P 11021 System Review Miniaturization of RITs LVAD
- Slides: 42
P 11021 System Review Miniaturization of RIT’s LVAD Electronics Package
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.
Original System “Black box” architecture used during development Large, not portable Runs on AC power
System Goal Miniaturize the existing LVAD system to achieve portability while retaining its safety and reliability.
Concepts Control system all external
Enclosure Design Nicole Varble and Jason Walzer
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
Enclosure Features � Dimensions: 180 x 82 x 103 mm Volume ~ 1, 500 cm 3 Current Controller ~ 12, 700 cm 3 Heart Mate II ~ 820 cm 3 � 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
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
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
Electronics Design Zack Shivers and Juan Jackson
Electronics Overview
HESA Signal Conditioning 0 V 3. 3 V 0 V 1. 6 V 2. 58 V Before Scaling 29% ADC Range 3. 0 V 0. 01 V 2. 94 V After Scaling 98% of ADC Range
HESA Signal Conditioning �Hall effect sensors are natively 5 V �Divide to 3. 3 V levels �Use 3. 0 V ref for ADC �RC anti-aliasing filter �Effective transformation �Voltage divider �Buffer �Subtract 1. 6 V and gain up by factor of 3
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
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
Active Magnetic Bearings LMD 18200 P 10021’s System: 8280 mm 3 DRV 8412 Our System: 282 mm 3 Only 3. 40% of previous prototype!
On-Board Power Supplies 15 V 3. 3 V 5. 0 V 12 V 5. 0 V Ref 3. 0 V Ref 1. 60 V Ref �Need to overall system at 15 V � 3. 3 V and 5 V needed at relatively high power Generated with high-efficiency switching power supplies � 15 V used directly for AMB system �Various references for HESA and DAC
On-Board Power Supplies ~85% efficient for loads > 0. 35 A
Printed Circuit Board
Printed Circuit Board
Printed Circuit Board
Printed Circuit Board UI HESA u. C AMB Power
PCB Results Passes all hardware tests Microcontroller 3. 3 V, 5 V, and 12 V power supplies H-bridges HESA signal conditioning No cut/reworked traces
Embedded Control System Andrew Hoag
MSP 430 F 5438 A Texas Instruments MSP 430 Microcontroller
MSP 430 F 5438 A Specifications �Specifications Max Frequency: 25 MHz Operating voltage: 1. 8 V – 3. 3 V Package: 100 pin LQFP Flash Memory: 256 KB RAM: 16 KB 87 General I/O pins ADC: 12 -bit SAR 4 x USCI_A (UART/LIN/Ir. DA/SPI) 4 x USCI_B (I 2 C/SPI) Timers 1 x 16 -bit (5 CCR) 1 x 16 -bit (3 CCR) 1 x 16 -bit (7 CCR) Watchdog RTC
Our Configuration MSP 430 Operating at 20 MHz Using less than 16 k. B memory HESA values sampled 5000 times per second using Analog-to-Digital converter
Software Controller software written in C using Texas Instruments Code Composer Studio. Technician/debug client software written in Java.
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 20 k. Hz PWM signals generated by Timer A 0. �The 3 -phase motor PWM signal is generated using a 50 Hz PWM signal generated by Timer B.
Motor PWM Test Results
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.
Debug Data Debug information is transmitted to a PC at 115200 baud using serial RS-232 over USB. Centering test results:
User Interface Elements Graphic LCD Buttons LEDs Buzzer
User Interface Elements
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 IP 67 -rated � LEDs Provide basic, robust indicators � Buzzer Loud, high importance warnings Audible button feedback (beep when pressed)
System Analysis
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
Customer Specifications Engr. Spec. # Source ES 101 -1 CN 101 Weight of device lbs 6 ES 101 -2 CN 101 Volume of device cu in ES 102 -1 CN 103 Device running time (full charge-needing recharge) ES 103 -1 CN 103 ES 105 -1 Specification (description) Unit of Measure Marginal Ideal Value Actual Comments/Status 4 1. 22 Met 75 56 91. 5 Not Met hours 6 12 Not Met Device recharge time hours < 2 1 Not Met CN 105 AC mains power binary 0 1 ES 203 -1 CN 203 Device running time between swapping batteries hours 0. 25 >0. 5 ES 302 -1 CN 302 Battery information is indicated binary 0 1 1 Met ES 303 -1 CN 303 User control of pump rotation speed binary 1 1 1 Met ES 401 -1 CN 401 Hardware signal debug port binary 0 1 1 Met ES 402 -1 CN 402 Device is reprogrammable binary 1 1 1 Met ES 403 -1 CN 403 Manual speed control binary 1 1 1 Met ES 500 -1 CN 500 Device price dollars <4000 2000 1400 Met ES 601 -1 CN 601 Device lifetime expectancy years 0. 5 20 Not Met ES 701 -1 CN 701 Battery life vs. competitor life % -50 100 Not Met ES 702 -1 CN 702 Device weight vs. competitor weight lbs 1. 33 > 1. 33 1. 22 Met ES-802 -1 CN 802 Device heat dissipation m. W/cm^2 40 <40 11. 4 Met 1 Met Not Met
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.
Budget Initial Budget: The design was estimated to cost $ 1, 000. Current Status: Currently ~$1, 400 has been spent.
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