| Since the outbreak of the Coronavirus,Extracorporeal Membrane Oxygenation(ECMO)has received widespread attention as an effective means of saving lives in respiratory failure and critical heart disease.ECMO is a mechanical device capable of extracorporeal circulation consisting of oxygenator,artificial heart pump and auxiliary equipment.Over several generations,the main artificial heart pumps used today are axial flow blood pumps and centrifugal blood pumps.The centrifugal blood pumps adopts the support structure of hydraulic suspension or magnetic suspension without mechanical contact support,which not only eliminates mechanical wear and tear,but also reduce the degree of damage to the blood.Therefore,it becomes the mainstream trend in the development of artificial heart pumps.However,its magnetic drive system still suffers from deficiencies such as oversize and low utilization of permanent magnets,which cannot meet the demand for high-performance magnetic couplings in ECMO.Aiming at the magnetic drive system of ECMO,this paper designs the magnetic drive system with control and monitoring functions.The main work completed is as follows:(1)First,the composition of magnetic drive system is introduced.The working mode of the system is explained according to the structure of each component,and the performance parameters and their calculation methods concerned in practical applications are concluded.Besides,based on the idea of superposition principle,the air gap magnetic field of the magnetic couplings is divided into the outward magnetic field generated by the driven ring and the inward magnetic field generated by the active ring.Referring to the calculation method of air gap magnetic field of permanent magnet motor,the magnetic field generated of them is calculated separately.The air gap magnetic field of magnetic couplings can be obtained by superimposing them.(2)Models of traditional array magnetic couplings are established by using finite element software.First,models of magnetic couplings with plane air gaps are established,including cylindrical and disc magnetic couplings.Their magnetic field distribution and torque performance are simulated,the performance differences between them were concluded.Then,the model of magnetic coupling without plane air gaps is established,and its magnetic field distribution and torque performance are simulated.Finally,the influence of plane air gaps on magnetic couplings performance is analyzed and the applicability of different structures are concluded.(3)The Halbach array magnetic coupling is modelled and simulated using finite element software,and its magnetic field distribution and torque performance are simulated.Besides,the effects of air gap width,permanent magnet thickness,polar logarithm and permanent magnet shape on the torque performance of magnetic couplings are calculated using the Maxwell 2D analysis function.Parameters applicable to the ECMO are selected with dimensional constraints to improve the utilization of permanent magnets and obtain better torque performance.Based on these,the magnetic couplings of ECMO are designed,and a 3D model of magnetic couplings is established and verified by simulation.(4)The control and monitoring system of the magnetic drive system is designed by using a Single-Chip Microcomputer(SCM)and LCD screen,and the test platform of ECMO is established.The monitoring and control module of rotational speed is designed by using SCM and motor driver.The real-time monitoring and over-limit alarm module of flow and pressure is designed by using flow and pressure sensors.Finally,a friendly human-computer interaction interface is established using the programmable LCD screen to realize the functions of visual processing,parameter setting and data storage of speed,pressure and flow parameters.In conclusion,the design goal of monitoring the magnetic drive system is accomplished,and the feasibility of the designed control system is verified through the test platform. |
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