Magnetic Bearing Structure Optimized Design And Its Flux Decoupling Self-adaptive Control

Active Magnetic Bearing(AMB)is a kind of non-contact bearing supported by magnetic force.Compared with traditional real-contact bearing,magnetic bearing owns lots of advantages.It can operate at no lubrication circumstance and earns more accurate displacement precise.As the result,it not only can support super rotation rate but prolong its service life.What's more,the rotor position can be kept under AMB's control automatically.Attributed to all of these advantages,AMB has been used in fields such as manufacture,aerospace,bioscience and computer.However,the complicated and expensive control system limits its industrialization.In order to enhance the overall performance of control system,modeling should base on the magnetic field distribution analysis.Electromagnetic simulation illustrates that flux coupling exists among the poles,what's more,flux coupling degree differ from geometric parameters and exciting modes.Flux coupling will affect the magnetic force and impact control performance.Hence,started from the geometric structure design,magnetic field distribution affected by geometric parameters was researched,and the magnetic force impacted by magnetic field distribution was analyzed.Based on analyzing results,how to verify the control current to enhance the magnetic force precise was deduced under the different degree of flux coupling.Major works were conducted from three aspects,geometric structure,magnetic field distribution and control schedule.First of all,the multi-objective optimization method and traditional empirical parameter design method was compared.The finite element electromagnetic simulation was conducted among different models with varied multiple optimization goals,and the result shows that different degree of non-ideal flux distribution,flux coupling and leakage,differ from the geometric parameters.The flux coupling among the poles is the dominate component of the non-ideal distributed flux,which finally leads to the control force error.Therefore,how the geometric parameters impact the flux coupling and how the flux coupling will affect the magnetic force error should be researched.In order to analyze questions posed above,firstly,the equivalent magnetic flux model in consideration of flux coupling was established.The flux coupling patterns have been discussed,and according to discussed result,an evaluation index,coupling coefficient ?,was proposed to describe flux coupling degree.On the base of the equivalent magnetic flux model,according to the Boit-Savart law,the magnetic field distribution mathematic model was established.The magnetic field expansion graph was produced,according to which flux coupling affected bygeometry parameters and control current was analyzed.Result shows that varied geometry parameters affect flux coupling in different extents.What's more,the force error caused by flux coupling can be verified by adjusting the control current.The reference dynamic mathematic model of magnetic force error was established taking mechanical coupling and flux coupling into overall consideration.The magnetic force error affected by coupling coefficient,control current and rotor displacement were analyzed separately.Moreover,the verified control current decoupling strategy aiming at eliminating the force error was derived.In order to achieve the self-adaptive control,parameter identification module and parameter correction module were designed to coordinate with the time-varying parameter system,so that the varying parameters in the reference mathematic model could be verified correctly and timely according to the magnetic field distribution state and the rotor displacement,and increase the control performance intrinsically.Through the theoretical analyzing,the prior fuzzy relationship between the verified control current and the magnetic force error was deduced,and the variable domain self-adaptive fuzzy control model was proposed to further enhance the control rapidity,fault tolerance and robustness.The control system simulation model was set up and analyzed.The traditional PID control,the reference self-adaptive decoupling PID control and the variable domain self-adaptive fuzzy control simulation results were compared,and the variable domain self-adaptive fuzzy control shows the best comprehensive control performance.In the end,the experiment was conducted in order to prove the validity of the decoupling control strategy.Moreover,the state levitation test and the impact test testified the superiority control performance of the reference self-adaptive decoupling control.