Reliability-based health monitoring redline voting logic design

Redline limit protection is a very important safety and reliability design feature for “cannot fail” systems such as liquid rocket engines and launch vehicles. Traditionally, the redline system design is ad-hoc without formal and systematic reliability consideration. This paper presents a reliability-based redline voting logic design methodology to enhance the redline effectiveness. The paper introduces two reliability measures, false positive probability and false negative probability, and applies them to guide voting logic design assessment and alternative option selections. Several design options are proposed and evaluated, including “All” logic, “Majority” logic, and “Average” logic. Illustrative examples are shown, and some general comparison conclusions of these design options are presented. With the reliability consideration and sound health monitoring redline system designs and implementations, it is believed that more potential for higher reliability, safer, and lower cost of any “cannot fail” systems can be realized.