liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Models and solution methods for large-scale industrial mixed integer programming problems
Linköping University, Department of Mathematics, Optimization . Linköping University, The Institute of Technology.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with large-scale industrial problems that can be formulated using mixed integer linear programming (MIP) models. Because of the large problem size, it is not often possible to apply standard solution methods. Therefore special techniques must be used. In this thesis, both full optimization and optimization based heuristic approaches are developed.

The body of this thesis consists of five research papers. In the papers we consider industrial cases based on three applications: production planning at Södra Cell AB, ship routing and distribution at Södra Cell AB, and staff routing and scheduling in the Swedish home care.

We develop two large-scale MIP models for the production-planning problem. For solving, we use both a direct approach, and a combination of column generation and constraint branching. The latter is a technique to control the branching rules in a branch and bound framework and takes into account application specific properties.

For the ship routing problem, we present a MIP model and develop two solution methods. The first is based on an iterative rolling time horizon. In each step a part of the model is solved and later fixed. This is repeated until the full problem is solved. The second approach is to combine a genetic algorithm and linear programming. From the MIP model, we obtain solution bounds rarely present in genetic algorithm frameworks.

In the staff routing problem there are special synchronization constraints and we introduce a new MIP model. An exact solution approach based on column generation and branch and bound is developed. We also suggest a variable fixing heuristic, which we use for solving the more general problem with requirements on equal workload.

In the computational experiments, we use data instances obtained from real-world cases, and generated instances based on real-world cases. The numerical results show that high quality solutions can be obtained within reasonable time limits in all applications.

Place, publisher, year, edition, pages
Matematiska institutionen , 2007.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1071
Keyword [en]
Mathematic, linear programming (MIP), production-planning
National Category
Mathematics
Identifiers
URN: urn:nbn:se:liu:diva-11454ISBN: 978-91-85715-89-3 (print)OAI: oai:DiVA.org:liu-11454DiVA: diva2:17885
Public defence
2007-02-16, Glashuset, Hus B, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2009-04-24
List of papers
1. Combined vehicle routing and scheduling with temporal precedence and synchronization constraints
Open this publication in new window or tab >>Combined vehicle routing and scheduling with temporal precedence and synchronization constraints
2006 (English)In: EconPapers, Vol. 18Article in journal (Other academic) Published
Abstract [en]

We present a mathematical programming model for the combined vehicle routing and scheduling problem with time windows and additional temporal constraints. The temporal constraints allow for imposing pairwise synchronization and pairwise temporal precedence between customer visits, independently of the vehicles. We describe some real world problems where the temporal constraints, in the literature, usually are remarkably simplified in the solution process, even though these constraints may significantly improve the solution quality and/or usability. We also propose an optimization based heuristic to solve real size instances. The results of numerical experiments substantiate the importance of the temporal constraints in the solution approach. We also make a computational study by comparing a direct usage of a commercial solver against the proposed heuristic where the latter approach can find high quality solutions within distinct time limits.

Keyword
Routing; Scheduling; Temporal Constraints; Synchronization; Branch and Bound
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13128 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2009-02-17
2. A branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints
Open this publication in new window or tab >>A branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints
2007 (English)In: Social Science Research Network, Vol. 7Article in journal (Refereed) Published
Abstract [en]

In this paper we present a branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints. The synchronization constraints are used to model situations when two or more customers need simultaneous service. The synchronization constraints impose a temporal dependency between vehicles, and it follows that a classical decomposition of the vehicle routing and scheduling problem is not directly applicable. With our algorithm, we have solved 44 problems to optimality from the 60 problems used for numerical experiments. The algorithm performs time window branching, and the number of subproblem calls is kept low by adjustment of the columns service times.

Keyword
Routing, Scheduling, Synchronization, Branch and Price
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-13129 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2009-04-15
3. Supply chain optimization in the pulp mill industry: IP models, column generation and novel constraint branches
Open this publication in new window or tab >>Supply chain optimization in the pulp mill industry: IP models, column generation and novel constraint branches
Show others...
2004 (English)In: European Journal of Operational Research, ISSN 0377-2217, Vol. 156, no 1, 2-22 p.Article in journal (Refereed) Published
Abstract [en]

We study the supply chain problem of a large international pulp producer with five pulp mills located in Scandinavia. The company currently uses manual planning for most of its supply chain, which includes harvesting and transportation of pulp, production scheduling and distribution of products to customers. We have developed two new mixed integer models that determine daily supply chain decisions over a planning horizon of three months. One model is based on column generation, where the generation phase is to find new production plans using a shortest path network. The second, slightly less flexible, has the daily production decisions explicitly included in the model. In order to solve the models within practical time limits we use a flexible approach that aggregates together the less immediate decisions. We also introduce a novel constraint branching heuristic. The models and solution approaches are intended to become an integrated component in the company’s new management system. In tests and comparisons with today’s manual planning, we have found new strategic policies that significantly reduce the company’s supply chain costs.

Keyword
Branch and bound, Integer programming, Production, Scheduling, Supply chain management
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-13130 (URN)10.1016/j.ejor.2003.08.001 (DOI)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2013-11-05
4. Supply chain optimization in pulp distribution using a rolling horizon solution approach
Open this publication in new window or tab >>Supply chain optimization in pulp distribution using a rolling horizon solution approach
2006 (English)Report (Other academic)
Abstract [en]

In this paper we consider a combined supply chain and ship routing problem for a large pulp producer in Scandinavia. The problem concerns the distribution of pulp to customers, with route scheduling of ships as a central part of modeling. It is an operative planning problem with daily ship routing decisions over a 40 days period. The pulp supply is determined by fixed production plans, and the transport flows and storages are modeled with the requirement to satisfy the demand in a cost-optimal way. We develop a mixed integer programming model with binary variables for route usage of a vessel.

The problem is solved with a heuristic solution method, based on a rolling time horizon and a standard branch and bound algorithm. We apply the heuristic on problem instances with real world data, and compare results from reduced problem instances with the results from an exact branch and bound search. The computational experiments indicate that real world problems are solvable with the solution method and that it in many cases can be very effcient.

 

Series
LiTH-MAT-R, 2003-25
Keyword
Supply chain, Ships, Scheduling, Mixed integer programming
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-13131 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2013-11-05
5. A hybrid algorithm for a pulp distribution problem
Open this publication in new window or tab >>A hybrid algorithm for a pulp distribution problem
2005 (English)In: IEEE Intelligent Systems, ISSN 1541-1672, Vol. 20, no 4, 19-25 p.Article in journal (Refereed) Published
Abstract [en]

Distribution is a major factor in the supply chain for Sodra Cell, a leading manufacturer of pulp intended for paper production. Each year, the company transports large quantities of pulp using ships, trains, and trucks; here we focus on scheduling the ships and optimizing deliveries to minimize distribution costs.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13132 (URN)10.1109/MIS.2005.59 (DOI)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2015-12-29

Open Access in DiVA

No full text

Authority records BETA

Bredström, David

Search in DiVA

By author/editor
Bredström, David
By organisation
Optimization The Institute of Technology
Mathematics

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1666 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf