Vibration Control Strategy For Bearingless Switched Reluctance Motor

Bearingless switched reluctance motor(BSRM) integrates the function of rotation and levitation.It has the advantages of high integration,simple structure,flexible control,fault tolerance and high adaptability.Due to those advantages,the motor has potential application prospect in the high-speed actuation fields. As a special kind of switched reluctance motor, bearingless switched reluctance motor also has the problems of electromagnetic vibration and noise. The technique of self-bearing in switched reluctance motor(SRM) can suppress the vibration and noise by controlling the radial force between the rotor and stator actively.In order to suppress the vibration of dual-winding structure BSRM,the vibration control strategy is investigated in this paper. The main contents are concluded as follow:Firstly, the mathematical models of BSRM according to the virtual displacement and maxwell stress method are deduced,which supplies the basic theories for vibration control strategy. To get the vibration mode and the corresponding natural frequency of stator, the modal analysis of stator is performed by the finite element method(FEM).It laies the foundation for solving the vibration response of stator.Secondly,this paper applies the two step commutation method of switched reluctance motor to BSRM, analyzing the limitation of two step commutation method in the direct application of BSRM.Based on the basic idea of two step commutation of SRM,Vibration control strategy is proposed to reduce the vibration of the motor at the moment of commutation.Aiming at the reduction of the torque in the new control strategy,a compensation control strategy is proposed.Then, aiming at the problem of the low frequency resonance of the devices on the transmission shaft caused by the large torque ripple of the BSRM, the direct torque control strategy of the BSRM is described.The direct torque control strategy takes the torque as the direct control object, which reduces the torque ripple of the motor effectively.This paper analyzes the influence of the direct torque control strategy to the stator vibration characteristics.Finally, due to the abrupt change of the radial force in each phase,that a method which adopts two phase conduction is proposed. The new control strategy reasonably distributes the suspension force and winding current of each phase to change radial force smoothly to restrain the vibration and noise.On the basis of the above thoery research, the simulations are conducted on the platform ofdouble-winding structure BSRM to verify the availability of the proposed methods.