| Multi-mode onboard train control system(hereinafter referred to as MOTC system)is the system capable of running on trackside train operation control system compatible with two or more system standards or control modes,which is of great significance to improve the flexibility of rail transportation,support interoperability for diverse rail networks,and thus create more business opportunities on rolling upgrade or revamping of signaling systems under revenue service.Availability,as core of MOTC system,is closely related to safety and efficiency of rail transportation.Current availability evaluation on onboard train control system is mostly based on the inherent availability by analyzing system composition under a predefined environment,so credibility of the evaluation is lower due to huge gap to practical system performance.In view of rapid development of MOTC system whilst shortcomings in system availability evaluation still remain,this paper studies how to improve the availability evaluation of MOTC system by establishing a reasonable and comprehensive availability index system and putting forward objective and scientific availability evaluation methods.Main research in the paper includes:1.On the basis of analysis of development background,mainstream and on-site application of MOTC systems,the generic functional architecture,mode conversion logic,system spatio-temporal characteristics and capability evaluation criteria of MOTC system are refined;A dynamic reliability block diagram based on the system’s generic functional structure set expression and inter-modes correlation is established;A simulation model of the operation scenario based on the spatio-temporal characteristics of the system and the inter-modes conversion logic is constructed;The capability evaluation criteria of MOTC system is put forward.2.On the basis of studies and analysis of requirements and parameters of evaluation,a MOTC system availability evaluation index system is established by progressive steps of "inherent availability,online operation availability and system effectiveness",meeting the needs of availability evaluation in the process of system design and delivery,operation and maintenance,R&D investment and engineering decision making.3.On the basis of analysis of MOTC system requirements,system breakdown by "task-function unit-module" is carried out.The hierarchical model of system architecture with corresponding functional set expression is established;In view of the detectable and repairable features of the redundant module carrying functional units of the system,the Markov failure evaluation method of the repairable system based on the detection rate is put forward.According to the features of dynamic correlation coupling between modes of MOTC system,the inherent availability evaluation method of MOTC system based on dynamic reliability block diagrams is put forward.Exemplified by evaluation analysis of typical systems,the results show that the inherent availability of MOTC system depends on the degree of multi-mode heterogeneity and system complexity.4.On the basis of analysis of spatio-temporal characteristics of the operation scenario of MOTC system,the correlation between the time effectiveness of mode switching and the granularity of resource utilization is established.Colored Petri net model of the online operation scenario of systems based on time constraint and space constraint is constructed,and the online operation availability evaluation method based on the simulation is put forward.Taking typical systems as example,online operation availability data is obtained after carrying out simulation and mathematical statistics of the delay distribution probability for the multi-mode random switching The results show that the online operation availability of the MOTC system is positively correlated with its inherent availability and negatively correlated with the inter-mode performance gap,and the heterogeneity between the modes should be fully considered while ensuring the excellent multi-mode performance.5.On basis of collection on the working state of the MOTC system,the capacity evaluation decision unit space is determined;the capability evaluation criterion and the capability matrix by "DEA-AHP" are established by indicators of safety,reachable capacity,automation degree and cost,and the performance evaluation method of MOTC system based on matrixes of availability,dependability and capability is put forward.This paper takes evaluation on typical MOTC system as example.The results show that the system effectiveness of the multi-mode is higher than that of monomode while new generation system higher than that of traditional system.Train autonomous control system based on “train to train” communication features much higher efficiency,indicating that the system efficiency is closely related to the technological advancement.Under the same technical conditions,the MOTC system enjoys big advantage in improving system effectiveness.The research results play an important role in formulation of backup solution and degrade plan of current mainstream train control systems,implementation of the seamless revamping solution such as the retrofit solution of Shanghai Line 2compatible with the existing train control system,selection of the suburban control system solution adapting to interoperability and research,development and deployment of the high-performance train control system.All these applications have been recognized by users,design companies and institutions. |
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