Research On Model Prediction Control And Speed Sensorless For A Bearingless Induction Motor

With the rapid development of modern social industry,the plan of manufacturing industry of “the industrial 4.0” and “made in China 2025” have been put forward at home and abroad.Then the motor is one of the important power sources of industry.In order to overcome shortcomings of the traditional motor such as mechanical friction,wear and short life,a bearingless induction motor(BIM)has been proposed.The BIM not only has the advantages of no friction and wear,no additional lubricating oil,strong corrosive,long service life,suitable for high speed or ultra-high speed operation,but also has the advantages of simple mechanical structure and uniform air gap.Therefore,BIM is suitable for the difficult maintenance of life science,strong acid corrosion chemical field,and high speed fields,such as turbo molecular pump,flywheel battery,aeronautics and astronautics,etc.Under the support of the General Program of National Natural Science Foundation of China(51475214)and the General Program of the Natural Science Foundation Project of Jiangsu Province(BK20141301),the main contents are as follows: working principle of the BIM,mathematical model establishment,the partial torque and the partial suspension,speed sensorless and digital control.(1)The research background,research status and development of bearingless motors are described.The BIM and its torque part and suspension part control strategy and speed sensorless technology are briefly described.Based on the analysis of the realized structure and the operating mechanism of the BIM,the mathematical model of the BIM is derived,and its model is verified based on the finite element method,and the direct torque control based on BIM is built.(2)To solve the problem of low accuracy of rotor speed identification of the BIM under traditional direct torque control system,the rotor flux observation based on the Super-Twisting(ST)sliding mode algorithm is used as a reference model.Then a speed sensorless system is constructed by using MRAS.The operation of speed sensorless of the BIM is realized.At the same time,the online identification and correction is realized by constructing the stator resistance.(3)In order to solve the problem of large stator flux and electromagnetic torque ripple caused by hysteresis comparator of the BIM under the traditional direct torque control(DTC),the model predictive direct torque control strategy is proposed.According to the observed value of stator current and stator flux,the electromagnetic torque and stator flux are predicted at the next moment.With the constraint between stator flux and torque,the weight coefficient design of multivariable in traditional objective function is eliminated.The effectiveness of the proposed strategy is verified by simulation and analysis.(4)The hardware and software of the BIM digital control system based on TSM320F2812 are designed.The partial torque is modeled by air gap magnetic field directional control,and the levitation force is controlled by decoupling control of force/suspension current.The experimental results show that the digital control system can not only stabilize the suspension,but also has good dynamic and static performance.