• Title/Summary/Keyword: real-time systems

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Real Time Modeling of Discrete Event Systems and Its Application (이산사건 시스템의 실시간 모델링 및 응용)

  • Jeong, Yong-Man;Hwang, Hyung-Soo
    • Journal of the Korean Institute of Intelligent Systems
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    • v.8 no.6
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    • pp.91-98
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    • 1998
  • A DEDS is a system whose stated change in response to the occurrence of events from a predefined event set. A major difficulty in developing analytical results for the system is the lack of appropriate modeling techniques. In this paper, we consider the modeling and control problem for Discrete Event Dynamic Systems(DEDS) in the Temporal Logic framework(TLF) which have been recently defined. The traditional TLF is enhanced with time functions for real time control of Discrete Event Dynamic Systems. A sequence of event which drive the system from a given initial state to a given final state is generated by pertinently operating the given plants. This paper proposes the use of Real-time Temporal Logic as a modeling tool for the analysis and control of DEDS. An given example of fixed-time traffic control problem is shown to illustrate our results with Real-time Temporal Logic Framework.

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Development of Embedded Web Server System Using a Real-Time OS (실시간 운영체제를 이용한 내장형 웹서버 시스템 개발)

  • 정명용;문승빈;송상훈
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.223-223
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    • 2000
  • Embedded system area has brought an innovation and has been spread rapidly by the growth of the Internet, wireless telephony and multimedia recently. Many embedded systems are required to be real-time systems in that it needs multi-tasking and priority based scheduling. This paper introduces a real-time system that was developed with web server ability for control and monitoring system employing a real-time operating system. It discusses the design model, structure, and applications of web server system. We used SNDS100 board which has a 32-bit RISC microcontroller of ARM7TDMI core as a hardware platform. MicroC/OS kernel was used as Real-time operating system that supports a preemptive and multitasking functions. We developed a hierarhchical control and monitoring system that not only reduced system and management costs, but also enhanced reusability and portability.

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Stability and a scheduling method for network-based control systems (네트워크를 이용한 제어 시스템의 안정도 및 스케줄링에 관한 연구)

  • 김용호;권욱현;박홍성
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10b
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    • pp.1432-1435
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    • 1996
  • This paper obtains maximum allowable delay bounds for stability of network-based control systems and presents a network scheduling method which makes the network-induced delay be less than the maximum allowable delay bound. The maximum allowable delay bounds are obtained using the Lyapunov theorem. Using the network scheduling method, the bandwidth of a network can be allocated to each node and the sampling period of each sensor and controller can be determined. The presented method can handle three kinds of data (periodic, real-time asynchronous, and non real-time asynchronous data) and guarantee real-time transmissions of real-time synchronous data and periodic data, and possible transmissions of non real-time asynchronous data. The proposed method is shown to be useful by examples in two types of network protocols such as the token control and the central control.

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Performance Analysis of Checkpointing and Dual Modular Redundancy for Fault Tolerance of Real-Time Control System (실시간 제어 시스템의 결함 극복을 위한 이중화 구조와 체크포인팅 기법의 성능 분석)

  • Ryu, Sang-Moon
    • Journal of Institute of Control, Robotics and Systems
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    • v.14 no.4
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    • pp.376-380
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    • 2008
  • This paper deals with a performance analysis of real-time control systems, which engages DMR(dual modular redundancy) to detect transient errors and checkpointing technique to tolerate transient errors. Transient errors are caused by transient faults and the most significant type of errors in reliable computer systems. Transient faults are assumed to occur according to a Poisson process and to be detected by a dual modular redundant structure. In addition, an equidistant checkpointing strategy is considered. The probability of the successful task completion in a real-time control system where periodic checkpointing operations are performed during the execution of a real-time control task is derived. Numerical examples show how checkpoiniting scheme influences the probability of task completion. In addition, the result of the analysis is compared with the simulation result.

A Study on the Dynamic Encryption Manager for Improved Timeliness in Secure Real-Time Database Systems (보안 실시간 데이터베이스 시스템에서 시간성 향상을 위한 동적 암호화 관리자에 관한 연구)

  • Lee, Soon-Jo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.9 no.1
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    • pp.210-216
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    • 2005
  • In many real-time applications, security is another important requirement, since the secure real time database system maintains sensitive information to be shared by multiple users with different levels of security clearance or to be attacked by hackers with ill will. Encryption policies are necessary for the security of secure real-time database systems in addition to the existing security methods, too. However, there has not been much work for the encryption policies in secure real-time database systems, although sensitive information must be safeguarded in real-time systems as well. In this paper, we propose a encryption manager for the purpose of solving the encryption policies of the secure real-time database systems. What is important in the encryption policies of secure real-time database systems is security and timeliness. A significant feature of the proposed encryption manager is the ability to dynamically adapt a encryption algorithm that consider transaction deadline and security level.

On Benchmarking of Real-time Mechanisms in Various Periodic Tasks for Real-time Embedded Linux (실시간 임베디드 리눅스에서 다양한 주기적 타스크의 실시간 메커니즘 성능 분석)

  • Koh, Jae-Hwan;Choi, Byoung-Wook
    • The Journal of Korea Robotics Society
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    • v.7 no.4
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    • pp.292-298
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    • 2012
  • It is a real-time system that the system correctness depends not only on the correctness of the logical result of the computation but also on the result delivery time. Real-time Operating System (RTOS) is a software that manages the time of a microprocessor to ensure that the most important code runs first so that it is a good building block to design the real-time system. The real-time performance is achieved by using real-time mechanisms through data communication and synchronization of inter-task communication (ITC) between tasks. Therefore, test on the response time of real-time mechanisms is a good measure to predict the performance of real-time systems. This paper aims to analysis the response characteristics of real-time mechanisms in kernel space for real-time embedded Linux: RTAI and Xenomai. The performance evaluations of real-time mechanism depending on the changes of task periods are conducted. Test metrics are jitter of periodic tasks and response time of real-time mechanisms including semaphore, real-time FIFO, Mailbox and Message queue. The periodicity of tasks is relatively consistent for Xenomai but RTAI reveals smaller jitter as an average result. As for real-time mechanisms, semaphore and message transfer mechanism of Xenomai has a superior response to estimate deterministic real-time task execution. But real-time FIFO in RTAI shows faster response. The results are promising to estimate deterministic real-time task execution in implementing real-time systems using real-time embedded Linux.

Design and Implementation of a Architecture For Fault-Tolerant and Real-Time System (결함허용 실시간 시스템 구조에 대한 설계 및 구현)

  • 유종상;김범식;신인철
    • Proceedings of the Korea Society for Industrial Systems Conference
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    • 1997.11a
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    • pp.417-433
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    • 1997
  • A real-time operating system has focused primary on techniques to minimize processing time, with a secondary emphasis on system reliability issues. Conversely, fault-tolerant system has concentrated on using recourse and information redundancy to maximize the availability and reliability of the system, with a lesser emphasis on performance. We have developed a fault-tolerant and real-time operations system which support a powerful concurrent runtime environment under the above requirements. In this paper, we present an overview of real-time systems, design and implementation of a duplex architecture using advanced concepts and technologies such as fast " fault detection", "fault isolation" and "fault recovery" Because the duplex architecture has two dentical hardware elements and has several recovery steps and hierarchy to facilitate a fast recovery which must be proceeded by a prompt fault detection and isolation. Thus it makes possible to minimize the overhead of the systems including hardware and software and guarantee the service continuity of he systems.

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Safety Evaluation on Real Time Operating Systems for Safety-Critical Systems (안전필수(Safety-Critical) 시스템의 실시간 운영체제에 대한 안전성 평가)

  • Kang, Young-Doo;Chong, Kil-To
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.10
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    • pp.3885-3892
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    • 2010
  • Safety-Critical systems, such as Plant Protection Systems in nuclear power plant, plays a key role that the facilities can be operated without undue risk to the health and safety of public and environment, and those systems shall be designed, fabricated, installed, and tested to quality standards commensurate with the importance of the functions to be performed. Computer-based Instrumentation and Control Systems to perform the safety-critical function have Real Time Operating Systems to control and monitoring the sub-system and executing the application software. The safety-critical Real Time Operating Systems shall be designed, analyzed, tested and evaluated to have capability to maintain a high integrity and quality. However, local nuclear power plants have applied the real time operating systems on safety critical systems through Commercial Grade Item Dedication method, and this is the reason of lack of detailed methodology on assessing the safety of real time operating systems, expecially to the new developed one. This paper presents the methodology and experiences of safety evaluation on safety-critical Real Time Operating Systems based upon design requirements. This paper may useful to develop and evaluate the safety-critical Real Time Operating Systems in other industry to ensure the safety of public and environment.

Development of Real-Time Distributed Simulator and Controller Based on Virtual Machine (가상머신을 이용한 실시간 분산처리 시뮬레이터 및 제어기)

  • 양광웅;박재현
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.1
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    • pp.115-121
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    • 1999
  • Advanced digital computer technology enables the computer-based controllers to replace the traditional analog controllers used in factory automations. This replacement, however, brings up the side effects caused by the quantization error and non-real-time execution of control software. This paper describes the structure of real-time simulator and controller that can be used for design and verification of real-time digital controllers. The virtual machine concept adopted by the proposed real-time simulator makes the proposed simulator be independent from the specific hardware platforms. The proposed system can also be used in the loosely coupled distributed environments connected through local area network using real-time message passing algorithm and virtual data table based on the shared memory mechanism.

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Real-Time Centralized Soft Motion Control System for High Speed and Precision Robot Control (고속 정밀 로봇 제어를 위한 실시간 중앙 집중식 소프트 모션 제어 시스템)

  • Jung, Il-Kyun;Kim, Jung-Hoon
    • IEMEK Journal of Embedded Systems and Applications
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    • v.8 no.6
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    • pp.295-301
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    • 2013
  • In this paper, we propose a real-time centralized soft motion control system for high speed and precision robot control. The system engages EtherCAT as high speed industrial motion network to enable force based motion control in real-time and is composed of software-based master controller with PC and slave interface modules. Hard real-time control capacity is essential for high speed and precision robot control. To implement soft based real time control, The soft based master controller is designed using a real time kernel (RTX) and EtherCAT network, and servo processes are located in the master controller for centralized motion control. In the proposed system, slave interface modules just collect and transfer all sensor information of robot to the master controller via the EtherCAT network. It is proven by experimental results that the proposed soft motion control system has real time controllability enough to apply for various robot control systems.