Study On Clearance-rubbing Dynamic Behavior Of Magnetic-liquid Double Bearing

As a new type of suspension bearing,Magnetic-Liquid Double Suspension Bearing(MLDSB)is mainly supported by electromagnetic suspension and supplemented by hydrostatic supporting.Its bearing capacity and stiffness can be greatly improved.Because of the small liquid film thickness(it is smaller 10 times than air gap),the eccentricity,crack,bending of the rotor,and the assembly error,it is easy to cause the clearance-rubbing fault and the magnetic pole group coating-wear phenomenon between the rotor and stator,the operating stability can be reduced.Therefore,this paper intends to study the dynamic behavior of the 2-DOF supporting system of the MLDSB under the states of the clearance-rubbing and the coating-wear,and reveal its operation law and control strategy.The main research contents of this paper are as follows:(1)In view of the problems of the clearance-rubbing and the coating-wear in the supporting system of MLDSB is raised.Based on Maxwell’s electromagnetic suspension theory and hydrostatic suspension theory,the incremental expressions of the electromagnetic suspension force and hydrostatic suspension force of the MLDSB are derived,and the 2-DOF mathematical model is established.(2)According to the linear rubbing force expression,the clearance-rubbing dynamic equation of 2-DOF system of MLDSB is established and the fourth order Runge-Kutta method was used to simulate the effects of rotor eccentricity ratio,rotating speed and the compound plane of rotor eccentricity ratio and rotating speed on the clearance-rubbing behavior of rotor displacement.(3)In view of the coating-wear situation of magnetic pole group,a new soft sensing method for the wear of magnetic pole group is proposed,the supporting performance of the MLDSB was analyzed,the clearance-rubbing dynamic equation of 2-DOF system of MLDSB is established under different wear condition of magnetic pole group.Then,the influence law of wear state on rotor displacement and its rubbing behavior is simulated,and the electromagnetic control strategy which can restore the supporting performance of the bearing rotor system is explored.(4)According to the linear rubbing force expression,the dimensionless differential equation of the rubbing rotor with 4-DOF system is established.Then,the influences of rotating speed and eccentricity ratio on the displacement of rotor bearing and rotor turn table are simulated,and the compound plane of bifurcation and rubbing between rotor bearing and rotor turn table is studied.(5)The proposed soft sensor method is validated by experiments and the wear condition of the coating of the magnetic pole group was qualitatively studied by three groups of magnetic sleeve with different outer diameters.