The Research On Measurement Precision Of Fiber Optic Displacement Sensor

Since the beginning of the 21st century,sensor technology has been widely used in aerospace,defense research,information industry,medical equipment,industrial automation and other fields due to its high technical content,strong penetrability and good economic efficiency.Optical fiber has become one of the important materials for making new sensors by virtue of its anti-electromagnetic interference and anti-corrosion properties.In this paper,a reflective fiber-optic displacement sensor is studied,and a reflective fiber-optic displacement sensor measurement system is studied to improve its measurement accuracy.The research contents are as follows:(1)The structure and working principle of the reflective fiber displacement sensor are analyzed,and the temperature calibration experiment is carried out by means of a temperature sensor.The performance of the reflective fiber displacement sensor is evaluated by three performance indexes of zero temperature coefficient,sensitivity temperature coefficient and relative error,which confirms the existence of temperature drift problem.(2)A GA-BP model for optimizing BP neural network based on genetic algorithm(GA)is proposed,and the software method is used to compensate the temperature of the reflective fiber displacement sensor.After compensation,the zero temperature coefficient is increased from 7.57×10-3/? to 8.8×10-4/?.,the sensitivity temperature coefficient is increased from 7.57×10-3/? to 9.65x10-4/?,the relative error is increased by 25.53%to 3.47%,it can be seen that the GA-BP model can effectively eliminate the influence of temperature on the reflective fiber displacement sensor.The input-output characteristic curve of the reflective displacement sensor was nonlinearly corrected by curve fitting.The linearity after correction was increased from 6.94%to 3.5%,and good results were obtained.The working principle of the digital lock-in amplifier is studied and its possibility of improving the accuracy of the reflective fiber displacement sensor is analyzed.(3)The hardware design scheme of the reflective fiber displacement sensor measurement system is given.Among them,the DSP chip is used to realize the amplification and noise reduction of the sensor measurement signal by the digital lock-in amplifier,and the weight and threshold of the GA-BP model are stored in the processor of the MK60 chip to complete the temperature compensation,using the Bluetooth module to complete the communication between the two MCUs,and the design of the power circuit,alarm circuit and OLED display circuit.(4)Complete the programming and writing of each module in the software development platform,and perform hardware and software debugging on the whole system to ensure that the measurement system can work normally.At the end of the measurement,the displacement was measured using this measurement system.The research results show that the reflective fiber displacement sensor measurement system studied in this paper can effectively improve the measurement accuracy of the sensor and the system performance is stable.