Multi Physical Field Coupling Analysis And Optimization Design Of Three-degree-of-freedom Motor With Liquid Suspension

The research object of this paper is a kind of liquid suspension permanent magnet three-degree-of-freedom ball motor with elastic slug lubrication.In the motor,the spherical bearing structure is used to realize the direct connection between the output shaft and the load of the motor,and the special lubrication support structure is used to change the traditional mechanical connection mode,at the same time,the possibility of resonance of the stator and rotor is reduced by the lubricating oil film during the operation of the motor.The working system of the motor involves electromagnetic,temperature,fluid and many other fields at the same time.Therefore,it is of great practical significance to explore,analyze and optimize the performance of the motor based on the theory of multi physical field coupling analysis.In this paper,the electric magnetic coupling analysis,the fluid solid coupling analysis,the temperature field calculation and analysis,as well as the modal analysis are carried out for the motor system.In order to solve the problems of wear,oil whirl and rotor slip in the working process of the motor,the optimization design of the motor structure is carried out.The main contents of this paper are as follows:Firstly,the structure and working mechanism of the new three DOF ball motor are introduced.Through the establishment of the three-dimensional model of the motor magnetic field,the distribution of the motor magnetic field and the spatial distribution of the radial electromagnetic force are solved respectively,and the harmonic of the electromagnetic force is decomposed,which provides the theoretical basis and basis for the subsequent analysis of electromagnetic vibration.Moreover,based on the theory of electro-magnetic coupling analysis,the induction magnetic field of different shapes of winding coil is analyzed.Considering the intensity value of the induction magnetic field and the influence on the air gap magnetic field fluctuation,the rectangular coil winding is selected,which provides the theoretical basis for the stable operation of the motor.Secondly,the EHL performance of the motor supporting structure is analyzed,optimized and designed.The calculation model of spherical bearing is established in spherical coordinate system,and the distribution of oil film pressure and oil film thickness on smooth surface is obtained by programming.Based on the fluid structure coupling theory,the static and dynamic performance of spherical bearing are simulated.In addition,combined with the working characteristics of spherical bearings,the effects of oil whirl and rotor slip are analyzed.By coupling the Reynolds equation with the function describing the surface roughness of spherical bearing,the pressure distribution and film thickness distribution of the rough surface are calculated by the finite difference method.In view of a series of problems that may occur in the work of spherical bearing,an optimized structure is proposed,that is,adding spiral groove structure to the inner surface of stator.Through comparative analysis with spherical bearing without spiral groove,it is found that adding spiral groove can improve the work performance of spherical bearing by changing the lubrication mode.Thirdly,aiming at the special rotor structure of liquid suspension three-degree-of-freedom spherical motor,the optimization design scheme of cooling structure of motor with stator shell cooling channel is proposed.A three-dimensional temperature field calculation model is established to calculate the temperature distribution and volume strain after the winding is electrified.By deriving the viscosity temperature formula,the two-way coupling is realized,and the temperature rise distribution of lubricating fluid and the pressure distribution of oil film after the change of oil film viscosity are obtained by programming.The temperature rise cooling process of motor stator and oil film is calculated by the two-way coupling of finite element method,and the cooling effect of different kinds of stator materials is compared,and the conclusion that aluminum material has the best cooling effect is obtained.Finally,the modal analysis and experimental verification of the stator and rotor structure of the motor are carried out.According to the principle of modal analysis,a three-degree-of-freedom vibration model is established to calculate the oil film mode.Through the finite element method,the vibration characteristics of the stator shell structure without spiral groove and with spiral groove are analyzed.The effects of oil whirl and electromagnetic force harmonic on motor vibration are analyzed.Finally,the empirical mode decomposition of the experimental data shows that when the oil film whirls,the forward precession will increase the speed and vibration frequency of the oil film,while the reverse precession will increase the speed of the oil film,and the vibration frequency will decrease and the amplitude will increase.