to solves it without cost added. But dynamic web environment can causes causality error of events. This paper is concerned with client-server model, which supports interaction between distributed simulation server and web browser, and it is implemented by Java distributed object model. the result have shown that the distributed simulation is performed correctly on dynamic environment.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.9
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• pp.9-17
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• 1993

There are multiple controllers (PLC. LOOP Controller ) which are operating in product line and fabrication line. In those lines, it is necessary to connect various multilple controllers with integrity and coordination. The ways to connect those devices are specified by ISO network standard. In this paper, real time network is designed and implemented for factory automation at lowest possible cost that meets the small and middle size MINI-MAP specifications. Network performance is evaluated by simulation method on data link layer implemented interfacing modules has efficiency in throughput by reducing processing time. The system designed in this paper can be also applied to the field of distributed systems for real time processing.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.799-803
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• 1991

This study proposes a CIM shell that is consisted with computers connected by a LAN. Since this system excludes production hardwares, physical movements of devices are represented by computer simulation. On the other hand, softwares that dictate system operation are real, and consu- me physical time. Thus the shell becomes half-real-half-simulation that requires events synchronization mechanism. This study shows the building procedure of such shell as well as an example of application of the shell.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1131-1135
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• 2014

This paper proposes the enhanced faulty node detection scheme with hybrid algorithm using Markov-chain model on BCH (Bose-Chaudhuri-Hocquenghem) code in naval distributed control networked systems. The probabilistic model-driven approach, on Markov-chain model, in this paper uses the faulty weighting interval factors, which are based on the BCH code. In this scheme, the master node examines each slave-nodes continuously using three defined states : Good, Warning, Bad-state. These states change using the probabilistic calculation method. This method can improve the performance of detecting the faulty state node more efficiently. Simulation results show that the proposed method can improve the accuracy in faulty node detection scheme for real-time naval distributed control networked systems.