• 한국정보처리학회논문지
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• 제3권6호
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• pp.1397-1406
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• 1996

본 논문에서는 자동화된 생산 시스템과 조립 시스템에서 반제품을 생산기기들 사 이로 운반하기 위해 가장 많이 이용되고 있는 컨베이어 (conveyor) 시스템의 이산구 조 모델을 제안한다. 조립라인과 같이 조립 기기들 사이에 반제품을 운반하는 데 걸 리는 시간이 단위공정을 수행하는 데 걸리는 시간보다 클 경우, 조립기기들의 배치와 컨베이어로 연결되는 조립기기들 사이의 거리는 전체 조립시스템의 성능에 중요한 영 향을 미치게 되므로 컨베이어 시스템의 특성을 정량적으로 분석하기 위한 모델이 필 요하다. 본 논문에서 제안하는 모델은 팔레트(pallet)를 이용하는 컨베이어 시스템에 서 각각의 컨베이어의 길이가 팔레트 길이의 정수 배이며 컨베이어의 속도가 일정하 다는 가정을 전제로 한다. 이런 가정 하에서 컨베이어 운동의 관측 시간과 컨베이어 의 길이는 양자화 될 수 있으므로 각 샘플링 시각에서의 컨베이어 시스템의 상태는 양자화된 컨베이어상의 팔레트 유무와 이 팔레트의 이동도(mobility)를 나타내는 두 가지의 Boolean 변수로 간단히 표시될 수 있다. 이 두 변수를 바탕으로 전체 컨베이 어 시스템은 생산기기들 사이의 통로인 branch와 branch의 끝점인 knot의 조합으로 구성된 network으로 모델링된다. 이 모델링 방법으로 여러 가지 모양의 컨베이어 시 스템을 모델링해 본 결과 복잡한 토폴로지의 컨베이어 시스템도 간단히 모델링 및 시 뮬레이션될 수 있었으며 공장설계, 공정제어 등의 시뮬레이션에 유용하게 이용될 수 있음을 보여 주었다.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.345-351
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• 2024

The unitized regenerative fuel cell (URFC) is a method that can reduce costs and increase system simplification by unitizing a fuel cell system and a water electrolysis system. The spray method is suitable as the membrane electrode assembly (MEA) manufacturing method for URFC because it is easy to control the amount of catalyst, the size of the system is small, and economical manufacturing is possible. In this study, a numerical analysis of the effect of solution concentration on the spray method was performed to use it as basic data for the spray method to be used in MEA manufacturing. As result, as the Nafion solution concentration decreases it was found that the spray speed and the mass flow rate and the discrete phase model concentration increases and the spray range widens.

• 경영과학
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• 제9권1호
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• pp.3-15
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• 1992

In this paper, we study a manufacturing system of serial stages with general service times, in which the production of each stage and the coordination of stages are controlled by Kanban discipline. This Kanban discipline is modeled as a Discrete Event Dynamic System and a system of recursive equations is applied to study the dynamics of the system. The recursive relationship enables us to compare this Kanban discipline with the other blocking disciplines such as transfer blocking, service blocking, block-and-hold b, and block-and-hold K, and the Kanban is shown to be superior to the other disciplines in terms of makespan and throughput. As a special case, two stages Kanban system is modeled as $C_2/C_2/1/N$ queueing system, and a recursive algorithm is developed to calculate the system performance. In optimizing the system performance, the stochastic optimization approach of Robbins-Monro is employed via perturbation analysis, the way to estimate the stochastic partial derivative based on only one sample trajectory of the system, and the required commuting condition is verified. Then the stochastic convexity result is established to provide second-order optimality condition for this parametric optimization problem.

• 품질경영학회지
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• 제18권2호
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• pp.54-68
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• 1990

Contingency response in a FMS system requires that the system be able to identify and evaluate a number of alternatives. This paper is outlined that DSS completes with a problem processor in corporating Timed Petri Nets model, and a data base system. DSS enables the FMS user to get the maximum benefit from a FMS. The structure of this DSS parallels the organizational activities involved in running the FMS. In designing a shop floor controller for FMS, interactions between the different real time, discrete event functions must be established. The specification of the machine tool and material handling system functions working as a concurrent and cooperative system is given in terms of Timed Petri Nets. In addition, the basic concepts and uses of Petri Nets are surveyed. The system to be studied is first modelled by a Timed Petri Nets and then procedure for evaluating the FMS system performance are presented. Numerical examples are studied to illustrate a session of the FMS used-DSS interaction.

• 한국공작기계학회논문집
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• 제13권3호
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• pp.76-83
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• 2004

The purpose of this paper is to find an effective control system for a hydraulic motor-load system using matlab. The Hydraulic control system consists of a hydraulic pump, a hydraulic proportional control valve, hydraulic pipelines, a hydraulic motor and a load system. The simulation models were verified by comparing the simulation results with measured data from the real hydraulic proportional position control system. In order to compensate the nonlinear friction characteristics in a hydraulic motor-load system, a discrete time PD controller and Friction torque observer has been applied.

• International Journal of Precision Engineering and Manufacturing
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• 제5권2호
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• pp.22-31
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• 2004

A problem of task rescheduling using a coordinator in a structural decentralized control of supervisory control theory is formulated. we consider that the overall system is divided into a number of local systems. Using an example of a chemical batch reaction process, it has shown that after local supervisors have been established for a given task, a coordinator can be used to solve some rescheduling problems among local plants for new or modified tasks. The coordination system models the interactions of local plants, and is consisting of only the shared events of local plants, so simpler to synthesize. A coordinator is designed based on the specifications given for the coordination system. Under the 'structural' conditions developed in this paper, the combined concurrent actions of the coordinator with the existing local supervisors will achieve the rescheduling requirements. Again since the conditions are structural (not specification-dependent), once the coordination architecture has been established, it can be used for a number of different tasks without further verifications.

• Structural Engineering and Mechanics
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• 제33권5호
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• pp.543-560
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• 2009

The rotating Rayleigh-Timoshenko beam element based on B-spline wavelet on the interval (BSWI) is constructed to discrete short shaft and stiffness disc. The crack is represented by non-dimensional linear spring using linear fracture mechanics theory. The wavelet-based finite element model of rotor system is constructed to solve the first three natural frequencies functions of normalized crack location and depth. The normalized crack location, normalized crack depth and the first three natural frequencies are then employed as the training samples to achieve the neural networks for crack diagnosis. Measured natural frequencies are served as inputs of the trained neural networks and the normalized crack location and depth can be identified. The experimental results of fatigue crack in short shaft is also given.

• 제어로봇시스템학회논문지
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• 제11권8호
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• pp.709-716
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• 2005

As a way to build more efficient and intelligent container cranes for todays hub ports, communication networks are used to interconnect numerous sensors, actuators, controllers, and operator switches and consoles that are spatially distributed over a crane. Various signals such as sensor values and operator's commands are digitized and broadcast on the network instead of using separate wiring cables. This not only makes the design and manufacturing of a crane more efficient, but also easier implementation of intelligent control algorithms. This paper presents the performance evaluation of CAN(Controller Area Network), TTP(Time Triggered Protocol) and Byteflight that can be used for cranes. Through discrete event simulation, several important quantitative performance factors such as the probability of a transmission failure, average system delay (data latency) and maximum system delay have been evaluated.

• 한국경영과학회지
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• 제20권2호
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• pp.159-178
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• 1995

Supervisory control is an approach based on formal language. it is used to model and control discrete event systems in which each discrete event process is represented as an automation. A supervisor is a generator that switches control patterns in such a way that a given discrete evenet process behaves in obedience to various constraints. A flexible manufacturing cell (FMC) is one of discrete evenet systems. Functions necessary for the operation of an FMC are characterized by operational components and informational compoments. The operational components can be modeled using the finite state machines and the informational components can be modeled using the abstract formalism which describes supporting operations of the cell controller. In this paper, we addressed function required for FMC control specification, software engineering aspects on FMC control based on supervisory control, a concept of event queue for resolving synchronization problem, and complexity reduction. Based on the mathematical model of an FMC. we synthesized the controller by integrating a supervisor for FMC with control specification that specifies event-driven operation of the cell controller. The proposed control scheme is stable mathematically so that the system always behaves on a controlled way even under the existence of uncontrollable events. Furthermore, using an event queue concept, we can solve a synchronization problem caused by the violation of instantaneity assumption of supervisory control theory in real life situation. And also, we can propotype a control software rapidly due to the modularity of the proposed control scheme.

• 한국시뮬레이션학회논문지
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• 제7권2호
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• pp.137-152
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• 1998

One of the components that constitute the simulation models is the state variables whose values are determined by the time related simulation process. Embedding rule-based expert systems into the simulation models should provide a systematic way of handling these time-dependent variables without distracting the essential problem solving capabilities of the expert systems which are well suited for expressing the decision making function of complex cases. The expert system, however, is inefficient in dealing with the time elapsing characteristics of target system compare to the simulation models. To solve the problem, this paper provides an interruptible inference engine whose inferencing process can be interrupted when the variables' value, which are used as the parameters of the rules, are not yet determined due to the time dependent nature of the state variables. The process is resumed when the variables are ready. The elapse of time is calculated by time-advance function of the simulation model to which the expert system has been embedded. The example modeling shown exploits the embedded interruptible inferencing capability for the controlling and monitoring of metal grating process.