Research On Static Suspension Control And Dynamics Of Active Magnetic Bearing

Active Magnetic Bearing(AMB)has the advantages of frictionless,low loss,long service life,and controllability.Therefore,it can be widely used in various rotary shaft mechanical devices,such as high-speed motors,flywheel energy storage devices,artificial hearts,compressor centrifuges,aircraft engines,and other occasions.Currently,the research on control strategies for magnetic bearings has entered a new stage with the development of modern control theory.Many advanced control methods applied to magnetic bearing systems have good control effects in theory,but there are significant differences in practical applications.In order to reduce the difference between the actual and theoretical control effects and improve the suspension performance of the magnetic bearing rotor,this paper analyzes the suspension dynamics of the magnetic bearing rotor under static conditions based on the radial 8-pole active magnetic bearing system platform,and improves the control method to make the rotor suspend within the allowable range of the air gap.The main research work of this article is as follows:Firstly,this paper introduces the main components and working principle of the active magnetic bearing system,and theoretically analyzes the dynamic model of the active magnetic bearing system.Aiming at the phenomenon that the magnetic force of the actual active magnetic bearing system is offset due to the manufacturing deviation,the magnetic force calculation formula of the magnetic bearing rotor in the eccentric position is derived by using the equivalent magnetic circuit method and Maxwell integral stress method.Secondly,this paper studies the magnetic bearing suspension control strategy,adopts the incomplete differential PID control strategy,builds the ideal model of the magnetic bearing magnetic system in the simulation software,carries out the magnetic force simulation test in the horizontal and vertical directions,and finally suspends the rotor stably after a short oscillation,which verifies the feasibility of the control strategy.Then,based on the incomplete differential PID control strategy,a static suspension dynamics analysis of the magnetic bearing rotor was performed using the derived eccentric position magnetic force calculation formula.The rotor motion process was divided into three stages: acceleration,deceleration,and fluctuation.The motion behavior characteristics of the rotor in each stage were analyzed and a three-dimensional relationship diagram of the rotor acceleration,speed,and duty ratio was drawn.During the acceleration phase,the rotor moves upward through the upper magnetic traction,and the magnetic force received increases with the reduction of the upper air gap.In order to prevent the rotor from overshooting,it is necessary to control the rotor deceleration.Therefore,a control analysis of the rotor deceleration motion has been conducted.The deceleration motion is divided into two cases: uniform deceleration motion and variable deceleration motion.Through magnetic force calculation,the critical maximum deceleration point position for the rotor to perform uniform deceleration motion upward based on its own gravity is obtained,and it is extended to situations with different duty ratios at the upper end.The relevant three-dimensional relationship curve is drawn.Finally,on the basis of control strategy research and dynamic analysis,this paper conducted experimental prototype testing,including control strategy comparison experiments,control parameter setting experiments,left and right end optimization experiments under magnetic force offset,and static suspension motion control experiments for rotors with different duty ratios.The motion trajectory shows that the rotor is basically suspended within the allowable range of air gap,with good suspension performance achieved,The effectiveness of the method proposed in this paper is verified.