Optical-inertial system for railway track diagnostics

The paper presents the results of development of the Optical-lnertial System for Railway Track Diagnostics. It is demonstrated that in order to implement the solution at a speed of up to 430 kmph (used for example in South Korean high-speed train HEMU-430X, standing for High-Speed Electric Multiple Unit 430 km/h experimental) while satisfying the accuracy of 0.1…0.5 mm during measurement of longitudinal level, cross level, twist, curvature, rail profile, etc., it is needed to combine the optical scanners of the inner profile of the rail line with the strapdown inertial navigation system (SINS) in a single block. Supplying of odometer and Global navigation satellite system receiver (GNSS) into the system structure allows to determine measurement point position. Thanks to our a priori knowledge of the semipermanent nature of the railway track, and also to the fusion of the odometer data and satellite navigation system reception equipment data, it is possible to use fiber-optic gyros as the sensitive units of the SINS (both open-loop and closed-loop configurations of FOG can be used). The distinctive feature of the system's algorithm is that it solves both the navigation/orientation task (i.e. it fuses odometer data, satellite navigation system data and inertial navigation system data), and the task of measuring the inner surface profile of the rail line. The use of a sole odometer to localize the found rail flaws does not provide satisfactory results because of its errors. Integration of the odometer, SINS and GNSS receiver data offers highly accurate referencing of diagnostic results to the traversed track coordinate. Odometer readings are updated using the navigation system data. The system provides measuring of the track geometry and accurate localization of the measurement point using the geographical coordinates (latitude and longitude) and orientation parameters (roll, pitch and course angle). The possibility of using SINS based on fiber-optic gyros (FOG) for railway applications is considered in the article. Some practical results are given.