Miniaturization and Performance Enhancement of the Magnetically Levitated Centrifugal Pump as an Implantable Ventricular Assist Device

本研究的目的是提高磁悬浮叶轮离心泵作为左心室辅助装置的性能和生物相容性，最终研制出植入式心室辅助系统，主要研究结果如下：1.悬浮控制电路的小型化和稳定性的提高设计了控制转子（叶轮）径向悬浮和旋转的电子电路，以实现在紧凑型离心泵中。通过数值模拟得到了定子内、外径和匝数的优化值。根据分析结果设计了试验台泵，实现了作为左心室辅助装置的充分的流体动力学性能.采用零功率控制方法，并将其应用到本悬浮系统中。零功率系统设置为 ...更多信息 将控制目标定位在径向流体力最小的位置上，从而节省了悬浮系统所需的电力。建立了电磁元件的数学模型，得到了永磁体厚度、定子直径和线圈匝数的优化设计。最后，定子的直径被设置为55毫米，我们成功地将总电力减少到11瓦.在定子和转子之间的差距处，血液通道的最小间隙为0.5 mm。进行了溶血试验，以确认对红细胞施加的机械损伤在临床应用的可耐受范围内。结果表明，在5.0 L/min的流速下，在100 mmHg的压头下，该泵引起的机械性血液损伤与市售泵（Medtronic BP-80）的机械性血液损伤相容。并对泵流量的估算方法进行了研究。作为零功率控制的结果，叶轮位置在每个流动条件下移动到平衡位置。我们发现叶轮离几何中心的位移与流量成正比。这一基本发现可以发展成不需要任何流量计的流量测量系统。少

The purpose of the present study is enhancement of the performances and the biocompatibility of the centrifugal pump with magnetically levitated impeller as a left ventricular assist device, with the final goal of development of an implantable ventricular assist system.The primary results obtained through this study are as follows;1. Miniaturization and Stability Enhancement of the Levitation Controlling CircuitThe electronic circuits which control both radial levitation and rotation of the rotor (impeller) were designed to be implemented in the compact centrifugal pump. Numerical Simulations were carried out to obtain the optimized values of the inner/outer diameters of the stator, and the number of turns. The test rig pump was designed based on the analyses results, and the sufficient hydrodynamic performances were realized as a left ventricular assist device.2. The zero-power control method was employed and implemented into the present levitation system. The zero-power system sets t … More he control target onto the position where the radial fluid forces are minimized, and consequently save the electric power required to the levitation system. We built the numerical modeling of the electromagnetic components and then obtained the optimized thickness of the permanent magnets, diameter of the stator, and the number of turns of electric coils. Finally the diameter of the stator was set to 55 mm and we have succeeded in reducing the total electric power to 11 watts.3. The smallest clearance of the blood passage was 0.5 mm at the gap between the stator and the rotor. The hemolysis tesing was carried out to confirm the mechanical damage exerted to the red blood cells are within tolerable range toward clinical application. The results showed that the mechanical blood damage caused by the pump are compatible to that by the commercially available pump (Medtronic BP-80) at the flow rate of 5.0 L/min against the pressure head of 100 mmHg.4. The method of estimating the flow rate of the pump are also investigated. As the result of the zero-power control, the impeller positions shift to the balanced position on each flow condition. We have found the displacement of the impeller from the geometrical center are proportional to the flow rate. This basic founding can be developed into the flow rate measurement system which does not require any flow meter in the system. Less