Assembly Line Worker Assignment And Balancing Problem Research Articles

Developments in the Literature and New Study Recommendations Within the Scope of the Assembly Line Worker Assignment and Balancing Problem (ALWABP)

In this study, by defining the Assembly Line Worker Assignment and Balancing Problem (ALWABP), the point that has been reached to this day is researched on ALWABP. The studies in question are evaluated comprehensively in terms of their objective functions, established decision models, additional constraints that are being considered, the solution method that is applied, the size of the problem, the data that were used in the research, the type of assembly line that was used in the research, and the product model variety. For this purpose, a total of 41 articles, which are presented on the Web of Science (WoS), Scopus, and Google Scholar databases, are reviewed from the time that this problem first appeared in 2007, up to 2022. Keywords that are used while researching the mentioned databases are “Assembly Line Worker Assignment and Balancing Problem (ALWABP)”, “Assembly Line Balancing Problem (ALBP)”, and “Worker Assignment Problem (WAP)”. Based on the articles examined in the study, the developments in the literature concerning the subject of ALWABP have been discussed, and the required study themes in this area have been determined. Since the research performed is a study that has not taken any place in the literature to this day, it is considered that it can shed light on the research that might be needed in the future in the ALWABP area.

Developments in the Literature and New Study Recommendations Within the Scope of the Assembly Line Worker Assignment and Balancing Problem (ALWABP)

In this study, by defining the Assembly Line Worker Assignment and Balancing Problem (ALWABP), the point that has been reached to this day is researched on ALWABP. The studies in question are evaluated comprehensively in terms of their objective functions, established decision models, additional constraints that are being considered, the solution method that is applied, the size of the problem, the data that were used in the research, the type of assembly line that was used in the research, and the product model variety. For this purpose, a total of 41 articles, which are presented on the Web of Science (WoS), Scopus, and Google Scholar databases, are reviewed from the time that this problem first appeared in 2007, up to 2022. Keywords that are used while researching the mentioned databases are “Assembly Line Worker Assignment and Balancing Problem (ALWABP)”, “Assembly Line Balancing Problem (ALBP)”, and “Worker Assignment Problem (WAP)”. Based on the articles examined in the study, the developments in the literature concerning the subject of ALWABP have been discussed, and the required study themes in this area have been determined. Since the research performed is a study that has not taken any place in the literature to this day, it is considered that it can shed light on the research that might be needed in the future in the ALWABP area.

Risk-averse assembly line worker assignment and balancing problem with limited temporary workers and moving workers

Assembly line worker assignment and balancing problem (ALWABP) is an important research topic originated from sheltered work centres for disabled, in which workforce is assumed to be heterogeneous due to their disabilities. Since the employment of disabled workers may sustain higher absenteeism rates due to their health, especially under COVID-19, employing temporary workers to fill labour shortage is a crucial issue. In addition, in practice, the movement of workers between stations on assemble lines can increase the flexibility of worker assignment. In this study, we investigate a new risk-averse ALWABP with uncertain disabled worker availability, limited temporary workers and moving workers. The objective is to minimise the risk-averse weighted sum of the cycle time and the number of employed temporary workers. For the problem, a risk-averse two-stage stochastic programming model is formulated. The first stage assigns specific tasks (called fixed tasks) to stations, while the second stage assigns workers and remaining tasks (called flexible tasks) to stations. A genetic algorithm combining K-means clustering approach and variable neighbourhood search (GAKV) is designed. Experiment results show the superiority of the GAKV in terms of solution quality and computation time compared with sample average approximation (SAA). In addition, managerial insights are drawn.

Modeling and solving assembly line worker assignment and balancing problem with sequence-dependent setup times

Assembly lines appear with various differentiations in order to better include the disabled in the labor market and to increase production efficiency. In this way, the optimal workforce assignment problem that emerges heterogeneously is called assembly line worker assignment and balancing problem (ALWABP). This paper addresses the ALWABP where the simple version is enriched by considering sequence-dependent setup times between tasks. A mixed integer linear programming model is presented, and a simulated annealing algorithm is developed such as an NP-hard problem. In order to test the proposed solutions, 640 benchmark problems in the literature were combined and used. The solutions obtained through using the proposed algorithm are compared with the mixed integer programming model on the small-size test problems. Experimental results show that the proposed algorithm is more effective and robust for a large set of benchmark problems.

The Fuzzy Assembly Line Worker Assignment and Balancing Problem

Consideration is given to the assembly line worker assignment and balancing problem (ALWABP) with uncertain task processing times and objective to simultaneously minimize the fuzzy cycle time and the fuzzy smoothness index of the line. After positioning the problem within the relevant research field, we present a genetic algorithm (GA) for its solution. Results over selected benchmarks test problems show the effectiveness of the proposed GA. The results obtained are further supported by a sensitivity analysis that shows the effect of the vagueness (uncertainty) of the task processing times on the uncertainty of the examined optimization criteria.

A New Mathematical Model for Assembly Line Worker Assignment and Balancing

Aim of assembly line balancing is to assign the product parts to the workstations that constitute the assembly line. Worker assignment problem is a new problem variety in assembly lines that typically is met in different situations in which the workforce is not homogeneous. This problem is different from the well-known simple assembly line balancing problem from the view point of task execution times of nonhomogeneous workers. In this paper, we introduce a new mathematical formulation with objective function to minimize the cycle time for the assembly line worker assignment and balancing problem (ALWABP). GUROBI solver is used for the problem solution. The mathematical model is examined by using a standard test problem set. As a result of the experiments, it is observed that the proposed mathematical model is more effective in terms of solution quality and CPU time than the current mathematical method.

Model and migrating birds optimization algorithm for two-sided assembly line worker assignment and balancing problem

Worker assignment is a relatively new problem in assembly lines that typically is encountered in situations in which the workforce is heterogeneous. The optimal assignment of a heterogeneous workforce is known as the assembly line worker assignment and balancing problem (ALWABP). This problem is different from the well-known simple assembly line balancing problem concerning the task execution times, and it varies according to the assigned worker. Minimal work has been reported in worker assignment in two-sided assembly lines. This research studies worker assignment and line balancing in two-sided assembly lines with an objective of minimizing the cycle time (TALWABP). A mixed-integer programming model is developed, and CPLEX solver is used to solve the small-size problems. An improved migrating birds optimization algorithm is employed to deal with the large-size problems due to the NP-hard nature of the problem. The proposed algorithm utilizes a restart mechanism to avoid being trapped in the local optima. The solutions obtained using the proposed algorithms are compared with well-known metaheuristic algorithms such as artificial bee colony and simulated annealing. Comparative study and statistical analysis indicate that the proposed algorithm can achieve the optimal solutions for small-size problems, and it shows superior performance over benchmark algorithms for large-size problems.

The robust (minmax regret) assembly line worker assignment and balancing problem

Line balancing aims to assign the assembly tasks to the stations that compose the assembly line. A recent body of literature has been devoted to heterogeneity in the assembly process introduced by different workers. In such an environment, task times depend on the worker performing the operation and the problem aims at assigning tasks and workers to stations in order to maximize the throughput of the line. In this work, we consider an interval data version of the assembly line worker assignment and balancing problem (ALWABP) in which it is assumed that lower and upper bounds for the task times are known, and the objective is to find an assignment of tasks and workers to the workstations such that the absolute maximum regret among all of the possible scenarios is minimized. The relationship with other interval data minmax regret (IDMR) problems is investigated, the inapplicability of previous approximation methods is studied, regret evaluation is considered, and exact and heuristic solution methods are proposed and analyzed. The results of the proposed methods are compared in a computational experiment, showing the applicability of the method and the theoretical results to solve the problem under study. Additionally, these results are not only applicable to the problem in hand, but also to a more general class of problems.

A multiple-rule based constructive randomized search algorithm for solving assembly line worker assignment and balancing problem

This paper proposes a constructive heuristic approach for the assembly line worker assignment and balancing problem (ALWABP). ALWABP arises when the operation time for every task differs according to the worker who executes the task. Since the operation times of tasks vary due to the workers, the problem requires a simultaneous solution to the double assignment problem. Tasks must be assigned to workers and workers to stations, concurrently. This problem is especially proposed in sheltered work centers for the disabled. However, it is not only important for the assembly lines with the disabled, but also for manually operated assembly lines with high labor turnover. In this paper, a multiple-rule based constructive randomized search (MRBCRS) algorithm is proposed in order to solve the ALWABP. Thirty nine task priority rules and four worker priority rules are defined. Performance of the proposed MRBCRS is compared with the relevant literature on benchmark data. Experimental results show that the proposed MRBCRS is very effective for benchmark problems. The results show that the algorithm improves upon the best-performing methods from the literature in terms of solution quality and time.

ErgoALWABP: a multiple-rule based constructive randomized search algorithm for solving assembly line worker assignment and balancing problem under ergonomic risk factors

This paper proposes a new type of assembly line worker assignment and balancing problem (ALWABP) which considers ergonomic risks. ALWABP occurs when task times vary according to the assigned worker. Although the operation time of a task is assumed to be fixed in classical assembly lines, it depends on the operator who executes the task in ALWABP. In ALWABP literature, the primary and secondary objectives are minimizing cycle time and balancing workload among workstations smoothly, respectively. When smoothing workload, only task times are taken into consideration in the relevant literature. However, degree of difficulty of tasks is also very important. Two workers executing two different stations with the same station time are assumed to be equally loaded according to the traditional perception. In fact, even they have the same station time; their workloads are different because of the different tasks they execute, in real life assembly line configurations. In order to close this gap between the real life and the literature, this study introduces an ALWABP problem with considering ergonomic risk factors (ErgoALWABP). Due to the complex nature of the problem, optimum seeking methods are not capable of solving it. So, the proposed problem is tackled with the multiple-rule based constructive randomized search approach. Also, OCcupational Repetitive Action method is used for making ergonomic risk assessment. Performance of the proposed solution procedure is compared with the relevant literature on benchmark data. Experimental results show that ergonomic environment could be improved when ergonomic risk factors are taken into account.

A population-based algorithm for the bi-objective assembly line worker assignment and balancing problem

A multi-objective evolutionary algorithm (MOEA) is presented for the solution of the bi-criteria assembly line worker assignment and balancing problem (ALWABP). This problem consists of determining the best assignment of the assembly tasks to workers as well as the workers to workstations in accordance with some desired objectives. Task times differ depending on worker skills. Two optimization criteria are considered to be minimized, the cycle time and the smoothness index of the workload of the line. The efficiency of the proposed MOEA is evaluated over a set of benchmarks test problems taken from the open literature. A suitable performance analysis is deployed concerning the quality of the Pareto solutions. The results demonstrate a very satisfactory performance in terms of solution quality.

The assembly line worker assignment and balancing problem with stochastic worker availability

Assembly lines can be employed successfully in sheltered work centres to better include persons with disabilities in the labour market as well as to improve production efficiency. The optimal assignment of a heterogeneous workforce is known as the assembly line worker assignment and balancing problem (ALWABP). These assembly lines are characterised not only by a heterogeneous workforce, but also by high levels of absenteeism, which makes it more difficult to obtain stable and efficient line balancing solutions. In this paper, an extension of the ALWABP to minimise the expected cycle time under uncertain worker availability is proposed. We model this problem as a two-stage mixed integer program, and propose local search heuristics for solving it. Computational experiments show that stochastic modelling can help to improve the line’s efficiency and that the proposed heuristics produce good results for instances of practical size.

A heuristic and a branch-and-bound algorithm for the Assembly Line Worker Assignment and Balancing Problem

In traditional assembly lines, it is reasonable to assume that task execution times are the same for each worker. However, in Sheltered Work Centres for Disabled this assumption is not valid: some workers may execute some tasks considerably slower or even be incapable of executing them. Worker heterogeneity leads to a problem called the Assembly Line Worker Assignment and Balancing Problem (ALWABP). For a fixed number of workers the problem is to maximize the production rate of an assembly line by assigning workers to stations and tasks to workers, while satisfying precedence constraints between the tasks.This paper introduces new heuristic and exact methods to solve this problem. We present a new MIP model, propose a novel heuristic algorithm based on beam search, as well as a task-oriented branch-and-bound procedure which uses new reduction rules and lower bounds for solving the problem. Extensive computational tests on a large set of instances show that these methods are effective and improve over existing ones.

Two extensions for the ALWABP: Parallel stations and collaborative approach

In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balancing Problem (ALWABP) that allow parallelization of and collaboration between heterogeneous workers. These new approaches suppose an additional level of complexity in the Line Design and Assignment process, but also higher flexibility; which may be particularly useful in practical situations where the aim is to progressively integrate slow or limited workers in conventional assembly lines. We present linear models and heuristic procedures for these two new problems. Computational results show the efficiency of the proposed approaches and the efficacy of the studied layouts in different situations.

On solving the assembly line worker assignment and balancing problem via beam search

Certain types of manufacturing processes can be modelled by assembly line balancing problems. In this work we deal with a specific assembly line balancing problem that is known as the assembly line worker assignment and balancing problem (ALWABP). This problem appears in settings where tasks must be assigned to workers, and workers to work stations. Task processing times are worker specific, and workers might even be incompatible with certain tasks. The ALWABP was introduced to model assembly lines typical for sheltered work centers for the Disabled. In this paper we introduce an algorithm based on beam search for solving the ALWABP with the objective of minimizing the cycle time when given a fixed number of work stations, respectively, workers. This problem version is denoted as ALWABP-2. The experimental results show that our algorithm is currently a state-of-the-art method for the ALWABP-2. In comparison to results from the literature, our algorithm obtains better or equal results in all cases. Moreover, the algorithm is very robust for what concerns the application to problem instances of different characteristics.

Branch and bound procedures for solving the Assembly Line Worker Assignment and Balancing Problem: Application to Sheltered Work centres for Disabled

In this paper a new problem called Assembly Line Worker Assignment and Balancing Problem (ALWABP) is introduced. This problem arises in those assembly lines where we have certain limited resources available (normally workers) in which the operation time for every task is different depending on who executes the task, and where there are also some task–worker incompatibilities defined. The problem consists of providing a simultaneous solution to a double assignment: (1) tasks to stations; and (2) available workers to stations. After defining the mathematical model for this problem, a basic Branch and Bound approach with three possible search strategies and different parameters is presented. We also propose the use of a Branch and Bound-based heuristic for large problems and analyse the behaviour of both exact and heuristic methods through experimental studies. Finally the implementation of these procedures in a Sheltered Work centre for Disabled—the real environment which has inspired this research—is described. In these centres the adoption of assembly lines provide many advantages, since the traditional division of work in single tasks may become a perfect tool for making certain worker disabilities invisible. Efficiently applying this configuration helps these centres to achieve their primary aim: growth in order to provide more jobs for more disabled people, but always considering the specific limitations that the disabled workers have. In this sense this paper shows one of the possible real applications where Operations Research can help not only to get economic and productive benefits but also certain social aims.