Design And Control Of A Ring Direct-drive Permanent Magnet Motor

The ring direct-drive permanent magnet motor can drive the load directly and eliminate the transmission error,therefore,it is suitable for CT machine and ball mill.In this paper,the design of the permanent magnet synchronous motor using field-circuit method was introduced.This paper focused on the design of the ring direct-drive permanent magnet motor,the optimization of the cogging torque,the simulation of the vector control system and the experiments of the prototype.Firstly,the structure design of the motor was carried out.According to the principle of permanent magnet synchronous motor and the performance index,the overall scheme was determined.The main dimensions and performance parameters were calculated.RMxprt and 2D modules of Maxwell were applied to conduct the simulation of the motor respectively.Under the 2D module,the performance parameters were obtained under the conditions of no load,rated load and overload.The comparison of these three results proved the feasibility of the design scheme and the main technical parameters of the motor were given.Secondly,to weaken the cogging torque of the motor,Maxwell and Isight were used to optimize the structural parameters.By comparing the simulation waveforms of different air gap layers,the mesh accuracy of each part was determined and the cogging torque was obtained.By scanning the parameters of the motor,the optimum variable range was determined.Maxwell was integrated with Isight and RBF algorithm was used to establish an approximate model to improve the optimization efficiency.The optimization of the cogging torque was optimized based on NLPQL and MIGA respectively.The simulation results showed that the cogging torque was reduced by 59%.Thirdly,to research the vector control system,the mathematical model of the motor based on the dq coordinate system was established.The simulation model of three-closed loop was built in Matlab/Simulink.The simulation results showed that the control effect of speed and position is good.Finally,performance experiments were carried out for the prototype.The results showed that the operation of the prototype is stable under the drive of the inverter and the error between simulations and experiments is only 2.3% under the condition of no load,which proved the effectiveness of the scheme.The vibration displacements at four frequencies were measured and the motor vibration industry standard showed that the vibration grade is at the top level,which verified the effectiveness of the optimization.The speed closed-loop system based on vector control was used to carry out the speed control experiment.The experimental results showed that the speed control performance of the prototype is excellent.