Structure Optimization Design And Simulation Analysis Of Magnetic Gear With Eccentric Pole

Magnetic gear is a kind of transmission equipment using the magnetic field coupling principle to achieve power transmission.Compared with other traditional transmission equipment,due to its non-contact transmission mode,it has advantages such as no need for lubrication,overload protection,and high torque density.It is usually used in the production environment where reliability requirements are high,maintenance is difficult,low vibration and low noise are needed,such as wind power generation,electric vehicles,marine propulsion and other fields.As a key component of magnetic gear,permanent magnet is of great research value.In this thesis,from the perspective of changing the permanent magnet structure,the magnetic gear structure with eccentric pole is proposed,and the following aspects are studied:(1)Proposing the eccentric pole structure of permanent magnet and analyzing its magnetic field.Firstly,the basic structure and transmission principle of magnetic gear are introduced,and the transmission ratio of magnetic gear under different transmission modes is given.Secondly,the eccentric pole structure of permanent magnet is proposed,the main structural parameters of eccentric pole are defined,and the function expressions of eccentric distance and polar arc coefficient of permanent magnet are derived.Finally,the scalar magnetic potential method is used to obtain the magnetic field distribution when the permanent magnets act alone,and the magnetic field modulation effect after the addition of the ferromagnetic pieces is explained by the analytical method.Thus,the expression of the air gap magnetic density modulated by the ferromagnetic pieces is obtained.(2)Analyzing the effects of eccentric pole structure on the air gap magnetic field,static torque and cogging torque of magnetic gear.The effects on the air gap magnetic field before and after using the eccentric pole are studied by using Ansys EM software,and the air gap magnetic density waveforms are obtained respectively under three different conditions: only the inner rotor permanent magnet acted,the inner rotor permanent magnet acted alone and without ferromagnetic pieces,inner and outer rotor permanent magnets acted together and with ferromagnetic pieces.It is verified that the eccentric pole structure can improve the air gap magnetic density waveform and reduce the harmonic distortion rate.Moreover,both the method of joint action of the inner rotor and the outer rotor and adding ferromagnetic pieces can increase the amplitude of the radial air gap magnetic density of magnetic gear and reduce the harmonic distortion rate.In order to obtain the influence law of different structural parameters on static torque and slot torque,simulations are carried out for magnetic gears with different parameters.(3)Analyzing the effects of different structural parameters of the eccentric pole magnetic gear on torque ripple,and optimizing the structure of the eccentric pole magnetic gear through the response surface method for multi-objective optimization.To evaluate the influence of the eccentric pole per unit volume on torque ripple,the torque ripple factor is introduced.Considering the effects of different structural parameters of the eccentric pole magnetic gear on torque ripple and torque ripple factor of inner and outer rotors of the magnetic gear,a range of values for the structural parameters of the magnetic gear is given from the perspective of optimal design.Combined with the response surface method for multi-objective optimization,the mathematical function models are separately established for the relationships between permanent magnet thickness,permanent magnet eccentricity,permanent magnet pole arc coefficient,ferromagnetic piece pole arc coefficient and torque ripple,torque ripple factor,maximum static torque.The optimal solution with the minimum torque ripple factor when the maximum static torque is as large as possible and the torque ripple is as small as possible is as follows: permanent magnet thickness is 9.85 mm,permanent magnet eccentricity is 32 mm,permanent magnet pole arc coefficient is 0.95,and ferromagnetic piece pole arc coefficient is 0.45.At this time,the maximum static torque of the eccentric pole magnetic gear slightly decreases,but the torque density significantly increases,and both torque ripple and torque ripple factor decrease.(4)Testing the transmission performance of the magnetic gear.The transmission performance tests of the existing magnetic gear experimental prototype are carried out under three different working conditions: no load,constant input speed variable load,and constant load variable input speed.Based on the changes of transmission performances,it is found that the ratio of output speed and input speed is consistent with the transmission ratio.In no-load condition,the no-load loss of magnetic gear increases with the increase of input speed.Furthermore,the transmission efficiency of the magnetic gear increases as the load torque increases,while it decreases as the input speed increases.