Research On Optimal Inspection Policy For A Three-stage System Considering Production Wait

The emergence of increasingly sophisticated,complex and intelligent systems has injected strong vitality into the rapid development of modern manufacturing industry.However,modern intelligent manufacturing system is often in high speed,high pressure,high temperature,high load and other conditions of continuous operation,which greatly increases the loss and corrosion of the system,and easily lead to various faults.System failure will lead to a series of problems such as rising rate of defective products,production interruption,equipment damage and shutdown,and even lead to casualties,resulting in the interests of enterprises,reputation damage.Therefore,preventive maintenance is needed to avoid system failure.Usually,the preventive maintenance decision is made according to the result of the inspection.Through the inspection,the state of the system can be detected in time,and the system can be repaired before failure,so as to reduce the economic loss of the enterprise.The theory of delay time reveals the relationship between system inspection and maintenance and gradually becomes a research hotspot in industrial and academic fields.In actual production systems,production wait is common due to raw material exhaustion,insufficient demand,harsh operating conditions,and maintenance of other components.Taking advantage of the opportunity of product waiting for inspection can reduce the maintenance cost and improve the cost efficiency of production system.Combed the preventive maintenance based on the research,the system checks the research status in the field of strategy,and the theory of delay time and found:on the one hand,the existing research mainly focus on improve the modeling precision of the system failure process,in spare time make full use of the system(production wait)in a production system is called production work less;On the other hand,most of the existing maintenance studies on delay time are based on the traditional two-stage degradation model.However,in practice,some researchers have proved that the three-stage degradation system can provide more modeling options,which are closer to reality and have a wider application scope.Therefore,on the basis of existing relevant theories and literature research,this study considers the fault modeling of singleton system(singleton system affected only by a single fault mode)in production waiting as a three-stage degradation process,that is,the system has four states: normal state,small defect state,large defect state and fault state.Two types of inspection(two-stage periodic inspection and production wait inspection)are carried out on the system.The inspection can perfectly reveal the current state of the system.When the inspection finds the system is in a major defect,the system is updated,and when the periodic inspection finds the system is in a minor defect,the interval of subsequent periodic inspection is halved.Updates are also required when the system fails or a predetermined age threshold is reached.The cost model of maintenance inspection was established under different update scenarios,and the unit time cost of long-term operation of the system was minimized by finding the optimal periodic inspection interval and the optimal age-based replacement threshold.In order to illustrate the effectiveness of the maintenance strategy adopted in this paper in the small defect stage,two comparative models are also established for comparative analysis.The accuracy and effectiveness of the proposed inspection and maintenance model are verified by comparison with two comparison models.Furthermore,the sensitivity analysis of the model under different cost parameters is carried out,which not only studies the optimal choice of maintenance strategy under different cost parameters,but also explores the changing rules of the optimal unit time cost with different costs.It proves that the model proposed in this paper still has the optimal economic benefits under different cost parameters.Finally,this study provides useful management advice for relevant decision makers through conclusion analysis.