Analysis And Identification On The Suspension Parameters Of The Multiphase Bearingless PM Motor With Single Set Of Windings

The multiphase bearingless motor (MBLM) with single set of windings is the multi-disciplinary product of multiphase machine and bearingless motor. It could not only rotate without the support of bearing, but also has many advantages of multiphase motor. The suspension parameters, including the torque inductance, suspension inductance, and mutual-inductance coefficient, have important influence for the bearingless motor. The caculation and indentification of the suspension parameters are the main content in the paper. The characteristics of the multiphase half-coiled winding used in the multiphase bearingless motor are analyzed in detail, including the winding function, MMF, suspension parameters and suspension force. The influence of the motor parameters on the suspension parameters are researched in detail. The identification of the suspension parameters with the Model Reference Adaptive Method (MRAM) is simulated, and its pole assignment is optimized. The experimental platform for the multiphase bearingless motor is developed, on which the experiments on the suspension parameter identification are performed. The main work of this dissertation includes:Firstly, the MMF distribution of the the multiphase whole-coiled and half-coiled winding with different phase numbers are analyzed in detail to acquire their characteristics and scope of application. The characteristics of generating odd and even times harmonics of the multiphase half-coiled winding can be applied in the bearing motor. The inductance matrixes of the PM-type bearingless motor with salient and cylindrical rotor are deduced with the Modified Winding Function Method, and they are verified by FEM. The expression of the radial force of the multiphase bearingless motor is deduced by the Virtual Displacement Method, and the difference of the suspension field and radial force of the former two kinds of bearingless motor are researched by the FEM. Especially, the affection on the suspension characteristic of the armature reaction is analyzed. Finally, the mathmetical model with rotor eccentricity consideration is established, including the voltage function, torque function and rotor motion function.Secondly, the bearingless motor should satisfy the requirement of P2=P1±1. The analytical model of inductances and suspension force of the MBLM with2-pole torque field and4-pole suspension field (2-4type) and the MBLM with4-pole torque field and2-pole suspension field (4-2type) are deduced in the paper, which is fit for the MBLM with the salient-pole rotor and the cylindrical rotor and verified by the FEM. The characteristics of the half-coiled winding with2π/m-and π/m-phase-belt are analyzed, including the analysis and comparation of the airgap magnetic flux density and suspension force for the five-and six-phase bearingless motor by FEM. The influence to suspension paramenters of the pole-arc coefficients, airgap length and the permanent magnet thickness are analyzed, which is quantified by the variation of airgap magnetic flux density, torque inductance, suspension inductance, mutual-inductance coefficients, flux linkage and suspension force. Finally, the influence on the suspension parameters is synthesized by the three motor parameters.Thirdly, the accurate mathematical model and motor parameters play the key role in the PM bearingless motor control. The Model Reference Adaptive Method (MRAS) is used for the identification of torque inductance, suspension inductance, and mutual-inductance coefficient. Althought the rotor eccentricity has to be deleted in the MRAS for the inductance identification, the Simulink results prove that the rotor eccentricity don’t have the influence on parameter identification. Since the pole assignment can accelerate the convergence speed of the suspension parameters, the feedback matrixes for each suspension parameters are designed and used in the Simulink simulations, whose results verify the validity of the pole assignment.Finally, the experimental platform is established for the bearingless motor with any phase number. The platform concludes the major loop, the isolated driver circuit, the signal sample circuit and the fault secure circuit. The digital signal processor TMS320F28335and field programmable gate array EP2C8Q208C8are the core chips, which realize the control algorithm and the production of PWM. They communicate with each other with DMA and LPM_RAM. In the platform, the suspension parameters are measured off line, which verify the correction of the analysis results and act as the reference value for the parameters identification. Finally, the experiments of the parameters identification are performed with the proposed algorithm to verify its validity under the stable operation and acceleration respectively.