Research On The Two-dimensional FBG Vibration Acceleration Sensor And Its Application

The research on vibration of mechanical system is very important.Structural health monitoring is of great significance for the stable operation of the machinery equipment.Because once recognize vibration conditions of equipment in advance,and propose corresponding solutions,then unnecessary economic losses can be avoided.As an important characterization of vibration,acceleration can be used as vibration monitoring parameter.Traditional electromagnetic acceleration sensor is of some natural deficiencies,such as susceptible to electromagnetic interference,complex signal transmission cable and so on.These weaknesses may affect its application in some special occasions.However,FBG sensors have advantages ofimmune to electromagnetic interference,distributed measurement,etc,which can overcome shortcomings of electromagnetic sensors.Meanwhile,mechanical vibration is usually multi-dimensional.Therefore,designing a kind of multi-dimensional FBG acceleration sensor is of great help for structural health monitoring.In this paper,a new two-dimensional FBG vibration sensor is proposed,which is based on the parallel arrangement of the double metal beam and the optical fiber.Based on the principle of fiber Bragg grating sensor,the theoretical analysis and experimental study of the scheme are carried out.Copper wire,optical fiber and the inertial body are connected by AB glue,and both ends of copper wire and optical fiber are fixed on the shell of sensor.Double wire and fiber Bragg grating form the statically determinate beam elastomer with a isosceles triangle shape,and two FBGs are distributed on both sides of the inertial body.The vibration decoupling of plane x/y direction can be realized by the two FBGs.With the involving of copper wire,the problem of easy to brittle fracture when FBG bears tension and compression alone can be eliminated.Firstly through the vibration mechanics and the theory of fiber grating sensor establish the theoretical model of two-dimensional fiber grating vibration sensor,and the dynamic characteristics of the sensor are analyzed by using the finite element method;finally through experimental study on static and dynamic characteristics of sensor,effectively verified the correctness of this model.The experimental results show that the resonance frequency of the sensor in the radial direction of optical fiber(y-axis)is 225 Hz,and the amplitude flat area is 10-150 Hz,the sensitivity is 54.13pm/g in the range of 0-5g,and thelinearity is 4.34%,the repeatability error is 2.04% and hysteresis error is 0.97%;The resonance frequency of the sensor in the axial direction of optical fiber(x-axis)is 1074 Hz,the amplitude flat area is 10-750 Hz,the sensitivity is 21.56pm/g in the range of 0-10 g,and the linearity is 3.78%,the repeatability error was 3.05% and hysteresis error of 0.54%.Finally,the two dimensional FBG vibration acceleration sensor is applied to the "rotary machinerytest platform of Wuhan University of Technology",to verify the feasibility of the vibration monitoring.So,these performance indicators can meet the actual engineering requirements.