• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.68-70
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• 1998

본 논문에서는 클록들을 주기적으로 동기화하는 분산 실시간 시스템에서 주어진 태스크의 시간 제약(timing constraint)을 변환시는 구가지 기법을 제안한다. 전형적인 이산 클록 동기화(discrete clock synchronization)알고리즘은 클록의 값을 순간적으로 보정(correct)하여 클록의 시간이 불연속적으로 진행학 한다. 이러한 시간상의 불연속성은 태스크의 시작제한시간(release time)이나 종료시한(deadline)과 같은 이벤트를 잃어버리거나 다시 발생시키는 오류를 범하게 한다. 클록 시간의 불연속성을 피하기 위해 일반적으로 연속 클록 동기화(continuous clock synchronization) 기법이제안되었지만 소프트웨어적으로 구현되기에는 많은 오버헤드를 유발시키는 문제점이 있다. 이에 따라 연속 클록 동기화는 PLL (Phase-Locked Loop)을 이용한 별도의 하드웨어를 사용하는 것이 보통이다. 본 논문에서는 연속 클록 동기화 기법을 사용하는 대신, 태스크의 시간 제약을 동적으로 변환시키는 DCT (Dynamic Constraint Transformation) 기법을 제안하였다. DCT는 소프트웨어 으로 구현이 가능하여 새로운 하드웨어를 필요로 하지 않으며, 이를 통해 기존의 이산적으로 동기화된 시스템에서 클록 시간의 불연속성에 의한 문제점들을 해결할 수 있다. 또 다른 문제점으로서, 클록의 물리적인 특성으로 인해 동기화된 클록들이 상한된(bounded from the above)오차(skew)를 갖는다는 것이다. 이러한 오차는 지역 클록(local clock)에 대해 만족될 수 있는 임의의 실기간 제약 조건이 전역 클록(global clock)에 대해서는 만족되지 않을 수 있음을 의미한다. 본 논문에서는 이를 위해 먼저 두 가지의 스케줄링 가능성, 지역적 스케줄링 가능서(local schedulability)과 전역적 스케줄링 가능성(global schedulability)을 정의하고, 실시간 제약을 정적으로 변환시키는 SCT (Static Constraint Transformation)기법을 제안하였다. SCT를 통해 지역적으로 스케줄링 가능한 태스크는 전역적으로 스케줄링이 가능하므로, 단지 지역적 스케줄링 가능성만을 검사하면서 스케줄링 문제를 해결할 수 있도록 하였다.

• KIISE Transactions on Computing Practices
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• v.22 no.1
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• pp.32-37
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• 2016

In model-based testing using sequence diagrams, test cases are automatically derived from the sequence diagrams. For the generation of test cases, scenarios need to be found for representing as a sequence diagram, and to extract test paths satisfying the test coverage. However, it is hard to automatically extract test paths from the sequence diagram because a sequence diagram represents loop, opt, and alt information using CombinedFragments. To resolve this problem, we propose a transformation process that transforms a sequence diagram into an activity diagram which represents scenarios as a type of control flows. In addition, we generate test cases from the activity diagram by applying a test coverage concept. Finally, we present a case study for test cases generation from a sequence diagram.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.599-604
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• 2005

A functional suspension model is proposed as a kinematic describing function of the suspension, that represents the relative wheel displacement in polynomial form in terms of the vertical displacement of the wheel center and steering rack displacement. The relative velocity and acceleration of the wheel is represented in terms of first and second derivatives of the kinematic describing function. The system equations of motion for the full vehicle dynamic model are systematically derived by using velocity transformation method of multi-body dynamics. The comparison of test and simulation results demonstrates the validity of the proposed functional suspension modeling method. The model is computationally very efficient to achieve real-time simulation on TMS 320C6711 150 MHz DSP board of HILS (hardware-in-the-loop simulation) system for ECU (electronic control unit) evaluation of semi-active suspension.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.171-172
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• 2011

The paper proposes a close loop control algorithm for Z-source inverter. The algorithm is realized by PWM duty ratio control in order to improve the output voltage to it's desired level. The controller consist of the output voltage PID controller and DC input voltage P controller. Using the DQ coordinate transformation simplify the controller design. The PSIM simulation results verify the validity by means of comparing the system with or without compensation and estimating if the system has output consistency function when ZSI's load and input voltage value changing.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.194-195
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• 2011

본 논문은 Bi-directional Inverter(BDI)에 DQ 변환을 적용한 소신호 등가 모델과 이중 루프 제어기 설계에 대해 제안한다. 일반적으로 외부루프의 경우 동적 특성이 매우 느리기 때문에 외부루프 전달함수를 고려하지 않고 설계하는 경우가 많다. 결과적으로 시스템의 안정성이나 동적 특성이 설계한 것과 다르게 나타날 수 있다. 따라서 원하는 특성을 만족하기 위해 실험적 시행착오를 거쳐 설계를 하게 된다. 본 논문에서는 정확한 소신호 등가 모델을 제시하고 제어기를 설계한다. 제안된 방식은 PSIM 시뮬레이션 및 실험을 통해 회로해석과 소신호 등가모델의 타당성 및 제어기 설계의 타당성을 증명하였다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1849_1850
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• 2009

In this paper, we propose an adaptive observer for electrically driven mobile robots in the presence of parametric uncertainties. To estimate the unmeasured velocities of the mobile robot, we develop an adaptive observer using the transformation matrices which can solve the difficulty caused by the quadratic velocity terms depending on the uncertain parameters. Using the Lyapunov stability theory, we prove that all signals in a closed-loop system converge to zero. Finally, the simulation results demonstrate the effectiveness of the proposed observer system.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2480-2482
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• 2005

This paper presents a complete solution to intelligent digital redesign problem (IDR) for sampled-data fuzzy systems. The IDR problem is the problem of designing a sampled-data state feedback controller such that the sampled-data fuzzy system is equivalent to the continuous-time fuzzy system in the sense of the state matching. Its solution is simply obtained by linear transformation. Under the proposed sampled-data controller, the states of the discrete-time model of the sampled-data fuzzy system completely matches the state of the discrete-time model of the closed-loop continuous-time fuzzy systems are completely matched at every sampling points.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.560-564
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• 1996

A mixed H$^{2}$/$H^{\infty}$ controller design method for linear systems with time delay in all variables and parameter uncertainties in all system matrices is proposed. Robust $H^{\infty}$ performance and H$^{2}$ performance condition that accounts for model-matching of closed loop system and disturbance rejection is also derived. With expressing uncertain system with linear fractional transformation form, we transform the robust stability and performance problem to the H$^{2}$/$H^{\infty}$ optimization problem and design a mixed H$^{2}$/$H^{\infty}$ controller. Using the proposed method, mixed H$^{2}$/$H^{\infty}$ controller for underwater vehicle with time delay and parameter variations are designed. Simulations of a design example with hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.t performance.ance.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2688-2690
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• 1999

This paper presents the modeling method of $3{\Phi}$ phase-controlled rectifier considering the overlap interval for the drive of DC motor in the Matlab environment. The model is constructed by the module-based method and therefore it is appropriate in the research of the closed-loop controlled power electronic system in the Matlab/Simulink environment. The model of SCR is used as the element for the power transformation. The simulation results show that the overlap interval from the effect of the input inductance is accurate.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.2 no.1
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• pp.78-82
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• 2002

In this paper, we have studied a numerical stability analysis method for the robust fuzzy feedback linearization regulator using Takagi-Sugeno fuzzy model. To analyze the robust stability, we assume that uncertainty is included in the model structure with known bounds. For these structured uncertainty, the robust stability of the closed system is analyzed by applying Linear Matrix Inequalities theory following a transformation of the closed loop systems into Lur'e systems.