Design And Optimization Of Outer Rotor Direct Drive Permanent Magnet Synchronous Motors In Robots

Direct drive permanent magnet synchronous motors are one of the important equipment of the robot direct drive system,which has the merits of direct load,low loss,high torque density,high control accuracy,etc.An outer rotor direct-drive permanent magnet synchronous motor(ORDDPMSM)in robots is designed,suitable for smart devices processing of parallel robot.The electromagnetic design,combination of poles,characteristic analysis and slots and multi-objective optimization of ORDDPMSM are studied in this paper.The main research results of this paper are as follows.1.The electromagnetic parameters of the ORDDPMSM in robot are preliminarily determined.According to the working characteristics and actual requirements of the motor in robot drive system,the ORDDPMSM with 27 slots and 24 poles in robot is designed.Design process of the motor is analyzed.,and selection principles of main structural parameters and combination of poles and slots are studied.The main electromagnetic parameters of the motor are preliminarily determined.2.The finite element models are established and the performances of ORDDPMSM in different combinations of poles and slots are analyzed.According to the electromagnetic parameters of the motor,the finite element models are established.The no-load air-gap magnetic density distribution is calculated,and the no-load back EMF,harmonic content of back EMF and cogging torque are analyzed.Under the working conditions of rated torque and maximum torque,electromagnetic torque,efficiency,power factor and force-energy index are compared and analyzed.Under different load conditions,the performances of the motor in different combinations of poles and slots are compared and analyzed.The results show that the selection combinations of poles and slots in ORDDPMSM is reasonable,and the various indicators basically meet the design requirements.3.The influence of ORDDPMSM structural parameters on motor performance was analyzed by a single variable method.Structural parameters such as pole arc coefficient,permanent magnet magnetization direction length,air gap length,stator slot opening width and stator yoke thickness which have great influence on motor performance are selected as single variables.The influence of structure parameters on electromagnetic torque,torque fluctuation,efficiency and force-energy index are analyzed,and the influence degree of each structural parameter on the motor performance is obtained,which provides a certain reference value for the multi-objective optimization design of the motor.4.An improved fuzzy field method(IFBTM)is proposed to optimize the multiobjective design of ORDDPMSM.The layered method is used to build a multi-layer fuzzy rule base,so that IFBTM solves the problem that the original fuzzy Taguchi method is not applicable to four or more objective functions in the multi-objective optimization process.The multi-objective optimization design of ORDDPMSM was carried out by using Taguchi method,fuzzy Taguchi method and IFBTM respectively.The combinations of motor structural parameters with the best overall performance are obtained.The finite element models are established and the motor performances before and after optimization are compared and analyzed.The simulation results show that IFBTM has the effectiveness and correctness,which effectively improves the overall performance of the motor.