Dynamics Of Field Modulated Magnetic Gear Drive System

Mechanical gears can transmit movement and power by using mutual engagementbetween the driving wheel and driven wheel. Due to the direct contact between the teethin the process of transmission, the problems such as friction, wear, vibration and noiseare inevitable, so the lubrication has to be taken into account, which lead to a certainlimited application in the field of higher demand processing environment, such as food,medicine, chemical industry and so on. Magnetic gear transmission system can transmitmovement and power through the interaction of the magnetic coupling between themagnets with no direct contact between rotors, so it overcomes the problems caused bydirect contact of mechanical gears and also has overload protection ability. Therefore,mechanical gears have attracted much attention of domestic and international scholars.In this dissertation, a new concentric magnetic gear based on the mechanism of fieldmodulation is studied. It not only has the advantages of the traditional magnetic gear withparallel shaft, but also has the advantages of high transferable torque, high torque densityand so on. As a new kind of magnetic gear drive manner, studying its magnetic couplingdynamic problems has great significance to the dynamic optimal design of the systematicparameters and the improvement of systematic transmission performance.Magnetic coupling stiffnesses analysis of the field modulated magnetic gear is done.Based on the operating principle of the field modulated magnetic gear, the average statictorque of the inner and outer rotors and the magnetic coupling stiffnesses are deducedthrough the Maxwell stress tensor method, and the results are verified by theelectromagnetic simulation software Ansoft Maxwell. The influence laws of the designparameters (mainly include the axial length, the outer radius of the inner rotor yoke, theremanence etc.) on the torque characteristics and the magnetic coupling stiffnesses areanalyzed, which lay the theoretical foundation for the optimization of structuralparameters of the system.Free vibration analysis of the field modulated magnetic gear drive system is done. The free vibration dynamic model and equations of the field modulated magnetic geardrive system are established. A modal analysis is carried out for the system by analyticalmethod and six types of vibration modes are obtained. The natural frequency and modalshape with different magnetic coupling stiffness are discussed. The formula derivation andthe laws analysis of the natural frequency sensitivities on the design parameters arefinished.Forced vibration analysis of the field modulated magnetic gear drive system is done.The forced vibration equations of the field modulated magnetic gear drive system areestablished. The time and frequency domain response analysis of the system are finishedby canonical transformation and the transfer function method respectively. The systemtime resonance is analyzed in three cases: only consider the inner rotor torque fluctuations;only consider the outer rotor torque fluctuations; consider both inner and outer the rotortorque fluctuations comprehensively. Because the magnetic coupling stiffnesses is smallerthan the mechanical support stiffnesses, the unique forced response phenomenon in themagnetic gear drive system is analyzed. The influence rules of systematic designparameters on the systematic frequency domain response are discussed.Parameter vibration analysis of the field modulated magnetic gear drive system isdone. Taking account of the fluctuations of the magnetic coupling stiffnesses in the fieldmodulated magnetic gear drive system caused by the component eccentricities, theparameter vibration dynamic differential equations are established. The multiscale methodis adopted to deduce the main resonance time domain response formulaes when theexternal excitation frequency is closed to a certain natural frequency of the system and thecombination resonance time domain response formulae when the external excitationfrequency is closed to the combination frequency of a certain natural frequency and themeshing frequency of the system. The dominant frequency and the unique phenomenoncaused by the magnetic coupling stiffnesses fluctuations of the system in the mainresonance and combination resonances are analyzed.The structural design, machining and debugging of the field modulated magnetic gearprototype are carried out, which form the prototype torque characteristics and modalexperiment platform. The torque characteristic experiments and the modal experiment are performed. Through the comparison of the results obtained by experiment and analyticalmethod, the correctness of the theoretical analysis and the rationality of the prototypedesign are proved.