• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1564-1572
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• 2006

This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix of each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. .Finally, the kinematic optimization of the mechanisms is performed with regards to their dexterity, stiffness and space utilization. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.2
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• pp.107-113
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• 2004

This paper develops a adaptive fuzzy controller based fuzzy logic control for high performance of permanent magnet synchronous motor(PMSM) drives. In the proposed system, fuzzy control is used to implement the direct controller as well as the adaptation mechanism. The operation of the direct fuzzy controller and the fuzzy logic based adaptation mechanism is studied. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the adaptive fuzzy controller is evaluated by simulation for various operating conditions. The validity of the proposed adaptive fuzzy controller is confirmed by performance results for PMSM drive system.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.132-138
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• 2004

In a vacuum circuit breaker mechanism, a spring-actuated linkage system is used to satisfy the desired opening and closing characteristics of electric contacts. If the type and structure of the linkage system required to the circuit breaker is predetermined, the stiffness, free length and attachment points of a spring become the important design parameters. In this paper, based on the energy conservation that the total system energy is constant throughout the operating range of the mechanism, a systematic procedure for optimizing the spring design parameters is developed and applied to the simplified mechanism of a circuit breaker. Then, in order to consider the complex dynamics of the circuit breaker mechanism rather well, the developed procedure is converted to the environment of a multi-body dynamics program ADAMS.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.35-41
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• 2011

This work investigates the potential of in-cylinder thermal stratification and fuel stratification for extending the operating ranges in HCCI engines, and the coupling between thermal stratification and fuel stratification. Computational results areemployed. The computations were conducted using both a custom multi-zone version and the standard single-zone version of the Senkin application of the CHEMKINII kinetics rate code, and kinetic mechanism for di-methyl ether (DME). This study shows that the potential of thermal stratification and fuels stratification for extending the high-load operating limit by a staged combustion event with reduced pressure-rise rates is very large. It was also found that those stratification offers good potential to extend low-load limit by a same mechanism in high-load. However, a combination of thermal stratification and fuel stratification is not more effective than above stratification techniques for extending the operating ranges showing similar results of fuel stratification. Sufficient condition for combustion (enough temperature for) turns misfire in low-load limit to operate engines, which also leads to knock in high-load limit abruptly due to the too high temperature with high. DME shows a potential for maximizing effect of stratification to lower pressure-rise rate due to the characteristics of low-temperature heat release.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.330-335
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• 2012

Brushless doubly-fed machine (BDFM) doesn't use brush and slip ring, and has advantages such as high system reliability, small capacity of its frequency converter, low system cost, adjustable power factor and speed, etc. At the same time, it has good applicable potentials on the variable frequency motors and the variable speed constant frequency generators. However, due to the complicacy and particularity of BDFM in the structure and operating mechanism, the effect of magnetic field modulation directly influences the operating efficiency of BDFM. To study the effect of different cage rotor structures on the magnetic field modulation of BDFM, the rotor magnetomotive force (MMF) of BDFM with cage rotor is studied by the analytical method. The components and features of rotor harmonic MMFs are discussed. At the same time, the method to weaken the higher harmonics is analyzed by the theoretic formulae. Furthermore, the magnetic field modulation mechanism is expounded on in detail and the relationship between the magnetic field modulation effect and the operating efficiency of BDFM is established. And then, a new method for estimating the magnetic field modulation effect is proposed. At last, the magnetic field modulation effects of four BDFM prototypes with different cage rotor structures are compared by the MMF analysis and the efficiency data of electromagnetic design. The results verify the effectiveness of the new method for estimating the magnetic field modulation effect of BDFM with cage rotor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1002-1005
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• 2015

Mobile operating systems have been typically classified into Apple and Android. Samsung showed its own new mobile OS developing Tizen based on Linux kernel. Mobile operating system has developed a technology using low-power by itself because of the limitation of capacity of battery, a feature of mobile. Samsung Tizen OS has a low-power technology called Power Manager controling LCD states as users'inputs or time-out events occur. However, if users'input occurs frequently, energy consumption jumped before-and-after users'input because CPU clock is increased rapidly due to overhead increase for frequent LCD state changes. This paper proposes a mechanism to reduce the overhead for LCD state changes, when user's input is frequent, by adding a new state to the Power Manager the current Tizen OS is using. We have implemented the proposed mechanism at Tizen phone kernel layer in this paper and experimented the mechanism according to users' LCD touch inputs. The experiment shows that it is possible to decrease energy by reducing the CPU clock increase according to the frequent user's inputs.

• Journal of the Korea Society of Computer and Information
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• v.3 no.4
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• pp.110-119
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• 1998

This paper describes a C-API (Cryptographic-Application program Interface) mechanism that can serve cryptographic service to one or more application programmers in an open distributed computing system. Generic cryptographic service, provides application Programmers with cryptographic algorithms and interfaces which can be shared so that the programmers can program distributed applications containing security services even though they have no detailed knowledge of cryptographic algorithms. Therefore, in this paper, a generic C-API mechanism is designed that can be used independently from various application environments and basic system structures so that programmers can use it commonly. This mechanism has the advantage that allows application programmers be able to use some cryptographic services and key management services not considering of the application program and operating system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1181-1184
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• 2005

In this paper, we proposed small scale real-time operating system for embedded system. Real-time system is characterized by the severe consequences that result if logical as well as timing correctness properties of system are not met. On real-time system, real-time operating system allows real-time applications to be designed and expanded easily. Functions can be added without requiring major changes to the software. We design small scale real-time operating system for preemptive kernel, and design kernel component such as multitasking, scheduler, task priority, semaphore, inter-task communication, clock tick timer, ISR(Interrupt Service Routine) mechanism has low interrupt latency.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.173-182
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• 2002

We investigated the effects of operating variables, such as electrical. reactor and gas parameters on toluene removal and discharge property in the dielectric barrier discharge (DBD) process. The toluene removal was initiated with the energy transfer to the reactor by loading of voltages higher than the discharge onset value. The energy transfer and toluene removal increased with the applied voltage. Higher removal rate was observed with smooth surface electrode despite of lower energy transfer compared with the coarse electrode, because more uniform discharge can be obtained on smooth surface state. The decrease of dielectric material thickness enhanced the removal efficiency by increasing the discharge potential. The toluene removal efficiency decreased with the increase of the inlet concentration. The increase of gas retention time enhanced the removal efficiency by the increase of energy density. The oxygen and humidity contents seem to exert significant influences on the toluene removal by dominating the generation of electrons, ions, and radicals which are key factors in the removal mechanism.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.375-378
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• 1996

Robot control software is a hard real-time system that must output the planned trajectory points within an explicit short time period. In this paper, we present a design and implementation method for robot control software using commercial real-time operating systems, RTKemel 4.5. Therefore, various robot motions, efficient user interface, and system failure check are easily implemented by using multitasking function, intertask communication mechanism, and real-time runtime libraries of RTKernel. The performance analysis of commercial real-time operating system for robot control is presented based on Timed Petri net(TPN) and we can use these results to design an optimal system.