| As an effective treatment for end-stage heart failure and a transitional bridge for transplantation,the blood pumps will focus on implantation of physiological control.Miniature is the key problem for achieving implantation.In this paper a mini motor is put forward based on a permanent magnet motor used in a blood pump developed by the team and the finite element method is used to optimize the electromagnetic performance including reduction of cogging torque,thermal analysis and multi-objective optimization design.Then,the prototype is produced,and both the electromagnetic performance test of the motor and in vitro hydraulic experiments of the blood pump have been conducted after the prototype is manufactured.The main content of this article includes:1.Firstly,the development of blood pumps and the principle and characteristics of the permanent magnet synchronous motor are introduced.Then,considering the physiological requirements including implantation,biocompatibility,and reliability of the blood pump,a 9-slot 6-pole high-speed mini motor used in a mini blood pump is developed based on the motors early developed by the team.2.After analysis of the principle of cogging torque in the motor,magnet pole shifting is used to reduce cogging torque by combining with the principle of slot-pole ratio.The results show that the cogging torque are significantly reduced,the waveform of the back EMF is more sinusoidal after optimization,and the electromagnetic performance such as the output torque ripple is increased.3.A three-dimensional thermal model considering magneto-thermal coupling model is put forward to calculate the temperature field under both steady and transient conditions on the basis of loss analysis in the motor.The results show that in the long-term operation with direct contact with blood,the motor the temperature rise is within a reasonable range,which satisfies the requirement of biocompatibility of the motor.4.Take six motor structure parameters including air gap as optimization parameters variables and taking cogging torque,the back EMF and loss as three optimization target variables,multi-objective optimization design using the response method is used for the optimization of the mini motor.After optimization,the cogging torque ripple decreases,and the back EMF waveform is smooth,and the loss is reduced,indicating that the optimization algorithm can achieve the improvement of electromagnetic performance and loss suppression of the miniature motor.Finally,the corresponding motor structure parameters are determined according to the optimized objectives.5.After developing the performance test platform of the mini motor and the experimental cardiovascular loop system of the blood pump,both the performance experiment and hydraulic experiment of the motor are carried out after the prototype is manufactured.The electromagnetic performance experiments show that the back EMF waveform of the motor under no-load operation is stable and high sinusoidal,in accord with simulated data.The results of hydraulic experiments show that the min motor can drive the impeller of the blood pump at a design rotating speed to produce blood flow that meets the perfusion requirements of the cardiovascular system.This study proves the feasibility of the mini motor in a blood pump. |
