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Controle de estoque de peças de reposição em local único: uma revisão da literatura; Single location spare parts inventory control: the state of the art

REGO, José Roberto do; MESQUITA, Marco Aurélio de
Fonte: Associação Brasileira de Engenharia de Produção Publicador: Associação Brasileira de Engenharia de Produção
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.24%
Estoques de peças de reposição atendem necessidades de manutenção e reparo de produtos de consumo, veículos, máquinas e equipamentos industriais, acarretando frequentemente altos custos de capital e forte impacto no nível de serviço aos clientes. A grande multiplicidade de componentes, com ciclos de vida mais curtos e baixas demandas dificultam a gestão destes estoques. Este artigo apresenta revisão da literatura sobre modelos de controle de estoques de peças de reposição em local único, abordando tanto a previsão de demanda quanto o controle de estoques nos diferentes estágios do ciclo de vida das peças. A partir do levantamento bibliográfico, identificam-se algumas lacunas referentes à decisão de estocagem ou não de um item, elaboração de pedidos iniciais e finais, na integração de modelos de previsão de demanda com o controle de estoque e também de estudos de caso na aplicação prática dos modelos.; Spare parts inventory are needed for maintenance and repair of final products, vehicles, industrial machines and equipments, frequently requiring high investments and significantly affecting customer satisfaction. Inventory management is complex due to the large number of different items and low demands. This article presents a literature review on single location spare parts inventory control...

Gestão de estoques de peças de reposição: simulação e análise de modelos com dados empíricos.; Spare parts inventory management: models simulation and analysis with empirical data.

Rego, José Roberto do
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/06/2014 Português
Relevância na Pesquisa
56.05%
Em diversos setores, em especial no automotivo, uma boa gestão dos estoques de peças de reposição tem impacto significativo na satisfação dos clientes e em sua fidelidade aos fabricantes. Neste trabalho foram estudadas diferentes políticas de gestão dos estoques de peças de reposição, para comparar seu desempenho e elaborar recomendações para seu uso. Foram comparados 17 conjuntos de políticas que envolvem diferentes abordagens no registro das demandas (dados individuais de cada pedido versus dados agregados em janelas de tempo semanais e mensais), modelos de previsão (média móvel, Croston modificado SBA) e diferentes formas de modelar a distribuição da demanda durante o Lead-time de ressuprimento (Normal, Gama, Binomial Negativa, composta Poisson-Normal, composta Poisson-Gama). Cada um desses 17 conjuntos de políticas foi simulado sob duas dinâmicas de reparametrização (mensal e semestral) e para quatro objetivos diferentes do nível de serviço (TFR: Target Fill Rate), totalizando 136 simulações para cada item do estoque (SKU). Foram considerados 10.032 SKU's de uma montadora de automóveis instalada no Brasil, com um histórico de seis anos de movimentação. Diferentes recomendações foram elaboradas conforme categorização dos itens já existente na literatura. Os resultados apontaram recomendações distintas para cada TFR...

Análise do problema de controle de estoques dinâmico para demanda não estacionária e lead-time positivo.; Analysis of the dynamic inventory control problem with nonstationary demand and positive lead-time.

Cálipo, Leonardo Gurgel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/08/2014 Português
Relevância na Pesquisa
66.13%
O problema de controle de estoques com demanda não estacionária e lead-time positivo tem se tornado cada vez mais relevante em virtude da crescente tendência de redução do ciclo de vida dos produtos e internacionalização das cadeias de suprimentos. Embora haja uma solução exata para a minimização do custo esperado da política de estoques para este cenário, baseado no método de programação dinâmica, o custo computacional deste método ainda é considerado elevado. Este trabalho detalha e avalia através de simulação o método exato e duas aproximações para a minimização do custo esperado da política de estoques, em termos do desempenho em custo e eficiência computacional. Os resultados experimentais permitem a análise dos métodos disponíveis. Enquanto a abordagem heurística de Bollapragada e Morton, que utiliza o nivelamento da demanda não estacionária, perde desempenho de custo com o aumento do lead-time, a nova heurística proposta, que aproxima os parâmetros da política ótima por valores limitantes, produz resultados sucessivamente melhores com o aumento do lead-time.; The inventory control problem with nonstationary demand and positive lead-time has become increasingly important due to the growing trend of reduction in product life cycle and internationalization of the supply chain. Although there is an exact solution to the minimization of the expected cost of inventory policy on this environment...

LP-based subgradient algorithm for joint pricing and inventory control problems; Linear programming-based subgradient algorithm for joint pricing and inventory control problems

Rao, Tingting
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 94 p.
Português
Relevância na Pesquisa
46.22%
It is important for companies to manage their revenues and -reduce their costs efficiently. These goals can be achieved through effective pricing and inventory control strategies. This thesis studies a joint multi-period pricing and inventory control problem for a make-to-stock manufacturing system. Multiple products are produced under shared production capacity over a finite time horizon. The demand for each product is a function of the prices and no back orders are allowed. Inventory and production costs are linear functions of the levels of inventory and production, respectively. In this thesis, we introduce an iterative gradient-based algorithm. A key idea is that given a demand realization, the cost minimization part of the problem becomes a linear transportation problem. Given this idea, if we knew the optimal demand, we could solve the production problem efficiently. At each iteration of the algorithm, given a demand vector we solve a linear transportation problem and use its dual variables in order to solve a quadratic optimization problem that optimizes the revenue part and generates a new pricing policy. We illustrate computationally that this algorithm obtains the optimal production and pricing policy over the finite time horizon efficiently. The computational experiments in this thesis use a wide range of simulated data. The results show that the algorithm we study in this thesis indeed computes the optimal solution for the joint pricing and inventory control problem and is efficient as compared to solving a reformulation of the problem directly using commercial software. The algorithm proposed in this thesis solves large scale problems and can handle a wide range of nonlinear demand functions.; by Tingting Rao.; Thesis (S.M.)--Massachusetts Institute of Technology...

Modelling of information sharing in capacitated assembly supply chains using simulation

Lanning, Ivor
Fonte: University of Limerick Publicador: University of Limerick
Tipo: info:eu-repo/semantics/doctoralThesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations
Português
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46.26%
peer-reviewed; It has been noted in Lee and Wu (2006) that competition has required the integration of supply chain members and resources through supply chain management (SCM) and that inventory control as a key component of SCM is no exception to this. One manner in which firms in a supply chain can integrate is through information sharing. New technologies have facilitated the movement and processing of data between partners such as electronic data interchange (EDI) in the past, through to more current tools such as on-time, real-time web based portals. In tandem with more readily available information and data, methods for utilisation of such have been explored in research and practice. An array of literature now exists on various aspects of information enabled supply chain management and information enabled inventory control. Considering this, we have proposed a dissertation in the field of information sharing in capacitated assembly supply chains focusing on the inventory control mechanisms applied within. A case study based around a contract manufacturer in the electronics industry provides a vehicle for testing the information sharing propositions within a realistic supply chain. It is complicated on the supply side by multiple suppliers...

A comparison of an alternative inventory control concept with the Navy's existing wholesale inventory control procedures for repairables; NA

Kless, David R.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xv, 87 p.;28 cm.
Português
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The Director of Planning and Operation Research Department, Naval Inventory Control Point (NAVICP) Code M041, requested a study to compare the performance of two sets of inventory control procedures for managing high-cost repairable items. One of these sets is embedded in the Navy's existing wholesale inventory control system. The procedures of this set characterize a periodic review process, which calculates four decision variables in order to manage Navy inventories. These variables represent how much to order, how much to repair, when to order, and when to repair. The other set of procedures are adapted from a commercial software package called Bandwidth Management developed by Stewart- Frazier Tools Inc. Two versions of these latter procedures are modeled in this thesis. These procedures characterize a periodic review process, which calculates three decision variables. These variables represent how much to deliver, how much to repair, and when to repair. This thesis uses simulation to model the two sets of procedures and to compare their performance with respect to three formal measures of effectiveness adopted by NAVICP: Supply Material Availability (SMA), Average Delay for a Delayed Requisition (ADDR), and Average Monthly Investment Level (AMIL). The comparison results of the thesis indicate that the existing Navy inventory procedures generate better performance in all three formal measures of effectiveness.; NA; U.S. Navy (U.S.N.) author.

Review and analysis of Selected Items Management (SIM) inventory program aboard US surface ships

Axinto, Mark Ivan D.; Giles, Michael Scott
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Formato: xx, 87 p. : ill.; 28 cm.
Português
Relevância na Pesquisa
56.23%
MBA Professional Report; The purpose of this MBA project is to carry out an exploratory study and conduct an analysis to determine if there are any correlations between shipboard supply management practices/priorities and SIM Issue Effectiveness rates. Shipboard SIM inventories range from approximately 300 to 350 line items on average per ship. While SIM items constitute only a small portion of the ship's entire COSAL spare parts inventory, they are critical to the ship's material condition and to its preventive and corrective maintenance programs. Consequently, effective and efficient SIM inventory control is crucial and has a significant impact on the ship's mission readiness. However, surface ships reporting their monthly inventory and performance data to the Type Commander indicate some of the ships are not meeting their SIM Issue Effectiveness goals. The project investigated the variances to determine if they can be explained using correlations with other variables. In addition, the authors analyzed SIM inventory to determine if a Business Processing Reengineering (BPR) through virtual stock consolidation with a shift in emphasis from individual shipboard support to a more global level can result in risk mitigation of SIM stock outs. The project compared common commercial inventory control practices to shipboard inventory procedures to examine possible application of best practices.; US Navy (USN) author.

Process redesign of the Norwegian Navy Materiel Command's replenishment of inventory items

Tysseland, Bernt E
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Português
Relevância na Pesquisa
56.18%
Approved for public release; distribution is unlimited; The Norwegian Navy Materiel Command must keep inventory in order to serve its customers. Service level is established as a measure of effectiveness on delivery from inventory. Long replenishment lead-time, with variability in both lead-time itself and lead-time demand, make it hard to achieve the desired service level. The lead-time becomes costly, both in form of holding cost of safety stock and in form of stock-outs. Current inventory control policy used at the Materiel Command is presented, and compared to theoretical inventory control models. Computer simulation is used to measure current administrative lead-time at the Norwegian Navy Materiel Command. Two proposals for redesign of existing replenishment process are built as simulation models, and the effect on administrative lead-time and associated variability is measured. The first proposal is to consolidate two separate procurement offices into one. The second proposal is to introduce, and use electronic commerce in the replenishment process. It is concluded that both redesign proposals will reduce administrative lead-time, variability and hence cost. Benefits from an introduction of electronic commerce will yield a yearly cost saving of at least 4...

A wholesale level consumable item inventory model for non-stationary demand patterns; NA

Robillard, Glenn C.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 260 p.;28 cm.
Português
Relevância na Pesquisa
56.14%
The U.S. military presently manages about 88 billion dollars in spare and repair parts, consumables, and other support items. Department of Defense (DOD) inventory models which help wholesale item managers make inventory decisions concerning these items are based on the assumption that mean demand remains constant over time. In DOD this assumption is rarely met. During periods of declining demand, such as that associated with force reduction or equipment retirement, the inventory models usually keep stock levels too high, generating excess material. Recently, the amount of excess in DOD was estimated to be as high as 40 billion dollars. On the other extreme, during periods of increasing demand, the models generally provide too little stock, resulting in poor weapons system support. The purpose of this research was to develop an inventory model which does not rely on the assumption that mean demand is stationary. Use of the model would be appropriate when a known or predictable increase or decrease in mean demand is forecasted. Through simulation the model's performance was evaluated and compared with that of the Navy's Uniform Inventory Control Program (UICP) model. The results indicate that the proposed model significantly outperforms the existing model when mean demand is non- stationary. Additionally...

Evaluation of the inventory and accountability practices of common support equipment throughout Pacific and Atlantic Fleets

McCallister, Frank F; McCallister, Joyce L.; Pridgen, Robert D.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Português
Relevância na Pesquisa
46.21%
Approved for public release; distribution is unlimited.; Within Naval Aviation, Common Support Equipment (CSE) plays a critical yet unglamorous role in maintaining aircraft material readiness. Defense of CSE dollars is difficult because the Output of Aviation Support Equipment is not measurable. The ability to quantity and defend that role has been the nemesis of the Aviation Support Equipment Integrated Program Team members over the past two budget cycles. This study's intent is to provide an argument in defense of adequate program funding. The premise of this argument is: Inventory validity is a major consideration in making sound investment decisions. If the Fleet SE inventory validity is within acceptable limits, then the Fleet's input into the re-capitalization decision support system is valid. If the Fleet's SE inventory validity is poor, then the Fleet's buyout input is suspect. The foundation of this research is to determine how accurately the Fleet's on-hand assets reflect in the automated inventory database used to manage those assets. This research concludes that the mean SE validity for a reporting custodian's Intermediate Maintenance Activity (IMA) or 0rganizational Maintenance Activity (OMA) account is 72.4%. Fleet Individual Material Readiness List (IMRL) inventory control processes are hampered by a lack of quantifiable metrics...

Gestão de estoque no setor de varejo calçadista: abordagem via análise multivariada e teoria do controle ótimo

Alves Junior, Paulo Nocera
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 108 f. : il.
Português
Relevância na Pesquisa
46.26%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia de Produção - FEB; Um estoque inadequado pode inviabilizar um negócio, e uma caracterização pode influenciar em seu controle e gestão. O objetivo deste trabalho é avaliar a gestão de estoque do setor de varejo calçadista através do auxílio de técnicas de Análise Multivariada e da teoria do Controle Ótimo. Foi aplicada a Análise Multivariada com a finalidade de criar índices para caracterizar as lojas de calçados; criar uma função discriminante para avaliar a diferença entre grupos de lojas com e sem excesso de estoque; utilizar esta função para classificar novas lojas nesses grupos; verificar os grupos de lojas e adaptar um modelo de controle de estoque com a Teoria do Controle Ótimo de Sethi e Thompson (2006). Para isso foram utilizados questionários para coletar dados de 30 lojas da região polo do interior do Estado de São Paulo, que foram divididas em grupos. Utilizando análise multivariada o trabalho cria dois índices de segurança através de componentes principais, para caracterizar as lojas e as variáveis mais importantes, e através da análise discriminante cria uma função discriminantes linear de Fisher para avaliar diferença significativa entre gupos e classificar as lojas...

Implementación de un Sistema de Registro y Control de Inventario para el Almacén Acabados y Revestimientos 1A - sede Santa Lucia.; Implementing a Registration System for Inventory Control and Warehouse in the establishment Acabados y Revestimientos 1A location of Santa Lucia

Linares Beltrán, Diana; Ortiz Cárdenas, Fernando
Fonte: Universidad Militar Nueva Granada; Facultad de Ingeniería; Especialización en Gerencia Integral de Proyectos Publicador: Universidad Militar Nueva Granada; Facultad de Ingeniería; Especialización en Gerencia Integral de Proyectos
Tipo: bachelorThesis; Trabajo de grado Formato: pdf; pdf
Português
Relevância na Pesquisa
56.13%
En la actualidad, la mayoría de las empresas y negocios independientemente del nivel de sus ventas, cuentan con una herramienta tecnológica que soporte el desarrollo normal de sus actividades ofreciendo facilidades de manejo de información que sirve como soporte a la hora de tomar decisiones al interior de estas. Sin embargo, en el establecimiento Acabados y Revestimientos 1A Sede Santa Lucia, no se cuenta con ningún soporte tecnológico, a la fecha el manejo total del almacén se realiza de forma manual lo que lo hace menos eficiente. Por esta razón, se realiza un diagnóstico detallado de los procesos que requieren una mejora con el fin de proponer un sistema de registro y control de inventario que optimice dichos procesos, incremente las ventas y reduzca los costos de mantenimiento del establecimiento.; Currently, most companies and businesses regardless of the level of sales, have a technological tool that supports the normal development of their activities by providing information management tools that serves as a support for decision-making within of these. However, the establishment Acabados y Revestimientos 1A location of Santa Lucia, do not have any technological support, to date the total warehouse management is done manually which makes it less efficient. For this reason...

Fab cycle time improvement through inventory control : a wafer starts approach

Ward, Matthew John
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 60 p.
Português
Relevância na Pesquisa
46.27%
Intel's Colorado Springs wafer fabrication facility, known internally as F23, has undertaken several initiatives to reduce cycle time including High Precision Maintenance (HPM), content reduction through the application of Manufacturing Excellence (mX), effective utilization of production equipment, and aggressive inventory control. Each of these efforts has contributed to the marked improvement F23 achieved throughout 2006. F23's cycle time efficiency, the ratio of raw process cycle time to actual fab cycle time, improved from 12% (worst amongst Intel facilities) to greater than 35% (best amongst Intel sites), and overall cycle time was reduced by more than 61% in 2006. Inventory control was found to have a major impact on factory cycle time and performance. F23 controls its factory work-in-process, WIP, inventory through the F23 Wafer Starts Protocol. F23 utilizes Little's Law (Cycle Time = Inventory / Output) to identify target WIP inventory levels required to achieve particular cycle time goals. The target inventory is then achieved by modulating wafer starts. To do this, the Wafer Starts Protocol monitors the inventory of the overall fab and the constraint operations and suggests the amount of wafers to start for each shift.; (cont.) Maintaining the target inventory level drives the overall factory cycle time towards the cycle time goal. Using the starts protocol...

Distributionally robust inventory control when demand is a martingale

Xin, Linwei; Goldberg, David A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/11/2015 Português
Relevância na Pesquisa
56.09%
Demand forecasting plays an important role in many inventory control problems. To mitigate the potential harms of model misspecification, various forms of distributionally robust optimization have been applied. Although many of these methodologies suffer from the problem of time-inconsistency, the work of Klabjan et al. established a general time-consistent framework for such problems by connecting to the literature on robust Markov decision processes. Motivated by the fact that many forecasting models exhibit special structure, as well as a desire to understand the impact of positing different dependency structures, in this paper we formulate and solve a time-consistent distributionally robust multi-stage newsvendor model which naturally unifies and robustifies several inventory models with forecasting. In particular, many simple models of demand forecasting have the feature that demand evolves as a martingale. We consider a robust variant of such models, in which the sequence of future demands may be any martingale with given mean and support. Under such a model, past realizations of demand are naturally incorporated into the structure of the uncertainty set going forwards. We explicitly compute the minimax optimal policy (and worst-case distribution) in closed form...

On-line Non-stationary Inventory Control using Champion Competition

Mao, Jianfeng
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/08/2014 Português
Relevância na Pesquisa
55.95%
The commonly adopted assumption of stationary demands cannot actually reflect fluctuating demands and will weaken solution effectiveness in real practice. We consider an On-line Non-stationary Inventory Control Problem (ONICP), in which no specific assumption is imposed on demands and their probability distributions are allowed to vary over periods and correlate with each other. The nature of non-stationary demands disables the optimality of static (s,S) policies and the applicability of its corresponding algorithms. The ONICP becomes computationally intractable by using general Simulation-based Optimization (SO) methods, especially under an on-line decision-making environment with no luxury of time and computing resources to afford the huge computational burden. We develop a new SO method, termed "Champion Competition" (CC), which provides a different framework and bypasses the time-consuming sample average routine adopted in general SO methods. An alternate type of optimal solution, termed "Champion Solution", is pursued in the CC framework, which coincides the traditional optimality sense under certain conditions and serves as a near-optimal solution for general cases. The CC can reduce the complexity of general SO methods by orders of magnitude in solving a class of SO problems...

Hierarchical design of decentralized control structures for the Tennessee Eastman Process

Antelo, L. T.; Banga, Julio R.; Alonso, Antonio A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 522180 bytes; application/pdf
Português
Relevância na Pesquisa
56.18%
21 pages, 26 figures.-- Issue title: Networked and Complex Systems S.I. - Control of Networked and Complex Process Systems.-- Available online 13 November 2007.; In this work, the systematic approach to a plant-wide control design developed in a previous work by the authors [Antelo, L. T., Otero-Muras, I., Banga, J. R, & Alonso, A. A. (2007). A systematic approach to plant-wide control based on thermodynamics. Computers & and Chemical Engineering, 31(7), 677–691] is applied to derive robust decentralized controllers in the challenging benchmark of the Tennessee Eastman Process (TEP). The hierarchical control design is based on the link between thermodynamics and passivity theory as well as on the fundamentals of process networks. First, the TEP process network is decomposed into abstract mass and energy inventory networks. It is over these subnetworks where conceptual inventory control loops are developed to guarantee the convergence of the mass and energy inventories to a given compact region defined by constant inventories. Thermodynamics gives us a function (the entropy) which has a definite curvature (concavity) over these compact regions of the state space. This function can then be employed on these regions to derive natural storage or function candidates which can be used in designing controllers for stabilizing the network. The last step in the systematic control design procedure will be the realization of the controllers using the available degrees of freedom of the process. The inventory control laws will be obtained as a composition of control loops implemented over the real manipulated variables (degrees of freedom).; The authors acknowledge the financial support received from the Spanish Government (MCyT Projects PPQ2001-3643) and Xunta de Galicia (PGIDIT02-PXIC40209PN).; Peer reviewed

A systematic approach to plant-wide control based on thermodynamics

Antelo, L. T.; Otero-Muras, Irene; Banga, Julio R.; Alonso, Antonio A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 522180 bytes; application/pdf
Português
Relevância na Pesquisa
56.16%
15 pages, 23 figures.-- ESCAPE-15 - Selected Papers from the 15th European Symposium on Computer Aided Process Engineering held in Barcelona, Spain, May 29-June 1, 2005.-- Available online 26 December 2006.; In this work, a systematic approach to plant-wide control design is proposed. The method combines ingredients from process networks, thermodynamics and systems theory to derive robust decentralized controllers that will ensure complete plant stability. As a first step, the considered process system is decomposed into abstract mass and energy inventory networks. In this framework, conceptual inventory control loops are then designed for the mass and energy layers to guarantee that the states of the plant, both in terms of extensive and intensive properties, will converge to a compact convex region defined by constant inventories. This result by itself does not ensure the convergence of intensive variables to a desired operation point as complex dynamic phenomena such as multiplicities may appear in the invariant set. In order to avoid these phenomena, thermodynamics naturally provides the designer, in these convex regions, with a legitimate storage or Lyapunov function candidate, the entropy, that can be employed to ensure global stability. Based on this...

Inventory control in supply chains an internal model control approach /

García Salcedo, Carlos Andrés
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis Formato: application/pdf
Publicado em //2013 Português
Relevância na Pesquisa
56.33%
Esta tesis se basa en el diseño de estrategias de gestión de inventario en cadenas de suministro usando la teoría de control. El principal objetivo es proponer un esquema de control para resolver los principales problemas que aparecen en el controla gestión de inventario de una cadena de suministro (incertidumbre en el retardo, el efecto látigo y el déficit de inventario). Este objetivo principal se divide en dos objetivos: 1. La neutralización de los efectos causados por el retardo de entrega de un pedido. 2. Diseño de políticas de inventario que permitan un balance entre el rechazo a la perturbación (demanda) y el seguimiento del inventario objetivo. Dado que el esquema de control por modelo interno (IMC) permite tratar los objetivos (1) y (2) bajo el mismo paradigma de control, pero de una manera disociada, éste se presenta en esta tesis como una nueva política de reposición de inventario en cadenas de suministro. Sin embargo, el IMC requiere el conocimiento del retardo para compensar sus efectos. Esta situación no es viable cuando el retardo cambia durante el proceso, situación común en las cadenas de suministro. Por lo tanto, la investigación empieza con la identificación del retardo. Así, en esta tesis se formula un algoritmo de identificación que permite estimar el verdadero valor de los retardos de la cadena de suministro. Estos valores se utilizan para adaptar el bloque de retardos en el esquema de control. De ese modo...

Control of a production-inventory system using a pid and demand prediction based controller

Tosetti,S.; Patiño,D.; Capraro,F.; Gambier,A.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2009 Português
Relevância na Pesquisa
46.23%
The need of reducing inventory levels as much as possible without loosing sales opportunities is an important goal not only for small but also for mid-size and large companies, on account of the high costs associated with large inventory stocks. In general, the performance of inventory systems is also affected by the Bullwhip effect caused, among other factors, by non-zero lead times. This paper proposes an automatic pipeline feedback order-based production control system (APIOBPCS) considering a demand with cyclic and stochastic components. The dynamics and delays of the production process are modeled as a pure delay. The control system structure consists of a PID controller and demand prediction based on an Extended Kalman Filter (EKF). The main objective of the controller is to stabilize and regulate the inventory levels about a desired set-point. The extended Kalman Filter estimates the parameters of a Volterra time-series model to predict future values of the demand. The control system is evaluated by simulations, showing a good performance and better results than those achieved by using traditional inventory control techniques.

Supervisory control of an HEV using an inventory control approach

Pérez,L. V.; Bossio,G. R.; Moitre,D.; García,G. O.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 Português
Relevância na Pesquisa
56%
Hybrid electric vehicles (HEV) are those equipped with two or more energy sources, usually, a fuel tank with its associated internal combustion engine (ICE) and an electrical storage system (ESS), typically a bank of batteries. In order to efficiently operate the system it is necessary to determine the instantaneous power split between the two sources when the vehicle performs a predetermined duty cycle. In this work, this problem is posed as an optimal control problem with constraints, specifically, as an inventory control problem and solved using dynamic programming (DP). Results obtained for the HEV being developed in the Applied Electronics Group, School of Engineering, National University of Río Cuarto are shown.