• 한국지능시스템학회논문지
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• 제8권6호
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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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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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.

• 제어로봇시스템학회논문지
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• 제14권4호
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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.

• 한국정보통신학회논문지
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• 제9권1호
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• pp.210-216
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• 2005

대부분의 실시간 응용에서 보안은 또 하나의 중요한 요구 사항이 되고 있다. 따라서 보안 실시간 데이터베이스 시스템은 다양한 보안 등급을 갖는 여러 사용자가 공유하거나 악의를 갖은 해커에 의해 공격될 수 있는 민감한 정보를 관리해야 한다. 보안 실시간 데이터베이스 시스템이 보안을 위해서는 기존의 보안 방법뿐만 아니라 암호화 정책을 적용하는 것이 필요하다. 그렇지만 민감한 정보가 실시간 시스템에서도 보호되어야만 함에도 불구하고 보안 실시간 데이터베이스 시스템에서 암호화정책을 지원하기 위한 연구가 많지 않았다. 본 논문에서는 보안 실시간 데이터베이스 시스템의 이러한 암호화 정책 문제를 해결하기 위한 암호화 관리자를 제안한다. 보안 실시간 데이터베이스 시스템의 암호화 정책에서 중요한 것은 보안성과 시간성이다. 제안된 암호화 관리자의 중요한 특징은 트랜잭션 데드라인과 보안 수준을 고려하여 데이터를 동적으로 암호화하는 것이다.

• 로봇학회논문지
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• 제7권4호
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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.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 1997년도 추계학술대회 발표논문집:21세기를 향한 정보통신 기술의 전망
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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.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.3885-3892
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• 2010

원자력발전소의 발전소보호계통과 같은 안전필수 시스템은 예상 가능한 사고로부터 인간과 자연을 보호하기 위한 중요 기능을 수행하는 시스템으로써, 어떠한 조건 하에서도 고유의 안전기능을 안정적으로 수행할 수 있도록 설계되어야 한다. 원자력발전소의 안전필수 기능을 수행하는 계측제어시스템에 적용되는 최신의 컴퓨터에는 다양한 하부기기를 감시 및 제어하고, 응용 프로그램을 실행시키기 위한 실시간 운영체제가 탑재되어 있으며, 이러한 실시간 운영체제는 가장 엄격한 소프트웨어 품질이 요구된다. 또한, 예상 가능한 조건에서도 안전필수 시스템의 기능이 적절히 수행될 수 있도록 설계, 분석 및 평가되어야 한다. 그러나 지금까지 국내 원자력발전소 안전필수 시스템에는, 원자력 기준과 품질등급에 따라 개발된 제품이 아닌 상용제품의 실시간 운영체제를 정성적 측면에서 승인(Commercial Grade Item Dedication)하는 방식으로 적용되어 왔다. 이로 인해 실시간 운영체제가 안전필수 기능을 수행하는 데 적합한지를 평가하는 상세 방법론과 경험이 매우 부족한 것으로 파악되고 있다. 특히, 안전필수 시스템에 적용함을 목적으로 신규 개발되는 실시간 운영체제의 경우, 안전성을 평가하기 위한 적절한 방법을 도출하기에 어려움이 있는 것으로 파악되고 있다. 본 논문에서는 원전의 안전필수 기능을 수행하는 실시간 운영체제의 설계요구사항을 기반으로, 안전필수 실시간 운영체제에 대한 안전성 분석 및 평가 사례를 제시하고자 한다. 본 논문에서 제시한 상세 안전성 평가의 방법과 사례는 향후 타 산업분야에서의 안전필수 실시간 운영체제 개발 및 안전성 평가에 활용될 수 있을 것으로 기대된다.

• 제어로봇시스템학회논문지
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• 제5권1호
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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.

• 대한임베디드공학회논문지
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• 제8권6호
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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.