Research On Safety Risk Evaluation Method For Satellite-based Train Positioning

The use of train positioning based on satellite navigation can greatly reduce the use of the wayside equipment and the cost.The working environment of maintenance people is improved as well by this way.The natural environment of Chinese central and western regions is relatively poor and the density of population is relatively low.With low density of railway network and poor signaling infrastructure,volume of passenger and freight transport is not high.It is a good way to use the satellite navigation system to the low-density line in this environment.The application of train positioning based on satellite navigation is a safety critical application which requires high level security.So the corresponding safety evaluation method is needed to ensure that the positioning method can meet the safety requirements of train positioning.Therefore,it is very meaningful to study the safety evaluation method for satellite-based train positioning.The safety risk evaluation method for satellite-based train positioning is studied in this paper.According to the existing performance evaluation indexes in rail and satellite navigation field,it is put forward the corresponding safety risk evaluation indexes meeting two areas of navigation and railway and the corresponding evaluation methods according to the corresponding index parameters.The main content of this thesis includes as follows:According to analysis of mapping relationship between railway RAMS and satellite navigation system quality measures by failure modes and train positioning security requirements,the Tolerable Hazard Rate(THR),the Horizontal Protection Level(HPL)and the Error Confidence Level(ECL)are chosen as the main evaluation indexes.On the basis of the mapping relationship above,a method for calculating the THR based on integrity risk is proposed and determines safety integrity level.Secondly,the horizontal protection level algorithm based on maximum deviation and noise interaction is proposed to evaluate the positioning error of the train.Finally,because the existence of misleading information in positioning data which exists uncertainty,it is chosen error confidence level to describe misleading information and the safety analysis and evaluation method based on the ARIMA model is put forward.Using the positioning data from the Qinghai Tibet line,the proposed evaluation indexes are evaluated by the corresponding evaluation methods.The comprehensive evaluation results are given and the validity of the evaluation methods is proved.Microsoft C#2010 is used to develop the navigation safety evaluation software based on satellite navigation to improve the efficiency of the evaluation.The safety risk evaluation method for satellite-based train positioning is put forward in this paper,which can be used to quantify the evaluation index and has a certain role in promoting the application of satellite navigation in the railway industry.