Fault-tolerant strategies for an implantable centrifugal blood pump using a radially controlled magnetic bearing

Evaluation of the hydraulic forces in a magnetically levitated (maglev) centrifugal blood pump is important from the point of view of the magnetic bearing design. Direct measurement is difficult due to the absence of a rotor shaft, and computational fluid dynamic analysis demands considerable computational resource and time. To solve this problem, disturbance force observers were developed, using the radial controlled magnetic bearing of a centrifugal blood pump, to estimate the radial forces on the maglev impeller. In order to design the disturbance observer, the radial dynamic characteristics of a maglev impeller were evaluated under different working conditions. It was observed that the working fluid affects the additional mass and damping, while the rotational speed affects the damping and stiffness of the maglev system. Based on these results, disturbance force observers were designed and implemented. The designed disturbance force observers present a bandwidth of 45 Hz. In non-pulsatile conditions, the magnitude of the estimated radial thrust increases in proportion to the flowrate, and the rotational speed has little effect on the force direction. At 5 l/min against 100 mmHg, the estimated radial thrust is 0.95 N. In pulsatile conditions, this method was capable of estimating the pulsatile radial thrust with good response.

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A cost-effective extracorporeal magnetically-levitated centrifugal blood pump employing a disposable magnet-free impeller

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/0954411911422842 ◽

2011 ◽

Vol 225 (12) ◽

pp. 1149-1157 ◽

Cited By ~ 5

Author(s):

W Hijikata ◽

T Mamiya ◽

T Shinshi ◽

S Takatani

Keyword(s):

Degrees Of Freedom ◽

Low Cost ◽

Cost Effective ◽

Magnetic Bearing ◽

Blood Pump ◽

Total Power ◽

Centrifugal Blood Pump ◽

Total Power Consumption ◽

Pump Head ◽

Rotary Blood Pumps

In the field of rotary blood pumps, contactless support of the impeller by a magnetic bearing has been identified as a promising method to reduce blood damage and enhance durability. The authors developed a two-degrees-of-freedom radial controlled magnetic bearing system without a permanent magnet in the impeller in order that a low-cost disposable pump-head for an extracorporeal centrifugal blood pump could be manufactured more easily. Stable levitation and contactless rotation of the ‘magnet-free’ impeller were realized for a prototype blood-pump that made use of this magnetic bearing. The run-out of the impeller position at between 1000 r/min and 3000 r/min was less than 40 µm in the radial-controlled directions. The total power consumption of the magnetic bearing was less than 1 W at the same rotational speeds. When the pump was operated, a flow rate of 5 l/min against a head pressure of 78.66 kPa was achieved at a rotational speed of 4000 r/min, which is sufficient for extracorporeal circulation support. The proposed technology offers the advantage of low-cost mass production of disposable pump heads.

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TESTING OF A CENTRIFUGAL BLOOD PUMP WITH A HIGH EFFICIENCY HYBRID MAGNETIC BEARING

ASAIO Journal ◽

10.1097/00002480-200203000-00059 ◽

2002 ◽

Vol 48 (2) ◽

pp. 139

Author(s):

D. H. Locke ◽

E. S. Swanson ◽

J. F. Walton ◽

J. P. Willis ◽

H. Heshmat

Keyword(s):

High Efficiency ◽

Magnetic Bearing ◽

Blood Pump ◽

Centrifugal Blood Pump

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A Compact Centrifugal Blood Pump (1st Report) : A2-DOF Controlled Magnetic Bearing with Magnetic Coupling Drive

The proceedings of the JSME annual meeting ◽

10.1299/jsmemecjo.2004.5.0_355 ◽

2004 ◽

Vol 2004.5 (0) ◽

pp. 355-356

Author(s):

Tadahiko SHINSHI ◽

Junichi ASAMA ◽

Hideo HOSHI ◽

Setsuo TAKATANI ◽

Akira SHIMOKOHBE

Keyword(s):

Magnetic Coupling ◽

Magnetic Bearing ◽

Blood Pump ◽

Centrifugal Blood Pump

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Hybrid Magnetic Bearings for a Centrifugal Blood Pump

ASME/STLE 2007 International Joint Tribology Conference, Parts A and B ◽

10.1115/ijtc2007-44199 ◽

2007 ◽

Cited By ~ 1

Author(s):

Zhaohui Ren ◽

Said Jahanmir ◽

Hooshang Heshmat ◽

James Walton

Keyword(s):

Magnetic Bearing ◽

Active Magnetic Bearing ◽

Force Balance ◽

Blood Pump ◽

Axial Position ◽

Circulatory Support ◽

Radial Clearance ◽

Axial Stiffness ◽

Element Analysis ◽

Centrifugal Blood Pump

A hybrid passive/active magnetic bearing system was designed for a rotary centrifugal blood pump being developed for long-term circulatory support for heart failure patients. This system consists of two axially spaced bearing combinations for complete magnetic levitation of the rotor using only a single-axis active control. Each bearing combination comprises a pair of axially oppositely polarized permanent magnet rings on the rotor and a similar pair in the stator housing for both radial support and axial bias flux, and an electromagnetic coil to actively control the rotor axial position. The design permits a relatively large radial clearance between rotor and stator, and provides sufficient radial/axial stiffness, active controllability over the desired axial travel of the rotor. The bearing characteristics were evaluated by electromagnetic finite element analysis. The prototype pump was fabricated and levitated using a PID controller with zero-force balance algorithm to stabilize the rotor in the thrust direction and minimize the power draw. The experimental results confirmed the efficacy of the proposed magnetic bearing design and associated control algorithm.

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Development of Centrifugal Blood Pump with Compact Magnetic Bearing System

Journal of Life Support Engineering ◽

10.5136/lifesupport.16.supplement_97 ◽

2004 ◽

Vol 16 (Supplement) ◽

pp. 97-98

Author(s):

H. Hoshi ◽

T. Yasuda ◽

H. Kataoka ◽

K. Ohuchi ◽

M. Nakamura ◽

...

Keyword(s):

Magnetic Bearing ◽

Blood Pump ◽

Centrifugal Blood Pump ◽

Bearing System

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Magnetically Suspended Rotary Blood Pump (Keynote)

World Tribology Congress III, Volume 2 ◽

10.1115/wtc2005-63681 ◽

2005 ◽

Author(s):

Hooshang Heshmat ◽

James F. Walton ◽

Michael J. Tomaszewski ◽

Said Jahanmir

Keyword(s):

High Reliability ◽

Medical Center ◽

Magnetic Bearing ◽

Operating Conditions ◽

Active Magnetic Bearing ◽

Blood Pump ◽

Rotary Blood Pump ◽

Centrifugal Blood Pump ◽

Pump Rotor ◽

Blood Flows

MiTiHeart™ LVAD is a rotary centrifugal blood pump with a hybrid passive/active magnetic bearing support system. It exhibits low power loss, low vibration, and high reliability under transient operating conditions. Unique features of the design include a simple and direct flow path for both main and washing blood flows, non-contact pump rotor, i.e., no rubbing surfaces, and relatively large clearances between the pump rotor and housing. The first prototype was constructed from medical grade polycarbonate. To reduce the possibility of thrombosis, the internally exposed surfaces were coated with a biocompatible polymer. Hemolysis test results showed a low normalized index of hemolysis of 0.01 mg/dL. An acute animal test was successfully completed at the Hershey Medical Center. During the test, the pump was implanted in a calf and operated in parallel with the heart. Following the acute test a chronic 200-hour implant study was completed. A second prototype was constructed using a titanium alloy for all blood contacting surfaces and incorporating a redundant hydrodynamic thrust bearing. This prototype was successfully evaluated in two chronic implant studies in a calf animal model for a total of 130 hours.

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