• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.82.1-82
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• 2001

It is known that existence of irregular transmission time delay is a major bottleneck for application of advanced robot control schemes to internet telerobotic systems. In the internet teleoperation system, the irregular transmission time delay causes a critical problem, which is unstable and inaccurate. This paper suggests a practical internet teleoperation system with streaming buffer system, which consists of a buffer, a buffer manager, and a control timer. The proposed system converts the irregular transmission time delay to constant. So, the system effectively transmits the control input to a remote site to operate a robot stably and accurately. This feature enables short control input interval. That means the entire system has ...

• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.115-130
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• 2012

These days, most of safety-critical systems, which are systems those failures or malfunction may result in death or serious injury to people, or loss or severe damage to social systems, or environmental harm, are being built of embedded software or loaded controlling software systems on computers, electrical and electronic components or devices. There are a lot kind of fault analysis methods to evaluate safety of the safety-critical systems equipped computers, electrical and electronic components or devices with software. However, the only assessment method to evaluate software safety of a safety-critical system is not enough to analysis properly on account of the various types and characteristic of software systems by progress of information technology. Therefore, this paper proposes the integrated evaluation method and carries out a case study for the software safety of safety-critical system which embedded or loaded software sizes are small and control response times are not sensitive by use of two security analysis methods which are Fault Tree Analysis (FTA) and Fault Modes and Effect Analysis (FMEA) for ubiquitous healthcare system.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.606-621
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• 2004

A dynamic analysis using a hybrid finite element method was performed to characterize the effects of a number of manufacturing errors on bearing forces and critical tooth stress in the elements of a planetary gear system. Some tolerance control guidelines for managing bearing forces and critical stress are deduced from the results. The carrier indexing error for the planet assembly and planet runout error are the most critical factors in reducing the planet bearing force and maximizing load sharing, as well as in reducing the critical stress.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.87.3-87
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• 2001

The principle of matching is a new framework for control systems design that requires the matching between the control system and the environment (the source of exogenous inputs). The principle is especially useful for the design of the critical control systems where the responses of the control systems should be kept below the prescribed values. The design problem is reduced to find controller satisfying inequality constraints. However, conventional optimization techniques do not possess structural model selection ability and designers are required to select appropriate controller model. We propose to use a genetic algorithm to find an appropriate controller satisfying the matching conditions. The proposed genetic algorithm ...

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.100-105
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• 1990

Associated with the protection and control functions in the substations, a new network scheme based on the IEEE 802.4 is proposed in this paper. This network is designed for supporting 3 data classes: 1st, it includes the highly time-critical data for the fault detection function. 2nd, routine data with a period is to served for monitoring the power status. Finally, it contains the control data which is used for reporting an event about protection or tuning some values related with power status. The way to allocate target_token_rotation timer is provided to guarantee the protection and control activities in the suggested network for the substation.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1178-1183
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• 1990

A digital signal processor(DSP) is applied to realizing a compensator of control system of active magnetic bearings, to restrict a resonance caused by the first-order bending vibration of a flexible rotor, and to run the rotor beyond the critical speed. A full-order observer is applied to the translatory rotor-motion with the first-order vibration mode. A PID control is used for the conical motion. The rotor used in the experiments is symmetric, and an electromagnet and a displacement sensor are set in collocation.

• International Journal of Control, Automation, and Systems
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• v.3 no.spc2
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• pp.376-385
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• 2005

The proliferation of technology has made global conduction of business increasingly dependent upon the availability of reliable power. As a result, alternate power systems are being installed and expanded to protect the broadening scope of critical electrical loads. Bus transfer restores designated critical loads to an alternate source when utility derived service becomes inadequate or goes out of service due to any contingency. This paper describes the practices, requirements and implementation of bus transfer of motor loads to an alternate source of power. A new high-speed automatic bus transfer scheme is proposed which includes the development of a new algorithm for determining the type of bus transfer required and the realization of the scheme by using modem protection devices and intra-substation communication facilities.

• Journal of the Korea Safety Management & Science
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• v.17 no.1
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• pp.93-101
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• 2015

The demand from customers on better products and systems seems to be ever increasing. To meet the demand, the systems are becoming more and more complicated in terms of both scale and functionality, thereby requiring enormous effort in the development. One bright spot of this trend is that such effort has been the driving forces of the remarkable advancement in modern systems development. On the other hand, safety issues appear to be critical in many large-scale systems such as transportation and weapon systems including high-speed trains, airplanes, ships, missiles/rockets launchers, and so on. Such systems turn out to be prone to a variety of faults and thus the resultant failure can cause disastrous accidents. For the reason, they can be referred to as safety-critical systems. The systems failure can be attributed to either random or systemic factors (or sometimes both). The objective of this paper is on how to reduce potential systemic failure in safety critical systems. To do so, a proper system design is pursued to minimize the risk of systemic failure. A focus is placed on the fact that complex systems have a lot of complicated interfaces among the system elements. To effectively handle the sources of hazards at the complicated interfaces and resultant failure, a method is developed by utilizing a design structure matrix. As a case study, the developed method is applied in the design of train control systems.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.87-92
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• 2009

Many critical control systems are developed using formal methods. When software applied to such systems is developed, the employment of formal methods in the software requirements specification and verification will provide increased assurance for such applications. Earlier errors of overlooked requirement specification can be detected using the formal specification method. Also, the testing and full verification to examine all reachable states using model checking to undertake formal verification are able to be completed. In this paper, we proposed an eclectic approach to incorporate Z(Zed) formal language and 'Statemate MAGNUM', formal method tools using Statechart. Also we applied the proposed method to train control systems for the formal requirement specification and analyzed the specification results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.3888-3910
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• 2018

As an increasing number of defense methods against control-data attacks are deployed in practice, control-data attacks have become challenging, and non-control-data attacks are on the rise. However, defense methods against non-control-data attacks are still deficient even though these attacks can produce damage as significant as that of control-data attacks. We present a method to defend against non-control-data attacks using influence domain monitoring (IDM). A definition of the data influence domain is first proposed to describe the characteristics of a variable during its life cycle. IDM extracts security-critical non-control data from the target program and then instruments the target for monitoring these variables' influence domains to ensure that corrupted variables will not be used as the attackers intend. Therefore, attackers may be able to modify the value of one security-critical variable by exploiting certain memory corruption vulnerabilities, but they will be prevented from using the variable for nefarious purposes. We evaluate a prototype implementation of IDM and use the experimental results to show that this method can defend against most known non-control-data attacks while imposing a moderate amount of performance overhead.