Applying multi objective modeling to create safe job rotation schedules based upon workers´ skills and idleness

In this paper a model is developed to deal with safe skill-based job rotation scheduling (SSJRS). A multi objective integer programming model is presented to determine job rotation schedules which considers four objective functions simultaneously. The first objective function aims to minimize maximum occupational noise exposure injuries. The second one is designed to minimize potential of worker´s low back injuries and the third objective is developed to consider worker skill level´s priorities in assignments and finally fourth objective is added to minimize workers´ idleness during planning horizon. The potential of worker low back injuries and the noise exposure levels of each job are assessed by job severity index (JSI) and daily noise dosage (DND) respectively. Thresholds for JSI and DND, is also considered in the presented model. Finally this model is solved as a single objective model, using LP-Metric method. To verify the efficiency of SSJRS, test problems are solved for each objective of the model separately and the results are compared with solutions of SSJRS model. It is found that, the results from SSJRS model, dominates the results from single objective models.