Bi-level Imperfect Maintenance Strategy and Optimization for Single Component of Electric Multiple Unit

The maintenance of EMU (electric multiple unit) components is an important measure to ensure the operation reliability of vehicles. In addition, the determination of maintenance interval has direct influence on the safety of rail transport. Therefore, based on the multi-level maintenance rule of EMU in China, a multi-level imperfect maintenance policy was proposed. A component replaced in the 4-class repair of EMU was selected as an objective, and a bi-level imperfect maintenance model was established on the basis of the Weibull distribution of mileage fault. By utilizing the current maintenance rule of EMU as a template, two maintenance plans for the component were structured with maintenance cost and maintenance time as the optimal goals. The maintenance intervals and maintenance levels for each section of interest were optimized by using multi-objective genetic algorithm. Comparison with the optimization results of single maintenance mode shows that maintenance schedules based on the bi-level imperfect maintenance model can meet the reliability requirement at low cost. And maintenance schedules derived from case which does not exactly match vehicle repair levels can get higher component reliability with less maintenance costs and low requency.