| External rotor switched reluctance motor(ERSRM)has good torque characteristics,high energy density and system efficiency,but the torque ripple of ERSRM is large,which limits its application in the field of electric bicycles.This dissertation takes ERSRM as object to study the causes of its torque ripple,design the asymmetric stator structure,optimize the system parameters and carry out vibration simulation,and a prototype is manufactured and tested.These works have laid a certain foundation for this type motor to be used as the drive motor for electric bicycle.The main research contents and fruits of this dissertation are as follow:(1)Research on ERSRM topology and operation mechanism.An asymmetric stator structure of the combination of single-side pole shoe and stator pole deflection auxiliary tooth is proposed.It is proved by elliptic line arc magnetic field division method that the air gap magnetic permeability in the non-aligned position can be increased by single-side pole shoe on stator tooth.It is shown by equivalent magnetic circuit and linear model analysis that the deflection-assisted tooth on the stator pole enhances the air gap flux and reduces the peak of single-phase torque.(2)Research on preference optimization algorithm.A preference optimization method based on adaptive gradient targets weighted Chi-square distance ranking is given to address the problem that traditional non-dominated genetic algorithms have fewer feasible solutions in specific regions of the non-dominated frontier after a finite number of iterations.The algorithm is guided to produce more feasible solutions in the decision maker’s preference region through a set of adaptive gradient evolutionary objectives co-evolving with the algorithm population.The effectiveness of the preference search of the given method is demonstrated using standard test functions,and the finite element simulation reverse verifies correctness of the algorithm.(3)Parameter optimization design based on joint simulation.A multi-objective optimization method that combines algorithm with finite element software is proposed.Firstly,the design variables with strong correlation with optimization objectives were screened out through sensitivity analysis.The real Pareto solution set was obtained through the joint simulation optimization,which combine the referred optimization method and finite element software through script program.The maximum value of the weighted objective function is calculated,then the final design scheme is determined.The comprehensive performances of the initial motor and the optimized motor are compared and analyzed,and the effectiveness of the proposed optimization design scheme is preliminarily verified.(4)Simulation and analysis of the vibration and noise characteristics of the prototype.The vibration and noise simulation analysis of ERSRM was carried out by coupling Maxwell twodimensional electromagnetic field,Harmonic response field and Sound field.The simulation results show that the peak values of vibration displacement,vibration velocity,vibration acceleration and sound pressure of the optimized motor model are significantly reduced.(5)Manufacture and experimental verification of prototype.The prototype of the ERSRM motor was made according to the basic parameters of the optimized motor scheme.The prototype experiments show that the difference between the no-load current of the prototype and the peak current of the simulated waveform is small,and the torque ripple of the prototype under rated operating conditions is 2.5%.The result verifies the effectiveness of the asymmetric structure in reducing torque pulsation and the effectiveness of the optimized design. |
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