Browsing by Subject "Condition-based maintenance"

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Open Access
Implementing condition-based maintenance: optimizing maintenance decisions in multi-component systems using Markov Decision Processes
(2021-07) Nakhost, Mahsa Abbaszadeh
Maintenance scheduling has been playing a pivotal role in many industrial areas since unexpected failures result in costly actions to bring the system back to the operating state. An advanced maintenance policy is condition-based maintenance (CBM), which schedules the maintenance actions according to the data collected from the system inspections. In this study, we present a realistic discretization method for a maintainable multi-component system that is subject to periodic in-spection. We consider CBM policy and age-based maintenance policy for critical components and non-critical components of the system, respectively. We deﬁne ageneral coststructureincludingan operatingcost which isafunction ofsystem reliability, and we explain how this operating cost must be assigned in discrete and continuous state space. We use the Markov Decision Process (MDP) to ﬁnd the optimal maintenance policy for the discrete control problem. Using the MDP model, we prove that the threshold policy is not always optimal, which is the most well-known policy in the CBM literature. Finally, we propose two policies, RL-KIT and RI-MIT, to implement the policy found by MDP in the continuous environment. We show that either of these policies can be optimal depending on the system of interest using simulation.
Open Access
Machining conditions-based preventive maintenance
(Taylor & Francis, 2007) Akturk, M. S.; Gurel, S.
In this study we propose an operating conditions-based preventive maintenance (PM) approach for computer numerical control (CNC) turning machines. A CNC machine wears according to how much it is used and the conditions under which it is used. Higher power or production rates result in more wear and higher failure rates. This relationship between the operating conditions and maintenance requirements is usually overlooked in the literature. On CNC turning machines we can control the machining conditions such as cutting speed and feed rate, which in turn affect the PM requirements of the CNC machine. We provide a new model to link the PM decisions to the machining conditions selection decisions, so that these two decision-making problems can be solved together by considering their impact on each other. We establish that our proposed geometric programming model captures the related cost terms along with the technological restrictions of CNC machines. The proposed preventive maintenance index function can be used to provide an intelligent CNC machine degradation assessment.