Research On The Non-contact FBG Vibration Sensor And Itstesting System Of The Rotating Machinery

As the key fundamental equipment of military and civilian sectors, the majorrotating machinery like steam turbines, compressors, generators and aviation enginesplay an important role in the stable development of modern industrialization. As theirkey parts such as rotor and blade are often exposed to such working conditions ashigh speed, heavy load, high temperature and high pressure and extremely harshenvironments like corrosion and electromagnetic interference, such problems as aging,failure and damage have become increasingly serious. Therefore, it is necessary to usesome effective monitoring techniques to solve the problems and avoid possiblecatastrophic accidents. In the past, it was difficult and even impossible to realizeonline dynamic monitoring as traditional measuring sensor technology was used.Traditional regular and offline maintenance may lead to potential safety hazards andlong downtime and cannot prevent sudden accidents during operation. This paperproposes a non-contact FBG vibration sensor to achieve non-contact real-timedetection of vibration of rotating shaft and overcome the shortage of traditional sensortesting technology.Based on knowledge covering such disciplines as elastic mechanics, magnetics,FBG sensing technology and mechanical design, this paper designs a non-contactFBG vibration sensor. The major work includes the following aspects:1. We stated the purpose and significance of the paper and analysed the researchstatus of the measuring technique concerning a rotating shaft vibration and vibrationsensors based on FBG sensing technology;2. Based on elastic mechanics, magnetics and principle of FBG sensing, weestablished a physical equivalent model of the sensor through theoretical derivation；conducted a simulation analysis on the performance of a non-contact FBG vibrationsensor to prove the proposal is feasible and finish the structural design of the sensor;3. We established an experimental system and designed computer programsbased on Lab VIEW and MATLAB software so as to conveniently process largeamounts of data during experiment, made a study on static and dynamiccharacteristics of the non-contact FBG vibration sensor and analysed its sensingcharacteristics. The experimental results are as follows: the range is2-2.4mm;sensitivity is-1.694pm/um; linearity is2.92%; correlation coefficients of linear fitting0.9981; straight line fitting equation is Δλ=-1694×d+4250; the repeatability error is 1.25%; hysteresis error is3.05%; the resonant frequency of the sensor is about1500HZ and the working band ranges within0~1300HZ;4. Based on Wuhan University of Technology’s experiment platform for largerotating machinery tests, we built a detection system for rotating shaft vibration basedon eddy current displacement sensor and non-contact FBG vibration sensor, anddesigned an upper computer acquisition system of eddy current displacementvibration sensor; compared and analyzed the vibration signals acquired by the twosensing systems from such aspects as time and frequency domains, which mainlyincluded:1. comparison of vibration displacement;2. extraction of critical speed ofrotating shaft;3. analysis of frequency components of vibration signals acquired bythe two sensors;4. rotational speed extraction and vibration signal comparison andanalysis of the two sensors. Through the above comparison and analysis, we canensure it is feasible to measure vibration of rotating shaft with a non-contact FBGvibration sensor.