| In a train control system,train location plays an important role in guaranteeing train safety interval,generating control speed curve and indicating train moving state.The traditional train positioning method needs a lot of trackside equipment and cannot achieve continuous high-precision positioning.Precise Point Positioning(PPP)is a high-precision positioning method in Global Navigation Satellite System(GNSS),which can achieve centimeter-level positioning accuracy with a single dual-frequency GNSS receiver.The tight coupling of PPP and Inertial Measurement Unit(IMU)can provide continuous high-precision positioning information for trains,and meanwhile get train positioning rid of base station and trackside equipment,saving cost of construction and maintenance.In order to construct and improve the train positioning method based on PPP,the GPS and Bei Dou Navigation Satellite System(BDS)were combined to enhance the adaptability of the positioning system in the complex long distance railway environment.Therefore,the train positioning method based on multi-GNSS PPP/IMU were proposed.In addition,because the positioning accuracy of ranging signal in multi-GNSS system will be declined by multipath or interference during transmission process,the fault detection and adaptive process method was studied and its positioning performance was verified in real train moving situation.The main research contents of this thesis include:(1)The train positioning method based on multi-GNSS PPP was constructed.The real-time multi-GNSS ultra-rapid precise ephemeris product was chosen to replace the broadcast ephemeris.The error factors affecting the positioning accuracy were comprehensively analyzed and modeled to correct according to train moving environment.Therefore,the observations model and Kalman filter parameter estimation method of train positioning method based on multi-GNSS PPP were constructed to provide real-time and high-precision train position solution scheme without trackside equipment.(2)The tightly coupled multi-GNSS PPP/IMU train positioning method was proposed.Based on the multi-GNSS PPP method,inertial sensors was introduced to complete loosely coupled positioning method to enhance system independence.The tightly coupled multi-GNSS PPP/IMU positioning method was studied to solve the problem that positioning performance of loosely coupled method was limited by the number of available satellites.(3)The multi-GNSS PPP/IMU fault-tolerant navigation method was studied,including fast fault detection based on filter innovation and adaptive fault-tolerant filter method.The fault detection compare equation was constructed by satellites measurement innovation of multi-GNSS system and its statistical distribution to quickly detect their appearing time and location of faults.After identifying faults,the fault discriminant is calculated to carry out the classification and adaptive processing,so as to realize the rapid monitoring and effective conduct of the faults in satellite measurements.Experimental results showed that the tightly coupled multi-GNSS PPP/IMU train positioning method can provide decimeter level results for train positioning.With a strategy of multi-GNSS positioning,the positioning accuracy of tightly coupled PPP/IMU positioning method was performed better than PPP method and loosely coupled PPP/IMU positioning method with a development of 52.1% and 49.4%,respectively.In addition,tightly coupled multi-GNSS PPP/IMU positioning method could still maintain stable and available positioning information output under GNSS blocked situation,which was more reliable than single constellation system positioning.The simulated experiment about fault injection showed that the proposed fault detection method could quickly identify appearing time and location of faults,and classify and deal with the faults according to the predefined fault processing methods,so as to ensure smooth and adaptive train positioning results output.This thesis contains 53 figures,7 tables and 87 reference. |
PDF Full Text Request