A Design Capacity Analysis Method Of Ultra-high-speed Maglev Based On Improved NSGA-Ⅱ Optimization

As a cutting-edge key technology included in the "Outline of the Construction of a Strong Transportation Country",the low vacuum tube ultra-high-speed maglev mainly adopts superconducting magnetic levitation technology to realize ultra-high-speed operation in a low vacuum tube,which is a green intelligent transportation mode mainly for passenger transportation,taking into account freight transportation and military use.As an important indicator to measure the satisfaction of public transportation services and the use of train capacity resources,the design capacity of ultra-high-speed maglev has attracted much attention.However,there is no research on the capacity analysis of the ultra-high-speed maglev.Traditional capacity analysis methods of rail transportation generally calculate the capacity of stations and sections separately,which makes it difficult to realize quantitative assessment of the capacity of scheduled passing and overtaking operations.Therefore,this paper proposes a method of station-section integrated capacity analysis based on the improved non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ)optimization from the perspective of signal system design for the ultra-high-speed maglev.And the details are as follows:(1)The models including the line infrastructure based on sections,the train dynamics and the Automatic Train Protection(ATP)system are established,which consider the characteristics of the ultra-high-speed maglev.And the blocking time model for different types of sections is established,which considers the control model of ATP system,interlocking and related signaling times.(2)A capacity calculation model of ultra-high-speed maglev bottlenecks is established based on the Max-plus Automata theory and the blocking time model.(3)An optimization algorithm for section design based on improved NSGA-Ⅱoptimization is designed with the objective of minimizing the number of sections and the average departure headway to realize the rational design of the sections.(4)Based on the most unfavorable route occupancy plan and the optimization results of section design,the station-section integrated capacity calculation model is constructed by designing a capacity solving algorithm,in which the capacity solving algorithm includes three functional modules of compression,conflict detection and conflict adjustment.(5)In order to solve the problems in the integrated conflict adjustment module,such as the judgment of overtaking,the adjustment between the train headway and the scheduled waiting time,the conflict adjustment strategy optimization algorithm based on improved NSGA-Ⅱ is established in combination with the operation plan quality evaluation indexs,and comprehensive evaluation indexe is designed to screen the optimal solutions.Finally,the feasibility and effectiveness of the method is verified by designing four train operation plan schemes for a five-station,four-section line of ultra-high-speed maglev as an example.The conclusions are as follows:(1)The integrated capacity analysis can realize capacity assessment under complex operation scenarios.(2)The unevenness of capacity is exacerbated by the passing through non-stop of the ultra-high-speed maglev,resulting in a significant increase in the average departure headway.The organization of the station stops with balanced station-stop times can achieve the maximum capacity.(3)The optimized design of the block sections shortens the average departure headway by up to 29.9 s,which can significantly improve the capacity.(4)The pareto optimal solutions of the conflict adjustment strategy optimization is compared,showing that the algorithm based on comprehensive index screening can significantly improve the quality of train operation plans.(5)It is found that the NSGA-Ⅱ outperforms the vector-evaluated genetic algorithm(VEGA)in terms of counting index,convergence index,diversity index and super volume evaluation index by comparing the solution set quality under the VEGA based on linear weighting method and the improved NSGA-Ⅱ,which shows the excellent performance of the improved NSGA-Ⅱ.In summary,on the basis of maximizing the line design capacity with minimum section cost and ensuring the quality of train operation plan by taking into account the train travel time and design capacity,the capacity analysis method of ultra-high-speed maglev based on improved NSGA-Ⅱ optimization proposed in this research can achieve scientific and accurate quantitative capacity assessment under complex operation scenarios,which is of great significance to guide the economic,reasonable and scientific system design and plan of ultra-high-speed maglev.There are 45 figures,26 tables,and 99 references.