Research On Fiber Grating Displacement Sensor For High-speed Rail Beam Gap Monitoring

Due to the influence of changes in temperature,concrete shrinkage,high speed shock of the train and other factors,the gap of the bridge will change.The change in the gap of the bridge refers to the lateral displacement between the beam ends of the bridge.On a bridge with high-speed rail tracks,the change of the bridge gap will cause the change of the track structure,once the track changes due to changes in force,it will affect the safety of the train during operation,may even cause serious accidents.In order to enhance the safety of high-speed rail operation,the gap of the high-speed bridge is in urgent need of on-line displacement monitoring.Actual demand for beam displacement monitoring of high-speed railway bridge,the shortcomings of traditional electronic displacement sensors are analyzed in this paper,at the same time the principle of displacement sensing and fiber grating sensing is introduced,a new type of displacement monitoring based on fiber gratings has been proposed,on the basis of the theory of optical fiber sensing technology,a set of fiber grating displacement sensing monitoring scheme is designed.The program includes different ranges of displacement sensors to cope with the monitoring of the variation of different beam joints.In the sensor design process,the design concept of the elliptical displacement amplifier is proposed,it is compared with FBG deformation ring and sinusoidal magnification mechanism.After a lot of simulation analysis,the final sensor was in kind,and the complete experimental platform was built.The sensitivity of the sensor is 6.1pm / mm and 4.53 pm / mm,respectively.Characteristics such as high precision,high stability,anti-electromagnetic interference,no power supply of fiber Bragg grating are fully played in the design of the sensor in this paper,it has a very good application prospect in the field of high-speed rail safety monitoring.