Environmental issue in an alternative production-maintenance control for unreliable manufacturing system subject to degradation

This article addresses the problem of joint production, maintenance, and emission control for an unreliable manufacturing system subject to degradation. The manufacturing system is composed of a production unit producing one product type. The production operations generate harmful emissions to the environment and may be sanctioned by an environmental penalty imposed by the relevant authorities under the emission cap approach. Due to degradation phenomena, the availability of the machine decreases and the emission rate increases continuously over time. This paper aims to propose a feedback strategy to simultaneously control production rate, emission rate, as well as maintenance rate in order to mitigate the effect of the degradation of the system. The objective is to minimize the total cost over an infinite horizon. In this article, three different control policies from the class of hedging point (HPP1, HPP2, HPP3) are proposed, analysed and compared. Each control policy is characterized by a production and/or maintenance strategy different from the others policies, with or without the consideration of the emission aspect in the structure of the policy. An experimental resolution approach based on experimental design, simulation, and response surface methodology is applied in order to determine the optimal control policy parameters. The results show that the proposed HPP3, which integrates the emission control in the production and maintenance strategy, gives a significant gain in terms of total cost compared to HPP1 and HPP2. In addition, we integrate a preventive maintenance strategy to HPP3 in order to investigate a more general case. To illustrate the robustness of the proposed policies, several sensitivity analyses are presented to show the effect of system parameters on the structures of each policy. This analysis allows defining an overhaul and a preventive maintenance zone from the interactions between the parameters of HPP3.