Incorporating learning and fatigue effects in flowshop scheduling: a case study

Modern manufacturing systems promote a human-centred approach that emphasises the integral role of humans in the manufacturing process. Human operations, however, can be influenced by phenomena such as learning and fatigue. Within the framework of the flowshop scheduling problem, a bi-objective approach is developed to simultaneously minimise both makespan and total fatigue dose. This modular strategy follows a human-centric design by integrating the learning process as a variable in scheduling problems and incorporating the operator's fatigue. An experimental protocol is proposed to collect and estimate the learning rates of picking workers, as well as to mathematically model the learning effect. In addition, a methodology for collecting and analyzing data on muscular fatigue is outlined, allowing estimation of fatigue rate parameters. The findings of this study contribute to multiple fields. The study introduces an innovative method to define and incorporate the effects of learning and fatigue in the problem studied. It also affords managerial insights into the effective management of break policies, particularly in picking line operations, which have been poorly explored in the literature. Future research perspectives to extend this approach to other contexts are also suggested.