Attitude variometric approach using DGNSS/INS integration to detect deformation in railway track irregularity measuring

Abstract

Track irregularity measuring is of crucial importance to ensure the dynamic driving safety of the train as well as riding comfort of passengers. Navigation-grade inertial navigation system (INS) is capable of providing highly precise attitude solution with its accumulated error calibrated by global navigation positioning system (GNSS). Moreover, the application of post-mission smoothing method could further improve both relative and absolute accuracy of the attitude output. After investigating the variometric relationship between attitude of the measuring apparatus and track deformation, we proposed an attitude variometric approach (AVA) using double-differenced GNSS (DGNSS) and INS integration to detect deformation in railway track irregularity measuring. In this method, instead of using the position solutions directly from DGNSS/INS integration like previous researchers, the three-dimensional track is mainly reconstructed by integrating the high-accuracy attitude information. Prior to the track irregularity experiment, the error characteristics of the AVA are validated by evaluating the versine deviation and the analysis shows that the proposed method could achieve high repeatability in horizontal and vertical direction by reducing the error in the concerned lateral and up directions. Besides, the impact of misalignment could be limited with a rotation correction, and a preliminary analysis shows that the new method is robust and able to maintain high precision even with a GNSS outage of 2\xa0min. A field test was conducted on a segment of real high-speed railway, and four sets of observation data over the same mission track were collected with a DGNSS/INS-based trolley. Apart from that, external reference data were gathered by a total station-based trolley. The results show that the proposed method, which demonstrates good repeatability and provides 0.3\xa0mm and 0.4\xa0mm external measuring accuracy in horizontal and vertical components for shortwave track alignment irregularity as well as 1.8\xa0mm and 2.0\xa0mm for longwave track alignment irregularity, respectively, can meet the requirements of China Specifications for Survey Engineering of High-speed Railway and be utilized in practical track irregularity measuring application.