Research On Structure Design And Signal Processing Circuit For Saw Steering Torque Sensor

With the continuous improvement and innovation in the field of science and technology,safety,environmental protection,energy saving and user-friendly has become the inevitable direction of the development of the automobile.The automobile steering system is an important subsystem of the whole vehicle,its performance directly affects the vehicle's comfort and safety,stability and so on.At present,the main application power steering system of the automotive are the hydraulic,electronic hydraulic and electric Electronic power steering system(EPS),EPS is replacing other types because of its advantages,such as low fuel consumption,high speed,stable steering performance and obvious boosting effect of compact structure,light weight and so on in steering system.Torque sensor is one of the main components of EPS system,and its perceived precision directly affects EPS performance,such as sensitivity,stability,reliability and so on.Based on the theoretical analysis,finite element simulation,and the simulation and experiment of the detection circuit,a kind of surface acoustic wave steering torque sensor is designed.The paper introduces several kinds of sensors on the market in EPS system,also introduces their advantages and disadvantages,development trend.Based on that,introduces the surface acoustic wave technology(Surface Acoustic Wave,SAW)and the current development of the SAW torque sensor.This paper has established the tensor coordinate transformation formula of different piezoelectric substrates of different orientation transform and the constitutive equation under the no bias stress conditions.Based on the script file of MATLAB,write the solution program to get the value of SAW's velocity in a piezoelectric medium.And the result of that consistent with theory result.And based on the research of working principle of torque measurement mechanics theory and SAW sensor,determining the difference structure as basic structure and the material.And through the finite element simulation software COMSOL Multiphysics,establish the mechanical model of torsion and piezoelectric crystal,and gave the final structure by the estimation of the fatigue life of torsion bar,and determining the corresponding wafer thickness after that,establish a linear relationship between the torque and the detection frequency to determine the range of frequency that signal processing circuit to deal with.And the paper uses Multisim software to complete the design of signal oscillation circuit,mixer circuit,low-pass filter circuit and band-pass circuit,shaping circuit and gives the corresponding simulation results,through the design of signal conversion circuit board by Altium designer software,the experiment proves that the circuit could realize the signal conversion.Finally,based on the FPGA technology,by using Quartus II software,using Verilog hardware description language to complete the frequency divider,counter and latch and display modular and the top principle diagram,and get the corresponding simulation results to verify the correctness and rationality of the overall design,completed the experimental work by using 51 single-ship microcomputer and black gold AX301.Count circuit measurement error of less than 1%,so the design of pulse frequency detection can be applied to the research of SAW technology applied torque sensor area.Reducing the cost of the detection circuit and expanding the range of measurements,and the program can directly burn to FPGA chip used in the detection of pulse signals,combining the signal conversion circuit board,the circuit of the research can be used to the SAW signal of differential structure,saving time in detecting the data of SAW for subsequent experiments,and its easy to operation The work of this paper is a part of the research of SAW steering torque sensor,and its works such as theoretical research,structural design and the design of signal detection circuit and so on lay a good foundation for further research work.The work of this paper is a part of the research of SAW steering torque sensor,and its works such as theoretical research,structural design and the design of signal detection circuit and so on lay a good foundation for further research work.