Study On Algorithm And Application Of Fiber Bragg Grating Demodulation Of Temperature And Strain

To reduce the failure rate of the spacecraft in orbit and test if specimen can meet the requirements of thermal conditions shift spacecrafts are needed adequate space environment simulation test on the ground before launch. Vacuum Thermal Test is one of the most important test in the space environment test, which the strain and temperature are two important indexes the test concerns. Since the fiber grating has the advantages of high precision, anti-jamming, wavelength code etc., measurement of the temperature and strain is adopted by optical fiber grating of temperature control system in vacuum thermal test. Furthermore, the precision of strain and temperature directly affects the sensing properties of fiber grating. Hence, studying more advantageous demodulation algorithm of fiber Bragg grating temperature and strain has important practical significance to accurately simulate the environment of the spacecraft in orbit and to improve the reliability of spacecraft.In this paper, by analyzing domestic and international research status of fiber Bragg grating demodulation, aimed to observe distribution characteristics of fiber Bragg grating sensor system based on historical data, without changing the existing hardware of demodulation system,the technical route of several demodulation algorithms is proposed in this thesis. The main research work is as follows.First of all, we propose several demodulation algorithms of fiber grating temperature and strain based on the demodulation equipment of tunable F-P filter without changing the original equipment, which is according to the distribution characteristics of history data in the fiber Bragg grating sensor system.Secondly, the details of fitting algorithm based on BIC criterion for model selection(BMSFA), fixed endpoint linear fitting algorithm(FELFA) and adaptive section linear fitting algorithm (ASFLA)are expressed. The algorithms are evaluated with field test data, and ASFLA(2) is better comparing with other algorithms. Furthermore, ASFLA is improved aimed at boundary value problem.Finally, Graphical User Interface (GUI) of fiber grating temperature and strain offline fitting system and online demodulation system is built in MATLAB software environment. This system can expediently output and save the evaluation index of each algorithm. Furthermore, the system can meet the test requirements by field test.