Multi-physics Coupling Analysis Of Liquid Suspension Three-DOF Motor

In recent years,with the increasing demands for bionic drive and mechatronics,the spacial movement generated by single unit such as multi-degree-of-freedom(multi-DOF)motors has attracted more and more attention.The traditional multi-DOF motors always adopt mechanical bearing in connection structure,which leads to a more complex structure with lager friction loss and a lower positioning accuracy.The analysis is accomplished in view of a novel based hybrid drive three-degrees-of-freedom motor which innovatively uses the fluid damping structure,where the liquid oil film is injected between the stator and rotor to reduce the friction loss.The liquid film can make the rotor have a suspension movement when the motor rotates.However,most of this kind of motors or actuators usually suffered great stress in the drive force exertion parts when working at rated operation,which may cause insulation damage.When the windings appears in abnormal states such as short circuit,the stress may be 30 times more than that of rated condition causing damage for motor performance.So it is essential to carry out the influence on the motor structure form electromagnetic fore and thermal effect produced by the electromagnetic force.Besides,the liquid film between the stator and rotor will interacts with the motor stator shell and rotor shell,which will affect the shape of the liquid film then deteriorates motor performance and cause unstable operation.Therefore,the analysis of the fluid-structure interaction of the motor is completed.In this work,the electromagnetic field coupling of the motor and the fluid-structure interaction of the oil film are analyzed.Firstly,the working principle and structural parameters of the motor are introduced along with the driving strategy of the motor.The three dimensional model of the motor is established by using MAXWELL 3D software.The magnetic field and air gap magnetic field distribution of the permanent magnet of the motor is calculated by using the finite element method.The analytical method is used to model the air gap magnetic field of the motor,which verifies the correctness of the finite element method.Combined with the classical electromagnetic theory,the electromagnetic structure coupling analysis is carried out.The deformation and stress distribution of the stator pole core are calculated under the condition of energize coil and magnetized permanent magnet.According to the eddy current loss theory,the influence of electromagnetic thermal effect on the structure is analyzed,the distribution of eddy current density in the stator pole core is calculated,and the thermal stress distribution caused by eddy current density is solved.Finally,the principle of the fluid-structure interaction is expounded,and the characteristics and analysis methods of the liquid film are introduced.The fluid structure interaction analysis of the motor is carried out by using the COMSOL finite element analysis software,and the interaction stress distribution among the liquid film,rotor shell and stator shell.The effects of different angular velocities on the stress of the spherical shell are compared.The work has a certain reference value for the optimal design of the motor which also lays the theoretic foundation for further optimization of the motor.