Korea Artificial Organ Center, Department of Biomedical Engineering, College of Medicine, Korea University, Seoul, Korea.
Artif Organs. 2011 Nov;35(11):1082-94. doi: 10.1111/j.1525-1594.2011.01376.x.
A magnetic bearing system is a crucial component in a third-generation blood pump, particularly when we consider aspects such as system durability and blood compatibility. Many factors such as efficiency, occupying volume, hemodynamic stability in the flow path, mechanical stability, and stiffness need to be considered for the use of a magnetic bearing system in a third-generation blood pump, and a number of studies have been conducted to develop novel magnetic bearing design for better handling of these factors. In this study, we developed and evaluated a new magnetic bearing system having a motor for a new third-generation blood pump. This magnetic bearing system consists of a magnetic levitation compartment and a brushless direct current (BLDC) motor compartment. The active-control degree of freedom is one; this control is used for controlling the levitation in the axial direction. The levitation in the radial direction has a passive magnetic levitation structure. In order to improve the system efficiency, we separated the magnetic circuit for axial levitation by using a magnetic circuit for motor drive. Each magnetic circuit in the bearing system was designed to have a minimum gap by placing mechanical parts, such as the impeller blades, outside the circuit. A custom-designed noncontact gap sensor was used for minimizing the system volume. We fabricated an experimental prototype of the proposed magnetic bearing system and evaluated its performance by a control system using the Matlab xPC Target system. The noncontact gap sensor was an eddy current gap sensor with an outer diameter of 2.38 mm, thickness of 0.88 mm, and resolution of 5 µm. The BLDC motor compartment was designed to have an outer diameter of 20 mm, length of 28.75 mm, and power of 4.5 W. It exhibited a torque of 8.6 mNm at 5000 rpm. The entire bearing system, including the motor and the sensor, had an outer diameter of 22 mm and a length of 97 mm. The prototype exhibited sufficient levitation performance in the stop state and the rotation state with a gap of 0.2 mm between the rotor and the stator. The system had a steady position error of 0.01 µm in the stop state and a position error of 0.02 µm at a rotational speed of 5000 rpm; the current consumption rates were 0.15 A and 0.17 A in the stop state and the rotation state, respectively. In summary, we developed and evaluated a unique magnetic bearing system with an integrated motor. We believe that our design will be an important basis for the further development of the design of an entire third-generation blood pump system.
磁悬浮轴承系统是第三代血泵的关键组成部分，尤其是在考虑系统耐久性和血液相容性等方面时。在第三代血泵中使用磁悬浮轴承系统需要考虑效率、占用体积、流道内血液动力学稳定性、机械稳定性和刚度等诸多因素，并且已经进行了许多研究来开发新型磁悬浮轴承设计以更好地处理这些因素。在这项研究中，我们为新型第三代血泵开发并评估了一种带有电机的新型磁悬浮轴承系统。该磁悬浮轴承系统由磁悬浮腔和无刷直流（BLDC）电机腔组成。主动控制自由度为一个，用于控制轴向悬浮。径向悬浮采用无源磁悬浮结构。为了提高系统效率，我们通过电机驱动的磁路将轴向磁悬浮的磁路分开。通过将叶轮叶片等机械部件放置在磁路外部，使轴承系统中的每个磁路具有最小的间隙。使用定制设计的非接触式间隙传感器来最小化系统体积。我们制造了所提出的磁悬浮轴承系统的实验原型，并使用基于 Matlab xPC Target 系统的控制系统评估其性能。非接触式间隙传感器是一种外径为 2.38 毫米、厚度为 0.88 毫米、分辨率为 5 微米的电涡流间隙传感器。BLDC 电机腔的设计外径为 20 毫米、长度为 28.75 毫米、功率为 4.5 W。它在 5000 rpm 时产生 8.6 mNm 的扭矩。整个轴承系统，包括电机和传感器，外径为 22 毫米，长度为 97 毫米。原型在转子和定子之间间隙为 0.2 毫米的停止状态和旋转状态下表现出足够的悬浮性能。系统在停止状态下具有稳定的位置误差 0.01 微米，在 5000 rpm 的转速下具有 0.02 微米的位置误差；在停止状态和旋转状态下的电流消耗率分别为 0.15 A 和 0.17 A。总之，我们开发并评估了一种具有集成电机的独特磁悬浮轴承系统。我们相信，我们的设计将成为进一步开发整个第三代血泵系统设计的重要基础。
