Papers by D. Van Oudheusden
This paper aims to develop a practical finite capacity MRP (FCMRP) system based on the needs of a... more This paper aims to develop a practical finite capacity MRP (FCMRP) system based on the needs of an automotive parts manufacturing company in Thailand. The approach includes a linear goal programming model to determine the optimal start time of each operation to minimize the sum of penalty points incurred by exceeding the goals of total earliness, total tardiness, and average flow-time considering the finite capacity of all work centers and precedence of operations. Important factors of the proposed FCMRP system are penalty weights and dispatching rules. Effects of these factors on the performance measures are statistically analyzed based on a real situation of an auto-part factory. Statistical results show that the dispatching rules and penalty weights have significant effects on the performance measures. The proposed FCMRP system offers a good trade- off between conflicting performance measures and results in the best weighted average performance measures when compared to conventio...
Advanced Materials Research, 2005
Abstract Both the topics of Computer Aided Process Planning and Production Planning in the contex... more Abstract Both the topics of Computer Aided Process Planning and Production Planning in the context of sheet metal air bending have been presented as standalone topics previously. This paper will focus on the interaction between both modules. Choices made by the ...
Transportation Research Part B: Methodological, 2007
To improve the robustness of timetables for a network of passenger train services, this paper see... more To improve the robustness of timetables for a network of passenger train services, this paper seeks to minimize a waiting cost function that includes running time supplements and different types of waiting times and late arrivals. The approach is applied to the whole intercity (IC) network of the Belgian railways. The IC network consists of 14 fast trains connecting all major cities in Belgium. In the first phase of the approach, ideal running time supplements are calculated to safeguard connections when the feeder train is late. These supplements are based on the delay distributions of the trains, the passenger counts and on the weighting of different types of waiting times. In a second phase, continuous Linear Programming (LP) is used to construct an improved timetable with well-scheduled connections and, whenever possible, with ideal running time supplements. Simulation evaluates different timetables and makes further improvement of the LP timetable possible. For the case of the IC network, the final result is a timetable with suitable transfer times and a waiting cost, that is, 40% lower than the current timetable. Since continuous LP modelling is applied, the proposed technique is very promising for developing better timetables -even for very extensive railway networks.
Studies in Computational Intelligence, 2008
... presents a two–level algorithm to tackle this problem: an upper–level algorithm is used to de... more ... presents a two–level algorithm to tackle this problem: an upper–level algorithm is used to determine the most appropriate set of ... Automated Parameterisation of a Metaheuristic ... ti,last is the time from the current location of the tour to location i. A roulette wheel selection is used to ...
Lecture Notes in Economics and Mathematical Systems, 2009
In recent years, a lot of work has been done for supporting the operational management of contain... more In recent years, a lot of work has been done for supporting the operational management of container handling operations in seaports. However, the train-totrain container transshipment problem, in which containers have to be interchanged between trains, has been largely ignored. Containers are handled by rail mounted cranes. The time needed for completing the transshipments using multiple cranes is to be minimised. The contribution of this paper is to put forward a metaheuristic approach to deal with this challenging problem that has not been tackled before. The problem is first decomposed into three subproblems: (1) the assignment of a destination to each train, (2) the determination of container positions on the train wagons and (3) the determination of the operations sequence for the different cranes that perform the actual transshipments. The first subproblem is solved in a heuristic manner while the second subproblem is solved to optimality. The third subproblem is tackled by a Variable Neighbourhood Descent metaheuristic procedure. This approach is validated on a set of generated test problems. Solutions are obtained in a reasonable amount of calculation time.
2008 IEEE International Conference on Industrial Engineering and Engineering Management, IEEM 2008, 2008
ABSTRACT To compete with alternative production methods, sheet metal working firms need to improv... more ABSTRACT To compete with alternative production methods, sheet metal working firms need to improve continuously. Improvement efforts do not solely focus on the production processes, but also on other aspects of the production chain. Production planning is one of those aspects that need to be optimized. The presented research focuses on production planning optimization for sheet metal shops with a cutting stage and a bending stage. The combination of the production plans of the individual processes does not result in a globally optimal production plan. Consequently, both processes need to be integrated for production planning. In this paper, an integer programming formulation is presented for the multiple-machine two-stage sheet metal shop production planning problem. Numerous real-life test cases are used to benchmark the approach against the current way of planning. To limit the computational time, a dedicated variable neighborhood search procedure is presented.
Key Engineering Materials, 2007
Over the past few years both sheet metal process planning and production planning issues received... more Over the past few years both sheet metal process planning and production planning issues received increased attention. For process planning of the laser cutting process, nesting algorithms are developed in order to decrease the waste material. Additionally, algorithms are available for path planning, i.e. determining the best sequence for cutting the different parts. Production planning is mainly performed based on the ability to fill a sheet. For air bending, process planning focuses on bend sequencing and tool selection, while production planning optimization aims at minimizing time consuming setups between the different production layouts at the press brake. However, when integrating both processes, the benefits from individual optimization counteract one another: good nestings at the laser machine can create additional setups at the press brake, hence increasing the makespan. An integrated approach is proposed to verify whether this problem can be solved by already taking into account possible setups at the press brake in the early nesting stage. Integration of both processes aims at an optimal combination of parts on a sheet and minimization of the setups at the press brake. In this paper, an overview of a modeling effort addressing both goals is proposed. When combining parts on a sheet, preference is given to parts requiring the same production layout at the press brake. If this is impossible, production layouts with low changeover times are preferred. Industrial cases are used to verify the applicability of the proposed model. The results are compared to a reference approach where nesting is performed with dedicated software and planning for air bending is based on an operator's experience. Compared to this reference approach, a makespan reduction and a setup time reduction can be observed. The planning is generated almost instantaneously and no additional sheets are required compared to the reference approach. Future research will focus on expanding the model and verifying its applicability on a larger data-set.
Transportation Research Part E: Logistics and Transportation Review, 2007
In this paper we present the use of game theoretic models to analyse the cost allocation problem ... more In this paper we present the use of game theoretic models to analyse the cost allocation problem in the context of repairable spare parts pooling. Two situations are studied. In the first situation, all pooling members fully cooperate without having self-interest. We use the core concept from cooperative game theory as the basis for designing a fair cost allocation. In the second situation, competition exists as each member has an interest in maximizing his own benefit. Using the concept of Nash equilibrium, we show that the cost allocation policy influences the companies in making their inventory decisions.
Transportation Research Part E: Logistics and Transportation Review, 2009
We apply simulation optimization to determine the optimal design and stock distribution for a sin... more We apply simulation optimization to determine the optimal design and stock distribution for a single item supply system with a one-for-one replenishment policy. We investigate both the effect of the number of echelons and the degree of resupply flexibility, considering single-echelon and two-echelon systems with either no resupply flexibility, lateral transhipments only or both lateral transhipments and emergency deliveries. We show that the implementation of an emergency delivery option allows an augmentation of the fraction of customers served by lateral transhipments and that increased resupply flexibility enables increasingly important cost savings. the air . The primary challenge faced by every manufacturer is to deliver a service that meets pre-specified commitments (often formalized in a service level agreement) in the most cost-effective manner possible.
Production Planning & Control, 2009
Sheet metal working remains an important industry. It is argued that, to be competitive, the comp... more Sheet metal working remains an important industry. It is argued that, to be competitive, the complete production chain needs to be optimised. Therefore, this article focuses on the optimisation of the production plan. The sheet metal shop is configured as a two-stage flow shop with laser cutting and air bending. In the literature, theoretical production planning models can be found
Operations Research, 2005
The general routing problem (GRP) is the problem of finding a minimum length tour, visiting a num... more The general routing problem (GRP) is the problem of finding a minimum length tour, visiting a number of specified vertices and edges in an undirected graph. In this paper, we describe how the well-known 2-opt and 3-opt local search procedures for node routing problems ...
Operational Research, 2007
Violent crimes such as ram raids and armed robberies have a substantial impact on the physical, e... more Violent crimes such as ram raids and armed robberies have a substantial impact on the physical, emotional and material wellbeing of victims. Therefore these crimes typically receive the highest priority from the police. In this paper we present prescriptive models to deploy police patrol units to improve their ability to respond timely to such crimes. These models can also help police administrators to assess the effectiveness of proposals that attempt to advance the moment when the police arrives on the scene. The models are illustrated by an application to real-life data from a Belgian police zone from which some general guidelines are derived.
Journal of the Operational Research Society, 2005
ABSTRACT This paper deals with the analysis of a multi-item, continuous review model of a multi-l... more ABSTRACT This paper deals with the analysis of a multi-item, continuous review model of a multi-location inventory system of repairable spare parts, in which lateral and emergency shipments occur in response of stock-outs. The objective is to determine close-to-optimal stocking policies minimizing the total cost for inventory holding, lateral transshipments, and emergency shipments subject to a target level for the average waiting times at all locations. We structure the optimization problem as a combinatorial problem and four different heuristics are developed and evaluated in terms of their total costs and computation times. It is shown that the greedy-type heuristic has the best performance. A numerical study is carried out to look at the relative cost savings obtained from the use of multi-item approach and lateral transshipments.Journal of the Operational Research Society (2005) 56, 1419–1430. doi:10.1057/palgrave.jors.2601952 Published online 16 March 2005
International Journal of Production Research, 2007
ABSTRACT Mathematical models, sometimes implemented in commercial software, allow optimization of... more ABSTRACT Mathematical models, sometimes implemented in commercial software, allow optimization of individual machines based on specific criteria. For sheet-metal operations, cutting, punching, and air bending are the subject of extensive research, and both process planning and production planning can nowadays be automated to some extent. 2D cutting operations focus on minimization of waste material, and 3D bending operations focus on minimizing time-consuming setups. However, when integrating both processes, the benefits from separate machine optimization may disappear. Optimized nesting of parts at the laser can create additional setups at the pressbrake. In this paper, the use of OR techniques for integrated production planning for sheet-metal operations is analysed. An integrated production planning model is proposed, aimed at creating feasible groupings of parts while at the same time minimizing the number of time-consuming setups at the pressbrake. Simulation is used to confirm the applicability of the integrated approach. A case study is carried out to confirm the model's ability to generate feasible production plans. Those production plans are compared with a reference case, representing the current way of planning. An average makespan reduction of 4.11% is obtained, resulting in average yearly savings of about 10 days.
International Journal of Production Research, 2006
This paper discusses the planning module of system that has been developed in a research project ... more This paper discusses the planning module of system that has been developed in a research project investigating the possibilities for automatic planning of press brakes. Only limited attention has been given to production-planning problems for bending processes in the ...
International Journal of Production Economics, 2005
This paper presents an analytical model for determining spare parts stocking levels in a single-i... more This paper presents an analytical model for determining spare parts stocking levels in a single-item, multi-hub, multi-company, repairable inventory system in which complete pooling of stock is permitted among the hubs and companies. The objective is to minimize the total system cost which consists of inventory holding cost, downtime cost and transshipment cost. We develop an approximation method to compute
IIE Transactions, 2007
... Hartanto Wong, Dirk Van Oudheusden, Dirk Cattrysse TwoEchelon MultiItem Spare Parts Systems w... more ... Hartanto Wong, Dirk Van Oudheusden, Dirk Cattrysse TwoEchelon MultiItem Spare Parts Systems with Emergency Supply Flexibility and Waiting Time Constraints L/06/0010 CARDIFF BUSINESS SCHOOL WORKING PAPER SERIES ...
European Journal of Operational Research, 2006
This paper deals with the analysis of a multi-item, continuous review model of two-location inven... more This paper deals with the analysis of a multi-item, continuous review model of two-location inventory systems for repairable spare parts in which lateral and emergency shipments occur in response to stockouts. A continuous review basestock policy is assumed for the inventory control of the spare parts. The objective is to minimize the total costs for inventory holding, lateral transshipments and emergency shipments subject to a target level for the average waiting time at each of the two locations. A solution procedure based on Lagrangian relaxation is developed to obtain both a lower bound and an upper bound of the optimal total costs. The upper bound follows from a heuristic solution. An extensive numerical experiment shows an average gap of only 0.77% between the best obtained lower and upper bounds. It also gives insights into the relative improvement achieved when moving from a no-pooling policy to a pooling policy and when moving from an item approach to a system approach. We also applied the model to actual data from an air carrier company.
European Journal of Operational Research, 2005
In this paper, we develop an analytical model to estimate several performance measures in a singl... more In this paper, we develop an analytical model to estimate several performance measures in a single-item, multi-company, repairable inventory system where complete pooling of stock is permitted among the companies. Compared to previous research, this paper is different in that both non-zero lateral transshipment time and delayed lateral transshipments are considered in the model. We model the system as a
European Journal of Operational Research, 2003
This paper presents a new local search algorithm for the capacitated arc routing problem (CARP). ... more This paper presents a new local search algorithm for the capacitated arc routing problem (CARP). The procedure uses single vehicle moves and moves that operate on two routes, both derived from a node routing context but properly adapted to work well for arc routing ...
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Papers by D. Van Oudheusden