Nonlinear Decoupling And Experiment For Bearingless Induction Motors

Sponsored by the National Natural Science Foundation of China, this dissertation focuses on the fact that the bearingless induction motor is a strong-coupled, nonlinear, multi-variable complicated system. Combined neural networks with inverse system mothod, the neural network inverse system method for bearingless induction motor control is proposed. The influence caused by unmodeling dynamics, parameter variation and load disturbance is decreased evidently, and the bearingless induction motor is linearized and decoupled into four SISO subsystems. Main contents of this dissertation are as follows:Firstly, the principle of radial suspension force is expounded. The mathematics models of radial suspension forces and rotation part of the bearingless induction motor are deduced. In order to realize the decoupling control of torque and radial suspension forces for bearingless induction motor, two control systems based on rotor flux oriented control and air-gap flux oriented control are designed. The two control systems are simulated with Matlab/Simulink toolbox. Simulation results have shown that the static decoupling between torque and radial suspension are achieved basically. According to the simulation results, the rotor flux oriented control and air-gap flux oriented control are compared and analyzed.Secondly, according to the vector control only can realize static decoupling for the bearingless induction motor, a method based on neural network inverse system method has been used successfully in realizing dynamic decoupling control among radial displacement subsystems and torque subsystem. And this method is realized that each subsystems not only have no coupling, but also all subsystems have been linearized, therefore we design the system and attain the ideal performance easily. Then, linear control system techniques are applied to these linearization subsystems to synthesize and simulate.Finally, based on the principle of neural network inverse system method, the digital control system is designed using TMS320LF2407A of TI Corporation, and the flowcharts of each functional block are presented. Based on the prototype of bearingless induction motor, the digital control system is debugged and optimized. The experimental rig of digital control system is set up and is used to validate control strategy.