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다제품 저장창고의 재고관리를 위한 적응 모형예측 제어기
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.11
An inventory control system was developed for a distribution system consisting of a single multiproduct warehouse serving a set of customers and purchasing products from multiple vendors. Purchase orders requesting multiple products are delivered to the warehouse in a process. The receipt of customer orders by the warehouse proceeded in order intervals and in order quantities that are subject to random fluctuations. The objective of warehouse operation is to minimize the total cost while maintaining inventory levels within the warehouse capacity by adjusting the purchase order intervals and quantities. An adaptive model predictive control algorithm was developed using a periodic square wave model to represent the material flows. The adaptive concept incorporated a stabilized minimum variance control-type input calculation coupled with input/output stream parameter predictions. The effectiveness of the scheme was demonstrated using simulations.
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.7
Product shortage which causes backordering and/or lost sales cost is very popular in chemical industries, especially in commodity polymer business. This study deals with backordering cost in the supply chain optimization model under the framework of process-inventory network. Classical economic order quantity model with backordering cost suggested optimal time delay and lot size of the final product delivery. Backordering can be compensated by advancing production/transportation of it or purchasing substitute product from third party as well as product delivery delay in supply chain network. Optimal solutions considering all means to recover shortage are more complicated than the classical one. We found three different solutions depending on parametric range and variable bounds. Optimal capacity of production/transportation processes associated with the product in backordering can be different from that when the product is not in backordering. The product shipping cycle time computed in this study was smaller than that optimized by the classical EOQ model.
간헐적인 운전시간 손실하에 공정-저장조 망구조의 최적설계
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2013 제어·로봇·시스템학회 논문지 Vol.19 No.6
The purpose of this study is to find the analytic solution for determining the optimal capacity (lot-size) of a batch-storage network to meet the finished product demand under infrequent shutdowns. Batch processes are bound to experience random but infrequent operating time losses. Two common remedies for these failures are duplicating another process or increasing the process and storage capacity, both of which are very costly in modern manufacturing systems. An optimization model minimizing the total cost composed of setup and inventory holding costs as well as the capital costs of constructing processes and storage units is pursued with the framework of a batch-storage network of which flows are susceptible to infrequent shutdowns. The superstructure of the plant consists of a network of serially and/or parallel interlinked batch processes and storage units. The processes transform a set of feedstock materials into another set of products with constant conversion factors.A novel production and inventory analysis method, the PSW (Periodic Square Wave) model, is applied. The advantage of the PSW model stems from the fact it provides a set of simple analytic solutions in spite of a realistic description of the material flow between processes and storage units. The resulting simple analytic solution can greatly enhance a proper and quick investment decision at the early plant design stagewhen confronted with diverse economic situations.
회분식 공정-저장조 망구조의 최적설계를 위한 해석적인 방법
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.2
This study overcomes the limitation of the classical lot sizing method developed on the basis of the single product and single stage assumption. The superstructure of the plant considered consists of a network of serially and/or parallelly interlinked processes and storage units. The processes involve chemical reactions with multiple feedstock materials and multiple products. The objective function for optimization is minimizing the total cost composed of setup and inventory holding costs as well as the capital costs of constructing processes and storage units. And the relative optimality of a certain process can be computed to help the sequence decision of optimizing works. The novel Periodic Square Wave (PSW) model was used to analyze production and inventory system. The advantage of the PSW model comes from the fact that the model provides a set of simple analytic solutions in spite of a detailed description of the material flow between processes and storage units. The resulting simple analytic solution can greatly enhance the proper and quick investment decision for plant design and operaton problem confronted in diverse economic situations.
다국적 기업에서 환율과 세금을 고려한 공정-저장조 망구조의 최적설계
이경범(Gyeongbeom Yi),서근학(Kuen-Hack Suh) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.9
This paper presents an integrated analysis of supply chain and financing decisions of multi-national corporation. We construct a model in which multiple currency storage units are installed to manage the currency flows associated with multi-national supply chain activities such as raw material procurement, process operation, inventory control, transportation and finished product sales. Core contribution of this study is to quantitatively investigate the influence of macroscopic economic factors such as exchange rates and taxes on operational decisions. The supply chain is modeled by the Process-Storage Network with recycle streams. The objective function of the optimization is minimizing the opportunity costs of annualized capital investments and currency/material inventories minus the benefit to stockholders interpreted by home currency. The major constraints of the optimization are that the material and currency storage units must not be depleted. A production and inventory analysis formulation, the periodic square wave (PSW) model, provides useful expressions for the upper/lower bounds and average levels of the currency and material inventory holdups. The expressions for the Kuhn-Tucker conditions of the optimization problem are reduced to a subproblem and analytical lot sizing equations. The procurement, production, transportation and financial transaction lot sizes can be determined by analytical expressions after the average flow rates are already known. We show that, when corporate income tax is taken into consideration, the optimal production lot and storage sizes are smaller than is the case when such factors are not considered typically by 20 %.
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.2
The contribution of this study is its quantitative investigation of the influence of macroscopic economic factors such as ownership on operational decisions. The supply chain is modeled as a process-inventory network with recycling streams. The objective function of the optimization involves minimizing the opportunity costs of annualized capital investments and currency/material inventories minus the benefit to stockholders in the numeraire currency. The major constraints of the optimization are that the material and currency storage units must not be depleted. A production and inventory analysis formulation (the periodic square wave model) provides useful expressions for the upper and lower bounds and average levels of the currency and material inventory holdings. The expressions for the Kuhn-Tucker conditions of the optimization problem are reduced to a subproblem and analytical lot-sizing equations. The lot sizes of procurement, production, transportation and financial transaction can be determined by analytical expressions once the average flow rates are known. The optimal value of economic order quantities have changed substantially according to the variation of ownership.
이경범(Gyeongbeom Yi) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.12
An inventory control system was developed for multiproduct batch plants with an arbitrary number of batch processes and storage units. Customer orders are received by the plant at intervals and in quantities that are subject to random fluctuations. The objective of the plant operation is to minimize the total cost while maintaining inventory levels within the storage or warehouse capacity by adjusting the startup times, the quantities of raw material orders, and production batch sizes. An adaptive model-based control algorithm was developed that uses a periodic square wave model to represent the flows of material between the processes and the storage units. The effectiveness of this approach was demonstrated by performing simulations.