Research On Control Strategy Of Vertical Two Degree Of Freedom Electromagnetic Bearing

Active magnetic bearing(AMB)is a new type of mechanical and electrical integrated system which uses controllable electromagnetic force to control the suspension of the bearing in the air.Because of its non-contact,non friction,long service life and other characteristics,it has extremely important commercial value,and has a very wide application prospect in various fields of industry.Different from the traditional electromagnetic bearing which usually works in air or vacuum environment,because of the limitation of the working environment of the electromagnetic bearing in this paper,it is necessary to separate the rotor part and the stator part with metal shielding shell,and on this basis,the control strategy of the vertical two freedom electromagnetic bearing is studied.The paper describes the construction and working theory of the isolated rotor type radial two degree of freedom active electromagnetic bearing,establishes its electromagnetic force mathematical model and linearizes it,establishes the transfer function model and its structure block diagram under the single degree of freedom rotor system based on the position and current double closed-loop control,and also derives the two self of the rotor system under the influence of the gyroscopic effect The model is controlled by degree coupling.The concepts of equivalent stiffness and equivalent damping in AMB are put forward,which provide the theoretical basis for the selection of bias current,and the parameter selection principle of PID controller is determined by using the classical control theory.Then it introduces the fuzzy control theory,designs the fuzzy controller of the electromagnetic bearing,and designs the fuzzy PID control model by combining the fuzzy control and PID control.In the Simulink environment,the simulation models of the three are built,and the simulation contents of the ups and downs simulation and the sudden disturbance simulation are compared and analyzed.The simulation shows that the fuzzy PID control has better dynamic and steady performance than the other two control methods.In order to study the decoupling control strategy of the electromagnetic bearing,the theoretical basis of the linear state feedback decoupling is introduced.The state feedback decoupling matrix is designed on the basis of the two degree of freedom coupling model of the rotor.The closed-loop controller of the system is designed by using the selection principle of the previous control parameters,and the decoupling control simulation model under the Simulink environment is built.The results show that the state feedback decoupling control is effective at low speed and high speed.The control system of AMB is designed and developed.The hardware includes power amplifier,controller,driving circuit and so on.Based on the single-phase full bridge circuit,the power amplifier adopts two-level control mode,and the main controller uses TMS320F28335 DSP of TI company as the main control chip.Then,the initialization program,main program,interrupt subprogram and other control software are designed and developed.After the development of the controller,the related experiments are carried out,including the output characteristics of the eddy current sensor,the calibration of the center position,the software Closed-loop test and the current Open-loop test when the DC bus voltage is applied.