Study On The Transmission Characteristics Of The Magnetic-geared Motor

Magnetic-geared double-rotor permanent magnet motor(hereinafter referred to as magnetic-geared motor)is a kind of low speed and high torque direct drive motor,which is composed of permanent magnet brushless DC motor and field modulated magnetic gear.It has the advantages of simple structure,stable operation,high reliability,low energy consumption,few maintenance and so on.Being different with the structure of general direct drive motors,this motor can achieve a low speed and high torque output condition with smaller diameter and less number of poles and coggings.In the field of household appliances,new energy vehicles,industrial automation and robot joint driving,magnetic-geared motors have broad application prospects.Methods of decomposition and synthesis are useful in the analysis of magnetic-geared motor.This motor can be decomposed into a brushless DC motor and a magnetic gear equivalently,and the internal action of them should be analyzed.At the same time,the mutual influence and interaction of them are considered so that they can be integrated into the whole magnetic-geared motor and work as a whole.This thesis focuses on the magnetic-geared motor,and the following work has been done:1.Based on the electromagnetic theory,air gap flux density and operation principle of the field modulated magnetic gear are analyzed.The structure characteristics and operation process of the motor are shown,and magnetic flux distribution of air gaps and operation principle of the motor are studied by using analytical method.2.Establish the finite element model of this motor,and air gap flux density,harmonic components and torque-angle characteristics are analyzed.With theoretical analysis of cogging torque,influence factors can be revealed.Quantitative analysis of the influence of air gap,equivalent width of ferromagnetic pole-pieces,thickness of connecting bridge and permanent magnet materials,on cogging torque,is finished.Using finite element models with same number of slots and different number of poles,the effect of least common multiple on cogging torque is discussed.After establishing a motor model with Halbach permanent magnet array,air gap magnetic density,torque-angle characteristics and cogging torque of motors,with different magnetizing methods,are contrasted.3.This motor can be decomposed into two components.Concerning the assembly of high speed rotor and armature,the phase voltage equation,electromagnetic torque equation and motion equation can be obtained.The double rotor assembly can be simplified,so dynamics equations between two rotors are yielded.4.Closed-loop control system of the motor can be established in MATLAB/Simulink,which contains several modules,such as PI control,inverter,armature-high speed rotor and so on.Differences of control systems between whole closed-loop and semi closed-loop are studied,and responses with sudden load torque,linear load torque and overload in the whole closed-loop system are shown.5.On the basis of theoretical analysis,finite element analysis and dynamic analysis,two prototypes of magnetic-geared motor with different effective lengths are designed and fabricated,and related experiments are carried out.