P11021 System Review Miniaturization of RIT’s LVAD Electronics Package

1. P11021 System ReviewMiniaturization of RIT’s LVAD Electronics Package

2. 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.

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

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

5. Concepts Control system all external

6. Enclosure Design Nicole Varble and Jason Walzer

7. External Enclosure • Needs • Lightweight • Robust • Competitive with current devices • Easily portable and comfortable for user • Resist splashing • 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

8. Enclosure Features • Dimensions: 180 x 82 x 103 mm • Volume ~ 1,500 cm3 • Current Controller ~ 12,700 cm3 • Heart Mate II ~ 820 cm3 • Percentage Reduction: • 88 % • Weight: • ~560 g • Heart Mate II ~ 602 g • Other features: • Helicoils to reinforce threads in ABS plastic • Plasti- dip coating • Ergonomic curve against body • Belt-loop for portability • Custom made 0-ring

9. Enclosure Testing • Drop Test: • Enclosure dropped 1.5 m above ground level and was tested for damage • Results: No visible cracks or fissures were observed. • 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 • Heat Dissipation: • Max temperature inside the box was analytically calculated to be 79°C • Under the max critical operating temperature of electronics

10. Short comings / Recommendations • Drop Test: • Use enclosure with similar components to current prototype • High risk of permanent damage • 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

11. Electronics Design Zack Shivers and Juan Jackson

12. Electronics Overview

13. HESA Signal Conditioning 0V 3.3V 0V 3.0V 1.6V 2.58V 0.01V 2.94V

14. HESA Signal Conditioning • Hall effect sensors are natively 5V • Divide to 3.3V levels • Use 3.0V ref for ADC • RC anti-aliasing filter • Effective transformation • Voltage divider • Buffer • Subtract 1.6V and gain up by factor of 3

15. Impeller Speed Controller • 3-phase motor controller • Used to control impeller • Off-the-shelf component • Suggested to us by the customer as tested and reliable controller • Simplified our design • Interface • Standard RC PWM signal, low resolution

16. Active Magnetic Bearing • 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

17. Active Magnetic Bearings LMD18200 DRV8412 Only 3.40% of previous prototype!

18. On-Board Power Supplies • Need to overall system at 15V • 3.3V and 5V needed at relatively high power • Generated with high-efficiency switching power supplies • 15V used directly for AMB system • Various references for HESA and DAC

19. On-Board Power Supplies ~85% efficient for loads > 0.35A

20. Printed Circuit Board

21. Printed Circuit Board

22. Printed Circuit Board

23. Printed Circuit Board UI uC Power HESA AMB

24. PCB Results • Passes all hardware tests • Microcontroller • 3.3V, 5V, and 12V power supplies • H-bridges • HESA signal conditioning • No cut/reworked traces

25. Embedded Control System Andrew Hoag

26. MSP430F5438A • Texas Instruments MSP430 Microcontroller

27. MSP430F5438A Specifications • 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  • Specifications • Max Frequency: 25MHz • Operating voltage: 1.8V – 3.3V • Package: 100 pin LQFP • Flash Memory: 256 KB • RAM: 16 KB • 87 General I/O pins • ADC: 12-bit SAR

28. Our Configuration • MSP430 • Operating at 20MHz • Using less than 16kB memory • HESA values sampled 5000 times per second using Analog-to-Digital converter

29. Software • Software • Controller software written in C using Texas Instruments Code Composer Studio. • Technician/debug client software written in Java.

30. PWM Output • 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.

31. Motor PWM Test Results

32. Control Law • 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.

33. Debug Data • Debug information is transmitted to a PC at 115200 baud using serial RS-232 over USB. • Centering test results:

34. User Interface Elements

35. User Interface Elements

36. User Interface • Why use an LCD? • Display much more information • Interactivity • Allows interface modes for technician and user • Buttons • Up, Down, and Menu for interaction • IP67-rated • LEDs • Provide basic, robust indicators • Buzzer • Loud, high importance warnings • Audible button feedback (beep when pressed)

37. System Analysis

38. Customer Needs • 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

39. Customer Specifications

40. Schedule • Initial Plan: Final Assembly by Week 7 followed by testing. • Actual Plan: The plan was delayed by 2 weeks. Assembly was done in week 9 followed by testing in week 10. • Current Status: Continuing Testing. System Demo to be done by mid Week 11.

41. Budget • Initial Budget: The design was estimated to cost $ 1,000. • Current Status: Currently ~$1,400 has been spent.

42. Questions / Comments