Optimization Design And Characteristic Analysis Of Magnetic Bearing And Ball Bearing Double Support Motorized Spindle

To obtain high stiffness,the traditional angular contact ball bearing supports the motorized spindle mainly through increasing the preload,while,increasing the preload limits the speed of the ball bearing and increases the wear between the ball bearing and the spindle.In order to solve this problem,maglev motorized spindle apperred.However,its own low stiffness,magnetic levitating bearing stiffness is completely provided by current,once there is a power outage or out of control,the rotor will fall off and the spindle parts will be damaged.In order to improve the electric spindle rigidity and reduce the wear between the spindle and ball bearing,this paper designs a new type of magnetic bearings,ball bearings,double support motorized spindle.The details are as follows:Firstly,the overall structure of magnetic bearing and ball bearing double-supported motorized spindle was introduced,and the experimental platform of magnetic bearing and ball bearing double-supported motorized spindle was independently designed and built.Finite element simulation software Ansoft was used to simulate and analyze the electromagnetic bearing to verify the maximum electromagnetic force calculated theoretically.The mathematical model of axial preload and inner and outer ring displacement of angular contact ball bearing and 5-d OF dynamic model of magnetic bearing and ball bearing double support motorized spindle were established.Secondly,this paper used the finite element analysis software to study the static stiffness and modal harmonious response characteristics of the magnetic bearing and ball bearing double-supported motorized spindle respectively,and obtained the static stiffness,the first two order natural frequency and vibration mode of the motorized spindle,the natural frequency and vibration of the motorized spindle under the influence of excitation force.In order to further verify the static and dynamic characteristics of the magnetic bearing and ball bearing double-supported motorized spindle,the static stiffness and the first two order natural frequency of the motorized spindle system were obtained by the static stiffness test and the constrained modal test.The results were compared with the simulation results,and analyzed the causes of errors.The natural frequency of magnetic bearing and ball bearing double support motorized spindle is compared with that of non-magnetic bearing motorized spindle.The results show that the new double support motorized spindle can effectively improve the natural frequency of the motorized spindle.In order to improve the dynamic characteristics of motorized spindle,the design of motorized spindle was optimized,and the natural frequency of motorized spindle was greatly improved.Finally,the control characteristics of the new double-supported motorized spindle were studied.PID control was adopted and matlab was used to simulate and analyze the five-degreeof-freedom mathematical model of magnetic bearing-ball bearing,and an experimental prototype was built for experimental verification.By comparing the rotor displacement of the magnetic bearing-ball bearing double support motorized spindle and the traditional ball bearing at the speed of 1000r/min,2000r/min and 3000r/min respectively,the amplitude of the new double support structure is reduced by about 30% at different speeds through the control of the magnetic bearing,which effectively improves the stiffness of the motorized spindle system.The wear of spindle and ball bearing and the rotary center of spindle are reduced,and the service life of ball bearing is prolonged.In the experiment,the air gap of the electromagnetic bearing is 0.15 mm,so that the electromagnetic force of the electromagnetic bearing can be effectively utilized.Through simulation and experiment,the design of the magnetic bearing and ball bearing double support motorized spindle is reasonable.