Research On Control And Design Of Rotor Optimization Of Bearingless Motor

With the development of science and technology,the requirements of motors are getting higher and higher in various fields.In particular,high-speed,ultra-high speed areas require the motor speed to break the traditional critical speed.The traditional motor due to the existence of bearing,will produce friction,so the critical speed is relatively low.When the speed is relatively high,due to the noise,heat and other defects make the motor speed's increase encountered a bottleneck so it is difficult to have a big upgrade.In order to solve the problem of bearing's friction,some experts invented the flotation-bearing,liquid-bearing motor and active magnetic bearing motor.They have many advantages compared to traditional motors,such as no friction,higher critical speed.However they have some disadvantages,such as high cost,large volume and so on.On the basis of the active magnetic bearing motor,a bearingless motor is proposed.A new set of suspension windings are added to the original torque winding in the motor to break the uniformity of the air gap magnetic field in the original motor so that the Maxwell forces suffered by the rotor can not cancel each other out.Using this non-zero Maxwell force,the rotor can be stably suspended in the stator.On the one hand,due to the rotor can be operated without friction,the critical speed of the motor is greatly increased,and on the other hand,the problem of large size and high cost of the active magnetic bearing motor is solved.Because of the advantages and characteristics of bearingless motors,it have been greatly developed and researched in the past twenty or thirty years.First of all,the article introduces the principle of bearingless motor suspension,then establishes the mathematical model of the two most common motors,bearingless induction motor and bearingless permanent magnet synchronous motor.On this basis,according to the law of electromagnetic induction and the law of inertia,it is proposed to add a set of damping coils to the bearingless permanent magnet synchronous motor.It is inferred that this coils can improve the robustness of the system and establish its complete mathematical model.Using finite element analysis method,builds a model of ordinary motor on Ansoft Maxwell software Rmxprt module.After that,the Maxwell 2D model of bearingless permanent magnet synchronous motor is built and simulated.The analysis results prove the correctness of the basic principle of bearingless motor and it can improve the stability of the motor after increasing the damping coil.Then the two main control methods of the motor are analyzed,the advantages and disadvantages of the two control methods are discussed,and finally the control method of the rotor field oriented control is selected.After that,established the mathematical model of the whole bearingless motor system,analyzed the principle of coordinate transformation,and set up the coordinate transformation simulation model.Finally,the simulation model of bearingless permanent magnet synchronous motor is built in MATLAB.The mathematical parameters of the conventional bearingless permanent magnet synchronous motor and the mathematical model with damping coil are set respectively.The simulation analysis of the bearingless motor with or without damping coil is carried out.The comparison analysis shows that the robustness of the system is enhanced by adding the damping coil,so the theoretical inference and the correctness of the mathematical model are proved.The thesis concludes with the main contents and innovations of the whole article,and describes the research work needed in the article.The development trend and research direction of bearingless motor are prospected.At the same time,this paper also put forward the need for further research and exploration of the content,then planning for the future works.