Study On Sensing Characteristics Of Strain Sensor Based On Flexible Hinge

Under the background of industrial society,mechanical equipment is very important for industrial development.In the process of service,mechanical equipment is vulnerable to various factors such as external load,stress concentration and fatigue deformation,which lead to structural damage of important parts,resulting in the decrease of the overall stiffness and strength of the structure,and ultimately the failure and destruction of the entire mechanical structure.In order to avoid this situation,strain monitoring of mechanical equipment structure is of great practical significance.However,the existing strain monitoring methods mainly focus on the electrical magnetic sensing technology,which is more vulnerable to electromagnetic interference,and the stability is poor,so it is not easy to use multi-point distributed measurement.Fiber Bragg Grating(FBG)has attracted much attention in the field of strain monitoring because of its small size,no electromagnetic interference,good long-term stability and distributed measurement.In this paper,a new type of sensor with high strain monitoring sensitivity is designed based on fiber Bragg grating(FBG).The sensor is encapsulated on a substrate and combines FBG with flexible hinge bridge micro-displacement structure.In this paper,the sensing characteristics of the sensor are deeply studied,and an experimental platform is set up to verify the sensing characteristics.The force-deformation relationship of flexible hinges is studied.Based on the flexibility matrix method,a computational model for series flexible hinges is proposed.The calculation model is applied to the sensor designed in this paper,and the strain sensing characteristics of the sensor are obtained.The results show that the sensitivity of strain measurement is 12 times higher than that of bare FBG.The strain measurement accuracy and stability of the sensor are far beyond that of bare FBG,which can meet the requirements of strain monitoring of structural deformation in mechanical system.For the theoretical model of the sensor,ANSYS Workbench finite element method is used to verify the error between the theoretical model and the finite element method is only 1%.The flexibility matrix method and finite element method are used to analyze the structural parameters of the sensor,and the influence of the structural parameters of the sensor on the sensitivity multiplier is studied.The results show that the displacement magnification factor can be effectively increased by reducing the radius and the narrowest width of the flexible hinges appropriately for the flexible hinges and by increasing the thickness of the structure and the deflection angle of the rotating rods for the whole structure and the rigid rods.The sensing characteristics of the sensor are studied through various experiments.The experimental results are consistent with the results of theoretical calculation and simulation analysis.The sensitivity,linearity,repeatability,hysteresis and natural frequency of the sensor are obtained.Through the analysis of static and dynamic experimental results,it is proved that the sensor is suitable for real-time strain monitoring and has good engineering application value.