The Analysis And Research On Stiffness And Damping Of Active Magnetic Bearing

As a new type of high-performance mechatronic product,active magnetic bearing,suspends the rotor to the space through controllable electromagnetic force,realizing the non-contact state of the rotor and the bearing.Active magnetic bearing suspension characteristics is one of the key researches in the active magnetic bearing system,especially the stiffness and damping,stiffness and damping characteristics have great influence on the stability,dynamic characteristics and rotation accuracy of active magnetic bearing rotor system.In order to effectively improve the stability of the system,it is very important to make a more detailed research of the stiffness and damping of the bearing.Based on 10 kWh energy storage flywheel active magnetic bearing test prototype,this paper focuses on the stiffness and damping characteristics of active magnetic bearing from theoretical analysis,simulation analysis and experimental analysis.Firstly,the basic structure and working principle of active magnetic bearing rotor system are described,and the mathematical model of the radial single degree of freedom rotor system is established.According to the established model,the relationship between electromagnetic force and the current and gap in the coil is deduced by electromagnetic theory,and the electromagnetic force is linearized near the equilibrium position.Based on the PID control strategy,the single-degree-of-freedom closed-loop control system model of active magnetic bearing is established,and transfer function of the control system is obtained.The stable region of the control parameter is determined by Routh CriterionSecondly,the theoretical analysis of the stiffness and damping is carried out.The electromagnetic force of the bearing rotor under eccentricity is deduced by subsection integral method.The formula of stiffness and damping is derived based on the concept of stiffness and damping,and the influence factors of the stiffness and damping characteristics are analyzed.Based on the PID control strategy,the control effect and anti-interference ability of the control system are simulated and analyzed respectively.Through the nonlinear research of stiffness and damping,the nonlinear relationship between stiffness and damping of the bearing and the control parameters in the stable control parameters is analyzed,and the influence of control parameters on the stiffness and damping characteristics is simulated and analyzed.Finally,the static and dynamic stiffness of the bearing are analyzed by static measurement and dynamic suspension experiment.The experimental measurement of static suspension mainly tests the static performance of radial magnetic bearing,the measurement of dynamic suspension is mainly carried out by testing the rotor with stable suspension after applying the load.The output data of the two test conditions are collected and analyzed,and the stiffness characteristics is analyzed.By comparing the data analysis with theoretical analysis,the final determination of stiffness characteristics basically meets the design requirements of the whole active magnetic bearing rotor system,and also provides a reference for the structure design and control system research of the bearing.