Study On Decoupling Control Of Bearingless Induction Motor Based On Inverse System Method

The self-bearing induction motor,which combines function of induction motor and magnetic bearings,can provide both torque and radial suspension forces.The rotor of the self-bearing induction motor can rotate with no mechanical friction.In recent years,self-bearing motors have been developed for high-speed machine tools, turbo-molecular pumps,compressors,blood pumps and computer disk drives,and have provided realization methods for many special drives.The self-bearing induction motor is a strong-coupled,nonlinear, multi-variable complicated system.This dissertation focuses on the fundamental theory and a decoupling control approach based on inverse system including mathematic models,rotor flux oriented controller, decoupling control of bearingless induction motor based on inverse system method and the digital control syetem design.The detail contents are as follows:Firstly,the principle of radial suspension force is expounded.The mathmatic models of radial suspension forces are deduced,and the state equations of the bearingless induction motor are set up.Secondly,in allusion to the coupling characteristics between the electronmagnet torque and radial suspension forces of bearingless induction motor,the rotor flux oriented control strategy based on torque winding is investigated.Also,the control system and the simulation models of bearingless induction motor are designed.Then,the control syetem is simulated with Matlab/Simulink toolbox.Thirdly,the reversibility of system based on the mechanical equations is discussed.Based on the mathmatic models of the rotor flux oriented control strategy,a method based onα-th order inverse system theory is used to realize dynamic decoupling control in motor system. Cascading theα-th order inverse system with the motor system,a pseudo-linear system is completed.So it is decoupled into three kinds of independent linear subsystems—radial displacement subsystems,speed subsystem and flux subsystem.And then a linear close-loop adjustor is designed to control each of the subsystems.Finally,the control structure based on digital signal processor(DSP) of bearingless induction motor is discussed;the main hardware system is given too.The implementation of torque control system and radial displacement control subsystem based on the principles and the characteristics of bearingless induction motor are designed.