Matching Grating Method Strain Measurement And Its Application In Rocket Weapon System

Fatigue and damage exist in many structural parts of rocket launching system,especially in some key parts of undercarriage and landing gear,such as the support part of the rotary seat on the undercarriage,the side frame of landing gear and the trunnion.The fatigue and failure of these parts will affect the stability of rockets launching,so it is necessary to monitor the deformation and strain data of these parts in real time.In this paper,a strain measurement system based on matched grating demodulation is designed.With Bragg grating as sensing element,a matched grating demodulation method is adopted,which combines with optical power meter to convert strain measurement into power of optical,which greatly reduces the difficulty of the implementation,cost and volume of the whole measurement system.Compared with traditional resistance strain detection,FBG is smaller,lighter and anti-electromagnetic interference,which can better meet the requirements of stress and strain monitoring system for rocket launcher components.This paper includes the following contents:(1)The design of strain measurement based on matched grating demodulation;(2)Analysis using numerical simulation software of the spectrum of Bragg grating reflectance,the influence of physical parameters of Bragg grating on its reflectance spectrum.By simulating matched grating demodulation and the sensing grating,the variation law of superposition spectrum is obtained;(3)The Bragg grating strain measurement experiment and strain gauge calibration system are built.By loading the cantilever beam and comparing the surface strain data obtained by the two methods,the strain function relationship of the grating measurement system is finally obtained;(4)Comparing the deviation between the measured data and the actual value under different calibration methods,and choosing the better strain function relationship.The fractional errors of grating strain measurement system are obtained under multiple dynamic loading experiments.The rules and causes of errors in grating strain measurement system are analyzed.And the repeatability of the measurement system is studied.The feasibility of matched grating demodulation is verified by experiments.Through the above research,the Bragg grating strain device based on matched grating demodulation meets the design requirements;the strain values measured by the strain function of grating measurement system are in good agreement with the actual values,which verifies the change regulation of the superposition spectrum of the matched grating demodulation and the sensing grating.