Novel Decoupling Hybrid Magnetic Bearings And Control Strategies

The magnetic bearings are one of the key devices in the high speed rotating electromechanical equipment.It is an effective technical means to improve the safety and reliability of the high speed rotating electromechanical equipment by excellent electromagnetic properties,coupling mechanical characteristics and impulsive disturbance rejection properties.In this dissertation,based on the magnetic bearing systems,the electromagnetic design,coupling mechanical properties and impulsive disturbance rejection control strategy are studied.The repeated demagnetization or magnetization will degrade the performance of the permanent magnet.The low permeability of the permanent magnet will lead to the large power consumption.The decoupled hybrid radial magnetic bearings(DHRMB)are proposed.The repulsion type radial passive magnet bearing(PMB)is placed in the cavity between the stator and the rotor of the homopolar permanent magnet bias radial magnetic bearing(PRMB).The stator and rotor core are used commonly to improve the radial stiffness of the PMB.The performances of combination are superior to the distributed structure.Further,in order to improve coupling mechanical properties,the permanent magnetic bias axial magnetic bearing(PAMB)with smaller outer diameter of the rotor core is proposed.Placing PMB in the cavity between the stator and the rotor of PAMB,the decoupled hybrid axial and radial magnetic bearings(DHARMB)are designed.The mathematical models of two kinds of hybrid magnetic bearing are established by the principle of mirror image and the equivalent magnetic circuit method.Based on radial passive and axial active hybrid magnetic bearing(HMB),the equivalent model of coupling mechanical characteristics is established.Using coplanar characteristics between radial component of electromagnetic force of thrust bearing,radial force of passive bearing and centerline of the shaft,the thrust bearing is equivalent to two semicircular bearings.Then the relationship between stiffness of thrust bearing and coupling force in HMB is expressed clearly.The conditions of the stable suspension in the hybrid magnetic bearing are calculated.The external load stiffness is obtained and confirmed by experiment.Using the methods,assumed that the displacement current constant of the active radial bearing is constant,the conditions of the stable suspension and the external load stiffness in the 5-DOF magnetic bearing system are calculated.Based on the viscoelastic material model,an active viscoelastic control strategy is proposed to suppress the impulsive disturbance.Using the equivalent effect between the model of magnetic bearing with PD controller and the Kelvin model or the standard solid model of elastic damper,compared the Kelvin model,standard solid model,the generalized Kelvin model and standard solid model,it is found that the traditional active controller model and the Maxwell model are independent of each other.When the viscoelastic control law from the Maxwell model is presented in parallel with the traditional active controller model,the active viscoelastic control strategy is proposed.The effect between different viscoelastic control laws,parameters and systems on rejection disturbance were compared by viscoelastic PD,PID and active disturbance rejection controller(ADRC).Further,a switching control strategy is constructed for decreasing long adjustment time in active viscoelastic control.Using the viscoelastic PID control in magnetic bearing system,the experimental results show that the active viscoelastic control strategy is effective in suppressing the impulsive disturbance.Using the DSP and the external control circuit,a 5-DOF magnetic bearing system was set up.The experimental results show that the DHRMB and DHARMB with active viscoelastic control are excellent to suppress the impulsive disturbance.