Design of a novel and comprehensive methodology for failure and reliability analysis of artificial heart pumps.

摘要

Artificial heart pumps (AHPs) in the form of ventricular assist devices (VADs) are today's most promising, long-term (5-10 years) treatments for patients suffering from intractable congestive heart failure. There are no standardized protocols for long-term reliability testing and only limited recommendations to achieve approval for clinical use. The objective of this dissertation was to develop and apply a comprehensive, thorough failure and reliability analysis applicable to many types of AHPs.; All components and subsystems of three VADs (pulsatile, mechanical bearings, and magnetically levitated) were assessed for their reliability and potential to fail. This research also focused on the motor, after a failure modes and effects analysis (FMEA) was conducted. An extensive evaluation of fault tolerance was completed in a brushless direct current (BLDC) motor, typical for an AHP application. This BLDC motor was experimentally tested under normal and faulted conditions (including short and open circuit insulation faults). Under faulted conditions, the motor speed was reduced by 6%, while current requirements increased by 50%, and the temperature of the motor increased by 300% of normal. An experimental and computational comparison found a 5% deviation between the experimental and computational current, and a 2.8% difference in the speed under similar faulted conditions (short circuited turns). Experimental results support the need for significant evaluation of fault tolerance to prevent increased temperatures of the motor. Weibull, normal, and exponential failure distributions were used to analyze failure data that were obtained from experimental testing and extensive literature research. Application to reliability block diagrams resulted in 80% theoretical reliability measures of: 0.66 years, 1.39 years, and 5.03 years for the pulsatile VAD, VAD with mechanical bearings, and the magnetically levitated VAD. These results provide encouraging support for the use of reliability block diagram analysis to predict reliability.; As medical devices evolve into the consumer market, this research is provides industry with a thorough methodology and implementation for failure and reliability studies not only for VADs but can be expanded for other medical devices. Ultimately, the application of this research during the design and development stage of medical devices will ensure safety and efficacy for patient use.