• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.79-86
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• 2007

In this paper, an adaptive control algorithm using system identification is proposed for an aircraft fault tolerant control system. A discrete state-space system is reformulated to be the ARX model which has the advantage in handing variable structure systems. Discrete model reference adaptive control is used to make the output of fault system follow the output of reference model. To validate the performance of the proposed control scheme, numerical simulations are performed for the high performance aircraft with control surface damage.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.430-449
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• 2004

A quantitative model for a control system that integrates human operators, systems, and their interactions is developed based on discrete functions. After identifying the major entities and the key factors that are important to each entity in the control system, a quantitative analysis to estimate the recovery failure probability from an abnormal state is performed. A numerical analysis based on assumed values of related variables shows that this model produces reasonable results. The concept of 'relative sensitivity' is introduced to identify the major factors affecting the reliability of the control system. The analysis shows that the hardware factor and the design factor of the instrumentation system have the highest relative sensitivities in this model. T도 probability of human operators performing incorrect actions, along with factors related to human operators, are also found to have high relative sensitivities. This model is applied to an analysis of the TMI-2 nuclear power plant accident and systematically explains how the accident took place.

• 대한전자공학회논문지
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• 제25권5호
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• pp.482-489
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• 1988

In this paper, we proposed a generalized model reference adaptive control theory which can be applied to single-input single-output discrete system by using V.M.Popov's hyperstability theory. As the result of theoretical analysis, it is proved that the discrete adaptive control scheme proposed by Narendra is a special case of the adaptive control schemes proposed in this paper. Also we suggest a variety of parameter adaptiations methods of controller through hyperstability theory.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.411-413
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• 1997

This paper presents the problem of fault-tolerant robust supervisory control of timed discrete event systems (DESs). First the concept of faults is quantitatively defined in timed DESs and fault tolerable event sequences are presented as a desired legal language. Given a timed DES with model uncertainty, the conditions for the existence of a supervisor which always guarantees fault tolerable event sequences embedded in the system are derived.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1362-1366
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• 2003

Workload programming is allocating suitable workloads of production process according to the needs of products, which would minimize the total cost of both work and stock under some constraint conditions. In this paper, a production process flow chart of discrete manufacturing is presented by a Petri net, and the optimization model of workload-stock is established. An approach of the optimal workloads is provided by means of the integer matrix theory. An example is given to verify this method.

• 한국수학교육학회지시리즈A:수학교육
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• 제38권2호
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• pp.189-197
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• 1999

Discrete mathematics allows students to examine and explore unique, special problem situations which were not used to solve problems by paper-and-pencil procedures or applying common formulas. The use and integration of accessible computer-related technologies such as 'Mathematics' or 'Maple' software programs enables students to explore problem situation dramatically. This study shows that it is possible to introduce computer-based discrete mathematics focused on the Leslie matrix model as modeling age-specific population growth to high school students.

• 대한전기학회논문지:전력기술부문A
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• 제48권11호
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• pp.1441-1447
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• 1999

A discrete time domain modeling is presented for the pulse-width modulated series resonant converter (PWM-SRC) with a discontinuous current mode. This nonlinear system is linearized about its equilibrium state to obtain a linear discrete time model for the investigation of small signal performances such as the stability and transient response. The usefulness of this small signal model is verified through the dynamic simulation.

• Structural Engineering and Mechanics
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• 제16권6호
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• pp.713-730
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• 2003

This paper contains the results of the study on the development of fracture and crack propagation in quasi-brittle materials, such as concrete or rocks, using the Discrete Element Method (DEM). A new discrete element numerical model is proposed as the basis for analyzing the inelastic evolution and growth of cracks up to the point of gross material failure. The model is expected to predict the fracture behavior for the quasi-brittle material structure using the elementary aggregate level, the interaction between aggregate materials, and bond cementation. The algorithms generate normal and shear forces between two interfacing blocks and contains two kinds of contact logic, one for connected blocks and the other one for blocks that are not directly connected. The Mohr-Coulomb theory has been used for the fracture limit. In this algorithm the particles are moving based on the connected block logic until the forces increase up to the fracture limit. After passing the limit, the particles are governed by the discrete block logic. In setting up a discrete polygon element model, two dimensional polygons are used to investigate the response of an assembly of different shapes, sizes, and orientations with blocks subjected to simple applied loads. Several examples involving assemblies of particles are presented to show the behavior of the fracture and the failure process.

• 지질공학
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• 제5권2호
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• pp.155-165
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• 1995

열극암반내의 지하수유동 및 용질이동 해석을 위해서는 추계론적인(Simulation Techique) 3차원 불연속체 모형(Discrete Fracture Model)이 요구된다. Monte Carlo 모의기법(Simulation Techique)에 의해 구성된 추계론적 불연속체모형을 지하 유류저장공동의 기밀성평가를 위한 지하수유동 및 용질이동 모의에 적용하였다. 불연속체모형구성에 영향을 미치는 열극 특성요소는 방향서 및 크기로 분석되었으며, 구성도니 모형(Model)에서의 지하수유동에 영향을 미치는 요소는 투수성 열극밀도로 분석되었다. Particle Tracking 기법을 사용한 불연속체모형의 용질이동 모의에서는 열극의 투수성에 의해 이동경로 및 이동속도에 많은 차이가 관찰되었다. 검증된 추계론적 불연속체모형은 지하 유류저장공동 기밀성평가에 적용이 가능함이 부분적으로 인정되었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권1호
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• pp.33-40
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• 2000

In this paper, an integrated method for the path planning and motion control of wheeled mobile robots using a hybrid system model and control is presented. The hybrid model including the continuous dynamics and discrete dynamics with the continuous and discrete state vector is derived for a two wheel driven mobile robot. The architecture of the hybrid control system for real time path planning and following is designed which has the 3-layered hierarchical structure : the discrete event system using the digital automata as the higher process, the continuous state system for the wheel velocity controls as the lower process, and the interface system as the interaction process between the continuous system as the low level and the discrete event system as the high level. The reference motion commands for autonomous navigation are generated by the abstracted motion in the discrete event system. The motion control tasks including the feasible path planning and autonomous motion control with various initial conditions are investigated as the applications by the simulation studies.