1. LVAD System Review

2. System Overview
Smiha Sayal

3. System Overview Left Ventricular Assist Device (LVAD)
Mechanical device that helps pump blood from the heart to the rest of the body.
Implanted in patients with heart diseases or poor heart function.

4. System Goal
Miniaturize the existing LVAD system to achieve portability while retaining its safety and reliability.

5. Original System “Black box” architecture used during development
Large, not portable
Runs on AC power

6. P10021’s System Has both internal / external components
Equivalent to our “Option 2”
Unfinished implementation

7. Customer Needs Safe Robust Affordable Easy to wear and use
Interactive with user
Controllable by skilled technician
Comparable performance
Compatible with existing pump

8. Other LVAD Technologies
CorAide (NASA)

9. Other LVAD Technologies

10. All electronics external
Concepts: Option 1
All electronics external

11. Concepts: Option 2
ADC internal only

12. Pump and motor control internal
Concepts: Option 3
Pump and motor control internal

13. All electronics and battery internal
Concepts: Option 4
All electronics and battery internal

14. All electronics and battery internal
Concepts: Option 5
All electronics and battery internal

15. Concept Generation

16. Concept Generation Highlights
Option 1
Smallest internal volume
Feasible within timeline
Easiest to maintain
Minimum 20 wires
Option 2
Relatively small internal volume
Slightly higher risk of internal failure
Minimum 10 wires
Option 3
Large internal volume
Difficult to design
Electronics failure is fatal
Minimum 3 wires
Option 4
Best Option
350
273
200
153
Option 5
Relatively small internal volume
Slightly higher risk of internal
failure
Minimum
249

17. Enclosure Design
Nicole Varble and Jason Walzer

18. External Enclosure Needs Risks
The external package should be lightweight/ robust/ water resistant
The devices should be competitive with current devices
The device should fit into a small pouch and be comfortable for user and be comfortable for the user
The external package should resist minor splashing
The device should survive a fall from the hip
Risks
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

19. Concept Generation- Materials/Manufacturing Process
Concept Generation- Material and Manufacturing Processes
Manufacturing Processes
Rapid Prototyping (ABS Plastic)
Stereolithography
Injection Molded
Machine Metal or Polymer
Selection Criteria
Weight
Rating
Notes
Score
Cost 9 4 36 1
$30k for mold 2 18
Feasibility within timeline 10 5 50
long lead time 40 3 30
Strength 6
37 MPa 24
58 MPa
35-70 MPa
~580 MPa
Material Interaction with water 8
resin based 16 20
Ease of Manufacturing 15
20 wires
10 wires
3 wires
Net Score
133
110 78
103
Rank
Continue?
 yes No no
weight
1- low importance
10- high importance
rating
1- does not meet cirteria
5- meets cirteria

20. Rapid Prototyping Capable of building thin geometries Machinable
Material can be drilled and tapped (carefully)
Accepts CAD drawings
Complex geometries can be created easily
Ideal for proposed ergonomic shape
Builds with support layer
Models can be built with working/moving hinges without having to worry about pins
Capable of building thin geometries
ABSplus
Industrial thermoplastic
Lightweight - Specific gravity of 1.04
Porous
Does not address water resistant need

21. ABS Plastic Mechanical Property Test Method Imperial Metric
Tensile Strength
ASTM D638
5,300 psi
37 MPa
Tensile Modulus
330,000 psi
2,320 MPa
Tensile Elongation 3%
Heat Deflection
ASTM D648
204°F
96°C
Glass Transition
DMA (SSYS)
226°F
108°C
Specific Gravity
ASTM D792
1.04
Coefficient of Thermal Expansion
ASTM E831
4.90E-5 in/in/F
Important Notes
Relatively high tensile strength
Glass Transition well above body temperature
Specific Gravity indicates lightweight material

22. Feasibility- Water Ingress Test
Need: The external package should resist minor splashing
Specification: Water Ingress Tests
Once model is constructed, (user interface, connectors sealed, lid in place) exclude internal electronics and perform test
Monitor flow rate (length of time and volume) of water
Asses the quality to which water is prevented from entering case by examining water soluble paper
Risk: Water can enter the external package and harm the electronics
Preventative measures:
Spray on Rubber Coating or adhesive
O-rings around each screw well and around the lid
Loctite at connectors
Preliminary Tests without protective coating show no traceable water ingress
Loctite
Spray on Rubberized Coating

23. Feasibility- Robustness Testing
Need: The device should survive a fall from the hip
Specification: Drop Test
Drop external housing 3 times from 1.5 m, device should remain fully intact
Specify and build internal electrical components
Identify the “most vulnerable” electrical component(s) which may be susceptible to breaking upon a drop
Mimic those components using comparable (but inexpensive and replaceable) electrical components, solder on point to point soldering board
Goal
Show the housing will not fail
Show electronics package will not fail, when subjected to multiple drop tests
Risks
The housing fails before the electronic components in drop tests (proved unlikely with prototype enclosure)
The electronic components can not survive multiple drop tests
Preventative Measures
Eliminate snap hinges from housing (tested and failed)
Test the housing first
Design a compact electronics package

24. Feasibility- Heat Dissipation of Internal Components
130°C is absolute maximum for chip junction temperature in order to function properly
Goal- comfort for the user
Assumed steady state, heat only dissipated through 3 external surfaces
Maximum heat dissipation ~25W
Actual heat dissipation ~5W
t, k Q
Tin
Tout h

25. Prototype Enclosure Survived drop test Water resistant
Plastic is machinable
Drilled, tapped, milled
Helicoils should be used to tap holes
Constant opening and screwing and unscrewing of lid will result in stripped threads
Approximate wall thickness (6mm)
Distance between center of holes and wall needs to be increased
Some cracking occued
Latches are not feasible

26. User Interface + - From Pump To Battery BATTERY MENU To Battery OK
Speed
Battery Life
Fault Indication
BATTERY OK
ERROR
MENU
From Pump
To Battery
To Battery
To/From Computer
Components:
Indication of battery life (3x LED)
Indication of Fault (LED and Buzzer)
Indication of levitation (LED)
Display
Increase/Decrease Speed (2x Button)
Menu (Button)
Connectors:
26- pin LEMO connector
USB connector
Battery Terminals (x2)
OK: Indication of levitation
ERROR: No Levitation, connection errors

27. User Interface- Components
LED Backlit display with waterproof bezel and o-ring
G/R/Y LEDs with O-ring and waterproof bezel
Waterproof buttons with O-ring

28. User Interface- Connectors
Current Model: Part # EGG 2K 326 CLL
Proposed: Part # EEG 2K 326 CLV
Pin Layout

29. User Interface- IP Codes
Ingress Protection
First Number
Protection against Solid Objects
- No protection (Sometimes X) 1
- Protected against solid objects up to 50mm³ 2
- Protected against solid objects up to 12mm³ 3
- Protected against solid objects up to 2.5mm³ 4
- Protected against solid objects up to 1mm³ 5
- Protected against dust, limited ingress (no harmful deposit) 6
- Totally protected against dust
Second Number
Protection against liquids
- Protection against vertically falling drops of water (e.g. condensation)
- Protection against direct sprays of water up to 15 degrees from vertical
- Protection against direct sprays of water up to 60 degrees from vertical
- Protection against water sprayed from all directions - limited ingress permitted
- Protected against low pressure jets of water from all directions - limited ingress permitted
- Protected against low pressure jets of water, limited ingress permitted (e.g. ship deck) 7
- Protected against the effect of immersion between 15cm and 1m 8
- Protected against long periods of immersion under pressure
Display
IP 67
Buttons
LEDs
USB
IP 68
Connector

30. Enclosure Design

31. Enclosure Design

32. Enclosure Design

33. Embedded Control System
Andrew Hoag and Zack Shivers

34. Control System Requirements Customer Needs
Selecting suitable embedded control system
Designing port of control logic to embedded system architecture
Customer Needs
Device is compatible with current LVAD
Device is portable/small
Allows debug access

35. Impeller Levitation 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

36. Levitation Algorithm
Algorithm complexity influences microcontroller choice
Electronics choices affect volume / weight
Proportional – Integral – Derivative (PID)
Very common, low complexity control scheme

37. Embedded System Selection
Requirements:
Can handle PID calculations
Has at least 8x 12-bit ADC for sensors at 2000 samples/sec
Multiple PWM outputs to motor controller(s)
Same control logic as current LVAD system
Reprogrammable

38. Embedded System Selection
Custom Embedded
dsPIC Microcontroller
Blocks for Simulink
Small
Inexpensive (<$10 a piece)
TI MSP430
Inexpensive (<$8 a piece)
Small, low power
COTS Embedded
National Instruments Embedded
Uses LabVIEW
Manufacturer of current test and data acquisition system in “Big Black Box”
Large to very large
Very expensive (>$2000)

39. Control Logic/Software
Closed-loop feedback control using PID – currently modeled in Simulink for use with the in “Big Black Box”
Additional microcontroller-specific software will be required to configure and use A/D, interrupts, timers.

40. Life Critical System Not at subsystem level detail yet.
Life-critical operations would run on main microcontroller.
User-interface operations run on separate microcontroller.
Possible LRU (Least Replaceable Unit) scheme

41. Separation of Main/UI Microcontroller Concept Selection

42. Technician/Field Software Debug Interface
USB
USB is everywhere.
Requires custom PC-side software.
Requires processor support.
Serial (RS-232)
Many computers don’t have serial ports anymore.
Can use $15 COTS USB to Serial adapter.
Can use COTS terminal tools.

43. Technician/Field Software Debug Interface
Example of using COTS tool – Windows HyperTerminal (free/part of Windows)

44. Technician/Field Software Debug Interface Concept Selection

45. Microcontroller Search Parameters
A/D
0-5V
(kilo-samples/sec)
This equates to 40ksps minimum for A/D
PWM
General I/O for UI controls
At least 10x digital
At least 5x analog
UART (for Serial connection)

46. Microcontroller Packaging
L/TQFP – Low-profile/Thin Quad Flat Pack
Small surface-mount (PCB mount) chip package.
Is solderable (by skilled solderer)
Body thickness up to 1.0mm, sizes range from 5x5mm to 20x20mm

47. Microcontroller 2 families of Microcontrollers dsPIC from Microchip
MSP430 from Texas Instruments

48. Microchip dsPIC dsPIC30F5011 (16-bit architecture)
Max CPU speed 30 MIPS (Million Instructions/sec)
V operating voltage
66KB Flash, 4KB RAM, 1KB EEPROM
16x12-bit 200ksps
-40 to 85C operating temp
64-lead TQFP – body 10x10mm, overall 12x12mm
Cost [1-25 units] = $7.21

49. TI MSP430 MSP430F5435A (16-bit architecture)
Max CPU speed 25 MIPS (Million Instructions/sec)
V operating voltage
192KB Flash, 16KB RAM
16x12-bit 200ksps
3 Timer modules (with total of 15 timer channels)
-40 to 85C operating temp
80-lead LQFP – body 10x10mm, overall 12x12mm

50. Microcontroller Concept Selection

51. Active Magnetic Bearings System Ampliers
Juan Jackson

52. AMB Control Center The control center is a closed loop system
Stabilization of system is achieved by the feedback control
Power Amplifiers convert the input PWM signals to satisfy system requirements
Four Degrees of freedom, FrontX, FrontY, RearX, RearY, which pushes rotor
DAC
Microcontroller
PWM Control Signal
4 H-Bridge or 2 Full Bridge Power Amplifiers
Active Magnetic Bearing System
Impeller
FrontX
FrontY
RearX
RearY
Hall Effect Sensors
(Senses Position)

53. Amplifier Selection 2 types to select from Linear PWM Output input
Higher power to load
PWM
The generated current switches between output high and low
Capable of higher power than the linear amplifier
Better performance at higher frequencies

54. Amplifier Selection Linear Amplifier PWM Amplifier Selection Criteria
Linear Amplifier
PWM Amplifier
Selection Criteria
Weight
Rating
Notes
Score
Cost 5 3 15 25
Feasibility within timeline 10 50
Fits Customer Requests 2 20
Ease of Design 6 4 24
Net Score
109
149
1-Low importance
10-High importance
1-Does not meet criteria
5-Meets criteria

55. AMB Amplifier Selection
11021
AMB Amplifier Selection
LMD1800
TLE6209R
DRV8412
Selection Criteria
Weight
Specification
Notes
Rating
Score
Continuous Current Output (A) 10 3
Operation with current system verified 5 50 6
Switching Frequency (kHz)
100
2000
500
Rdson (mΩ)
330 2 20
150 80
Operating Supply Voltage (V)
12 to 55
up to 45
Temperature (°C)
-40°C ~ 125°C
-40°C ~ 150°C
-40°C ~ 85°C
Package Type 8
Through hole 16
Surface mount 40
Net Score
236
290
Rank 1
Designer Choice
3RD
2ND
1st
Customer Choice 55

56. Amplifier Selection Proof of concept
Texas Instrument Application Diagram for Full Bridge Mode Operation

57. Amplifier Selection Proof of concept
Motor Control - DC Brushless
BLDC motors are more efficient, run faster and quieter, and require electronics to control the rotating field. BLDC motors are also cheaper to manufacture and easy to maintain
Recommended:MSP430F Also consider: Stellaris 5000 /8000 Series C2000 - Fixed Point / Piccolo, Delfino MSP430 - F2xx /5xx 25MHz
ADS7953 - 1ch, 12 bit ADC
BQ2000T - Battery Charge Management
SN65HVD233  - 3.3V CAN Transceiver
TPS40305 - DC/DC Controllers
DRV8412 - PWM Power Driver
TPS54620 - Step- Down Regulators
Texas Instruments Microcontroller for Motor Control Applications : Component recommendation
"MCU4Analog." Texas Instruments. Texas Instruments, n.d. Web. 4 Nov <

58. Amplifier Selection Proof of concept
Testing
Hardware

59. Questions / Comments
Help us improve our design!