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AI for Services
Published in Josep Aulinas, Hanky Sjafrie, AI for Cars, 2021
Nowadays, most of these production machines and vehicles are equipped with various sensors that actively monitor and transmit vital information such as temperature, humidity, workload, fatigue, vibration levels etc. These sensors produce considerable amounts of valuable data and logs. The combination of real-time data with breakdown and maintenance history across a whole fleet or multiple production lines can be used to identify conditions and patterns that could lead to failure before it happens, hence to predict when maintenance might be necessary and to prevent significant damage. Analyzing and modeling from available data, one can estimate RUL, identify fault root cause and implement fault prediction strategies. Besides this, one can optimize maintenance scheduling, either extending the working life of some equipment or preventing major collateral damage to other equipment, both of which can result in risk minimization and a reduction in repair costs, waste, production downtimes and associated losses.
Introduction to loads and structures
Published in Martin O. L. Hansen, Aerodynamics of Wind Turbines, 2015
After having described in detail how to calculate the aerodynamic loads on a wind turbine, the following material concerns structural issues to ensure that the construction will not break down during its typical design lifetime of 20 years. Normally a breakdown is caused by an inadequate control system, extreme wind conditions, fatigue cracks or a defective safety system. A very dangerous breakdown may occur if the power to the generator is lost. There is then no braking torque on the rotor which, in the absence of a safety system such as mechanical or aerodynamic emergency brakes, is free to accelerate. Because the aerodynamic forces increase with the square of the rotor speed, the blades will bend more and more in the downwind direction and might end up hitting the tower or flying off due to centrifugal forces. It has been estimated (Sørensen, 1983) that blades sheared from an over-speeding wind turbine can land up to about 300 metres from the tower. Fortunately, violent failures are extremely rare and no humans have, to the author’s knowledge, ever been reported to have suffered injuries from debris flying off a wind turbine. Safety standards, such as (IEC 61400, 2004), exist to ensure that wind turbines operate safely. The standards define load cases, such as extreme gusts, which a wind turbine must be able to survive. Lightning is also known to have caused disintegration of blades.
Optimal decision of an economic production quantity model for imperfect manufacturing under hybrid maintenance policy with shortages and partial backlogging
Published in International Journal of Production Research, 2019
Xinfeng Lai, Zhixiang Chen, Bopaya Bidanda
Just as our mentioned at the beginning, maintenance policy has an important influence on the production decision; naturally, incorporating maintenance strategy into the production decision models has become a new stream of academic study in the production and maintenance areas. Summarily, in literature, three types of maintenance policies are considered (Horenbeek et al. 2013): Failure-based maintenance (FBM) or called corrective maintenance. In this policy, whenever a failure occurs, maintenance (machine repair) begins to perform immediately. In our paper, we name it as emergency maintenance, since it happens emergently when the machine breakdown stochastically occurs. This type of maintenance policy is scarcely studied.Preventive maintenance (PM). In this policy, planned maintenance activities are aimed to prevent the occurrence of machine breakdown or imperfect production. In literature, this type of maintenance is most frequently studied.Condition-based maintenance (CBM) or predicted maintenance. This policy tries to measure the condition of machine and decide to perform maintenance or not. In literature, this type of maintenance policy is seldom studied.
A two-stage assembly flow-shop scheduling problem with bi-level products structure and machines’ availability constraints
Published in Journal of Industrial and Production Engineering, 2022
Mohammad Ali Nikouei, Mostafa Zandieh, Maghsoud Amiri
Most scheduling studies assumed that machines were always available for processing on the scheduling horizon. It means that the probability of machine breakdown during the production period is negligible. However, machines are subject to breakdown due to several reasons. Preventive maintenance activities are performed to mitigate machine breakdown risks. Considering preventive maintenance operations brings the model closer to reality.