Stochastic human fatigue modeling in production systems

The performance of human resources is affected by various factors such as mental and physical fatigue, skill, and available time in the production systems. Generally, these mentioned factors have effects on human reliability and consequently change the reliability of production systems. Fatigue is a stochastic factor that changes according to other factors such as environmental conditions, work type, and work duration. Many models have been proposed to quantify fatigue in order to control its effect on reliability, but most of them considered the fatigue as a deterministic variable, while this factor is uncertain. In this paper, we propose a stochastic model for human fatigue with the aim of increasing the reliability. Considering the fatigue uncertainty, we use Chance Constraint (CC), and some methods are used to convert the model into the deterministic one. In the proposed model we consider the reliability of machines and the fatigue of human as two important factors in the production systems' reliability. The proposed model has been applied to a real case and the provided results show that production system reliability can be calculated more effectively using the proposed model.