Design and development of compact 2-axis accelerometer for pantograph-catenary system

Abstract

Designing a miniature 2-axis accelerometer is attractive for pantograph-catenary interaction system monitoring because the size and weight of sensor adversely affect the dynamic property of the pantograph. The features of fiber Bragg grating along with the femtosecond laser-based inscription technology can be utilized to make not only compact but also robust accelerometer. Therefore, this thesis focuses on designing and fabrication of a compact cantilever based two-axis accelerometer using multicore fiber (MCF) inscribed with FBG by femtosecond laser-based point by point technique. Prior to the fabrication, the stress distribution along the length and cross section of the cantilever beam structure has been evaluated using FEM based software (COMSOL Multiphysics). Furthermore, the frequency response of the cantilever structure with different length has also been investigated. The simulation results have been validated by inscribing an FBG in one of the cores of a homemade three core fiber and subsequently analyzing the frequency response as well as the response to applied acceleration along one axis. Thereafter, a two-axis accelerometer based on a commercial multi core fiber has been fabricated. The two cores of the MCF have been inscribed with well distinguished FBG using femtosecond laser-based point-by-point technique without removing the polymeric coating thereby enhancing the mechanical stability. The sensor has been packaged in a box with a total weight of 5.2 grams. The response of the packaged sensor has been studied by evaluating its performance to applied acceleration up to 5g without damping oil, and up to 25 g with the filling of the box with damping oil.