| In recent years,with the development of national economy,the demand of industrial automation is higher and higher,and the application of displacement sensor is more and more extensive.It is used to monitor the displacement,angle,length and other physical quantities in the fields of aerospace,shipbuilding,manipulator,semiconductor processing and biomedicine,and has become the key research object of industrial automation.Based on the principle of resistance strain form,the relationship between the strain of the fixed end and the position and torsion of the moving end is revealed.Compared with the traditional displacement sensor,it has the characteristics of high precision,large range,multi degree of freedom measurement,simple mechanism and low cost.In this paper,the elastomer displacement sensor mathematical modeling,finite element simulation,through the comparison of theory and simulation to optimize the sensor strain gauge patch position,material and size,and on this basis to build an experimental platform,design experiments to verify.First of all,through the analysis of the principle of the elastomer sensor,the experimental model of the elastomer displacement sensor with flange is established.Through the analysis of the principle and the establishment of the mathematical model,it is found that whether the displacement in X,Y,Z direction or the torsion around Z axis,the strain relationship is only related to the size of the elastomer.In order to select suitable elastomer materials,this paper analyzes the creep properties,hysteretic properties,damping properties and fracture properties of silicone rubber,natural rubber and polyurethane elastomer respectively,and finally determines that polyurethane is the most suitable for elastomer displacement sensor.Secondly,in order to obtain the constitutive model and parameters of polyurethane elastomer to realize the finite element simulation of sensor,based on GB/ T 528-2009 standard,the stress-strain curve of polyurethane material was obtained through uniaxial tensile test,and the corresponding polyurethane material parameters of Mooney-Rivlin,Ogden,Neo-Hooke and Yeoh constitutive models were fitted.The stress-strain relationship obtained from the experiment is transformed into data for variance calculation by difference extrapolation method.Based on the comprehensive analysis of the trend and variance of each constitutive model fitting curve and the strain range of polyurethane elastomer in the sensor,it is concluded that the most suitable constitutive model for polyurethane elastomer material is Ogden constitutive model with N = 3 and its parameters.Furthermore,the constitutive model and parameters of polyurethane material are imported into the finite element simulation,and the accuracy of N = 3 Ogden constitutive model is verified through the simulation of uniaxial tensile test.The constitutive model and parameters of polyurethane material and 6061 aluminum alloy flange,glue material model are imported into ABAQUS to carry out the finite element simulation of polyurethane elastomer displacement sensor,find out the maximum strain area,and guide the sensor strain gauge placement and method.Through the finite element simulation of the sensor with different adhesive and adhesive layer thickness,elastomer diameter and length,it is concluded that the sensor with higher hardness and bonding strength after curing,and thinner adhesive layer has higher accuracy.The shorter the length and the larger the diameter of the elastomer,the higher the accuracy of the sensor.Finally,the experimental platform is built.Through the design of strain data processing method and the four degree of freedom translation and torsion experiments,the relationship between strain and load corresponding to the calibration point is obtained.The results show that the nonlinearity of four degrees of freedom is less than1%,and the experimental and theoretical errors of four degrees of freedom are less than 10%. |
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