LVAD System Review

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. Concepts: Option 1 All electronics external

11. Concepts: Option 2 ADC internal only

12. Concepts: Option 3 Pump and motor control internal

13. Concepts: Option 4 All electronics and battery internal

14. Concepts: Option 5 All electronics and battery internal

15. Concept Generation

16. Concept Generation Highlights 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 • 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

20. Rapid Prototyping http://www.dimensionprinting.com/ • 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 • Important Notes • Relatively high tensile strength • Glass Transition well above body temperature • Specific Gravity indicates lightweight material

22. Feasibility- Water Ingress Test Loctite Spray on Rubberized Coating • 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

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 Tout Tin h Q t, k 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

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 + Speed Battery Life Fault Indication To Battery To/From Computer ERROR OK - 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

30. Enclosure Design

31. Enclosure Design

32. Enclosure Design

33. Embedded Control System Andrew Hoag and Zack Shivers

34. Control System • Requirements • 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 http://en.wikipedia.org/wiki/PID_controller

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 • 8x12-bit @5ksps (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) • 2.5-5.5V operating voltage • 66KB Flash, 4KB RAM, 1KB EEPROM • 16x12-bit ADC @ 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) • 2.2-3.6V operating voltage • 192KB Flash, 16KB RAM • 16x12-bit ADC @ 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