Optimization Of Overhaul And Heavy Repair Scheduling Of Urban Rail Transit Trains Considering Flexible Operation

The development of urban rail transit systems incurs a rapid increment in the number of trains and maintenance requirements.As the high-level maintenance process of trains,overhaul and heavy repair operations(OHRO)have long maintenance downtime,complicated processes,and many uncertain factors.The improvement in the efficiency and quality of OHRO on trains promotes high operational safety and reliability and costsaving.In the OHRO on trains,the maintenance operation schedule integrates the detailed maintenance operations and resources,which becomes the basis for the maintenance organization.However,due to the complex relationship between various elements in OHRO,the current maintenance work is mainly carried out with manual scheduling.The manual schedule may lead to low efficiency and difficulty in task connections.Therefore,an automatic method of scheduling optimization for OHRO on trains is the key to improving the efficiency of maintenance implementation.Based on the above background,this paper researches the OHRO on trains in the urban rail transit system with the following content.Firstly,based on relevant literature,this paper analyses the characteristics of the OHRO scheduling problem and the similarities between the problem with the flexible job shop problem(FJSP)and the equipment maintenance operation scheduling problem(EMOSP).The operation content and mode,craft characteristics of current OHRO on urban rail trains are summarized.On this basis,a flexible operation craft for OHRO on urban rail trains is proposed.Then,a three-level structure of the urban rail OHRO project is established based on the work breakdown structure theory and method.An adapted FJSP mathematical programming model with updated constraints is proposed according to the characteristics of the craft sequence relationship of activities in OHRO.Based on the proposed FJSP model,a scheduling model for OHRO optimization is arranged to minimize the total duration of the maintenance operation of all trains in the maintenance warehouse.Finally,a genetic algorithm is improved to solve the OHRO scheduling problem by simultaneously considering the maintenance group selection and operation activities sequence.The decoding mechanism,initialization method,and calculation operators are designed to improve the solution quality and efficiency,which is verified according to the comparison with the Gurobi solver.Based on the case analysis of an overhaul and heavy repair depot,the optimization plans of OHRO under various operating scenarios are solved,which proves the correctness and effectiveness of the model and algorithm.The bottleneck of the maintenance capacity in the OHRO depot in the case of single-train heavy repair,single-train overhaul,and multi-trains overhaul,and heavy repair operation are respectively illustrated.Additionally,the influence of maintenance craft on the optimization of single-train overhaul and heavy repair operation scheduling is further explored.It proves that the flexible operation craft for OHRO can increase the space for optimization of operation scheduling,which is beneficial to reduce the total time of the maintenance operation of all trains in the OHRO depot.