Scheduling Cellular Manufacturing Systems Based on Human Factors and Due Date of Orders

Human factors engineering is a scientific area about collaboration between persons and other parameters of a system. It consists of theorems, principles and methods for designing based on the relief of operators and system performance. The main purpose of this paper is scheduling the orders and operators in a CMS regarding the human factors to minimize the orders’ tardiness and fatigue of operators. The fatigue, recovery, learning and forgetting are the human factors in this study, which affect the job rotation and shift scheduling. A mathematical model and a rolling horizon heuristic are developed as well as three groups of test problems each including five random problem instances. The rolling horizon algorithm was tested on the test problems and the results showed that non-overlapping mode with a length of 2 periods is the best choice. The heuristic algorithm solves large-scale instances with less than 3% optimality gaps in about 5.5 minutes while the MIP model needs about 2 hours. The results of linearization of the model showed that the conversion of the continuous variables into integer numbers is more efficient than the McCormick method. Sensitivity analysis shows that fatigue factor has a direct relation with tardiness and learning and also, the learning factor has a reverse relation with the both objectives of tardiness and mean fatigue.