Research On Electromagnetic Characteristics And Parameters Optimization Of The Toroidal Coil Type EPS Torque Sensor

As the "sense organ" of automobile,sensor is the information source of automobile electronic control system.The progress of sensor technology has greatly improved vehicle safety and fuel economy.Electric power steering(EPS)system is in line with the development direction of energy saving,high efficiency and miniaturization of automobiles,and is an essential key component in current and future automobiles.The torque sensor designed based on the principle of electromagnetic induction has high measurement accuracy,no temperature compensation,good electromagnetic compatibility and excellent environmental adaptability.It is widely used in the automotive industry and is a research hotspot in the field of engineering applications.Torque sensor is the core component of EPS system,which has high requirements on measurement accuracy,electromagnetic compatibility,environmental adaptability and volume.At present,the research of electromagnetic induction torque sensor still stays in the planar structure.The planar sensor has the following disadvantages: First,the planar winding mode leads to the structural problem of relatively large sensor volume;The second is the technical problem of how to design the optimal winding mode;The third is the problem of linearization algorithm with lower linearity.In order to solve the above problems,based on the principle of electromagnetic induction,this paper uses the structural characteristics of planar torque sensor for reference to design a toroidal torque sensor used in EPS system.The magnetic circuit analysis method and electromagnetic field analysis method are used to study the output voltage waveform of toroidal torque sensor and the structural factors affecting its output signal,reduce the linearity of toroidal torque sensor,and realize the miniaturization of sensor structure,With high precision and low linearity,it is the development and extension of traditional electromagnetic induction measurement technology.The structure of the toroidal torque sensor is designed,and the key factors affecting the output of the toroidal torque sensor are explored based on the magnetic circuit analysis method.According to the principle of electromagnetic induction,in order to solve the problem of large winding volume of planar torque sensor structure,the spiral excitation coil is designed based on the Flexible printed circuit(FPC)technology to realize the axial layout of the sensor along the torque;Considering the complexity of the output signal source of the sensor,the differential sine structure receiving coil is designed to improve the sine fitting of the induced voltage of the receiving coil,and realize the decoupling of the excitation magnetic field and the eddy current magnetic field;The periodic magnetic flux region method is proposed.Using the distribution characteristics of the excitation magnetic flux of the toroidal coil torque sensor,the main magnetic flux region and the leakage magnetic flux region are divided,the equivalent magnetic circuit model is established,and the model output expression is derived.According to the model output expression,the influence of structural parameters on the output signal of the toroidal coil torque sensor is studied.Based on the ring coil structure of the sensor,the electromagnetic distribution characteristics of the sensor are studied.According to the MAXWELL equations,the mathematical model of magnetic induction intensity of the excitation coil is established,and the distribution characteristics of the excitation magnetic field are studied;The rotor eddy current is calculated by Truncated region eigenfunction expansion(TREE),and the rotor eddy current distribution characteristics are studied;According to the formula of magnetic induction intensity and the position relationship between the components of the toroidal coil torque sensor,combined with the relationship between the coupling area of the rotor and the receiving coil,the analytical expression of the induced voltage of the receiving coil is established.Through the finite element simulation software Ansys Maxwell,the distribution characteristics of magnetic lines of force and eddy current are studied,and the characteristics of space magnetic field change and the induced voltage of receiving coil in the case of no rotor and with rotor are compared;The static and dynamic simulations are carried out respectively to study the variation law of the output voltage of the receiving coil,and analyze the influence of the rotor crosstalk on the induced voltage of the receiving coil.A three-phase signal transformation linearization calculation model is constructed and a particle swarm optimization(PSO)algorithm with adaptive adjustment of inertia weight is proposed to reduce the linear error and absolute error of the sensor.The output signal of the toroidal coil torque sensor is three-phase sine curve.The linear function relationship between the induced voltage and the angle is established by the transformation linearization method,which theoretically reduces the linear error of the sensor;The Plackett Burman test was used to screen out the key factors affecting the linear error and absolute error of the toroidal torque sensor;For the double objective optimization problem,according to the effect value of Plackett Burman test,different weight coefficients are introduced to reconstruct the objective function;Aiming at the problem that the PSO algorithm needs to repeat the physical modeling for optimizing the structural parameters of the sensor,the electromagnetic model of the toroidal coil torque sensor is established based on Simulink with reference to the transformer modeling method,which is used as the PSO algorithm tool to improve the optimization efficiency;Aiming at the slow convergence speed of PSO algorithm with decreasing inertia weight,a PSO algorithm with adaptive adjustment of inertia weight is proposed to improve the convergence speed of the algorithm.The prototype of the toroidal coil torque sensor is trial manufactured,and the performance parameters of the sensor are tested.The ring coil torque sensor adopts the differential output mode,and the prototype of the sensor is trial produced;With the torsion bar of EPS string as the measurement target,the sensor experimental platform was built to complete the sensor calibration.Carry out accuracy and linearity experiments at zero speed and rotating state,verify the function of the ring coil torque sensor,and test the performance parameters of the sensor.