New models with ergonomic extension in assembly line worker assignment and balancing problem

The efficiency of assembly lines where workers are taken place intensively depends on the performance levels of the workers working on these lines. The performance levels of the workers are affected by the heterogeneous worker characteristics. These heterogeneous features cause workers to be affected by working environment conditions at different levels. For this reason, it is necessary to benefit from the science of ergonomics in Assembly Line Worker Assignment and Balancing Problem (ALWABP), where systematic activities are carried out to ensure harmony between human and working environment. Therefore, Ergonomic Assembly Line Worker Assignment and Balancing Problem (Ergo-ALWABP) models considered the heterogeneous characteristics of the workers and reflect the real production conditions will be established and the productivity levels of the lines will be determined more reliably. In this context throughout the theses study, six Ergo-ALWABP models have been proposed, in which different ergonomic risk factors are taken into account. In the first model, environmental risk factors such as illumination and noise factors and Inappropriate Working Postures (IWP) are included in the constraints and it is aimed to minimize the cycle time. The Rapid Entire Body Assessment (REBA) method was used to determine the risk level of working postures, depending on the duration of the postures being used. In the second model, environmental risk factors and IWP are included in the constraints and it is aimed to minimize the cycle time and maximize the ability of workers to perform their preferred task/s considering the psychological risk factor. In the third model, the probability of having an occupational accident, which is calculated by considering the different characteristics of the workers within the scope of individual risk factors, is minimized with the cycle time and with that, environmental risk factors and IWP are included in the constraints. In the fourth model, environmental risk factors and IWP are included in the constraints, and the energy expenditure amounts of the workers and cycle times are minimized. In the fifth model, environmental risk factors and IWP are included in the constraints, the cycle time is minimized and the assignment of workers to appropriate tasks according to their experience level is maximized. In the last model, an integrated ALWABP model is proposed, which includes all the ergonomic risk factors considered in the study. Since the first model developed was single-objective, it was solved by mathematical modeling. Since the second, third, fourth and fifth models are two-objective, Pareto Solutions (PSs) has been put forward. For the last model, Compromise Solution-CSs were obtained. In the solutions of the proposed mathematical models, data belonging to a real production environment with 18 tasks and 7 workers were used. In addition, performance analysis for the 24 and 28 tasks ALWABP test data which previously developed by other researchers was performed for all of the six models. As a result of the study, it was seen that the best results were achieved in reasonable times with the developed models. Accordingly, it has been evaluated that the proposed integrated model has an original and detailed structure that can contribute to the Ergo-ALWABP literature. In addition, it will be able to support decision makers as a decision mechanism in order to increase the efficiency of assembly lines, considering heterogeneous worker characteristics and ergonomic risk factors.