Design And Characterization Of Active Control Type Magnetic Levitation Bearing For Artificial Kidney Pump

At present,more than 2 million patients with kidney disease worldwide are receiving hemodialysis.The equipment used in hemodialysis treatment is large,the system is complex,and the treatment time is long and the frequency is high.Therefore,this treatment method cannot guarantee the quality of life of patients.Therefore,the development and use of small,continuous and implantable centrifugal pumps instead of traditional hemodialysis machines can improve the quality of life of patients to a certain extent.In the existing centrifugal pump,the impeller is supported by a rolling bearing.The wear between the bearing and the seal will reduce the durability of the bearing,and the high risk of hemolysis and thrombosis caused by the shear stress caused by the contact between the bearing and the rotating parts.This paper will use the non-contact characteristics of magnetic levitation to develop a single degree of freedom controllable magnetic bearing for small centrifugal pumps.Firstly,the structure of the magnetic levitation bearing system is designed and its characteristics are analyzed according to the functional requirements of the magnetic levitation centrifugal separation artificial kidney pump.In order to realize the stable suspension of the rotor in the magnetic levitation bearing system,the radial permanent magnet bearing and the axial electromagnetic-permanent magnet hybrid bearing of the magnetic levitation bearing system were modeled and simulated for this purpose,and their mechanical characteristics were analyzed;the simulation analysis and experimental verification of the overall magnetic levitation bearing system were also carried out,and their results showed that the rotor generated a maximum reply force of50 N in radial motion,the control force of axial motion was maximum 100 N,the radial displacement stiffness coefficient is 47.432N/mm,and the axial current stiffness coefficient is 0.144N/AT,which analyzes the stiffness characteristics of the magnetic levitation bearing system.The dimensions of the prototype of the magnetic levitation bearing system designed in this thesis are 90 mm in diameter,120 mm in height and 1.51 kg in mass.the height of the rotor is 94 mm,the maximum diameter is66 mm and the mass is 0.37 kg.Then,the pole configuration is applied to the control of magnetic levitation bearing by studying the control system of magnetic levitation bearing,and the controller of magnetic levitation bearing is designed according to the principle of differential control.To verify the superiority of the magnetic levitation bearing controller,simulation analysis is performed using Matlab/Simulink.Among them,the step response simulation,the response speed and stability of the maglev bearing system are analyzed;the sinusoidal following simulation,the following characteristics of the maglev bearing system are analyzed;the anti-disturbance simulation,the anti-disturbance characteristics of the maglev bearing system are analyzed.Finally,in order to verify the dynamic characteristics of the magnetic bearing system,the experimental platform of the magnetic bearing is designed and built to verify the magnetic bearing system.Among them,the rotor floating experiment verifies the suspension characteristics of the rotor of the magnetic bearing system,the dynamic characteristics of the magnetic bearing system are verified by the step response experiment,sine follow experiment and anti-disturbance experiment.The experimental results show that the response time of the rotor floating of the magnetic bearing system is 0.0025 s,the adjustment time is 0.07 s,the amplitude in the axial Z direction after stabilization is 3μm,and the coil peak current required for the rotor floating from the axial displacement of 0.3mm is 2.5A,which verifies the responsiveness and stability of the magnetic bearing system.