Study On The Design And Control Of Micro Magnetic Suspension Thrust Bearing

The magnetic suspension thrust bearing is a new type of high performance mechatronics bearing which is stabilized and suspended in the air by electromagnetic force.It has many advantages,such as no mechanical friction,no lubrication and high rotational speed,and it is widely used in biomedical field.As the axial positioning device of rotor in biomedical equipment,the magnetic suspension thrust bearing is closely related with the whole medical equipment performance,so it is necessary to develop a kind of magnetic suspension thrust bearing that can meet the requirement of biomedical equipment.In this thesis,a miniature magnetic suspension thrust bearing with a diameter of 33 mm and a thickness of 6 mm is designed on the basis of the theory of direct current attracting suspension.In the axial direction,the magnetic suspension thrust bearing has three degrees of freedom.According to the three points to determine the principle of a plane,the stator with the same circle on three evenly distributed electromagnetic core to ensure the dynamic balance in the rotor end.The mathematic model of this system is established by linearization of electromagnetic force model,transformation of space rotation coordinate system,derivation of differential equations of motion,and the distributed PID simulation is carried out.The simulation results show that the speed will lead to the coupling between two axial degrees of freedom,and the coupling will increase with the higher speed.In order to eliminate the influence of coupling,the cross-feedback control is introduced,and the coupling of the rotor degree of freedom under different attenuation factors and disturbances is analyzed by the reasonable value of the feedback gain.The cross-feedback control can realize two free-degree of decoupling.In order to verify the simulation results,a micro-magnetic suspension thrust bearing system test-bed is designed and built.The mechanical structure of the test-bed consists of rotor,stator,cover plate,pillar,base and sensor protection frame.The control hardware includes controller,acquisition card,sensors and power amplifiers.Based on the software of Matlab/RTW,the real-time windows target method is used to simulate the system.The rotor suspension is realized by repeated adjustment of the parameters.