System Reliability Analysis

MEDICAL SYSTEM:

H&E Staining Instrument (Class II)

WORK SCOPE:

Conduct a comprehensive system reliability and failure analysis on the instrument, and propose an Error Handling architecture that effectively mitigates the hazardous situations and improves the overall instrument service performance.

BACKGROUND:

The company is a world leader in the markets of H&E Staining and in vitro diagnostics; they were struggling to successfully complete the development of their next generation H&E platform, underwent significant leadership and engineering turnover, and had numerous hardware / software integration challenges due to inadequate design specifications, inefficient multi-discipline team collaboration, and a weakly structured development process. The software engineering team was more than 9 months behind schedule, and had "higher priorities than error handling". To add to that, the cumulative number of errors across the system exceeded 2000 unique fault codes, each error with varying degrees of failure and system effects.

RESULTS:

Defined a software architecture based on a rule engine structure that integrates error handling in an event driven environment with an easy to maintain decision table in Excel format. The system error handler is centralized, receiving fault codes from various instrument subsystems, and maintaining a knowledge base with the instrument operational state history. Rule based actions are performed based on the decision table specifications and the instrument knowledge base (e.g. how many times an error occurred in the last 10 cycles or hour, rate of occurrence, combination of errors, etc.).

The rule engine framework also allows for a hierarchical error handling implementation that leverages common error handling for similar failure modes, such as:

  • Mechanical door/motion control failure
  • Heater control runaway
  • Excessive motor torque
  • Control parameter out-of-range (upper/lower specs)

Further the system provides finer error handling control for complex sequences of events that involve multiple modules, or temporal characteristics, such as:

  • Scheduling process hand-off from one module to another
  • Limiting available processing based on consumable levels, module failures, door states, etc. (degraded modes)
  • Dispatching preventive maintenance on early signs of failures

A flexible architecture that is capable of addressing a wide range and volume of fault handling scenarios to effectively manage instrument reliability concerns.

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