Advanced Biomedical Engineering
Online ISSN : 2187-5219
ISSN-L : 2187-5219
Flow Rate Estimation of a Centrifugal Blood Pump Using the Balance of Control Currents Through the Electromagnets in the Magnetic Bearing
Shuya ShidaToru MasuzawaMasahiro OsaYutaka Suzuki
Author information

2023 Volume 12 Pages 244-252


Implantable ventricular assist devices (iVADs) are commonly used to treat patients with severe heart failure. To ensure safe and reliable operation of iVADs, it is crucial to develop a method for estimating the flow rate (Q) of the centrifugal blood pump used in iVAD without relying on a flowmeter. To address this need, we previously developed a flow rate estimation method (FEM-r) that focuses on the correlation between Q and the levitation position (r) of an impeller suspended by a magnetic bearing in a centrifugal blood pump. The FEM-r maintains a high level of estimation accuracy even when changes in blood viscosity are expected during treatment. This advantageous characteristic distinguishes FEM-r from the conventional method (FEM-IMT) that employs motor current as an estimation index. However, a drawback of FEM-r is the requirement for an additional displacement sensor to measure r. In this study, we propose a solution to this issue by leveraging the correlation between r and the balance of currents (IEMs) flowing through the electromagnets in a magnetic bearing. Thus, we propose an estimation method called FEM-IEM, which utilizes the balance of IEMs as a flow rate estimation index. The balance of IEMs can be obtained using the minimum number of sensors required for iVAD control. First, we developed an estimation equation for FEM-IEM and determined its estimation coefficients by multiple regression analysis based on the data obtained from experiments using a mock loop. The root mean square error (RMSE) and determination coefficient (R2) of the multiple regression analysis were 0.293 L/min and 0.965, respectively. The RMSE between the estimated and measured Q values were 0.284, 0.347, and 1.069 L/min for FEM-IEM, FEM-r, and FEM-IMT, respectively, indicating that the accuracy of FEM-IEM was comparable to that of FEM-r and significantly higher than that of FEM-IMT. Thus, the simple FEM-IEM proposed in this study demonstrates excellent performance for clinical use, allowing accurate flow rate estimation of a centrifugal blood pump without requiring additional position sensor, viscosity measurement, or compensation method, even when the blood viscosity fluctuates.

Content from these authors
© 2023 Japanese Society for Medical and Biological Engineering

Copyright: ©2023 The Author(s). This is an open access article distributed under the terms of the Creative Commons BY 4.0 International (Attribution) License (, which permits the unrestricted distribution, reproduction and use of the article provided the original source and authors are credited.
Previous article Next article