Design Of Measurement Circuit And Research On Nonlinear Problems Of LVDT Linear Displacement Sensor

Linear Variable Differential Transformer(LVDT)displacement sensor is widely used in all walks of life of the national economy because of the characteristics of simple structure,fast signal response speed,strong stability and long service life,and its performance directly determines the detection accuracy of the whole system.The displacement of most LVDT sensors is nonlinear with the measured value,which leads to nonlinear error in the measured data.This error greatly reduces the accuracy of LVDT sensor measurement results.Therefore,it is particularly important to calibrate the nonlinearity of LVDT sensor.The main contents of this paper are as follows:(1)Equivalent circuit analysis of LVDT displacement sensorFirstly,the theoretical basis of LVDT displacement sensor is summarized,including the mechanical structure composition,classification,static characteristics and dynamic characteristics.Secondly,the equivalent circuit of the sensor is deduced and analyzed,and the distribution of the magnetic field is further analyzed.The LVDT mathematical model is established to provide strong support for the design of LVDT line displacement sensor.(2)Structure and measurement circuit design of LVDT displacement sensorAccording to the process route,the structure and circuit design of LVDT sensor are carried out.Firstly,the mechanical structure of each part of the sensor is designed,including the design of excitation winding,armature,secondary coil and the determination of winding turns.Secondly,the measurement circuit is designed.Based on the principle of lock-in amplifier,the dual phase lock-in ampli fier circuit is designed by using AD9833 as excitation generator.(3)Electromagnetic simulation analysis of LVDT displacement sensorAiming at the excitation signal of the designed LVDT linear displacement sensor,the number of turns of the primary and secondary coils and other parameters,the electromagnetic simulation software Ansoft Maxwell is used to model them and simulate the electromagnetic field.Starting with static magnetic field and transient field,the output characteristics of LVDT sensor are further studied.Meanwhile,the factors affecting the performance of LVDT sensor are discussed,and the analysis shows that the nonlinearity of LVDT sensor has great influence on the accuracy of its output.(4)Nonlinear correction and MATLAB simulation of LVDT displacement sensorThe displacement measurement system of LVDT sensor is built and simulated.The relationship between LVDT displacement and output voltage is plotted.Then,BP neural network and ant colony algorithm are used to correct the nonlinear part of LVDT,the optimization algorithm is simulated by MATLAB software,and the experimental results are analyzed and summarized.The results show that the average error percentage of BP neural network and ACO BP neural network are 6.456%and 0.315%respectively,which shows that ACO-BP neural network is feasible to solve the nonlinear problem of LVDT.Based on the relevant theory of LVDT displacement sensor,this paper analyzes its static and dynamic characteristics and equivalent circuit.The structural parameters of each part of LVDT sensor are determined,and the excitation generation circuit based on AD9833 is designed.Moreover,Maxwell software is used to model and analyze the electromagnetic field simulation,and the factors affecting the performance of LVDT sensor are discussed.Furthermore,a scheme of fitting and correcting the nonlinear part of BP neural network optimized by ant colony algorithm is proposed,and MATLAB simulation analysis proves that this scheme can effectively improve the linearity of LVDT.