Rotor Dynamic Analysis And Structural Optimization Of Surface Mount Electro-hydraulic Coupler Without Air Gap

Mechatronics-electro-hydraulic power coupling system can realize the arbitrary mutual conversion and coupling of mechanical energy,electric energy and hydraulic energy.It overcomes the disadvantages such as large volume,loose structure,low energy conversion efficiency and poor adaptability of power devices such as generator,motor,swashplate hydraulic pump or hydraulic motor and combination system of motor and hydraulic pump.In order to make it more compact,a new structure of non-air gap surface-mounted permanent magnet synchronous mechatronics-electro-hydraulic power coupling system is proposed.The force analysis and structure optimization of its motor part are carried out to verify the feasibility of this new structure,and provide theoretical basis for its structure improvement.The electromagnetic field characteristics of the motor are studied.The electromagnetic field analysis models of traditional and non-air gap surface-mounted permanent magnet synchronous motor are established,the finite element simulation analyses are carried out.Through comparison,the structure without air gap makes the magnetic density of the motor become higher,the value of the induced voltage increase,meanwhile,the cog torque value and the torque fluctuation value of the motor are reduced,and the operation stability of the motor is improved.The stress field of the rotor is analyzed.The three-layer structure model of the motor rotor and its strength theoretical analytical model are established,and the finite element simulation analysis of the stress field of the rotor of the traditional surface-mounted permanent magnet synchronous motor and the rotor of the non-air gap surface-mounted permanent magnet synchronous motor are carried out respectively.The results show that their forces meet the safety requirements of the rotor strength.The influence of interference and sheath thickness on the rotor stress is studied.The influence of interference on the equivalent stress of rotating shaft,the radial compressive stress of permanent magnet,the tangential compressive stress of permanent magnet,the radial compressive stress of sheath,and the contact stress between sheath and permanent magnet of the rotors of two kinds of motors are consistent.The thickness of sheath has a greater influence on the stress of the rotor of the traditional surface-mounted permanent magnet synchronous motor.The structural parameters of the rotor are optimized based on the response surface method.The interference between sheath and permanent magnet and the thickness of sheath are selected as optimization variables,and the stress of the rotor is selected as optimization goal.The optimal parameter combination scheme was obtained through objective driven optimization.The optimized equivalent stress of rotating shaft,radial compressive stress of permanent magnet,tangential compressive stress of permanent magnet and equivalent stress of sheath are all reduced,the contact stress between sheath and permanent magnet meets the requirement of transferring torque.The dynamic characteristics of rotor system are studied.The dynamic characteristics analysis model of the rotor of surface-mounted mechatronics-electro-hydraulic power coupling system without air gap is established based on the optimized results.The vibration mode,natural frequency,critical speed and Campbell diagram of the rotor system under the bearing rigid support and elastic support are obtained by simulation.The avoidance margin of the critical speed is calculated to be greater than 20%,and the resonance phenomenon would not occur.The influence of bearing stiffness on the critical speed of rotor system is analyzed,with the increase of bearing stiffness,the critical speed of the first two orders of rotor system does not change basically,the critical speed of the third order increases gradually.