Research On Electromechanical Structure Design And Control System Of Active Magnetic Bearing

Magnetic bearing is a typical electromechanical product,which integrates electromagnetism,electrical and electronic technology,control theory,signal processing,mechanics,rotor dynamics.Magnetic bearing gets rid of contact between the rotor and the rotor,it is easy to realize high speed of rotor,and it has the advantages of no friction,no wear,no lubrication and sealing,low cost,low loss,long service life,etc.So it has has a bright prospect in Industrial field of High speed,ultra high speed,vacuum and ultra clean.In this paper,active magnetic bearing(AMB)is taken as research object,and aim at realization precise levitation control of rotor.So this paper study at critical technology of active magnetic bearing,such as analysis of magnetic field,structure of electromechanical,mathematic model,switching power amplifier,digital control system etc,the details as following aspects.Mathematical model of AMB is foundation of rotor levitation,this paper discusses the working principle of active magnetic bearing,magnetic force model of AMB is established through magnetic circuit analysis.The linear range of the electromagnetic force of the magnetic bearing is standardized,influence of external conditions such as magnetic saturation on electromagnetic force is analyzed,accuracy of electromagnetic force in the whole air gap is discussed.On this basis,linear model of the single degree of freedom active magnetic bearing is established under the condition of differential drive control.Single magnetic bearings can only realize suspension of two degree of freedom,but shaft of motor is a rigid rotor,it needs interaction of multiple magnetic bearings.So the model of five degree of freedom(5-DOF)magnetic bearing is established based on the theories of rotor dynamic.The whole design scheme for 5-DOF AMB is offered,the computing method of allowable magnetomotive force,winding design and the maximum bearing capacity are presented,and correctness of the model of the 5-DOF AMB is validated by finite element simulation.Power amplifier is the key component in the drive system of AMB,it affects the effect of control algorithm directly.In this paper,a current controlled switching power amplifier is designed through the analysis of the efficiency,frequency,current response speed,the corresponding speed of electromagnetic force and the ripple of output current.Based on the design of two level PWM switching power amplifier,a three level PWM switching power amplifier is designed,which can improve the response speed of the drive control system.A digital control system based on DSP is Proposed and designed,experimental prototype of AMB is developed,hardware experiment platform is built,experiment results show The correctness of the control method,and effectiveness of the experimental hardware platform is verified...