Turnout Maintenance Scheduling Problem Considering Reliabilities:Modeling And Optimization

The rapid development of railway transportation industry in China has increased the efficiency of transportation but also brought more pressure on railway tracks.As an important signal equipment of railway system,turnout is responsible for changing the pathes of trains.The quality of turnouts impacts the safety and efficiency of railway transportation directly.With the increase of the number of passengers and freight,one of the most important tasks of railway department is to ensure the safety and reliability of railway turnouts system,which requires enhance the maintenance of railway turnouts.Excessive maintenance tasks have brought heavy pressure on maintenance teams and a great deal of financial and material resources.Therefore,it becomes the key task of railway department that how to reduce the maintenance cost,meanwhile,the reliabilities of turnouts can be ensured by increasing routine maintenance of railway turnouts.The maintenance costs can be reduced and the maintenance efficiency can be increased by arranging maintenance plans and determining the routine maintenance time of each turnout in railway system reasonably.Based on these,this thesis will study the routine maintenance of railway turnouts combining reliabilities and maintenance pathes of maintenance teams.The main contributions are as follows:(1)Focusing on the reliability researches of railway tracks and the maintenance scheduling problem of railway tracks,the related papers published on domestic and international journals are consulted comprehensively.The research problems in references are classified and summarized.(2)Regarding a turnout as a node,a mathematical model of maintenance scheduling problem considering the reliability of single turnout is established aiming at minimizing the total maintenance costs.This problem can be seen as a variant of the multiple traveling salesman problem with time window(m-TSPTW).It differs from the classical m-TSPTW in at least two aspects.On one hand,each node has multiple time windows among which only one can be selected.On the other hand,each node has a reliability constraint.A linearization process is presented to solve the problem by a series of mathematical transformations.A number of experiments are also carried out to verify and evaluate the correctness and effectiveness of the model.(3)Based on the reliability of the whole railway system,we divide the railway system into "turnout-line" level and "line-system" level by using the track element method.The reliability relational expressions of the two levels are established respectively by using the reliability block diagram.Then the reliability relational expression of "turnout-system" can be obtained by integrating the two expressions.For"turnout-line" level,a mathematical model of maintenance scheduling problem considering the reliability of track line is established.For "turnout-system",a mathematical model of maintenance scheduling problem considering the reliability of railway system is established.The correctness of the two model is verified by solving a number of instances.Adjusting several key parameter,the influence of key parameters on the result of the problem is obtained through experimental analysis.Finally the general rule of reducing the maintenance cost is summarized.