Research And Design Of Magnetic Bearing Control System With Three-level Power Amplifier

With the development of high-speed motors used in industrial production,magnetic bearings that support high-speed motor rotors have become the hot research topic.Magnetic suspension bearing is a typical representative of mechatronics integrating mechanical structure,power electronics,control engineering,materials science,digital signal processing and many other disciplines.Magnetic bearings can be classified into various categories depending on the source of the magnetic bearing bias magnetic field.This paper mainly studies the single-degree-of-freedom active magnetic suspension bearing and its control system.The details are as follows:The structure of the radial magnetic bearing of the active magnetic suspension bearing and the winding mode of the stator magnetic pole are studied.Based on the analysis of electromagnetic force,the electromagnetic force calculation formula of the magnetic suspension bearing controlled by single-degree-of-freedom differential driving mode is derived.The model and parameters of the electromagnetic bearing are determined.The simplified mathematical model of the displacement sensor and power amplifier is given.In order to realize the single-degree-of-freedom dispersion control of the magnetic bearing,the two-dimensional finite element electromagnetic simulation calculation of the different structures of the radial magnetic bearing stator is carried out by using Ansoft finite element analysis software,and the calculation results of different stator structures are analyzed to determine decoupling structure of radial magnetic bearing.The relationship between the electromagnetic resultant force of the rotor and the rotor displacement is calculated.The analysis shows that the magnetic bearing structure with decoupling design can provide the electromagnetic force to return to the equilibrium position when the rotor disturbance occurs.Therefore,the designed magnetic bearing structure meets the actual requirements.The control method of active magnetic suspension bearing is analyzed.Following the design principle of the magnetic bearing power amplifier,a logic circuit is designed between the PWM generating circuit and the power amplifier driving circuit to implement a three-level control strategy based on the two-level power amplifier circuit.The rationality of the power amplifier is verified by the combination of simulation and experiment.Analysis shows that the designed power amplifier is reasonable and the performance of the power amplifier is good.The amplifier can effectively reduce the current ripple.The simulation determines the displacement outer loop PID control parameters of the magnetic bearing control system.Under the condition of this parameter,the active magnetic suspension bearing rotor was subjected to floating,static suspension and rotation experiments..