The Technology Research Of Torque Sensing Based On The Equivalent Theory Of The Magnetic Field And Stress

Torque as one of the physical quantities that can reflect the performance of a system,both in the field of automobile manufacturing or in the field of aerospace and rail transport fields are playing an important role.Torque is one of the important indicators of the power output of the rotary machine,and it is also a key factor in verifying whether the mechanical product is qualified.For the drive shaft,the accurate real-time monitoring of the state of the torsion of the drive shaft,the drive shaft can detect potential failures present in working condition.This paper introduces the methods and principles of various torque detection at home and abroad in detail,and based on the theory of magnetomechanical effect,a non-contact torque detection method based on the equivalent theory of the magnetic field and stress is proposed.And in this method,the relationship between the deflection angle of magnetization and the torque is deduced by using the thermodynamic equilibrium relationship in the torsional ferromagnetic shaft,and the deflection angle ? is taken as the new parameter of the characterization torque.The main contents of this paper are as follows:Firstly,the stress distribution of the cross section of the torsional ferromagnetic shaft is analyzed by COMSOL physical field simulation software,and it indicates the reason for not selecting the axial stresses as the torque measurement.Secondly,from the point of view of the Mohr's diagram to explain the pure shear state can be can be described in terms of a pair of tensile and compressive stresses acting at 45° to the axis of the shaft.Finally,the linear relationship between the equivalent stress and the torque is verified by the energy conservation law.Taking the hyperbolic tangent function as the prototype,the different types of hysteresis loops are simulated by matlab.The theory of magnetomechanical effect is introduced and the stress can be equivalent to an external magnetic field is explained.the theoretical formula between magnetization and equivalent stress under weak magnetic field is given.Finally,on the basis of this,a torque detection method based on the equivalent theory of the magnetic field and stress is proposed and the corresponding theoretical formula is deduced.A torque sensing system based on the equivalent theory of the magnetic field and stress is built,which mainly includes the design of mechanical structure of torque sensing system,the design of ferromagnetic shaft and material selection,and the design of torque detection circuit.And then the accuracy of the torque detection circuit was determined,at the same time according to the sensor performance indicators such as linearity,repeatability,etc.carried out a series of torque experiments.It is shown by experimental data that the resolution of the detection circuit is 25.476 mv/?,the sensitivity of the torque sensing system is 28.4mV/Nm,the maximum nonlinearity error is 1.17%FS,the maximum repeatability error is 7.14%,and then analyzes the causes of the experimental error.