Theory And Algorithm Research On Train-set Utilization Problem Under High Speed Railway Network

Train-set as a tool of high-speed railway (HSR) transport, its utilization efficiency is one of the main factors of HSR passenger transport efficiency. Train-set circulation planning is the key task of HSR passenger transport organization, which determines the realization of train diagram, the safety, service quality and enterprise income of HSR operation. The utilization of train-set has always been a hard problem in railway transportation organization theory. Besides, the gradual formation of HSR network in China aggravates the complexity and difficulty of the problem, so new challenges exist in solving the train-set circulation planning problem. With the background of HSR network, the paper aims to investigate theoretical methods of train-set utilization,maintenance and planning. The main research contents in the study are listed as the following three aspects:(1) With the background of train-set maintenance mode in fixed allocation segment at present stage in China, the study investigates optimization problem of train-set circulation plan by introducing allopatric maintenance mode. Impacted by maintenance standard and capacity, the mode of affiliated maintenance depot is applied currently in China, which means when the cumulative mileage or time reaches the maintenance standard, the train-set must return back to its affiliated maintenance depot to get maintenance. This requirement as a strong confinement in train-set utilization,becomes a key factor of restricting the optimization of train-set circulation planning.Therefore, the study aims to introduce allopatric maintenance mode to release the constraint and enhance the train-set utilization efficiency. With the continually propelling of standard train-set, the problems in maintenance standardization are being solved gradually, which provides possibility for the realization of allopatric maintenance.The study proposes the train-set allopatric maintenance mode theoretically and builds a train-set circulation plan optimization model that fits multiple train type.Multi-populations genetic algorithm is designed to solve the model and partial train diagrams of Beijing-Shanghai, Beijing-Tianjin and Qingdao-Jinan passenger dedicated line are used as paradigms to examine the feasibility of the model and algorithm. By comparing with the traditional ant colony algorithm and the standard genetic algorithm,the multi-populations genetic algorithm presented in the study has obvious advantages in computation efficiency, stability as well as the obtained train-set circulation plan quality. Besides, the comparison of optimization results of allopatric maintenance mode and affiliated maintenance mode shows that for the same train diagram task, the allopatric maintenance mode can save 17 train-sets and the maintenance times are also reduced by 17. Therefore, the introducing of allopatric maintenance mode can improve train-set utilization efficiency effectively. Based on the research results, the difficulties in implementing allopatric maintenance mode in China and the elemental work need to be prepared are discussed in the paper.(2) With the background of the gradually formed HSR network in China, the study investigates the optimization problem in train-set circulation planning under network condition. Along with the accelerating process of HSR construction in China,the HSR network has formed preliminarily. As a tool of HSR transport, the train-set utilization mode and utilization efficiency face new challenges with the formation of HSR network. The formation of network increases the scale of train-set utilization and the difficulty of train-set circulation planning. Specifically, how to obtain train-set circulation plan of good quality within short time becomes a key problem in train-set utilization. Besides, in order to adapt to the large-scale operation in network, related research theory and method that can guide the realization of intelligent train-set circulation planning with computer is needed urgently.With the precondition of allopatric maintenance, the study uses the minimum linkage time as the optimization objective and builds train-set circulation planning optimization model under network condition. In the model solving process, the study designed a two-stage algorithm with stable solving quality and efficient solving speed,which provides theoretical basis for the realization of intelligent train-set circulation planning with computer. In order to examine the feasibility of the model and algorithm,the study solves the train-set circulation plan with partial train diagram of Beijing-Tianjin inter-city high-speed railway as a small-scale paradigm. The compared results with traditional ant colony algorithm show that the two-stage algorithm performs better in solving efficiency, quality and stability. Besides, a large-scale network composed by Beijing-Shanghai, Qingdao-Jinan, Shanghai-Nanjing, Shanghai-Hangzhou and Nanjing-Hangzhou five HSR lines is also examined as a paradigm and the results show that the presented model and algorithm in the study can satisfy demands of train-set circulation planning under HSR network condition.(3) With the background of current train-set utilization mode in China, the study investigates train-set circulation plan optimization problem that considers interstation dispatch within hub. In traditional train-set utilization, as the HSR lines are single generally and the early train-set number is small, the utilization mode of train-set is simple, which is continuing the same station operation task basically.However, with the joining of HSR in passenger hub, part of traditional railway stations and new constructed HSR stations can conduct HSR train operation and normally,connection lines are used for contact between stations in hub. Therefore, the traditional train-set utilization mode has some limitations, based on which, the study proposes a train-set utilization mode of interstation dispatch within hub to adapt the HSR network and enhance train-set utilization efficiency.With the precondition of allopatric maintenance, the study uses a comprehensive minimum value of train-set utilization number and maintenance times as the optimization objective and builds train-set circulation plan optimization model that considers interstation dispatch within hub. To solve the model, the study combines the train-set utilization problem features and designs an improved genetic algorithm based on the traditional genetic algorithm. With the paradigm of Nanjing hub and Shanghai hub on the Beijing-Shanghai HSR line, a train-set circulation plan with given train diagram is obtained. By comparing the two train-set circulation plans with and without considering the interstation dispatch within hub, results show that when the train-set can be dispatched between stations, the utilization efficiency is improved obviously. For the same given train diagram task, the presented mode can reduce 2 train-set in number required and the utilization efficiency will be increased by 2%.