The Experts below are selected from a list of 8319 Experts worldwide ranked by ideXlab platform
El-kebir Boukas - One of the best experts on this subject based on the ideXlab platform.
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piecewise linear h controller synthesis with applications to inventory control of switched production systems
Automatica, 2006Co-Authors: Luis Rodrigues, El-kebir BoukasAbstract:This paper focuses on the problem of inventory control of production systems. The main contribution of the paper is that production systems are modeled as constrained switched linear systems and the inventory control problem is formulated as a constrained switched H"~ problem with a piecewise-affine (PWA) control law. The switching variable for the production systems modeled in this paper is the Stock Level. When the Stock Level is positive, some of the perishable produced parts are being stored and will deteriorate with time at a given rate. When the Stock Level is negative it leads to backorders, which means that orders for production of parts are coming in and there are no Stocked parts to immediately meet the demand. A state feedback controller that forces the Stock Level to be kept close to zero (sometimes called a just-in-time policy), even when there are fluctuations in the demand, will be designed in this paper using H"~ control theory. The synthesis of the state feedback controller that quadratically stabilizes the production dynamics and at the same time rejects the external demand fluctuation (treated as a disturbance) is cast as a set of linear matrix inequalities (LMIs). Two numerical examples are provided to show the effectiveness of the proposed method.
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Piecewise-Linear H∞ Inventory Control of Switched Production Systems
Proceedings of the 45th IEEE Conference on Decision and Control, 2006Co-Authors: Luis Rodrigues, El-kebir BoukasAbstract:This paper focuses on the problem of inventory control of production systems. The main contribution of the paper is that production systems are modeled as constrained switched linear systems and the inventory control problem is formulated as a constrained switched H∞ problem with a piecewise-affine (PWA) control law. The switching variable for the production systems modeled in this paper is the Stock Level. When the Stock Level is positive, some of the perishable produced parts are being stored and will deteriorate with time at a given rate. When the Stock Level is negative it leads to backorders, which means that orders for production of parts are coming in and there are no Stocked parts to immediately meet the demand. A state feedback controller that forces the Stock Level to be kept close to zero (sometimes called a just-in-time policy), even when there are fluctuations in the demand, will be designed in this paper using H∞ control theory and will be formulated as a set of linear matrix inequalities (LMIs). A numerical example is provided to show the effectiveness of the proposed method
R Haijema - One of the best experts on this subject based on the ideXlab platform.
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Stock Level dependent ordering of perishables a comparison of hybrid base Stock and constant order policies
International Journal of Production Economics, 2016Co-Authors: R Haijema, Stefan MinnerAbstract:In practice, traditional Stock-Level dependent policies, like base-Stock policies (BSP) and constant order policies (COP), are commonly used for replenishing inventories of perishable products at retailers. These policies are preferred for being easy to implement: they only require information on the total number of products in Stock, but not differentiated by their age. In this paper, we analyze a number of new and existing hybrid BSP-COP policies. These policies have different complexities, but, so far, they have not been systematically compared with respect to their performance. By simulation-based optimization, the parameter values of the policies are determined. For this purpose, search ranges for the parameter values are provided. Based on an extensive set of experiments, insights are gained on when to apply which policy. The results show that two newly proposed enhancements of traditional base-Stock policies, in particular, perform well and can be recommended for practical implementation.
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a new class of Stock Level dependent ordering policies for perishables with a short maximum shelf life
International Journal of Production Economics, 2013Co-Authors: R HaijemaAbstract:Many perishables such as fresh food and blood platelet concentrates are characterized by a short maximum shelf life. As demand is often highly uncertain the outdating and shortages figures can be very high, especially when frequent replenishment is not possible or inefficient due to fixed ordering cost. We present a new class of Stock-Level dependent ordering policies: the (s,S,q,Q) policy, which is a periodic review (s,S) policy with the order quantity restricted by a minimum (q) and maximum (Q). Optimal (weekday dependent) parameter values are derived by dynamic programming and simulation. The (s,S,q,Q) policy performs nearly optimal and improves the (s,S) policies in many cases by 4–25%.
Luis Rodrigues - One of the best experts on this subject based on the ideXlab platform.
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piecewise linear h controller synthesis with applications to inventory control of switched production systems
Automatica, 2006Co-Authors: Luis Rodrigues, El-kebir BoukasAbstract:This paper focuses on the problem of inventory control of production systems. The main contribution of the paper is that production systems are modeled as constrained switched linear systems and the inventory control problem is formulated as a constrained switched H"~ problem with a piecewise-affine (PWA) control law. The switching variable for the production systems modeled in this paper is the Stock Level. When the Stock Level is positive, some of the perishable produced parts are being stored and will deteriorate with time at a given rate. When the Stock Level is negative it leads to backorders, which means that orders for production of parts are coming in and there are no Stocked parts to immediately meet the demand. A state feedback controller that forces the Stock Level to be kept close to zero (sometimes called a just-in-time policy), even when there are fluctuations in the demand, will be designed in this paper using H"~ control theory. The synthesis of the state feedback controller that quadratically stabilizes the production dynamics and at the same time rejects the external demand fluctuation (treated as a disturbance) is cast as a set of linear matrix inequalities (LMIs). Two numerical examples are provided to show the effectiveness of the proposed method.
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Piecewise-Linear H∞ Inventory Control of Switched Production Systems
Proceedings of the 45th IEEE Conference on Decision and Control, 2006Co-Authors: Luis Rodrigues, El-kebir BoukasAbstract:This paper focuses on the problem of inventory control of production systems. The main contribution of the paper is that production systems are modeled as constrained switched linear systems and the inventory control problem is formulated as a constrained switched H∞ problem with a piecewise-affine (PWA) control law. The switching variable for the production systems modeled in this paper is the Stock Level. When the Stock Level is positive, some of the perishable produced parts are being stored and will deteriorate with time at a given rate. When the Stock Level is negative it leads to backorders, which means that orders for production of parts are coming in and there are no Stocked parts to immediately meet the demand. A state feedback controller that forces the Stock Level to be kept close to zero (sometimes called a just-in-time policy), even when there are fluctuations in the demand, will be designed in this paper using H∞ control theory and will be formulated as a set of linear matrix inequalities (LMIs). A numerical example is provided to show the effectiveness of the proposed method
Hesham K Alfares - One of the best experts on this subject based on the ideXlab platform.
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inventory model with Stock Level dependent demand rate and variable holding cost
International Journal of Production Economics, 2007Co-Authors: Hesham K AlfaresAbstract:Inventory models in which the demand rate depends on the inventory Level are based on the common real-life observation that greater product availability tends to stimulate more sales. Previous models incorporating inventory-Level dependent demand rate assume that the holding cost is constant for the entire inventory cycle. This paper considers the inventory policy for an item with a Stock-Level dependent demand rate and a storage-time dependent holding cost. The holding cost per unit of the item per unit time is assumed to be an increasing function of the time spent in storage. Two time-dependent holding cost step functions are considered: Retroactive holding cost increase, and incremental holding cost increase. Procedures are developed for determining the optimal order quantity and the optimal cycle time for both cost structures.
Shanlin Yang - One of the best experts on this subject based on the ideXlab platform.
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a two warehouse inventory model for items with Stock Level dependent demand rate
International Journal of Production Economics, 2005Co-Authors: Yongwu Zhou, Shanlin YangAbstract:Abstract As we all know, the capacity of any warehouse is limited. In practice, however, there usually exist various factors that induce the decision-maker of the inventory system (especially those with inventory-dependent demand rate) to order more items than can be held in his own warehouse. Therefore, for the decision maker, it is very practical to determine whether or not to rent other warehouses and what order or shipment policy to adopt if other warehouses are indeed needed. In this paper, a deterministic inventory model with inventory-dependent demand rate and two separate warehouses (own warehouse, abbreviated as OW and rented warehouse, abbreviated as RW) is developed to help the decision-maker to make the decision. The model is formulated by assuming that the demand rate is a polynomial form of current inventory Level, the Stock is transferred from RW to OW under a bulk release pattern and the transportation cost is taken to be dependent on the transported amount. Shortages are not allowed. Presented here are sufficient and necessary conditions of judging whether to rent RW and the solution procedure of the proposed model. The solution procedure is illustrated with some numerical examples. Sensitivity analysis of parameters is also shown.
