Transcript Display

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Left Ventricular
Assist Device (LVAD)
 Mechanical device that
helps pump blood from
the heart to the rest of
the body.
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Implanted in patients
with heart diseases or
poor heart function.
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“Black box” architecture used during
development
Large, not portable
Runs on AC power
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Miniaturize the existing LVAD system to
achieve portability while retaining its safety
and reliability.
Control system all external
Nicole Varble and Jason Walzer
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Needs
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Lightweight
Robust
Competitive with current devices
Easily portable and comfortable for user
Resist splashing
Survive a fall from the hip
Risks
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Housing for the electronics is too heavy/large/uncomfortable
Water can enter the external package and harm the electronics
The housing fails before the electronic components in drop tests
The electronic components can not survive multiple drop tests
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Dimensions: 180 x 82 x 103 mm
 Volume ~ 1,500 cm3
 Current Controller ~ 12,700 cm3
 Heart Mate II ~ 820 cm3
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Percentage Reduction:
 88 %
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Weight:
 ~560 g
 Heart Mate II ~ 602 g
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Other features:
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Helicoils to reinforce threads in ABS plastic
Plasti- dip coating
Ergonomic curve against body
Belt-loop for portability
Custom made 0-ring
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Drop Test:
 Enclosure dropped 1.5 m above ground level and was
tested for damage
 Results: No visible cracks or fissures were observed.
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Water Ingress Test:
 Enclosure was sprayed on with a rubberized coating
and was held under a faucet with a flow rate of about 2
gpm for about 1 min
 Results: Not submersible but can endure running water
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Heat Dissipation:
 Max temperature inside the box was analytically
calculated to be 79°C
 Under the max critical operating temperature of
electronics
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Drop Test:
 Use enclosure with similar components to current
prototype
 High risk of permanent damage
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Heat Analysis:
 Many broad assumptions (often over compensating)
 Temperature calculated was close to the critical
working temperature of electronics (~85°C )
 In-depth experimental analysis could have been
conducted
Zack Shivers and Juan Jackson
0V
3.3V 0V
1.6V
2.58V
Before Scaling
29% ADC
Range
3.0V
0.01V
2.94V
After Scaling
98% of ADC
Range
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Hall effect sensors are
natively 5V
 Divide to 3.3V levels
 Use 3.0V ref for ADC
 RC anti-aliasing filter
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Effective transformation
 Voltage divider
 Buffer
 Subtract 1.6V and gain
up by factor of 3
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3-phase motor controller
 Used to control impeller
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Off-the-shelf component
 Suggested to us by the customer as tested and
reliable controller
 Simplified our design
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Interface
 Standard RC PWM signal, low resolution
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Impeller must be levitating or “floating”
Electromagnets control force exerted on impeller
Keeps impeller stabilized in the center
Position error measured by Hall Effect sensors
LMD18200
P10021’s
System:
8280 mm3
DRV8412
Our
System:
282 mm3
Only 3.40%
of previous
prototype!
15V
3.3V
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5.0V
12V
5.0V Ref
3.0V Ref
1.60V Ref
Need to overall system at 15V
3.3V and 5V needed at relatively high power
 Generated with high-efficiency switching power
supplies
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15V used directly for AMB system
Various references for HESA and DAC
~85% efficient
for loads > 0.35A
UI
uC
HESA
AMB
Power
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Passes all hardware tests
 Microcontroller
 3.3V, 5V, and 12V power supplies
 H-bridges
 HESA signal conditioning
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No cut/reworked traces
Andrew Hoag
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Texas Instruments MSP430 Microcontroller
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Specifications
 Max Frequency: 25MHz
 Operating voltage:
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1.8V – 3.3V
Package: 100 pin LQFP
Flash Memory: 256 KB
RAM: 16 KB
87 General I/O pins
ADC: 12-bit SAR
 4x USCI_A
(UART/LIN/IrDA/SPI)
 4x USCI_B (I2C/SPI)
 Timers
 1x 16-bit (5CCR)
 1x 16-bit (3CCR)
 1x 16-bit (7CCR)
 Watchdog
 RTC
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MSP430
 Operating at 20MHz
 Using less than 16kB memory
 HESA values sampled 5000 times per second
using Analog-to-Digital converter
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Software
 Controller software
written in C using
Texas Instruments
Code Composer
Studio.
 Technician/debug
client software written
in Java.
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Pulse-Width Modulation is a digital signal
that is used to simulate an analog output by
varying high and low signals at intervals
proportional to the value.
The AMBs PWM signals are generated using
four 20kHz PWM signals generated by Timer
A0.
The 3-phase motor PWM signal is generated
using a 50Hz PWM signal generated by Timer
B.
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PID: common feedback control loop that is
currently used in the LVAD control system.
 The output signal is a function of the error, the
error’s history, and the error’s rate of change.
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Debug information is transmitted to a PC at
115200 baud using serial RS-232 over USB.
Centering test results:
Graphic
LCD
Buttons
LEDs
Buzzer
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Why use an LCD?
 Display much more information
 Interactivity
 Allows interface modes for technician and user
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Buttons
 Up, Down, and Menu for interaction
 IP67-rated
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LEDs
 Provide basic, robust indicators
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Buzzer
 Loud, high importance warnings
 Audible button feedback (beep when pressed)
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System needs to work
Safe
Robust
Affordable
Easy to wear and use
Interactive with user
Controllable by skilled technician
Comparable performance
Compatible with existing pump
Engr. Spec.
#
Source
Unit of
Measure
Marginal
Value
Ideal Value
Actual
Comments/Status
ES101-1
CN101
Weight of device
lbs
6
4
1.22
Met
ES101-2
CN101
Volume of device
cu in
75
56
91.5
Not Met
ES102-1
CN103
Device running time (full charge-needing recharge)
hours
6
12
Not Met
ES103-1
CN103
Device recharge time
hours
<2
1
Not Met
ES105-1
CN105
AC mains power
binary
0
1
ES203-1
CN203
Device running time between swapping batteries
hours
0.25
>0.5
ES302-1
CN302
Battery information is indicated
binary
0
1
1
Met
ES303-1
CN303
User control of pump rotation speed
binary
1
1
1
Met
ES401-1
CN401
Hardware signal debug port
binary
0
1
1
Met
ES402-1
CN402
Device is reprogrammable
binary
1
1
1
Met
ES403-1
CN403
Manual speed control
binary
1
1
1
Met
ES500-1
CN500
Device price
dollars
<4000
2000
1400
Met
ES601-1
CN601
Device lifetime expectancy
years
0.5
20
Not Met
ES701-1
CN701
Battery life vs. competitor life
%
-50
100
Not Met
ES702-1
CN702
Device weight vs. competitor weight
lbs
1.33
> 1.33
1.22
Met
ES-802-1
CN802
Device heat dissipation
mW/cm^2
40
<40
11.4
Met
Specification (description)
1
Met
Not Met
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Initial Plan: Final Assembly by Week 7 followed
by testing.
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Actual Plan: The plan was delayed by 2 weeks.
Assembly was done in week 9 followed by
testing in week 10.
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Current Status: Continuing Testing. System
Demo to be done by mid Week 11.
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Initial Budget: The design was estimated to
cost $ 1,000.
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Current Status: Currently ~$1,400 has been
spent.