Leal-Junior Arnaldo, Biazi Vitorino, Marques Carlos, Frizera Anselmo
Mechanical Engineering Department, Federal University of Espírito Santo, Vitória 29075-910, Espirito Santo, Brazil.
Graduate Program in Electrical Engineering, Federal University of Espírito Santo, Vitória 29075-910, Espirito Santo, Brazil.
Sensors (Basel). 2022 Jul 18;22(14):5355. doi: 10.3390/s22145355.
This paper presented the force and displacement analyses of a diaphragm-embedded fiber Bragg grating (FBG) sensor. In the first step, a numerical analysis (via finite element method) was performed considering linear elastic materials, where there is a linear variation on the strain in the optical fiber for both displacement and force (or pressure). In the second step, the experimental analysis was performed using two approaches: (i) controlling the displacement applied in the diaphragm-embedded FBG (while the force is also measured). (ii) Controlling the force applied in the sensor (also with the measurement of the displacement). Results showed reflected optical power variations and wavelength shift following the application of displacement and force. The sensitivities of both wavelength shift and optical power were different (and non-proportional) when displacement and force were compared. However, a higher correlation, determination coefficient (R) of 0.998, was obtained in the analysis of the wavelength shift as a function of the displacement, which indicated that the strain transmission in the optical fiber is directly related to the strain in the diaphragm, whereas the force has an indirect relation with the strain and depends on the material features. Then, the possibility of simultaneous estimation of force and displacement was investigated, where the linear relation of both parameters (displacement and force) with the wavelength shift and the optical power were obtained in a limited range of displacement and force. In this range, root mean squared errors of 0.37 N and 0.05 mm were obtained for force and displacement, respectively. In addition, the force variation with a step displacement input also shows the possibility of using the proposed FBG device for the characterization of the materials' viscoelastic features such as phase delay, creep, and stress relaxation, which can be employed for in situ characterization of different viscoelastic materials.
本文介绍了一种埋入式光纤布拉格光栅（FBG）传感器的力和位移分析。第一步，通过有限元方法进行数值分析，考虑线性弹性材料，在这种情况下，光纤中的应变随位移和力（或压力）呈线性变化。第二步，采用两种方法进行实验分析：（i）控制施加在埋入式FBG上的位移（同时测量力）。（ii）控制施加在传感器上的力（同时测量位移）。结果表明，施加位移和力后，反射光功率发生变化，波长发生偏移。比较位移和力时，波长偏移和光功率的灵敏度不同（且不成比例）。然而，在分析波长偏移随位移的变化时，获得了较高的相关性，决定系数（R）为0.998，这表明光纤中的应变传递与膜片中的应变直接相关，而力与应变有间接关系，且取决于材料特性。然后，研究了同时估计力和位移的可能性，在有限的位移和力范围内，获得了这两个参数（位移和力）与波长偏移和光功率的线性关系。在此范围内，力和位移的均方根误差分别为0.37 N和0.05 mm。此外，阶跃位移输入下的力变化还表明，所提出的FBG装置可用于表征材料的粘弹性特性（如相位延迟、蠕变和应力松弛），可用于原位表征不同的粘弹性材料。
