Article
Engineering, Industrial
Ge Guo, Sarah M. Ryan
Summary: This paper tackles the uncertainty factors in sequencing decisions in mixed-model assembly lines by modeling unreliable part delivery and quality. It utilizes stochastic optimization to find sequencing policies that can improve on-time performance, and also introduces a risk-averse program to protect against worst-case scenarios chosen by decision makers. Computational studies demonstrate the high quality of resulting sequencing decisions and the time efficiency of the solution method using Progressive Hedging.
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
(2022)
Article
Computer Science, Artificial Intelligence
Lixin Cheng, Qiuhua Tang, Shengli Liu, Liping Zhang
Summary: This paper presents a mathematical model and an augmented simulated annealing algorithm for the mixed-model assembly job-shop scheduling problem with batch transfer. By incorporating production sequencing knowledge and batch transfer knowledge, designing problem-specific neighborhood structures, and implementing a restart mechanism, the proposed algorithm outperforms other comparison algorithms in solving the problem.
KNOWLEDGE-BASED SYSTEMS
(2023)
Review
Engineering, Manufacturing
Maximilian Johannes Schlueter, Frederik Ferid Ostermeier
Summary: Dynamic line balancing is a promising approach to achieve both equal loads for operators and high throughput for manufacturers. Tasks can be shared between adjacent stations in addition to the fixed allocated tasks.
CIRP JOURNAL OF MANUFACTURING SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Industrial
Yunfang Peng, Lijun Zhang, Beixin Xia, Yajuan Han
Summary: In this study, the balancing and sequencing problems of flexible mixed model assembly lines with alternative precedence relations are addressed. Instead of using precedence graphs, If-then rules and AND/OR graphs are chosen as modeling tools due to their ability to represent alternative precedence relations. Mixed integer linear programming (MILP) and constraint programming (CP) models are developed, and an iterative decomposition method is proposed for dealing with large-sized problems. The computational experiments show that CP outperforms MILP, especially when there are more OR relations. Additionally, the iterative decomposition method achieves better solution quality and time efficiency than MILP and CP.
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
(2023)
Article
Engineering, Manufacturing
Arnd Huchzermeier, Tobias Moench
Summary: Industry trends such as product customization, radical innovation, and local production are driving the adoption of mixed-model assembly lines (MMALs) to handle the increasing gap between model processing times and true build to order capability. The existing deviations in work content on these assembly lines pose challenges for production planning, particularly in assembly line sequencing. This study proposes an ideal variable rate launching (VRL) case that achieves 100% productivity by minimizing idle time and utility work, and demonstrates the benefits of open stations and variable takt in reducing labor costs and total line length.
PRODUCTION AND OPERATIONS MANAGEMENT
(2023)
Article
Engineering, Electrical & Electronic
Qidong Yin, Xiaochuan Luo, Julien Hohenstein
Summary: The automotive industry is facing challenges of integrating new energy vehicles into existing assembly systems. The BMW assembly shop implemented a practical approach using specific workforce for NEV assembly, studying the design of assembly system under this new production pattern to minimize production costs and enhance system flexibility. Developed algorithm showed effectiveness in quickly generating reconfiguration solutions for various model mix scenarios and production rates.
Article
Engineering, Industrial
Thiago Cantos Lopes, Adalberto Sato Michels, Nadia Brauner, Leandro Magatao
Summary: This paper focuses on optimizing Mixed-model assembly lines with continuous paced line control and proposes a criterion-space method for defining the Pareto front. Comparing the Pareto fronts between cycle time and line length for paced and unpaced lines allows meaningful comparisons between line controls. An industrial case study suggests that paced lines are more efficient than unpaced lines for lower cycle time ranges.
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
(2023)
Article
Engineering, Industrial
Lixin Cheng, Qiuhua Tang, Liping Zhang
Summary: This paper investigates the mixed-model assembly job-shop scheduling problem with lot streaming and proposes a mathematical model and an adaptive simulated annealing algorithm to solve the problem. Experimental results show that the algorithm performs well.
JOURNAL OF MANUFACTURING SYSTEMS
(2023)
Article
Computer Science, Interdisciplinary Applications
Stefan Bock, Nils Boysen
Summary: This study focuses on real-time launch control in mixed-model assembly lines, proposing an integrated solution and demonstrating its superiority over alternative launching approaches in a simulation study. The integrated approach not only improves production efficiency but also reduces safety stocks of parts within workstations.
COMPUTERS & OPERATIONS RESEARCH
(2021)
Article
Engineering, Industrial
Serena Finco, Martina Calzavara, Fabio Sgarbossa, Ilenia Zennaro
Summary: This paper proposes a new methodological approach to include physical fatigue and rest allowance as ergonomic parameters in mixed-model assembly lines, aiming to improve productivity and human safety. By developing a linear mathematical model and heuristic approach, it effectively addresses the balancing and sequencing decision problems in assembly lines.
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
(2021)
Article
Engineering, Industrial
Thorben Krueger, Achim Koberstein, Norbert Bittner
Summary: This paper proposes a new linear programming-based approach for the master production scheduling of mixed-model assembly lines, which considers technical car sequencing rules in a higher level of detail. The interdependencies of car sequencing rules, often neglected in practice and research, are investigated and found to induce additional implicit constraints. A numerical study shows that the proposed approach significantly reduces sequencing violations compared to existing methods.
FLEXIBLE SERVICES AND MANUFACTURING JOURNAL
(2022)
Article
Computer Science, Interdisciplinary Applications
Binghai Zhou, Zhe Zhao
Summary: This study focuses on the dynamic part feeding scheduling problem under a Kanban system in mixed-model assembly lines in the automobile industry. A hybrid fuzzy-neural-based dynamic scheduling method is proposed to optimize productivity and part feeding costs simultaneously. Computational experiments demonstrate the superiority of the method in dynamic manufacturing environments.
COMPUTERS & INDUSTRIAL ENGINEERING
(2022)
Article
Engineering, Industrial
Tadeusz Sawik
Summary: In this paper, a new mixed integer programming (MIP) formulation is proposed for balancing and scheduling of mixed model assembly lines with disjunctive precedence constraints among assembly tasks. The alternative precedence relations are represented by AND/OR assembly graph. Unlike other MIP approaches, the new model introduces a new disjunctive precedence selection and task assignment variable to optimally choose one relation for each subset of alternative precedence relations. The computational examples demonstrate the superior performance of the new modelling approach.
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
(2023)
Article
Computer Science, Interdisciplinary Applications
Wei Zhang, Liang Hou, Roger J. Jiao
Summary: This paper introduces a method for balancing and sequencing in paced assembly lines planning based on dynamic takt time, and evaluates the effectiveness of the improved artificial bee colony algorithm. Analysis of case studies of different scales verifies the rationality of the dynamic takt time method.
COMPUTERS & INDUSTRIAL ENGINEERING
(2021)
Article
Engineering, Multidisciplinary
F. Tanhaie, M. Rabbani, N. Manavizadeh
Summary: This study investigates the use of mixed-model assembly line (MMAL) technology to address make-to-order (MTO) challenges, achieving superior performance through a multi-objective particle swarm optimization (MOPSO) algorithm.
ENGINEERING OPTIMIZATION
(2021)
Article
Management
Kai Wang, Erwin Pesch, Dominik Kress, Ilia Fridman, Nils Boysen
Summary: This paper discusses the Piggyback Transportation Problem, where large vehicles transport small vehicles to designated locations. Through theoretical analysis and computational complexity investigation, the study examines solutions to the Piggyback Transportation Problem and the impact of cost drivers on service quality.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2022)
Article
Management
Johannes Rupp, Nils Boysen, Dirk Briskorn
Summary: Hubs play a crucial role in modern distribution networks, enabling transportation efficiency and cost savings. This study focuses on optimizing vehicle consolidation in hub processes and proposes suitable solutions. The problem addressed is not only relevant to the air hub of DHL and other logistics companies, but also applicable to other types of hubs.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2022)
Article
Management
Stefan Schwerdfeger, Stefan Bock, Nils Boysen, Dirk Briskorn
Summary: This paper presents a detailed modeling approach based on continuous variables to minimize installation costs for electrified highway kilometers while still providing sufficient energy for a given set of representative electric vehicle tours. The study applies this approach to demonstrate that investment costs can be considerably reduced along a European highway mainline while still enabling electrified transport between most adjacent major cities.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2022)
Article
Engineering, Manufacturing
Dirk Briskorn, Konrad Stephan, Nils Boysen
Summary: The study investigates the single machine scheduling problem arising from products with modular design, where product characteristics are achieved through separate components that can be freely combined, and setup between consecutive products depends on the similarities of product characteristics. Some special cases are found to be solvable in polynomial time, while most cases remain strongly NP-hard.
JOURNAL OF SCHEDULING
(2022)
Article
Management
Joachim Scholl, Nils Boysen, Armin Scholl
Summary: Recent technological developments enable the connection of vehicles through digital data transmission, allowing for safe platooning of trucks. This platooning reduces fuel consumption and carbon footprint in road-based freight transportation. Electric trucks, which need to charge their batteries, are particularly suitable for platooning as it reduces energy consumption and increases driving range. This paper presents optimization approaches for scheduling the platoon formation process of electric commercial vehicles, aiming to minimize total energy costs.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2023)
Review
Management
Nils Boysen, Stefan Schwerdfeger, Konrad Stephan
Summary: This paper explores the synchronization problems that arise in warehouses that have evolved into fully-automated fulfillment factories due to the success of e-commerce. By optimizing workstation setups and implementing synchronization operations, the picking efficiency can be improved and the burden on the bin supply system can be reduced. The findings demonstrate that the right workstation setup significantly enhances throughput performance.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2023)
Article
Computer Science, Interdisciplinary Applications
Nils Boysen, Dirk Briskorn, Johannes Rupp
Summary: More and more people are living in urban areas, particularly in megacities. To reduce the negative effects of surface traffic on health, congestion, environment, and safety, a cargo tunnel is proposed as an innovative solution for delivering goods to urban inhabitants. The concept involves autonomous rail-bound or maglev vehicles delivering goods underground to small inner-city hubs, from where environmentally-friendly vehicles can complete the final leg of delivery. However, there are operational challenges in synchronizing goods arrivals at the inner-city hubs with delivery tours. An optimization problem is formulated to address this issue and explore the impact of tunnel throughput, storage capacity at the hub, and vehicle capacity on delivery performance. A benchmark test shows that while a cargo tunnel reduces carbon dioxide emissions, it can lead to excessive cargo bike traffic in large urban regions.
COMPUTERS & OPERATIONS RESEARCH
(2023)
Article
Operations Research & Management Science
Maximilian Loeffler, Nils Boysen, Michael Schneider
Summary: In the e-commerce era, efficient order fulfillment processes in distribution centers have become crucial. This paper presents a heuristic method for coordinating multiple autonomous mobile robots (AMRs) and pickers to minimize the makespan. The study shows significantly improved efficiency with the use of robot-assisted order picking.
TRANSPORTATION SCIENCE
(2023)
Article
Management
Nils Boysen, Stefan Schwerdfeger, Marlin W. Ulmer
Summary: To meet the expectations of demanding customers, there is a trend toward warehouse automation, especially in large e-commerce distribution centers. This paper focuses on robotized sorting systems, where autonomous mobile robots are used to automatically sort products. The paper proposes a sophisticated optimization approach that improves the sortation throughput in real-time conditions, even with limited knowledge of the approaching products.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2023)
Article
Operations Research & Management Science
Nils Boysen, Dirk Briskorn, David Fuessler, Konrad Stephan
Summary: Due to high real estate costs, shop floor space is limited in brick-and-mortar stores. Retail chains now aim for store-friendly shipments by mirroring store layouts. A pocket sorter is used in distribution centers to assemble separate bags for each item, resulting in efficient delivery to workstations. Simple decision rules can solve the notorious complexity of the problem and dramatically reduce completion times of store orders.
NAVAL RESEARCH LOGISTICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Stefan Bock, Nils Boysen
Summary: Many online retailers use scattered storage in their picking areas, which increases the likelihood of products being located in close proximity, making picking more efficient. However, replenishment workers face additional effort due to the need to travel along multiple shelves for restocking. The special parallel-aisle structure in warehouses allows for an exact solution algorithm with pseudo-polynomial runtime, resulting in significant performance gains for an optimized stowing process.
INFORMS JOURNAL ON COMPUTING
(2023)
Article
Operations Research & Management Science
Nils Boysen, Dirk Briskorn, Rea Roentgen, Michael Dienstknecht
Summary: This study addresses the key issue of demand imbalance in free-floating carsharing and proposes an optimization-based matching method that considers both current and future demand. By reducing the deviations between actual car supply and target levels, this approach aims to alleviate the problem. The study presents polynomial-time algorithms for the matching task and demonstrates its advantage through computational experiments. However, the concept fails in a real-world dataset due to the use of geographical characteristics instead of demand variation. To be successful, the matching task requires a properly partitioned service district and reliable demand forecasts.
TRANSPORTATION SCIENCE
(2023)
Article
Operations Research & Management Science
Nils Boysen, Simon Emde, Konrad Stephan
Summary: The parts-to-picker system can relieve order pickers from walking in the warehouse and improve efficiency. We study the crane scheduling problem in this system and prove its strong NP-hardness. We also find that this problem is equivalent to the traditional vehicle routing problem.
EURO JOURNAL ON TRANSPORTATION AND LOGISTICS
(2022)
Article
Engineering, Industrial
Nils Boysen, Konrad Stephan, Felix Weidinger
Summary: In order to improve picking efficiency in warehouses, strategies like order batching and zoning are commonly used. These strategies help in increasing picking density and order processing efficiency in both picking and consolidation stages.
Article
Computer Science, Interdisciplinary Applications
Maximilian Loffler, Nils Boysen, Michael Schneider
Summary: This paper investigates the routing algorithms for AGV-assisted order picking in parallel-aisle warehouses. It proposes a dynamic programming routine with polynomial runtime for fixed picking order sequences and offers a heuristic for cases where order sequencing is a decision. The use of AGVs has shown to significantly improve order-fulfillment processes in warehouses.
INFORMS JOURNAL ON COMPUTING
(2022)
