Design And Experimental Study Of Fiber Optic Sensor For Oil Film Thickness Of Journal Bearing

With the development of the measurement technology,the testing technology of the oil film thickness of the bearing of the large rotating machinery has been developed rapidly.Micro displacement measurement for lubricating oil film thickness,to ensure the installation distance,to meet the high sensitivity and suitable measurement range and a faint light output according to the processed signal is stable and accurate.In this paper,a reflective intensity modulated fiber optic displacement sensor(Reflective Intensity Modulated Fiber Optic Displacement Sensor,abbreviated as RIM-FODS)based on large core multimode fiber is presented and the structure and parameters of the sensor probe is optimized,the detection processing circuit of optical fiber output end reflection weak signal is designed and experimentally studied.The specific completion of the following research work:Firstly,the research significance and development status of optical fiber displacement sensor for the measurement of oil film thickness of large rotating machinery lubricating bearing is introduced and the measurement method of lubricating oil film is briefly described.Then,the theoretical calculation of the minimum oil film thickness is discussed and the single point measurement is taken as an example.The Analysis of RIM-FODS is focusing on,including the detection principle,probe structure and light distribution.The intensity modulation function is modeled by the quasi Gauss distribution light field.The influence parameters are simulated and the influence characteristics of the modulation function curve is summarized,which lays a theoretical foundation for the optimization of the structure,the choice of the designparameters and eventually establishing specific program.Then the key components of the system(optical fiber,light source)is selected and the design.Simulation and test of RIM-FODS weak signal processing circuit is completed.The detection signal processing circuit includes a photoelectric conversion circuit,notch circuit,filter circuit design and ratio processing circuit.the software simulation and PCB circuit design is completed.The finished PCB is tested and the experiment platform is set up,using the RIM-FODS system to complete the performance calibration experiment of lubricating oil film thickness measurement.Finally,the simulation and experimental results show that the RIM-FODS measurement model is reasonable,and the design of signal detection processing circuit can realize the measurement of weak light signal and the filter effect of background light is obvious.The design of the signal detection circuit has a good performance,stability and availability.The small signal can be amplified accurately,and output signal is stable,low noise,small offset.In the static calibration experiment,the sensitivity of the linear range of 1200?m~2700?m can reach 6.0mV/?m,which meets the requirement of detection.