Bearingless Synchronous Reluctance Motor And Its Control Strategy

As an integration of magnetic bearing technology and traditional motors,a new type of high performance motor called bearingless motor,which possesses a lot of merits including no friction,no wear,no lubrication,high speed,high precision and long life,is considered to have a wide application prospect in the fields such as precision machining,flywheel energy storage,aerospace,and ultra clean product production,etc..On the other hand,owing to the absence of the permanent magnet and exciting winding on the rotor,bearingless synchronous reluctance motor(BSRM)not only retains the advantages mentioned above,but also possesses advantages of simple structure,low cost,low temperature rise,etc..Hence,the BSRM has becoming a research hotspot in power transmission field at home and abroad.In this dissertation,the theory and application researches of the BSRM are carried out,including operation mechanism,mathematical model,electromagnetic analysis,structural optimization,operation control and digital system.A BSRM with new structure is designed with optimized main structure and parameters,and the mathematical models of levitation force and torque subsystem are established.Moreover,the precise feedback linearization decoupling control and the nonlinear second-order sliding mode control strategy are proposed.Last but not least,the BSRM digital control system is designed,and further related experiments are carried out.The main works and achievements of this dissertation can be summarized as follows:(1)The structure and mechanism of traditional synchronous reluctance motors and the generation mechanism of rotor radial levitation force of BSRMs are analyzed to determine the realization scheme of BSRMs with two degrees of freedom.Based on the theory of electromagnetic field,the analytical models of inductance matrix in the static coordinate system and rotating coordinate system of bearingless motors are established respectively.Also,according to the virtual displacement principle,the general mathematical model of the radial levitation force for bearingless motors is designed to deduce the mathematical model of levitation force and torque subsystems of BSRMs.The relevant finite element analysis is carried out,which verifies the correctness of the generation principle and the mathematical model of radial levitation force.(2)In order to resolve the problems of high torque ripple and low output torque in the BSRMs with salient pole rotor,a radial laminated multi-layer flux barrier rotor structure model of BSRMs is put forward,and the main structural parameters such as the layer and thickness of flux barrier and the thickness of the magnetic stripe are optimized.Moreover,the simulation research of levitation force and torque is carried out based on the finite element simulation model.The results show that this new-type BSRM has the advantages of reduced torque ripple and improved output torque when compared with the traditional BSRMS with salient pole rotors.(3)In order to solve the problem of strong coupling between the electromagnetic torque and the radial levitation force of BSRMs,a precision feedback linearization decoupling control strategy of BSRMs is proposed,and the related simulation research is carried out.The mathematical model of BSRMs is transformed into affine nonlinear form.Also,it is proved that the proposed model meets the sufficient and necessary condition of precision feedback linearization by differential geometry theory.Furthermore,the coordinate transformation matrix and state feedback control law are derived in order to realize the precision feedback linearization of BSRMs,hence making the original nonlinear system linearized and decoupled into three independent linear subsystems.The simulation results show that the precision feedback linearization method based on differential geometry can realize the decoupling control between the electromagnetic torque and the radial levitation force of BSRMs with good dynamic and static performance.(4)Considering the influence of uncertain factors such as magnetic saturation,load disturbance,time-varying model parameters,and unmodeled dynamics of BSRMs,a second-order sliding mode control strategy of BSRMs is put forward,and the related simulation research is carried out.The first-order sliding mode control method of speed subsystem and the second-order sliding mode control method of radial displacement subsystem is designed respectively to integrate the nonlinear second-order sliding mode control strategy,which effectively enables the rotor of BSRM to stabilize to the center position and to track to the given speed in a certain time.The simulation results show that the system has fast dynamic response of the motor speed and radial displacement,small overshoot,good tracking ability,and strong robustness when the load changes and the external strong interference occurs.(5)The digital control system of BSRM based on digital signal processor(DSP)TMS320F28335 is built,and the related experimental research is carried out.Based on DSP TMS320F28335,the realization methods and techniques of control modules,power drive modules,parameter detection modules and other function modules are analyzed and studied,and the main hardware and software systems of the digital control system are designed.The experiments of starting,suspension and interference of BSRM are studied.The experimental results verify that the digital control system can realize the stable suspension and operation of BSRM,and the system has satisfactory dynamic and static characteristics.