光纤光栅称重传感器研究

提出一种基于光纤光栅传感技术的称重系统.用特种粘贴剂将布喇格光纤光栅(FBG)粘贴于悬臂梁的自由端,当悬臂梁自由端受力发生微挠度弯曲时,光纤光栅将沿轴向发生形变,通过监测布喇格光纤光栅传感器反射波长漂移测量悬臂梁的微挠度变化.通过分析悬臂梁结构,建立悬臂梁受力与挠度的数学关系,进而测量出加载在悬臂梁自由端应力的数值.通过对系统结构理论分析和实验验证,该装置称重测量范围达到50千克力,测量灵敏度达到0.05千克力,线性拟合度达到0.9997.

Novel Weigh Sensors Based on Fiber Bragg Grating Sensing Technology

The fiber-optic weigh technology is the process to estimate the gross weight of the loads, by measu-ring the loads forces acting on the weigh system with fiber-optic sensing technology. Several fiber-optic weigh system have been reported by prior authors, such as the microbending system, the polarimetric system and the interferometric system. Here, we demonstrate a novel weigh system based on fiber Bragg grating(FBG) sen-sing technology. The sensing principle of FBG is that: when the physical quantity, strain or temperature, monitored by FBG sensors changes, it will cause the reflected wavelength shift of the FBG sensors. This wavelength shift is proportional to the variation of strain or temperature. Compared with other fiber-optic systems, the FBG-based weigh system, which is simpler in design and easier to be integrated, can offer higher accuracy, longer lifetime, and lower costs simultaneously. In the weigh system, the load-supporting structure is very important. In this experiment, a metal cantilever beam was chosen as the elastic body of the weigh system to support the loads. With the theory of the strength of materials, we analyzed the cantilever beam structure and deduced that the force on the free end of the cantilever beam was direct proportion to the deflection variation of the beam. We could use a FBG to detect the deflection of the beam to calculate the force on the free end of the beam. Based on this conclusion, we designed the cantilever beam with special parameters to meet this weigh system. We also used the ANSYS software to calculate the deflection of the designed cantilever beam, and the result showed that this metal cantilever beam was suitable for this weigh system. In this experiment, in order to use the FBG detect the deflection variation of the cantilever beam, one end of the FBG was adhered on the free end of the standard cantilever beam with special gelatin, then the FBG was dragged to make the FBG reflected wavelength shift about 1 nm. Finally, the other end of the FBG was adhered on the motherboard of the weigh system. The bonding coefficient of the gelatin is about 0.93. When the loads were applied to the end of the cantilever beam, it caused the deflection of the beam, and this caused the FBG deformation along the fiber longitudinal direction. A fiber grating interrogator was applied to detect the wavelength shift of FBG. The best resolution of the interrogator is 1 pm, and the scan rate of the interrogator can reach 5 000 Hz. According to monitoring the wavelength shift of the FBG, the deflection variation of the cantilever beam could be obtained. After analyzing the cantilever beam structure, we could derive the mathematic relationship between the loads applied to the end of the beam and the flexivity of the beam, and the weight of the applied loads could be made out by the value of the flexivity. The experiment results demonstrated that the weight range of this system could reached about 50 kg, the sensitivity of this system was about 0.05 kg, and the related linear regression coefficient is 0.999 7.