“万峰离心泵”径向磁悬浮轴承的改进研究

Research on Improvement of Radial Magnetic Suspension Bearing of“Wanfeng Centrifugal Pump”

目的:“万峰离心泵”采用5自由度磁悬浮转子-叶轮体驱动血液流动,磁悬浮轴承的控制和稳定性需要设计在合理的范围,以减小血泵体积和重量,改善解剖相容性。方法:研制“万峰离心泵”专用的悬浮转子力学测试台。在悬浮力学实验台上对“万峰离心泵”悬浮转子的悬浮状态和各方向受力特性进行定量测试。通过测定悬浮转子轴向位置与轴向受力,轴向位置与径向受力及轴向受力与径向受力的定量关系,建立各自由度受力特性的关系曲线。结果:悬浮转子的径向受力与转子的轴向位置相关。悬浮转子在轴向位置上有一个力学平衡点,在力学平衡点位置悬浮转子个方向受力为0,可以实现5自由度悬浮。但是,这种悬浮状态不稳定,在微小的外力下极易失衡。实现稳定的悬浮需要有电磁力对抗失衡力。失衡力的方向与大小转子的轴向位置相关,径向悬浮力与轴向失衡力呈正相关,减小径向悬浮力可以有效地减小各个位置的轴向失衡力。结论:磁悬浮转子在偏离轴向平衡位置后可以产生失衡力使悬浮失效。采用电磁力来对抗失衡力是保证稳定悬浮的必要措施。电磁力系统的体积重量必须设定在一个合理的范围,适当的减小转子的径向悬浮力可以降低电磁控制冗余设计的重要途经。

Objective:“Wanfeng centrifugal pump”uses 5-DOF magnetic suspension rotor impeller body to drive blood flow.The control and stability of magnetic suspension bearing should be designed in a reasonable range to reduce the volume and weight of blood pump and improve anatomical compatibility.Methods:A special suspended rotor mechanics test bench for Wanfeng centrifugal pump was developed.The suspension state of the suspended rotor of"Wanfeng Centrifugal Pump"and the force characteristics in all directions were measured quantitatively on the suspension mechanics experimental platform.By measuring the quantitative relationship between the axial position and the axial force,the axial position and the radial force,and the axial force and the radial force of the suspended rotor,the relationship curve of the force characteristics of each degree of freedom is established.Results:The radial force of the suspended rotor is related to the axial position of the rotor.The suspended rotor has a mechanical balance point in the axial position,and the force in each direction of the suspended rotor at the mechanical balance point is 0,which can achieve 5 degrees of freedom suspension.However,this suspension state is unstable,and it is easy to be out of balance under small external forces.To achieve stable suspension,electromagnetic force is required to counter the unbalanced force.The direction of unbalance force is related to the axial position of large and small rotors.The radial magnetic levitation force is positively correlated with the axial unbalance force.Reducing radial suspension force can effectively reduce the axial unbalance force at each position.Conclusion:When the magnetic suspension rotor deviates from the axial balance position,the unbalanced force can be generated to make the suspension invalid.It is necessary to use electromagnetic force to counteract unbalanced force to ensure stable suspension.The volume and weight of the electromagnetic force system must be set in a reasonable range.Proper reduction of the radial suspension force of the rotor can reduce the important way of electromagnetic control redundancy design.