Research Of ELoran Time Service Monitoring Evaluation Method And System Design

With the continuous advancement and enhancement of the satellite-based time service system,users have formed a strong dependence on the satellite-based timing system.However,the satellite-based time service system is naturally vulnerable to interference,attack,the weak signal and other deficiencies,there are major security risks.As a completely independent land-based time service system,enhanced Loran(eLoran)system has the advantages of high transmission power,high reliability and strong anti-interference performance.It is an effective supplement and enhancement to the satellite-based time service system and has important applications value.The national "13th Five-Year plan" major science and technology infrastructure--the Highprecision Ground-based Time Service System and Chinese Beidou satellite navigation system jointly construct Chinese space-earth integrated time service system.As a part of eLoran system construction,time service monitoring station is an important link in system design and operation,as well as an important part to ensure time service safety.The time service monitoring station provides a means of monitoring and evaluation for the eLoran system,and also improves time service reliability by publishing monitoring data to users.It is necessary to carry out the research of eLoran time service monitoring and evaluation method for users to obtain more reliable timing service.The thesis is closely combined with the construction of the High-precision Ground-based Time Service System,and conducts research on eLoran time service monitoring and evaluation and monitoring system design.The main research contents and innovations are as follows:(1)A comprehensive and systematic study of the time service error distribution of eLoran system,especially the influence of atmospheric conditions on time serviceBased on the comprehensive and systematic analysis of eLoran time service signal propagation characteristics,the time transfer law of eLoran time service system is given,the time service model of eLoran time service system is established.The eLoran time service error is analyzed in detail.The influence of solar eclipses and climate change in winter and summer on eLoran time service monitoring were studied,and an experiential system was designed to verify it.Among them,the quantitative impact of solar eclipse on eLoran has important scientific significance.(2)The methods of monitoring receiver delay calibration and time service signal quality monitoring and calibration are systematically studied,and an evaluation method for monitoring receiver delay calibration uncertainty is given.Monitoring receiver is the key to the time service monitoring equipment.Aiming at the phenomenon of inconsistent receiver delay calibration method and performance characterization,combined with eLoran time service characteristics and user requirements,the monitoring receiver calibration method was systematically studied,and a monitoring receiver delay calibration platform was built.The two methods of segment calibration and overall relative calibration are analyzed,and the evaluation method of calibration uncertainty is given,which provides academic basis and professional guidance for the calibration of monitoring receivers.(3)The eLoran time service performance evaluation index system is systematically combed,and eLoran time service performance evaluation method is given,which provides theoretical support for the formation of long wave time service signal monitoring industry standardsThe meaning and characteristics of many representational parameters such as accuracy,accuracy,uncertainty,root mean square and 95% points for evaluation eLoran time service performance are sorted out.Combined with user requirements,the time service performance evaluation index system that can fully reflect the characteristics of eLoran time service performance is given.Experiments are designed to evaluate and authenticate the evaluation index system.GUM method was proposed to evaluate the uncertainty of eLoran time service monitoring system,a complete monitoring and measurement model was established,and the evaluation of GUM method standard uncertainty was compared and verified.Relevant research results promote the standardization and normalization of eLoran time service performance monitoring,and provide theoretical support for the formation of the industry standard " Technical Requirements for Long Wave Time Service Signal Monitoring ".(4)TOA data forecasting methodIn order to improve the judgment of system integrity by a single receiver,an anomaly identification method based on the comparison between the TOA data predicted value and the measured value was proposed,and the method key element,the TOA data forecast method was studied.In order to repair missing data,the repair effect of the two methods was analyzed,and polynomial repair method was recommended.Aiming at the sudden jump data detection,four methods of sudden jump data detection were studied,and the optimal Vondrak data smoothing method was given.Design experiments to analyze the grey model,quadratic polynomial,and BP neural network methods for TOA data forecasting.According to the characteristics of different methods,a combined model forecasting method suitable for TOA characteristics was proposed.The superiority of the combined model in TOA data forecasting was proved in terms of forecasting accuracy and forecasting stability.(5)Based on the above research foundation and facing the actual needs of national major projects,the engineering implementation method and engineering scheme of eLoran time service monitoring system were studied and designedAiming at the actual needs of the High-precision Ground-based Time Service System,on the basis of the previous research,the engineering elements such as the technical architecture,physical composition,and work flow of the time service monitoring system are analyzed.Two hierarchical monitoring methods of single station fine-quality observation and multi-point comprehensive observation are proposed,and the engineering implementation scheme of eLoran time service monitoring system is designed,which provides guidance for the construction of High-precision Groundbased Time Service System.Facing the major national needs,this thesis systematically studies eLoran time service monitoring and evaluation method and standardizes the eLoran time service evaluation index system and evaluation method.The research results of this thesis provide guidance for the construction of High-precision Ground-based Time Service System,which has scientific significance and engineering application value.