Operation Risk Analysis On Train Dispatching System Of High-speed Railway And The Method For Real-time Timetable Reschduling

The normal condition of high-speed train dispatching system can keep the safety,punctuality and effectiveness of high-speed system and it is also one of indispensable parts for the dispatching system,thus it is necessary to enforce the risk analysis by clarifying characteristics of the hazards with regard to railway infrastructure,environment,weather and railway staff,to keep the stability and robustness.Those unavoidable hazards result in the disturbances or disruptiond for the high-speed railway system.Due to the negative influence caused by disturbances/disruptions,i.e.,infrastructure failures,bad weather or accidents,another important purpose of this thesis is to find an effective timetable rescheduling method to mitigate trains delays and avoid conflicts between trains or infrastructure.An intelligent decision support scheme not only improves the reliability of this system to deal with abnormal events,but also can relaxes the heavy workloads of train dispatchers.As a result,this thesis aims to give a detailed description for the internal function of train dispatching system,analyze the comprehensive risk factors,and provide an effective conflict resolution to reduce effects of hazards.In detail,based on the existing research works regarding to safety theory and operational research methods,the core role of train dispatching system is demonstrated by considering the information transferring format in the whole dispatching system,as well as the inherent features of various information.Then the transition mechanism from one unstable state to another different state of train dispatching system is also displayed in this thesis.On the behalf of machine and environment,the potential hazards are identified and evaluated to rank their frequency probabilities,effect degrees and risk degrees.With regards to human errors,the reliability of human behave is measured as well.At last,an optimizing model is built to address the conflicts resulted from hazards determining speed limitations.The detail work is listed as follows:(1)An overview of the current safety management related to railway system,emergency processing,and timetable rescheduling under disturbances/diruptions is carried out in the first section,where most of domestic articles focus on the one special event/accident related to system safety,or qualitative analysis rather than the quantitive analysis,so one problem is the scarcity of comprehensive analysis on train dispatching system,and the other is the demanding to figure out a suitable quantitive analysis based on the history recorded date.Through some surveys on the real-world train dispatching systems from different railway bureaus,the railway operation rules,work content,history data are collected and prepared for the evaluation in the following research work.(2)As high-speed railway dispatching system is a large complex system including multi-objects,multi-tasks and multi-levels,it is essential to confirm or test the role of train dispatching system,which is a part of the whole dispatching system.On the basis of the graph network theory,a weighted undirected network is established to describe this system.Combined with information entropy theory,the weight of each arc is calculated according to the characteristics and amount of on-boarding information on each arc.Furthermore,important degrees of nodes,stretch degrees,correlation matrix,and path functional matrix are formulated to study the interaction relationship between nodes and arcs by the means of complex network theory.Finally,the problem-solving process is designed and the complexity of the algorithm is analyzed.Additionally,the experimental test is carried on the dispatching network of high-speed railway to reach the conclusion about the topology structure,that train dispatching system is the core of the system,and the second-central cycle around train dispatching system consists of CTC equipment,power dispatching system,dispatching scheduling system,plan dispatching system,the dispatching system of the service and vehicle dispatching system.In this way,the priority of train dispatching system is demonstrated and the main information corridor is used to connect trains and train dispatching system through the CTC and the RBC.(3)The dissipation theory is applied to describe the fluctuation of entropy,interaction among internal elements in the train dispatching system,which is an open,nonequilibrium and nonlinear system.When abnormal issues occur in the human,machines or environment sub-system,the stability of train dispatching system is effected by the change of entropy.In this section,the difference between actual train running lines and original planned train lines is treated as one of crucial criterions.The exchange between the system and outside substances,power and information relates to the entropy flow,and the entropy of sources are classified into three groups,i.e.,speed limitations,abnormal stops and conflicts/crash between trains.At last,the root causes which result in the change of entropy flow and entropy of source,are events of cause-effect,i.e.,infrastructure failures,human failures and bad weather.As a result,the transition of different states for the train dispatching system is a comprehensive,complicate interaction among the above factors.(4)The hazards related to railway infrastructure and environment can disturb the normal performance of train dispatching system.In this section,all the recorded hazards are divided into eight categories,i.e.,bad weather,vehicle on-board equipment failure,electrical failure,track system failure,train body failure,communication equipment failure,dispatching human interface failure and others.With the aim to better understand the influences of those hazards,the statistical characteristics of those hazards and delayed traffic are studied,by applying the maximum likelihood estimation to evaluate the probability density distributions of the different hazards.A zero-truncated negative binomial distribution model is then developed to link the hazards and the amount of delayed traffic.This is important to determine the probabilities and the impacts of those hazards.Then a simulation integrates the probability and influence of the hazard to assess the risk degree of each kind of hazard.It suggests which hazard should be tackled firstly in order to reduce the impact and probability of disruptions as much as possible.(5)In the dispatching and management system of high-speed railway,the dispatching terminal equipment is used by dispatchers who manage the running high-speed trains and related production activities,so the reliability of dispatcher is directly related to the safety of operation for high-speed trains.In this section,THERP theory is introduced from nuclear plant industry to calculate the failure rate and the corresponding confidence intervals of dispatchers with neglecting the work duration,combining with the characteristics of their performance.According to the Markov chain theory,the probability state transferring equations are established to study the law of the dispatcher reliability under a certain influencing factor,by Laplace transform.Finally,the task about setting train speed limitation proceed by the dispatcher is taken into an experimental to analyze the static and dynamic reliability rates,when the person is under the influence of different levels of pressure.The results show that human error rate about setting train speed limitation is lowest(0.0104)under medium pressure state.(6)Chinese high-speed railways is still confronted with disruptions,which impact on the reliability of the traffic and the passenger satisfaction.This part presents a rescheduling model which is able to solve the critical problem of effective disruption management(namely,fast and dynamic train speed adaptation and supervision of braking due to incidents,warnings or alarms),and consider in detail the signalling and safety systems based on a quasi-moving block system with variable headways.The modelling of efficient traffic management measures and the supervision of speed are integrated,braking and headway in one general job-shop model.A commercial solver with a custom-designed two-step method is used to speed up the procedure in order to solve instances from real-world high-speed networks in China quickly.Overall,the approach guarantees the resolution of the traffic control and speed management within few minutes of computation.The output demonstrates that the proposed approach can achieve a reduction of train delays by 70%compared to the solution determined by keeping the order of the original timetable,and solve to optimality more than 90%of instances for a realistic case.