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Semi‐Markov reliability model of manufacturing systems considering machine degradation, human errors, and their mutual facilitation effects

Reliability plays a significant role in the overall performance of manufacturing systems, and accurate reliability assessments can guarantee their functionalities and efficiencies. This paper develops a reliability model of a manufacturing system considering machine degradation, human errors, and their mutual facilitation effects (MFE): machine degradation may increase fatigue rate and weaken learning process, thereby facilitating the occurrence of human errors, while human errors may, in turn, facilitate the machine degradation process. Although MFE may reduce system reliability, current reliability models ignore this effect. In this paper, to describe the MFE, a stochastic human error model under the effects of learning–forgetting and fatigue–recovery is proposed, where the human error rate depends on the current machine degradation state; next, based on their facilitation effects on machine degradation, human errors are divided into safety, damage, and fatal zones; finally, we incorporate the zoned human error model into the machine degradation model and develop a Semi‐Markov reliability model. A Monte Carlo method is implemented to calculate system reliability. The turret of a lathe operated by a worker is utilized to illustrate the effectiveness of the reliability model.