On-board Dynamic Measuring of Long-wave Track Irregularity based on Visual Inertial Fusion

This paper studies an inspection method to measure the long-wave track irregularities using the signals of IMU (Inertial Measurement Unit) and Laser & Camera installed on a bogie, which is implemented in comprehensive inspection trains. To reduce the influence of random noise and vehicle vibration, the mechanical structure is optimized; the spatial-dependent change of the "two-point chord" on the track is observed by high-precision FOC (Fiber Optic Gyroscope) and laser camera components; the angular velocity measurement method is deduced. To eliminate high-frequency attenuation of the signal, a sensor fusion algorithm based on the concept of complementary filters is presented. The angular velocity-based method is also used to measure low spatial frequencies, while the acceleration-based method is used to measure high spatial frequencies. The measurement accuracy of the system is evaluated from two aspects: internal and external coincidence accuracy. The test shows that the repeatability accuracy of the system to alignment and profile of the wavelength of 200 m is 0.5 mm and 0.8 mm, respectively, and the trend item and the line design value maintain good consistency.