Research On FBG Displacement Sensor With Hyperbolic Flexible Hinge Structure

Slope deformation is an important feature of slope damage,which often causes sliding or collapse damage,causing huge losses to people's lives and property.In order to be able to reveal the degree of slope deformation,the internal mechanism of slope damage and potential deformation trends,and to avoid or reduce geological disasters,it is necessary to safely monitor the displacement of the slope.However,the traditional electrical sensors have shortcomings in anti-lightning interference and real-time reliability,and the output is a weak electrical signal,and the transmission distance is limited.In recent years,with the continuous development of fiber Bragg grating sensing technology,temperature,stress,displacement,pressure and other sensors based on this technology have achieved good engineering due to their anti-electromagnetic interference,easy reuse,networking,and remote monitoring advantages.Application effect.Providing a reliable and stable sensor is the foundation of slope safety monitoring.In this paper,a finite element analysis optimization method is used to design a fiber Bragg grating displacement sensor based on a hyperbolic flexure hinge structure.The main research work of this paper is as follows:1.Aiming at the problems of mechanical friction and low motion sensitivity caused by the cantilever beam as a sensing structure,a hyperbolic flexible hinge structure is designed based on the principle of triangular amplification.Given the ratio of the cut length to the cutting thickness,a finite element model is established to perform finite element numerical analysis on four common flexible hinge structures,and the relationship between the cutting thickness and the tensile flexibility and rotation flexibility is obtained,and the flexibility is further calculated.The relationship between the degree ratio and the structural parameters shows that the hyperbolic flexure hinge is easier to produce axial linear displacement than other hinge structures,which can produce larger amplification gain and higher sensitivity,so the hyperbolic flexure hinge is selected Structure to carry out the design of the displacement sensor.2.Optimize the size parameters of the hyperbolic flexure hinge structure and design the fiber grating displacement sensor.Given the basic parameters,change the ratio of the length of the incision to the thickness of the cut to calculate the output displacement and maximum stress of the hyperbolic flexure hinge structure,and select the geometry of the hyperbolic flexure hinge structure reasonably according to conditions such as amplification performance and allowable safety stress constraints.Size,the structure of the determined size is analyzed by finite element,and the error rate of the final amplification gain and finite element simulation analysis is 3.7%.The hyperbolic flexure hinge structure and optimization based on the structure parameter and compliance ratio are feasible and correct.of.Combining with the particularity of the slope displacement monitoring environment,further design and perfect other parts of the sensor,and develop the sensor.3.Build a sensor test platform and conduct a comprehensive performance test on the sensor.Select photosensitive adhesive and two-point installation method to install fiber Bragg grating elements to ensure the stability of fiber grating demodulation.In order to verify the sensitivity performance of the displacement sensor in actual displacement measurement,first,the sensor is subjected to temperature compensation experiments to eliminate the temperature For the impact on the measurement structure,a fiber grating displacement sensor displacement test platform was further built.The platform includes an AQ-6370 D spectrometer,a broadband light source and a data acquisition card.The displacement performance test experiment was carried out on the displacement sensor.The experimental data analysis results show that the sensor has a sensitivity of 24.45pm/mm and a linearity of 0.53%FS in the range of 0-50 mm,and it has good micro-displacement measurement capabilities;repeatability The error and hysteresis error are 1.1%FS and 0.537%,respectively,which meet the accuracy and long-term stability requirements of slope safety monitoring for displacement and deformation measurement.