XIV Brazilian Automatic Control Conference 1 The Streamliner Artificial Heart Brad Paden University...

XIV Brazilian Automatic Control Conference

1

The Streamliner Artificial Heart

Brad PadenUniversity of California, Santa Barbara

& LaunchPoint Technologies LLC


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Outline

LVAD’s for artificial heart assist Background Next generation devices Design & Prototypes

– Actuators– Sensor– Control

Commercialization


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Need for Mechanical Need for Mechanical Circulatory AssistCirculatory Assist

15,000,000 heart disease deaths/yr. 5-10% could be saved with

circulatory assist Several options:

– Transplant (limited supply)– Ventricular assist device– Total artificial heart (not needed in

general)


4

Heart Transplants in the US

2500/yr

2000/yr

1500/yr

1000/yr

500/yr


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Left Ventricular Assist Devices (LVAD) are the Leading Alternative to Transplants


6


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Lumped-element model of thecardiovascular system


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1st Generation LVADs are in use and are

pulsatile


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1st Generation Devices

Increase 2-year survival from 8% to 23% in end-stage heart failure patients*

Issues remain:– Thrombus (clot) formation,– Mechanical reliability.– Energy efficiency.

*Rose et al, “Long-term use of a left ventricular assist device for end-stageheart failure,” The New England Journal of Medicine, Vol 345(20), 2001


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1st Generation (pulsatile)

2nd Generation (rotary)

3rd Generation (maglev)


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Background on 3rd GenerationLVADs

Extracorporeal Prototypes (Olsen and Bramm, 1981; Allaire, Maslen, and Olsen, 1995; Chen et al, 1998)

Implantable devices in animal trials (StreamLiner 1998, TCI/Sulzer 1999, Berlin Heart ?)

Human Trials (Berlin Heart AG, June 16th 2002)


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Utah/UVA Mag-Lev LVAD


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Cleveland Clinic/Mohawk LVADCleveland Clinic/Mohawk LVAD


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LVAD Design Objectives

Avoid mechanical shearing of the blood

6 Liters/min and 100 mmHg High reliability and efficiency

– … hence magnetic bearings low power ~10 g loading


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Shear-Induced Hemolysis:a design constraint

L.B. Leverett et al, “Red Blood Cell Damage by Shear Stress,” Biophysical Journal, Vol. 12, pp. 257-273, 1972.


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1st Streamliner Concept(HemoGlide 1)


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Conical Bearing Prototypea wonderful 8x8, 10-state nonlinear multivariable control

problem. Stabilized using static linear decouplers and and 5 SISO lead-lag controllers.


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•In a divergence-free electric field there are no stable equilibria for charged particles.

•Similarly for ideal permanent magnets in astatic magnetic field.

This is too complicated!Can we just use permanent magnets?

Earnshaw’s Theorem (1842)


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more formally…

Let )( xEqF

, 0 E

, 0 E

, 0x

be an equilibrium point for a charge in the

field F

.

Since 0 E

there exists a real potential such that E

. Hence the

Jacobian qofHessianxd

Fd

and is therefore real sym m etric.

Further, real sym m etric m atrices have real eigenvalues and orthogonal eigenvectors.


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Theorem (Earnshaw): Let 321 ,, be the eigenvalues of the stiffness

matix xd

Fd

.

Then .0321 In particular, not all eigenvalues are negative

(i.e. there is no stable equilibrium). Proof: (the sum of the principle stiffnesses is a scalar multiple of the field divergence)

.0

321

Eq

dz

dF

dy

dF

dx

dF

xd

FdTr

zyx

Design Corollary: We can’t use all permanent magnet levitation...


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HG3 concept

But we can eliminate all but one active axis...


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JA Holmes

Final Design


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Section View and Final Device


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Jarvik-7, Novacor LVAD, HG3b


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HG3b Animal Trial (July ‘98)first fully maglev pump sufficiently compact and energy

efficient for implantation


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34 Day Animal Trial(August 24, 1999)


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Design Approach: Computer Modeling and Optimization


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TOPOLOGY SELECTION

FINITE ELEMENT

MODEL

LUMPED PARAMETER

MODELS

RAPID PROTOTYPE

IMPLANTABLE PROTOTYPE

OPTIMIZATION

OPTIMIZATION

Design Procedure


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Topology Selection (via design grammar)

(FH,AO) Sp - PRB-DCBM-ATB-PRB-Sp

|| ||

sb - ib - sb


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Lumped-Element Modeling and Finite-Element Analysis

Motor & Thrust Actuator– Lumped reluctance analysis

w/FEA-derived Correction Factors

– Some FEA optimization PM Bearings

– closed form solution of maxwell’s equations

– FEAanalysis Rotor

– rigid body model

– linear fluid damping

Controller, Actuator, Sensor– finite-dimensional models

Pump– Meanline Analysis

– Empirical Formulae

– Computational fluid dynamics (CFD)


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PM Bearing Design


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T a k e g a p < < R a n d i g n o r e e n d - e f f e c t s - > u s e 2 D m o d e l .

./2cos, znMMn

nODz

/2cos, zmMMm

mIDz

T h e s c a l a r m a g n e t i c p o t e n t i a l a t a p o i n t ( x , y , z ) d u e t o

i n n e r r a c e i s i n t e g r a l o f d i p o l e p o t e n t i a l s

dVr

MzyxU

IDV

ID

3

04

1),,(

r

.

z


34

UHHH Tzyx },,{H .

T h e p o t e n t i a l e n e r g y o f a v o l u m ewdV OD

i n t h e f i e l d o f p l a t e I D i s

O DO D V

ODzIDz

V

ODID dVMHdVE ,,MH

y

wE

warea

forcepressure

),(1

. z


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+ s o m e c a l c u l u s …

nm

nmzneeB gndnr

y

if 0

if /2cos14 0

/22/2

0

2

I n t e g r a t i n g a r o u n d t h e r i n g s w i t h m = n = 1 .

deeeBLR

F xgdr cos14

cos/2/22/2

0

20

./214 1

/22/2

0

20

xIee

LRB gdr

s u m m i n g o v e r t h e v a r i o u s w a v e l e n g t h s y i e l d s t h e f o r c e f o r m u l a .


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PM Bearing Model

)/2(114

2

),,(1

/2/2

12

0

2

xnIeen

B

LR

dgxF gndn

oddn

r


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Motor Design

ROTOR

STATOR


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Motor Parameterization

R5 = 13.31

R3 = 5.936

R4 = 9.58

Ls =14.66W1 = 3.73


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Motor Optimization

2

1

3N = 5000 RPM = 85%P = 4W

V = 16.1

46

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N = 15000 RPMV = 11.0

N = 10000 RPMV = 12.4

= 95%V = 40.2

= 90% V = 20.3

P = 16WV = 20.8

P = 8WV = 18.2


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Motor redesign and re-optimization to reduce radial instability

peakcoil

radial

NIBmm

mmB

r

mBB

,062

260

20

9

2

cos


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Pump Design (CFD)(James Antaki & Greg Burgreen)


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Final impeller design

• 5 impeller blade refinements• 4 internal flow path refinements• 6 aft stator blade refinements• 18 month development effort


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Flow visualization of early design

44XIV Brazilian Automatic Control Conference

8000 RPM

Hydrodynamic performance

Efficiency

PR

ES

SU

RE

mm

-Hg

0.160.150.140.130.120.110.100.090.080.070.060.050.040.030.020.01

FLOW RATE (LPM)


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Control system design

•Linear actuator with optimized force/watt1/2

•Virtual Zero Power (VZP) axial control (1.5W coil power while pumping)

•Ultra low-noise eddy-current sensors

•Sensorless Motor Control


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LPF+VoltageSense Amp

-1

1 MHzOsc.

CurrentDriver

s-a s+b

(-90 deg)

V(x)

L(x)x

C

1/(2(L(x0)C) ½) = 1MHz

-90º 90º

offsetadjust

mixer

Sensor System


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Ka (Ms2 -Kb )-1 Ks

Kp+Kd s

Ki/s

impeller axialdisturbance force

-

PID Controller

Linear Motor~2 N/ root watt

Rotor Mass &Bearing Negative Stiffness

Eddy-CurrentSensor

Pos. Reference= 0

PID Controller Structure(for reference only)

coil current

force displacement

noise~1Å / root Hz

heat


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Ka (Ms2 -Kb )-1 Ks

Kp+Kd s

Ki/s

impeller axialdisturbance force

-

VZP Controller

Linear Motor~2 N/ root watt

Rotor Mass &Bearing Negative Stiffness

Eddy-CurrentSensor

current reference = 0

Virtual Zero Power (VZP) Controller Structure*

coil current

force displacement

noise~1Å / root Hz

lessheat

s(Kp+Kd s)

Ki Kp +(1-Kd Ki)sAnti-windup included

*J. Lyman, “Virtually zero powered magnetic suspension,” US Pat. 3,860,300, 1975.


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Axial Disturbance Force

4 Newtons


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19 August 1999Streamliner HG3C sn001pre-implant

What is next?


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Commercialization

Teamed with MedQuest Products Inc, Salt Lake City, Utah.– commercially competitive engineering, clinical, and

business team.– a large maglev patent portfolio and has acquired

the Streamliner patents

Moved to a centrifugal pump design to maximize efficiency


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Conclusions Control engineers have much to offer

– System optimization is at the center of the design process

– The language of mathematics, objectives and constraints is essential

– Clever control design makes low-power maglev possible (Lyman Patent 1975)

Physiologic control is next...– Responsive to condition of heart and body


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Streamliner Team

Mechatronics– Brad Paden, Control

engineering– Chung-Ming Li, Analog

Design– Tom Dragnes, Electrical– Dave Paden,

Mechanical– Randy Crowsen,

Mechanical– Lina Arbelia, bio-

coatings– Nelson Groom, mag-lev

Fluids/Biological– James Antaki,

Streamliner Director– Greg Burgreen, CFD– Jon Wu, exp. fluids– Marina Kameneva,

blood damage– Phil Litwak,

veterinary surgery– Bartley Griffith,

surgery

Funding– McGowan Foundation


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MedQuest Products Team Mechatronics

– Brad Paden, & Garrick McNey,control engineering

– Jed Ludlow, dynamics

– Chung-Ming Li, electronics

– Dirk Cooley, electronics

– Dave Paden, Mechanical

– Randy Crowsen, Mechanical

Fluids/Biological– James Antaki, LVAD

design– Jon Wu, exp. fluids– Gordon Jacobs,

experimental– Jim Long, surgery– Don Olsen,

veterinary surgery

Business– Pratap

Khanwilkar, CEO

– Tim Walker, Marketing

Funding– NIH– Venture Capital


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The End

XIV Brazilian Automatic Control Conference 1 The Streamliner Artificial Heart Brad Paden University...

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