Design And Analysis Of Low Torque Pulsation Spoke-Type PM Motor With Shaped ASPs

Servo motor has been widely used in numerical control machine tools and robots,as the core component,its positioning accuracy is directly related to the quality of processing production.Among the various servo motors,the spoke-type PM motor can concentrate flux by two adjacent PMs in various PM motors to generate high flux density,and its simple structure has some cost advantages.However,the high air-gap flux density harmonics of conventional spoke-type PM motor leads to high torque pulsation,which in turn reduces the positioning accuracy of the device.In order to reduce the torque pulsation,four rotor shaping methods,namely pulse width modulation(PWM)method,eccentric(ECC)method,inverse cosine(ICS)method and inverse cosine plus third harmonic(ICS+3rd)method,are applied to the conventional spoke-type PM motor.However,the value of torque pulsation is still high and the torque loss is large.Hence,the ASP is introduced into the spoke-type PM motor to increase the degree of freedom of optimization,and then the four shaping methods are extended to the new motor to achieve a reduction in torque pulsation while reducing torque losses.The main contents of the study are as follows:1.A spoke-Type PM motor is designed,including the slot-pole combination,the motor dimension calculation,the stator and the rotor design.In order to reduce torque pulsation,ASPs are added to the outer edge of the rotor as the basis for subsequent optimization.2.By analyzing the air-gap flux density harmonics,the main harmonic orders causing torque pulsation are determined.In order to suppress air-gap flux density harmonics and reduce torque pulsation,the PWM method,ECC method,ICS method and ICS+3rd method are applied to the conventional spoke-type PM motor,and the four methods are modeled and analyzed using FEM.The results show that above four methods can reduce the torque pulsation to different degrees,but the capacity of suppressing the air-gap flux density harmonic order is poor,and the fundamental wave loss is large.3.The effect of ASPs on the main air-gap flux density harmonics is analyzed,and it is determined that ASPs can reduce the harmonics causing the first-order torque pulsation,based on which Stair ASP.ECC ASP,ICS ASP and ICS+3rd ASP are proposed.Among them,the Stair ASP is improved based on the PWM method,which eliminates the rib of the rotor,resulting in lower torque pulsation and less torque loss.The ECC ASP is redesigned the optimization method based on the Stair ASP,and establish the connection between parameters and narrows the optimization range.The ICS ASP solves the problem of high torque loss of the ECC ASP,allowing the shape parameters to be optimized individually to obtain a shape with lower torque pulsation.The ICS+3rd ASP retains the advantages of the ICS ASP,and the third harmonic amplitude can be individually optimized to further reduce torque loss and maintain low torque pulsation.4.The optimal model is selected through FEM,and a prototype is customized.Then the experimental platform is built according to the test needs,and the torque performance of the prototype is tested and compares with the FEM results to verify the effectiveness of the proposed methods.