Parameter Design And Vibration-rejection Control On Bearingless Permanent Magnet Synchronous Motor

With the rapid development of science, technology and productivity, high-precision tools, such as precise numerically-controlled machine tools, special robot, IC manufacturing equipments, low carbon energy, high speed aircraft, turbo molecular pumps, centrifuge, are widely applied in engineering, which gives urge requirement of high-speed and super-speed motors. The high-speed motor has some remarkable advantages, such as:(1) It possesses smaller volume, less row material, higher power density, and higher efficiency;(2) It can drive the load directly without the transmission mechanism, which mean less transmission and noise;(3) The rotor of high-speed motor has less rotational inertia and thus has higher-speed dynamic response. For its promising application in special electrical transmission and high-speed direct-drive fields, the high-speed motor has becoming the international research topic in the electrical engineering field. The high-speed motor has vital vibration and shock to bearings, which makes the bearings with severe fever and attrition. This may significantly reduce the service life of bearings. The magnetic bearing can realize the friction-free and abrasion-free operation, which effectively resolves this problem. But, the motor supported by magnetic bearings has longer axial length and lower critical speed, which gives the stubborn ceiling on speed and power restrictions. Besides this, the motor supported by magnetic bearings requires more magnetic bearing units, which makes the motor system more complex and bigger. The bearingless permanent magnet synchronous motor sufficiently combines the advantages of permanent magnet synchronous motor and magnetic bearings, which can produce the radial suspension force and torque simultaneously, and thus it can realize stable operation with bigger power and higher speed. Thus, it has more significant application value in high-speed drive field.Supported by the National High Technology Research and Development Program under grant2007AA04Z213and the National Natural Science Foundation of China under grant60974053, in order to solve technology difficult problems of bearingless permanent magnet synchronous motor applied to the high-speed direct-drive fields, some key theoretical and technological problems such as the mathematical model, the mechanical strength optimal design method of permanent magnet rotor, the construction of the eddy current loss model and winding pole pair number optimization, the adaptive vibration-rejection control, the digital control system design and so on have been researched aiming to realize the high-speed operation of bearingless permanent synchronous motors,. The main researches and the corresponding results are as follows:(1) The Maxwell force and Lorenz force in bearingless permanent magnet synchronous motor was analyzed. The operating principle of bearingless permanent magnet synchronous motors was researched and the conditions of producing controllable radial suspension force in any direction were concluded. The mathematic models of torque and radial suspension force were constructed, considering the rotor eccentricity.(2) The parametric transient finite element optimal design method was put forward. The transient finite element model of bearingless permanent magnet motor was established. The external current sources with adjustable frequency and phase were loaded to the model. The suspension mechanism was verified and EMF, torque and radial suspension force were calculated.(3) The mechanical strength optimal design method of the permanent magnet rotor of bearingless permanent magnet synchronous motors is presented. The mathematic model between the bandage shrink range and the maximum rotating speed was established according to the mechanics of materials and elasticity mechanics theory. For the buried permanent magnet rotor, the equivalent ring method was put forward to calculation the mechanical strength. Finally, based on contact finite element method, the simulation results verify the correctness of the method presented in this paper.(4) The air-gap field and pole-pair-number of windings optimal design strategy was presented. The rotor eddy current loss model of permanent magnet synchronous motor was built. The magnetization modes of permanent magnets were researched and air-gap field were optimized in order to reduce the harmonics. The rotor eddy current losses with different pole-pair-numbers were compared. Finally, based on the transient finite element method with coupled circuits, the simulation results verify the correctness of the method.(5) The adaptive vibration-rejection control method of rotor is presented based on multi-frequency tracking algorithm. The vibration producing principle was analyzed, based on which, the adaptive vibration-rejection control strategy is presented based on the multi-frequency tracking algorithm for bearingless permanent magnet synchronous motors. The multi-frequency tracking algorithm had been deduced and the stability was analyzed. Combing the online identification of rotor vibration frequency and magnetic field orientation, the adaptive vibration-rejection control strategy is presented. The simulation results have shown that the presented method efficiently eliminates the rotor vibration and thus improves the rotating precision.(6) The digital control system of bearingless permanent magnet synchronous motors is designed based on the space voltage vector pulse width modulation to realize the rotor magnetic field-orientated control strategy. The corresponding hardware systems and software systems are designed and the related experiments are conducted. The experiment results have shown that the platform can realize the stable suspension operation.As a conclusion, the summarization of the whole contents is given. The content and emphasis of the further research is also given.